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The stainless steel water pipe does not mean that it will not rust, but it is not easy to rust with respect to iron and copper pipes. A good quality stainless steel water pipe for a dozen years is still not a big problem, but it should be used well. The stainless steel water pipe is not easy to rust, because the stainless steel pipe is nickel-chromium alloy steel. After the nickel-chromium content reaches a certain condition, a protective film is formed on the surface of the steel pipe to protect the steel pipe from rust. However, once the external force or corrosive environment destroys the protective film, the steel pipe is easily rusted. The six types of rust that are common in stainless steel water pipes and their treatment are as follows: 1. Rusted by dissimilar metals Here, it refers to a dissimilar metal such as iron that is easily rusted. It is caused by iron powder iron cutting. If the situation is not serious, it can be wiped directly with sponge or cloth with neutral detergent or soapy water. However, if the situation is serious and brown rust has been formed, it will be used on the market. A special cleaning agent or a 15% sulfuric acid dilution is used for cleaning. 2. Attachment to rust caused by harmful components in the exhaust Under the influence of harmful components contained in automobile exhaust, air-conditioning, or factory exhaust, stainless steel pipes are prone to rust spots. The processing can be handled in the first case. However, if in this environment, it is necessary to do 2-3 times of comprehensive cleaning work every year. 3. Rusting due to salt adhesion In the coastal area, the front side is blown by the sea breeze, and the 304 stainless steel pipe will also generate red rust in a short period of time. Moreover, it rusts faster than other areas, and the treatment method is the same as the first case. In the coastal area, when using stainless steel exteriors, it is desirable to use stainless steel pipes of 316 material with higher corrosion resistance. 4. Rusting caused by attached cleaning solution If it cannot be removed with a neutral detergent, use a cleaning solution to remove it. 5. Rusting due to fingerprints or hand scales If it cannot be removed with a neutral detergent, use a sponge, cloth, etc., with an organic solvent (alcohol, acetone, light oil, etc.) to wipe. If this method is still not completely removed, use stainless steel with a cleaning solution to remove it. In short, after cleaning various cleaning methods, it is necessary to use clean water for final cleaning. 6. Contamination caused by surface protective film Wipe with a sponge, cloth dampened with a water-soluble neutral detergent, or alcohol. If it is still invalid, use a thinner and light oil to remove it. Rinse thoroughly with clean water after washing. Source: China Stainless Steel Water Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The metal content of different materials in stainless steel welded pipes are different, and the application is very different. The 316 and 317 stainless steel welded industrial tubes contain molybdenum (Mo), which is superior to the 304 stainless steel industrial welded pipe in the marine and chemical industry environments. Among them, 316 stainless steel extends from low carbon stainless steel 316L, nitrogen-containing high-strength 316 stainless steel thick-walled pipe and high-sulfur free-cutting stainless steel 316F. And 321 , 347 and 348 are titanium (Ti), niobium (Nb) and tantalum (Ta) respectively; as the yttrium-stabilized stainless steel, it is suitable for use as a welded member at a high temperature. Corrosion resistance of various stainless steel welded pipes: 304 is a versatile stainless steel welded pipe that is widely used to make equipment and parts that require good overall performance (corrosion resistance and formability). 301 stainless steel exhibits significant work hardening during deformation and is used in a variety of applications requiring higher strength. 302 stainless steel is essentially a variant of 304 stainless steel with a higher carbon content, which allows it to achieve higher strength through cold rolling. The 316 stainless steel thick wall tube is a high silicon content stainless steel with high resistance to high temperature oxidation. 303 and 303Se are free-cutting stainless steels containing sulfur (Si) and selenium (Se), respectively, for applications requiring high cutting and high surface brightness. 316 stainless steel thick-walled tubes are also used to make parts that require enthusiasm because they have good hot workability under these conditions. 304L is a variant of the 304 stainless steel industrial welded pipe with a low carbon content for applications where welding is required. The lower carbon content minimizes the precipitation of carbides in the heat affected zone near the weld, which may result in intergranular corrosion (weld erosion) in certain environments. 304N is a nitrogen-containing stainless steel with nitrogen (N) added to increase the strength of the steel. 305 and 384 stainless steels contain high nickel and have a low work hardening rate, making them suitable for a variety of applications where high cold formability is required. 308 stainless steel is used to make the electrode. The nickel and chromium contents of 309, 310, 314 and 316 stainless steel welded pipes are relatively high in order to improve the oxidation resistance and creep strength of steel at high temperatures. The 30S5 and 310S are variants of the 309 and 310 stainless steels, except for the lower carbon content, in order to minimize the carbides precipitated near the weld. 316 stainless steel thick-walled tubes have exceptionally high resistance to carburization and thermal shock resistance. Source: China Stainless Steel Welded Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1. Introduction to duplex stainless steel Duplex stainless steel refers to a stainless steel in which the solid solution structure is composed of a ferrite and austenite duplex, and one of the comparative examples is about 45% to 55%. Due to the characteristics of the two-phase structure, the duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel. Compared with the ferritic stainless steel, it has high toughness, low brittle transition temperature, resistance to intergranular corrosion and good welding performance. The advantages of high thermal conductivity and small expansion coefficient of ferritic steel are retained. Compared with austenitic stainless steel, its yield strength is twice that of austenitic stainless steel. The resistance to chloride stress corrosion cracking is significantly higher than that of 300 series austenitic stainless steel. The resistance to pitting and crevice corrosion is similar to that of 316. stainless steel. Duplex stainless steel is widely used in oil and gas, petrochemical, fertilizer, bridge, construction and chemical tankers due to its excellent mechanical properties and corrosion resistance. 2. Progress in foreign research of duplex stainless steel The development of duplex stainless steel began in the 1930s. In 1936, the steel grade named Uranus50 obtained the first patent for duplex stainless steel in France. So far, duplex stainless steel has been developed for three generations. The first generation of duplex stainless steel is represented by Swedish 3RE60 and American AISI329. 3RE60 is a duplex stainless steel specially developed to improve the resistance to chloride stress corrosion cracking. AISI 329 duplex stainless steel is widely used in heat exchanger tubes for nitric acid plants. The first generation of duplex stainless steel has good performance characteristics, but it has limitations in the welding state. The heat affected zone of the weld has low toughness due to excessive ferrite and corrosion resistance is significantly lower than that of the base metal. These limitations have limited the use of first-generation duplex stainless steels to specific applications in non-welded conditions. In 1968, the stainless steel refining process, the invention of argon-oxygen decarburization, made it possible to produce a series of new stainless steel grades. One of the many advances brought by AOD is the addition of alloying elemental nitrogen. The addition of nitrogen to the duplex stainless steel allows the toughness and corrosion resistance of the heat affected zone to be close to that of the base metal in the welded state, and the nitrogen also reduces the rate of formation of the harmful intermetallic phase. Nitrogen-containing duplex stainless steel is known as second-generation duplex stainless steel. 2205 is a representative steel of the second generation of dual-phase steel and is widely used in offshore oil platforms, chemical, paper and other fields. The super duplex stainless steel developed in the late 1980s belongs to the third-generation duplex stainless steel, and the representative grades are SAF2507, UR52N, Zeron100, etc. These steels are characterized by low carbon content, high molybdenum and high nitrogen. This type of steel has excellent pitting resistance. Pitting equivalent) is greater than 40. From the current research and production level, Europe and the United States are at the leading level in the research and development and production of duplex stainless steel and the recognition of users. The representative companies include Sweden’s Outokumpu, Sandvik, and the US KA, KL. In Asia, Japan and South Korea are major producers of duplex stainless steel. The level of steel production is somewhat different from that of Europe and the United States. Take 2205 production as an example. The main brands produced in Japan and South Korea are S31803, while European and American production. The main grade is S32205. 3. Domestic research progress of duplex stainless steel The research on domestic duplex stainless steel began in the mid-1970s. The Beijing Iron and Steel Research Institute first started research work in this area. The 00Cr18Ni5Mo3Si2 developed by the company has been included in the national standard. Baosteel Special Steel Co., Ltd. has produced 2507 super duplex stainless steel pipes. Baosteel Pugang has produced 2205 plates. However, its production volume is small, and the finished product rate is low, mainly for special purposes. Taigang and Baosteel are currently available in China for commercial products. Taigang started to develop duplex stainless steel 2205 from the late 1990s, and introduced its products to the market in 2005. The 2205 produced by TISCO reached the standard level of S31803. The TISCO patent discloses a low nickel duplex stainless steel which has the advantages of low cost and high strength. Baosteel No. 1 Steel Co., Ltd. also started to develop Cr22 duplex stainless steel in 2006. Now it can produce 4~8mm coil plate and 14-30mm medium plate 2205. Baosteel’s patent discloses a high-nitrogen low-nickel duplex stainless steel with excellent room temperature impact resistance and corrosion resistance, which can be widely used in coastal construction, petrochemical and other fields. It is worth noting that some small and medium-sized stainless steel companies have also begun research on duplex stainless steel. 4. Future development direction of duplex stainless steel In recent years, with the rising and volatile fluctuations in Ni prices, duplex stainless steel has shown a trend of two developments. First, give full play to the advantages of resource saving of duplex stainless steel, and develop economical duplex stainless steel with 2101. Its development direction is to replace the traditional 300 series austenitic stainless steel. Its design idea is to replace Ni, Mo, etc. with Mn and N elements. Precious metal. Second. It is to fully utilize the characteristics of high-strength and good corrosion resistance of duplex stainless steel, and develop super duplex stainless steel represented by 2507 and 2906 to partially replace super austenitic stainless steel 904L, 254Mo and so on. It can be seen from the development of duplex stainless steel at home and abroad that duplex stainless steel is a resource-saving high-performance stainless steel product, and its production and application are in line with the future development of stainless steel. At the same time, duplex stainless steel is a high-tech, high value-added product. Its development and production not only reflects the technical level of stainless steel production enterprises, but also creates more economic benefits for enterprises. It is expected that the proportion of duplex stainless steel will be further expanded in the future, and the development of duplex stainless steel has a bright future. Source: China Duplex Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

