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Stainless steel angle bar is a kind of strip steel with vertical angle on both sides. It can be pided into two kinds: equal side stainless steel angle bar and non equal side stainless steel angle bar. The width of the two sides of the former corner is the same. The stainless steel angle bar can form various force components according to the different needs of the whole structure, and can also be used as the connecting parts among the components. angle bar is simply section non shaped steel. It has good solderability, plastic deformation performance and mechanical strength when used, and the delivery status of finished stainless steel angle bar is hot rolling, normalizing or hot rolling. Its applications are metal components and building frames. The main applications are building structures and engineering structures, such as transmission towers, beams, bridges, ships, industrial furnaces and shelves. The material specification of stainless steel angle can be expressed in terms of the width of the edge, the width of the edge, the thickness of the sides and the number of the models. The model here refers to the centimeter of the side width. Because the type does not represent the different sides and sizes of the same type, so we should fill in the width and side thickness of the stainless steel angle on the contract documents, not by the model alone. At present domestic stainless steel Angle steel specification is 2-20, use the centimeter number of side length as the number, the angle bar of the same number often has 2-7 different sides thick. The imported stainless steel angle bar is usually marked on both sides of the actual size and edge thickness and mark the relevant standards. Usually, the side length is larger than 12.5cm, which is a large stainless steel angle bar. The side length range is 5cm -12.5cm, which is a medium-sized stainless steel angle bar, and the side length is smaller than 5cm, which is a small stainless steel angle bar. The import and export of stainless steel angle orders generally is applied to the required specifications, the corresponding steel to stainless steel. So in addition to stainless steel angle specification number, no specific components and properties of a series of instructions. The appearance quality requirements of stainless steel angle bar are stipulated in the surface quality standard, that is, there are no defects which are harmful to use, such as cracks, lamination and scarring. Source: China Stainless Steel Angle Bar Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In recent years, the rapid development of production technology and equipment technology level of global stainless steel pipe, stainless steel pipe international advanced production features is the use of new equipment, new technology, automatic control and NDT to improve product quality and yield, in the domestic stainless steel welded pipe and seamless steel pipe production technology have also made great progress, but compared with the international advanced level there is a large gap. Below to look at the production technology of several stainless steel pipes. Three step process for steelmaking and continuous casting The production of stainless steel pipe billet by “three step” steelmaking and continuous casting can effectively increase the quality of stainless steel pipe billet and reduce the cost. The process of using electric furnace for melting, MRP – L converter and oxygen gun fast decarbonization, VOD vacuum furnace end deep decarburization, the starting point is that the advantages of AOD and VOD two kinds of production process of the combination of play, can solve the large consumption and processing time for the shortcomings of AOD argon and refractory materials, a short time with the aim of low cost. Hot extrusion process Hot extrusion process is the main production process of hot – working stainless steel seamless steel pipe. With the continuous development of technology, some hot rolled steel pipe sets can produce stainless steel pipes, but the extruding unit is the main production unit of stainless steel seamless steel pipe. Compared with rolling and rolling, it is characterized by three direction compressive stress in the deformation process of stainless steel. In this optimal stress state, the stainless steel pipes with high deformation resistance can obtain a better quality of the internal and external surface and the metallographic structure. Cold rolling production in cold rolling Cold processing stainless steel pipes mainly use cold rolling (cold drawing) combined production technology, cold rolling mills and cold drawn machines develop towards high-speed, high-precision, long journey and multi line. Most of the stainless steel pipes are finished in the form of cold processing. So people pay more attention to cold processing equipment. Cold – drawing, cold rolling, cold – rolling and cold drawing are the three kinds of cold – processing technology. Cold rolling and cold drawing are used in most of the stainless steel pipes. The main and secondary relations are cold rolling and cold drawing. The modern cold rolling mill can also achieve large reducing and large wall reduction, and the deformation of the rolling mill is mainly achieved on the cold rolling mill. Multi line, high speed and full automatic are the better development direction of the current cold drawing machine. Various welding processes The progress of welding technology has speeded up the development of stainless steel welded pipe production, and the application of various welding methods further improved the welding quality and productivity. At present, the main methods for welding stainless steel used in industry are tungsten arc welding, high frequency welding, plasma welding and laser welding. The highest application frequency is argon arc welding and high frequency welding. Light heat treatment process Concerning the heat treatment process of stainless steel pipes, the non oxidation continuous heat treatment furnace with protective gas is widely used abroad for intermediate heat treatment and final product heat treatment. Because of the ability to get no oxidation of the bright surface, in order to eliminate the traditional pickling process. The use of this heat treatment process not only optimizes the quality of the stainless steel pipe, but also solves the problem that the acid cleaning is easy to pollute the environment. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

