Successfully won the Middle East pile pipe project

 At the beginning of December 2019, Xinyue received an inqury from customer about pile pipe projects. They need ssaw steel pipe with external coating. After a series of technical confirmation, we received the L/C at the beginning of March. This customer has strict quality requirements.

The client's project is very urgent. In order to meet the delivery date of the client, Tianjin Xinyue purchase raw materials at a high price.At present, the order is in production process smooth, we hope to complete the delivery through the active cooperation of xinyue people.

Every steps of efforts is worthy, it means that we Xinyue is always on our way to build the world, serve the global , and we always try our best to serve every customers.

Xinyue people sincerely look forward to working with you!

http://www.tjxysteel.com/news/Successfully-won-the-Middle-East-pile-pipe-project-946.html

ERW, SSAW, LSAW welded steel tube

    ERW steel pipe: high-frequency straight seam resistance welded pipe, using hot-rolled wide coil as the material, through pre-bending, continuous forming, welding, heat treatment, sizing, straightening, blocking and other processes, it has a shorter weld seam than the spiral, standard High precision, uniform wall thickness, good surface quality, and high-end benefits under pressure, but the defect is that only small and medium-diameter thin-walled pipes can be produced, and the welds are prone to gray spots, unfused, and groove-shaped corrosion defects. At present, the widely used fields are city gas, crude oil products and oil transportation, etc.

    SSAW steel pipe: spiral submerged arc welded pipe, which has a forming angle (adjustable) with the center line of the forming pipe when the pipe is rolled, and is welded while forming, and its welding seam is formed into a spiral line, and the same standard can produce a variety of diameters Standard steel pipe, the material is used to planning larger, the weld can avoid the main stress, the stress is better, the defect is a few standards are poor, the length of the weld is longer than that of the straight pipe, the crack is easy to crack, the slag is included, the welding deviation, etc. Welding defects, welding stress is tensile stress. The general design rules and regulations of long-distance spiral submerged arc for oil and gas pipelines can only be used in category 3 and category 4 areas.

    LSAW steel pipe: Straight seam submerged arc welded pipe, which is made of a single medium-thick plate by pressing (rolling) the steel plate in a mold or forming machine, using double-sided submerged arc welding and expanding the diameter to produce. Its product standard planning is wide, and the resistance, plasticity, uniformity and fineness of the weld are good. It has the advantages of large pipe diameter, pipe wall thickness, high pressure resistance, low temperature resistance and corrosion resistance. When creating high-strength, high-endurance, high-quality long-distance oil and gas pipelines, most of the steel pipes required are large-diameter thick-walled straight-seam submerged arcs. According to API standard rules, in large oil and gas transportation pipelines, when passing through Class 1 and Class 2 areas such as the seabed in high cold areas and densely populated urban areas, the straight-seam submerged arc is the only designated pipe type.

Limitations of SSAW steel tube

　　SSAW steel pipe also has its own shortcomings, spiral steel hollow section is used as a large number of pipeline fluids, such as transportation of oil, natural gas, gas, water and some solid materials, pipes and so on. Compared to other steel and solid steel bar, the same torsional strength in bending, lighter, is an economic cross-section steel, widely used in the manufacture of structural parts and mechanical parts, such as drill pipe, automotive drive shafts, bicycle rack and construction using steel scaffolding.

　　Steel pipe manufacturing annular parts, can improve material utilization, simplify the manufacturing process, saving material and machining time, such as bearing rings, jack sets, has been widely used to make steel. Steel or a variety of conventional weapons indispensable material, barrel, barrel would have to make steel. Pipe according to different cross-sectional shapes can be divided into tube and shaped tubes. Because in the perimeter of equal conditions, the largest area of a circle with a circular tube can carry more fluid. In addition, the circular cross section to withstand internal or external radial pressure, the force is uniform, so the vast majority of pipe is pipe.

　　However, the tube also has some limitations, such as under the conditions by plane bending, tube as good as square, rectangular tube large flexural strength, the skeleton of some farm machinery, steel and wood furniture on the popular square, rectangular tube. According to different uses should also have other special-shaped pipe cross-sectional shape.

Belt And Road impact on steel industry

　　Shinestar Steel Research Institute believes that China's era of rapid economic growth has gone for ever, which makes the steel industry has experienced the middle adjustment pains low growth in the past five years, and future growth continued to slow down will become an indisputable fact.Therefore, the hope of the future development lies in the discovery of new growth momentum of China's economy, growth support points.