First. China’s stainless steel seamless pipe production and consumption trends With the development of China’s economy and the acceleration of industrialization, oil, petrochemical, boiler, nuclear power, military, shipbuilding, fertilizer and other enterprises that have long relied on imported stainless steel pipes have turned their attention to stainless steel pipe products produced by Chinese enterprises. Development and construction meet the needs of the enterprise and the industry for stainless steel pipes. The general user has greatly improved the understanding of the stainless steel pipe, and began to select the material reasonably in the process of purchasing, paying attention to the material and physical properties of the steel pipe. There is a new trend in the demand for stainless steel seamless pipes: stainless steel pipes are widely used for condensers for generator sets; pipes for seawater purification devices are being replaced by dual-phase steel and super-ferritic stainless steel; oil well pipes are made of long stainless steel pipes ( Reduce joints; oil and gas open pipes, from 9Cr to 13Cr, duplex steel, super austenite, G3, G8, etc.; boiler tubes to meet supercritical, ultra-supercritical requirements, materials developed to 347H , super304, supet310s; the development of nuclear power industry drives a new opportunity for the development of high-end stainless steel pipe. Second, the current production and quality of stainless steel pipes in China China’s current stainless steel seamless pipe enterprises use advanced three-step smelting technology, basically no need to return the charge, ingot, forging (rolling), extrusion, perforation, cold rolling, perfect controllable heat treatment means, no chloride ions exist Acid pickling, reliable chemical, mechanical, physical, flaw detection and other inspection methods, clean production and assembly production environment, can produce nuclear industry, electronics industry, aerospace, ships and other stainless steel tubes used in enterprises. There are not many companies close to the above process level. Through efforts and cooperation, the production of high-pressure boiler tubes, oil (gas) well pipes, high-end chemical pipes and ship vessels for power stations account for about 15%-20% of the national output. The enterprise with basically reliable quality, the production process is basically smelted by electric furnace, the recycled material accounts for about 60%, ingot or continuous casting, hot rolled tube blank, perforation, general roller hearth furnace heat treatment, mixed acid pickling, tap water cleaning, routine inspection It can produce stainless steel seamless pipes for general chemical, printing and dyeing machinery manufacturing, vehicles and other industries. The output of these enterprises accounts for about 50% of China’s total output. Third. Overview of demand for medium and high-end stainless steel seamless pipes in major industries in China 1. Oil and gas industry The main oil and gas pipelines are PetroChina, Sinopec and CNOOC. The main applications are oil wells (pipes) and gas gathering stations. The petroleum industry must produce high-grade steel, corrosion-resistant and oil-well pipes with special requirements. Most of the current dependence on imports. With the development of natural gas and petroleum in China, high-volume gas fields and oil fields have been discovered in western areas such as eastern Sichuan and Xinjiang. The exploitation of these oil and gas fields has encountered the problem of coexistence of CO2, H2 S and CL ions. The highest content of CO2 exceeds 10 %, H2 S exceeds 60,000 ppm, and CL ions exceed 100,000 ppm. Therefore, high-alloy steel and stainless steel must be used to ensure the safety of oil and gas wells (one oil and gas well is tens of millions, and more than 100 million yuan). At present, the oil pipe and casing suitable for water injection environment are made of 13Cr and compounded materials. The oil pipes and casings suitable for CO2 moisture working environment are made of austenitic stainless steel; suitable for H2S-based, H2 S and CO2 coexistence environment. , using dual-phase steel and super austenite; suitable for CO2-based, H2S, CO2 coexistence environment, using dual-phase steel, super-alloy, high-alloy and QTHI nickel-based alloy. Among these materials, mainly include: 13Cr martensitic stainless steel and modified, 22Cr, 25Cr duplex stainless steel, Cr25Ni36, Cr25Ni38, Cr28Ni43 and other super-stainless steel, Monel K alloy and G3, G8 and other materials. In 2010, the oil was opened with stainless steel pipe, high-Cr steel pipe and high-nickel alloy pipe of about 25,000 tons. Main specifications: 2〞, 2.5〞, 3.5〞, 4.5〞, 5.5〞, 7〞, 8〞, 9〞 maximum caliber It is ∮508mm*30mm. The ground uses stainless steel pipes of about 6,000 tons, and the underground stainless steel seamless pipes are about 30,000 tons. Oil and gas are currently one of the world’s most important strategic materials. By 2020, China’s oil well exploitation will gradually develop in the west, desert, alpine and marine areas. The current global offshore oil and gas production accounts for 50%, and 44% of future oil and gas is in the deep sea area. China’s oceans have about 36 billion tons of oil resources. At present, China is limited to offshore within 200 meters, and it will be a period of rapid development by 2020. The “combustible ice” of oil and gas field reserves in the South China Sea equivalent to 20 billion tons of oil is under development, which will give corrosion resistance and extrusion resistance. Duplex stainless steel seamless pipe provides a large demand space. 2, Fertilizer industry At present, there are 40 large-scale chemical fertilizer enterprises and more than 2,518 small and medium-sized chemical fertilizer enterprises in China. It mainly produces urea, nitrogen fertilizer, phosphate fertilizer, potassium fertilizer and chloramine, ammonium bicarbonate, phosphorus ammonia and sulfuric acid base fertilizer. The basic fertilizer has been processed into a compound fertilizer through secondary processing; at present, China has obtained more than 2,500 compound fertilizer production license enterprises with a production capacity of more than 12 million tons. The scale of large-scale fertilizer enterprises is 400,000 tons/year, and the medium-sized average is 200,000 tons/year. In 2008, the total output of chemical fertilizers (demolition) was about 55,927,900 tons. The basic fertilizer process is mainly to use stainless steel equipment to complete the production process. Among the four major equipments for fertilizer production, the furnace tube to the synthesis tower and high-pressure condenser are the most demanding. Generally, the materials need to be 316L, 317L, 321 347H, 1Cr25Ni20, 1Cr36Ni38 and super-alloy, high-alloy steels, etc., to meet the needs of high temperature and strong corrosion. The best service life of the furnace tube is 3-4 years, generally 1-2 years, and the specifications of the furnace tube are mainly ф159mm-406mm. At present, the gasification furnace and evaporator of the fertilizer industry use not less than 8,000 tons of high-quality stainless steel pipes every year, almost all rely on imports, and also use cast stainless steel pipes. The other pipes of the fertilizer industry are around 30,000 tons a year. The total amount of stainless steel pipes for fertilizer industry in China is about 35,000 tons per year. 3. Chemical industry By 2020, China’s oil consumption will be about 450-460 million tons. Natural gas consumption is 200 billion cubic meters, and the corresponding crude oil processing capacity and ethylene production capacity reach 28.5 million tons. Stainless steel pipes in the petrochemical industry are mainly used for heating pipes and heat exchange gas pipes, atmospheric and pressure post-cooler pipes, tray coils, water cooler heat exchange pipes, cooler pipes, flue pipes, and hydrogenation devices. Process pipeline. Part of the heat exchanger and dryer piping in the PTA unit, the acetic acid plant process line, and the synthesis reactor tube in the methanol mixture. The material flows out of the heat effect, the medium pressure flash tank top condenser tube, the ethylene catalyst in the catalyst regeneration cooler tube, etc., only the petrochemical industry, the annual need for stainless steel pipe not less than 100,000 tons, other industries are also used in 60,000-7 10,000 tons / year. 4. Boiler industry By 2020, China plans to add 294 million kW of generator capacity. According to the analysis of the current new projects, it is possible to develop to 360 million to 430 million kW. In the past few years, it was around 90 million kW per year. After 2010, the annual installed capacity was between 3200-4200 kW. Add 220 million to 280 million kW of thermal power generators. About 6000kW per year. The state focuses on the development of supercritical, ultra-supercritical high-efficiency thermal power generating units. The efficiency of the generator set depends mainly on the pressure and temperature parameters of the steam. The higher the parameters, the higher the efficiency. The supercritical unit is generally 700,000 kW and the steam pressure is 25.2 MPa. Temperature 566 ° C / 566 ° C, ultra-supercritical unit pressure 27.26 MPa, temperature 600 ° C / 600 ° C As supercritical and ultra-supercritical boilers are put into production, the requirements for furnace tubes are getting higher and higher. The average quota of steel pipes for power generation equipment is about 90T/10,000 kW, of which stainless steel is about 5-8T/10,000 kW. By 2010, an average of 32,000-42,000 tons of stainless steel seamless pipes are used every year. The overhaul period of the power station boiler is 8 years. Therefore, the consumption of stainless steel pipes for boilers should not only consider the needs of new units, but also meet the demand for stainless steel pipes in each overhaul cycle. 5. Nuclear industry By 2020, China’s nuclear power industry will develop at a high speed, and nuclear power projects such as Zhejiang Sanmen, Shandong Haiyang, Liaoning Hongyan River, Fujian Ningjia, and Guangdong Yangjiang are under construction. The installed capacity has increased from 9.8 million kW to 30 million kW. This requires the simultaneous development of the nuclear fuel industry and the nuclear power industry. The whole process equipment for nuclear fuel production uses stainless steel, high alloy steel and mixed materials such as lead and aluminum, of which stainless steel accounts for 80%. According to the current development speed of China’s nuclear industry, it is estimated that the annual demand will increase by about 5,000 tons. The nuclear power industry is a nuclear reactor used for power generation, which is pided into light water reactors and nano-cooling reactors. Except that the cladding material of the equipment is changed from lead to stainless steel containing Ti, the internal structure is all stainless steel tubes. The nuclear industry also has waste liquid and waste treatment. In order to prevent leakage and avoid pollution, the 0Cr25Ni20Nb DN300 steel pipe is combined with lead and antimony to form a cylinder, sink in deep water or bury in the desert area, after several decades or several A hundred years of energy decay will be safe for the natural world and for human society. A factory also uses hundreds of tons per year. Fourth, the development of stainless steel seamless pipe industry The integration and reorganization of high-end enterprises in stainless steel pipes is to exploit the advantages of various enterprises, reduce re-construction, reduce vicious competition, stabilize product quality, improve material cost performance, and facilitate the development trend of participating in international circulation. The professionalization of the company’s product direction is further improved, which can be roughly pided into the production of nuclear industrial tubes, boiler tubes, petrochemical tubes, oil (gas) open tubes, ship tubes and general fluid tubes. plant. In the next few years, the product advantages of extra-large steel pipe enterprises will become increasingly apparent. In the next few years, China will build a super-large-scale special steel pipe company. The products are mainly made of stainless steel, including alloy steel and high-alloy steel. The pipe diameter is 406mm-∮12000mm and the wall thickness is 40mm-270mm. The production capacity is between 500,000 and 700,000 tons/year, which makes China rely on imported large-diameter, large-wall-thick steel pipes to achieve self-sufficiency. The overall consumption market of stainless steel seamless pipes in China is still growing. At present, despite the impact of the financial crisis, the overall economic development level of the country is still good. It is predicted that by 2020, the total demand for stainless steel seamless pipes in China will reach 500,000. 