After the welding operation of stainless steel welded pipe, there are sometimes small defects in the weld area. If it is not found in time and handled well, it is easy to affect the use effect. So how can we check the weld in detail and do not damage the weld? At present, there are five main main methods. Ray flaw detection A nondestructive testing method for inspection of internal defects in welded joints of stainless steel welded pipes using X – ray or gamma ray radiation. It can accurately show the type, size and shape of welding defects in the weld. The flaw in this method of flaw detection is that if long-term operation affects the influence of the operator’s body. Penetrant flaw detection This is the penetration effect of a permeable agent with a fluorescent dye or a red dye to show a nondestructive testing method for small defects on the surface of the welded joint. The surface of the test needs to be smooth and smooth when testing. This method is two kinds of fluorescent flaw detection and coloring flaw detection. The accuracy of fluorescence detection is relatively high, and it can reach up to 10 m. The surface inspection of welded components is often done by coloring method. Eddy current flaw detection Eddy current testing is based on the principle of electromagnetic induction as a basis, when the stainless steel pipe through the AC winding, the stainless steel pipe surface or near the surface will produce skin effect, eddy current when the defective parts will produce change, the winding impedance or induced voltage change, in order to obtain the signal related defects. The defect can be identified from the amplitude and phase of the signal, and the discontinuity defects on the inner and outer surface of the stainless steel pipe can be identified effectively. Magnetic particle flaw detection This is a nondestructive test for the absorption of magnetic powder by leakage magnetic field formed in the surface of a ferromagnetic material in a strong magnetic field. In a place where there is a defect, the effect of magnetic leakage concentrates on the iron powder that is sored. The position and size of the welding defects can be judged according to the shape, thickness and number of the adsorbed iron powder. This method is not suitable for the non magnetic austenitic stainless steel. Ultrasonic examination This method is a nondestructive testing method by using the ultrasonic flaw detector to detect the defects in the weld. This method is suitable for plate flaw detection, and the defects within 5mm can be determined. The detection period is short, the wood is low, the equipment is simple, it is harmless to the operator, but it can not accurately judge the nature of the defect. Source: China Stainless Steel Welded Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are mainly two kinds of stainless steel seamless steel pipes, namely, cold rolling seamless steel pipes and hot-rolled seamless steel pipes. The difference between them is obvious, each has its own advantages and disadvantages. Difference First, the local buckling of materials. The section of cold rolled stainless steel pipe can have local buckling, so as to make better use of the post buckling bearing capacity of pipes, while the section of hot-rolled stainless steel pipes can not have local buckling. Secondly, the difference of the residual stress is different, so the distribution of the cross section is very different. Residual cold-formed stainless steel on the stress distribution of bending type, and the residual hot rolled steel section stress distribution on the performance of thin film. In addition, the free torsion stiffness of the hot rolled stainless steel pipe is higher than that of the cold rolled steel, so the torsional resistance of the hot rolled stainless steel pipe is better than that of the cold rolled stainless steel pipe. Advantages and disadvantages The cold rolled seamless steel pipe is made of stainless steel plate or under cold drawing, cold bending, cold drawing and other cold drawing process under the condition of normal temperature. The utility model has the advantages of fast forming speed, high yield, and will not damage the surface coating, can be made into a variety of styles section, which can well meet the various needs of cold rolled stainless steel materials; also can let the formation of plastic deformation, so as to improve the material yield point. There are three main shortcomings. One is that although there is no hot plastic compression in the forming process, there will still be residual stresses in the section, which will inevitably affect the overall and local buckling characteristics of stainless steel. The other is the style of cold rolled stainless steel is usually the open section, resulting in the lower free torsion stiffness of the section, which is prone to torsion when bending, and it is prone to bending torsion buckling when it is subjected to compression, and the torsion resistance is weak. The third is that the cold rolled