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It is well known that the surface quality roughness of the stainless steel plate will affect the effect of the finished product, so what are the effects of the roughness? Stainless steel plate surface has a layer of dense oxide film can prevent oxidation of stainless steel material erosion surface, which could effectively avoid oxidation, whereas a more porous oxide film is constantly upset oxidation. In continuous production line, the surface of stainless steel is forced oxidation through continuous pickling method, thus increasing the toughness of the surface oxidation film of stainless steel. In addition, the effect of high temperature oxidation resistance, thickness of oxide film and chemical composition of oxide film should be tested. The results showed that the composition of oxide film and the oxide film thickness were not significantly affected by the adjustment of acid concentration. In the higher temperature environment, the application will be oxidized and discolored. Under the environment of high temperature stainless steel plate surface oxidation surface oxidation film thickness of the board, this kind of phenomenon also and oxidation resistance of stainless steel plate itself and material heat capacity is directly related to stainless steel plate surface roughness and surface of the chromaticity of heat absorption capacity per unit area and cause stainless steel plate color degree. Relevant data shows that when the surface roughness of the surface of the stainless steel plate drops to 0.022 mu m, the absorption capacity of the stainless steel plate will decrease significantly, and the stainless steel plate will not be further oxidized. When the oxide film thickness of stainless steel plate is basically maintain the original thickness, the degree of discoloration is slight. Conversely, if the thickness of the oxide film is significantly increased, the color will become more severe. The carbon content of stainless steel plate materials is low, and the carbon atoms in the high temperature environment can easily spread to the stainless steel matrix during the oxidation process, so the oxidation process of stainless steel is accompanied by the carburizing process. In order to verify the effect of silicon on carburizing, only the silicon elements were adjusted in 310S stainless steel, and then the high temperature cycling test was conducted. The test results show that the high temperature oxidation performance of the stainless steel materials can be enhanced significantly when the quality score of the chromium element increases to above 22% or the quality fraction of the silicon element is above 2%. Source: China Stainless Steel Plate Manufacturer – wilsonpipeline pipe fitting Industry Co., Limited (www.wilsonpipeline.com)

The main problem of large stainless steel pipe bending equipment is that the chute can’t move along with the stainless steel pipe, it is difficult to process, and the material is relatively wasteful. For these problems, the following is the improvement plan. Metal forming elbow is a very important part in the production process of the manufacturing, it has attracted the attention of people, applications are also very much, such as aerospace, shipbuilding and other ordnance system, also has such as natural gas pipelines, oil pipelines, water pipelines and other small pipeline system. In these piping systems, changing the direction of pipes is a very common thing, but it will always be applied to all kinds of stainless steel elbows. In reality, the circular curved pipes with various diameters and angles are mostly manufactured by manual or mechanical bender. And this kind of bend model uses a fixed sliding groove. The friction consumption between the fixed chute and the pipe will cause greater bending moment. The application capacity of the equipment can not be well utilized, because the existing equipment lacks the interface of the mobile chute, so if we want to make the chute move, we must think about it on the mold. Now, the fixed chute has three disadvantages: the chute cannot move along with the movement of the pipe, and there is a higher friction between the pipe and the chute, resulting in a scratch on the surface of the pipe and the sliding slot, thus affecting the quality of the stainless steel elbow and the service life of the die. The fixed chute is connected by the tail between the swallowtail and the equipment. Every time it is necessary to process the tail of the swallowtail, it is difficult to process and waste a lot of materials. Therefore, in order to meet the higher requirements, it is a good choice to replace the fixed sliding groove with a movable sliding groove. The advantages of mobile chute is its main structure is adopted, and the chute chute between the body coated with a lubricant between the chute and the chute body is sliding, there is no relative friction between the chute and the tube, thereby effectively ensuring the tube surface quality, improve the actual service life of die. The friction between the slots and the slots needs to be much smaller than the friction between the fixed slots and the slots. The chute seat of the mobile chute has good versatility. For the new elbow specifications, it is generally necessary to repeat the manufacture of the chute, that is to say, avoid unnecessary repetition and add T swallow tail to reduce the difficulty of processing and save material effectively. Pipe mold mold block combination design improved is the core part of the whole design, each a small mold block is formed by the die block, similar fan-shaped ring structure shape, with its previous fan disc in different places in addition to its shape and increased in a sliding disk base slide. Its working principle is this: when choosing some specifications of the tubes, can according to the diameter and bending radius to determine