Introducing performance precision tubes, precision tubes often said that it is not easy to rust, and say this is because of the precision tubes containing chromium ingredient, in the air, it combines with oxygen to form a solid surface and dense film is not oxidized state, this film is not oxidized steel surface to prevent oxidation (rust), and may play a role in protecting the surface to prevent corrosion of various corrosion factors. However, if this layer of protective film destroyed, its corrosion occurs, let's look at what causes for the oxide film is destroyed and its corresponding approach.
The main reason for the destruction of the oxide film from its floating iron or harmful atmospheric gas composition affected, because adhesion, accumulation, and sea salt contained in the adhesion caused. These attachments will gradually gather, plus moisture and fixed, so that will destroy the surface of the stainless steel pipe materials are not oxidized film and hinder regeneration of this film, which began rusting stainless steel pipe materials. Rust caused by this situation, mainly precision tube surface rust inside and no rust, so the direct use of artificial means to get rid of surface rust can, once the rust removal, precision tubes can still restore the original shiny, re-use.
For precision tubes are often not in use, before use, when found rusted, they need to be cleaned, in peacetime, we should pay attention to the maintenance of precision tubes, precision tubes not only to avoid corrosion, but also to save a lot of waste of human and financial resources for our business, after all, under the rusty precision tubes if the number of its relatively large number of cases, cleaning up is also a troublesome thing.
Wednesday, November 27, 2013
Steel pipe weld internal defect repair
No internal defects steel weld penetration refers to a defect between the workpiece and the weld metal or weld layer partially unfused. Incomplete penetration welds weakened section of the work, resulting in severe stress concentration, greatly reduce joint strength, it often becomes the root of the weld cracking. Weld slag sandwiched nonmetallic slag, that is called slag. Slag reduces the weld cross-section of work, causing stress concentration will reduce the weld strength and toughness.
Porosity of the weld metal at high temperatures, excessive absorption of the gas (e.g., H2) or because the bath inside the metallurgical reaction gases (e.g., CO), the bath is cooled and solidified in the time to discharge, and in the inside or the surface of the weld cavities, namely pores. The presence of pores reduces the effective work weld cross section, decreasing the mechanical strength of the joint. If penetrating pores or continuity exists, it will seriously affect the tightness of the weldment. After the welding process, cracks or welding, metal in the welded joint region appears is called a partial fracture cracks. Cracks may occur in the weld may also be generated on both sides of the weld heat affected zone. Sometimes produced in the metal surface, the metal may be generated internally.
Generally in accordance with the mechanism of crack formation can be divided into two types of thermal cracking and cold cracking. Thermal cracking is generated by a liquid to a solid state crystallization process in the weld metal, mostly produced in the weld metal. The main cause of the existence of the low-melting substances (such as FeS, m.p. 1193 ℃) weld which weakens the contact between the grains when subjected to high welding stress, it is easy to cause breakdown between the grains. Weldments and welding rod containing S, Cu impurities such a long time, it is prone to hot cracking. Thermal cracks along the grain boundary characteristic distribution. When the crack through the surface and the outside world, the tendency has obvious hydrogenation. Cold cracks are generated in the cooling process after welding, mostly produced in the base metal or base metal and the weld at the junction of the fusion line. The main reason is due to the generation of weld heat affected zone or formed within the quenched structure, under high stress, caused by the rupture of the grains, when welding high carbon content of the alloying elements more easily or hardened steel, the prone to cold cracking . Excessive weld melt into hydrogen, can cause cold cracking. Crack is the most dangerous kind of defect, which in addition to reducing carry-section outside , but also have serious stress concentration in the use of crack will gradually expand, may eventually lead to the destruction member. So welded structures generally do not allow the existence of such defect , a shovel was found to be necessary to re-welding.
Porosity of the weld metal at high temperatures, excessive absorption of the gas (e.g., H2) or because the bath inside the metallurgical reaction gases (e.g., CO), the bath is cooled and solidified in the time to discharge, and in the inside or the surface of the weld cavities, namely pores. The presence of pores reduces the effective work weld cross section, decreasing the mechanical strength of the joint. If penetrating pores or continuity exists, it will seriously affect the tightness of the weldment. After the welding process, cracks or welding, metal in the welded joint region appears is called a partial fracture cracks. Cracks may occur in the weld may also be generated on both sides of the weld heat affected zone. Sometimes produced in the metal surface, the metal may be generated internally.
Generally in accordance with the mechanism of crack formation can be divided into two types of thermal cracking and cold cracking. Thermal cracking is generated by a liquid to a solid state crystallization process in the weld metal, mostly produced in the weld metal. The main cause of the existence of the low-melting substances (such as FeS, m.p. 1193 ℃) weld which weakens the contact between the grains when subjected to high welding stress, it is easy to cause breakdown between the grains. Weldments and welding rod containing S, Cu impurities such a long time, it is prone to hot cracking. Thermal cracks along the grain boundary characteristic distribution. When the crack through the surface and the outside world, the tendency has obvious hydrogenation. Cold cracks are generated in the cooling process after welding, mostly produced in the base metal or base metal and the weld at the junction of the fusion line. The main reason is due to the generation of weld heat affected zone or formed within the quenched structure, under high stress, caused by the rupture of the grains, when welding high carbon content of the alloying elements more easily or hardened steel, the prone to cold cracking . Excessive weld melt into hydrogen, can cause cold cracking. Crack is the most dangerous kind of defect, which in addition to reducing carry-section outside , but also have serious stress concentration in the use of crack will gradually expand, may eventually lead to the destruction member. So welded structures generally do not allow the existence of such defect , a shovel was found to be necessary to re-welding.
IF tube seam welded pipe line annealing equipment
With weld annealing method, the company can produce high-grade steel pipe. Pipe induction annealing apparatus is an induction heater as a main component of the continuous welded mechanical, welded and quenched to just weld the pipe is heated to above the critical temperature, quenched and annealed steel pipe weld, the weld stress and to minimize the potential crack, resulting fine grain structure can be guaranteed to meet all the requirements of the standard tough steel. As the weld rapid local heating, making steel oxidation and deformation are minimal, accurate and consistent diathermy been fine grain structure also makes the entire weld area and base metal converge.
Center console is the core set of equipment, and set up a manual or automatic conversion, automatic function control system consists of PLC, touch control screen, high-precision thermometer, etc., to achieve a complete high-precision closed-loop temperature control, temperature control accuracy of less than 1%, to ensure the stability of the quality of the steel pipe annealing.
Heating temperature can be set by the man-machine interface (touch screen), you set the parameters according to different specifications and material of the pipe. Internal system can store five kinds of equipment operating data to be stored after adjustment for different pipe size, material, and later have the same specification steel annealing can be directly transferred out of its further ensure the stability of the steel annealing quality, very great convenience to users. Programmable controller for water, electricity and all-round monitoring, alarm and event of a failure, the system immediately stop heating, to ensure the safe operation of the system and displays the fault location can quickly find fault, to resume production.
Center console is the core set of equipment, and set up a manual or automatic conversion, automatic function control system consists of PLC, touch control screen, high-precision thermometer, etc., to achieve a complete high-precision closed-loop temperature control, temperature control accuracy of less than 1%, to ensure the stability of the quality of the steel pipe annealing.
Heating temperature can be set by the man-machine interface (touch screen), you set the parameters according to different specifications and material of the pipe. Internal system can store five kinds of equipment operating data to be stored after adjustment for different pipe size, material, and later have the same specification steel annealing can be directly transferred out of its further ensure the stability of the steel annealing quality, very great convenience to users. Programmable controller for water, electricity and all-round monitoring, alarm and event of a failure, the system immediately stop heating, to ensure the safe operation of the system and displays the fault location can quickly find fault, to resume production.
Spiral seam welded pipe hydrostatic burst test
Spiral seam welded pipe hydrostatic burst test is a destructive test, tube sheet through the entire board surface ultrasonic flaw inspection, pipe weld inspection through the X-ray inspection, hydrostatic testing, ultrasonic flaw detection, thickness and tensile after passing performance test to pass as a pipe burst test tube. For the important oil and gas pipelines with spiral welded pipe, in the book require technical standard pipe manufacturers do hydrostatic burst test, and provide a burst test report.
Blasting field locations should be selected in a safe place in the absence of personnel and motor vehicles through; If set in the underground or semi-underground, but also set an alert when blasting test mark, to prevent personnel and motor vehicles. The device consists of blasting proving ground burst test units, feed pumps, high-pressure injection pump, electric control box, computer control systems, pressure sensors, temperature sensors and other components. 4m from the bursting pipe installed at both ends of the process of electronic cameras, surveillance blast site, can be seen bursting through the monitor screen.
By blasting tests to verify product performance and process rationality. Design units and provide reference data for the bursting pressure; pipe manufacturers to find areas of improvement through test analysis helps to improve product quality. Spiral seam welded pipe burst test device. Spiral seam welded pipe manufacturers should have burst Proving Ground, generally divided into temporary and permanent blasting blasting Proving Ground test site.
Blasting field locations should be selected in a safe place in the absence of personnel and motor vehicles through; If set in the underground or semi-underground, but also set an alert when blasting test mark, to prevent personnel and motor vehicles. The device consists of blasting proving ground burst test units, feed pumps, high-pressure injection pump, electric control box, computer control systems, pressure sensors, temperature sensors and other components. 4m from the bursting pipe installed at both ends of the process of electronic cameras, surveillance blast site, can be seen bursting through the monitor screen.
By blasting tests to verify product performance and process rationality. Design units and provide reference data for the bursting pressure; pipe manufacturers to find areas of improvement through test analysis helps to improve product quality. Spiral seam welded pipe burst test device. Spiral seam welded pipe manufacturers should have burst Proving Ground, generally divided into temporary and permanent blasting blasting Proving Ground test site.
Drawback of magnetic particle testing or penetration detection
Magnetic particle testing or penetration detection can be useful to find the appearance of cracks, folds, double skin, hairline, pinhole appearance shortcomings. About ferromagnetic materials, magnetic particle testing method should be preferred, because of its high detection sensitivity; on non-ferromagnetic materials, such as stainless steel seamless pipe, then use soaked detection.
When the two remaining reserved ADX less, because the layout reasons detecting apparatus, two heads are sometimes not useful in detecting, and the end is capable of cracks or other defects site. If there is a potential end cracking tendency of the weld heat affected apparatus also allows potential expansion of cracks. Thus, we should also pay attention to the detection zone must seamless steel welding, expanding pipe ends to discover defects. On -line use of austenitic seamless insulation is damaged or when to have rain infiltrated the site, should be soaked focus detection to detect stress corrosion cracking or pitting and other shortcomings. However, detection of magnetic or soaked steel outer appearance can only be detected, internal appearance of the shortcomings of the powerless. Detection of internal appearance, particularly the detection of cracks class disadvantage, it is necessary to carry out after ultrasonic detector.
When the two remaining reserved ADX less, because the layout reasons detecting apparatus, two heads are sometimes not useful in detecting, and the end is capable of cracks or other defects site. If there is a potential end cracking tendency of the weld heat affected apparatus also allows potential expansion of cracks. Thus, we should also pay attention to the detection zone must seamless steel welding, expanding pipe ends to discover defects. On -line use of austenitic seamless insulation is damaged or when to have rain infiltrated the site, should be soaked focus detection to detect stress corrosion cracking or pitting and other shortcomings. However, detection of magnetic or soaked steel outer appearance can only be detected, internal appearance of the shortcomings of the powerless. Detection of internal appearance, particularly the detection of cracks class disadvantage, it is necessary to carry out after ultrasonic detector.
Thursday, November 21, 2013
Prevent intergranular stress corrosion cracking method
As intergranular stress corrosion cracking is probably caused because of the chromium depleted zone, preventing intergranular stress corrosion cracking method may include post-weld heat treatment to restore the diffusion of chromium, the carbon content to very low levels and adding titanium to inhibit precipitation of chromium carbide.
To determine the impact of post-weld heat treatment, the carbon material of 100ppm two passes through a heating cycle sensitization, followed by the different conditions in the third pass of the heating cycle. Similar to the above using U -bend stress-corrosion cracking test to evaluate the samples prepared. The results showed that the range of 550 ~ 700 ℃ heated few minutes, sensitized specimens crack. This effect may be due to the heat treatment to increase the diffusion of chromium, thus narrowing the chromium depleted zone. PWHT using short (a few minutes), you can prevent intergranular stress corrosion cracking, which is the actual laying of pipeline efficiency without hinder.
To determine the lower carbon content, and adding titanium influence on different carbon content and the titanium content of the material was evaluated. The samples were 450 ℃, 1000s a heating cycle of treatment, this condition is likely to cause sensitization, a similar U-shaped pattern bending stress corrosion cracking tests. With the change of test conditions, the U-shaped bend in the sample by generating a gap. The results show that addition of titanium to reduce carbon content and inhibit the generation of cracks. This is probably because the soldering is suppressed and the dissolution of carbon into titanium carbide and chromium depleted suppressed cause precipitation of chromium carbides. Therefore, reducing the carbon content and the addition of titanium to improve the material resistance to intergranular stress corrosion cracking an effective manner.
To determine the impact of post-weld heat treatment, the carbon material of 100ppm two passes through a heating cycle sensitization, followed by the different conditions in the third pass of the heating cycle. Similar to the above using U -bend stress-corrosion cracking test to evaluate the samples prepared. The results showed that the range of 550 ~ 700 ℃ heated few minutes, sensitized specimens crack. This effect may be due to the heat treatment to increase the diffusion of chromium, thus narrowing the chromium depleted zone. PWHT using short (a few minutes), you can prevent intergranular stress corrosion cracking, which is the actual laying of pipeline efficiency without hinder.
To determine the lower carbon content, and adding titanium influence on different carbon content and the titanium content of the material was evaluated. The samples were 450 ℃, 1000s a heating cycle of treatment, this condition is likely to cause sensitization, a similar U-shaped pattern bending stress corrosion cracking tests. With the change of test conditions, the U-shaped bend in the sample by generating a gap. The results show that addition of titanium to reduce carbon content and inhibit the generation of cracks. This is probably because the soldering is suppressed and the dissolution of carbon into titanium carbide and chromium depleted suppressed cause precipitation of chromium carbides. Therefore, reducing the carbon content and the addition of titanium to improve the material resistance to intergranular stress corrosion cracking an effective manner.
Tank ultrasonic flaw detection precision tubes Analysis
Sink is the use of ultrasonic detection precision tubes spin forward type, ultrasound probe stationary. Chongqing Precision Pipe Factory technicians mentioned were seized through gutters and precision tubes full of water at the bottom of the coupling characteristics, to ensure the thickness of the coupling constant. But because ultrasonic detection of internal defects on the surface of the main and sub- surface defects exist blind, preventing detection, coupled with spiral forward type, precision tubes for 12m long 30m venue needs such as space shortage has affected the precision tube detection method selection and promotion.
