Development of high performance nickel base corrosion resistant alloy
Nickel base alloy is not only widely used as high temperature alloy in many industries, but also as corrosion-resistant alloy in aerospace, nuclear engineering, energy and power, transportation, oil and gas development, petrochemical industry, marine engineering and metallurgical industry and other fields. Therefore, the development and application of nickel base alloy are highly valued in various countries. With the increasingly complex and harsh service environment, especially the continuous improvement of engineering design standards, the requirements for material corrosion and protection engineering are also higher and higher, so high-performance nickel base corrosion-resistant alloy has been the focus of research and development and production in various countries.
Since the first industrial nickel base corrosion resistant alloy MONEL400 was successfully developed in 1906, the development history of corrosion resistant alloy has exceeded 100 years. In the process of commercialization and development of nickel base corrosion resistant alloy, foreign well-known enterprises have played a key role, including Yaang, Haynes International Inc., carpenter Technology Corporation, Allegheny technologies Incorporated, ATI) and Thyssen Krupp VDM. After decades of development and evolution, dozens of representative commercial alloy series have been formed. Among them, SMC company has Monel, Inconel, Incoloy, etc., with nearly 100 kinds of commercial brands; Hastelloy company has Hastelloy B, Hastelloy C, Hastelloy D, Hastelloy g, etc., with main brands are the product series of ThyssenKrupp VDM company includes nickel, cronifer, nicorros, nimofer, etc.
In addition, ArcelorMittal stainless steel and nickel alloy company (formerly imphy alloys of France), Sumitomo Metal Industries, Ltd., Nippon Yakin kogyo Co., Ltd. and other companies also occupy a place in the international nickel base corrosion resistant alloy market.
China began to copy and improve the nickel base alloys of foreign brands in 1950s, and there were more than 10 brands by the end of 1980s. There are 23 kinds of nickel base corrosion resistant alloy grades published after 1994. Compared with developed countries, China started late and its comprehensive technology level is poor. At present, representative units include Chongqing Research Institute of materials (CMRI), General Institute of iron and steel research, Baosteel Special Steel Company, Great Wall Special Steel and Fushun Special Steel, etc. After more than half a century of continuous development, the overall strength of domestic nickel base corrosion-resistant alloy has made great progress, but the problems of weak independent development ability and less original brand still exist. For many products such as B-10, C-2000, g-35 and 945, there is no reference brand in China at present, so they can only be imported.
In the process of practical application, in order to meet the market demand, companies have launched alloys with better performance to gain competitive advantage, which is an important driving force to promote the continuous development of corrosion-resistant alloys.
Alloy series, composition and performance characteristics
From the point of view of alloy system, the corrosion resistance of nickel base alloy is improved by adding CR, Mo, Cu, W and other elements. CR endows Ni with the corrosion resistance under oxidation condition, as well as the oxidation resistance and vulcanization resistance under high temperature. Mo and W significantly improve the corrosion resistance of Ni in reducing acid. Cu can improve the corrosion resistance of Ni in reducing medium. At the same time, adding CR and Mo can modify it Good corrosion resistance in oxidizing and reducing media. In addition, many precipitation hardening nickel base alloys also contain some Nb, Ti, Al and other elements. During aging, γ ‘- Ni3 (Ti, Al) and γ “- ni3nb strengthening phases can be precipitated to obtain excellent strengthening and toughening effect.
The classification of nickel base corrosion-resistant alloy can be divided according to its main alloy elements. From the binary point of view, it mainly includes Ni Cu, Ni Mo, Ni Cr and Ni Fe (or Fe Ni), and from the ternary point of view, it includes Ni Cr Mo, Ni Cr Si, Ni Cr Fe and Ni Fe CR.
Composition and performance characteristics
Ni Cu system
Ni and Cu can be infinitely miscible, with unique properties. Ni Cu system has developed into an independent series, and the most famous commercial product is Monel alloy of SMC company.
Ni70cu30 is the earliest Ni Cu alloy. Its typical commercial brand is MONEL400. It not only has high strength and toughness, but also has excellent corrosion resistance to reducing acid, strong alkali medium and sea water. It is usually used to manufacture parts working in hydrofluoric acid, brine, neutral medium, alkali salt and reductive acid medium. Its typical applications are pumps, valves, pump and impeller shafts, marine application fixings and fasteners, power and electronic components, springs, chemical equipment, oil, gas and fresh water tanks, crude oil stills, process vessels and pipelines, boiler water supply heaters and other heat exchangers, and degassing heaters.
