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When fastening parts are used, the stainless steel fasteners will sometimes be locked. However, if the carbon steel fasteners are used, the locking is seldom seen. An important reason is that the stainless steel is soft and the carbon steel fasteners are relatively stiff. Stainless steel materials have good ductility, but there are some differences between hardness and carbon steel. Is there any other reason for that? In fact, it is because the stainless steel material has good corrosion and corrosion resistance. When its surface is damaged, a thin and dense chromium oxide layer will form on the surface to prevent corrosion from developing to a deeper level. When the stainless steel fastener is locked, the pressure and heat between the teeth will destroy and wipe out the chromium oxide layer on the surface of the material, resulting in the direct blocking or shearing of the teeth and forming adhesion. When the sticky situation persists, the stainless steel fastener will be locked directly and completely, and it can no longer be unloaded or locked. This series of continuous movements of blocking, shear, adhesion, and lock death can be done in a very short few seconds. Avoid the stainless steel fasteners have locked the best properties of stainless steel products first and follow the correct operation of the corresponding procedures so I want to. About 304 or 316 stainless steel like materials have good ductility and viscosity, it can be clearly seen in the turning process, such as the 304/316 bar in the car when processing chip it is folded extrusion, and other materials such as brass or iron in the turning process for Clastic debris removal shaped or filamentous. If the use of electric tools in or out when the stainless steel screws and nuts under high torque when the thread contact begins to heat, a point of contact adhesion so as to bring up a large, then the internal thread and external thread bonding formed together locked at the bolt group is scrapped, and even may be installed so that the whole work have become bad. The effective way to reduce or avoid the locking of stainless steel screws is the corresponding method in the process of installation and application. The protection of thread is controlled in semi-finished products, rubbing teeth and finished product transportation packages. No matter whether users use electric tools or overload torque or stainless steel screws and nylon lock nuts, they will not lock. They are exactly the same as carbon steel fasteners. This can reduce the loss to the lowest or even completely without changing the installation tools and installation methods in the process of use. In fact, the cost of this kind of stainless steel screw anti lock solution is controllable and cheap, it will only increase a small amount of extra cost or even optimize, and no additional cost will be needed. Source: China Stainless Steel Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

As the demand for stainless steel materials is more and more widely used, stainless steel welded pipes, as one of the applied varieties, are also widely used in various industries. As the stainless steel industry welded pipe, because of the different surface treatment, there are two kinds of welded pipe and polished pipe. Below are the principles and advantages and disadvantages of the two kinds of welded pipes. The welded pipe with welding seam is welded by automatic welding, one side welding is formed on double side, and the weld on the pipe is smooth and smooth. Because the pickling pipe is made from the first grade stainless steel plate, the surface of the stainless steel welded pipe is consistent with the surface of the original plate. Polishing by hand welding pipe is formed by molding, polishing processing, surface passivation layer and cast weld pipe, stainless steel pipe surface showed a higher degree of brightness. Below, look at the contrast between the stainless steel belt welded pipe and the polished pipe. First, the wall thickness of the welded pipe with welding seam is more uniform and has higher bearing pressure. The wall thickness of the raw material will be thinner, especially in the weld area, by artificial polishing. The thinner the thickness of the weld wall, the smaller the bearing capacity of the weld. Secondly, the welded pipe with weld seam pickling ensures the performance of austenitic stainless steel. Most stainless steel welded pipes are austenitic stainless steel used as raw materials, such as 201, 202, 304, 316L stainless steel and so on, while austenitic stainless steel is non-magnetic or weak magnetic. The chemical composition fluctuates after polishing, which makes the austenitic stainless steel magnetic. The third is high corrosion resistance of welded pipe with seam pickling. The polishing pipe eliminates the passivation layer generated after pickling of raw materials, which results in the rusting of the welded pipe in normal environment, thus weakening the corrosion resistance of the stainless steel pipe. In addition, the quality stability of the welded pipe with weld seam pickling is better. The polished welded pipe is a product popularized from the Wenzhou area. But because most of the Wenzhou area of stainless steel pipe used raw material is two grade materials or recycled material, to cover up the two grade stainless steel material surface spray, heavy leather and corrosion point must be polished; even some in order to reduce the cost of materials, full use of waste recycling in a pipe joint, a plurality of