550,000 tons / year, industrial stainless steel welded pipe 80,000-100,000 tons, water industry pipe 200,000 tons. By 2020, China’s high-end stainless steel seamless steel pipe will basically meet the needs of medium and high-end pipe use in China’s nuclear industry, boiler industry, oil and gas well industry, shipbuilding industry, electronics industry, fertilizer industry and other fields. At the same time, it is difficult to solve the problem of import demand. In the future, China’s stainless steel seamless steel pipe can have the world’s advanced technology and equipment level, China’s stainless steel seamless steel pipe will enter a new stage of exhibition. Source: China Stainless Steel Seamless Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The integrity of the flange connection is critical to the delivery of fluid piping systems. Whether it is a piping system that transports chemical media (such as hydrocarbons) or a water supply line, flange connection leakage can cause serious environmental and economic impacts, and may even pose a huge safety hazard. If the flange is not protected, it can be exposed to corrosive environments or contaminated industrial atmospheres. In addition, due to the complex geometry of the flange connection, crevice corrosion between the two flange faces and galvanic corrosion between different metals are highly likely to seriously damage the integrity of the pipeline system. This article describes several practical methods for solving flange corrosion. In order to meet the demanding production needs and reduce the sudden shutdown caused by leakage, effective monitoring and inspection is essential. Often the technician is more concerned with the leakage problem between the flange faces, while ignoring the protection of the fasteners and the exterior of the pipe, which can have extremely serious consequences in a harsh external environment. Insufficient external protection accelerates and expands the damage to the flanges and fasteners, causing the entire seal system to accelerate and deteriorate, potentially damaging the structural integrity of the system and causing seal failure. Visual inspection of the flanged sealing faces can only be carried out when the entire system is shut down. The inspection procedure should be as simple as possible and the external corrosion should first be eliminated. If it is not possible to stop the machine, it can only be detected by ultrasonic technology. In the case where external corrosion cannot be controlled, the process will be more complicated and accurate test results will not be obtained. Therefore, in order to monitor the entire system and provide effective and feasible quality control and overhaul procedures, external corrosion protection of flanges and fasteners is critical. Existing solution Ideal solution It should take into account excellent corrosion protection performance and simple construction procedures, and should be suitable for flanges of various sizes and shapes, and it is convenient to operate the bolts during maintenance. Common solutions currently on the market include: Maintenance paint solution Maintenance paint is a hard film that can be bonded directly to a substrate, typically an epoxy or polyurethane coating. Flanges have many edges, and it is difficult for conventional paint systems to effectively cover the edges due to edge thinning effects. Although the thicker coating will solve the problem of edge protection, it will also seal the fasteners and will not be disassembled for subsequent repairs. In addition, the coating will be destroyed when the bolt is operated and must be repainted after repair. Mechanical solution The gap between the flange and the flange surface is mainly sealed by the protective cover and the clamp, and is usually made of stainless steel or plastic with a rubber sealing strip. This type of protection is less flexible and requires the storage of covers or clamps that are perfectly matched to flanges of all sizes. Tape or semi-solid anti-corrosion tape solution Roll-wrapped tape (such as petrol tape, wax or elastic polymer wrap) is protected by wrapping on the surface of the substrate. Due to the good water resistance of semi-solid polymers, this protection provides reliable corrosion protection. However, if the flange is complex in shape, this material is not only time consuming but also difficult to construct. When the bolts need to be disassembled, the material is relatively soft and easy to cut, but it is difficult to reseal and restore the original protection after disassembly and assembly, and generally requires re-construction. Hot melt plastic solution The hot melt plastic is essentially a high temperature heated waxy fusible polymer that is sprayed onto the surface of the substrate by professional hot melt equipment. The advantage of this type of protection is that it can be remelted and reused, saving costs. However, this method also requires hot work, professional equipment and construction services. Although it can be reused, it is not easy to open and seal during maintenance. Polymer sealed bag solution The sealed bag encloses the flange completely and consists of a low permeability polymer, a corrosion inhibitor vapor and a desiccant. It is easy to install, but the ends of the bag are only sealed with tape, rather than a durable and effective mechanical bond. There is a large area of steam inside the bag, which is easy to collect a large amount of water, and the corrosion inhibitor will be consumed for a period of time. Although the above scheme can play a certain role in anti-corrosion protection, there are still some defects in construction, inspection and maintenance. It is necessary to explore and develop effective solutions to provide long-term and comprehensive protection for the flange. New peelable sealing membrane system In response to the problem of flange corrosion, the company has developed a new peelable sealing film system that is tough and flexible enough to use the chemical action of the polymer. It can be peeled back backwards without tearing, and has rubber elasticity. It is completely free of isocyanate and toxic metal catalysts. Designed to protect flanges, fasteners and associated piping, the system can be bonded to hand-treated substrates without the need for hot work, making construction safe and easy. The system uses a corrosion inhibitor as a primer to provide overall corrosion protection, while the coating itself has a strong bond that removes all moisture from the system. System corrosion resistance The corrosion resistance of the system is tested by salt spray and the corrosion resistance of the coating is evaluated by continuously placing the sample in a salt spray environment. The salt spray box converts a sodium chloride solution of 5% mass fraction into a high temperature salt spray of 35 °C. The test specimens were assembled flanged joints with bare steel on one side and the sealing membrane system on one side. The samples were exposed to a salt spray for 1000 h and no signs of corrosion were found under the sealing membrane system. In contrast, the bare steel portion on the other side of the flange is severely corroded. System adhesion performance In order to ensure that the port is permanently sealed and moisture is removed, the system requires excellent adhesion, especially in close adhesion to manually treated surfaces. Adhesion testing was performed on three different substrates that were manually surface treated according to ASTM D429 and ISO8510-1. The results show that the sealing film fails on the three kinds of substrates without adhesion failure, that is, the adhesion on the substrate is greater than the gelation cohesion of the polymer material, which proves that the sealing film has excellent adhesion. performance. System stripping performance and flexibility Another feature of the system is that the constructor can easily operate the fasteners. When it is time to repair! Simply insert the blade into the sealing film between the flange faces and cut it along the circumference of the flange. Then pide the sealing film into two halves, or you can pull it back together with the plastic cap to expose the flange and bolt. After the repair is completed, the sealing film can be folded back to its original position. In order to meet the peelable characteristics, the sealing system must be both strong and flexible. The tests for tensile strength, elongation strength and tear strength were carried out in strict accordance with ASTM D412 and ASTM D624. The use of reinforcing strips at both ends of the coating finish on the pipe and at the circumference of the flange face can increase the strength of the polymer material in critical stress areas during the peeling and sealing process during the test, giving the system superior elasticity and Intensity. When resealing is required, the circumference of the flange must be cleaned to remove all dust, grease and surface contaminants. Then use a sealing film to brush the circumference of the cut protection system for quick and easy repair protection. For the flange anti-corrosion problem, although there are different solutions on the market, most of the solutions can not have excellent anti-corrosion protection, easy installation, suitable for various flange sizes and shapes, and easy maintenance. After careful development, the peelable sealing system provides complete protection for the flange and avoids the potential risk of flange leakage. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Duplex stainless steel has two kinds of metal phase structure, so the duplex stainless steel can combine the properties of ferritic stainless steel and austenitic stainless steel by properly controlling the chemical composition and heat treatment process, that is, the good toughness and welding of austenitic stainless steel. Performance combined with higher strength and chloride stress corrosion resistance of ferritic stainless steel. It is these superior properties that make duplex stainless steel develop rapidly as a weldable structural material. Typical grades in duplex stainless steel are 2205 duplex stainless steel and 2507 duplex stainless steel. Development and application of duplex stainless steel 1.1.1 Overview of the development of duplex stainless steel at home and abroad The development of duplex stainless steel began in the 1930s, France won the first patent in 1935, and duplex stainless steel has been developed for three generations. The first generation of duplex stainless steel is represented by 329 steel developed in the United States in the 1940s. It contains high chromium and molybdenum and has good local corrosion resistance, but has a high carbon content (≤0.1% c). Therefore, the loss of phase balance during welding and the precipitation of carbides along the grain boundary result in a decrease in corrosion resistance and toughness, which must be subjected to heat treatment after welding, and is generally used only for casting and forging, and is limited in application. In the 1950s, the 08X2lH5T and 08x2lH6M2T steels with stabilizing elemental titanium were developed. At the same time, Germany developed 1.458Z steel, France developed Urnnus50 steel, Britain successfully developed Ferriumlium255 steel, and Japan reduced it based on US 329 steel. The carbon content was presented at 329J. Steel grades, these duplex stainless steels can be used as weldable structural parts. Later, in the mid-1960s, Sweden developed the famous 3RE60 steel, which is the representative steel of the first generation of duplex stainless steel. It is characterized by ultra-low carbon, 18% chromium content, good welding and forming properties, and can be widely used to replace AIsl304L. 316L is used as a material resistant to chloride ion stress corrosion. Since the 1970s, with the emergence and popularization of secondary refining technologies such as AOD and VOD, ultra-low carbon steels can be easily smelted, and nitrogen is found as an austenite forming element to improve corrosion resistance of duplex stainless steel. Important role, improved the shortcomings of the first generation of duplex stainless steel, thus creating a second generation of new nitrogen-containing duplex stainless steel and developed a new application field of duplex stainless steel. The second-generation duplex stainless steels, whether 18Cr or 22Cr or 25cr, are mostly ultra-low carbon and have been included in the ASTM A789 and A790 standards in the United States. In addition, France has uRANUS series, Britain has ZERON cast steel series, Germany also has a series of grades of steel grades. The super duplex stainless steel (SuperDss) developed in the late 1980s belongs to the third-generation duplex stainless steel, and the grades are SAF2507, UR52N+, zeronl00, etc. These steels are characterized by extremely low carbon content (C 0.01% to 0.02). %), containing high molybdenum and high nitrogen (Mo 1% ~ 4%, N 0.1% ~ 0.3%), the ferrite content of steel is 40% ~ 50%, such steel has excellent pitting corrosion resistance The pitting resistance equivalent value (PRE=Cr%+3.3×Mo%+16×N%) is greater than 40⋯. South Korea’s 1996 duplex stainless steel (patent application number: 96190623) has superior thermoplasticity, high temperature oxidation resistance, corrosion resistance and impact toughness. China has developed duplex stainless steel since the mid-1970s. The Beijing Iron and Steel Research Institute first carried out research work in this area. The 00Crl 8Ni5M03Si2 duplex stainless steel developed by the company has been included in the national standard GBl220, GB3280, GB4237. In addition, on the basis of analyzing the development of foreign duplex stainless steel, the No. 5 Research Institute successfully developed a new rare earth duplex stainless steel SG52 with an anti-pitting equivalent of PRE≥40. The steel is modified with rare earth and has nickel, which has good mechanical properties, process performance and corrosion resistance. 