　　The layout of the new strategic space needs to be realized through specific economic activities.The infrastructure Belt and Road in the background are beyond the borders, has a broad space for regional infrastructure, China international, along the way will undoubtedly open the human history one of the most magnificent level intercontinental infrastructure construction stage, so large-scale construction will bring a variety of new demand.In Southeast Asia and even greater Eurasian space, China's infrastructure is beginning to show a new development context.If the infrastructure in China's iron and steel, with China's high-speed development, the layout, it needs to how much demand for iron and steel?If China cannot meet the demand for steel who can fill the gap?Does this mean for China's iron and steel, a huge new demand.Shinestar Steel Research Institute believes that the infrastructure is just a part of it, we must rely on infrastructure integration production capacity and transfer, there must be more to promote trade exchanges, including a solid pace of internationalization of the RMB, along the way of opening a new era, brought far beyond our imagination.

　　9.6 million km of land in China,the adjustment of regional economic structure is also in the rapid advance of the steel industry in the study of the market structure of the need to pay attention to this point.Among them, in particular is the integration of the beijing-tianjin-hebei region development.As a key sector of regional development,

　　integration of the beijing-tianjin-hebei region is currently building in Beijing as the starting point of the radial transport system.Such a structure up, how much need to build, how much of the iron and steel, how much investment, will get the number of growth, are obvious.Shinestar steel group last year to put into operation in Tianjin production base, is based in Tianjin, radiation global manufacturing platform, high frequency ERW pipe's production of LSAW pipe, SSAW steel pipe, seamless steel pipe and other quality products, is constantly to meet customer demand.

　　Infrastructure of the formation of the region to accelerate the development of the region's capacity to re layout.Now, we can see the layout of coastal heavy chemical industries include iron and steel, is rapidly formed a pattern in Tangshan, Tianjin as the representative of the heavy, especially the rise of manufacturing industry circle, and Beijing to the two wings extending in the modern industry.These changes in the development of Beijing, Tianjin and Hebei, it means that a non limited prospects, it will undoubtedly bring great demand, these are worth the steel industry to think.

　　The future, shinestar will grasp the macro economic development opportunities, innovative production technology, continue to produce high frequency ERW pipe, LSAW pipe, SSAW steel pipe, seamless steel pipe and other high-quality products, to enhance the market competitiveness of continuous efforts.

Spiral welded pipe production process

　　Spiral welded pipe (some people call it SSAW steel pipe) is also a kind of welded pipe, its strength is generally higher than the LSAW steel pipe. Spiral welded pipe with large diameter can be produced by the narrow blank, and SSAW steel pipe with different diameter can also be produced by the same width of blank. However, compared with the same length of the straight pipe, the weld length increased by 30 to 100%, and the production rate is low. Therefore, the smaller diameter of the pipe mostly use LSAW steel pipe, large diameter welded pipe mostly use spiral welded pipe.

　　The production process of spiral welded pipe

　　Spiral welded pipe is the steel pipe with spiral seam that using the strip coil as raw material, extrusion forming under normal temperature, and using automatic double wire double-sided submerged arc welding process to weld.

　　1.Raw materials are coil, wire, flux. Those must finish the rigorous physical and chemical testing before putting into.

　　2.The head and tail of strip steel butt joint, use single or double wire submerged arc welding, and use automatic submerged arc welding to repair welding after rolled into steel pipe.

　　3.Before forming, the strip will go through the leveling, cutting edge, planing edge, surface cleaning and delivery to the edge of the treatment.

　　4.Using electrical contact pressure gauge control the pressure of the cylinder on both sides of the conveyor to ensure the smooth delivery of the strip.

　　5.Use external control or internal control roll forming.

　　6.Use weld gap control device to ensure that the weld gap to meet the welding requirements, diameter, misalignment and weld gap are strictly controlled.

　　7.Welding and external welding all use American Lincoln welding machine to single or double wire submerged arc weld, in order to obtain a stable welding specifications.

　　8.The welding line after welding must go through on-line continuous ultrasonic automatic injury inspection to ensure that 100% of the spiral weld non-destructive testing coverage. If there are defects, automatic alarm and spray marking, production workers adjust the process parameters at any time, eliminate of defects timely.

　　9.Use air plasma cutting machine to cut a single pipe.