transverse seam. This kind of polished pipe is not guaranteed on the quality of the raw material, and the quality of the pipe itself is more difficult to ensure. The last point is that the practicability of the welded pipe with weld seam pickling is better. In terms of industrial welded pipe, stainless steel welded pipe is mainly used for its own mechanical properties, corrosion resistance and channel performance. For stainless steel welded pipe, its surface gloss is relatively low, which, of course, besides decorative pipe and sanitary welded pipe. Therefore, the industrial welded pipe is not necessary to use the high cost but not the performance of the polished welded pipe. Source: China Stainless Steel Welded Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Nowadays, duplex stainless steel is widely applied in various industrial fields, such as pulp and paper industry, oil and gas industry, chemical industry, dangerous goods transportation, pharmaceutical and food processing, and construction industry. In these industries, the duplex stainless steel is mainly used for the preparation of reaction containers, industrial equipment and various kinds of conveying pipes. Compared with many other materials, duplex stainless steel is generally recognized as the best cost effective material. It effectively fills the blank of intermediate austenitic stainless steel such as 316 and high alloy austenitic stainless steel. It is generally believed that the application of duplex stainless steel is due to the material can resist chemical corrosion, corrosion medium such as urea fertilizer and organic acid production, production and processing of natural gas containing hydrogen sulfide will encounter, but more critical applications for those who do not have enough resistance to pitting corrosion of austenitic stainless steel and chlorine ion hot water solution of stress corrosion cracking the properties, such as heat exchanger, condenser and various types of containers and other equipment. For duplex stainless steel, there are limitations and requirements for the following safe use. The first is to control the phase ratio. The most suitable proportion is the ferrite phase and the austenite phase, each half of which must be occupied. The number of a phase can not be greater than 65%. The second is to master the transformation rule of the duplex stainless steel, and be familiar with the constant temperature transformation and the continuous transformation of the ferrite in each steel. This is also the key to correctly guide the process of heat treatment and hot forming for duplex stainless steel. The sensitivity of duplex stainless steel to brittle phase is far more sensitive than austenitic stainless steel. In addition, the continuous temperature range of the duplex stainless steel is from -50 to 250. The duplex stainless steel should be cooled quickly after the solid solution treatment. The slow cooling will lead to the precipitation of the brittle phase and reduce the toughness and corrosion resistance of the steel. It is important to pay attention to the elimination of stress treatment at 650-800 C, usually used for austenitic stainless steel, usually with a solution annealing treatment over 950 centigrade. If in the surfacing of low alloy steel duplex stainless steel after 600-650 DEG C to the overall stress relieving, we must consider the toughness and corrosion resistance decrease, shorten the heating time as far as possible in this temperature range. It is also necessary to be familiar with the welding rules of duplex stainless steel and not to use all kinds of austenitic stainless steel welding technology. The key of welding is the control of line energy and interlayer temperature. The correct selection of welding materials is also very important. The heat affected zone of welding fusion line should maintain a certain amount of austenite so that the performance of the welded joint is equivalent to or close to the parent material. The last point is the selection of duplex stainless steel in various corrosion environments, the need to pay attention to the corrosion resistance of stainless steel is limited, even if the double phase stainless steel has better resistance to local corrosion, but for any type of double phase stainless steel, the model is a suitable medium range of conditions, including temperature medium, pressure, concentration and pH value, so need to be carefully selected according to actual use. In order to meet the requirements of actual conditions, it is necessary to do some corrosion tests in actual media or hang up test under field conditions when necessary, and even more, we can do the test of analog devices. Source: China Duplex Stainless Steel Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In all applications of stainless steel, stainless steel screws are a very inconspicuous but closely linked way of application. The stainless steel is a very excellent alloy metal. There are three main types of metal corrosion and usually can approach are composition design of contact surface of metal and metal dielectric properties, its application environment and external medium, change the stainless steel itself, if you want to use the complete corrosion resistance of stainless steel to produce stainless steel screws, unless special application requirements, or from the angle of economy it is not cost-effective nor practical, and put the screws on the surface and easy to cause the corrosion of the environment medium complete isolation, the feasibility is very low. Improve the composition structure