1.1.2 Classification and composition of duplex stainless steel Duplex stainless steel can be mainly pided into two categories, one is Cr-Ni duplex stainless steel, the composition (mass fraction) is generally: Cr 17% ~ 25%, Mn 3% ~ 10%, Mo 0 ~ 6%, Si ≤ 0.5% to 6%, Ni 3% to 7%; Cu 0 to 3%, N 0 to 0.4%, containing a small amount of carbon, the main feature is that it contains higher chromium and lower nickel; Is Cr-Mn-N duplex stainless steel, into The sub-ranges are: Cr 18% to 25%, Mn 8% to 16%, N 0.2% to 0.4%, Mo 0 to 3%, Si ≤ 2%, C ≤ 0.20%, and its composition characteristics It is low in nickel and contains high nitrogen. 1.1.3 Performance characteristics of duplex stainless steel Since the duplex stainless steel has a two-phase structure, the duplex stainless steel can combine the properties of ferritic stainless steel and austenitic stainless steel by properly controlling the chemical composition and the heat treatment process, that is, the good toughness and weldability of the austenitic stainless steel. Combined with higher strength and chloride stress corrosion resistance of ferritic stainless steel. It is these superior properties that make duplex stainless steel develop very rapidly as a weldable structural material. In a nutshell, duplex stainless steel has the following main features: (1) Duplex stainless steel containing 18% to 22% Cr has good resistance to neutral chloride stress corrosion under low stress. 18-8 type austenitic stainless steel applied to a neutral chloride solution at 70 ° C or higher is prone to stress corrosion cracking on heat-dissipating parts such as heat exchangers and evaporators used in industrial media such as chlorides and sulfides. (2) Duplex stainless steel containing molybdenum has good pitting corrosion resistance, and the pitting corrosion resistance of duplex stainless steel containing 18% Cr is equivalent to that of AISl316L steel. The corrosion resistance and crevice corrosion resistance of duplex stainless steel containing 25% Cr, especially nitrogen-containing duplex stainless steel, exceeds that of AISl316L steel. (3) Duplex stainless steel has high strength and toughness, good overall performance, and yield strength twice that of austenitic stainless steel 18-8. (4) Good weldability, low thermal cracking tendency, no preheating before welding, no heat treatment after welding, and welding with dissimilar steel such as 18-8 austenitic stainless steel or carbon steel. *Includes SAF2304, 2205, SAF2507 (5) The hot working temperature range is wider than that of the 18-8 type austenitic stainless steel, and the deformation resistance is small. The duplex stainless steel containing low chromium (18% Cr) can be directly rolled to produce profiles and steel sheets without forging. (6) The cold working performance is larger than that of the 18-8 type austenitic stainless steel. In the initial stage of deformation of the tube and the plate, a large stress is required to deform. (7) Various brittleness tendencies of high-chromium ferritic stainless steel, and should not be used under working conditions higher than 350 °C. The lower the chromium content in duplex stainless steel, the less the hazard of phase brittleness. (8) Compared with austenitic stainless steel, it has high thermal conductivity and small coefficient of linear expansion, and is suitable for use as a lining for equipment and for producing composite panels. 1.1.4 Main application of duplex stainless steel pipe After decades of research and development, duplex stainless steel has won a place in the chemical, petroleum, paper, energy, shipbuilding, military and other industrial fields, and its application range is also expanding. Source: China Duplex Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Corrosion is one of the important elements that cause valve damage. Therefore, valve protection is an important issue to consider in valve protection. PetroChina and Sinopec talk about anti-corrosion: What is the corrosion of the valve? How to carry out valve anti-corrosion? What is the basis for the selection of corrosion-resistant valves? 1. Valve corrosion form The corrosion of metals is mainly caused by chemical corrosion and electrochemical corrosion. The corrosion of non-metallic materials is generally caused by direct chemical and physical damage. Chemical corrosion The surrounding medium directly reacts with the metal to cause damage under the condition that no current is generated, such as corrosion of the metal by the high-temperature drying gas and the non-electrolytic solution. 2. Electrochemical corrosion The metal is in contact with the electrolyte, causing the flow of electrons, which destroys itself in electrochemical action, which is the main form of corrosion. Common acid-base salt solution corrosion, atmospheric corrosion, soil corrosion, seawater corrosion, microbial corrosion, stainless steel pitting corrosion and crevice corrosion are all electrochemical corrosion. Electrochemical corrosion occurs not only between two substances that can act as a chemical, but also because of the difference in concentration of the solution, the difference in the concentration of surrounding oxygen, the slight difference in the structure of the substance, etc., the difference in potential is generated, and the power of corrosion is obtained. The metal with low potential and in the positive position is lost. Valve corrosion rate Corrosion speed can be pided into six: Full corrosion resistance corrosion rate less than 0.001 mm / year Extreme corrosion resistance corrosion rate 0.001 to 0.01 mm / year Corrosion resistance corrosion rate 0.01 to 0.1 mm / year Corrosion resistance corrosion rate 0.1 to 1.0 mm / year Poor corrosion resistance Corrosion rate 1.0 to 10 mm / year Non-corrosion corrosion rate greater than 10 mm / year Nine major anti-corrosion measures 1. Select corrosion resistant materials according to corrosive media In the actual production, the corrosion of the medium is very complicated. Even in the case of the valve material used in a medium, the concentration, temperature and pressure of the medium are different, and the medium is not corroded to the material. For every 10 °C increase in the temperature of the medium, the corrosion rate increases by about 1 to 3 times. The concentration of the medium has a great influence on the corrosion of the valve material. For example, the lead is in the sulfuric acid with a small concentration, and the corrosion is small. When the concentration exceeds 96%, the corrosion rises sharply. On the contrary, carbon steel is the most severe when the concentration of sulfuric acid is about 50%. When the concentration is increased to more than 6%, the corrosion drops sharply. For example, aluminum is highly corrosive in concentrated nitric acid at a concentration of 80% or more, but it is severely corroded in medium and low concentrations of nitric acid. Although stainless steel has strong corrosion resistance to dilute nitric acid, corrosion is more serious in more than 95% concentrated nitric acid. It can be seen from the above examples that the correct selection of valve materials should be based on the specific conditions, analyze various corrosion factors, and select materials according to the relevant anti-corrosion manual. 2. Using non-metallic materials Non-metallic corrosion resistance is excellent, as long as the valve temperature and pressure meet the requirements of non-metallic materials, it can not only solve the corrosion problem, but also save precious metals. The valve body, valve cover, lining, sealing surface and other common non-metallic materials are used. As for the gasket, the filler is mainly made of non-metallic materials. The valve is lined with plastic such as polytetrafluoroethylene or chlorinated polyether, and rubber such as natural rubber, neoprene or nitrile rubber, and the body of the valve body and bonnet is made of general cast iron and carbon steel. That is to ensure the strength of the valve, and to ensure that the valve is not corroded. The pinch valve is also designed based on the excellent corrosion resistance and excellent properties of the rubber. Nowadays, plastics such as nylon and polytetrafluoroethylene are used more and more, and various sealing surfaces and sealing rings are used for natural rubber and synthetic rubber for various types of valves. These non-metallic materials used as sealing surfaces not only have good corrosion resistance, but also good sealing performance, and are particularly suitable for use in granular media. Of course, their strength and heat resistance are low, and the range of applications is limited. The emergence of flexible graphite has enabled non-metals to enter the high-temperature field, solving the long-term problem of filler and gasket leakage, and is a good high-temperature lubricant. 3. Metal surface treatment Valve connection The valve connection screw is usually galvanized, chrome-plated, and oxidized (blue) to improve the resistance to atmospheric and medium corrosion. In addition to the above methods, other fasteners are also subjected to surface treatment such as phosphating depending on the situation. Sealing surface and closing piece with small diameter Surface processes such as nitriding and boronizing are often used to improve its corrosion resistance and wear resistance. The valve disc made of 38CrMoAlA has a nitrided layer ≥0.4mm. Stem corrosion protection Surface treatment processes such as nitriding, boronizing, chrome plating, and nickel plating are widely used to improve corrosion resistance, corrosion resistance and abrasion resistance. Different surface treatments should be suitable for different valve stem materials and working environments. The stems that are in contact with the atmosphere, water vapor medium and asbestos packing can be hard chrome-plated and gas nitriding (stainless steel is not suitable for ion nitriding); The valve in the hydrogen sulfide atmosphere has better protection performance by electroplating high-phosphorus nickel plating; 38CrMoAlA can also resist corrosion by ion and gas nitriding, but it is not suitable to use hard chrome plating; 2Cr13 can be resistant to ammonia corrosion after quenching and tempering, carbon steel using gas nitriding can also resist ammonia corrosion, and all phosphorous nickel coatings are not resistant to ammonia corrosion; The gas nitriding 38CrMoAlA material has excellent corrosion resistance and comprehensive performance, and it is used to make a valve stem. Small diameter valve body and hand wheel It is also often chrome-plated to improve its corrosion resistance and to decorate the valve. 4. Thermal spraying Thermal spraying is a type of process block for preparing coatings and has become one of the new technologies for surface protection of materials. It uses a high energy density heat source (gas combustion flame, arc, plasma arc, electric heat, gas explosion, etc.) to heat and melt the metal or non-metal material, and then sprays it onto the pretreated basic surface in atomized form to form a sprayed layer. , or a method of surface strengthening which simultaneously heats the basic surface to re-melt the coating on the surface of the substrate to form a spray-welded layer. Most metals and their alloys, metal oxide ceramics, cermet composites, and hard metal compounds can be coated on a metal or non-metal substrate using one or more thermal spray methods. Thermal spraying can improve the surface corrosion resistance, wear resistance, high temperature resistance and other properties, and prolong the service life. Thermal spray special function coating with special properties such as heat insulation, insulation (or isoelectric), grindable seal, self-lubricating, heat radiation, electromagnetic shielding, etc.; parts can be repaired by thermal spraying. 