the size of the mold with different specifications, and then fixed to the top of the disk base, of course, the mold block is made beforehand, its entire manufacturing standards in accordance with the pre bending pipe as the standard, in accordance with the bending radius of the die block in the sliding seat position adjustment module to achieve. The combination is composed of a base, adjusting the mould a disc chute, chute seat and several mold block, the improved combination of adjustable mould, which is l to 9 die block belongs to the activity, the number and size of enough according to the production pipe replacement and adjustment, and between the sliding slots the traditional plays the role of pushing the tail is different, they can be in accordance with the size of about in the chute seat movement and changing, so as to meet the needs of different diameters of products. The slot seat is a practical requirement to ensure that the sliding groove is slid right and left so as to better adapt to various pipe pipes. The base of the original plate has a fixed function, with a slide seat on it so that the die block can be slid on it to reach the bending radius of the stainless steel elbows. Source: China Stainless Steel Elbows Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In general, the process of manufacturing stainless steel pipe fittings in accordance with the order including cutting, forming, heat treatment, surface treatment, cutting, nondestructive testing, surface protection and the logo, the following step by step under the details. The first is the cutting, the production of stainless steel pipe fittings used in the material is usually pipe, stainless steel plate and stainless steel bar, according to the characteristics of the material and the shape of the product to choose blanks blanking method. Blank shape, size and other requirements are also based on different product specifications. For stainless steel pipe, the commonly used methods of cutting the band sawing machine or bow saw cutting, gas cutting, plasma cutting. For stainless steel sheet, often used cutting method is gas cutting, plasma cutting, punching punch. For stainless steel bars, frequently used blanking methods include band sawing or bow sawing, blanking and cutting. The second step is forming, also known as welding, all stainless steel pipe production and forming processes are inseparable from this process. This article describes the heating and welding in the next part of the forming process. The heating refers to the requirement of deformation of the stainless steel material in the forming process and heating of the billet during forming. The heating temperature is generally determined by the material and the process needs. Hot elbow or hot elbow forming, the general use of IF or high frequency induction heating method, but also the use of flame heating method. This type of heating process is a continuous heating of the elbow or elbow forming process, the tube is heated during the movement and complete the forming process. Hot elbow, hot tee or forging forming, the general use of reflective furnace heating, flame heating, induction heating or electric furnace heating and other methods. Such heating process is to first heat the stainless steel tube to the required temperature, and then into the mold or forging forming. The welding, there are two cases, one is the use of pipe production of pipe, the use of pipe forming process and the use of seamless pipe forming process is basically the same, the pipe forming process does not include the welding process, the other is from the pipe factory To complete the pipe forming the welding process required, and then welded into the tube after the stainless steel plate tube and then pressed the tee and so on. The third step is heat treatment, this process is an important part of stainless steel pipe production. After heating, heat preservation and cooling heat treatment step, to remove forming hardening, residual stress, deformation of metal defects and so on, so that after the formation of stainless steel pipe fittings of the metal structure, performance changes, return to the pre-deformation state or to make its performance Be improved and improved. Often used heat treatment equipment is the reflection furnace, electric furnace, etc., the control method is the thermocouple inside the furnace through the sensor connected to the temperature – time automatic recorder control device. Different pipe products in the standard heat treatment requirements are not the same. Not all of the deformed pipe must be heat treated, in general, for the low-carbon steel pipe fittings the final forming temperature of not less than 723 ℃, no longer need to heat treatment, due to the temperature under the conditions of its final organization Usually normalized, below this temperature or higher than 980 ℃ to be heat treatment, alloy steel or stainless steel tube regardless of the use of cold forming or thermoforming, should be heat treatment. Routine inspection The effect of heat treatment is usually to see the hardness test situation. The fourth step is the surface treatment, the method is basically sandblasting, shot blasting, grinding, pickling, etc., so as to remove the surface rust, scratches, etc., to improve the surface smoothness, to follow-up processing, testing needs. After the shot blasting stainless steel pipe fittings, the surface hardness will be slightly increased. The fifth step is cutting, it is to complete the welding of stainless steel pipe ends, the size of the structure, shape and position tolerance process. For some pipe products, cutting and processing, including internal and external diameter of the processing. Cutting is usually done by a dedicated machine or general-purpose machine tool. For oversized pipe fittings, when existing machine tools can not meet the machining requirements, they can be finished