Therefore, the domestic large-caliber precision tubes for the detection, commonly used magnetic flux leakage method or hydrostatic test. In China, good performance is still not suitable for large -caliber precision tubes produced magnetic flux leakage testing equipment, the use of which is imported. Imported magnetic flux leakage detection equipment is expensive, for the majority of domestic enterprises is difficult to accept; while the hydraulic test inefficient, labor-intensive, especially when the operator is not high sense of responsibility, the water pressure test useless. Visible to achieve large-diameter seamless precision tubes metallurgical testing has become the steel industry problems to be solved.
Large diameter pipe is characterized by precision large diameter, wall thickness is relatively thick, so take advantage of this feature under ultrasound and eddy current testing internal surface and subsurface features combine to achieve "blind" testing. Through the use of "precision tubes in situ rotation detection probe forward combinations," not only solve the detection problem, but also solve the narrow space occupied space.
Therefore, the domestic large-caliber precision tubes for the detection, commonly used magnetic flux leakage method or hydrostatic test. In China, good performance is still not suitable for large -caliber precision tubes produced magnetic flux leakage testing equipment, the use of which is imported. Imported magnetic flux leakage detection equipment is expensive, for the majority of domestic enterprises is difficult to accept; while the hydraulic test inefficient, labor-intensive, especially when the operator is not high sense of responsibility, the water pressure test useless. Visible to achieve large-diameter seamless precision tubes metallurgical testing has become the steel industry problems to be solved.
Large diameter pipe is characterized by precision large diameter, wall thickness is relatively thick, so take advantage of this feature under ultrasound and eddy current testing internal surface and subsurface features combine to achieve "blind" testing. Through the use of "precision tubes in situ rotation detection probe forward combinations," not only solve the detection problem, but also solve the narrow space occupied space.
Tuesday, November 19, 2013
Lsaw steel pipe heat treatment technology in steel structure
LSAW steel pipe heat treatment technology form the temperature difference in the heating and cooling process because of the central portion of the cooling surface and the speed and time of inconsistencies, volume expansion and contraction will cause uneven stress, the thermal stress. Under the effect of thermal stress, because the surface temperature is below the core part begins, shrinkage core portion by the central portion is greater than the tension, when the end of cooling, since the volume shrinkage of the cooling core section last leaving the surface pressure can not freely central portion tension. That is, in the final thermal stress under the action of the workpiece surface pressure while the heart of tension. This phenomenon is cooled rate, material composition and heat treatment process and other factors.
When cooled, the faster, the higher the carbon content and the alloy composition, the cooling process under thermal stress generated in the non-uniform plastic deformation larger, the final form of the residual stress it gets. The other hand, during the heat treatment of steel changes in the organization that the austenite to martensite transition, will be accompanied by an increase in specific volume due to the volume expansion of the workpiece, the workpiece successively all parts of the phase change, resulting in inconsistent grown produce tissue volume stress.
When cooled, the faster, the higher the carbon content and the alloy composition, the cooling process under thermal stress generated in the non-uniform plastic deformation larger, the final form of the residual stress it gets. The other hand, during the heat treatment of steel changes in the organization that the austenite to martensite transition, will be accompanied by an increase in specific volume due to the volume expansion of the workpiece, the workpiece successively all parts of the phase change, resulting in inconsistent grown produce tissue volume stress.
Longitudinal stability of thick-walled molding
Longitudinal use from the nearest point of view, using hydroformed tubes used in auto parts concern. Using the hydroforming process systems due to complexity, large pressure, therefore possible to improve the workability of steel. However, previous evaluations steel workability indicators are not clear, I hope to develop a simple evaluation processing technology.
As the hydraulic tube forming equipment is huge, high prices, so the compact hydraulic forming equipment in high demand by the automobile manufacturers and steel plants work together to develop a new concept of compact hydraulic forming equipment. For the production of thick-walled welded pipe, some manufacturers have developed resistance welding and laser welding and high frequency welding combined with technology. In the past, laser welding for the production of stainless steel, will be applied to the welded steel pipe forming speed production lines forming the first time. This technology is due to the development of high power laser generating device before achieved. From a manufacturing technical point of view, the stability of the thick-walled pipe and weld portion forming process technology as key to the development, of low deformation tube technology developed in Japan CBR technique which can produce high-strength steel good processability.
As the hydraulic tube forming equipment is huge, high prices, so the compact hydraulic forming equipment in high demand by the automobile manufacturers and steel plants work together to develop a new concept of compact hydraulic forming equipment. For the production of thick-walled welded pipe, some manufacturers have developed resistance welding and laser welding and high frequency welding combined with technology. In the past, laser welding for the production of stainless steel, will be applied to the welded steel pipe forming speed production lines forming the first time. This technology is due to the development of high power laser generating device before achieved. From a manufacturing technical point of view, the stability of the thick-walled pipe and weld portion forming process technology as key to the development, of low deformation tube technology developed in Japan CBR technique which can produce high-strength steel good processability.
SAW straight seam steel coil manufacturing technology
In general, the coil volume header, the volume at the end of the board edge straightness easily exceeded, and prone to heavy skin folds, scars, indentations, scratches and other imperfections and defects, and thus cut steel Kaiping, the appearance and geometric dimensions conform to the technical requirements of the plate lower pass rate, calculated based on the volume weight and the actual weight per unit length of the coil, the budget out of steel rolls long, the whole rationale for determining the shear length and number of sheets of qualified steel; same time as the on-site inspection volume Kaiping head and capuchin defects in real time straight from the severe degree of excessive volumes and closing coil be cut; straightness exceeded for larger volume header plates and capuchin plate edge milling to increase the amount.
Due to the volume board without slitting, rolling board edge defects and imperfections easily exist, such as heavy paper, folded, scarring, indentations, scratches, etc., which feed on the road when the first steel reinforced manual inspection. In addition, because billet steel hot rolled into plates immediately after a coil winding, coiling temperature of 500-600 degrees Celsius, and therefore can not be in the steel mills UT hierarchical testing, coil quality can not be guaranteed. So steel technical conditions "are subject to 100% of all steel stratified testing for 100% of the scan." Domestic steel plant in the feeding line are equipped ultrasonic flaw detection process layering, layering plates thus conducted online testing can be achieved, but the scan area, generally scan area can reach 25 % or more. To improve the scanning coverage of the probe of the packet is changed to a slow walk straight swing back and forth scan, the scan area can be increased to 40 % or more, to ensure the quality of the inner plate line.
Collage volume level edge milling and forming, welding and outside the pre- welding, weld and weld edges enhance elimination board edge defect inspection is the best way. X-ray tube weld industrial TV or X-ray film examination to strengthen the seam side edges 20-50mm base material inspection, pipe automatic weld seam edges UT flaw detection increases stratified parent material testing and inspection, can be very ensure good quality steel pipe weld edge.
Due to the volume board without slitting, rolling board edge defects and imperfections easily exist, such as heavy paper, folded, scarring, indentations, scratches, etc., which feed on the road when the first steel reinforced manual inspection. In addition, because billet steel hot rolled into plates immediately after a coil winding, coiling temperature of 500-600 degrees Celsius, and therefore can not be in the steel mills UT hierarchical testing, coil quality can not be guaranteed. So steel technical conditions "are subject to 100% of all steel stratified testing for 100% of the scan." Domestic steel plant in the feeding line are equipped ultrasonic flaw detection process layering, layering plates thus conducted online testing can be achieved, but the scan area, generally scan area can reach 25 % or more. To improve the scanning coverage of the probe of the packet is changed to a slow walk straight swing back and forth scan, the scan area can be increased to 40 % or more, to ensure the quality of the inner plate line.
Collage volume level edge milling and forming, welding and outside the pre- welding, weld and weld edges enhance elimination board edge defect inspection is the best way. X-ray tube weld industrial TV or X-ray film examination to strengthen the seam side edges 20-50mm base material inspection, pipe automatic weld seam edges UT flaw detection increases stratified parent material testing and inspection, can be very ensure good quality steel pipe weld edge.
Straight seam welded steel pipe heat treatment
Straight seam steel pipe weld heat treatment is a new technique to eliminate residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals.
NDT weld inside the pipe in the water supply as part of large steel works, especially the thickness t=30mm steel tube is used as a pipe bridge, both to withstand the water pressure, but also the burden of weight and water from the pipe forming moment, so the welding quality requirements are particularly high. For pipe bridge of t=30mm thick with a large-diameter steel pipe, the longitudinal seam and girth welds belong to a class, require 100% of X-ray film examination and 100 % of the ultrasonic flaw detection; while the thickness t=24mm buried pipe, belongs to a class of longitudinal seam welding, for 20 % of the X-ray film examination and 50 % of the ultrasonic flaw inspection.
Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. Large diameter steel pipe weld heat treatment can effectively improve the large-diameter steel pipe stress corrosion resistance, heat treatment temperature is higher, increasing resistance to stress corrosion is more significant. Diffusion of metal carbide coating technology is the workpiece on special media, the diffusion layer is formed on the surface of several microns to several tens of micrometers of the metal carbide layer. Large diameter steel pipe anti-corrosion of buried pipes and tubes inside out corrosion, are used to hang galvanized wire, spraying compressive strength of not less than 30N/mm2 cement mortar lining.
NDT weld inside the pipe in the water supply as part of large steel works, especially the thickness t=30mm steel tube is used as a pipe bridge, both to withstand the water pressure, but also the burden of weight and water from the pipe forming moment, so the welding quality requirements are particularly high. For pipe bridge of t=30mm thick with a large-diameter steel pipe, the longitudinal seam and girth welds belong to a class, require 100% of X-ray film examination and 100 % of the ultrasonic flaw detection; while the thickness t=24mm buried pipe, belongs to a class of longitudinal seam welding, for 20 % of the X-ray film examination and 50 % of the ultrasonic flaw inspection.
Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. Large diameter steel pipe weld heat treatment can effectively improve the large-diameter steel pipe stress corrosion resistance, heat treatment temperature is higher, increasing resistance to stress corrosion is more significant. Diffusion of metal carbide coating technology is the workpiece on special media, the diffusion layer is formed on the surface of several microns to several tens of micrometers of the metal carbide layer. Large diameter steel pipe anti-corrosion of buried pipes and tubes inside out corrosion, are used to hang galvanized wire, spraying compressive strength of not less than 30N/mm2 cement mortar lining.
Tuesday, November 12, 2013
Longitudinal and spiral welded differences and blasting methods
The main difference of longitudinal and spiral welded pipe lies in the two different production processes, the formation of the first Longitudinal molding machine through the first hot rolled coil shape, so that it becomes smooth cylindrical outer surface, and then soldering, welding or the use of a solder layer of the proximity effect of arcing and burning of the skin effect, the edge of the heating tube and melted in a suitable cooled compression molding. LSAW and ERW tube edge is melted in different ways by the distinction, generally called by arc melting LSAW steel pipe and ERW is the use of high-frequency current melted. Spiral welded pipe production process is to follow the appropriate helix angle of the low-carbon low-alloy structural steel and carbon steel coils into the tube, and then seam welded pipe forming. Spiral welded pipe spiral submerged arc welded pipe is the main form. Can narrow the billet production of large diameter spiral steel pipe is the most significant feature is widely used in all walks of life of the gas pipeline construction.
To reduce the quality of the coating, layer type and construction of environmental factors on the life of the coating Longitudinal should be regularly Longitudinal rust. There are four common rust, namely, pickling, cleaning, descaling and tools rust spray. Pickling is the most common ways of rust, sand-blasting not only can be used as a further treatment step after, but also the Longitudinal surface rust, scale, old coatings completely removed, although this cleaning method make steel surface roughness and cleanliness requirements are up to par, but that is a chemical cleaning method, likely to cause pollution of the surrounding environment. Straight seam steel pipes cleaned only as an adjunct to anti-corrosion treatment, because the steel surface cleaning methods can only dust, grease and lubricants and other residual organics removed, and can not play antiseptic effect, as we usually wash Like, you can clean the surface of the dirt, most bacteria are still left in the hand. Professional and technical personnel with a wire brush and other cleaning tools on the surface to be polished, this approach is known tools rust, loose rust, welding slag and oxide so can be completely removed, but for steel surface firmly attached oxide is powerless and can not achieve the standard preservative effect. Jet is the use of grit blasting, steel shot abrasive materials such as high-quality powerful centrifugal force through the jet to jet straight seam steel surface, not only can effectively remove surface dirt, rust and oxides, etc., will be as abrasive roughness Longitudinal friction and achieve the standard required under the action.
To reduce the quality of the coating, layer type and construction of environmental factors on the life of the coating Longitudinal should be regularly Longitudinal rust. There are four common rust, namely, pickling, cleaning, descaling and tools rust spray. Pickling is the most common ways of rust, sand-blasting not only can be used as a further treatment step after, but also the Longitudinal surface rust, scale, old coatings completely removed, although this cleaning method make steel surface roughness and cleanliness requirements are up to par, but that is a chemical cleaning method, likely to cause pollution of the surrounding environment. Straight seam steel pipes cleaned only as an adjunct to anti-corrosion treatment, because the steel surface cleaning methods can only dust, grease and lubricants and other residual organics removed, and can not play antiseptic effect, as we usually wash Like, you can clean the surface of the dirt, most bacteria are still left in the hand. Professional and technical personnel with a wire brush and other cleaning tools on the surface to be polished, this approach is known tools rust, loose rust, welding slag and oxide so can be completely removed, but for steel surface firmly attached oxide is powerless and can not achieve the standard preservative effect. Jet is the use of grit blasting, steel shot abrasive materials such as high-quality powerful centrifugal force through the jet to jet straight seam steel surface, not only can effectively remove surface dirt, rust and oxides, etc., will be as abrasive roughness Longitudinal friction and achieve the standard required under the action.
The choice of straight seam submerged arc welding steel pipe
(1) required for the high peak pipeline, because the user's gas consumption is very uneven, frequent fluctuations in the pipeline pressure, alternating steel to withstand the stress is large, defects will already in pipes alternating stress expansion if optional multi- weld defect high probability spiral welded steel pipe, pipeline safety operations will not be guaranteed.
(2) Pipeline crossing earthquake fault or through local high intensity earthquake zone, because these lots geologically active, which will have a vertical or axial pipe alternating stress. Spiral weld is much higher chance than LSAW steel pipe, in the long term stress, spiral welded steel pipe is much higher than the chance of an accident LSAW steel pipe, therefore, in this zone should be used straight submerged arc welded pipe.
(3) internal and external coating demanding pipes, LSAW steel pipes should be used. Multi- spiral submerged arc welded pipe weld, the weld reinforcement generally higher than LSAW high on steel pipe inside and outside corrosion, the corrosion-resistant materials combined with the bare pipe LSAW degree as closely antiseptic effect is not good LSAW steel pipes.
(4) For critical wear crossing project, you should use LSAW steel pipe. Since future maintenance and management difficulties than the general line segment, therefore, with excellent performance LSAW particularly necessary.