of stainless steel can increase the corresponding resistance in some situations, but as the application of less ordinary stainless steel screws basically is not taken in the optimization of steel components to meet the demands for use, and even if the optimization cannot completely screw can meet the perse and harsh environment of demand. Therefore, for stainless steel screws, the most widely used and the most suitable corrosion resistance method is to make surface treatment of the material. Stainless steel screw surface corrosion prevention technique refers to the use of various methods on the surface of stainless steel materials with common protective layer, and its role is to isolate the metal medium environment and corrosion resistance from the formation to suppress the corrosion process, or reduce the corrosive medium and the stainless steel material surface contact degree, so as to avoid or the purpose of reducing corrosion. The requirements for the protection layer of the stainless steel screw surface are required as described below. The first is to have good corrosion resistance, wear resistance and high hardness. Secondly, the structure of the stainless steel material used is dense, perfect and small pore. The third point is that both the surface protection layer and the matrix metal should be separated and have good bonding force. The last point is that the surface protection layer should be spread evenly and with a certain thickness. The surface protection layer of stainless steel usually includes two kinds of metal coating and non-metallic coating. The metal coating means the metal or alloy with strong corrosion resistance is used as the protective layer on the stainless steel surface, and the coating is also called the coating. There are many ways to produce metal coating, the most commonly used is electroplating, then molten metal plating and chemical surface treatment. Instead of metal coating refers to the use of organic polymer materials such as paint or inorganic material such as ceramic, forming a protective layer on the surface of stainless steel material, the protective layer can be stainless steel and the external environment medium is completely isolated, also can effectively prevent the substrate from corrosion of stainless steel. Source: China Stainless Steel Screws Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

904L stainless steel plate is the gold of a high alloy austenitic stainless steel carbon content is very low. It is specially developed for a highly corrosive environment. At first, its role was to corrode the environment that was resistant to dilute sulfuric acid. As it has been successfully tested, 904L stainless steel is now standardized in many countries and is identified as being able to make pressure vessels. In terms of performance, 904L stainless steel plate has excellent resistance to pitting and crevice corrosion, stress corrosion cracking and intergranular corrosion resistance as well as other common chromium nickel austenitic steels, and has good machinability and solderability. In hot forging, the maximum heating temperature can reach 1180 degrees C, and the minimum stopping forging temperature is not less than 900. Its thermoforming can be carried out within a temperature range of 1000 – 1150 degrees C. Its heat treatment process is 1100 – 1150 C, and it is cooled fast after heating. Although it can be welded with a general welding process, the most suitable welding process is manual arc welding and tungsten arc welding. When manual arc welding is used to weld stainless steel plate less than 6 mm, the diameter of the welding rod is less than or equal to 2.5 millimeters. When the plate thickness is higher than 6 mm, the diameter of the welding rod is less than 3.2 mm. When heat treatment is needed after welding, it can be treated quickly after heating at 1075 – 1125 C. The filler metal can be used for the use of tungsten electrode in argon arc welding, and the weld is treated by pickling and passivation. The metallographic structure of 904L stainless steel plate is completely austenitic. Compared with ordinary austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and alpha phase. Because the carbon content of 904L stainless steel is very low, the highest is only about 0.020%, so in the ordinary heat treatment and welding, no carbide will be precipitated. This eliminates the risk of intergranular corrosion after ordinary heat treatment and welding. Because of the high content of chromium, nickel and molybdenum and the addition of copper elements, 904L can be passivated in the reductive environment, such as sulfuric acid and formic acid. The high nickel content also has a slower corrosion rate in the active state. In pure sulfuric acid in the concentration range of 0-98%, the use temperature of 904L stainless steel can be as high as 40 degrees C. In the pure phosphoric acid in the 0-85% concentration range, its corrosion resistance is very good. In the industrial phosphoric acid produced by wet process, the effect of impurities on corrosion resistance is great. In all kinds of phosphoric acid, the corrosion resistance of 904L stainless steel is better than that of ordinary stainless steel. In strong oxidizing nitric acid, compared with steel high alloy containing molybdenum, corrosion resistance ability is weak. In hydrochloric acid, the use of 904L stainless steel is limited to a lower concentration of 1-2%. At this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has a high resistance to point corrosion. The anti crevice corrosion ability