by other processes, such as gas cutting and sanding after large-diameter elbows . Stainless steel pipe usually appearance, size inspection after cutting. The sixth step is non-destructive testing, non-destructive testing is to detect stainless steel materials and pipe processing process may produce defects in an important process. Most stainless steel pipe product standards for non-destructive testing requirements have some provisions, but the requirements are not the same. In addition to the non-destructive testing of stainless steel standards and ordering requirements, some of the more stringent quality control manufacturers also make non-destructive testing requirements based on materials, processing techniques, and internal quality controls to ensure the quality of the final product. The actual work of non-destructive testing of stainless steel pipe to determine the level of acceptance should be based on the order requirements or standards of the specific provisions. As the stainless steel pipe is usually the original surface of the original pipe, plate or forgings, stainless steel pipe surface quality of the non-destructive testing, if there is no clear grade requirements can be Ⅱ grade, for mezzanine and crack such defects are not easy to determine the depth of As unqualified. For non-destructive testing of internal quality of pipe fittings, if there is no clear grade requirement, ray inspection should be carried out in grade Ⅱ and ultrasonic inspection should be grade Ⅰ. In order to avoid the stainless steel tube during heat treatment may have a defect situation, the final non-destructive testing of stainless steel pipe fittings to be carried out after the heat treatment. The seventh step is the surface protection, the use of pickling stainless steel pipe passivation approach. The main purpose of stainless steel pipe surface protection is anti-corrosion, but also to achieve beautiful appearance of the product results. In general, the order surface protection put forward specific requirements, the manufacturer according to the requirements of the order to complete the stainless steel pipe surface protection. The last is marked on the stainless steel tube, the mark is an integral part of the product is to achieve the basis of traceability requirements. In general, the standard stainless steel pipe on the logo content and methods to do some provisions. Stainless steel pipe signs usually include the manufacturer’s trademark, name, material grade, specifications and other requirements of the order. Signs are mainly permanent signs, such as stamping, sculpture, galvanic corrosion, there are also non-permanent signs, such as jet printing, labels and so on. In addition, in addition to some of the above conventional production processes, in order to control the quality of raw materials, the production plant to complete the inspection of raw and auxiliary materials to ensure the accuracy of the use of materials to meet some special requirements, but also for example, microstructure , Intergranular corrosion, ferrite and other tests and tests to ensure that the final product quality in line with the needs of use. Source: China Pipe Fittings Manufacturer – wilsonpipeline pipe fitting Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pipe fittings drawing processing, usually found near one end of the clip, some small diameter stainless steel pipe fittings, its wall thickness size and drawing pipe billet is the same as the former, is only the reducing pipe didn’t decrease wall deformation, cause empty pull effect. If the empty pull segment is relatively short, as long as it is cut off at the cutting head, the yield, quality and use of the stainless steel pipe will not have much impact. However, if the empty segment is longer or too long, when the stainless steel pipe is produced, it will cause a short ruler to be scrapped. If you don’t pay attention when cutting the stainless steel pipe or inspection, you will not be able to use it properly and even have an accident. There are five main reasons for the short length of the stainless steel. First of all, the core stick forward is not timely. In general, the operation process of the fixed short core bar drawing is to remove the core rod from the first place to the back limit position, and the short core rod is pulled out from the die hole. To lubricate the inner wall of the head and lubricate the inner wall from the back end. Core rod to go forward, to promote the stainless steel pipe billet clamp side wear out from the die hole, because is affected by the holder, at this time of the mandrel can not progress to the specified location, mandrel will continue to keep the forward thrust. When the clip head is worn out of the die hole, it is clamped by the pull of the car, and then pulled out from the die hole before pulling out the car. But in the actual production, drawing medium and small sizes of stainless steel pipe fittings, pipe set on the mandrel, after operation are the clip from the die hole, since the core rod to move forward to promote core rod into the people die. During the operation, sometimes the mandrel has not started to move forward, and the clamping of the die hole will be clamped forward by the car tongs, resulting in a longer empty segment. The second reason is the core bar. If mandrel position adjustment is not appropriate, too, at the beginning of the drawing mandrel is not easy to smoothly into the person die, even in the entire process of drawing, into not to die, there will be a period of the sky, even also can have the entire length of stainless steel pipe fittings all empty cases. The third reason is that the mandrel is not fixed. In fixed short mandrel drawing, because the core rod and pipe billet surface will be within the lubricating oil, to depend entirely on the pipe wall friction with mandrel brought its people die is more difficult, the back-end must