5. Spray paint Coating is the most widely used anti-corrosion method, and it is an indispensable anti-corrosion material and identification mark on valve products. Coatings are also non-metallic materials. They are usually made of synthetic resin, rubber slurry, vegetable oil, solvent, etc., covering the metal surface, insulating the medium and the atmosphere to achieve anti-corrosion purposes. Coatings are mainly used in environments where water, salt water, sea water, and the atmosphere are not corrosive. The inner cavity of the valve is usually painted with anti-corrosive paint to prevent the water, air and other media from corroding the valve. The paint is mixed with different colors to represent the materials used by Faine. Valve spray paint, usually in half a year to once a year. 6. Add corrosion inhibitor What is the mechanism of corrosion inhibitor control? It is that it promotes the polarization of the battery. Corrosion inhibitors are mainly used in media and packing. Adding corrosion inhibitor to the medium can slow down the corrosion of equipment and valves. For example, chrome-nickel stainless steel is ignited in a large range of solubility in oxygen-free sulfuric acid. Corrosion is serious, but a small amount of copper sulfate or nitric acid is added. When the oxidant is used, the stainless steel can be transformed into a passive state, and a protective film is formed on the surface to prevent the etching of the medium. In the hydrochloric acid, if a small amount of the oxidizing agent is added, the corrosion of the titanium can be reduced. The valve pressure test commonly uses water as the medium for pressure test, which is easy to cause corrosion of the valve. Adding a small amount of sodium nitrite in water can prevent the water from corroding the valve. The asbestos filler contains chloride, which is very corrosive to the valve stem. If the steamed water washing method is used, the chloride content can be reduced. However, this method is difficult to implement and cannot be generalized. The ester is suitable for special needs. In order to protect the valve stem and prevent corrosion of the asbestos filler, in the asbestos filler, the valve stem is coated with a corrosion inhibitor and a sacrificial metal. The corrosion inhibitor consists of sodium nitrite and sodium chromate to form a passivation film on the surface of the valve stem to improve the corrosion resistance of the valve stem; the solvent can dissolve the corrosion inhibitor slowly and can provide lubrication; Zinc powder is added to asbestos as a sacrificial metal. In fact, zinc is also a corrosion inhibitor. It can be first combined with chloride in asbestos, so that the chance of contact between chloride and stem metal is greatly reduced, thus achieving anti-corrosion purposes. If a corrosion inhibitor such as red dan or calcium lead is added to the coating, the surface of the valve can prevent corrosion of the atmosphere. 7. Electrochemical protection Electrochemical protection has both anodic protection and cathodic protection. If zinc is used to protect iron, zinc is corroded and zinc is called sacrificial metal. In production practice, anode protection is used less and cathodic protection is used more. Large-scale valves and important valves use this cathodic protection method, which is an economical, simple and effective method. Zinc is added to the asbestos filler and the protective stem is also a cathodic protection method. 8. Control the corrosive environment The so-called environment, there are two broad and narrow senses, the generalized environment refers to the environment around the valve installation and its internal circulation medium; the narrow environment refers to the conditions around the valve installation. Most environments are uncontrollable and production processes are not subject to change. Only when there is no damage to the product or process, the method of controlling the environment can be adopted, such as boiler water deoxidation, and the pH value of the alkali in the refining process. From this point of view, the above-mentioned addition of corrosion inhibitors, electrochemical protection, and the like are also controlled corrosion environments. The atmosphere is filled with dust, water vapor, and smoke, especially in production environments, such as smoke and halogen, toxic gases and fine powder emitted from equipment, which can cause different degrees of corrosion on the valve. The operator should periodically clean and purge the valve and regularly refuel according to the regulations in the operating procedures. This is an effective measure to control environmental corrosion. The valve stem is installed with a protective cover, the ground valve is provided with a well, and the surface of the valve is painted with paint, etc., which are methods for preventing corrosion of the valve by corrosive substances. Increased ambient temperatures and air pollution, especially in closed environments, can accelerate corrosion. Floors should be used as much as possible or ventilation and cooling measures should be adopted to reduce environmental corrosion. 9. Improve processing technology and valve structure The anti-corrosion protection of the valve is a problem that has been considered from the design. A valve product with reasonable structural design and correct process method will undoubtedly have a good effect on slowing the corrosion of the valve. Therefore, the design and manufacturing department should improve the components that are unreasonable in structural design, incorrect in process methods, and prone to corrosion, and should be improved to suit the requirements of various working conditions. Corrosion type for different valve components 1. Methods for preventing intergranular corrosion of austenitic stainless steel valve parts are as follows: The solution treatment is carried out by solid solution quenching, that is, heating to about 1100 ° C for water quenching, and austenitic stainless steel containing titanium and niobium and having a carbon content of 0.03% or less is used to reduce the generation of chromium carbide. 2. Stress corrosion occurs under the action of both corrosion and tensile stress. Methods to prevent stress corrosion: Eliminate or reduce the stress generated by welding and cold working by heat treatment, improve the irrational valve structure, avoid stress concentration, and adopt electrochemical protection and spray anti-corrosion coating. Add corrosion inhibitor, apply compressive stress and other measures. 3. Wear corrosion is a form of corrosion caused by the alternating action of fluid on metal wear and corrosion. It is a common type of corrosion of valves, which occurs in the sealing surface. Prevention method: use corrosion-resistant and wear-resistant materials, improve structural design, and adopt cathodic protection. 4. Vibration corrosion is the simultaneous contact of two parts in contact with each other, and the contact surface is damaged by vibration and sliding. Frictional corrosion occurs at the bolted joint, between the stem and the closure, between the ball bearing and the shaft. Prevention method: It can be applied by lubricating grease, reducing friction, surface phosphating, using hard alloy, and improving the surface hardness by spraying or cold working. 5. After welding, it is necessary to adopt corresponding protective measures such as annealing treatment. Improve the surface roughness of the valve stem and the surface roughness of other valve parts. The higher the surface roughness level, the stronger the corrosion resistance. Prevention methods: Improve the processing and structure of fillers and gaskets, use flexible graphite and plastic fillers, as well as flexible graphite adhesive gaskets and PTFE gaskets to improve sealing performance and reduce the stem and Corrosion of the flange sealing surface. Valve parts anti-corrosion precautions 1. Stem corrosion and protection Main causes of stem corrosion: Corrosion damage of the valve body is mainly caused by corrosive media, and the problem of valve stem corrosion is mainly filler. Not only does the corrosive medium corrode the stem, but steam and water can also cause spots on the stem to contact the packing. Especially for valves stored in warehouses, stem corrosion can occur. This is the electrochemical corrosion of the filler to the valve stem. The most widely used filler is the asbestos-based packing. The asbestos material contains a certain amount of chloride ions, in addition to potassium, sodium and magnesium ions, which are all corrosive factors. Valve stem anti-corrosion precautions: Do not add filler during valve storage. Without filling, it loses the electrochemical corrosion of the valve stem and can be stored for a long time without being corroded. The stem is surface treated. Such as chrome plating, nickel plating, nitriding, boronizing, zinc and so on. Reduce asbestos impurities. Washing with distilled water can reduce the chlorine content in asbestos and reduce its corrosivity. Add a corrosion inhibitor to the asbestos packing. This corrosion inhibitor suppresses the corrosiveness of chloride ions. Such as sodium nitrite. Add sacrificial metal to asbestos. This is a metal that is lower than the stem potential as a victim. This corrosion of chloride ions first occurs on the sacrificial metal, thereby protecting the valve stem. It can be used as a sacrificial metal such as zinc powder. Protected with Teflon. Polytetrafluoroethylene has excellent chemical stability and dielectric properties, and current cannot pass. If the asbestos packing is impregnated with polytetrafluoroethylene, the corrosion will be reduced. The asbestos packing can also be wrapped with a Teflon tape and then loaded into a stuffing box. Improve processing smoothness and also reduce electrochemical corrosion. 2. Closed parts corrosion and protection The main reason for the corrosion of the closure: The closure is often flushed with fluid, allowing corrosion to accelerate. Some discs, although using better materials, are still more corrosive than the valve body. The upper and lower closing members are usually threadedly connected with the valve stem and the valve seat, and the joint is deficient in oxygen than the general portion, which easily constitutes an oxygen concentration battery, causing corrosion damage. Some sealing parts are pressed into the sealing surface. Due to the lack of tightness and slight gap, oxygen concentration battery corrosion may occur. Close parts anti-corrosion notes: Use corrosion resistant materials as much as possible. The closing piece has a small weight, but plays a key role in the valve, as long as it is resistant to corrosion, even with a little expensive material. Improve the closure structure so that it is less subject to fluid erosion. Improve the connection structure to avoid the generation of oxygen concentration batteries. In valves below 200 ° C, the joint between the closing part and the sealing surface, using a Teflon raw material tape as a filler, can reduce the corrosion of these parts. While considering corrosion resistance, attention should also be paid to the erosion resistance of the closure material. Use a material that is resistant to erosion as a closure. Corrosion resistant valve selection points In the case of corrosive media conditions, anti-corrosion is the most critical place for chemical equipment. If the metal material of the chemical valve cannot be correctly selected, it is slightly inadvertent, and the equipment is damaged, which may cause accidents or even disaster. How to choose the corrosion-resistant valve for some common chemical media? 1. Sulfuric acid medium As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Different concentrations and temperatures of sulfuric acid have a great difference in corrosion of materials. For concentrated sulfuric acid with a concentration above 80% and temperature less than 80 °C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid. Not suitable for use as a valve material. Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited in their use for sulfuric acid media. Therefore, valves for transporting sulfuric acid are usually made of high-silicon cast iron (difficult to cast and process) and high-alloy stainless steel (20 alloy). Fluoroplastics have better resistance to sulfuric acid, and a fluorine-lined pump valve (F46) is a more economical option. If the pressure is too high and the temperature rises, the point of use of the plastic valve is impacted, and only a ceramic ball valve that is more expensive than it is selected. 2. Hydrochloric acid medium Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum-containing high-silicon iron can only be used for hydrochloric acid at 50 ° C and 30%. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choice for transporting hydrochloric acid. However, if the temperature of the medium exceeds 150 ° C, or the pressure is greater than 16 kg, any plastic (including polypropylene, fluoroplastic or even Teflon) will not be competent, and there is no ideal valve on the market. . However, you can try the emerging ceramic ball valve. The advantages of this valve are self-lubricating, low torque, no aging, and much longer life than normal valves. Its disadvantage is that the price is much higher than plastic valves. 3. Nitric acid medium Generally, most metals are quickly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid-resistant material. It has good corrosion resistance to all concentrations of nitric acid at normal temperature. It is worth mentioning that it contains molybdenum-containing stainless steel (such as 316 and 316L). The corrosion resistance to nitric acid is not only not superior to ordinary stainless steel (such as 304, 321), and sometimes even worse. For high temperature nitric acid, titanium and titanium alloy materials are usually used. 4. Acetic acid medium It is one of the most corrosive substances in organic acids. Ordinary steel is severely corroded in acetic acid of all concentrations and temperatures. Stainless steel is an excellent acetic acid resistant material. Molybdenum-containing 316 stainless steel can also be used for high temperature and dilute acetic acid vapor. . High-alloy stainless steel or fluoroplastic valves are available for demanding requirements such as high temperature, high concentration acetic acid or other corrosive media. 