(5) For piping weak links, such as hot simmer elbow pipe, LSAW steel pipe should be used. Hot simmer elbow as change of direction, which is subject to external forces than the general lines of straight pipe should be large, because the simmer process affected by various factors, the stress is not easy to eliminate long-distance pipeline is weak link using an integrated LSAW good performance can make up for these deficiencies.
(2) Pipeline crossing earthquake fault or through local high intensity earthquake zone, because these lots geologically active, which will have a vertical or axial pipe alternating stress. Spiral weld is much higher chance than LSAW steel pipe, in the long term stress, spiral welded steel pipe is much higher than the chance of an accident LSAW steel pipe, therefore, in this zone should be used straight submerged arc welded pipe.
(3) internal and external coating demanding pipes, LSAW steel pipes should be used. Multi- spiral submerged arc welded pipe weld, the weld reinforcement generally higher than LSAW high on steel pipe inside and outside corrosion, the corrosion-resistant materials combined with the bare pipe LSAW degree as closely antiseptic effect is not good LSAW steel pipes.
(4) For critical wear crossing project, you should use LSAW steel pipe. Since future maintenance and management difficulties than the general line segment, therefore, with excellent performance LSAW particularly necessary.
(5) For piping weak links, such as hot simmer elbow pipe, LSAW steel pipe should be used. Hot simmer elbow as change of direction, which is subject to external forces than the general lines of straight pipe should be large, because the simmer process affected by various factors, the stress is not easy to eliminate long-distance pipeline is weak link using an integrated LSAW good performance can make up for these deficiencies.
Monday, November 4, 2013
Precision light pipe welding temperature
Precision bright tubes solid tube inspection and removal of surface defects, cut into desired length, end to end in the perforated tube surface-centering, and then sent to the furnace heating, punch a hole. In the hole while continuing to rotate and move forward in the roll and the role of the head, gradually formed within the tube cavity, called the capillary. And then sent to the automatic rolling machine to continue rolling. Finally after all the whole entire wall thickness are, after sizing mill sizing, to specifications. Use of continuous pipe mill producing hot-rolled precision light pipe is a more advanced methods. If you wish to get smaller and better quality seamless, must be rolled, drawn or a combination of methods. Cold is usually performed on two-roll mill, pipe hole in the variable section tapered slot and does not move the head of the circular hole formed in the rolling. Drawing is usually 0.5 ~ 100T single chain or double chain drawing machine on. Heating tube extrusion method is about good squeeze on the closed cylinder, perforated extruded rod rod and move together, so that extrusion from the smaller hole in the extrusion die. This method can produce smaller diameter of the pipe. After coating the coating material on the precision light pipe ri pretreatment indirectly affect the quality of the coating off the power attached to compete.
Titanium solid solution strengthening effect is strong, but the toughness of reducing solid solution, solid solution in austenite to improve the hardenability of steel, but titanium compounds , but lower hardenability of steel. Improve the tempering stability, and a secondary hardening effect in enhancing the oxidation resistance and heat resistant steel heat resistance, such as creep and rupture strength, and improve the weldability of steel. Precision light pipe welding temperature is mainly affected by the impact of high-frequency eddy current heating power, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current, and capacitance, inductance. Use of this technology and the production of hot-rolled steel welded pipe common essential difference between the high-frequency furnace heating the weld through the parent microstructure and mechanical properties can be achieved entirely consistent Additionally, multiple passes through the tension -reducing rolling machines and automatic control makes precision light pipe size accuracy (especially tube roundness and wall thickness accuracy) than similar. Produced in the developed world, fluid pipes, boiler tubes have been widely used pipe seamless process, with the development of society, domestic hot-rolled precision light pipe welded to gradually replace the situation has been formed.
Titanium solid solution strengthening effect is strong, but the toughness of reducing solid solution, solid solution in austenite to improve the hardenability of steel, but titanium compounds , but lower hardenability of steel. Improve the tempering stability, and a secondary hardening effect in enhancing the oxidation resistance and heat resistant steel heat resistance, such as creep and rupture strength, and improve the weldability of steel. Precision light pipe welding temperature is mainly affected by the impact of high-frequency eddy current heating power, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current, and capacitance, inductance. Use of this technology and the production of hot-rolled steel welded pipe common essential difference between the high-frequency furnace heating the weld through the parent microstructure and mechanical properties can be achieved entirely consistent Additionally, multiple passes through the tension -reducing rolling machines and automatic control makes precision light pipe size accuracy (especially tube roundness and wall thickness accuracy) than similar. Produced in the developed world, fluid pipes, boiler tubes have been widely used pipe seamless process, with the development of society, domestic hot-rolled precision light pipe welded to gradually replace the situation has been formed.
Precision light pipe fundamental properties of liquid metals
Density of atoms in the liquid light pipe as heat energy is still larger, higher precision light control its intensity in three dimensions each atom adjacent atoms are often collide with each other, replacing energy. In the collision, some energy to the atoms in the other a fragmentary atoms, and their energy declined. Precision light pipe is all the time there are some consequences of atomic energy even beyond atomic energy, some of the energy of atomic energy is much smaller than the uniform. Precision light pipe heterogeneity of this energy is called energy fluctuation. Energy fluctuation exist in liquid form within the group each atom has a larger atomic kinetic energy near the atomic overcome the constraints (joint formed between atoms barrier), in addition to strong heat occurring within the group still (vacancy occurs and dispersion) in addition, precision light pipe also in clusters from the original groups were added to other atomic groups or form new atomic groups. Thus, precision light pipe despite everything ferrite grain atomic groups are in a rapidly changing situation, sometimes grow and sometimes smaller, sometimes occurs and sometimes disappear, one after another, as in swimming without pause.
This structure is called rapidly changing structure and downs. Precision light pipe above three characteristics of the liquid metal choices based features: a fixed volume , precision light pipe has good mobility, a variety of physical and chemical properties close to the solid state, and away from the gaseous state. Precision bright tubes present, at home and abroad on the nature of the liquid metal to make a small amount of research, here only u stagnation of liquid metal, basic physical appearance and sense of nature scenes. Study the chemical composition of metal species indicated, individual state comparable metal different than the coefficient of friction of the contact metal to be large; each other can cause friction between the alloying metal, can not be compared with each other alloys or compounds caused to a large coefficient of friction. Precision light pipe without smooth conditions, some pure metal contact practice coefficient of friction. However, in practice, the course of the rolling appearance much smaller than the coefficient of friction between the net coefficient of friction between the metal surface. Precision light pipe because of the nature and status of seizures practice appearance change, so changes to the friction conditions episodes, such as the change from the adhesive friction sliding friction, the friction coefficient will lead to landing.
This structure is called rapidly changing structure and downs. Precision light pipe above three characteristics of the liquid metal choices based features: a fixed volume , precision light pipe has good mobility, a variety of physical and chemical properties close to the solid state, and away from the gaseous state. Precision bright tubes present, at home and abroad on the nature of the liquid metal to make a small amount of research, here only u stagnation of liquid metal, basic physical appearance and sense of nature scenes. Study the chemical composition of metal species indicated, individual state comparable metal different than the coefficient of friction of the contact metal to be large; each other can cause friction between the alloying metal, can not be compared with each other alloys or compounds caused to a large coefficient of friction. Precision light pipe without smooth conditions, some pure metal contact practice coefficient of friction. However, in practice, the course of the rolling appearance much smaller than the coefficient of friction between the net coefficient of friction between the metal surface. Precision light pipe because of the nature and status of seizures practice appearance change, so changes to the friction conditions episodes, such as the change from the adhesive friction sliding friction, the friction coefficient will lead to landing.
Thursday, October 31, 2013
Buried gas pipeline corrosion problems
If all the re- excavation of pipeline corrosion, effort, and cost is enormous, only the implementation of the cathodic protection system is the most economical and easy solution , but because of pipeline construction without appropriate insulation measures and difficult to stop gas for insulation transformation, also difficult to obtain because there is no insulation and pipe -related parameters, so it can not be implemented before the relevant cathodic protection process calculation, which gives the cathodic protection system implementation has brought great difficulties. Cathodic protection methods are forced current law and the sacrificial anode protection laws, which force the current method due to the pipeline without insulation and building pipelines in multi- family area environment, technically feasible, it is difficult to use sacrificial anode cathodic protection law in the implementation of, since the anode at a certain distance pipelines laid in place, avoid other buildings and underground piping is protected against the impact of pipeline and technically feasible, so as to prevent the continuation of the development of corrosion, the use of sacrificial anode cathodic protection.
Soil environment in which the pipeline can not be changed, so we use the most simple way for family wings branch pipeline insulation insulation transform this transformation in the surge tank can be carried out at the flange, ie the surge tank flange screw plus insulating sleeve, the use of PTFE insulation pads, while the flange gasket without replacing the original asbestos mat, so stop making pipeline protection potential output has reached eleven, the realization will be, will be fully protected pipeline. To the factory area two parallel pipelines buried a short distance though, but after entering the factory overhead to each workshop, all of the overhead steel pipe support brackets, the number of overhead line length of about stents, each bracket is a ground point Meanwhile, the plant area electrolysis plant and other major electricity system grounding, causing stray current interference of the pipeline is also very obvious. This requires a large ground exclude exclude stray current interference impact of the pipeline. The best solution is in the pipeline overhead before installing insulation or insulating flange joints, were insulated transformation, then ground and stray interference issues have been resolved accordingly, but because of all gas production plant in the region, stop gas transformation will force production stopped, will lead to huge economic losses. Interference from stray current drain approaches can be taken to resolve the basic solution is buried pipeline overhead before installing zinc anodes with one hand, so that stray current through the zinc anode grounded to earth stray current row of people, partly because zinc anode has a more negative potential than steel, providing cathodic current can give pipeline, drainage and protection to achieve the dual purpose. But no matter what measures the exhaust stream draining grounding grounding resistance should be less than pipe body resistance, draining effect was obvious. However, due to high soil resistivity pipeline which should produce a ground resistance of less than pipe body resistance grounding is very difficult, but because the ground is used in zinc anode material is very expensive, can be installed to protect the pipeline, also Shangqie I do not know. In order to avoid blindness and unnecessary economic losses, we do not make any insulation transformation cases, an analog current cathodic protection test. To determine the case of non-insulated pipeline in the end require much cathode current cathodic protection system which re- determine the best solution embodiment.
Soil environment in which the pipeline can not be changed, so we use the most simple way for family wings branch pipeline insulation insulation transform this transformation in the surge tank can be carried out at the flange, ie the surge tank flange screw plus insulating sleeve, the use of PTFE insulation pads, while the flange gasket without replacing the original asbestos mat, so stop making pipeline protection potential output has reached eleven, the realization will be, will be fully protected pipeline. To the factory area two parallel pipelines buried a short distance though, but after entering the factory overhead to each workshop, all of the overhead steel pipe support brackets, the number of overhead line length of about stents, each bracket is a ground point Meanwhile, the plant area electrolysis plant and other major electricity system grounding, causing stray current interference of the pipeline is also very obvious. This requires a large ground exclude exclude stray current interference impact of the pipeline. The best solution is in the pipeline overhead before installing insulation or insulating flange joints, were insulated transformation, then ground and stray interference issues have been resolved accordingly, but because of all gas production plant in the region, stop gas transformation will force production stopped, will lead to huge economic losses. Interference from stray current drain approaches can be taken to resolve the basic solution is buried pipeline overhead before installing zinc anodes with one hand, so that stray current through the zinc anode grounded to earth stray current row of people, partly because zinc anode has a more negative potential than steel, providing cathodic current can give pipeline, drainage and protection to achieve the dual purpose. But no matter what measures the exhaust stream draining grounding grounding resistance should be less than pipe body resistance, draining effect was obvious. However, due to high soil resistivity pipeline which should produce a ground resistance of less than pipe body resistance grounding is very difficult, but because the ground is used in zinc anode material is very expensive, can be installed to protect the pipeline, also Shangqie I do not know. In order to avoid blindness and unnecessary economic losses, we do not make any insulation transformation cases, an analog current cathodic protection test. To determine the case of non-insulated pipeline in the end require much cathode current cathodic protection system which re- determine the best solution embodiment.
Discussion of the gas pipeline corrosion
Because the pipeline internal corrosion caused by gas leaks, explosions occupies a large proportion of the pipeline after doing inner coating can effectively suppress the occurrence of internal corrosion, thereby improving pipeline safety. The other hand, the level of efficiency of gas pipeline transmission and distribution projects in the pipeline is a measure put into operation one of the main symbol of good and bad, and pipeline efficiency and pipe wall roughness to some extent.
The organic coated steel pipes for the surface- coating with excellent corrosion resistance, chemical stability and good molding properties. Steel substrate with high mechanical strength, impact resistance, resistance to bending. The combination of organic coatings and steel focused on the advantages of both. Applications in the oil industry drill drilling organic coatings, containing hydrogen sulfide, salt, a very high temperature and pressure operating under poor working conditions, the actual use of the drill pipe is subsequently proved that organic coatings with good corrosion resistance, its service life than the non- coated with organic coatings increased by 2 to 3 times. Organic coating steel pipes are used than non- coated with organic coatings life of the pipeline increased by 3 to 4 times. When the organic coated steel pipes for laying in the ground, due to the presence of the coating, forms a good insulating layer, weakening the stray current corrosion. Organic coating smooth surface smooth, easy to breed bacteria and mold, wax effectively prevent corrosion, fouling, avoid bacterial corrosion, corrosion under the scale of production.
The organic coated steel pipes for the surface- coating with excellent corrosion resistance, chemical stability and good molding properties. Steel substrate with high mechanical strength, impact resistance, resistance to bending. The combination of organic coatings and steel focused on the advantages of both. Applications in the oil industry drill drilling organic coatings, containing hydrogen sulfide, salt, a very high temperature and pressure operating under poor working conditions, the actual use of the drill pipe is subsequently proved that organic coatings with good corrosion resistance, its service life than the non- coated with organic coatings increased by 2 to 3 times. Organic coating steel pipes are used than non- coated with organic coatings life of the pipeline increased by 3 to 4 times. When the organic coated steel pipes for laying in the ground, due to the presence of the coating, forms a good insulating layer, weakening the stray current corrosion. Organic coating smooth surface smooth, easy to breed bacteria and mold, wax effectively prevent corrosion, fouling, avoid bacterial corrosion, corrosion under the scale of production.
Monday, October 28, 2013
Large diameter steel pipe expanding proces
Because the large diameter seamless steel pipe diameter sizes is too large, in addition to the less efficient large hot extrusion unit and large pipe jacking machine outside, we can no longer use the familiar automatic pipe mill or continuous pipe mill and other models for direct production. Thus emerged pull Dial expanding, expanding top push and rotate the three main Seamless expanding expanding process. Currently most of the world are produced in large diameter seamless steel technology three and pull Dial and top push expanding process has been applied to some large -diameter welded steel pipe production, and become part of the composition of its processes.