have a thrust. If the core stick is not fixed, the core rod has not entered the manhole and the thrust disappears. It can also be extruded, resulting in the formation of the air pull. The fourth reason is that the gap between the core and the pipe is too large. When swimming core head drawing, if the core gap between head and the pipe is too big, especially when small drawing specification stainless steel pipe fittings, in drawing at first, the core head is not stable in the pipe billet, is very difficult to enter the deformation area, leading to empty, pull. The fifth is that the stainless steel pipe billet is not stopped. When the head of the moving core is pulled out of the small size of the thin wall pipe, the core head shall be mounted on the surface of the stainless steel pipe at the back of the core, and a pit shall be punched in the outside, so that the core head should not be moved backward. If it is not in the pipe, the core is not easy to enter the deformation zone, thus forming a long empty segment. The main measures to reduce the air segment of the stainless steel pipes are 3 points. First, it is the standard operation procedure. When the stainless steel pipe is worn out of the die hole, the core bar is pushed to the die hole and then pulled and pulled. When using the hydraulic cylinder to control the mandrel, do not step back in the whole drawing process. When the pedal method is controlled, the core rod should not loosen the pedal before entering the die hole. The second is to adjust the position of stainless steel mandrel, not too close, but not too forward. When using a moving core, the gap between the large cylinder and the stainless steel pipe is not too large, and the clearance should be reduced as far as possible without affecting the core head. When the core head is installed in the stainless steel pipe, it is necessary to check the pit and prevent the core head from moving backward. Source: China Pipe Fittings Manufacturer – wilsonpipeline pipe fitting Industry Co., Limited (www.wilsonpipeline.com)

Molybdenum is mainly used for production of iron and steel industry in many countries, basically accounted for more than 8 of the molybdenum is added as elements of steel, but only about 2 is used to produce metal molybdenum, super alloy and special alloy, chemical products, they are used in the petroleum chemical industry, light industry, electronic and high-tech fields. Molybdenum elements can improve the hardenability and thermal strength of stainless steel pipes. Avoid temper brittleness and improve corrosion resistance in some medium. Mo can make larger sections of stainless steel pipe parts quenching depth, quenching and tempering, improve the anti tempering stability of stainless steel material, the material can be tempered at high temperature, so as to effectively reduce or even eliminate the residual stress, enhance the plasticity in the Mo elements in carbon steel in addition to the above use, but also can reduce the the carbide forming tendency of continuous net at the grain boundary in the carburized layer, reduce the residual austenite in the carburized layer, enhance the relative wear resistance of the surface layer of the stainless steel pipe. In 316L and 2205 stainless steel welded pipes, the molybdenum element can also guarantee the stability of the hardness of the stainless steel and enhance the resistance to deformation, cracking and wear. In the stainless steel and acid resistant steel, the molybdenum element can further enhance the corrosion resistance in various environments. In addition, the corrosion tendency of chlorine ions can be avoided. The effect of molybdenum on Microstructure and heat treatment of stainless steel welded pipe is mainly four points. In the first Mo solid solution in stainless steel and ferrite, austenite and carbide in the pipe, which is to narrow the austenite phase elements; when the content is low, and iron and carbon composite formation of cementite, when high concentrations can generate special carbide; molybdenum can improve the hardenability of stainless steel pipe, than Cr, was less than that of manganese; molybdenum can enhance the stability of tempering steel. Molybdenum plays a great role in the mechanical properties of stainless steel pipes. First, molybdenum has solid solution strengthening effect on ferrite, and it also increases the stability of carbides, thereby increasing the strength of stainless steel. Molybdenum also improves the ductility and toughness of stainless steel and is also beneficial to the enhancement of wear resistance. In addition because molybdenum will make deformation enhanced after softening and recrystallization temperature and recovery temperature increase, and significantly enhance the creep resistance of ferrite, can effectively inhibit the aggregation of cementite at 450-600 DEG C, promote the precipitation of special carbide, so it became an enhanced heat resistance stainless steel material is the most effective alloy elements. The effects of molybdenum on the physical, chemical and technological properties of stainless steel pipes are also reflected in four aspects. The first is 1.5% carbon steel, 2%-3% molybdenum will improve the remanence and coercivity; can make stainless steel pipe surface passivation in reducing acid and strong oxidizing salt solution in the second, so Mo can generally improve the corrosion resistance of stainless steel materials, stainless steel in chloride solution to avoid the occurrence of pitting corrosion in liquid the third is the antioxidant; molybdenum high content of stainless steel materials will deteriorate. Finally, the stainless steel with no more than 8% molybdenum still can be forged and rolled, but when the molybdenum content is high, the stainless steel pipe has greater resistance to the deformation of the heat processing. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