　　10.After cutting into a single steel pipe, the first three of each batch of steel pipe must be carried out a strict first inspection system, to check the weld mechanical properties, chemical composition, melting conditions, steel pipe surface quality and after nondestructive testing to ensure that the pipe process qualified, so it can be put into formal production.

　　11.There are parts marked by ontinuous acoustic flaw on the seam, after manual ultrasound and X-ray review, if there are defects, after repair, again after the nondestructive test until the defect has been confirmed to eliminate.

　　12.The butt welds and helical welds of strip steel where the junction of the Ding-type joints, all through the X-ray TV or film inspection.

　　13.Each pipe must go through the hydrostatic test, the pressure using radial seal. Test pressure and time by the steel pipe hydraulic microcomputer detection device strictly controlled. Test parameters are automatically printed.

　　14.Pipe end machining, so that the vertical face, bevel angle and blunt edge to be accurately controlled.

Causes of trachoma weld formation

　　Spiral Pipe(ssaw steel pipe): by strip by roll forming machine, folding spiral direction, and then double-sided submerged arc welding is made through a capacitor. Spiral welded steel pipe production process, prone to leakage in many cases, such as welding and the wrong side. However, in these cases appear Chlamydia is the most difficult to master spiral steel butt weld.

　　The so-called trachoma: that the welding process on the inside surface of the weld or welds, there has not been a thorough penetration of particles or bubbles, as well as the shape of the sand pit in the surface of the weld. The reason for trachoma are the following:

　　1, the supply of the welding torch during the current is too small, the capacitor is too short, the capacitor has not been completely thorough when welding the welding surface has been hardened, so there occurs a penetration of sand or not bubbles.

　　2, scimitar tune into the strip-shaped curvature of the time there is no good butt, butt strip does not match exactly, there has been too much of a gap between the butt strip.

　　3, butt welded steel when the two sides have not cleared up the edge of the strip rust or scale.

　　4, there is no timely maintenance of production equipment to clean up. Workbench dust or dirt, mistakenly fall into the gap at the butt welding of steel.

　　5, the operating temperature is too low or too wet workshop, which affects the temperature and dryness of welding points.

Welding defects and welding quality of SSAW steel pipe

　　What is the welding qulity of SSAW steel pipe? It is the the degree to which the welding product meets the design technical requirements. Pipe manufacturer usually ensure the welding qulity of SSAW steel pipe by design quality, processing quality, quality inspection, post-weld treatment, etc., since the welding quality not only affects welding products's use performance and life, it also affects personal and property safety.

　　Welding quality usually appears as welding defects, that includes external defects and internal defects. External defects refer to excess height does not meet the requirements, welding tumor, undercut, crater, arc burns, surface pores, surface cracks, welding deformation and warping. Internal defects refer to cracks, not penetration, not fused, slag and porosity.

　　How to prevent the appearance of welding defects to ensure the welding quality?

　　1. Welding method should be suitable for the characteristics of components, and its economical efficiency should be good. The welding process should be able to minimize stress, deformation and stress concentration. Production labor and material consumption should be as small as possible, the convenience of flaw detection should also be taken into consideration when design the joint. The type of joint used in the welding product and its calculated strength should meet the actual carrying capacity.

　　2. The performance of the base metal, wire, flux or welding electrodes and other welding materials those adopted by pipe manufacturer should meet the design requirements. The performance of welder, auxiliary equipment and testing equipment should be good. Before welding, the welding material should be dried according to the provisions, the welding groove of workpiece should meet the requirements and remove the cutting residue, cracks and dirt.

　　3. Pipe manufacturer should carry out quality inspection through the whole production process from design to finished product, we must ensure that the test method used in the quality inspection process is rationality, the reliability of the testing instrument and inspection staff technical level. We should use various inspection methods to test the properties of the joints, physical properties, mechanical properties, microstructure, chemical composition, corrosion resistance, appearance dimensions and welding defects of products after welding.

SSAW steel pipe technology

　　Production process of ssaw steel pipe: based on strip coil as raw material, often warm extrusion molding, automatic double-wire double-sided submerged arc welding process welding spiral seam steel pipe.

　　(1) Raw materials are steel coils, welding wire, and flux. Have to go through rigorous physical and chemical tests before investing.

　　(2) For the butt-end welding of steel strips, single-wire or double-wire submerged arc welding is used, and after the coils are made into steel pipes, automatic submerged arc welding is used to make up the welding.

