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.
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