Pull Dial expanding process
Pull Dial Flaring machine produced in the 1930s in Germany, then to Italy, France adopted and in Italy to perfect, which is currently the world's only six units and relatively obsolete technology. To 630 units, for example CSST; several thousand tons equipment, hundreds of millions of investment, annual output of 50,000 tons. The production process must first be heated thermal expansion material as the tube end valgus cone, for fixing the tubular body. Then the overall heating tube, with a chain pull has been set into the inner mold raw tube and fitted mandrel, complete flaring. Its characteristics: high production efficiency, longer processed finished products, equipment can be reduced flaring necking multi- wall, but the equipment weight of large infrastructure investment is large, deformed steel pipe flaring continues in tension, resulting in poor product quality, external Drive low precision steel surface is not smooth, as the removal of low end valgus cone timber defects caused more prominent.
Rotate expanding process
Expansion of the machine, also known as rotary disc flaring equipment. Its name comes from its cross- tilt placed two large-diameter disk-shaped rolls similar to the device once expansion ratio of up to 70 %, which is currently the world's largest amount of time expanded diameter pipe expansion models. The device is in a 1990s Italian oblique roller mill developed on the basis adapted from. So far only four sets of the world, only Italy Dalmine unit for the most successful cases, thousands of tons of equipment over a billion construction investment, sophisticated technology, despite its high production efficiency, deformation speed, a large flaring, so that the industry is still daunting . However, if the Department were equipped machine, sizing machine composed of expanding production lines, for a large number of large -diameter pipe production is not a good solution for the vector.
Pushing expanding process
This model was invented in Germany in the 1950s, the mid-1980s to elbow pushing machine models from Japan into China. To 1997 and renovated in China perfect obtaining intellectual property, and named two -step expansion of the machine hydraulic pusher, the device is simple in principle to the hydraulic push plate will cover only the fixed cone with expanding mandrel outside the hot feed pipe pushed through flaring cone will complete the expansion work. Expanding mandrel process only occurs in the raw material tube and associated fixed connections between stress lines therefore very short. And because of the fixed plate and cylinder mandrel mandrel tube billet between the forces, this device stiffness structure greatly simplified. Two step forward in turn reduce the length of the hydraulic cylinder nearly half, so a greater extent, reduce the equipment cost and mainly from the process solution to the cylinder machining length limit. The expanding device complete with frequency heating equipment, rapid and uniform heating of raw materials controllable, uniform propulsion deformed pipes are refined microstructure and mechanical properties of materials to improve the performance guarantee uniformity of the tube to create the conditions, although the device has less investment, short construction period, simple equipment, product quality, high geometric accuracy, finished product rate, etc.
Pull Dial expanding process
Pull Dial Flaring machine produced in the 1930s in Germany, then to Italy, France adopted and in Italy to perfect, which is currently the world's only six units and relatively obsolete technology. To 630 units, for example CSST; several thousand tons equipment, hundreds of millions of investment, annual output of 50,000 tons. The production process must first be heated thermal expansion material as the tube end valgus cone, for fixing the tubular body. Then the overall heating tube, with a chain pull has been set into the inner mold raw tube and fitted mandrel, complete flaring. Its characteristics: high production efficiency, longer processed finished products, equipment can be reduced flaring necking multi- wall, but the equipment weight of large infrastructure investment is large, deformed steel pipe flaring continues in tension, resulting in poor product quality, external Drive low precision steel surface is not smooth, as the removal of low end valgus cone timber defects caused more prominent.
Rotate expanding process
Expansion of the machine, also known as rotary disc flaring equipment. Its name comes from its cross- tilt placed two large-diameter disk-shaped rolls similar to the device once expansion ratio of up to 70 %, which is currently the world's largest amount of time expanded diameter pipe expansion models. The device is in a 1990s Italian oblique roller mill developed on the basis adapted from. So far only four sets of the world, only Italy Dalmine unit for the most successful cases, thousands of tons of equipment over a billion construction investment, sophisticated technology, despite its high production efficiency, deformation speed, a large flaring, so that the industry is still daunting . However, if the Department were equipped machine, sizing machine composed of expanding production lines, for a large number of large -diameter pipe production is not a good solution for the vector.
Pushing expanding process
This model was invented in Germany in the 1950s, the mid-1980s to elbow pushing machine models from Japan into China. To 1997 and renovated in China perfect obtaining intellectual property, and named two -step expansion of the machine hydraulic pusher, the device is simple in principle to the hydraulic push plate will cover only the fixed cone with expanding mandrel outside the hot feed pipe pushed through flaring cone will complete the expansion work. Expanding mandrel process only occurs in the raw material tube and associated fixed connections between stress lines therefore very short. And because of the fixed plate and cylinder mandrel mandrel tube billet between the forces, this device stiffness structure greatly simplified. Two step forward in turn reduce the length of the hydraulic cylinder nearly half, so a greater extent, reduce the equipment cost and mainly from the process solution to the cylinder machining length limit. The expanding device complete with frequency heating equipment, rapid and uniform heating of raw materials controllable, uniform propulsion deformed pipes are refined microstructure and mechanical properties of materials to improve the performance guarantee uniformity of the tube to create the conditions, although the device has less investment, short construction period, simple equipment, product quality, high geometric accuracy, finished product rate, etc.
Welding stress elimination
For the high-rise buildings, the component of the residual stress in particular the control of welding residual stresses is quite strict, the welding process of welding residual stress and stress will reduce the capacity and lifetime of the structure, but also the direct cause of cracks caused. After completion of the processing components must adopt appropriate measures to eliminate stress, while the economic costs are very high, the mechanical properties of the component will have a greater damage.
VSR substantive principle is based on mechanical vibration modes impose additional stress on the workpiece, when the additional stress and residual stress superimposed upon the total stress reaches or exceeds a certain value, the stress concentration at the site of more than metallic material yield strength occurs within the workpiece macroscopic and microscopic plastic deformation - Bauschinger effect, thereby reducing the residual stress of the peak point, the stress uniform, improved resistance to deformation of metals. Meanwhile, the dynamic stress and vibration superposition of macroscopic residual stress, combined stress caused yield greater than the elastic limit, the high stress drop, stress uniformity, improved dimensional stability. Particularly in the stress concentration are likely to form a larger tensile stress yield zone, formed after the stress unloading stress protected areas, improve the stability of the structure; early in the VSR effect plays a major role in this.
VSR substantive principle is based on mechanical vibration modes impose additional stress on the workpiece, when the additional stress and residual stress superimposed upon the total stress reaches or exceeds a certain value, the stress concentration at the site of more than metallic material yield strength occurs within the workpiece macroscopic and microscopic plastic deformation - Bauschinger effect, thereby reducing the residual stress of the peak point, the stress uniform, improved resistance to deformation of metals. Meanwhile, the dynamic stress and vibration superposition of macroscopic residual stress, combined stress caused yield greater than the elastic limit, the high stress drop, stress uniformity, improved dimensional stability. Particularly in the stress concentration are likely to form a larger tensile stress yield zone, formed after the stress unloading stress protected areas, improve the stability of the structure; early in the VSR effect plays a major role in this.
Sunday, October 27, 2013
Pipeline corrosion protection measures
At present, domestic and international long- distance pipelines for corrosion-resistant coatings are mainly coal tar enamel, two layer structure of PE, three-layer structure of PE, FBE (FBE), double-layer fusion bonded epoxy powder ( FBE layer ) covering layer.
Coal tar enamel with good insulation properties, low water absorption, corrosion-resistant bacteria and plant roots penetrate the material adequacy and long service life and low price. The main disadvantage is lower mechanical strength, suitable temperature range is narrow, low and easy brittle, production and construction process may escape of toxic gases, requires strict smog measures. Used abroad for more than 70 years of history, in recent years due to environmental restrictions gradually replaced by other coatings. 2 layer PE structure has good insulation properties, low water absorption, high mechanical strength, tough wear-resistant, acid salts and bacteria, corrosion resistance, temperature changes, sufficient material advantages, the price is lower. Drawback is poor resistance to ultraviolet radiation, exposure to sunlight for too long and easy to aging, poor adhesion with steel surface, anti- cathodic stripping poor performance. PE layer electrostatic shielding effect is not conducive impressed current cathodic protection. 3-layer PE anti-corrosion layer structure combines a high-density polyethylene coating, FBE advantages. It is an epoxy powder and firmly with the pipe surface, the use of high density polyethylene resistant to mechanical damage, a special layer between the two layers so that the three molecules bond to form a composite structure, to achieve corrosion properties, good combination of mechanical properties, is currently the leading pipeline engineering preferred coating. FBE (FBE) has a steel surface with a solid, good insulation properties, high mechanical strength, resistance to temperature changes, resistance to chemical corrosion, etc., suitable for a variety of harsh natural environment. The main disadvantage is poor resistance to ultraviolet radiation, since the covering layer is thin, scratch and bump performance is poor. Abroad from the 1960s began to be used pipeline corrosion, has developed rapidly and is currently used on the international pipeline corrosion largest amount of overburden. FBE layer ( layer FBE) and 3-layer PE structure is similar, with good overall performance, high mechanical properties. FJC also with double FBE, good compatibility, cladding surface smooth. In addition, the cathode shielding problems can be avoided with the cathodic protection system matching better than the three-layer structure of PE. It is internationally developed a new kind of coating, the most suitable for use across the mountain section and the stonework.
Coal tar enamel with good insulation properties, low water absorption, corrosion-resistant bacteria and plant roots penetrate the material adequacy and long service life and low price. The main disadvantage is lower mechanical strength, suitable temperature range is narrow, low and easy brittle, production and construction process may escape of toxic gases, requires strict smog measures. Used abroad for more than 70 years of history, in recent years due to environmental restrictions gradually replaced by other coatings. 2 layer PE structure has good insulation properties, low water absorption, high mechanical strength, tough wear-resistant, acid salts and bacteria, corrosion resistance, temperature changes, sufficient material advantages, the price is lower. Drawback is poor resistance to ultraviolet radiation, exposure to sunlight for too long and easy to aging, poor adhesion with steel surface, anti- cathodic stripping poor performance. PE layer electrostatic shielding effect is not conducive impressed current cathodic protection. 3-layer PE anti-corrosion layer structure combines a high-density polyethylene coating, FBE advantages. It is an epoxy powder and firmly with the pipe surface, the use of high density polyethylene resistant to mechanical damage, a special layer between the two layers so that the three molecules bond to form a composite structure, to achieve corrosion properties, good combination of mechanical properties, is currently the leading pipeline engineering preferred coating. FBE (FBE) has a steel surface with a solid, good insulation properties, high mechanical strength, resistance to temperature changes, resistance to chemical corrosion, etc., suitable for a variety of harsh natural environment. The main disadvantage is poor resistance to ultraviolet radiation, since the covering layer is thin, scratch and bump performance is poor. Abroad from the 1960s began to be used pipeline corrosion, has developed rapidly and is currently used on the international pipeline corrosion largest amount of overburden. FBE layer ( layer FBE) and 3-layer PE structure is similar, with good overall performance, high mechanical properties. FJC also with double FBE, good compatibility, cladding surface smooth. In addition, the cathode shielding problems can be avoided with the cathodic protection system matching better than the three-layer structure of PE. It is internationally developed a new kind of coating, the most suitable for use across the mountain section and the stonework.
Buried steel pipeline corrosion factor analysis
Buried pipelines in the working environment, mainly with soil erosion corrosion, bacteria, corrosion and stray current corrosion. Soil is a solid, liquid and gas -phase capillary porous gelatinous body, the soil voids is filled with air and water, the water contains a certain amount of salt, so that the soil has ionic conductivity, soil physical and chemical properties of heterogeneous and metal electrochemical inhomogeneity, constitute electrochemical corrosion of buried pipeline conditions, which will produce soil erosion. In some soil bacteria oxygen ( SRB ) participated in the etching process, the role of bacteria is to participate in the electrode reaction, the soluble iron sulfate to hydrogen sulfide, thus producing bacterial corrosion. Stray current is flowing in the ground outside the protection system design corrosive to metal pipes damaging effects of current. Stray current corrosion including DC and AC stray current corrosion stray current corrosion. DC stray current corrosion principles and electrolytic corrosion similar to AC stray current corrosion is a pipe near high voltage power lines generated by the second induction AC superimposed on the pipeline corrosion corrosion resulting electrochemical cell , the corrosion was smaller, but concentrated corrosion resistance.
Corrosion protection control pipe corrosion damage is a key factor. Currently, the pipeline corrosion protection using a double measures, namely anti-corrosion coating and cathodic protection ( impressed current or sacrificial anode exhaust stream ). Anti-corrosion coating can withstand corrosive environment of the scene to ensure that the pipe firmly bonded, does not appear possible cause cathodic protection cathodic stripping and dead. In the event of partial peeling, you must adjust the impressed current cathodic protection system operating parameters, in order to effectively control the dead corrosion achieve the protective effect. Tube material and manufacturing factors are internal pipeline corrosion, especially steel chemical composition and crystalline structure, high content of non-metallic components ( such as S and P) prone to corrosion, C and Si could easily lead to brittle cracking. Microcrystalline fineness of low-grade, cracks along the grain expansion , prone to cracking. In the manufacturing process, the surface defects ( such as scratches , pits, micro-crack , etc. ), also cause pipe corrosion cracking. Pipeline operation is running, delivery pressure and pressure fluctuations are an important factor in stress corrosion cracking. Excessive pressure to the wall using excessive stress corrosion crack easy to make, easy to make pressure cycle fluctuations crack.
Corrosion protection control pipe corrosion damage is a key factor. Currently, the pipeline corrosion protection using a double measures, namely anti-corrosion coating and cathodic protection ( impressed current or sacrificial anode exhaust stream ). Anti-corrosion coating can withstand corrosive environment of the scene to ensure that the pipe firmly bonded, does not appear possible cause cathodic protection cathodic stripping and dead. In the event of partial peeling, you must adjust the impressed current cathodic protection system operating parameters, in order to effectively control the dead corrosion achieve the protective effect. Tube material and manufacturing factors are internal pipeline corrosion, especially steel chemical composition and crystalline structure, high content of non-metallic components ( such as S and P) prone to corrosion, C and Si could easily lead to brittle cracking. Microcrystalline fineness of low-grade, cracks along the grain expansion , prone to cracking. In the manufacturing process, the surface defects ( such as scratches , pits, micro-crack , etc. ), also cause pipe corrosion cracking. Pipeline operation is running, delivery pressure and pressure fluctuations are an important factor in stress corrosion cracking. Excessive pressure to the wall using excessive stress corrosion crack easy to make, easy to make pressure cycle fluctuations crack.