　　(3) Before forming, the steel strip is leveled, trimmed, edged, surface cleaned and pre-flanged.

　　(4) The electric contact pressure gauge is used to control the pressure of the compression cylinders on both sides of the conveyor to ensure the smooth delivery of the strip.

　　(5) External control or internal control roll forming.

　　(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment, and the weld gap are all strictly controlled.

　　(7) The inner and outer welds are all welded by single-wire or double-wire submerged arc welding using the Lincoln Electric Welder of the United States, thereby obtaining a stable welding specification.

　　(8) Welded welds were all inspected by an online continuous ultrasonic automatic flaw tester to ensure non-destructive testing coverage of 100% spiral welds. If there are defects, they will be automatically alarmed and painted. The production workers will adjust the process parameters at any time to eliminate defects in time.

　　(9) Using an air plasma cutter to cut the steel pipe into single pieces.

　　(10) After cutting into a single steel pipe, a strict first inspection system shall be carried out for each of the first three pipes of each batch to inspect the mechanical properties, chemical composition, fusion condition, surface quality of steel pipes, and non-destructive testing to ensure the pipe-making process. Qualified before they can officially put into production.

　　(11) Where there is a continuous sound wave flaw detection mark on the weld, after manual ultrasonic and X-ray review, if there is a defect, after repair, it shall undergo a non-destructive test again until it is confirmed that the defect has been eliminated.

　　(12) The butt joints of the butt welds and the intersections with the spiral welds of the steel strip are all examined by X-ray television or film.

　　(13) Each pipe is hydrostatically tested and the pressure is radial sealed. The test pressure and time are strictly controlled by the steel pipe hydraulic pressure testing device. Test parameters are automatically printed and recorded.

　　(14) End-of-pipe machining is performed so that the verticality of the end face, the groove angle and the blunt edge are accurately controlled.

LSAW Steel Pipe vs SSAW Steel Pipe

　　1, Difference between lsaw steel pipe and ssaw steel pipe in production process

　　LSAW steel pipe is a longitudinally parallel steel pipe. Usually divided into metric welded steel pipe, welded thin-walled pipe, transformer cooling oil pipe and so on. The straight seam welded pipe has a simple production process, high production efficiency, low cost, and rapid development. SSAW steel pipe is a coiled steel pipe made from strip coils as the raw material, which is often warm extruded and welded by an automatic double wire double-sided submerged arc welding process.

　　The strength of the ssaw steel pipe is generally higher than that of the lsaw steel pipe. A narrower blank can be used to produce a larger diameter pipe, and a blank having a different diameter can be produced from a blank of the same width. During the forming process, the steel plate is uniformly deformed, the residual stress is small, and the surface is free of scratches. The processed spiral steel pipe has greater flexibility in the range of diameters and wall thicknesses, especially in the production of high-grade thick-walled pipes, especially small- and medium-caliber thick-walled pipes, which have unparalleled advantages over other technologies and can satisfy users. More requirements on the specifications of spiral steel pipe. The use of advanced double-sided submerged arc welding technology can achieve welding in the best position. It is not prone to defects such as misalignment, welding deviation and incomplete penetration, and it is easy to control the welding quality. However, compared with the straight seam pipe of the same length, the length of the weld seam increases by 30 to 100%, and the production speed is low.

　　2, Difference between lsaw steel pipe and ssaw steel pipe in security analysis

　　LSAW steel pipe is mainly subjected to residual stress caused by inhomogeneous cooling. Residual stress is the stress of internal self-phase equilibrium under no external force. Hot rolled section steel of various sections has such residual stress. The larger the section size of general steel, the greater the residual stress is. Although the residual stress is self-balanced, it still has certain influence on the performance of steel components under external forces. For example, it may have adverse effects on deformation, stability, and fatigue resistance; after welding, The non-metallic inclusions inside the straight seam steel pipe are pressed into thin slices, and the delamination phenomenon occurs. The delamination weakens the performance of the straight seam steel pipe in the thickness direction, and there is a possibility of interlayer tearing when the weld seam shrinks. The local strain induced by weld shrinkage often reaches several times of the yield point strain, which is much larger than the strain caused by the load. In addition, the lsaw steel pipe will inevitably have many T-welds, so the probability of welding defects is also greatly improved. Moreover, the welding residual stress at the T-weld is large, and the weld metal is often in a three-dimensional stress state, increasing the possibility of cracking.