According to the relevant european standards, the conventional cold rolled stainless steel plate has two kinds of surfaces, one is the 2D/2B surface, the other is the surface after cold rolling, annealing, pickling and leveling. The second one is the 2R surface, which is cold rolled and annealed after smooth annealing. Before welding, clean up the paint, dirt and oxide layer of, the former is usually produced by horizontal high yield continuous annealing pickling line, and the annealing of stainless steel strip is carried out in oxidizing atmosphere. The oxidation layer generated in the annealing must be removed and then recovered to the passivation state. This process is generally achieved by electrolysis descaling and chemical pickling, and chemical acid washing is usually used as a mixed acid solution (i.e., nitric acid and hydrofluoric acid). And a large number of pollutants such as nitrogen oxides, nitrate and sludge in the waste water will be treated by special treatment process. The latter is produced on a vertical bright annealing unit. The stainless steel plate is annealed in the mixture of hydrogen and nitrogen. If the dew point is well controlled and the oxidation of the strip surface is avoided, the pickling process is not necessary. Because of the surface features and good appearance of the surface, the stainless steel strip on the 2R surface is more popular. By combining the main advantages of the two processes, an innovative processing technology has been developed and applied to the annealing and pickling treatment of stainless steel plate cold rolled strip. It is a new stainless steel strip production technology that can get close to the 2R’s enhanced surface quality. It can also maintain the same production capacity and production cost as the traditional annealing pickling line, and it can also reduce the impact of chemical pickling process on the environment. Compared to the traditional annealing and pickling line, the new technology can significantly reduce the oxidation of stainless steel strip in annealing period, so chemical pickling treatment can cancel or reduce the use, in order to get better surface quality, can save the cost and reduce the need for acid pickling wastewater treatment capacity. Controlling the formation of oxide layer on the surface of stainless steel plate is through the special strip heat treatment cycle and accurately controlling the amount of oxidation in each process step (heating and cooling section), especially in the high-temperature process section. A key step in this process is the first control section of rapid heating under oxidizing atmosphere, the oxide film and a thin layer of oxide crystal nucleus formation, followed by annealing, mechanical properties, grain size, the carbon demand of the solution and so on, this process is carried out in a non oxidizing atmosphere, can limit the generation of oxide layer the. In the cooling section of non oxidizing atmosphere, the cooling rate can prevent carbides from precipitating. The main advantages of the new process is reflected in the production capacity and the same traditional annealing and pickling line and flexible production, saving equipment investment and management costs, reduce environmental pollution and reduce waste disposal costs, but also get better surface quality of products, the last is that this technique is suitable for the new factory is also suitable for the transformation of the existing factory. Source: China Stainless Steel Plate Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pipe fittings in the installation, there are two ways are the viega profi-press and the groove, and they have their own advantages, including stainless steel viega profi-press pipe is an upgraded version of the stainless steel pipe fittings, compared with the ordinary stainless steel pipe fittings, the installation is very easy. Its working principle is to put the stainless steel tube inserted into the viega profi-press pipe socket, at the time of installation does not need to be welded, using specialized conformity of tools the stainless steel pipe stuck inside pipe fittings, installation time, and can also be fired later period maintenance updates, opposite for the stainless steel pipe fittings with better efficiency. The section shape of the compression section is hexagonal shape, with an o-ring seal between the stainless steel tube and the pipe fitting, which has the advantages of stop seepage, tensile, shock resistance and high pressure. However, the drawback is that when the connection is connected, the pressure-type pipe is meant to kill the connection directly, and then it is not to be removed, so the installation will need to be reinstalled once the installation is made. This kind of stainless steel pipe fittings is a kind of advanced connector commonly used in direct drinking water system, water system, heating system, steam system, industrial oil pipe system and industrial pipe system. Another kind of groove type pipe connection technology is also known as general clamp connection, now has become a choice of liquid, gas pipe connection technology, though the technology in domestic development time later than abroad, but with the development of the technology, has been recognized by the domestic market rapidly. At present, it has been widely used in various fields in China, and it has begun to gradually replace the traditional connection of flange connection and welding. There are two main types of pipe fittings. One is the pipe fittings that are connected to seal and have rigid joint, flexible structure, mechanical three-way and grooved flange. The second is the connection of the transition of the pipe fittings with elbow, tee, four-way, reducer, blind, etc. The grooved fittings with connection seals usually consist of three parts: sealing rubber ring, clamp and locking bolt. In the inner lining of the rubber seal on the outer edge of the connected pipes, and match the grooves and rolled in advance, then buckle on the outside of the rubber ring clamp, then with two bolts. Because the rubber sealing ring and clamp the peculiar can seal structural design, can help to form good sealing groove joints, and with the increasing of fluid pressure stainless steel tube, the stainless steel pipe fittings of sealing will be further improved. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