Friday, October 25, 2013
Development and application of thick wall straight seam steel five-wire submerged arc process
In the thick wall LSAW steel pipe production process, five -wire submerged arc welding process has been a hot research. Currently, only a few countries in the world to master this advanced production technology. Five power wire submerged arc welding using five were arranged longitudinally along the welding wire five separate power supply, the wire solder layer in the pool under a total combustion, enabling the pipe welding. Since more than five arc welding wire, current, pool length, and therefore has a large heat input, high deposition efficiency, metallurgical reaction fully, welding speed, etc. In five wire submerged arc welding process development projects, there is significant electromagnetic interference between AC arc, multi- adjustable parameters, process control and so demanding and difficult. Specifically in the configuration of the welding power source and connection of the wire set spatial position welding parameter selection, the combination of wire diameter and the selection of solder and so on. Where welding power supply configuration, wire spatial position and the welding parameters design choice is the focus of the development process, which is the key technical problems choose reasonable power connections as well as many rational combination of variable parameters.
Introduction of virtual manufacturing technology for non- mandrel -drawn steel production process modeling and simulation, cold drawn steel pipe can operate virtual machines, draft and draft seats, the virtual deformation and bending the material, and for the metal in the deformation process generated in the longitudinal extension and lateral flow causes the inner wall of uneven metal flow problems for the overall coordination and dynamic process optimization; while the material hardness, bending springback, outline size , aspect ratio and other issues simulation. Through this virtual computer model to observe the deformation process of the metal vertical extension and lateral flow, pipe wall thickness changes, and adjust draft and draft seat size, pipe wall thickness of the original with the original diameter ratio, each parameters such as reducing the amount of times, improve product quality.
Introduction of virtual manufacturing technology for non- mandrel -drawn steel production process modeling and simulation, cold drawn steel pipe can operate virtual machines, draft and draft seats, the virtual deformation and bending the material, and for the metal in the deformation process generated in the longitudinal extension and lateral flow causes the inner wall of uneven metal flow problems for the overall coordination and dynamic process optimization; while the material hardness, bending springback, outline size , aspect ratio and other issues simulation. Through this virtual computer model to observe the deformation process of the metal vertical extension and lateral flow, pipe wall thickness changes, and adjust draft and draft seat size, pipe wall thickness of the original with the original diameter ratio, each parameters such as reducing the amount of times, improve product quality.
Thursday, October 24, 2013
High-frequency resistance welding technology
The direct roll formed steel high-frequency resistance welding technology is a rapid production pipeline technology, now in many areas such as: downhole casing, oil and gas gathering and transportation pipe has been widely used. However, this pipe weld area than the base metal and heat affected zone has a higher activity, so the weld zone of the pipe determines the service life. Trench etching is a special pipe joints for crevice corrosion phenomena, usually forming a trench in the weld zone. Under natural conditions, the formation of the trench is easy to make the seam corrosion medium is stagnant state, resulting in dissolved oxygen concentration decreased gradually in the seam and the seam formed outside the oxygen concentration cell, accelerated corrosion of the metal seam. Simultaneously etching the metal ions during the remaining seam, the seam causing Cl- moved, it was immersed in a neutral have been observed within the gap sodium chloride solution, which contains chloride as the main solution 3 to 10 times, with the the corrosion progresses, the corrosion products accumulate in the weld around, such as Fe2 + hydrolysis tends to seam generate excess H +, and the stagnation of the role of making seam metal in the acidic conditions has been reported that the pH can reach 2 to 3, so that the seam metal retainer activation, promote corrosion proceed. When its anodic polarization, the base metal and weld depends on the speed of the electrochemical corrosion activity. Frequency ERW pipe (ERW) if the whole tube without heat treatment, the circumferential weld residual stresses reach 350MPa, close to the yield strength of the pipe. When processed into the working electrode after welding, the residual stress is reduced to 100MPa or less. Circumferential weld tensile stress can reduce the corrosion potential, accelerated corrosion, corrosion susceptibility coefficient increases trench. The product of the pipe after the heat treatment, the residual tensile stress of the circumferential weld small as 10 ~ 100MPa, after processing into the working electrode changes its circumferential tensile stress is not. Such a conventional measurement methods can not characterize pipe products in the practical application of corrosion resistance, can not distinguish between real or not heat-treated for corrosion resistance of welded pipes. However, there is no crevice corrosion under tensile stress reported, this work uses a self-designed fast etching method, studied under constant tensile stress corrosion pipe trench.
Welding process is to produce non-uniform temperature field welding stress and deformation of the underlying causes. Weldment small thickness, the welding residual stress is essentially planar stress, stress is small in the thickness direction. In a free state welding plate, the general vicinity of the weld and the tensile stress, compared away from the weld stress. Residual stress can affect the strength of the weldment, stiffness, stability, accuracy, and corrosion resistance. Elimination of residual stress, the general overall heat treatment. As the annealing temperature is too high will result in material strength and organizational changes or second phase precipitates, the annealing temperature is too low for the removal of little residual stress, and therefore to the stress of the steel 500 ℃ annealing 1h, slow cooling, reducing the welding member of residual stress and improve the homogenization of organization and composition. ERW pipe under the influence of residual stresses in welds susceptible to corrosion, and the greater the degree of residual stress corrosion larger, generally without the entire pipe ERW pipe heat treatment of serious corrosion. 500 ℃ to stress annealing 1h, weld and heat affected zone and base metal corrosion rate close to the same , less prone to corrosion trench.
Welding process is to produce non-uniform temperature field welding stress and deformation of the underlying causes. Weldment small thickness, the welding residual stress is essentially planar stress, stress is small in the thickness direction. In a free state welding plate, the general vicinity of the weld and the tensile stress, compared away from the weld stress. Residual stress can affect the strength of the weldment, stiffness, stability, accuracy, and corrosion resistance. Elimination of residual stress, the general overall heat treatment. As the annealing temperature is too high will result in material strength and organizational changes or second phase precipitates, the annealing temperature is too low for the removal of little residual stress, and therefore to the stress of the steel 500 ℃ annealing 1h, slow cooling, reducing the welding member of residual stress and improve the homogenization of organization and composition. ERW pipe under the influence of residual stresses in welds susceptible to corrosion, and the greater the degree of residual stress corrosion larger, generally without the entire pipe ERW pipe heat treatment of serious corrosion. 500 ℃ to stress annealing 1h, weld and heat affected zone and base metal corrosion rate close to the same , less prone to corrosion trench.
Wednesday, October 23, 2013
Seamless MFL role and evolution of non-destructive testing
Seamless pipe MFL technology is the external magnetic field the ferromagnetic material is magnetized, the material, the outer surface and internal defects in the material surface of the leakage magnetic field, by scanning the sensor surface, the surface defects of Chongqing leakage magnetic alloy tube into the defect signal to determine the defect location and parameters of a non-destructive testing techniques.
Non-destructive testing by detecting magnetic flux leakage is magnetized ferromagnetic surface overflow leakage flux, to determine whether there is defect exists within the material. Since the permeability of the ferromagnetic material is greater than the permeability of other media, most are from the iron magnetic flux inside through. If the ferromagnetic material surface is smooth, uniform, dense interior, no cracks, no inclusions in the material is magnetized, the magnetic material parameters are the same everywhere inside the magnetic field lines all through the internal uniform and dense ferromagnetic material. If the external and internal surface or internal defects, the defect of the magnetoresistive material increases, so the magnetic flux in the magnetic circuit corresponding to distortion: the magnetic flux passes through the defect portion ; another part of the magnetic flux around the defect, through the surrounding ferromagnetic materials; also part of magnetic flux leakage in the outer surface of ferromagnetic material, and then re-enter the material around the defect. This part is called overflow portion distortion flux leakage flux.
Defects in ferromagnetic material forming the outer surface of the space width is inversely proportional to the leakage magnetic field and defects, defect width is smaller, more close to the material near the surface, then the leakage flux Chongqing alloy tube defects greater. The first condition MFL regulated DC magnetization using the method be fully magnetized ferromagnetic material, when the material inside and outside the surface or material defect, the defect inside cut, must outward expansion, this part of the expansion part of the magnetic field lines leaking the workpiece surface, the sensor surface laminating speed scanning, can be detected. Therefore, magnetic flux leakage inspection is the most significant feature of the material, the outer surface and internal defects have a high detection capability.
Segmented perpendicular magnetic sensor group pickup surface defects in material leakage magnetic flux component, to convert it as a defect signal. When the detection speed increases, the signal amplitude increases, the defect signal becomes more acute. Therefore, magnetic flux leakage testing method is a high-speed detection method to detect the faster the higher the signal to noise ratio to obtain a defect is detected, the better. At present, the international community generally detected using magnetic flux leakage testing of ferromagnetic NDT technology pipeline.
Magnetic flux leakage detection technology has emerged on the basis of metal magnetic memory testing technology, Chongqing alloy hell can be effectively applied to in-service equipment early damage detection. The basic principle is: the ferromagnetic material defect or if the defect before the formation of a slight change in the region of the earth magnetic field, will cause changes in the magnetic field, which is called the magnetic memory properties. As the device itself hereditary components, the manufacturing process is the formation of microscopic defects and subsequent operation of the load in the presence of stress, the metal magnetic memory manifested in a cumulative manner, the operation of the load force component magnitude and direction magnetic variation will cause the magnitude and direction changes, the metal member surface leakage magnetic field scan test, can determine the area of stress concentration, and thus indirectly determine the presence of the ferromagnetic member is the possibility of defects. Metal magnetic memory method does not require pretreatment of the surface of the equipment, it can quickly and accurately diagnose the equipment, so as to achieve an early warning device fatigue damage, to facilitate the timely control purposes.
Non-destructive testing by detecting magnetic flux leakage is magnetized ferromagnetic surface overflow leakage flux, to determine whether there is defect exists within the material. Since the permeability of the ferromagnetic material is greater than the permeability of other media, most are from the iron magnetic flux inside through. If the ferromagnetic material surface is smooth, uniform, dense interior, no cracks, no inclusions in the material is magnetized, the magnetic material parameters are the same everywhere inside the magnetic field lines all through the internal uniform and dense ferromagnetic material. If the external and internal surface or internal defects, the defect of the magnetoresistive material increases, so the magnetic flux in the magnetic circuit corresponding to distortion: the magnetic flux passes through the defect portion ; another part of the magnetic flux around the defect, through the surrounding ferromagnetic materials; also part of magnetic flux leakage in the outer surface of ferromagnetic material, and then re-enter the material around the defect. This part is called overflow portion distortion flux leakage flux.
Defects in ferromagnetic material forming the outer surface of the space width is inversely proportional to the leakage magnetic field and defects, defect width is smaller, more close to the material near the surface, then the leakage flux Chongqing alloy tube defects greater. The first condition MFL regulated DC magnetization using the method be fully magnetized ferromagnetic material, when the material inside and outside the surface or material defect, the defect inside cut, must outward expansion, this part of the expansion part of the magnetic field lines leaking the workpiece surface, the sensor surface laminating speed scanning, can be detected. Therefore, magnetic flux leakage inspection is the most significant feature of the material, the outer surface and internal defects have a high detection capability.
Segmented perpendicular magnetic sensor group pickup surface defects in material leakage magnetic flux component, to convert it as a defect signal. When the detection speed increases, the signal amplitude increases, the defect signal becomes more acute. Therefore, magnetic flux leakage testing method is a high-speed detection method to detect the faster the higher the signal to noise ratio to obtain a defect is detected, the better. At present, the international community generally detected using magnetic flux leakage testing of ferromagnetic NDT technology pipeline.
Magnetic flux leakage detection technology has emerged on the basis of metal magnetic memory testing technology, Chongqing alloy hell can be effectively applied to in-service equipment early damage detection. The basic principle is: the ferromagnetic material defect or if the defect before the formation of a slight change in the region of the earth magnetic field, will cause changes in the magnetic field, which is called the magnetic memory properties. As the device itself hereditary components, the manufacturing process is the formation of microscopic defects and subsequent operation of the load in the presence of stress, the metal magnetic memory manifested in a cumulative manner, the operation of the load force component magnitude and direction magnetic variation will cause the magnitude and direction changes, the metal member surface leakage magnetic field scan test, can determine the area of stress concentration, and thus indirectly determine the presence of the ferromagnetic member is the possibility of defects. Metal magnetic memory method does not require pretreatment of the surface of the equipment, it can quickly and accurately diagnose the equipment, so as to achieve an early warning device fatigue damage, to facilitate the timely control purposes.
High pressure seamless steel welding method
Preheat help reduce the carbon steel heat-affected zone of the highest hardness and prevent cold cracking, which is a major carbon steel welding process measures, preheating can improve joint plastic, reducing the welding residual stresses. Typically, high-pressure and high pressure boiler seamless pipe preheating temperature of 150 ~ 250 ℃ then high carbon content or because a large thickness and stiff ness, cracking tendency is large, the preheating temperature can be increased to 250 ~ 400 ℃. If too much solder pieces, the overall preheating of difficulty, can be partially preheated heating locally preheated weld both sides of the range of 150 ~ 200mm.
Welding conditions permit preferred alkaline electrode. Groove forms the weldment try to open a U -shaped groove type welding. If the casting defects, dig out the shape of the groove should be smooth, and its aim is to reduce the molten parent metal into the weld metal in proportion to the reduction in the carbon content of the weld to prevent the cracks.
Welding parameters due to the first layer of molten parent metal weld metal in the proportion of up to 30 %, so the first layer of weld, you should try using a small current, slow welding speed, to reduce the depth of penetration of the base material. Post weld heat treatment after welding, preferably carried out immediately weldment stress relief heat treatment, especially for large thickness of the welded parts, high-rigidity structure part and harsh conditions ( dynamic load or impact load ) working weldment even more so. Stress relief tempering temperature is 600 ~ 650 ℃. If after welding ( ie, when the temperature ≮ 200 ℃ ) can not be stress relief heat treatment, heat treatment should begin immediately ( ie, elimination of hydrogen processing, general heating temperature is about 150 ℃ for 2h slow cooling ).
Welding conditions permit preferred alkaline electrode. Groove forms the weldment try to open a U -shaped groove type welding. If the casting defects, dig out the shape of the groove should be smooth, and its aim is to reduce the molten parent metal into the weld metal in proportion to the reduction in the carbon content of the weld to prevent the cracks.
Welding parameters due to the first layer of molten parent metal weld metal in the proportion of up to 30 %, so the first layer of weld, you should try using a small current, slow welding speed, to reduce the depth of penetration of the base material. Post weld heat treatment after welding, preferably carried out immediately weldment stress relief heat treatment, especially for large thickness of the welded parts, high-rigidity structure part and harsh conditions ( dynamic load or impact load ) working weldment even more so. Stress relief tempering temperature is 600 ~ 650 ℃. If after welding ( ie, when the temperature ≮ 200 ℃ ) can not be stress relief heat treatment, heat treatment should begin immediately ( ie, elimination of hydrogen processing, general heating temperature is about 150 ℃ for 2h slow cooling ).
Monday, October 21, 2013
Straight seam steel pipe breakage
Generally, hydraulic ( pneumatic ) parts in the design using the mechanical properties are assumed material is uniform, continuous, isotropic, According to this method of design that is safe, sometimes accidents fracture accidents.