of the chloride solution is also good. The high nickel content of 904L reduces the corrosion rate at the jute pit and the gap. Ordinary austenitic stainless steel can be sensitive to stress corrosion in a chloride rich environment at temperatures above 60 degrees Celsius, and this sensitization can be reduced by increasing nickel content in stainless steel. Because of high nickel content, 904L has high resistance to stress corrosion cracking in chloride solution, concentrated hydroxide solution and hydrogen sulfide rich environment. The field of application of 904L stainless steel plate is mainly concentrated in the industrial field. For example, petroleum, petrochemical equipment, reactor in petrochemical equipment and so on. The storage and transportation of sulfuric acid, such as heat exchangers, etc. The main parts of flue gas desulfurization unit in power plant are the tower body, flue, gate plate, inner part, spray system and so on. There are also the scrubber and fans in the organic acid treatment system. Source: China 904L Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The main components of stainless steel material is iron chromium alloy and other trace elements. Because of the excellent performance of stainless steel materials, and the corrosion resistance is generally stronger than other metals, and is still more beautiful and durable. However, although stainless steel materials have good corrosion resistance, they are not never rusty. In fact, the stainless steel plate has a layer of passivation film, which is a stable form of oxide. If the stainless steel plate is exposed to the corrosive environment, the surface of the plate will produce electrochemical reaction or chemical reaction, that is, to withstand the corrosion evenly. Stainless steel plate passivation film, where the corrosion resistance is weak, will generate pitting reaction due to self-excited reaction, and produce small pores. If chlorine ions are encountered, there will be very strong corrosive solutions to accelerate the rate of corrosion reaction. In addition, there will be intercrystalline corrosion cracking in the stainless steel. All kinds of corrosion will destroy the passivation film of the stainless steel plate. Therefore, in order to ensure the beautiful surface of the stainless steel plate products and prolong the service life, we must maintain regular maintenance. In the use of stainless steel products, we need to pay attention to the following points. The first is the attention not to scratch the surface phenomenon must be in the stainless steel surface cleaning, do not use bleach containing abrasive and lotion, do not use a steel ball or a grinding tool, and to remove the washing liquid in the washing at the end to use clean water rinse stainless steel plate. If there is dirt on the surface of stainless steel and dirt that is easily removed, it can be washed with soap, weak detergent or warm water. When removing the trademark and sticker of the stainless steel plate, we should use warm water and weak detergent to clean it, or use alcohol or organic solvent to scrub. If the stainless steel plate is contaminated with grease, oil and lubricating oil, it can be cleaned with soft cloth and then washed with neutral detergent or ammonia solution or special detergent. If the stainless steel board with all kinds of acid bleaching agents such as adhesion, should immediately use water to wash, and then use the ammonia solution or neutral carbonated soda solution immersion, use neutral detergent or water washing etc.. If there is a rainbow grain on the stainless steel surface, it is in fact too much use of detergent or oil caused by the use of warm water neutral detergent in order to wash away. If it is the rust caused by the dirt, 10% nitric acid or abrasive detergent can be used to wash, and special washing drugs can be used for washing. As long as the correct maintenance method is adopted, the service life of the stainless steel material can be increased and the gorgeous surface effect can be maintained for a long time. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In fact, stainless steel pipes will not rust, but rust resistance is very high, so it is very difficult to rust, but if the storage method is not appropriate, the rust will happen. This paper will talk about how to keep it as long as possible to make the stainless steel pipe in the best condition. Choose the right place The place suitable for keeping stainless steel pipes should be clean and clean and the drainage is unobstructed, and there is no harmful gas or dust in the vicinity of the factory. In the storage warehouse, the stainless steel pipe should not be stacked with acid, alkali, salt, cement and other materials that easily corrode stainless steel pipes. To avoid confusion were piled up, different types of stainless steel pipe, avoid contact corrosion; pipe fittings must have cover cushion, some thin pieces or high price and easy corrosion, or need to be stored in storage; the warehouse according to the geographical conditions selected, usually use ordinary closed warehouse, there is a roof walls, doors and windows tightly, a ventilation device for warehouse; warehouse environment is sunny rainy day can close attention to ventilation, moisture. Reasonable stacking advanced first place Stainless steel pipe stacking principle is required in the stacking stable, safe condition, do according to the palletizing varieties of different specifications, different varieties of materials to avoid confusion with each other are stacking, corrosion, prevent