5. Alkali (sodium hydroxide) Steel is widely used in sodium hydroxide solutions below 80 ° C and 30% concentration. Many petrochemical plants still use ordinary steel at 100 ° C and below 75%. Although the corrosion is increased, the economy is good. The corrosion resistance of ordinary stainless steel to lye has no obvious advantages compared with cast iron. Stainless steel is not recommended as long as a small amount of iron is allowed in the medium. For high-temperature alkaline liquids, titanium and titanium alloys or high-alloy stainless steels are often used. 6. Ammonia (ammonium hydroxide) Most metals and non-metals are slightly corrosive in liquid ammonia and ammonia (ammonium hydroxide), and only copper and copper alloys are not suitable. 7. Chlorine (liquid chlorine) Most metal valves are very resistant to chlorine corrosion, especially in the case of chlorine with water, including various alloy valves. In this case, PTFE valves are a good choice, but chemical plants that produce chlor-alkali will It was found that the time required for the PTFE valve was slightly longer, the torque was increased, and the problem of PTFE aging was highlighted. The leakage occurred in this case was fatal. It can be considered to replace the original ordinary lining PTFE valve with a PTFE-filled ceramic core, which has a perfect effect by utilizing the self-lubricating property of the ceramic and the corrosion resistance of the PTFE. 8. Salt water (sea water) Ordinary steel is not too corrosive in sodium chloride solution and seawater or salt water, and generally needs to be protected by paint. All types of stainless steel also have a very low uniform corrosion rate, but may cause local corrosion due to chloride ions, usually 316 stainless steel is better. 9. Alcohols, ketones, esters, ethers Common alcohol media are methanol, ethanol, ethylene glycol, propanol, etc., ketone media are acetone, methyl ethyl ketone, etc., ester media have various methyl esters, ethyl esters, etc., ether media are methyl ether, ether, Butyl ether, etc., they are basically non-corrosive, and commonly used materials can be applied. When selecting specifically, they should also make reasonable choices according to the properties of the medium and related requirements. It is also worth noting that ketones, esters, and ethers are soluble in a variety of rubbers and avoid errors when selecting sealing materials. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Despite our efforts to promote renewable resources, oil and gas will continue to be the main force of energy in the coming decades. Since most of the traditional resources available have been exhausted, it has to be developed to make it more difficult to exploit oil and gas fields. In order to meet the rapid growth of oil and gas demand, more advanced collection methods must be used in existing oil and gas fields. The era of easy exploitation of oil and gas has ended. In the past few decades, the share of oil and gas production in offshore oil exploration platforms has increased substantially, and the rapid development of ultra-deep water exploitation is expected to maintain its growth momentum in the future. The difficulty of oil and gas exploration is increasing because the working environment is becoming more and more demanding, for example, higher temperature and pressure, and high acid environment of CO2 (high hydrogen sulfide content). Under these harsh conditions, in order to ensure the normal production of oil and gas, and more importantly, safe production, advanced technology, good equipment and high-performance materials must be available. This is where corrosion-resistant alloys come in because they are more responsive to increasingly stringent mining and production requirements. As a result, the demand for alloy steel, stainless steel and nickel alloys in the upstream oil and gas industry has increased significantly, and this trend will continue. Types of Corrosion Resistant Alloys Used in the Oil and Gas Industry The most representative corrosion resistant alloys are stainless steel and nickel alloys. In addition to typical corrosion resistant alloys, special alloy steels are also widely used in the oil and gas industry. Alloy steel and stainless steel account for 95% of the total amount, while nickel alloy accounts for only 5%, but it accounts for 25% of the total value. The demand and choice of corrosion resistant alloys depends on the production/storage environment (classified by importance): Corrosive (hydrogen sulfide, carbon dioxide, chloride) Temperature Pressure The corrosion engineer calculates the expected annual corrosion rate and then multiplies it by the design life. When the expected amount of corrosion exceeds a certain value, a corrosion-resistant alloy may be used, or carbon steel may be used, but the wall thickness is increased. In addition to the use of an overall corrosion-resistant alloy material, it is also possible to perform corrosion-resistant alloy compounding or surfacing on the surface of carbon steel or alloy steel. Another anti-corrosion measure is chemical inhibitor or cathodic protection. While safety is the first element, material selection also depends on the calculated life cycle cost. Although the initial investment in corrosion resistant alloys is large, it may be a more economical option over the entire life cycle, which reduces the number of replacements, reduces maintenance, and eliminates the need for chemical inhibitors. The order of selection of steel for oil and gas projects is carbon steel→alloy steel→13Cr martensitic stainless steel→300 series stainless steel→duplex steel (22Cr)→super duplex stainless steel (25Cr)→28Cr (alloy 28)→Ni alloy→titanium alloy. Use carbon steel and alloy steel wherever possible, as they have the lowest cost. However, as the working environment deteriorates, higher grade materials must be gradually selected, and corrosion resistant alloys are irreplaceable. The most widely used steel grades in the oil and gas industry are described in more detail below: Alloy steel: 4145H, 4130, 4140, 4330, 8630, F22 Martensitic stainless steel: 13Cr, Super13Cr, 410, 420, F6NM Austenitic stainless steel: 316, 304, 321, 317L, Nitronic 50/60, 904L254SMO (6Mo) Duplex stainless steel: 2205, 2507, LDX2101 PH steel: 17-4, 15-5, 13-8 Nickel alloy: 825, 625, 718, 925, alloy 28 Non-magnetic steel: special chromium manganese austenitic steel Corrosion-resistant alloys are required for a variety of product types, including 3D forgings, rolling rings, forged and rolled bars, welded and seamless pipes, composite pipes, slabs and strips. Corrosion-resistant alloys are used in the oil and gas industry. Special alloy steels and corrosion-resistant alloys are used in a wide range of applications, especially at sea. They can be used as drill strings, pipes, casings, downhole completions, wellheads, blowout preventers, subsea trees, manifolds, risers, oil pipes, jumpers, umbilicals, valves, pumps, water Processing equipment, etc. The following are some application examples: Oriented and horizontal drilling components are forged on a precision rotary forging press using special non-magnetic steel and then machined. The bottom hole assembly includes a drill collar, MWD and LWD tools, a downhole power drill and a drill bit. Seamless pipes are used for pipes and casings (OCTG). 13Cr, super duplex stainless steel or nickel alloy can be selected depending on the fluid composition. Need to be cold worked to increase strength. The composite welded pipe has low cost and can replace the corrosion resistant alloy pipe, the oil outlet pipe, the conveying pipe and the steel catenary riser. The composite pipe is made of carbon steel mother pipe and corrosion resistant alloy (such as 316L, 825, 625). The composite method has two techniques of metallurgy or mechanical compounding. The hose can replace the rigid oil pipe and riser. The skeleton is made of cold rolled coil. Common steel grades are 316L, economical duplex, duplex and super duplex stainless steel. Large forgings, such as blowout preventers and subsea trees. Usually made of alloy steel (F22, 8630, 4130), in order to prevent corrosion, the wet zone part is made of nickel alloy surfacing. Small forgings, such as valve bodies, also use duplex stainless steel. Large-diameter thin-wall welded pipes are used for LNG pipes (mainly 304L and 316L). The LNG cryogenic transfer line uses Invar (Alloy 36) or 9% nickel steel. Invar can also be used as a film for LNG carriers. Macro Trends and Driving Forces The application of corrosion resistant alloys in the global oil and gas industry is driven by two completely different forces: the US’s terrestrial shale oil and gas and global offshore oil and gas fields (especially deep water), which are very different, but develop The speed is very fast. Over the past five years, tremendous advances in drilling and completion technology have led to explosive growth in the production of US terrestrial shale gas. The development of horizontal drilling and hydraulic fracturing technology has freed previously unavailable resources and changed the US terrestrial resource market. In less than 10 years, the proportion of horizontal drilling rigs in the United States has increased from 10% to over 60%. In the face of the deformation of the bottom hole equipment plus the corrosive nature of shale gas and high pressure shale oil, the rig must be made of high quality materials. With the help of many factors, the use of corrosion resistant alloys at sea, especially in the deep sea, has exceeded the demand baseline. The investment in offshore projects will reach 1.2 trillion in 2013-2017, an increase of 57% over the previous five years. Investment in deep sea projects will exceed $800 billion, an increase of 60% over the previous five years. Deep sea project investment mainly comes from two aspects, one is deep sea and ultra deep sea mining in the US Gulf of Mexico, Africa and Brazil; the other is natural gas mining, especially LNG production in Asian land and floating equipment. For new deep-sea and ultra-deep sea development projects, producers face higher reservoir pressures and temperatures, and they are also learning about the experience and lessons of existing deep-sea and ultra-deep-sea development projects. As a result of increased attention to the safety and operational data of existing equipment, major oil companies and large national oil companies require their manufacturing companies to use higher grade materials for subsea equipment. As wellhead pressures reach 15,000 psi, and even higher, well flow temperatures reach 350 °C, corrosion-induced pollution, including carbon dioxide and hydrogen sulfide, and demand for high-quality materials such as stainless steel and nickel alloys will continue to grow. Although the rapid development of shale gas has significantly reduced the price of natural gas in the United States, the rapid growth of energy demand in Asian markets (including China, Japan, South Korea and India) and concerns about nuclear energy have led to an increase in LNG prices there. The growth in demand for LNG has prompted a large amount of capital to be invested in new and expanded LNG projects. The new capacity of LNG will reach 200 million t/year from 2013 to 2017. Most of this natural gas comes from offshore platforms, and liquefaction is done on land or on floating installations. Although most LNG projects are currently in shallower waters (within 500m), most offshore LNGs use underwater technology, including long-distance anchors for untreated wells. Many times the gas contains a lot of impurities, so that the steel in contact with the well flow is in a highly corrosive environment. In addition, environmental regulations in Australia and other regions are very strict, equipment must be long-lived, and maintenance-free for life. This requires manufacturers to use high-quality materials, including nickel-alloy composites or integral stainless steel tubes for subsea equipment and pipelines. Under the dual push of offshore and shale gas mining, the oil and gas industry will increase the use of stainless steel and special steel to meet technical challenges and exploit proven resources. For those companies that are willing to invest time and resources in accordance with the stringent standards of the oil and gas industry, opportunities to expand sales are everywhere. Source: China Alloy Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1 Types of stainless steel According to the chemical composition, stainless steel can be pided into Cr stainless steel, Cr-Ni stainless steel and Cr-Ni-Mo stainless steel. According to the application field, it can be pided into medical stainless steel, atmospheric corrosion resistant stainless steel, anti-oxidation stainless steel, and Cl-resistant stainless steel. However, the most commonly used classifications are classified according to