Straight seam steel pipe(lsaw steel pipe) drawing, since the hot tube defects such as cracks or high-precision drawing after the tank is made, in the course of the fracture occurred, almost no plastic deformation occurs, in general are brittle fracture. Brittle fracture is caused by a variety of reasons. Such as: precipitates on the grain boundaries, regardless of the intensity ratio of the matrix strength strong or weak, are all causes cracks; grain boundary segregation of inclusions also cause fracture; addition, even in far less than the yield limit of the cross- variable loads, can also cause fatigue fracture phenomena.
Found brittle fracture but also with use of components temperature. The study found that people when the temperature drops below a certain temperature, the material will be brittle transition state, the impact absorbed energy decreased, a phenomenon known as cold brittleness, high strength metal materials, low stress occurring in brittle fracture process, the material structure is far from homogeneous and isotropic. Tissues have cracks, there will be inclusions, porosity and other defects, which are a material can be seen in the micro- cracks. Therefore, the design also according to the operating temperature to select members with appropriate cold brittle transition temperature of the material.
Straight seam steel pipe(lsaw steel pipe) drawing, since the hot tube defects such as cracks or high-precision drawing after the tank is made, in the course of the fracture occurred, almost no plastic deformation occurs, in general are brittle fracture. Brittle fracture is caused by a variety of reasons. Such as: precipitates on the grain boundaries, regardless of the intensity ratio of the matrix strength strong or weak, are all causes cracks; grain boundary segregation of inclusions also cause fracture; addition, even in far less than the yield limit of the cross- variable loads, can also cause fatigue fracture phenomena.
Found brittle fracture but also with use of components temperature. The study found that people when the temperature drops below a certain temperature, the material will be brittle transition state, the impact absorbed energy decreased, a phenomenon known as cold brittleness, high strength metal materials, low stress occurring in brittle fracture process, the material structure is far from homogeneous and isotropic. Tissues have cracks, there will be inclusions, porosity and other defects, which are a material can be seen in the micro- cracks. Therefore, the design also according to the operating temperature to select members with appropriate cold brittle transition temperature of the material.
Diameter tolerance of seamless steel pipe
Hot-rolled seamless steel pipe out diameter tolerance with different cold rolled steel after usually not needed for sizing. Therefore, cold rolling steel tube outer diameter of attention is an important indicator of quality. Pipe diameter hole tolerance and wear and rolling machine bouncing value is too large for. If the hole sizing with a serious wear and tear, the tube diameter increases is self-evident. Once the rolling force is too large, it will increase the value of rolling machine bouncing change the size of the roll nip, causing the pipe outside diameter tolerance. The size of the rolling force in addition to the original size of the tube, the metal itself is the size of the deformation resistance, but also with the rolling reduction ( reducing the amount of wall by volume and feed rate ) pipe size and the rolling surface of the tool quality, quality lubricating tube has a close relationship. All measures to reduce the rolling force are conducive to increased tube diameter precision, including the tube annealing; reduce rolling reduction; improve the quality and lubrication tube rolling tools, surface finish, etc. In addition, the use of high strength and hardness of the material to make pipe rolling tool, and to strengthen the rolling tool cooling and inspection, if found rolling tool badly worn, it should be replaced to prevent the pipe diameter tolerance.
Sunday, October 13, 2013
The development of internal and external coating plastic pipe industry
Because plastic pipe inside and outside the performance itself, in the decoration industry has become a plastic pipe is positioned into a new green pipe. In accordance with the relevant departments of the survey data show that both the plastic tube and pipe characteristics of plastic pipe in the next few years to become an emerging force pipe industry . Because from the point of view of domestic manufacturers, plastic pipe or galvanized steel market has become saturated. In the absence of more profits in the case, it is the rapid development of plastic pipe provides an excellent market opportunity. Because of its environmental, home improvement customers now prefer plastic pipe, most of it depends on strong adhesion plastic pipe inner and outer surface after coating, bonding, curing, adhesion large by drop hammer shock and tear, no damage. Second is flame retardant and antistatic products using mine polyethylene coating, the antistatic, flame retardant composition evenly distributed over the surface and inner tubes, in line with MT181 requirements applicable to mine flammable, explosive specific places.
There is corrosion-resistant and easy to scale, at the time of transmission fluid resistance tubing material has a strong acid and alkali resistance and corrosion resistance, suitable for high-sulfur coal mine water and calcium and magnesium ions in water. Because of its high surface finish, the fluid resistance is small, does not adhere to scale, can reduce secondary pollution. Pressure combined with good toughness, high mechanical strength steel to impact, bending and other outside influences, with a strong capacity. But we can not deny that truly promote the development of plastic pipe industry, or in the technical aspects. Because technology is a change in the industry, it can contribute to internal and external plastic pipe from immaturity to become more mature and become more perfect from the imperfect. Whether manufacturers also customers prefer high-quality products, only high-tech in order to create a superior quality product.
There is corrosion-resistant and easy to scale, at the time of transmission fluid resistance tubing material has a strong acid and alkali resistance and corrosion resistance, suitable for high-sulfur coal mine water and calcium and magnesium ions in water. Because of its high surface finish, the fluid resistance is small, does not adhere to scale, can reduce secondary pollution. Pressure combined with good toughness, high mechanical strength steel to impact, bending and other outside influences, with a strong capacity. But we can not deny that truly promote the development of plastic pipe industry, or in the technical aspects. Because technology is a change in the industry, it can contribute to internal and external plastic pipe from immaturity to become more mature and become more perfect from the imperfect. Whether manufacturers also customers prefer high-quality products, only high-tech in order to create a superior quality product.
Improve precision stainless steel tube wear thermal spraying and electroplating method
Thermal spraying is the use of certain heat the coating material is heated to a molten or semi-molten state, and by means of high velocity gas stream and the flame to be atomized and to promote the atomized spray particles to the substrate surface, depositing as having a function of the coating. Thermal spraying can provide surface wear and corrosion resistance, high temperature coating. Coating material usually present between the substrate and the combination of three ways: mechanical bonding, physical bonding, and a metallurgical bond. With the low pressure plasma spraying, high-energy, high velocity plasma spraying, HVOF technology, to further improve the performance of the coating: the porosity can be reduced to 015% to 1%; coating and the substrate bonding strength can reach 70 ~ 140MPa. Studies show that using HVOF (HVOF) and plasma spray technology (ASP) technology, respectively, in 0Cr13Ni5Mo precision stainless steel tube prepared on the substrate of the iron -based amorphous alloy coating and iron-based amorphous and nanocrystalline coatings studied two kind of coating at room temperature friction and wear characteristics, the results showed that the two spraying preparation of iron -based coating have high hardness and low porosity, dense and showed a typical layered structure, improve the wear resistance of the coating.
To compensate for soft precision stainless steel tube does not wear, friction coefficient weakness common plating methods to improve precision stainless steel tube drive shaft with parts of the surface hardness and self- lubricating properties. Precision stainless steel tube is a surface easily passivated metal must be removed before the plating surface passivation film, precision stainless steel tube through to oil, impregnation, activation, and the pre-nickel plating processes, obtained chromium, zinc, copper, tin, precious metals coating. Studies showed that the base metal turbine precision stainless steel tube, and with the periodic inverted earth chrome plating, coating thickness of about 013mm, the coating phase and the rare earth metal-based salt particles of second phase composition, hardness can reach 900 ~ 1000Hv, anti-abrasion coating as a base material of 25 to 28 times, than the original product life of the high precision stainless steel tube 2 to 6 times.
To compensate for soft precision stainless steel tube does not wear, friction coefficient weakness common plating methods to improve precision stainless steel tube drive shaft with parts of the surface hardness and self- lubricating properties. Precision stainless steel tube is a surface easily passivated metal must be removed before the plating surface passivation film, precision stainless steel tube through to oil, impregnation, activation, and the pre-nickel plating processes, obtained chromium, zinc, copper, tin, precious metals coating. Studies showed that the base metal turbine precision stainless steel tube, and with the periodic inverted earth chrome plating, coating thickness of about 013mm, the coating phase and the rare earth metal-based salt particles of second phase composition, hardness can reach 900 ~ 1000Hv, anti-abrasion coating as a base material of 25 to 28 times, than the original product life of the high precision stainless steel tube 2 to 6 times.
Seamless welding procedure tests
According to a different process for seamless pipe production, it is parallel to the longitudinal seam of the steel pipe, welded steel pipe is usually divided into metric, welding thin-walled tube, transformer cooling pipe and so on. Seamless in use with different value and role according to the appropriate method to be used and welding, the welding process used and the type of attention, according to certain production process required for production and processing. Seamless steel pipe with high frequency welding process is relatively simple, fast, continuous production characteristics in the production process is simple and convenient, in accordance with the appropriate production and processing technology. Seamless in civil construction, petrochemical, light industry and other sectors have wide range of applications, used for transporting low-pressure fluid or made into a variety of engineering components and light industrial products, in different industries play an important role and value, to show good properties and performance.
Friction stir welded joints with no pores, fine grain size, fatigue properties, good tensile and flexural properties, welding, no cloud of dust, no splash, energy saving, no wire and shielding gas, welding residual stress and deformation, etc., which is a good applicability soldering method. Cu-Cr alloy has high strength, hardness, good electrical conductivity, thermal conductivity and corrosion resistance, which is the preparation of resistance welding electrodes, metal molds, large high-speed turbine guide bar, power tools, etc. A preferred material for steering. The generator guide bar, electric tools manufacturing process of steering the need for copper-chromium alloys for welding, currently mainly used welding, pressure welding and brazing and other methods. Its physical and chemical properties as well as the copper of impurity elements, which joint prone porosity, strength, corrosion resistance decrease and the welding deformation problems. Currently on friction stir welding of copper -chromium alloy microstructure and properties of welded joints are not many reports, for each pair of solid solution and aging state copper-chromium alloy friction stir welded joint microstructure, hardness and electrical conductivity comparative study of friction stir welding to provide experimental evidence for chromium alloy.
Solid solution of copper -chromium alloy welded joint matrix grain coarse, nugget zone is fine equiaxed grain heat affected zone weld nugget size slightly larger than the area, and there is a certain flow, heat affected zone grain and matrix little difference; weld nugget zone hardness up to 78HB, farther from the weld center lower hardness, hardness until Scientology. Copper-chromium alloy joints aged state matrix structure uneven size equiaxed nugget zone grain refinement, uneven distribution; grain heat affected zone is elongated, with a certain flow resistance; grain heat affected zone than matrix slightly raised; weld nugget zone hardness highest 113HB, the farther away from the center of the weld lower hardness, heat affected zone hardness lowest 91HB, then recovered to the substrate hardness.
Friction stir welded joints with no pores, fine grain size, fatigue properties, good tensile and flexural properties, welding, no cloud of dust, no splash, energy saving, no wire and shielding gas, welding residual stress and deformation, etc., which is a good applicability soldering method. Cu-Cr alloy has high strength, hardness, good electrical conductivity, thermal conductivity and corrosion resistance, which is the preparation of resistance welding electrodes, metal molds, large high-speed turbine guide bar, power tools, etc. A preferred material for steering. The generator guide bar, electric tools manufacturing process of steering the need for copper-chromium alloys for welding, currently mainly used welding, pressure welding and brazing and other methods. Its physical and chemical properties as well as the copper of impurity elements, which joint prone porosity, strength, corrosion resistance decrease and the welding deformation problems. Currently on friction stir welding of copper -chromium alloy microstructure and properties of welded joints are not many reports, for each pair of solid solution and aging state copper-chromium alloy friction stir welded joint microstructure, hardness and electrical conductivity comparative study of friction stir welding to provide experimental evidence for chromium alloy.
Solid solution of copper -chromium alloy welded joint matrix grain coarse, nugget zone is fine equiaxed grain heat affected zone weld nugget size slightly larger than the area, and there is a certain flow, heat affected zone grain and matrix little difference; weld nugget zone hardness up to 78HB, farther from the weld center lower hardness, hardness until Scientology. Copper-chromium alloy joints aged state matrix structure uneven size equiaxed nugget zone grain refinement, uneven distribution; grain heat affected zone is elongated, with a certain flow resistance; grain heat affected zone than matrix slightly raised; weld nugget zone hardness highest 113HB, the farther away from the center of the weld lower hardness, heat affected zone hardness lowest 91HB, then recovered to the substrate hardness.
The oxidation resistance of the welded elbow
Welded elbow will not attack corrosion, pitting, corrosion or wear. Stainless steel construction with a metal timber is still guess one of the highest intensity data. Because the stainless steel has excellent corrosion resistance, it can be permanently linked structural component integrity works envisaged. Chromium welded elbow also set mechanical strength and high delay in one, easy-to -parts manufacturing, construction engineers and structure can meet the needs of persons envisaged. Welded elbow ordinary beam made using seamless, high pressure grade, butt adjoining. Commonly used galvanized iron pipe fittings with Mary ( may cast iron segments ) manufacturing, almost than steel strengths than wrought iron. Its purpose is plain civilian water supply and drainage, the interface can only be threaded adjacent to the pressure grade less than 10kg may 1mpa, ordinary is 7kg. As long as we distinguish the various types of elbow substandard feature, ability to cut the correct use of the elbow to stop substandard substandard task.
Welded elbow to dominate the paint or oxidation-resistant metal ( eg , zinc , nickel and chromium ) to ensure the steel plating rough stop, however, as people know it, this shelter is only a film made for the welding elbow a category not only has a property with elbow as welded elbow also has its own characteristics. Welded elbow during use to show good features and performance characteristics, and fully in accordance with the important criteria parameter. All metals and the oxygen in the atmosphere is stopped reflected in the schematic form an oxide film Disadvantageously, the plain carbon steel iron oxide adhering to the stop formed on oxidation, corrosion inexhaustible expansion, forming holes. Welded elbow refers to all materials and manufacturing style, all interface mode, all the pressure grade elbow ( or other fittings ), include stamping elbow. Welded elbow attention in the course of maintenance and repair, to prevent improper use because some affect its performance operation, affecting the quality of the process model.
Welded elbow to dominate the paint or oxidation-resistant metal ( eg , zinc , nickel and chromium ) to ensure the steel plating rough stop, however, as people know it, this shelter is only a film made for the welding elbow a category not only has a property with elbow as welded elbow also has its own characteristics. Welded elbow during use to show good features and performance characteristics, and fully in accordance with the important criteria parameter. All metals and the oxygen in the atmosphere is stopped reflected in the schematic form an oxide film Disadvantageously, the plain carbon steel iron oxide adhering to the stop formed on oxidation, corrosion inexhaustible expansion, forming holes. Welded elbow refers to all materials and manufacturing style, all interface mode, all the pressure grade elbow ( or other fittings ), include stamping elbow. Welded elbow attention in the course of maintenance and repair, to prevent improper use because some affect its performance operation, affecting the quality of the process model.
Use of the elbow making materials
High elbow wide range of materials, uses widely used, are forming a large-scale high-tech industry group, has a very broad market prospects and extremely important strategic significance.
