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.
Wednesday, September 25, 2013
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.
Application of electro-galvanized steel sheet
Household appliances used in the production of traditional steel, electro-galvanized steel mainly. In recent years, with galvanized steel mechanical properties and surface quality continues to improve, with electro-galvanized steel sheet compared to its low production costs, strong corrosion resistance and environmental pollution, etc. become increasingly prominent, and thus with its alternative plating zinc steel appliances at home and abroad has become a major trend in the manufacturing industry. However, from the use of electric appliances with galvanized sheet steel to hot galvanized plate is not a simple substitution process. Among them, how to choose the right materials, it is worth studying.
Appliances with a selection of hot dip galvanized steel mainly related to material grades, coating the surface structure and surface treatment and so on. Appliance parts with specific conditions of use and quality requirements for a reasonable selection, to ensure the quality of home appliances under the premise of reducing material costs, and increase overall competitiveness.
Steel appliances generally stamping with a soft steel, its mechanical properties in accordance with national standards, European standards, the Japanese standard, American standard, etc. to be divided, different standards corresponding to different grades of series. According to the material in the course of processing the degree of deformation, usually steel appliances by stamping level is divided into general use, stamping purposes, uses and ultra deep drawing ( special ) deep drawing uses. Overall, the appliance sheet metal parts stamping difficulty is not too large, but there is a big difference between different parts, so the parts should be based on the deformation mode, deformation characteristics and quality requirements of a reasonable selection of materials. Sheet metal parts stamping appliance that may arise in the main problem is cracking , wrinkling and springback. Because steel stamping defects but also with mold conditions related parts stamping process, a reasonable selection should also consider the user's own mold factors and process factors.
The need for plating appliance parts, use glossy plate, so as to achieve the effect of the light after plating. Appliances are mostly bare plate with ( interior parts ) and painted or foil used ( exterior parts ), you should use matte steel, coating and is conducive to enhancing the binding force between the plates. Meanwhile, the matte side of the beneficial effect of lubricating oil, in order to improve the ability of the material forming. Hot dip galvanized steel in accordance with zinc coating structure, zinc solution to add other elements can be divided into ordinary circumstances hot galvanized plate, zinc alloy of plates, zinc-aluminum alloy coated sheet, aluminum-zinc alloy coated sheet. Different kinds of steel sheets having different characteristics, such as zinc alloy plate weldability, zinc-aluminum alloy plate stamping performance, aluminum-zinc alloy sheet and strong corrosion resistance. At present, the major users of domestic appliances using ordinary galvanized steel (GI), small parts using galvanized (GL) and zinc alloy plate (GA). Ordinary hot- dip galvanized sheet surface state can be divided according to their normal spangle boards, finishing spangle boards, panels and small spangle spangle board, different states steel surface quality, corrosion resistance and paint different results. Zinc galvanized steel sheet thick layer of welded parts prone to injury electrodes, welding is not strong or welding wear phenomenon. Meanwhile, in order to ensure steel within a certain period does not produce red rust on the thickness of the zinc layer has certain requirements.
Galvanized sheet in order to prevent the transport and storage process produces white rust, galvanized sheet surface passivation generally require treatment or oiled. Chromate passivation previously widely used approach has better anti- white rust function, but can not meet the requirements of the EU directive RoHs. Currently, some domestic steel companies successfully developed passivation board can fully meet the EU requirements, to enhance the quality of home appliances to make a contribution. According to user needs, galvanized sheet surface can be thin organic coating, such as fingerprint resistant coating film, anti-fingerprint film helps prevent the production and transportation process residual fingerprints, perspiration and other issues affecting the appearance and surface quality. Plate in order to increase the lubricity of the stamping process, the steel sheet surface to reduce friction and damage the steel sheet can be self- lubricated.
Appliances with a selection of hot dip galvanized steel mainly related to material grades, coating the surface structure and surface treatment and so on. Appliance parts with specific conditions of use and quality requirements for a reasonable selection, to ensure the quality of home appliances under the premise of reducing material costs, and increase overall competitiveness.
Steel appliances generally stamping with a soft steel, its mechanical properties in accordance with national standards, European standards, the Japanese standard, American standard, etc. to be divided, different standards corresponding to different grades of series. According to the material in the course of processing the degree of deformation, usually steel appliances by stamping level is divided into general use, stamping purposes, uses and ultra deep drawing ( special ) deep drawing uses. Overall, the appliance sheet metal parts stamping difficulty is not too large, but there is a big difference between different parts, so the parts should be based on the deformation mode, deformation characteristics and quality requirements of a reasonable selection of materials. Sheet metal parts stamping appliance that may arise in the main problem is cracking , wrinkling and springback. Because steel stamping defects but also with mold conditions related parts stamping process, a reasonable selection should also consider the user's own mold factors and process factors.
The need for plating appliance parts, use glossy plate, so as to achieve the effect of the light after plating. Appliances are mostly bare plate with ( interior parts ) and painted or foil used ( exterior parts ), you should use matte steel, coating and is conducive to enhancing the binding force between the plates. Meanwhile, the matte side of the beneficial effect of lubricating oil, in order to improve the ability of the material forming. Hot dip galvanized steel in accordance with zinc coating structure, zinc solution to add other elements can be divided into ordinary circumstances hot galvanized plate, zinc alloy of plates, zinc-aluminum alloy coated sheet, aluminum-zinc alloy coated sheet. Different kinds of steel sheets having different characteristics, such as zinc alloy plate weldability, zinc-aluminum alloy plate stamping performance, aluminum-zinc alloy sheet and strong corrosion resistance. At present, the major users of domestic appliances using ordinary galvanized steel (GI), small parts using galvanized (GL) and zinc alloy plate (GA). Ordinary hot- dip galvanized sheet surface state can be divided according to their normal spangle boards, finishing spangle boards, panels and small spangle spangle board, different states steel surface quality, corrosion resistance and paint different results. Zinc galvanized steel sheet thick layer of welded parts prone to injury electrodes, welding is not strong or welding wear phenomenon. Meanwhile, in order to ensure steel within a certain period does not produce red rust on the thickness of the zinc layer has certain requirements.
Galvanized sheet in order to prevent the transport and storage process produces white rust, galvanized sheet surface passivation generally require treatment or oiled. Chromate passivation previously widely used approach has better anti- white rust function, but can not meet the requirements of the EU directive RoHs. Currently, some domestic steel companies successfully developed passivation board can fully meet the EU requirements, to enhance the quality of home appliances to make a contribution. According to user needs, galvanized sheet surface can be thin organic coating, such as fingerprint resistant coating film, anti-fingerprint film helps prevent the production and transportation process residual fingerprints, perspiration and other issues affecting the appearance and surface quality. Plate in order to increase the lubricity of the stamping process, the steel sheet surface to reduce friction and damage the steel sheet can be self- lubricated.
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