stack corrosive goods store near the end of the stack to the pad material; high, strong, smooth, avoid stainless steel pipe damp or deformed; the same material in storage respectively stacking, convenient implementation of advanced first principles; the open dumps pipe must have wood pad or stone, stack face slightly tilted, convenient drainage, and placed flat note material, to avoid bending deformation; on the stacking height, the manual operation can not be higher than 1.2m, the mechanical operation is not higher than 1.5m, pile width not greater than 2.5m; between the stack and leave the stack channel, check road is usually 0.5m, and The channel is determined by the size and material transport machinery, usually 1.5-2.0m; pile pad high, if the warehouse is Chaoyang cement floor, then pad high 0.1M on the line; and if it is mud, to pad 0.2-0.5m. And if it is outdoors, then the cement ground to pad 0.3-0.5m, if the sand mud pad 0.5-0.7m. Packaging and protective layer of protective materials The preservative or other plating and coating is applied before the steel mill of stainless steel pipe is put out. This is an important measure to avoid rust of stainless steel pipe. It is necessary to protect and avoid damage during transportation and handling, and it can extend the storage period of stainless steel. Keep the warehouse clean and strengthen the material maintenance Stainless steel pipe material in storage before the need to pay attention to avoid the rain or rain or have to sneak into the impurities, dirty materials according to the nature of use other ways to clean, if high hardness can use wire brush, you can use the low hardness of the cloth, such as cotton fabric cleaning; stainless steel pipe after storage need regular inspection, if found it should promptly remove rust, rust layer; usually steel surface to remove in the net, without oil, but for high quality steel, alloy thin plate, thin wall stainless steel pipe, alloy steel pipe, rust inside and outside surface of it are coated with anti rust oil after storage; for serious corrosion of stainless steel pipe, do not save too long time in use after cleaning as soon as possible. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are four kinds of stainless steel seamless steel pipe production methods: hot rolling, hot extrusion, cold rolling and cold drawing. Their production characteristics from plastic deformation resistance, and spread, several aspects of this application and the sensitive degree of thermal conductivity and oxidation resistance of observation. The following are described in detail. Plasticity Martensitic stainless steel is very easy to perforate at high temperature when it is a single austenite structure, but the perforation of the martensitic stainless steel is obviously reduced if it contains two phase tissues. The heating temperature of stainless steel pipe is usually 1130-1160 degrees, and the temperature of the furnace tail is below 900 degrees. The final rolling temperature is greater than the critical point transformation temperature. The low carbon content is higher than 850 degrees, and the high carbon can not be greater than 925 degrees. Martensitic stainless steel increases with the increase of carbon content, and the strength and hardness of stainless steel will also increase significantly, but the plasticity will weaken. Therefore, it is best to use the mandrel to pull out when cold drawing, because it is easy to burst after empty drawing. The high temperature plasticity of austenitic stainless steel is related to the residual alpha phase. Usually the plasticity decreases with the increase of the alpha phase. In addition to alpha phase, there are other residual phases in austenitic stainless steel, such as various kinds of carbides and intermetallic compounds. The plasticity of the superfluous relative stainless steel will have an effect, and the extent of its influence depends on the quantity and state. The plastic properties of the stainless steel material will be greatly deteriorated by the reticular formation at the grain boundary during heating. The ductility of austenitic stainless steel is low at high temperature, and the deformation resistance of the stainless steel will become larger. The reasonable deformation parameters and temperature parameters should be paid special attention to in the use of oblique piercing. Because ferritic stainless steel is a single phase structure and no phase transformation occurs. Therefore, the grain growth is serious when the heating time is long and the temperature is high, which will significantly weaken the plasticity of stainless steel. The maximum heating temperature of the stainless steel pipe billet is 1000-1060. In this range of temperature, stainless steel will have excellent plasticity. The heating temperature before the cold – drawn hammer is 700-850 degrees C, and the carburization should be avoided and the water quenched after the hammer. Because ferrite chrome stainless steel will have room temperature brittleness, cold processing performance is relatively weak, cold drawing is easy to crack and pull off, so it is best to draw at a certain temperature, and the speed of pulling and pulling is not too large. When the cold rolled ferritic stainless steel pipe is rolled, the deformation degree of the stainless steel pipe is not higher than 40%-48%. According to the grain refinement degree, the degree of deformation can be raised to 55%-65% in the following channel. In order to prevent cracks in the stainless steel pipe when rolling, the temperature rise