Production of high pressure elbow requires some special raw materials for production of these materials to conduct rigorous selection and control of raw materials to choose the right, otherwise there would be no production of high quality assurance elbow. High elbow is a category of materials used has a special power, sound, heat, power, chemical, and biological features of the new materials, bio- technology, energy technology and other high-tech fields, and an important foundation for national defense construction material, but also on the transformation Some traditional industries, such as agriculture, chemicals, building materials plays an important role. The material is a special high-pressure elbow, and in some areas show a different value in use, to some extent affect the development of other industries.
High elbow wide range of materials, uses widely used, are forming a large-scale high-tech industry group, has a very broad market prospects and extremely important strategic significance. High elbow material according to different classification criteria can be divided into different categories, because we have a separate electronic information materials as a new class of materials in the field, so the new wear-resistant material referred to here is in addition to electronic information materials outside the main wear-resistant materials.
Production of high pressure elbow requires some special raw materials for production of these materials to conduct rigorous selection and control of raw materials to choose the right, otherwise there would be no production of high quality assurance elbow. High elbow is a category of materials used has a special power, sound, heat, power, chemical, and biological features of the new materials, bio- technology, energy technology and other high-tech fields, and an important foundation for national defense construction material, but also on the transformation Some traditional industries, such as agriculture, chemicals, building materials plays an important role. The material is a special high-pressure elbow, and in some areas show a different value in use, to some extent affect the development of other industries.
High elbow wide range of materials, uses widely used, are forming a large-scale high-tech industry group, has a very broad market prospects and extremely important strategic significance. High elbow material according to different classification criteria can be divided into different categories, because we have a separate electronic information materials as a new class of materials in the field, so the new wear-resistant material referred to here is in addition to electronic information materials outside the main wear-resistant materials.
Thursday, October 10, 2013
Spiral Pipe Welding sulfur segregation
Spiral Pipe sulfur crack (crack caused by sulfur). Sulfur segregation spiral welded steel plates with a strong (especially soft boiling steel) with the segregation of sulfur in the sulfur into the resulting weld metal cracking. The reason is that the melting point of sulfur segregation band containing iron sulfide in the presence of hydrogen and steel. Therefore, in order to prevent this situation generates, uses less sulfur segregation band semi-killed steel or killed steel is also clear efficiency. Secondly, spiral steel pipe weld surface and flux clean and dry is also very necessary. Hot cracking. In submerged arc welding, the weld hot cracking within, particularly in spiral pipe from arcs and arc prone to cracking at the crater. To eliminate this spiral pipe cracks, usually in the arc and arc-quenching plate mounted at, and in the end of the welding coil can be reversed and the spiral welded pipe welded into the stitch welding. Great stress in the weld hot cracking, or when the si weld metal when the most prone to high. Slag involvement. Involved in the welding slag is part remaining in the weld metal welding slag.
Structural steel heat treatment technology
Structural steel workpiece in the heating and cooling process, because the central portion of the cooling surface and the speed and time of inconsistencies, the formation temperature, volume expansion and contraction can lead to uneven stress, the thermal stress. Under the effect of thermal stress, because the surface temperature is below the core part begins, shrinkage core portion by the central portion is greater than the tension, when the end of cooling, since the volume shrinkage of the cooling core section last leaving the surface pressure can not freely central portion tension. That is, in the final thermal stress under the action of the workpiece surface pressure while the heart of tension. This phenomenon is cooled rate, material composition and heat treatment process and other factors. When cooled, the faster, the higher the carbon content and the alloy composition, the cooling process under thermal stress generated in the non-uniform plastic deformation larger, the final form of the residual stress it gets. The other hand, during the heat treatment of steel changes in the organization that the austenite to martensite transition, will be accompanied by an increase in specific volume due to the volume expansion of the workpiece, the workpiece successively all parts of the phase change, resulting in inconsistent grown produce tissue volume stress. The final result of the stress variation is the surface tensile stress, the center of compressive stress, the thermal stress is just the opposite. The size of the stress in the workpiece martensite transformation zone cooling rate, shape, chemical composition and other factors.
Welding temperature of precision light pipe
Precision bright tubes inspection and removal of surface defects, cut into desired length, end to end in the perforated tube surface-centering, and then sent to the furnace heating, punch a hole. In the hole while continuing to rotate and move forward in the roll and the role of the head, gradually formed within the tube cavity, called the capillary. And then sent to the automatic rolling machine to continue rolling. Finally after all the whole entire wall thickness are, after sizing mill sizing, to specifications. Use of continuous pipe mill producing hot-rolled precision light pipe is a more advanced methods. If you wish to get smaller and better quality seamless, must be rolled, drawn or a combination of methods. Cold is usually performed on two-roll mill, pipe hole in the variable section tapered slot and does not move the head of the circular hole formed in the rolling. Drawing is usually 0.5 ~ 100T single chain or double chain drawing machine on.
Heating tube extrusion method is about good squeeze on the closed cylinder, perforated extruded rod rod and move together, so that extrusion from the smaller hole in the extrusion die. This method can produce smaller diameter of the pipe. After coating the coating material on the precision light pipe ri pretreatment indirectly affect the quality of the coating off the power attached to compete. Titanium solid solution strengthening effect is strong, but the toughness of reducing solid solution, solid solution in austenite to improve the hardenability of steel, but titanium compounds, but lower hardenability of steel. Improve the tempering stability, and a secondary hardening effect in enhancing the oxidation resistance and heat resistant steel heat resistance, such as creep and rupture strength, and improve the weldability of steel. Precision light pipe welding temperature is mainly affected by the impact of high-frequency eddy current heating power, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current, and capacitance, inductance. Use of this technology and the production of hot-rolled steel welded pipe common essential difference between the high-frequency furnace heating the weld through the parent microstructure and mechanical properties can be achieved entirely consistent Additionally, multiple passes through the tension -reducing rolling machines and automatic control makes precision light pipe size accuracy ( especially tube roundness and wall thickness accuracy ) than similar. Produced in the developed world, fluid pipes, boiler tubes have been widely used pipe seamless process, with the development of society, domestic hot-rolled precision light pipe welded to gradually replace the situation has been formed.
Heating tube extrusion method is about good squeeze on the closed cylinder, perforated extruded rod rod and move together, so that extrusion from the smaller hole in the extrusion die. This method can produce smaller diameter of the pipe. After coating the coating material on the precision light pipe ri pretreatment indirectly affect the quality of the coating off the power attached to compete. Titanium solid solution strengthening effect is strong, but the toughness of reducing solid solution, solid solution in austenite to improve the hardenability of steel, but titanium compounds, but lower hardenability of steel. Improve the tempering stability, and a secondary hardening effect in enhancing the oxidation resistance and heat resistant steel heat resistance, such as creep and rupture strength, and improve the weldability of steel. Precision light pipe welding temperature is mainly affected by the impact of high-frequency eddy current heating power, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current, and capacitance, inductance. Use of this technology and the production of hot-rolled steel welded pipe common essential difference between the high-frequency furnace heating the weld through the parent microstructure and mechanical properties can be achieved entirely consistent Additionally, multiple passes through the tension -reducing rolling machines and automatic control makes precision light pipe size accuracy ( especially tube roundness and wall thickness accuracy ) than similar. Produced in the developed world, fluid pipes, boiler tubes have been widely used pipe seamless process, with the development of society, domestic hot-rolled precision light pipe welded to gradually replace the situation has been formed.
Diameter pipe connection method and process
Stamping is a good elbow bend in different fields and industries are widely used and promoted, to varying degrees of application and popularization. Stamping elbow is the use of the same material of the plate and pipe with a stamping die stamping into the ring halves elbow, then two half-rings welded elbow for group forming, stamping elbow welding need to follow certain procedures for production and processing. because different types of pipe welding standards, usually in groups to the point of semi- solid factory, on-site construction of the pipe welding seam level, therefore, also known as two half- stamping elbow.
Stamping elbow by means of regular or special processing stamping equipment, power, the plate material in the mold directly affected by the deformation force and the deformation, resulting in a certain shape, size and performance of the product parts production technology, good attention in the processing production techniques. sheets, stamping molds and equipment are the three elements in the production of a good use of time to pay attention and cooperation. stamping is a metal cold deformation processing methods, so called cold stamping or sheet metal stamping, referred to stamping it is metal plastic processing ( or pressure processing ) one of the main methods, also attached to material forming engineering.
Stamping elbow by means of regular or special processing stamping equipment, power, the plate material in the mold directly affected by the deformation force and the deformation, resulting in a certain shape, size and performance of the product parts production technology, good attention in the processing production techniques. sheets, stamping molds and equipment are the three elements in the production of a good use of time to pay attention and cooperation. stamping is a metal cold deformation processing methods, so called cold stamping or sheet metal stamping, referred to stamping it is metal plastic processing ( or pressure processing ) one of the main methods, also attached to material forming engineering.
Monday, October 7, 2013
Longitudinal and spiral welded differences and blasting methods
The main difference between longitudinal and spiral welded pipe lies in the two different production processes, firstly, the formation of longitudinal molding machine is through the first hot rolled coil shape, so that it becomes smooth cylindrical outer surface, and then soldering, welding or the use of a solder layer of the proximity effect of arcing and burning of the skin effect, the edge of the heating tube and melted in a suitable cooled compression molding. LSAW and ERW tube edge is melted in different ways by the distinction, generally called by arc melting LSAW pipe and ERW steel pipe is the use of high-frequency current melted. Spiral welded pipe production process is to follow the appropriate helix angle of the low-carbon low-alloy structural steel and carbon steel coils into the tube, and then seam welded pipe forming. Spiral submerged arc welded pipe is the main form, which can narrow the billet production of large diameter spiral steel pipe is the most significant feature and widely used in all walks of life of the gas pipeline construction.
To reduce the quality of the coating, layer type and construction of environmental factors on the life of the coating Longitudinal should be regularly Longitudinal rust. There are four common rust, namely, pickling, cleaning, descaling and tools rust spray. Pickling is the most common ways of rust, sand-blasting not only can be used as a further treatment step after, but also the Longitudinal surface rust, scale, old coatings completely removed, although this cleaning method make steel surface roughness and cleanliness requirements are up to par, but that is a chemical cleaning method, likely to cause pollution of the surrounding environment. Straight seam steel pipes cleaned only as an adjunct to anti-corrosion treatment, because the steel surface cleaning methods can only dust, grease and lubricants and other residual organics removed, and can not play antiseptic effect, as we usually wash Like, you can clean the surface of the dirt, most bacteria are still left in the hand. Professional and technical personnel with a wire brush and other cleaning tools on the surface to be polished, this approach is known tools rust, loose rust, welding slag and oxide so can be completely removed, but for steel surface firmly attached oxide is powerless and can not achieve the standard preservative effect. Jet is the use of grit blasting, steel shot abrasive materials such as high-quality powerful centrifugal force through the jet to jet straight seam steel surface, not only can effectively remove surface dirt, rust and oxides, etc., will be as abrasive roughness Longitudinal friction and achieve the standard required under the action.
To reduce the quality of the coating, layer type and construction of environmental factors on the life of the coating Longitudinal should be regularly Longitudinal rust. There are four common rust, namely, pickling, cleaning, descaling and tools rust spray. Pickling is the most common ways of rust, sand-blasting not only can be used as a further treatment step after, but also the Longitudinal surface rust, scale, old coatings completely removed, although this cleaning method make steel surface roughness and cleanliness requirements are up to par, but that is a chemical cleaning method, likely to cause pollution of the surrounding environment. Straight seam steel pipes cleaned only as an adjunct to anti-corrosion treatment, because the steel surface cleaning methods can only dust, grease and lubricants and other residual organics removed, and can not play antiseptic effect, as we usually wash Like, you can clean the surface of the dirt, most bacteria are still left in the hand. Professional and technical personnel with a wire brush and other cleaning tools on the surface to be polished, this approach is known tools rust, loose rust, welding slag and oxide so can be completely removed, but for steel surface firmly attached oxide is powerless and can not achieve the standard preservative effect. Jet is the use of grit blasting, steel shot abrasive materials such as high-quality powerful centrifugal force through the jet to jet straight seam steel surface, not only can effectively remove surface dirt, rust and oxides, etc., will be as abrasive roughness Longitudinal friction and achieve the standard required under the action.
Repair of steel pipe welding inernal defect
Pipe internal defects of the weld penetration is not the workpiece and the weld seam between layers of metal or a partial lack of fusion defects. Incomplete penetration welds weakened section of the work, resulting in severe stress concentration and greatly reduce joint strength, it often becomes the root of the weld cracking. Weld slag in the folder with non-metallic slag, which called slag. The weld slag reduces the work section, causing stress concentration, will reduce the strength and toughness of the weld.
Hole weld metal at high temperatures, the absorption of excessive gas ( such as H2) or because of metallurgical reaction solution within the cell gases ( eg CO), cooling and solidifying the molten pool in the time to discharge, and the weld surface of the inside or cavities, is the porosity. The presence of pores reduces the effective working of the weld cross-section, reducing the mechanical strength of the joint. If penetrating holes or continuity exists, it will seriously affect the tightness of the weldment. Cracking during welding or after welding, the welded joint of the metal within the region that appears is called partial rupture cracks. Cracks may occur in the weld, the weld on both sides may also arise in the heat affected zone. Sometimes with the metal surface, sometimes with the metal inside.
Cracks usually follow different mechanisms can be divided into two types of thermal cracking and cold cracking. Hot cracking in the weld metal from a liquid to a solid produced during the crystallization, which result in the weld metal. Its causes are mainly present in the weld low melting substances ( such as FeS, melting point 1193 ℃), it weakens the link between the grains, when subjected to high welding stresses, it is easy to cause the rupture between the grains. Weldments and welding rod containing S, Cu impurities such a long time, it is prone to hot cracking. Hot cracks along the grain boundary characteristics. When the crack through the surface and the outside world, then a clear tendency hydrogenation. Cold crack is generated in the cooling process after welding, most of the base metal or produce the matrix metal and the weld at the junction of the fusion line. Which produces mainly due to the weld heat affected zone or the formation of a hardened structure, high stress, caused by the breakdown of grains, welding high carbon or alloy elements more easily quenched steels, the most prone to cold cracking. Excessive weld melt into hydrogen, can cause cold cracking. Crack is the most dangerous kind of defect, which in addition to reducing the bearing section, the will have serious stress concentration in the use of crack will gradually expand, eventually could lead to component damage. Therefore, there is generally not allowed in welded structures such defects, once discovered to be shoveling heavy welding.
Hole weld metal at high temperatures, the absorption of excessive gas ( such as H2) or because of metallurgical reaction solution within the cell gases ( eg CO), cooling and solidifying the molten pool in the time to discharge, and the weld surface of the inside or cavities, is the porosity. The presence of pores reduces the effective working of the weld cross-section, reducing the mechanical strength of the joint. If penetrating holes or continuity exists, it will seriously affect the tightness of the weldment. Cracking during welding or after welding, the welded joint of the metal within the region that appears is called partial rupture cracks. Cracks may occur in the weld, the weld on both sides may also arise in the heat affected zone. Sometimes with the metal surface, sometimes with the metal inside.
