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Usually the heat exchanger can be normal working temperature to 283 ℃, but the temperature is easy to rust stainless steel bolts. The reason is that, in the high temperature environment, the heat cycle can cause some stainless steel tissue to be non – stainless steel. Therefore, when selecting stainless steel fasteners, the requirements must be met to prevent later loss. The following will introduce the optional materials for the stainless steel fasteners. 300 series stainless steel fasteners 300 – line stainless steel is the most commonly used material for the manufacture of fasteners, joints, pipes and pipes. Among them, 304 stainless steel fasteners are the most. 18 – 8 steel is the nominal content of 300 series stainless steel chromium and nickel. The surface of such materials has excellent corrosion resistance, but if the 304 stainless steel is heated to 199 degrees, the carbon content will decrease the content of chromium. This is due to the formation of chromium carbide in the combination of chromium and carbon at high temperature, and the chromium carbide is not antirust. If 304L stainless steel can be used to alleviate this problem, the carbon content of 304L stainless steel is only about 1 / 3 of the 304 stainless steel. The use of 321 stainless steel or 347 stainless steel can avoid the formation of chromium carbide. 321 stainless steel and 347 stainless steel are titanium and niobium respectively, and their chemical properties are very stable. Since titanium and niobium have a larger affinity for carbon than chromium, they are formed at high temperatures with carbon and niobium, respectively, so that chromium can be retained. So 304, 321, and 347 stainless steel are used to make bolts for 300 series stainless steel. In addition, because the strength of 300 series stainless steel can only be strengthened in cold forming, so when the temperature reaches 283 degrees, the thermal cycle will reduce the strength of fastener to the annealing state. If the degree of intensity is not acceptable, even 321 or 347 should be reconsidered, and in this case, the other materials are selected. 400 series stainless steel The chromium content of the 400 series stainless steel is lower than that of the 300 series stainless steel, but there is no carbon deposition problem, and it can be heat treated. It can be used in the working environment with a temperature of 393 degrees. But because the chromium content is only 12%-14%, it will be corroded in a serious chemical atmosphere. However, the chromium content of the 300 system reaches 16%-20%, and it will not corrode. The other 400 series of stainless steel has magnetic properties. The 410, 416, and 430 series of 400 series of stainless steel are used for fasteners. The use of 304 stainless steel is not suitable for 283 degrees in the operating environment, if the decline in strength of materials close to the annealed state can accept, can choose a stable material 321 or 347 stainless steel and the like, and if the strength requirement is high, and the surrounding environment corrosion is not serious, can use 400 series stainless steel can meet the requirements. Source: China Stainless Steel Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are many metal materials that can be used to make fasteners. Stainless steel fasteners not only have better appearance and better physical strength, but also have advantages such as corrosion resistance, easy welding and manufacturing. Stainless steel fasteners can also be treated with electroplating or heat treatment to get better product performance, and the waste can be recycled and reused completely. The use of fasteners made of stainless steel production, whether in manufacturing, application and processing have very big advantage, so although stainless steel fasteners due to its material cost and the cost is high, but because of its relatively long cycle life, so in all kinds of materials selection of fasteners, is still a cost-effective. When stainless steel is used as raw material, fasteners are heavily dependent on the addition of nickel. However, the price of stainless steel fasteners is also greatly affected by the high price of nickel. Stainless steel fasteners manufacturers, in order to reduce cost pressure and enhance the price competitiveness of fasteners, have searched for alternative materials, and successfully produced low nickel stainless steel fasteners, so that the price of such fasteners is more close to the people. If the fastener is made of stainless steel as the main material, it is necessary to clarify the magnetic problem of the stainless steel. Stainless steel is usually considered to be non-magnetic, but in fact, after austenitic stainless steel is partly processed, it may still produce weak magnetism. Therefore, it is inaccurate to distinguish the quality of stainless steel fasteners with or without magnetism. When selecting stainless steel fasteners, whether the stainless steel material is magnetic can not explain the quality of the products, because some chrome manganese stainless steel is also non magnetic stainless steel. Stainless steel fasteners, such as chromium, manganese and stainless steel, can not replace the application of the 300 series stainless steel, especially in high corrosive medium, and the quality of stainless steel fastener is better. Source: China Stainless Steel Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The common metal bellows are basically made of thin – walled stainless steel welded pipe. It can be used to transport various kinds of industrial gases, such as water, oil, medicine and other fluid medium. It can play an important role in reciprocating movement of pipeline, absorption of heat expansion