stainless steel has low wall thickness and is not thickened at the corner of stainless steel plate joining, resulting in poor performance of local concentrated load. Compared with hot-rolled seamless steel pipes, cold rolled seamless steel pipes are rolled under the recrystallization temperature of materials, while hot-rolled seamless steel pipes are rolled on the recrystallization temperature. The advantage is that it can refine the microstructure of stainless steel, destroy the casting structure of the ingot, and remove the microstructural defects, make the steel structure more dense and improve its mechanical properties. This improvement is mainly along the rolling direction, so that the stainless steel material is not isotropic to a certain extent, bubbles, cracks and loose in the previous pouring, will be welded by effect of high temperature and pressure. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Because the yield point of the stainless steel plate material itself is relatively high, the hardness is also very large, and the effect when performing the cold hardening is very obvious, so when the stainless steel plate is bent, the characteristics are very significant, mainly reflected in four aspects. The first reason is that the thermal conductivity of stainless steel sheet is weaker than ordinary low-carbon steel, and its elongation is also low, so it requires a large deformation force when bending; secondly, the springback tends to be large when the stainless steel sheet material is bent. In carbon steel, stainless steel plate has a smaller elongation than carbon steel, and the bending angle of the plate is also greater than that of carbon steel during bending. If it is too small, cracks may occur. In addition, the stainless steel plate is hard and cold. Hardening effect is obviously affected, so the tool steel with heat treatment hardness above 60HRC should be selected when selecting the bending tools. The surface roughness of such materials is higher than that of carbon steel bending tools by an order of magnitude. According to the above-mentioned characteristics of the stainless steel plate, normally, the thicker the stainless steel plate is, the larger the required bending force is, and the thickness of the stainless steel plate is increased. The margin of bending force that should be taken into account should also be higher; Second, under the unit size, the higher the tensile strength of the stainless steel sheet, the lower the elongation, the greater the required bending force, and the greater the bending angle. In the design drawing, the thickness of the stainless steel plate and the bending radius correspond to each other. According to experience, the bending dimension of a piece of stainless steel plate that is bent is the addition of two plate thicknesses at right angles, which can fully satisfy the accuracy of the design. Requirements, based on experience, the formula to calculate the amount of expansion can simplify the calculation process, which can greatly enhance the production efficiency; The higher the yield strength of the stainless steel plate material is, the greater the elastic recovery amount is, and the smaller the angle of the press blade required to obtain the angle of 90 degrees of the bent stainless steel plate is, the smaller the design should be. Relatively speaking, the stainless steel plate with the same thickness as the carbon steel plate will have a larger bending angle. In this regard, it is particularly necessary to pay attention to it, otherwise, it will be easy to form a pressure cracking crack, which affects the strength of the stainless steel plate. Source: China Stainless Steel Plate Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are many production processes for stainless steel pipes, and the finished products are bundled very neatly, and the surface of stainless steel pipes are also very beautiful. How does the manufacturing process the surface of the stainless steel pipe during production? When producing stainless steel pipes, it is necessary to pay attention to all aspects. The grinding and surface machining of stainless steel pipes requires careful and careful attention. With the wider use of stainless steel pipes, more manufacturers will have larger orders, they must not be careless, and they must handle the surface of stainless steel pipes. Speaking of the surface treatment of stainless steel pipe, the first thing to mention is the grinding process, which is part of the polishing process. In fact, there are many tricks in the surface treatment of such stainless steel pipes. If there are defects on the surface of the stainless steel pipe, it is necessary to grind it manually at this time, and then make a decision on the bar. Stainless steel pipes have now been effectively applied to many fields, and their chemical properties are different from those of other stainless steel materials. For surface treatment of stainless steel pipes, the workpiece must be inspected in all directions. If quality is found to be unacceptable, such as incomplete mating, uneven solder joint depth, etc., it is best to rework until stainless steel pipe work is confirmed to be defective. Polished. In the process of sanding the stainless steel pipe, it is necessary to carefully remove the solder joints and scratches left by the welding, so that the surface treatment is clean. There are two types of grinding: rough grinding and fine grinding. After grinding, the workpiece surface of stainless steel pipe will be very bright, and can completely eliminate the traces of the joints. After polishing, the stainless steel pipework should exhibit a mirror-like effect. Polishing is also a process for treating the surface of a stainless steel pipe. There are