Cracks usually follow different mechanisms can be divided into two types of thermal cracking and cold cracking. Hot cracking in the weld metal from a liquid to a solid produced during the crystallization, which result in the weld metal. Its causes are mainly present in the weld low melting substances ( such as FeS, melting point 1193 ℃), it weakens the link between the grains, when subjected to high welding stresses, it is easy to cause the rupture between the grains. Weldments and welding rod containing S, Cu impurities such a long time, it is prone to hot cracking. Hot cracks along the grain boundary characteristics. When the crack through the surface and the outside world, then a clear tendency hydrogenation. Cold crack is generated in the cooling process after welding, most of the base metal or produce the matrix metal and the weld at the junction of the fusion line. Which produces mainly due to the weld heat affected zone or the formation of a hardened structure, high stress, caused by the breakdown of grains, welding high carbon or alloy elements more easily quenched steels, the most prone to cold cracking. Excessive weld melt into hydrogen, can cause cold cracking. Crack is the most dangerous kind of defect, which in addition to reducing the bearing section, the will have serious stress concentration in the use of crack will gradually expand, eventually could lead to component damage. Therefore, there is generally not allowed in welded structures such defects, once discovered to be shoveling heavy welding.
Wednesday, September 25, 2013
Requirements for strip
Spiral steel pipe used as transport oil, artificial gas, gas, water and some solid materials, pipes and so on. Steel pipe and solid steel bar, etc. compared to the amount of large quantities of pipes for transporting fluids. Flexural torsional strength, lighter weight, an economic cross-section steel, widely used in the construction of structural parts and mechanical parts, such as drill pipe, automotive drive shafts, bicycle frames and construction using steel scaffolding.
Lower carbon content, can reduce the problem of sulfide inclusions, spiral steel pipe for the specific requirements can effectively improve the weldability of steel; reduce the sulfur content in steel to improve the toughness of injection pipe and the arrestability beneficial. Improve crack resistance of steel, while reducing the sulfur content can enhance the quality of steel.
Phosphorus toughness steel strip and weldability of the steel are harmful elements other rare contrast, the spiral steel pipe P also has a strong influence rigid, reducing the phosphorus content can proceed directly weldability, because some hot-rolled steel phosphorus content with better. And an appropriate increase in titanium, vanadium, niobium content. Hot rolled steel strip chemical composition control is important is to reduce the carbon content of parathion. This spiral steel pipe to be qualified.
Lower carbon content, can reduce the problem of sulfide inclusions, spiral steel pipe for the specific requirements can effectively improve the weldability of steel; reduce the sulfur content in steel to improve the toughness of injection pipe and the arrestability beneficial. Improve crack resistance of steel, while reducing the sulfur content can enhance the quality of steel.
Phosphorus toughness steel strip and weldability of the steel are harmful elements other rare contrast, the spiral steel pipe P also has a strong influence rigid, reducing the phosphorus content can proceed directly weldability, because some hot-rolled steel phosphorus content with better. And an appropriate increase in titanium, vanadium, niobium content. Hot rolled steel strip chemical composition control is important is to reduce the carbon content of parathion. This spiral steel pipe to be qualified.
Spiral pipe stress analysis
Spiral pipe of the force is a very complicated situation. Spiral Pipe has affected transmission medium pressure, temperature effects were shed hoop stress generated axial stress; tube bearing capacity of the soil outside the pipe caused by different points along the length of the side asked the uniform settlement for bending sheet cows force; buried by soil pressure pipe above below the top soil by heavy, pipe weight, medium weight reaction force generated by such. Moreover, changes in the soil (plus landslide) external mechanical impact force, but also the pipe is compromised.
Spiral steel pipe inner force is clear. Calculation is simple. Spiral steel pipe outside force is not clear (large random factors), stress analysis is also more complicated. In recent years, although the next few pipeline workers in this area have been studied and published many articles, but still difficult as the design basis. The current practice is to pipe the force generated by the media for the design basis, and left a large degree of safety backup. In the safety in addition to considering the tube on the force generated by external causes, we should also consider the spiral steel pipe (including material and weld) that may arise outside the specified defects in the construction and handling, transportation, F Q, etc. Yim Sang to sodium pipe may damage (scratches, indenting, etc.). Degree of safety is based on the long-term practical experience to determine, issued
by the former Ministry of Petroleum Industry Pipeline design standards, due to internal pressure generated hoop stress control in the range of 0.72 yield limit due to the hoop stress and thermal stress generated when composed of axial stress over the yield limit stress control in 0.9 range. Security too large will result in an increase in capital base construction, low waste Road safety will spiral pipe accident increases. It should be noted that the incident is not caused due to the internal medium, or when the hoop stress occurs in overstressing old (because both have very low limit range), mostly due to an external force and the spiral steel pipe itself and the construction the deficiencies.
Spiral steel pipe inner force is clear. Calculation is simple. Spiral steel pipe outside force is not clear (large random factors), stress analysis is also more complicated. In recent years, although the next few pipeline workers in this area have been studied and published many articles, but still difficult as the design basis. The current practice is to pipe the force generated by the media for the design basis, and left a large degree of safety backup. In the safety in addition to considering the tube on the force generated by external causes, we should also consider the spiral steel pipe (including material and weld) that may arise outside the specified defects in the construction and handling, transportation, F Q, etc. Yim Sang to sodium pipe may damage (scratches, indenting, etc.). Degree of safety is based on the long-term practical experience to determine, issued
by the former Ministry of Petroleum Industry Pipeline design standards, due to internal pressure generated hoop stress control in the range of 0.72 yield limit due to the hoop stress and thermal stress generated when composed of axial stress over the yield limit stress control in 0.9 range. Security too large will result in an increase in capital base construction, low waste Road safety will spiral pipe accident increases. It should be noted that the incident is not caused due to the internal medium, or when the hoop stress occurs in overstressing old (because both have very low limit range), mostly due to an external force and the spiral steel pipe itself and the construction the deficiencies.
Instability spiral steel pipe expansion and crack arrest
Crack instability of disaster research and control. Pair of spiral steel long pipeline is very important. Pressure vessels and factory spiral piping network once the crack, all at once would have been destroyed, it is because the sake of these components is too short, so for them, mainly controlled study initiation and expansion of its instability research seems to crack arrest is pointless. Spiral steel pipe for long-distance pipeline situation is very different, although the initiation of long-distance pipelines for spiral pipe is also very important, a lot of people at home and abroad have done a lot of work, but more important is starting soon unstable propagation of crack after crack can get an early crack than to prevent long break, causing serious damage.
Initiation of the word, in the spiral steel pipe is a long-distance large diameter pipe and spiral steel pipe weld defects, including transport and construction process of the surface damage caused (such as indentations and scratches, etc.) in the pressure test procedure after a period of steady expansion, or in the operating process due to stress corrosion and fatigue fracture propagation (due to pressure fluctuations) and other reasons, the formation - "after the expansion phase stability, resulting in leakage through
cracks in terms of the medium for compression container to control the initiation, is to make the entire life process defects will not reach the critical crack length, the unstable growth will not happen for long-distance pipeline, it is very difficult to do that in fact the current domestic were done outside, this is because spiral pipe some up to hundreds of kilometers and even dry I kilometers long welds, weld too, plus the construction and damage caused during transport, so that string machine undetected surge addition long pipeline is buried, and often is continuously conveyed, in fact, can not be checked throughout the period, due to "leak-before-crack" criteria and regular
observation of the defect etc. Diao; possible so that we can only focus on the spiral pipe crack instability on the crack arrest.
Initiation of the word, in the spiral steel pipe is a long-distance large diameter pipe and spiral steel pipe weld defects, including transport and construction process of the surface damage caused (such as indentations and scratches, etc.) in the pressure test procedure after a period of steady expansion, or in the operating process due to stress corrosion and fatigue fracture propagation (due to pressure fluctuations) and other reasons, the formation - "after the expansion phase stability, resulting in leakage through
cracks in terms of the medium for compression container to control the initiation, is to make the entire life process defects will not reach the critical crack length, the unstable growth will not happen for long-distance pipeline, it is very difficult to do that in fact the current domestic were done outside, this is because spiral pipe some up to hundreds of kilometers and even dry I kilometers long welds, weld too, plus the construction and damage caused during transport, so that string machine undetected surge addition long pipeline is buried, and often is continuously conveyed, in fact, can not be checked throughout the period, due to "leak-before-crack" criteria and regular
observation of the defect etc. Diao; possible so that we can only focus on the spiral pipe crack instability on the crack arrest.
The use of seamless steel pipe
In recent years, in factories, stadiums and other framework from the roofs of buildings, beams, room and pillar of steel tube has been adopted steel pipe because of the tube bending ability. with the development of steel production in the construction, more and more use of steel structure, daily utensils, furniture, water supply and drainage, gas, heating and ventilation, transport and agricultural equipment manufacturing, underground resources such as coal, oil, natural gas development, defense and aerospace used guns, artillery, rockets, missiles, etc. are inseparable from the pipe, so the pipe on the national economy development and people's living standards have a close relationship.
Seamless technical standards is fully seamless performance characteristics, correct and reasonable economic use of seamless services. In the technical standards set forth in the diameter, wall thickness and tolerances, pipe length, bending, end elliptical degrees, delivery weight, markings generally specified range, lists must meet the technical requirements and mechanical properties , process performance, test items and test methods, inspection rules. For some special-purpose seamless pay special attention to some of the requirements specified in the standard requirements. Therefore, the use of seamless process both to understand the user's requirements, but also to meet the technical standards of seamless carbon steel tube.
Seamless technical standards is fully seamless performance characteristics, correct and reasonable economic use of seamless services. In the technical standards set forth in the diameter, wall thickness and tolerances, pipe length, bending, end elliptical degrees, delivery weight, markings generally specified range, lists must meet the technical requirements and mechanical properties , process performance, test items and test methods, inspection rules. For some special-purpose seamless pay special attention to some of the requirements specified in the standard requirements. Therefore, the use of seamless process both to understand the user's requirements, but also to meet the technical standards of seamless carbon steel tube.
Sunday, September 22, 2013
Seamless structural steel heat treatment technology
Seamless steel pipe for structural workpiece in the heating and cooling process, because the central portion of the cooling surface and the speed and time of inconsistencies, the formation temperature, volume expansion and contraction can lead to uneven stress, the thermal stress. Under the effect of thermal stress, because the surface temperature is below the core part begins, shrinkage core portion by the central portion is greater than the tension, when the end of cooling, since the volume shrinkage of the cooling core section last leaving the surface pressure can not freely central portion tension. That is, in the final thermal stress under the action of the workpiece surface pressure while the heart of tension. This phenomenon is cooled rate, material composition and heat treatment process and other factors.
When cooled, the faster, the higher the carbon content and the alloy composition, the cooling process under thermal stress generated in the non-uniform plastic deformation larger, the final form of the residual stress it gets. The other hand, during the heat treatment of steel changes in the organization that the austenite to martensite transition, will be accompanied by an increase in specific volume due to the volume expansion of the workpiece, the workpiece successively all parts of the phase change, resulting in inconsistent grown produce tissue volume stress. The final result of the stress variation is the surface tensile stress, the center of compressive stress, the thermal stress is just the opposite. The size of the stress in the workpiece martensite transformation zone cooling rate, shape, chemical composition and other factors.
When cooled, the faster, the higher the carbon content and the alloy composition, the cooling process under thermal stress generated in the non-uniform plastic deformation larger, the final form of the residual stress it gets. The other hand, during the heat treatment of steel changes in the organization that the austenite to martensite transition, will be accompanied by an increase in specific volume due to the volume expansion of the workpiece, the workpiece successively all parts of the phase change, resulting in inconsistent grown produce tissue volume stress. The final result of the stress variation is the surface tensile stress, the center of compressive stress, the thermal stress is just the opposite. The size of the stress in the workpiece martensite transformation zone cooling rate, shape, chemical composition and other factors.
Friday, September 20, 2013
Methods to improve the wear resistance of stainless steel seamless pipe
To compensate not wear soft stainless steel, the friction coefficient of weakness, commonly used to improve the stainless steel plated with the drive shaft parts of the surface hardness and self-lubricating properties. Stainless steel is a surface easily passivated metal must be removed before the plating surface passivation film, stainless steel through to the oil, dipping, activation, and the pre-nickel plating processes, obtained chromium, zinc, copper, tin, precious metals, and other coatings. Studies show that the stainless steel base metal turbine, using the periodic inverted earth chrome plating, coating thickness of about 013mm, coating a metal matrix phase and a rare earth salt particles composed of a second phase, the hardness can reach 900 ~ 1000Hv, abrasion resistance of the coating the base material 25 to 28 times, than the original product life of stainless seamless steel pipe 2 to 6 times higher.
Thermal spraying is the use of certain heat the coating material is heated to a molten or semi-molten state, and by means of high velocity gas stream and the flame to be atomized and to promote the atomized spray particles to the substrate surface, depositing as having a function of the coating. Thermal spraying can provide surface wear and corrosion resistance, high temperature coating. Coating material usually present between the substrate and the combination of three ways: mechanical bonding, physical bonding, and a metallurgical bond. With the low pressure plasma spraying, high-energy, high velocity plasma spraying, HVOF technology, to further improve the performance of the coating. Porosity can be reduced to 015% to 1%; coating and the substrate bonding strength can reach 70 ~ 140MPa. Studies show that using HVOF (HVOF) and plasma spray technology (ASP) technology, respectively, in 0Cr13Ni5Mo prepared on stainless steel substrate iron-based amorphous alloy coating and iron. Based amorphous and nanocrystalline coatings studied two coating at room temperature friction and wear characteristics, the results showed that the two spraying iron-based coatings are prepared with high hardness and low porosity, dense and showed a typical layered structure, improve the coating wear layer.
Thermal spraying is the use of certain heat the coating material is heated to a molten or semi-molten state, and by means of high velocity gas stream and the flame to be atomized and to promote the atomized spray particles to the substrate surface, depositing as having a function of the coating. Thermal spraying can provide surface wear and corrosion resistance, high temperature coating. Coating material usually present between the substrate and the combination of three ways: mechanical bonding, physical bonding, and a metallurgical bond. With the low pressure plasma spraying, high-energy, high velocity plasma spraying, HVOF technology, to further improve the performance of the coating. Porosity can be reduced to 015% to 1%; coating and the substrate bonding strength can reach 70 ~ 140MPa. Studies show that using HVOF (HVOF) and plasma spray technology (ASP) technology, respectively, in 0Cr13Ni5Mo prepared on stainless steel substrate iron-based amorphous alloy coating and iron. Based amorphous and nanocrystalline coatings studied two coating at room temperature friction and wear characteristics, the results showed that the two spraying iron-based coatings are prepared with high hardness and low porosity, dense and showed a typical layered structure, improve the coating wear layer.
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