the organization of steel. They are generally classified into ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, duplex stainless steel and precipitation hardened stainless steel. In petroleum and petrochemical applications, austenitic stainless steel, ferritic stainless steel and duplex stainless steel account for a large proportion. Ferritic stainless steel generally has a Cr content of between 13% and 30%, and a C content of generally less than 0.25%. After annealing or aging, carbides are precipitated at the ferrite grain boundaries to achieve corrosion resistance. In general, ferritic stainless steels have lower corrosion resistance than austenitic stainless steels and duplex steels, but higher than martensitic stainless steels. However, due to its low production cost compared to other stainless steels, it is widely used in chemical and petrochemical applications for areas where corrosion resistant media and strength are not critical. For example, it is widely used in the environment of sulfur-containing petroleum, hydrogen sulfide, room temperature nitric acid, carbonic acid, hydrogen ammonia mother liquor, high-temperature ammonia water produced by urea, urea mother liquor, and vinyl acetate and acrylonitrile produced by vitamin nylon. Martensitic stainless steel generally has a Cr content of between 13% and 17%, a high C content of between 0.1% and 0.7%, and a high strength, hardness and wear resistance, but low corrosion resistance. It is mainly used in petroleum and petrochemical applications in environments where corrosive media is not strong, such as components requiring higher toughness and impact loads, such as turbine blades, bolts and other related components. Austenitic stainless steel Cr content is between 17%-20%, Ni content is between 8%-16%, C content is generally less than 0.12%, mainly by adding Ni element to expand the austenite transformation zone, thus at room temperature The austenite structure is obtained. Austenitic stainless steel is superior to other stainless steels in corrosion resistance, plasticity, toughness, processing properties, weldability, and low temperature performance. Therefore, it is the most widely used in various fields, and its usage accounts for about all stainless steel. About 70% of the amount. In the petroleum and petrochemical field, austenitic stainless steels have great advantages in highly corrosive media and low-temperature media, such as internal components with high corrosion resistance, especially in intergranular corrosion resistant environments, such as heat exchangers/pipe fittings. Low-temperature liquefied natural gas (LNG) conveying pipeline, urea, sulfur ammonia and other production containers, flue gas dedusting and desulfurization devices. Duplex stainless steel is developed on the basis of single-phase stainless steel, and its Ni content is generally about half of the austenitic stainless steel Ni content, which reduces the alloy cost. Austenitic stainless steel has excellent corrosion resistance and high comprehensive performance. It solves the disadvantages of weak corrosion resistance of ferrite and martensitic stainless steel and insufficient strength and wear resistance of austenitic stainless steel. In the petroleum and petrochemical field, it is mainly used in marine oil platforms resistant to seawater corrosion, acidic components and equipment, especially in pitting resistant components. Precipitation-strengthened stainless steel mainly obtains high-strength properties through the precipitation strengthening mechanism. At the same time, it sacrifices its own corrosion resistance. Therefore, it is rarely used in corrosive media, and is generally used in petrochemical machinery mining and other industries. 2 stainless steel pipe in petroleum and petrochemical applications The petroleum and petrochemical industry is the pillar industry of the national economy, and it plays a pivotal role in the national economy. In the past 20 years, stainless steel pipes have been greatly improved in terms of production technology, whether they are seamless pipes or welded pipes. The stainless steel pipes produced by some domestic manufacturers have reached the level that can completely replace imported products, and the localization of steel pipes has been realized. In petroleum and petrochemical, stainless steel pipes are mainly used in pipeline transportation systems, including high pressure furnace tubes, piping, petroleum cracking tubes, fluid conveying tubes, and heat exchange tubes. Stainless steel is required to perform well in wet and acid service conditions. 2.1 Application of Stainless Steel Seamless Pipe for Large Diameter Thick Wall High Pressure Hydrogen In order to adapt to the processing of low-quality crude oil and meet the requirements of environmental protection, domestic refining and chemical enterprises continue to optimize the processing structure of refinery units and adjust the product structure. Among them, high-pressure hydrogenation units such as hydrocracking and hydrotreating have developed rapidly in recent years, and the processing capacity of the equipment It is also constantly improving. The main features of the hydrogen pipeline are large diameter and thick wall. For the selection of high-pressure hydrogen materials, due to its high temperature and high pressure conditions, TP321/H, TP347/H, etc. are generally used as materials for high-pressure hydrogen pipes at home and abroad. The above two stainless steel materials are stabilized by the addition of Ti and Nb. The element has high high temperature corrosion resistance and high temperature mechanical properties. At present, domestic large-diameter thick-walled hydrogen pipelines are mainly manufactured by hot perforation + cold rolling / cold drawing. The processing process is shown in Figure 1. The pipe made by hot perforation + cold rolling / cold drawing has the characteristics of good surface, high dimensional accuracy and uniform wall structure compared with steel pipes manufactured by other methods. For the high-pressure hydrogen-producing steel pipe, due to the particularity of the working medium, the requirements for the raw material of the steel pipe are high. Therefore, the requirements of the design institute for the high-pressure hydrogen pipeline are: S≤0.015%, P≤0.030%, non-metallic inclusion A Class B, C, and D are not higher than 1.5. Ultrasonic inspection is required for the finished pipe, and the artificial contrast defect is not more than 5% of the nominal wall thickness of the pipe. 2.2 Application of stainless steel welded steel pipe for low temperature LNG Due to the development of society, people’s awareness of environmental protection has increased, and clean energy has received more and more attention. LNG is a clean and efficient energy source that plays an important role in national production and life. Therefore, LNG receiving stations and LNG carriers have sprung up. LNG is to cool gaseous natural gas to -162 ° C under normal pressure to cause it to condense into a liquid. Therefore, the piping for LNG transportation must have high low temperature performance. For low-temperature LNG pipes, most of them are made of ultra-pure, low-carbon, low-sulfur, low-phosphorus stainless steel at home and abroad. In recent years, double-grade stainless steel has been very popular among LNG users, especially TP304/304L, TP316/316L and other applications. Shuangzheng Steel not only has L-grade corrosion resistance and low temperature performance, but also has high mechanical properties. At present, the mainstream low-temperature LNG welded stainless steel pipes at home and abroad are generally processed by automatic unit welding forming process, UOE forming process and JCO forming process. The main processes are shown in Figure 2 and Figure 3, respectively. The automatic welding unit is a fast, efficient and automatic method of producing welded pipes in the case of not thick wall. At present, most of the plates are formed by the rollers, and then welded, heat treated, etc., and some welding units are also It integrates advanced technology such as on-line ultrasonic welding, on-line welding ultrasonic, and automatic seam tracking technology to provide high-efficiency manufacturing operations for LNG long-distance pipeline manufacturing and reduce the manufacturer’s production period. UOE forming technology is currently the most widely used, most mature and most recognized quality low-temperature LNG welded pipe production process in the world, and its main process technology has been finalized. The JCO molding process is a new molding process in recent years. This molding technology is an organic combination of stepping pre-bending and tube CNC bending. For the LNG stainless steel welded pipe, since the use environment is in a low temperature environment of -162 ° C, it is necessary to have a high low temperature impact property for the LNG pipe. At present, most design institutes, research institutes, and manufacturers require that the low-temperature impact performance of LNG pipes is not less than 80J, and the lateral expansion amount is not less than 0.38mm according to ASME B 31.3. For stainless steel welded pipes, the weld is used as the weak link of the pipe. The quality of the weld directly affects the safety of the pipeline and even the pipeline. The welding coefficient is one of the important factors to evaluate the quality of the weld. For the low temperature LNG welded pipe, the welding coefficient is Ej=1.0, and the welded joint must be a full welded joint. After the welded joint is completed, all welds must be 100% ray-tested. The weld must be free of defects such as incomplete penetration, no weld inclusions, no undercuts, and no cracks to ensure the stability of the welded joint at low temperatures. 3 Prospect Oil pipelines are the bulk of stainless steel pipes. Stainless steel pipes play an important role in equipment manufacturing, oil recovery, oil refining and transportation in the petroleum industry. In recent years, the country has increased the development of petroleum resources. At the same time, as the world’s largest net oil importing country, with the increasing demand for petroleum, the petroleum-related industries will further develop and the demand for stainless steel pipes will continue. increase. In 2017, China’s steel industry has shown signs of recovery. Domestic leading stainless steel pipe companies have increased their cooperation with PetroChina and Sinopec to increase their market share. At the same time, domestic steel pipe enterprises have also carried out activities with foreign oil companies to push China’s stainless steel pipe manufacturing to the world platform.

There are many factors affecting the choice of pipeline materials: process design conditions, material properties, economy, processability, contamination of the final product, process safety, corrosion resistance, etc. Cast iron pipe: Ordinary cast iron pipe: It is mainly used for water pipe, gas main pipe, sewage pipe, etc. buried in the ground, which has good corrosion resistance to soil, acid and alkali. However, it is low in strength and brittle, so it cannot be used on pipes with high pressure or toxic or explosive media. Ferrosilicon tube high silicon iron tube: It can resist the corrosion of many strong acids. It has high hardness, is not easy to process, and is easily broken by vibration and impact. The anti-chlorinated iron tube is mainly resistant to corrosion of various temperatures and concentrations of hydrochloric acid. Carbon steel pipe: Generally not resistant to corrosion, in certain occasions, such as concentrated sulfuric acid, lye (normal temperature), can withstand certain corrosion. Not suitable for chloride ions, sensitive to stress corrosion. stainless steel pipe: Austenitic stainless steel: Austenitic stainless steel is generally a corrosion-resistant steel. It is the most widely used type of steel. Among them, 18-8 stainless steel is the most representative. It has good mechanical properties and is convenient for machining, stamping and welding. Excellent corrosion resistance and good heat resistance in an oxidizing environment. However, it is particularly sensitive to media containing chloride ions (CL-) in solution and is prone to stress corrosion. 304 stainless steel: The most commonly used stainless steel, containing a small amount of chromium and nickel, has a low carbon content and is easy to heat treat. High temperature resistance is also good, the general use temperature limit is less than 650 °C. 304 stainless steel has excellent stainless corrosion resistance and good resistance to intergranular corrosion. For oxidizing acids, it is found in the experiment that 304 stainless steel has strong corrosion resistance in nitric acid below the boiling temperature of ≤ 65%. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids. 304L stainless steel: The low carbon version of 304 is mainly for the carbon infiltration of 304 steel. The lower carbon content minimizes the precipitation of carbides in the heat affected zone near the weld, which may result in intergranular corrosion (weld erosion) in certain environments. 