generally three methods, namely, mechanical polishing, chemical polishing, and electrochemical polishing. Mechanical polishing is particularly suitable for large-size polishing, where small parts are difficult to achieve very good results and are suitable for batch production. The advantage of this method is that it can perform surface treatment very well. However, its disadvantages are high investment costs, relatively large labor intensity, and serious pollution problems. Therefore, many manufacturers are not optimistic about this. Chemical polishing is the same, its cost is low, there is no need to use large-scale mechanical equipment, the investment is flexible, and the polishing speed is very fast, but the disadvantage is that the brightness of the polishing is not good enough. The process of electrochemical polishing method is more stable, it is easy to operate, and the investment cost is lower, and the pollution is also small. Generally, once a one-time investment is no longer necessary, the cost is now used by most companies. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Before the stainless steel pipe enters the pickling and passivation process, corresponding pretreatment work must be done so as to obtain a stainless steel pipe surface that meets expectations after the pickling and passivation process. Pretreatment work mainly includes the following aspects. The first is based on pre-written drawings and the requirements of the process documents, after the completion of the production of stainless steel pipe inspection of the specified project to ensure that the relevant standards are qualified. Followed by clean welding seams and spatter and spatter on both sides. When removing foreign materials on both sides of the weld, use a stainless steel wire brush or grinding wheel to remove; the surface of the machined parts of the stainless steel pipe should be cleaned with gasoline or detergent. If you remove grease, dirt, etc., if the oil is severe enough to be removed with a suitable alkaline solution, it is important to note that after both removals are completed, rinse with clean water with a chloride ion content of less than 0.5%. Mechanical sandblasting can be used to remove oxide scale from stainless steel hot work parts, where the sand must be pure silicon or alumina. Finally, it is necessary to formulate a good pickling and passivation safety measure and determine suitable labor and protective equipment. Pickling and passivation can be used for the overall treatment of smaller, unprocessed parts. When the temperature of the solution is in the range of 21-60°C, it should be checked every 10 minutes until a uniform white acid etching finish is exhibited. Pickling using pickling pastes is mainly suitable for the local treatment of large pipes or components. The treatment method is to evenly apply the pickling paste to the clean equipment at room temperature, apply a thickness of about 2-3mm or so, and then use a clean water or stainless steel wire to gently brush until it shows an even white acid etch. The finish is only finished. The passivation solution is mainly suitable for use in the overall treatment of small tubes or components. It can be immersed or sprayed. When the solution temperature is 48-60°C, it should be checked every 20 minutes when the solution is at 21-47°C. At that time, it needs to be checked once every hour until the surface forms a uniform passivation film. The passivation paste is also mainly applied to large-scale pipe fittings or localized treatment. The passivation paste is evenly coated on the surface of the acid-washed stainless steel tube at room temperature. After 1 hour, it needs to be inspected until a uniform passivation film is formed on the surface. . Pickling passivated tubes or components must be cleaned with clean water, and then use acidic litmus paper to detect all areas of the flushing surface. The requirement is to maintain the pH in the range of 6.5-7.5, then wipe clean or use compression The air is blown dry. Pickling and passivating stainless steel pipes cannot be bumped and scratched during handling and lifting to prevent damage to the passivation film. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In the process of processing stainless steel pipes, the surface of the pipes will always produce yellow or black oxide scales, which are not only beautiful but also seriously affect the corrosion resistance during use. In order to solve these problems, the stainless steel pipe must be processed after the corresponding acid Wash passivation treatment. The purpose of pickling and passivation is to remove the oxide scale generated after welding, high temperature treatment and other processing steps, so that the surface of the stainless steel tube restores its original silver luster, and a layer of chromium is also formed on the surface of the treated stainless steel tube. The oxide film of the material can prevent the stainless steel tube from being corroded by oxidation again so as to achieve the purpose of passivation. This can enhance the corrosion resistance of the surface of the stainless steel product and prolong the service life of the stainless steel tube equipment in disguise. From the effect of the above passivation, the corrosion resistance of stainless steel is mainly due to the fact that the surface is covered with a dense passivation film with a thickness of 1-15 nm. This film can completely separate the corrosive medium and is protected by stainless steel tubes. The basic barrier to external corrosion. In addition, the passivation film of stainless steel has obvious dynamic characteristics, because corrosion is a dynamic process that changes constantly, and the passivation film also forms a continuously spreading