As a kind of metal pipe, the stainless steel pipe has the characteristics of corrosion resistance, high temperature and high strength, most of which are used in the process pipeline of newly built and expanded petrochemical equipment. However, the biggest problem of this type of stainless steel welded pipe is the complete fusion welding problem of the base and the laminates. Therefore, to obtain the best welding effect, the following is the most correct welding method of stainless steel welded pipe. Before welding, clean up the paint, dirt and oxide layer of the contact layer before welding, and prevent the impurity in the welding process from being decomposed into H2O and CO2 to affect the welding effect. Preheat the base and laminates of thestainless steel pipe before welding. Preheat the use of electric heating method. The center line is used as the benchmark, and the two sides are not less than three times the thickness of the wall, and not less than 50mm, and avoid overheating. In the welding process, it is necessary to weld the composite layer before welding the base, and the sequence of the whole process is sealing layer, bottom welding, transition layer, filling layer and covering layer. The inner wall of the pipe shall be kept flush when the pipe is welded, and the inner wall shall not exceed 10% of the thickness of the pipe wall, and shall be less than 2mm. When welding, use multi-layer welding as far as possible, the joint of weld bead weld bead should be as wrong as possible, the weld bead is not too broad and too thick. In the process of soldering, the pipe must be filled with argon to ensure the weld quality. In the bottom welding position, the position of the inverted welding is used with the inner fillet, and the position of vertical welding and horizontal welding is used for welding. Additional best even in the arc of groove, avoid in the arc welding parts, the arc place to ensure the weld penetration and fusion, to fill arc crater, near the end of welding, to reduce the argon gas flow rate, pressure to avoid overheating ambassador weld sag. Don’t contact with tungsten or the arc column of the arc, avoid damaging the stability of arc and forming the tungsten defect. The wire end shall not be withdrawn from the protected area to avoid the oxidation of the welding wire. In a way to control the temperature between under 150 ℃, on both sides of weld used in the construction of water cooling method, is to put a wet towel wrapped on both sides of the outside is 80 mm from the weld steel pipe, the weld as soon as possible to below 150℃. After welding, carefully clean the surface of the stainless steel pipe pieces of welding slag, welding tumor spatter and various kinds of dirt, when necessary, the weld seams should be partially repaired. The residual stress should be eliminated after the heat treatment, the post-welding process should be carried out according to the design requirements, and the best use of the electric heating method in local heat treatment. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Now stainless steel pipe fittings are widely used in all kinds of pipeline projects, especially for the three way, elbow and size head. The main reason is that the stainless steel pipe has good forming, strong pressure resistance and easy welding, which can effectively guarantee the pressure bearing capacity of the pipeline. Therefore, in pipeline engineering, especially petrochemical and other high temperature, high pressure and flammable and explosive pipelines, the rational use of stainless steel pipe fittings and the quality of pipe fittings are very important. Because of this, in the design and installation of pipelines, especially in petrochemical industry and high temperature and high pressure inflammable and explosive pipeline project, whether from design or manufacturing, even to each link of construction installation and inspection of the design, manufacture and installation personnel are in need of strict quality control, to ensure the selection, pipeline timber, manufacture, installation and quality inspection, otherwise it will cause huge losses in installation construction and production process. In the course of construction, there are several problems in the quality of the general stainless steel pipe. The following is the following. First, the wall thickness of the stainless steel pipe fittings is not uniform. The uneven wall thickness of the pipe usually occurs in the parts of the maximum deformation of the pipe. For example, the wall thickness of the back of the elbow is thinner than the other, and the wall thickness of the pipe and pipe body is not equal. In the relevant national standards, the thickness reduction of stainless steel pipe can not exceed 12.5 of nominal thickness of pipe fittings. However, field measurement shows that some wall thickness thinning amounts to 20-30. However, it is difficult to find the measurement tools such as ordinary caliper and so on. Only by using the ultrasonic thickness gauge can be detected. The second is the problem of excessive hardness. The reason is the heat treatment process after forming. The solution is to use the right heat treatment process and do a heat treatment again. The third is the defects formed in the material and processing. The safety of this problem is the most dangerous, and it is not easy to check out. The factors that cause defects are many and complex. They not only have