system, absorption of vibration and adjustment of piping center. It features five main aspects, the first is convenient for construction, because the stainless steel corrugated pipe is a thin-walled tube, total weight, reduce the construction load and construction time greatly; secondly is the corrosion resistance is high, because the main body of the corrugated tube is made of 304 stainless steel or 316L stainless steel, and both use stainless steel joint or the carbon steel joint, excellent sealing performance and good corrosion resistance; stainless steel corrugated pipe has good pressure resistant performance; the materials of various kinds, even with the needs of users and customization; and stainless steel bellows and beautiful appearance, can be. The stainless steel bellows are based on the different wave types, including two kinds, which are circular corrugated tubes and spiral bellows. The pattern of the ring bellows is a tubular shell with a closed circular ring, which is formed in series between the wave and the wave. Circular bellows can be processed by seamless steel pipe or welded pipe. Limited to the processing technology, the length of the single tube is generally shorter than the spiral bellows. But the advantage is that the elasticity is better and the stiffness is low. The spiral corrugated tube is a corrugated tube with a spiral shape. There is a spiral angle between the two adjacent waves. All corrugation can be connected by a spiral line. The stainless steel corrugated soft tube according to use can be pided into metal bellows, bellows, bellows tube heat exchanger, diaphragm and Hengchang metal hose etc.. Metal bellows are mostly used to compensate for pipeline thermal deformation, shock absorption and pipeline settlement and deformation, etc., which are widely used in petrochemical, aerospace, power, metallurgy and other industries. A tubular elastic sensitive element that is connected in a folding and telescopic direction with a foldable wrinkle piece. The opening end is fixed and the seal end is in free state. It is the use of auxiliary spiral spring or reed to increase elasticity. At work, the length of the stainless steel tube is extended in the direction of the internal pressure, and the displacement of the active end can be caused by the pressure. The active end leads the pointer directly to indicate the size of the pressure. Bellows are usually combined with displacement sensors to form pressure sensors that output electricity, and sometimes used as isolation elements. Because of the stretch of ripple tube for volume changes greatly, so the response speed of the Bourdon tube below. The bellows are suitable for measuring low pressure. Source: China Stainless Steel Bellows Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel elbow is a kind of elbow pipe with wide application style, rich angle and composition, and has a very good competitive advantage. Due to the existence of a thin and dense oxidation protection film on the surface of stainless steel, stainless steel has strong corrosion resistance in various water environment, even in the soil. So the elbow pipe made of stainless steel is also suitable for many water quality environments, so we only need to disinfect the water quality without multiple control of water quality, which can effectively save costs. And when using this elbow pipe, there will be no corrosion and excessive seepage. It can ensure the purity and health of the water, avoid the two pollution of the water quality, and also wash with the high speed water flow up to 30 meters per second. The advantages of stainless steel, the high connection strength, strong anti vibration, the connecting parts one-time do firmly and effectively prevent joint loosening, installation is very convenient, and the set of operations without welding wire and stainless steel elbow, long service life. According to the actual corrosion test data, the service life of stainless steel elbow can reach up to 100 years, and stainless steel elbow is not normally maintained when used normally, so its cost performance is very high, and its running cost is relatively low, which is obviously cost-effective. Because the stainless steel elbow has the advantages of watertight, no burst, fire prevention, earthquake resistance and so on, it is very reliable in safety performance, and its thermal insulation performance is good, so it is very suitable for transporting hot water. Stainless steel elbow with connecting reliable safety, convenient construction, sanitation and environmental protection performance, flow pressure loss is small, the system compatibility, can be installed and concealed, free maintenance, economic performance, wide application range, suitable for hot and cold water, drinking water, heating, air conditioning, fire and gas etc. civil low-voltage fluid transport, can also be used for low pressure liquid medicine, beverage, food, chemical industry, transportation. The on-site installation of the stainless steel elbow is very convenient. The installation of 1/3, only welded pipe fittings or wire, can shorten the time of work and reduce a large amount of consumption, and can also prevent leakage of water. In connection with the elbow, the elbow should be controlled and used according to a certain way and principle, with excellent installation characteristics and value. Stainless steel elbows can be used in different fields. Good characteristics and advantages promote continuous promotion and progress, enrich and show good value and function, and do not damage the value in construction. Generally speaking, the stainless steel elbow has been widely applied in many fields and industries. It can ensure the safety and pollution-free of water quality, so that it can meet various requirements.