barrier, which greatly reduces the degree of anode reaction. Generally, in the case of external reducing agents (for example, chloride ions), the film tends to be destroyed, and in the presence of an oxidizing agent (such as air), the film is constantly maintained and repaired. The passivation treatment of stainless steel tubes is generally thoroughly cleaned first, which includes both alkali washing and pickling, and then passivation using an oxidant, so that it is possible to ensure good integrity and stability of the passivation film. One purpose of pickling is to create the right conditions for the passivation process and ensure the formation of a good passivation film. Since the surface of the stainless steel plate is corroded by an average of 10 μm thick on the surface of the stainless steel, the chemical activity of the acid solution causes the dissolution rate of the defect site to be higher than that of the normal surface. Therefore, the pickling process can cause the entire surface of the stainless steel pipe to be inclined. It is evenly balanced and some of the hidden dangers that are likely to cause corrosion are also removed. But more critical is that passivation by pickling will make the oxides of iron and iron preferentially dissolve away from the oxides of chromium and chromium. The removal of chromium-depleted layers will lead to the enrichment of chromium on the surface of stainless steel tubes. The potential of the chromium-rich passive film can reach +1.0V (SCE), which is close to the noble metal’s potential, which enhances the stability of corrosion resistance. Different passivation processes affect the composition and structure of the passivation film, which affects the stainless properties of the material. If the electrochemical modification treatment is used, the passivation film can be provided with a multilayer structure, and chromium trioxide can be formed on the barrier layer. Or chromium trioxide may also generate a glassy oxide film. From this point of view, the corrosion resistance of the stainless steel tube can be fully utilized. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

During the welding process of stainless steel pipes, cracks sometimes occur in the weld zone. According to the time and temperature of formation, there are mainly three forms of cold cracks, hot cracks and reheat cracks; according to the formation site, it can be pided into vertical cracks, transverse cracks, Weld root cracks, arc pit cracks, fusion line cracks, and heat affected zone cracks. This kind of defect is the most dangerous for the welded structure. Not only is it easy to scrap the stainless steel pipe, it may also cause serious accidents. Hot crack In the welding process, the welding crack formed by the stainless steel material in the weld zone and the heat affected zone cooled to the high temperature zone near the solid line is called a hot crack, and the danger is high. The main reason is that the low-melting eutectic and impurity in the molten pool metal produce severe intragranular and intergranular segregation during the crystallization process. At the same time, it is pulled along the grain boundary under the action of welding stress to generate hot cracks. Hot cracks usually occur in austenitic stainless steels, nickel alloys, and aluminum alloys. The solution is to strictly control the content of sulfur, phosphorus and other harmful impurities in stainless steel pipes and welding consumables, reduce the sensitivity of hot cracks, or adjust the chemical composition of the weld metal, optimize the weld microstructure, refine the grain, Strengthen plasticity and reduce segregation; also use alkaline welding materials, reduce the content of impurities in the weld, optimize the degree of segregation; select suitable welding process parameters, properly increase the weld forming factor, use multi-layer multi-channel welding Method: When the arc is broken, use the same lead plate as the parent material, or gradually extinguish the arc and fill the arc pit to prevent the formation of hot cracks in the arc pit. Cold crack Cold cracking refers to the formation of cracks when welded joints of stainless steel tubes cool to lower temperatures. This kind of defect may occur immediately after welding, or it may occur within a few hours, so it is also called delayed crack. It has high universality and greater danger. There are three main reasons for formation, namely hardened structure formed by martensitic transformation, welding residual stress formed by a large degree of binding, and hydrogen remaining in the weld. The solution is to use low-hydrogen type welding materials; to remove the oil and moisture on the weldment and reduce the hydrogen content in the weld before welding; to select suitable welding process parameters and heat input to reduce the hardenability tendency of the weld; after welding Hydrogen treatment is immediately required to allow hydrogen to escape from the welded joint. For stainless steel welded tubes with a high tendency to harden, preheating before welding and heat treatment in time after welding will improve the microstructure and properties of the joint. Reheat crack After welding, cracks formed when the stainless steel tube is heated again in the corresponding temperature range are called reheat cracks. The reason for this is that reheat cracking usually occurs in low-alloy high-strength steels, pearlitic heat-resistant steels, and stainless steels containing vanadium, chromium, molybdenum, boron, and other alloying elements. After being subjected to a welding heat cycle, it is heated to sensitive areas. form. Most cracks originate from the coarse-grained region of the heat-affected zone of the weld. Most of the reheat cracks are formed