their own defects of stainless steel, but also have problems in manufacturing process. In addition, they may also be caused by incorrect heat treatment process. Inspection of stainless steel welded pipe fittings before and after delivery is a key process to ensure the quality of pipe fittings, especially for pipes that are subjected to high temperature, high pressure and flammable and toxic media. Now the stainless steel pipes are usually inspected for appearance size, hardness, thickness and magnetic particle inspection (MT) and ultrasonic flaw detection (uT) before they leave the factory. From the aspect of inspection and arrival fittings, it is easier to detect magnetic particle defects and ultrasonic flaw detection. Because of the magnetic particle inspection, the commonly used yoke method (carbon steel pipe) is used in the factory. But restricted by the equipment, the method is limited in the outer surface of stainless steel pipe fittings, but the problem appears most is on the pipe wall, the crack usually appears such stainless steel pipe especially the crack of small diameter tube wall, to use the magnetic method or eddy current method to do inspection ultrasonic examination, and this is a the equipment and technology requirements are very high test items. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The current history of duplex stainless steel has reached the third generation. The first generation represented the 3RE60 stainless steel in the mid-1960s, which posed the problem of HAZ. The second generation was developed in the 1970s , Is characterized by ultra-low carbon and nitrogen, representing the grade 2205, the pitting equivalence index PRE is 32 to 39; the third generation is super-low carbon, high molybdenum, high nitrogen content developed in the late 1980s Duplex stainless steel, on behalf of grades 2507,32750, etc., their PRE value must be greater than 40. Now, with the use of stainless steel higher and higher requirements, duplex stainless steel has developed a new generation of higher strength, better corrosion resistance of duplex stainless steel – super-duplex stainless steel, on behalf of the steel is 32,707, 33207,2707HD. The new generation of super duplex stainless steel product features can be elaborated from three angles, the first is the chemical composition and microstructure, the design of such stainless steel materials is high alloying, not only to further increase the chromium, molybdenum, nitrogen content To improve the strength and corrosion resistance, but also a reasonable adjustment of the ratio of other elements, special super duplex stainless steel PRE value close to 50. In addition, the proportion of metallurgical phase is also controlled. When the super duplex stainless steel is solid solution at lower temperature, there is a certain amount of harmful phase σ phase in the microstructure, and the phase can basically dissolve when it is above 1100 ℃. The austenite phase and the austenite phase each account for approximately half, and to avoid the weaker phase being preferentially corroded, the respective pitting resistance index (PRE) design of both austenite and ferrite phases in the steel is equivalent to 32707 , The average PRE value of each phase is less than 1 on average. Second is the corrosion resistance, 32707 and 33207 theoretical equivalent pitting resistance at about 50, the critical pitting temperature of both are higher than 90 ℃, and 32750 is about 80 ℃. Ultra-duplex stainless steels can even replace high-alloy austenitic stainless steels and nickel-base alloys even in the most corrosive environments where standard austenitic stainless steels are used. The third is the mechanical properties, the super duplex stainless steel yield strength and pitting resistance and its almost equal to 2 times the performance of austenitic stainless steel. The heat exchanger tube using 32707 material yield strength is usually 800Mpa, tensile strength is 1000Mpa, quenching heat treatment state elongation greater than 25%. The 33207 stainless steel has better tensile strength, quenching heat treatment, the tensile strength is higher than the super dual-phase steel 32750 about 20%. In addition, the impact toughness of 32707 is also very good, its brittle transition temperature below -50 ℃. Of course, the domestic mainstream now also 2205 types of traditional duplex stainless steel, super duplex stainless steel production is still relatively small, and special super duplex stainless steel has just started, still in the research and development stage, the need to speed up the domestic special super duplex stainless steel Development and production. Source: China Stainless Steel Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Because the offshore oil platform riser has long suffered the wave scour, it is necessary to have high strength and excellent resistance to point corrosion material. In all kinds of alternative materials, because super duplex stainless steel possesses austenite and ferrite structure at the same time, it has many advantages such as high corrosion resistance, good mechanical properties and good corrosion resistance to chlorine ion, so it is an ideal offshore platform material. However, the super duplex stainless steel is sensitive to the third phase precipitation of intermetallic compounds. How to control the production process in the welding and heat treatment process is a difficult point. First talk about perfect super duplex stainless steel welded pipe manufacturing process, the order including the inspection of raw materials, stainless steel plate, ultrasonic flaw detection, edge planing, shaping, welding, the whole round, cutting, welding, sizing and heat treatment, weld seam detection, pipe end penetrant inspection and hydraulic test, pickling and passivation and finished products after the detection of marker packing. The next is formed, in the production of