The performance of duplex stainless steel is generally strong, but it also has weaknesses. Especially, the weakness of high alloy duplex stainless steel containing high amounts of chromium, molybdenum and nitrogen is obvious. One is thermal processing performance, the deformation temperature in thermal processing, because the two microstructure of duplex stainless steel in strength, plasticity and the deformation behavior of different has the difference, it will reduce the thermoplastic properties, and thermoplastic decline will lead to thermal processing performance of duplex stainless steel worse. The other is the cold forming properties. The cold forming properties of the duplex stainless steel are less than those of the chromium nickel austenitic stainless steel, and are lower than some chromium containing ferritic stainless steels. This is related to the low yield strength, large deformation resistance, low elongation, large anisotropy, R value (plastic strain ratio) and n value (cold working hardening coefficient) of duplex stainless steel. Therefore, the duplex stainless steel is usually not suitable for the use of strict cold forming (such as deep drawing). For pipe and tubesheet expansion technology, we must use the larger external force to cause the steel tube yield, so that we can successfully complete the expansion joint operation, in addition, it can also make cold bending, but the resilience is higher. The following features of the lower double phase stainless steel are introduced. The first point is that the yield strength of duplex stainless steel is nearly twice as high as that of austenitic stainless steel, so the amount of deformation needed to be used is lower than that of the latter. When the cold rolling is done, the proper speed and delivery must be selected, so as to reduce the uneven longitudinal wall thickness and rolling. The rate of reducing the surface of the steel tube should not be too large when it is cold drawn. The second point is the middle of the pipe softening using continuous roller hearth type heating furnace and heat treatment furnace duplex stainless steel (water cooling device with exit), do not use electric contact heating, which is not easy to control the temperature, and the heating speed is very fast, easily lead to overheating, the ferrite microstructure content exceed the standard, especially in the rolling of thin walled tube, if the control is not good, it is easy to form bamboo like uneven wall thickness, even if the wall thickness is not too mean. In electric contact heating, thin wall parts rapid warming, cause local overheating, will greatly increase the amount of ferrite, and even the formation of single-phase coarse ferrite, reduced corrosion resistance, acid pickling process after when the site is prone to local pickling, resulting in damage to scrap of duplex stainless steel tube. The third point is the solid solution treatment of finished duplex stainless steel pipes, which is the key link. It not only eliminates the residual stresses in the finished products, but also ensures the proper two phase ratio and the surface quality of the finished products. During heat treatment, we should pay attention to the uniformity of material temperature and enough holding time, so as to avoid stress corrosion caused by insufficient solid solution and high residual stress on the surface of steel pipe. Finally, for the steel pipe, which is mainly used for stress corrosion resistance, the delivery of the solid solution in the pickling state is needed to avoid the abrasive delivery. When the pipe surface is distributed with small cracks and folding defects, when the whole tube is needed to abrade, the steel pipes after grinding must be treated again after solid solution and acid washing. The main reason is that the tangential stress in the residual stress produced by grinding is the main stress to produce SCC damage. Source: China Duplex Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pneumatic valve is made of stainless steel material with pneumatic actuator Pneumatic ball valve, although stainless steel is very much, but the most common stainless steel ball valves are basically made of 304 stainless steel, 316 stainless steel, the characteristics of the pneumatic ball valve is a strong corrosion resistance. A stainless steel pneumatic ball valve closes tightly only with a 90 degree of gas rotation and a very small moment of rotation. The ball valve is characterized by its compact structure, easy operation and maintenance. The stainless steel pneumatic ball valve is widely used in pipelines conveying water, solvent, acid and natural gas. It is also suitable for pipeline transport in medium, such as oxygen, hydrogen peroxide, methane and ethylene, in the medium