of the stainless steel pipe is favorable when rolling, so in most cases, when the stainless steel pipe is rolled, there is no need to use the emulsion cooling tool and metal. Deformation resistance Austenitic and martensitic stainless steels have large deformation resistance, work hardening tendency is also large, and the recrystallization speed is slower at high temperature, so the cold rolling stainless steel needs special attention to equipment and motor capability. Both ferritic or semi ferritic low carbon stainless steel and ordinary carbon steel have similar deformation resistance. Spread Stainless steel spread greatly, the spread degree of martensitic stainless steel is 1.3 times of carbon steel; austenitic stainless steel is 1.35-1.5 times that of ferritic stainless steel is 1.55-1.6 times. Therefore, it is necessary to pay attention to control the transverse deformation and take a relatively small ellipticity. Cold and hot rolling pipe groove ovality is higher, and to take the small pass deformation, so as to avoid the above defects, in the absence of tension reducing when the stainless steel pipe wall thickness is larger, and the reduction of the groove ovality mill to get bigger. The sensitivity of the corresponding force The ferritic stainless steel has the normal temperature brittleness, the cold working sensitivity is high, the stress sensitivity is low during hot rolling, and the water quenching can be carried out after rolling. The sensitivity of martensitic stainless steel to crack is higher, and the cooling should not be too fast after hot rolling. Austenitic stainless steel has low sensitivity to crack and can be quenched after hot rolling. Thermal conductivity The low temperature thermal conductivity of stainless steel is poor, but the coefficient of linear expansion is greater than that of carbon steel. In order to ensure the quality of heating, low temperature (<800 C) is selected for slow heating. Antioxidation Because the stainless steel has certain antioxidant properties, the iron oxide skin formed by heating is low. However, there are chromium and nickel oxide in iron oxide skin, which is very dense, and it is difficult to acid pickling during cold processing. Often use HF+HNO3 to do acid washing or alkali acid compound acid washing. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

A stainless steel pipe with a diameter of less than 219mm is used in continuous roll forming, which is basically similar to that of a high frequency welded pipe. When the diameter of the tube is greater than 219mm, the pressure forming or spiral welding is used. The tube diameter is less than 4.76mm, and the tube is drawn by drawing after welding. The welding technology mainly includes high frequency welding, tungsten electrode inert gas protection welding, laser welding and electron beam welding. High frequency welding can not ensure the welding quality of the weld, but the welding speed is relatively large, it is suitable for the production of ordinary structure and decoration of stainless steel welded pipe. Most of the stainless steel welded pipes are combined with argon arc or argon arc welding and plasma welding. The stainless steel welded pipe for decoration requires grinding and polishing on the surface of the tube. The stainless steel welded pipe used in chemical machinery and boiler heat exchanger requires the welding of the inner wall of the pipe to be leveled. The weld structure is disposed by solid solution and must be equipped with the weld quality monitoring and nondestructive testing system. Argon arc welding stainless steel welded pipe production process sequence is plate coil longitudinal shear, strip steel, uncoiling, leveling, cutting head and tail butt welding, looper, forming, argon arc welding, welding, puncture, cooling, sizing, eddy current inspection, and finally sawing. But after cutting stainless steel pipe, stainless steel pipe according to use also pided into three kinds, one is without heat treatment and cold drawing pipe by straightening, flat, pressure, inspection, packing and storage; secondly to heat treatment of welded pipe after degreasing, bright heat treatment, straightening, ultrasonic inspection, flat, water pressure, inspection, packing and final storage; the third is to drawing pipe after degreasing, swaging, annealing, straightening, pickling, lubrication, drawing, cutting head, degreasing, bright annealing, finishing, inspection, packing and storage of the final. At present, a new welding technology has appeared in stainless steel welded pipe, that is, multi torch welding with multiple electrodes, or combination of argon arc welding and plasma welding. Multi torch welding is suitable for welded pipe with wall thickness greater than 2mm, its welding speed is 3-4 times faster than single torch welding, and the quality of pipe after welding is also optimized. Besides, adding hydrogen to 5%-10% and adding high frequency pulse welding power in argon can effectively enhance the welding speed. In order to ensure the quality of welding, the automatic tracking device for welding seam, arc voltage automatic control system and computer controlled welding process are used. Remove the thorn inside welding methods are the inner gas holder, droplet wall filled with inert gas to hold the melt pressure, to ensure that no sagging, so as not to generate welding spines; followed by wall hammer technology for diameter less than 30mm diameter pipe; the last is the inner wall of rolling technology for diameter larger than the diameter of 50mm welded pipe; decorative tube to polishing equipment with high efficiency, to increase the degree of surface finish of stainless steel welded pipe. Source: China Stainless Steel Welded Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