welded pipe, the production difficulty is on stainless steel strip edge bending moment applied to ensure effective, more difficult to solve using traditional molding technology; but the yield strength of duplex stainless steel is about two times the ordinary austenitic stainless steel molding, it is also more difficult. The use of flexible forming technology stick tension effect when bending, the maximum bending moment applied to the edge of the stainless steel belt; favorable conditions and also the use of electrodeless roll used, according to the strength and thickness of the stainless steel belt, adjustable bending forming degree so as to achieve the optimal welding conditions. The third step is welding, using plasma arc welding and tungsten arc argon arc welding complex welding process. First, plasma arc welding is used to do penetration fusion, so that it has the effect of one-sided welding and double-sided molding. Then TIG welding is used to make filler and cover surface, and pure argon protection is used for welding. In order to reduce the Precipitation Tendency of harmful phase, low line energy is used as far as possible in welding process, and the line energy is better than 16kJ/cm. In addition, the interlayer temperature is very important for the welding of duplex stainless steel. It must be controlled below 100 degrees. The high interlayer temperature will increase the tendency of harmful phase precipitation and ultimately affect the performance of products. The last is heat treatment. After heat treatment, the whole welding pipe is treated by induction furnace. The heat treatment temperature reaches 1050-1120 degrees, and then water spray is cooled to 40 degrees below. Source: China Super Duplex Stainless Steel Welded Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The content of chromium and nickel in 310S stainless steel is higher, and its corrosion resistance is better than that of ordinary 18-8 stainless steel. In boiling nitric acid with a concentration above 68.4%, the corrosion resistance of ordinary 18-8 stainless steel is not satisfactory, but 310S stainless steel can be applied in 65 ~ 85% nitric acid. 310S stainless steel is widely used in the nitric acid production equipment, such as the tail gas preheater, the heater, the condensing pipe, and the nitric acid producing equipment for the production of uranium oxide. In addition, the 310S stainless steel has good thermal strength, oxidation resistance and resistance to vulcanization. The maximum application temperature is 1200 C, the continuous application temperature is even 1150 degrees C, and its heat resistance is much better than that of 304, 316, and 321 stainless steel. Compared to nickel chromium superalloy and cobalt chromium superalloy, its cost advantage is very obvious. But some aspects in the production are difficult to control, it is a poor heat conductivity and thermal conductivity of only 304 stainless steel 58%, 17 Cr 47%, crack of continuous casting billet tendency; the second is serious dendrite segregation, the maximum temperature of hot rolling heating will have some limitations, high temperature deformation resistance, thermoplastic low. In the rolling process is easy to form crack; third is chromium carbide precipitates, sigma tendency. In the actual production, is an example of this is the use of electric furnace, LF furnace refining, continuous casting, hot rolling diameter is 90mm in diameter 310S stainless steel rod wall cracks in the heat pipe wear process, so do the analysis take inner wall cracking of 310S stainless steel pipe, so that the main reason for the cracking and some improvement measures. The cracks in the head of the stainless steel pipe were observed, and a certain length of the pipe was extended from the head to the pipe to check the cracking of the inner wall. The samples were taken on the pipe and the chemical components were detected on the SPECTROLAB M10 photoelectric direct reading spectrometer after grinding. The metallographic specimen was tested at the crack, mainly the grade of inclusion, the observation of the crack micromorphology and the analysis of the deformation of the tissue. Samples with foreign bodies in the crack are used to analyze the chemical composition of the material with energy spectrum under scanning electron microscope. The preparation, grinding, etching, microscopic examination and microphotography of the sample are carried out according to the GB/T13298-1991 “metal microscopic examination method”. The data show that the high content of ferrite in stainless steel, low heat deformation temperature of pipe and fatigue use of molybdenum head will affect the cracking of 310S stainless steel pipe. We must use some measures to improve, first is the blank of the existing pipe before to try to increase the heating temperature, holding time, speed up the wear speed, need to check the molybdenum before production use; the second is to optimize the appropriate chemical composition, without increase of nickel content, lower chromium according to the standard control elements, residues of molybdenum elements can’t be too much; third is because the alloy elements of 310S stainless steel with high content, serious dendrite segregation, coarse columnar crystals, low melting material and impurities easily intergranular and concentrated in the heart of the slab, in the smelting, casting molten steel cleaning after upgrading clarity in the premise of not completely exclude impurities or slag effect, reducing pouring temperature, superheat control, electromagnetic stirring technology, reduce dendrite segregation, improve the proportion of equiaxed grains It reduces the tendency of embrittlement caused by the segregation of impurity elements, improves the quality of the casting billet, and provides excellent quality for the subsequent heat processing. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)