of bad working environment. More types of stainless steel ball valve, in the form of the structure can be pided into three kinds, the first is the stainless steel floating soft sealing valve, also called floating pneumatic ball valve, stainless steel ball valve ball is floating in the medium under pressure, the ball can generate some displacement and pressed the sealing surface in the outlet end, and to ensure that exit seal. The structure of the stainless steel floating ball valve is relatively simple, and its sealing performance is relatively good. However, the load that the sphere bears the working medium is all passed to the export seal ring, so we need to consider whether the material of the sealing ring can withstand the working load of the ball medium. This structure is mostly used in medium and low pressure stainless steel ball valves. The second kind is the stainless steel fixed ball valve, also called the fixed ball pneumatic ball valve. The ball of the stainless steel ball valve is fixed and does not move after being pressed. The stainless steel fixed ball valve has the floating valve seat. The valve seat moves after the pressure of the medium, so that the seal is pressed on the ball to ensure the seal. In general, and the sphere of the upper and lower shaft with bearings, operating torque, suitable for use in high pressure and large diameter of the valve. The third kind is the stainless steel ball ball valve, also called the elastic ball pneumatic ball valve, the ball of the stainless steel ball valve is elastic. The ball and seat gasket are made of metal material. The sealing ratio is very high. The pressure of the medium can not meet the requirement of sealing. We must exert external force. This kind of valve is suitable for high temperature and high pressure medium. The elastic ball of the stainless steel is an elastic groove on the lower end of the inner wall of the sphere, thus getting the elasticity. When the channel is closed, the wedge head of the stem is used to make the sphere open and the seat press tight to get the seal. Before rotating the ball, the wedge head is loosened first, then the sphere is restored to the original shape, resulting in a small gap between the ball and the valve seat, which can reduce the friction and operation torque of the sealing surface. Source: China Stainless Steel Pneumatic Ball Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

When storing stainless steel plate, it should be placed on a special storage rack. The storage rack should be wood or surface painted carbon steel support or underlying rubber pad, so that it can be separated from other metals such as carbon steel and so on. When storing, the storage location shall be conveniently hoisted and pided into other materials storage areas, and there must be some protective measures to prevent dirt and oil contaminants from polluting the stainless steel. The hoisting of stainless steel plate, to use special sling, sling, such as special clip, prohibit the use of wire rope to avoid scratching the surface, but also in the lifting and placing, try to prevent shock bump cause scratches. When transporting stainless steel materials, we should use the means of transportation to keep the material clean and isolated, not to drag and drag, and not to be scratched and hurt. It is necessary to pay attention to the processing of stainless steel materials. First is the processing area, and the processing area of the stainless steel parts is relatively fixed. Isolation measures should be used for the platform of stainless steel parts, such as rubber pads. Management and processing stainless steel production should be strengthened to prevent damage and pollution of stainless steel. The second is the blanking, the cutting of stainless steel parts by cutting or plasma cutting, sawing and so on. The third is cutting, in shearing, to be separated from the support, and the hopper should also be laid on rubber pads to prevent the scratch of stainless steel material. The fourth is to clean the slags after plasma cutting. In the process of batch cutting, the finished parts should be cleaned in time so as to prevent the pollution of the workpiece. When cutting the material, the clamp should be protected by the rubber, and the oil and residue on the stainless steel workpiece should be cleaned after sawing. When machining stainless steel, stainless steel parts should also be protected when machining, such as vehicle and milling. After finishing operations, oil stains, iron scraps and other debris should be cleaned up. In the process of stainless steel plate forming, in the process of rolling and bending, it is necessary to use effective methods to prevent the scratch of the surface of stainless steel parts. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pipe, as a very common metal material, is widely applied due to the rapid progress of material processing technology. These excellent machining processes help to enhance the performance of stainless steel pipes and meet the needs. But after a series of processing processes, especially after heat treatment, the stainless steel pipe must be cooled. The cooling process is very important for the use of stainless steel pipes, because once any part of the process is wrong or wrong, it will lead to problems affecting the quality of stainless steel pipes, because we should pay special attention to several problems when cooling stainless steel pipes. The first is the degree of stability of stainless steel pipe cold austenitic high hardenability is also great, even if the air cooling can be obtained martensite, but air cooling can cause the surface of stainless steel tool products formed oxidation, and may precipitate eutectoid carbide now, so try not to use air cooling process. For large and complex structure of the stainless steel pipe, in order to reduce the deformation and cracking degree, can do a pre cooling treatment when quenching, but need to control the time, usually according to control the shape of the stainless steel pipe in a few seconds to tens of seconds, but the premise is not two carbon compounds can be precipitated and hard to reduce tool hardness and red, also can not form such as pitting corrosion. The third is that the grading quenching temperature should not be higher than 650, to avoid the transition of pearlite and the precipitation of carbides. The fourth is to take into account that the transformation temperature of the lower bainite is 320-250 degrees C, and the fastest transition temperature is 260 to 300 degrees. So the production is 260-280 to 300 hours. Because the retained austenite temperature after isothermal quenching is more and more stable, four tempering is required. The fifth is the high temperature quenching to 580 to 620 DEG C neutral salt bath, can not use 500 to 550 DEG C nitrate graded cooling, it is the cause of nitrate will hot forming tool oxidation and corrosion, and even the sharp knife burning. The last point is that the stainless steel pipe should be vertically placed in the cooling medium during the quenching operation so as to reduce the deformation of the stainless steel pipe. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

When the stainless steel plate is stretched and formed, the surface of the board will appear rough, and the surface roughness of the stainless steel is called the orange peel phenomenon. The so-called stainless steel plate, orange peel phenomenon is the surface of the stainless steel board presents like orange skin texture, touch, feel very rough, the obvious and common stainless steel plate, smooth surface, there is a certain gap so this is a defect. In the stainless steel plate trading market, there is an orange peel stainless steel plate appearance, while the surface of the stainless steel plate surface of the reason, there are four main types. Here are the reasons and prevention measures. The first reason is that in the process of processing stainless steel plates, the surface of stainless steel plate is not fully polished, which leads to the appearance of orange peel changes on the surface of the stainless steel plate. Therefore, this phenomenon can be prevented by fully grinding stainless steel plate surface. The second reason is that too much on the degree of processing of stainless steel plate, the more the conference led to the surface of the stainless steel plate and sample orange peel, want to a satisfactory solution for processing bigger orange peel phenomenon caused by a stainless steel plate surface, can carry on the processing of stainless steel plate and is going to do fully grinding stainless steel plate, can prevent the surface of the stainless steel plate again from orange peel phenomenon. Another is caused by heat treatment to soften on stainless steel plate processing, to solve this kind of factors lead to the surface of the orange peel, can through the study of the appropriate heat treatment of stainless steel plate, hold good degrees of heat treatment process. The last is that the grain of the raw material is too big. This kind of circumstance, from the perspective of raw materials, the raw material screening, appropriate control of the grain size of raw materials, fundamentally prevent stainless steel plate during the late processing orange peel sample changes. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Because stainless steel plate has high yield point, strong hardness and cold hardening effect, there are many characteristics to be noticed when doing deep drawing. First, because the thermal conductivity of stainless steel plate is weaker than that of ordinary low carbon steel, the deformation force is high. Secondly, when drawing deep, the plastic deformation of the stainless steel plate is hardened and the sheet drawing is easier to wrinkle and the edge pressure is stronger. The third is the springback caused by bending and reverse bending at the fillet corner of the drawing die, which usually causes concave deformation on the side wall of the product, which results in higher dimensional accuracy and shape requirement. The last one is that the stainless steel plate is easy to produce the bond in the drawing process. And how do you solve the problem? The first step is to choose the working parts of die materials better, in order to solve the problem of tumor bond practice shows that, with cast aluminum bronze, aluminum bronze, anti sticking effect is better, the use of tungsten carbide alloy die manufacturing than the service life of the die with Cr12Mov soft nitriding improved several times, also won’t stick to die; and such as the use of code 3054 alloy cast iron, as long as the flame quenching on the surface of the mould, mold will not appear on the surface of tumor adhesion. The surface of the working part of the mold should also be processed. Because the surface quality of the stainless steel drawing die is very high. The lower surface roughness can reduce friction and enhance the adhesion resistance. Therefore, to reduce the surface roughness of the die, the number of molds will also be reduced, which helps to improve the service life of the die. But also for the lubrication of the process, from the characteristics of stainless steel drawing to understand tumor is due to generation of bonding sheet and the mold have direct contact, so the choice of primary point lubricant or coating agent is in sheet deep drawing process of lubricating film can not break from first to last for lubrication. A good effect can be obtained by adding a certain proportion of additives or using solid lubricants in the lubricants. This is mainly to enhance the lubricating ability of lubricant on the surface of metal compounds, sulfur, phosphorus and chlorine to form at high temperatures and the metal surface chemical reaction, formation of iron sulfide, chloride, to strengthen the oil film strength and enhanced adsorption capacity, better lubrication and surface mold products. Solid lubricants are filled into small pits on the metal surface, so that the dry friction contact points are reduced to a minimum. In addition, solid lubricants are highly stable, and can also play a lubrication role at high temperature, and die bonding is not easy. In general, different proportions are selected according to the deformation degree of the product and the actual situation in the production. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The high temperature oxidation resistance is the key performance index of the heat-resistant stainless steel, and it is paid close attention to by the people in the industry. Stainless steel containing special alloy elements is an important factor to enhance and improve the oxidation resistance of the alloy, the prerequisite to guarantee the basic properties of stainless steel material, adding proper amount of alloy elements can improve the alloy oxidation resistance, surface oxidation because it can form a layer of compact protective film on stainless steel surface, so as to enhance the high temperature oxidation resistance stainless steel material. The heat resistant stainless steel 310S is high chromium and high nickel austenitic stainless steel, it not only has relatively good corrosion resistance and mechanical ability, but also has excellent excellent high-temperature oxidation resistance and creep resistance. Therefore, it is also used to make a large number of high temperature furnaces and high temperature components in special environment. Through the high temperature oxidation mechanism of the heat-resistant stainless steel 310S, there is a good breakthrough in the research. The high temperature oxidation test of 310S stainless steel in air was carried out to evaluate its high temperature oxidation resistance. Based on the analysis of the oxidation kinetics gain curve, the morphology, distribution and structure of these oxide films were studied, and the formation mechanism of the oxide film was explained. The test sample is the hot rolled stainless steel 310S plate of the austenitic stainless steel. The chemical composition is 0.055 carbon, 0.50 silicon, 1.03 manganese, 25.52 chromium and 19.25 nickel. The 310S stainless steel samples were cut into 30mm * 15mm * 4mmm. 3 parallel samples were used at each test point, the samples were lapping, and the