　　SSAW steel pipe with spiral weld distribution, long weld, especially in the dynamic conditions of welding, the weld is too late to leave the molding point of cooling, easy to produce welding hot cracks. The direction of the crack is parallel to the weld and is at a certain angle to the axis of the steel tube, typically between 30-70°. This angle is just in line with the shear failure angle, so its bending, tensile, compressive and torsional resistance is far inferior to the LSAW pipe. At the same time, due to the limitation of the welding position, the resulting saddle shape and ridge-shaped welding seam influence Beautiful. In addition, during the construction process, the intersecting line welds at the spiral welded parent pipe joints split the spiral joints and generate larger welding stress, which greatly weakens the safety performance of the components. Therefore, the non-destructive testing of the spiral welded pipe joints should be strengthened. Ensure welding quality, otherwise spiral submerged arc welded pipe should not be used in important steel structure occasions.

　　3, Difference between lsaw steel pipe and ssaw steel pipe in the scope of application

　　LSAW pipe adopts double-side submerged arc welding process. Welding under static conditions, the quality of the weld is high, the weld is short, and the probability of defects is very small. The steel pipe expands through full-length, has a good pipe shape, and is precise in size. The steel pipe has a wide wall thickness range and a wide range of pipe diameters. It is suitable for supporting columns, ultra-large span building structures, such as buildings, bridges, dams, and offshore platforms, as well as wind-resistant and earthquake-resistant structures. Pole mast structure. Spiral steel pipe is a kind of steel commonly used in industry, construction and other industries. Mainly used in tap water projects, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction.

　　In summary, we can see that the two different types of welded seam pipes have their own characteristics and have different advantages according to different applications.

Spiral Welded Pipe Production and Use

　　SSAW steel pipe often there will be some quality problems in the production and use, affecting normal use in some aspects, the need for spiral welded pipe to identify the quality, according to a certain way and performance testing, can produce significant in actual use role, then how to identify counterfeit spiral welded pipe method: the appearance often pockmarked face phenomenon. Generally the whole proportionate amount would be better, mainly taking into account the cumulative error and probability theory this problem. Some of the above please add if inadequate, we welcome the discussion of knowledge about aspects of the steel pipe together, advances constantly exchange. Pock is due to badly worn groove spiral welded pipe surface irregularities caused by uneven defects. Because of shoddy spiral welded pipe manufacturers have to pursue profits, rolling groove most often exceeded. The surface is easy to produce scarring.

　　Quality spiral welded pipe of uniform composition. High tonnage cold shear machine, cutting head end surface smooth and tidy, and shoddy materials due to the poor material, cut the first end surface there are often off the meat of the phenomenon that is uneven, and no metallic luster. And because of shoddy materials manufacturers cutting products less head, head and tail will be a big ears. Diameter size fluctuations. Folding is formed on the surface of a variety of spiral welded pipe polyline, this defect is often longitudinally throughout the entire product. Causes folding due to shoddy manufacturers to pursue high efficiency, reduction is too large, resulting in the ears, generated under a rolling folding, the product will crack when folded bending, strength thick spiral welded large decline. Easily scratched.

　　The reason is shoddy material manufacturers poorly equipped, easy to produce burr, scratching the surface of the spiral welded pipe. Depth scratch reduce the intensity of seamless steel pipe. Prone to folding. Transverse ribs thin and low. Often sufficient dissatisfaction with the phenomenon, because manufacturers to achieve large negative tolerance, finished before the reduction of a few relatively large, iron-type small, pass sufficient dissatisfaction. Easy to crack. The reason is that it is blank adobe, adobe many pores, adobe in the cooling process due to thermal stress, cracks, after after rolling there crack.

Raw materials on quality of steel pipe

    There are demands for various steel pipes from seamless steel pipe, ERW steel pipe, galvanized steel pipe as well as SSAW steel pipe in market for transportation of low pressure products like water and high pressure products like oil and gas.

    However, no matter which kind of steel pipe we choose from, we know that raw material would play an important role during the steel pipe’s production process.

    1. From the point of welding, the influence of raw material on quality of ERW steel pipe is mainly reflected in welding and organization of materials.

    2. The composition of the elements in raw material would lead to the impact on intensity, hardness. For example, high content of sulfur and phosphorus in the material can easily cause segregation of crystals. And so does for the impact of high carbon content, too large grain size of the metal structure.