in the stainless steel welded pipe and in the stress concentration area, and the reheat cracks are sometimes formed in the multilayer welding. The solution is to meet the design requirements, select the lower strength of the welding material, making the weld strength weaker than the parent material, the stress relaxation in the weld to prevent the formation of cracks in the heat affected zone; minimize the welding residual stress and stress Concentrate; control welding pipe heat input, reasonable choice of preheating and heat treatment temperature, try to avoid sensitive areas. The degree of risk of cracks is very high, especially the practical application and yield of stainless steel welded pipe products will be seriously affected. Therefore, such defects must be avoided as much as possible, and corresponding compensations should be made after the occurrence. If they cannot be compensated, they cannot be used in practical applications. Source: China Stainless Steel Welded Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In the welding process of stainless steel pipes, some defects may cause stress concentration, bearing capacity, shortened service life, and may even cause brittle fracture. Usually in the welding technical regulations, it is absolutely impossible for cracks, incomplete penetration, unfused, and surface slag inclusions; defects such as undercuts, internal slag inclusions, and pores must not be larger than the allowable value; And welding. Here are the reasons for the formation of several common stainless steel welding defects, hazards and solutions. Weld size not up to standard This kind of defect mainly refers to the weld residual height and residual height difference, the weld width and width difference, the amount of misalignment, the amount of deformation after welding does not meet the standard size, the weld is uneven, uneven width, deformation Great. Inconsistent weld widths, in addition to the unsightly appearance of welds, can also affect the bond strength between the weld and the base metal. Excessive weld seam height is too high to cause stress concentration. The weld seam is lower than the base metal and the joint strength will be Insufficient; wrong side and deformation is too large, will make the transmission force distortion and stress concentration, resulting in reduced strength. There are three reasons for the formation. One is the improper welding angle of the stainless steel pipe or the unevenness of the blunt edge and the assembly gap. The second is the unreasonable choice of the welding process parameters. The third is the low level of the welder’s operation skills. The solution is to choose the proper groove angle and assembly clearance; to enhance the assembly quality; to select suitable welding process parameters and to improve the operating technology level. Undercut defects Because the welding process parameters are not selected correctly or the operation process is not correct, the grooves or depressions that are easily formed by melting along the base material of the weld toe are called undercuts. Undercutting not only weakens the strength of welded joints in stainless steel pipes, but also causes cracks due to stress concentration. The reasons for the formation of the main current is too large, the arc is too long, the electrode angle is not correct, improper method of transport and so on. The solution is to choose the right welding current and welding speed during the arc welding of the electrode. The arc cannot be pulled too long. The angle of the welding rod must be correct and the method of transport should be accurate. Incomplete defect Incomplete penetration refers to the situation where the root of the welded joint does not completely penetrate the stainless steel pipe during welding. No penetration will lead to stress concentration and easily lead to cracks. Important weld joints may not have incomplete penetration defects. The reason for this is that the groove angle or gap is too small, the blunt edge is too large, the assembly is poor, the welding process parameters are not properly selected, the welding current is too small, the welding speed is too fast, and the welder has poor operation techniques. The solution is to correctly select and process the groove size, reasonably assemble, ensure clearance, select the appropriate welding current and welding speed, and improve the welder’s operating technology level. Unfused defect Non-fused refers to the portion that is not completely melt-bonded between the weld bead and the base metal or between the weld bead and the weld bead during welding. The lack of fusion directly reduces the mechanical properties of the welded joints of the stainless steel pipe. Severe non-fusing causes the welded structure to be completely unsupported. The reason is that the speed of welding stainless steel pipe is fast and the welding current is too low, the welding heat input is too low; the electrode is eccentric, the angle between the welding rod and the weldment is improper, and the arc points to the deflection; the rust and dirt on the side wall of the groove are formed; Slag is not completely clear. The solution is to correctly select the welding process parameters, perform the operation carefully, and clean up the layers. Weld A weld bead refers to a metal tumor that melts on the unmelted parent metal outside the weld during the welding process. The weldment not only affects the formation of the welds in the stainless steel tubes. In the area of the welds, there are usually slag inclusions and incomplete penetrations. The reason for the formation is that the blunt edge is too small and the root gap is too large; the welding current is large and the welding speed is fast; the welder has a low level