At present, most of the water pipes are concealed and pipe wells. If the material selection is wrong, it is likely to cause huge losses. The common water supply materials include stainless steel pipes, copper pipes, galvanized pipes, composite pipes and plastic pipes. Next, we will compare these materials to see which material is the most suitable. Intensity aspect The most used in stainless steel pipe is 304 or 316 stainless steel, which can meet most of the water treatment and transportation requirements. The tensile strength of the 304 stainless steel pipe is 2 times that of the ordinary steel pipe, about 4 times of the copper pipe, and more than the 8-10 times of the plastic pipe. As the strength of the material determines whether the water pipe is firm and reliable, it is also the most important requirement for the water supply of the building. And under the external force impact, the stainless steel pipe will not leak, and the leakage rate of copper pipe and plastic pipe is higher, and it will be easily damaged by construction or two time decoration. Thermal expansion and thermal expansion The thermal expansion coefficient of the stainless steel pipe is about the same as that of the copper pipe, which is 1.5 times that of the ordinary steel pipe, and the heat expansion and cold shrinkage of the stainless steel pipe is still relatively slow. The expansion coefficient of the plastic pipe is too large, which is fatal and is not suitable to be used as a heat pipe. Under the condition of environmental temperature change, the plastic pipe can also easily produce the hidden danger of leakage and so on, especially in the concealed engineering. The composite pipe has two different kinds of material expansion coefficient, which causes the joint to crack easily, which makes the pipe easier to burst. The thermal conductivity of stainless steel pipe is 1/25 of copper pipe, 1/4 of ordinary steel pipe, very suitable for hot water transportation, and the thermal insulation performance is much better than copper pipe. Corrosion resistance One of the best advantages of stainless steel pipes is the excellent corrosion resistance, which is the best of the five pipes. Because the stainless steel will produce passivation and oxidant to form a layer of dense tenacity the chromium oxide protective film on the surface of Cr2O3, can effectively prevent further oxidation reaction. Other metal pipes are far from stainless steel in corrosion resistance. Health and environmental protection performance The sanitary properties of stainless steel pipes are excellent, which can ensure that the water quality does not have all kinds of strange problems, nor does it smell or foul. It does not precipitate harmful substances, ensure the purity of the water, and is healthy and harmless to the human body. Stainless steel pipe not only in the food industry including beverages, dairy products, brewing, pharmaceutical industry, and other industries and long-term use of tableware cookware has become standard timber in these industries, but also a large number of materials used in the safety and cleanliness requirements of high medical body implants such as various stents, artificial joints and steel nail body, and become a standard material requirements for cleanliness of clean room of semiconductor industry’s extreme. Therefore, with the continuous improvement of water quality and the strict regulation of regulations on hazardous substances in water pipes, stainless steel pipes become the best choice for transporting high-quality water. Price Although the price of stainless steel pipe is higher than that of other pipes, it is very limited, but the material performance is much superior, and it also greatly improves the grade of the pipe. In fact, the selection of stainless steel water pipes is much more than initial investment, but the life cycle cost is very low, which is the absolute advantage of stainless steel compared with other materials in terms of economy. Source: China Stainless Steel Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Improving the surface quality of stainless steel pipelines, including improving the surface morphology and structure, and reducing the number of layers, the common surface treatment methods at present are mechanical drawing, mechanical lapping, polishing and burning. Mechanical drawing The mechanical drawing is to increase the surface roughness of the pipeline by using the plug bolt precision cold drawing, which can improve the surface structure of the pipelineline, but it will not improve the shape, energy level and the number of the intermediate layer of the stainless steel pipeline. This is one of the most basic surface treatment processes, and the roughness of the process is also the basis for other more complex surface treatment processes. Plume polishing This way of treatment is most commonly used to improve the surface brightness of decorative stainless steel tubes. Although the Ra value may be very good, many cracks can be seen under the electron microscope, the actual surface area is enlarged, and there will be separate ferrite and martensite structure. The surface of a stainless steel tube is mixed with a lot of impurities, such as abrasive particles. In addition, because of the use of the polished paste, a lot of energy is stored in the sunken, resulting in the increase in the number