321 stainless steel: It is a Ni-Cr-Mo type austenitic stainless steel, and its performance is very similar to that of 304. However, due to the addition of titanium metal, it has better resistance to intergranular corrosion and high temperature strength. 321 stainless steel has excellent high temperature stress breaking performance and high temperature anti-potential performance. It is used in field open-air machines for chemical, coal and petroleum industries with high resistance to intergranular corrosion, heat-resistant parts for building materials and parts with difficult heat treatment. 316 stainless steel: Mo is added, so its corrosion resistance, atmospheric corrosion resistance and high temperature strength are particularly good, and it can be used under severe conditions. Corrosion resistance is superior to 304 stainless steel and resistant to erosion by marine and aggressive industrial atmospheres. Due to the addition of Mo, there is some corrosion resistance to dilute sulfuric acid and chlorine ion-containing solutions. 316 is more resistant to corrosion and more resistant to corrosion than 304 in high temperature environments. 316L stainless steel: The carbon content of 316L is much lower than 316; while the high carbon content is the main cause of intergranular corrosion of metal, so under the important working conditions of chemical industry, 316L is widely used, but the price of 316L is high, and 316L is resistant to chlorine. The ionic corrosion is better than 316. The high alloy content of stainless steel has a nickel content of 29% to 30% and a chromium content of more than 20%. It has good corrosion resistance to acid and hydrochloric acid and is of course more expensive. Monel tube: Monel alloy, also known as nickel alloy, is an alloy formed by adding copper, iron, manganese and other elements to the metal nickel. Monel alloy has good corrosion resistance and is a corrosion-resistant alloy with the largest amount, the most versatile and excellent comprehensive performance. The alloy has excellent corrosion resistance in hydrofluoric acid and fluorine gas media, and excellent corrosion resistance to hot concentrated alkali liquor. It is also resistant to corrosion by neutral solutions, water, sea water, the atmosphere, organic compounds, etc. An important feature of this alloy is that it generally does not produce stress corrosion cracking and has good cutting performance. Applicable temperature can be up to 500 ° C, it is more expensive than stainless steel, but in the chloride ion environment, is not sensitive to stress corrosion cracking. Hastelloy tube: It is a kind of nickel-based alloy. It is mainly pided into three series of B, C and G. It is mainly used in the case of iron-based Cr-Ni or Cr-Ni-Mo stainless steel, non-metallic materials and other strong corrosive media. It has been widely used in many fields such as petroleum, chemical industry and environmental protection. Mainly resistant to wet chlorine, various oxidizing chlorides, chloride solutions, sulfuric acid and oxidizing salts, have good corrosion resistance in low temperature and medium temperature hydrochloric acid. Therefore, in the past 30 years, in the harsh corrosive environment, such as chemical, petrochemical, flue gas desulfurization, pulp and paper, environmental protection and other industrial fields have a wide range of applications. At the earliest, Hastelloy was developed for corrosion in HCL applications. Copper and copper alloy tubes: Brass (copper and zinc alloy) is mainly used in the chemical industry, as well as tin bronze (tin added to brass), aluminum bronze, copper-nickel alloy (white copper) and the like. Copper alloys have excellent resistance to atmospheric and seawater corrosion, and are mainly characterized by uniform corrosion in general media. Brass has good corrosion resistance in the atmosphere, a variety of medium aqueous solutions, organic acids; tin bronze exhibits better corrosion resistance than brass in various corrosive media. In the process of interaction with the atmosphere and the marine environment, the surface energy of the copper alloy forms a passive or semi-passive protective film, which inhibits various corrosion. Therefore, most copper alloys exhibit excellent corrosion resistance in the atmosphere. Brass and tin bronze are mainly used in the chemical industry for valves and fittings, as well as tube bundles for heat exchangers. White copper is often used in tube bundle materials for heat exchangers that exchange heat with seawater. Titanium alloy tube: Mainly used to deal with chlorine-containing solutions, such as sea water and wet chlorine, forming an oxide film to resist corrosion. Titanium materials are used in dealing with HCL, chlorine-containing solutions, seawater, etc. PVC tube: Resistant to most inorganic acids, inorganic salt solutions, not resistant to strong sulfuric acid / strong nitric acid, not suitable for most organic solvents. In most cases, PVC pipes are suitable for wire and sewage pipes. Teflon tube: In addition to alkali, fluoride, it is resistant to almost all chemicals. The temperature can reach 250C, and the coefficient of linear expansion is 10 to 20 times that of steel; however, it is expensive, difficult to form and process, and poor in thermal conductivity. It has the characteristics of corrosion resistance, aging resistance, low friction coefficient, non-sticking property and wide temperature range. It is commonly used in conveying pipes and exhaust pipes for transporting corrosive gases. Glass steel pipe: OPR has low density and light weight. The quality of glass steel pipe is only 1/6 of that of cast iron pipe. When installing the same quality pipe, the length of glass pipe is 6 times longer than that of cast iron pipe, which greatly speeds up the construction progress and saves construction costs. . High mechanical strength, excellent impact resistance, not easily damaged by impact; Excellent durability; Excellent chemical resistance; Can withstand freezing and thawing conditions such as low temperature and thawing in cold regions, the tube will not expand and freeze and crack, nor will it produce Burst accident. The inner wall of the pipe is smooth, the resistance to the fluid is small, and the deposit is not easy to adhere. The friction loss of the medium movement is only 30% of the steel pipe, and the conveying efficiency is much higher than that of the steel pipe and the cement pipe. Non-conducting, non-heat transfer, good thermal insulation performance, good insulation, and the surface of the pipe is not easy to dew, so it can be used in a large number of heat transfer pipelines. The cost of raw materials is slightly higher than that of cast iron pipes and concrete pipes, which is close to steel pipes. However, due to its many excellent characteristics and reduced transportation and construction costs, its comprehensive cost is lower than that of traditional pipes. Large-diameter pipes are suitable for buried drainage pipes, oil pipes, etc.; small-diameter pipes are used as rainwater pipes because of their excellent impact resistance. Large-diameter glass fiber-wound glass pipes have been widely used as water supply pipes in foreign countries instead of cast iron pipes and prestressed reinforced concrete pipes. Source: China Chemical Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1. The weight calculation of stainless steel plate Weight calculation formula for stainless steel plate/stainless steel belt: weight (kg) = length (m) * width (m) * thickness (mm) * density. 304, 304L, 305, 321, 201, 202, 301, 302 Density: 7.93 316, 316L, 347, 309S, 310S Density: 7.98. 405, 410, 420 Density: 7.75 409, 430, 434 density: 7.7 2. The weight calculation of stainless steel round bar Formula for calculating the weight of stainless steel round bar: weight (kg) = diameter (mm) * diameter (mm) * length (m) * density. Chromium nickel steel density: 0.00623 Chrome steel density: 0.00609 3. The weight calculation of stainless steel hexagonal bars Weight calculation formula for stainless steel hexagonal rod: weight (kg) = opposite side (mm) * opposite side (mm) * long (m) * 0.0069 4. The weight calculation of stainless steel square rod Calculation formula for the weight of stainless steel square bar: weight (kg) = side width (mm) * side width (mm) * length (m) * 0.00793 5. The weight calculation of stainless steel pipe Weight calculation of stainless steel pipe: weight (kg) = (outer diameter mm – wall thickness mm) * wall thickness mm * 0.02491 * length m, 6. Stainless steel and other corner steel (kg / m) W = 0.00785 × [d (2b – d ) + 0.215 (R2 – 2r 2 )] b= edge width, d= edge thickness, R= inner arc radius, r= end arc radius 7. Stainless steel unequal angle steel (kg / m) W = 0.00785 × [d (B+b – d ) + 0.215 (R2 – 2 r 2 )] B = long side width, b = short side width; d = side thickness; R = inner arc radius; r = end arc radius 8. Stainless steel channel steel (kg / m) W=0.00785 ×[hd+2t (b – d )+0.349 (R2 – r 2 )] h=high; b= leg length; d= waist thickness; t=average leg thickness; R= inner arc radius r= end arc radius 9. Stainless steel I-beam (kg / m) W = 0.00785 × [hd+2t (b – d ) + 0.615 (R2 – r 2 )] h= high, b= leg length, d= waist thickness, t= average leg thickness, R= inner arc radius r = radius of the end arc; 10. The weight calculation of the flange Formula: [π*(D÷2)2-π*(K÷2)2-nπ*(L÷2)2]*C*ρ D: outer diameter of the flange; K: the diameter of the center circle of the bolt hole; L: bolt hole diameter; n: the number of bolt holes; C: flange thickness ρ: density 11. The weight calculation of the flange Formula: {[(d-D)÷2+L]-T}*T* coefficient d: the bottom width; D: top width; L: length; T: thickness; Coefficient: 304 is 0.02491, 316 is 0.02508, Q235 is 0.02466 12. The weight calculation of the size of the head Formula: [(D1+D2)÷2-T]*T*L* coefficient D1: outer diameter of the big head; D2: outer diameter of the small head; T: thickness; L: length; Coefficient: 304 is 0.02491, 316 is 0.02508, Q235 is 0.02466 13. The weight calculation of the elbow 90° elbow: (D-T)*T*(2πR÷4)* coefficient 45° elbow: [(D-T)*T*(2πR÷4)* coefficient]÷2 180° elbow: [(D-T)*T*(2πR÷4)* coefficient]*2 D: end outer diameter T: thickness R: center to end distance;

The socket pipe fittings are mainly pided into high-pressure pipe connection fittings which are formed by die-casting forging of round steel or steel ingots, and then formed by lathe machining, and the pp resin modified polypropylene low-pressure pipe is connected with the curved elastic double-ducted socket. Double-melt pipe fittings. Connection Type The socket connection series includes: socket welding connection (SW), butt welding connection (BW), threaded connection (TR), curved elastic double-melt socket connection. Pressure Level The socket fittings are subjected to pressure grades. Generally, the pressure grades of the socket welding and butt welding joints are classified into 3000LB (SCH80), 6000LB (SCH160), and 9000 (XXS). The pressure rating of the pipe fittings is pided into 2000LB, 3000LB and 6000LB. The nominal pressure of the curved elastic double-pressure pipe fittings: PN2.5MPa. Common socket fitting types: 90 degree socket welding elbow, 45 degree socket welding elbow, socket welding equal tee, socket reducer tee, socket weld union, socket weld cap, socket weld Hoop, socket welding reducer joint, socket welded pipe table, double socket pipe clamp, single socket pipe clamp, socket type pipe joint, socket welding pipe hoop, socket thread elbow, forged thread buckle Head, forged elbow, forged socket elbow, forged socket tee, forged socket tee, forged union, forged high pressure union, forged thread union, forged stainless steel Union, internal thread union, inner wire union, forged threaded union, Y-type tee, internal thread elbow, internal thread tee, internal threaded cross, female threaded hose, internal threaded pipe, Four-way, cap, plug, pipe hoop, inner wire, outer wire, concentric, eccentric head, single and double socket pipe, live joints, etc. Common standard Pipe fittings manufacturing standards refer to: CJ/T 321-2010, ASME B16.11, HG/T 21634-1996, MSS SP-83, MSS SP-79, MSS SP-97, MSS SP-95, GB/T 14383-2008 , SH/T3410-96, GD2000, GD87, 40T025-2005, etc., can also be produced according to the drawings for non-standard processing. Common materials Commonly used raw materials for socket pipe fittings are generally pided into carbon steel, stainless steel, alloy steel, polypropylene ppr and so on. Commonly used carbon steel grades are Q235, 20#, A105, etc.; Commonly used grades of stainless steel are 304, 304L, 316, 316L, 321, 00Cr17Ni14Mo2, etc.; Commonly used alloy materials are 15CrMo, 1Cr5Mo, 16Mn, 12Cr1MoV, F11, F22, 10CrMo910, etc. Other materials: copper alloy, nickel alloy, etc. Application field The socket fittings are mainly used in sectors and fields such as petrochemical, medical and health, electric power, aerospace, military, fire, metallurgy, shipbuilding, gas, nuclear power, and environmental protection, which are subject to high pressure and precision. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)