of operational skills. The solution is to select appropriate welding process parameters according to different welding positions and strictly control the size of the fusion hole. Crater The crater refers to the depressed portion of the stainless steel tube formed at the end of the weld. The craters not only severely weaken the welds at the site, but also cause crater cracks due to the concentration of impurities. The main reasons for the formation are the short arc extinguishing residence time and the excessive current during the thin plate welding. The solution is that when the arc welding of the electrode arcs, the electrode must stay at the pool for a short time or make a circular transport bar. After the molten metal is filled, the arc extinguishes to one side. When the tungsten electrode is welded, there must be enough. The residence time, after filling the weld attenuation arc extinguishing. Stoma When the stainless steel pipe is welded, voids generated due to the gas in the molten pool not being able to escape during solidification are called pores. The pore is a kind of common welding defect, which is pided into two kinds, the inner pore and the outer pore of the weld. The pores are mainly round, oval, insect-shaped, needle-shaped, and dense-shaped. The existence of pores not only affects the tightness of the weld, but also reduces the effective area of the weld and weakens the relevant mechanical properties of the weld. The main causes are the presence of oil, rust, moisture, and other contaminants on the surface and groove of the stainless steel pipe; when the electrode is arc welded, the coating of the electrode is damp, and there is no drying before use; the arc is too long or partial blow; the effect of the molten pool protection Not good, the air invades the molten pool; the welding current is too large, the welding rod becomes red, the coating peels off prematurely, and the protection function is lost; the operation method is improper, such as the arc closing movement is too fast, the shrinkage hole is easy to occur, and the arc welding action of the joint is incorrect. It is easy to form dense pores. The solution is to remove the dirt in the 20-30mm range on both sides of the clean groove before welding; strictly according to the temperature and time specified in the electrode specification; select the correct welding process parameters and operate correctly; use short-arc welding as much as possible, There must be windproof facilities in the field construction; failure to use the welding rod. Inclusion and slag inclusion Inclusion refers to non-metallic inclusions and oxides formed by metallurgical reactions that remain in the weld metal. Slag inclusions are slag that remains in the weld. Stainless steel welded pipe slag is mainly pided into slag inclusions and strip inclusions. Slag inclusion weakens the effective section of the weld to reduce the mechanical properties of the weld. Slag inclusions also tend to cause stress concentration, which can easily damage the welded structure during loading. The reason for the formation is that the inter-layer slag is not clean during the welding process, the welding current is too low, the welding speed is too fast, and the welding operation is not performed properly; the chemical composition of the welding material and the parent metal are not properly matched; the groove design and processing are not suitable, etc. . The solution is to select the electrode with better slag removal performance; carefully remove the inter-layer slag; reasonably select the welding process parameters; adjust the angle of the electrode and the method of transport. Burn through The burn-through defect refers to the defect that the stainless steel pipe is perforated when the stainless steel pipe is welded and the molten metal flows out from the back of the groove. This is a relatively common arc welding defect. The reason for this is that the current during welding is too large and the welding speed is too slow, causing the stainless steel tube to be overheated; the groove gap is large and the blunt edge is too thin. The solution is to select suitable welding process parameters and suitable groove sizes, and in addition, the welding operation level should be as high as possible. Source: China Stainless Steel Welded Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The finished stainless steel pipes, unless used under deep underground conditions, need to be polished to ensure that the surface is bright and beautiful. Currently used polishing methods mainly include mechanical polishing, chemical polishing, and electrochemical polishing. Mechanical polishing The mechanical polishing method employs a polishing wheel or a polishing belt for processing, wherein the polishing belt performs abrasive polishing processing on the surface of the stainless steel tube with the abrasive in the polishing agent to promote the smooth polishing effect of the stainless steel tube surface. Mechanical polishing can obtain a mirror shiny surface of less than 0.4 μm. Simple-shaped parts can use hard polishing wheels or polishing belts, and parts with high complexity can be polished with soft polishing wheels. Large batches of small parts use batch lighting. Batch lighting can be subpided into roll-rolling, vibrating machine vibration lighting, centrifuge centrifugal lighting and rotating lighting and other methods. Mechanical polishing has a low amount of grinding on the surface of the stainless steel tube, so it is also difficult to polish a rough surface. At this point you need to do pre-grinding process, use the grinding wheel, polishing tape stained paste to do grinding, pided into coarse, medium and fine grinding. After grinding, the surface roughness of the stainless