of media. Mechanical grinding Mechanical attrition is the way to improve the surface roughness of stainless steel pipelines by precision grinding. It can optimize the surface structure of pipelines, but it will not improve the shape, energy level and the number of interlayers. Pickling or passivation After pickling or passivation, the stainless steel pipelineline will not increase the surface roughness, but it can remove the residual particles on the pipeline surface and reduce the energy level, but it will not reduce the number of interlayers. bright annealing The high temperature heat treatment of stainless steel pipelines under hydrogenation or vacuum can not only eliminate the internal stress of pipelines, but also produce a passive film on the surface of stainless steel pipelines, thereby improving the morphology and structure, reducing the energy level, but it will not increase the surface roughness. Subelectrochemical polishing This method is coupled with a surface treatment process based on BA on the surface of the electrolytic polishing process is mild, so as to try to reduce the surface area, and thick passivation film, in order to improve the corrosion resistance performance, optimization of surface morphology of stainless steel tube and a lower energy level. Although the surface of stainless steel tube after such treatment is not bright, it also improves the surface quality to a large extent, and does not produce particles and reduce the composition of iron and iron oxide on the surface. Electropolishing Through electrochemical polishing, the surface morphology and structure of the stainless steel pipeline can be greatly improved, and the actual area of the tube surface can be reduced to the maximum. The surface of the stainless steel tube is a fully protected chromium oxide film, and its energy is close to the normal level of the alloy, and the quantity of the medium will be reduced to the lowest. Source: China Stainless Steel Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are some technological difficulties in the actual welding of duplex stainless steel 2205, but in fact, if we grasp 2205 of the related material characteristics, many problems will be solved when welding is processed. Here are the following aspects. First, compared with the first generation duplex stainless steel, 2205 has further increased the nitrogen content, and enhanced the stress corrosion resistance and pitting corrosion resistance of the material in acid medium with high chloride concentration. Nitrogen is a strong austenite generating element. Adding into duplex stainless steel can not only enhance the strength of the material, but also damage the plasticity and toughness of stainless steel, and also inhibit and delay the precipitation of carbide. Secondly, we need to understand the organizational characteristics of 2205. Under room temperature, the austenite and ferrite structure are about half of the solid solution, so 2205 has two phase organization characteristics. It not only preserves the low thermal conductivity, corrosion resistance, crevice corrosion and chloride stress corrosion resistance of ferritic stainless steel, but also possesses excellent toughness of austenitic stainless steel, low brittle transition temperature, intergranular corrosion resistance, excellent welding and excellent mechanical properties. The weldability of the duplex stainless steel 2205 is good, which is reflected in the low sensitivity of both cold and hot cracks. No heat is needed before welding, and no heat treatment is needed after welding. Because the nitrogen content is high, the single phase ferrite tendency of heat affected zone is also low. If we choose the right welding material, we can control the welding energy effectively, and the welding head has excellent comprehensive performance. The thermal crack sensitivity of 2205 duplex stainless steel is much less than that of austenitic stainless steel. This is because the nickel content is small, it is easy to produce low melting point eutectic impurities very little, and it is not easy to form a low melting point liquid film. In addition, the grain has no risk of rapid growth at high temperature. During the welding process of the duplex stainless steel, a series of changes in the metallographic structure of the weld metal and the heat affected zone are produced by the influence of the heat cycle. At high temperature, the microstructure of all duplex stainless steel is completely formed by ferrite structure. Austenite microstructure is precipitated during cooling process, and there are many factors that affect the austenite microstructure. Thermal cycling is the most important feature in the process of duplex stainless steel welding. It is manifested that the welding thermal cycle will have great influence on the microstructure of welded joints, regardless of whether the weld or heat affected zone will undergo phase transformation, which will greatly affect the performance of welded joints. So, it is necessary to 2205 welding process of multi pass welding, with subsequent heat treatment on the weld bead before the role of weld metal in ferrite austenite transformation into further, become the dominant two-phase structure of austenite; thermal shadow adjacent welds in the austenite ring is in effect and increased. You can also refine ferrite grain, reduce carbides and nitrides from grains and grain boundaries, so as to improve the performance of welding joint microstructure. Source: China Duplex Stainless Steel Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)