    Once we choose the relevant standards from API 5L, API 5CT, ASTM 53, EN10217, DIN 2458. IS 3589, JIS G3452, BS1387 about ERW steel pipe, it is our responsibility to know their difference before purchasing.

    http://www.xysteelpipe.com/info/Raw-materials-on-quality-of-steel-pipe-937-1.htm

SSAW steel pipe pressure level

    A kind of SSAW steel pipe would include pipe, pipe fittings which conclude elbow, tee joint, taper pipe and so on. Like each kind of SSAW steel pipe has specific standard for it. So does for the pressure grade.

    SSAW steel pipe's grade pressure would be infected by several aspects. First of all, we should consider the pipe components selecting which would be an important factor affecting the grade pressure.

    Secondly, we should make sure the certain pressure, temperature during the whole production process. Thus, the SSAW steel pipe's grade can be controlled by manufacturer.

    In addition, the technological process would be another one factor for it too.

    http://www.xysteelpipe.com/info/SSAW-steel-pipe-pressure-level-895-1.htm

SSAW steel tube wall thickness control

    Spiral Submerged- Arc Welded Steel Pipe (SSAW steel pipe) is used for low pressure liquid delivery, such as water, gas, and oil; construction and piling. And there is a long mark in it so that we should pay high attention to the wall thickness control during the whole production process.

    First of all, pipe heating would be discussed here. Different types and different standard for the steel pipe would have various heating requirements. For SSAW steel pipe, heating to the average is just in order to prevent rapid up and down temperature so that to get the high quality pipes.

    Secondly, original material choosing. We should figure out that average wall thickness of thick wall pipe and solid billet make the probability of mandrel bending deformation significantly reduced, can effectively improve the wall thickness of the precision. So does for the SSAW steel pipe even there is a crack treatment.

    What's more, the perfect production process would another important factor for high quality of SSAW steel pipe.

    http://www.xysteelpipe.com/info/Wall-thickness-control-of-SSAW-steel-pipe-888-1.htm

Effect of Mechanical Expanding of Double Submerged Arc Welding Longitudinal Seam Steel Pipe

    At present, the long-distance transportation of oil and natural gas mainly adopts pipeline. Long-distance pipeline pipeline used in the main spiral pipe submerged arc welded pipe(ssaw steel pipe) and double submerged arc welded straight steel pipe(dsaw steel pipe). As the spiral submerged arc welded pipe is based on strip as raw material, wall thickness is limited, in addition to the existence of spiral submerged arc welded pipe longer, greater residual stress, weld reliability is poor and difficult to overcome the shortcomings of dense population area and reliability requirements of the region, large diameter straight seam submerged arc welded pipe has been gradually replaced by spiral submerged arc welded pipe.

    Expanded diameter is a large diameter straight seam submerged arc welded pipe production to ensure the quality of an important process, the standard pipe line pipe submerged arc welded pipe must be expanded process.

    1, Effectively improve the dimensional accuracy of steel pipe

    At present, there are mainly UO, RB, JCO, C and Hu-Metal for the forming of LSAW steel pipes. The steel pipes produced by these five kinds of molding methods have different geometrical accuracy. As the straight seam submerged arc welding in the tube side of the inside and outside welding, and thus under the action of thermal stress in the steel pipe to be bending deformation, and the longitudinal part of the weld shrinkage larger, so that the straightness of steel pipe is seriously affected; In addition, these five kinds of forming the production of steel pipe, the oval are large, especially JCO and C forming steel pipe. Therefore, we must increase the diameter, the whole circle and other processes to improve the geometric accuracy of steel pipe.

    2, Reduce or eliminate in the pipe, the test process caused by the Bauschinger effect

    As the steel pipe in the process of forming and testing will produce the Bauschinger effect, so that the yield strength decreased, and the expansion of steel in the cold hardened, expanded diameter can improve the yield strength of steel, thus reducing the strength to achieve steel requirements while increasing the level of waste caused by sheet metal.

    3, The elimination of steel pipe forming and welding residual stress

    Cold expansion can eliminate the residual stress caused by forming and welding, and improve the distribution of stress in the steel pipe, so as to avoid the occurrence of hydrogen embrittlement and crack in the steel pipe stress concentration area due to the transportation of H2S in oil or natural gas.

    In addition, the diameter of the welding quality and welding performance is also a good test.