surface oxide scale and the cutting edge were removed by sandpaper, then washed and dried by ethanol. Prepare the same number of crucibles with the same number of samples and bake them with a resistance heating furnace, so that the residual substances in the crucible can be fully developed and the quality is constant. The high temperature oxidizing specimens were directly placed in the crucible and placed together in a box type resistance furnace for high temperature oxidation. The test atmosphere is air, and the oxidation temperature is 800, 900 and 1000, respectively. The treatment time of each sample is 20, 40, 60, 80, 100, 120 and 140h, respectively. After the oxidation is completed, weighing and recording, the weighing instrument is the balance of the electronic analysis. After the high temperature oxidation test was finished, the oxidation products were analyzed by X ray diffractometer, and then the surface morphology of the oxide film was analyzed by scanning electron microscope and energy dispersive spectrometer. The final results show that the heat-resistant stainless steel 310S has a very good oxidation resistance at 800, 900, and 1000 C. With the prolongation of the temperature, there are different degrees of oxidation aggravation, but the trend of oxidation slows down with time. In addition, with the increase of temperature, the rate of oxidation will be accelerated. The second point is that the oxide film is composed of outer layer of dense spinel MnCr2O4, Cr2O3 and inner SiO2. As the temperature continues to rise, the diffraction peak of MnCr2O4 will increase, and the resultant will also become more. The multi-layer compact structure and the good oxidation resistance of the oxide itself can make the heat-resistant stainless steel 310S exhibit excellent high temperature oxidation resistance as a whole. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The surface of hot-rolled stainless steel plate usually has a thick oxide layer. If chemical oxidation is used to remove oxide layer, it will not only increase pickling time, reduce pickling efficiency, but also increase the pickling cost too much. Therefore, to use other methods to treat the stainless steel plate as an auxiliary process, there are three main pretreatment processes for pickling. The first is the shot peening process, this is a kind of mechanical removal way at the present time most frequently used, it is the principle of using shot peening equipment ejected fine particles of the shot to hit the surface of stainless steel plate, stainless steel plate in order to get rid of the thick oxide layer. After shot peening, some oxide layers will be removed, and the remaining oxide structure on the stainless steel plate will become loose and discontinuous, which is very beneficial for later pickling. The second is alkali leaching process, which includes two kinds of alkaline leaching with oxidation type and reduction type alkali leaching. The oxidized alkali leaching is also called the “salt law”, its mechanism is after alkali treatment for stainless steel oxide refractory iron chromium spinel (FeCr2O4) modified into alkali soluble CrO3, and because of changes in the volume and structure of oxide layer, the oxide layer falling off. Reduced alkali leaching is the strong reducing agent NaH, the oxide of iron, nickel, chromium and other refractory metal oxide or metal oxide reduction becomes low, and let the oxide layer break off, shortening pickling time and enhance efficiency. In the process of oxidizing alkali leaching, a certain degree of Cr6+ pollution will be formed. The reduction type alkali leaching can remove the problem of Cr6+ pollution, and the key material is NaH. Domestic use Potassium Permanganate oxidized alkaline leaching process, while the foreign countries mostly use the leaching of alkali reduction. The third one is neutral salt electrolysis, which takes Na2SiO4 aqueous solution as electrolyte. The stainless steel plate passes through the electric field between cathode and anode, changing cathode and anode continuously, and removing the surface oxide layer after current action. The mechanism of electrolysis of neutral salt, which is oxidized to higher soluble ions by chromium, manganese and iron oxide in the insoluble oxide based, so that the oxide layer is dissolved; second is based on the stainless steel substrate is oxidized to metal ions, so that the spallation of the oxide adhered on the surface of the stainless steel plate. In general, the most common use now is the neutral salt electrolysis process. These pretreatment processes can remove the oxidation layer on the surface of the hot rolled stainless steel plate and reduce the load produced during the pickling. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)