steel tube can reach 0.4 μm. In order to achieve other inpidual requirements, such as descaling, deburring, slag removal, or matte finish, surface treatments such as sandblasting, shot peening and wire brushing can also be used. Stainless steel wire wheels can be used for polishing. Effectively reduce iron pollution. Chemical polishing Chemical polishing involves immersing stainless steel tubing and other parts in a suitable solution. Since the solution will dissolve the protruding parts of the surface of the stainless steel tube more quickly, the surface of the stainless steel tube can be leveled to achieve polishing. Chemical polishing usually has a weaker polishing ability and only slightly enhances the brightness. However, the mechanical polishing method is more labor- and time-saving than the mechanical polishing method, and can also handle the inner surface of small parts. Chemical polishing process needs to pay attention to several aspects. Because the polishing speed is fast but the finish is poor, it is more suitable for pre-polishing. After chemical polishing will increase the surface activity, it must passivate the working surface to ensure corrosion resistance. Electrochemical polishing Electrochemical polishing treatment can increase the reflective performance of the stainless steel tube surface, improve the corrosion resistance, reduce the surface hardness of the machined parts, and reduce the friction coefficient due to the reduced surface roughness. Electrochemical polishing can also be used to remove parts such as burrs. Compared to mechanical polishing, the features of electrochemical polishing are as follows. The electrochemical polishing will form a passivated surface, improve the corrosion resistance of the material, and mechanical processing can not be achieved. Second, electrochemical polishing has certain requirements on the substrate, such as non-uniform microstructure will form a non-uniform polishing surface, deep scratches can not be polished flat. Mechanical polishing requires less substrate. Third, if you are dealing with parts with complex shapes, using electrochemical polishing is easier to achieve. Electrochemical polishing is also more efficient than mechanical polishing, but care must be taken not to place large workpieces. Electrochemical polishing of the workpiece surface current density must be uniform, so that the brightness of the polished surface will be uniform, due to the larger current electrochemical polishing, the fixture and the workpiece should have a large enough contact area and form a good contact, or easily lead to Local overheating and burning of the workpiece. Finally, it should be noted that some of the processes used to polish austenitic stainless steels cannot be used to polish martensitic stainless steels, because they are prone to corrosion. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pipes should have different forms of packing according to their product type, finish, size and transportation mode. Because the stainless steel pipe is usually the pipe, the pressure pipe, the mechanical pipe and the decorative pipe, and the stainless steel pipe can be processed, annealed and pickling, cold working, grinding and polishing and decorating, so the size and the processing luminosity of the stainless steel pipe are very complex, so it should be especially injected in order to purchase order. The corresponding packing, marking and shipping methods. If there is doubt about some shipping methods, we must do well in communication work. Stainless steel pipes are often packed, transported by bags, boxes or protective containers. The outer diameter of the stainless steel pipe with a size larger than 6 inches can be transported either in bulk or in packaging, or without packaging and transportation. The best packing method is determined by length size, outer diameter, wall thickness, finish and transportation. Most of the polishing pipes are packed in wooden boxes or other suitable materials. It is necessary for a stainless steel pipe to be bundled, because when the stainless steel pipe is transported, the amount of the pipe may lead to the risk of bending, extrusion or distortion during the handling of the pipe. In addition, some other auxiliary measures are required. Bales are usually fixed with flat steel ribbons, but other suitable materials can also be used. The number of fixed nodes depends on the length and weight of the bales. Some stainless steel pipes may have special smoothness requirements, special orders, special modes of transportation, or other factors. In this case, special containers are required to be prepared, such as paper pipes, cartons, wooden cases, or similar containers. During the transportation process, stainless steel pipes must be protected and covered. But if the outside diameter or inner diameter surface is the key feature, the protective cloth will be added to the railway transport equipment, and the waterproof cloth will be added to the truck. A certain degree of dirt and oxide is permissible, whether it is no coating, or galvanized pipe, or a non spray pipe, or a pipe that is sprayed with a non dry oil coating. Many ordinary stainless steel pipes are transported by unprotected open wagons. In addition to the mess outside, stainless steel pipes are usually kept neat, and there is no need to prepare separate items for shipment. Fixed or separated stainless steel pipes can be transported into cargo, separated into a certain size and quantity, requiring additional handling and materials. Adding stainless steel pipes to a closed truck or truck requires extra handling, and a small stainless steel pipe with a small size can also have extra labor costs. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)