Adding a small amount of S (0.04%) can improve the cutting performance of Ni Cu alloy, and it becomes monel r-405; adding a proper amount of Al and Ti, it becomes a precipitation strengthened Monel K-500 alloy. The mechanical properties, corrosion resistance and physical properties of r-405 alloy are basically equivalent to those of MONEL 400, but it has better machinability and is suitable for batch manufacturing of all kinds of threaded fasteners, valve parts, etc. K-500 alloy has excellent corrosion resistance and higher strength and hardness than MONEL400. It has good stability in hydrofluoric acid, alkali, sea water, H2S, H2SO4, H3PO4, organic acid and many other corrosive media, especially in hydrofluoric acid and alkali solution. Typical applications are chains, fasteners, springs, pumps, valves and pulp used in marine environment And paper production process blades, scrapers, oil and gas production process drill collars, pump shafts, impellers, non-magnetic casings, safety elevators, valves, etc. At present, there are more than 10 kinds of deformed Ni Cu alloys, the most commonly used ones are MONEL400, r-405 and K-500.
Ni Mo system
The earliest Ni Mo alloy is Hastelloy a, the starting point of its alloy composition design is to take hydrochloric acid corrosion resistance as the main goal, make full use of the characteristics of very small vapor pressure formed by the reaction of Ni, Mo and other elements with Cl2, so that these compounds are very stable and achieve corrosion resistance. However, Hastelloy a alloy can only be used in hydrochloric acid medium below 70 ℃, which is rarely used at present.
Based on Hastelloy a, Hastelloy B alloy was developed by adjusting Mo content and reducing Fe content. It can be used in any concentration of hydrochloric acid medium at boiling temperature, but the disadvantage is that the alloy is prone to intergranular corrosion in the heat affected zone of welding. Hastelloy B-2 was successfully developed by reducing the content of C and Si in the alloy. It can not only be used in any concentration of hydrochloric acid at boiling temperature, but also improve the intergranular corrosion resistance of the alloy in sensitized and post weld states.
The invention of Hastelloy B-3 has completely changed the disadvantage of Hastelloy B-2 which is easy to precipitate Ni Mo precipitate in the heat treatment process, and the processing performance has been greatly improved.
However, B series alloy is designed for reducing environment because of its low Cr content, but it is very sensitive to oxidizing medium. The 50 × 10-6 iron ion has already made the corrosion resistance of B series alloy decrease obviously. Due to the special properties of B series alloys, their application fields are relatively concentrated. The most important one is the production of acetic acid (carbonyl synthesis). In addition, some sulfuric acid recovery systems also use this series of alloys. At present, B-3 is widely used. B-2 has been gradually delisted due to the lack of processing performance. B-4 and B-10 alloys have been reported in the literature, but there is no official public information. In terms of the development of Ni Mo alloy, Hastelloy B of Hastelloy company is unique. In addition to nimofer6928 alloy (similar to b-2) and nimofer6629 alloy (similar to B-4) of ThyssenKrupp VDM and 3yc21b alloy (similar to b-2) of Chongqing Institute of materials research, other companies have few reference brands.
Ni Cr system
Ni Cr alloy is one of the most widely used alloys because of its good corrosion resistance, heat resistance and comprehensive properties, which can be used in the field of corrosion resistance and high temperature. Mo, Si, Fe, Nb, Ti, Al, W and other elements can be added to Ni cr. according to the type and content of elements, alloy varieties with different properties can be formed. Typical product lines include Inconel and Incoloy of SMC, Hastelloy C, Hastelloy D and Hastelloy g of Hastelloy, and nicrofer of ThyssenKrupp VDM.
In the development process of the above commercial alloy series, some of them show strict “composition improvement” features, such as Hastelloy C series; some show “application-oriented” features, such as Hastelloy g-35 is a Ni Cr Mo series by composition, which should belong to C series, but because it is designed for strong oxidation and mixed acid environment, it is still classified into G series. The following is a brief introduction of Ni Cr Mo, Ni Cr Si and Ni Cr Fe.
Ni Cr Mo system
The typical Ni Cr Mo commercial alloy is Hastelloy C series. Based on Hastelloy a alloy, a Hastelloy C alloy was developed by using 15% Cr instead of part of Fe and adding w element for solution treatment at high temperature. However, Hastelloy C alloy is prone to intergranular corrosion after welding, so reducing the content of C and Si properly becomes Hastelloy C-276 alloy, which has been produced since 1960s, still shows strong vitality after more than 40 years of test. Although C-276 alloy has reduced the precipitation rate and precipitation amount of precipitates in the sensitized temperature region, and greatly improved the resistance to intergranular corrosion, even if not sensitized after welding, after long-term aging at 650-1090 ℃, carbides will be precipitated at the grain boundary or co2mo6 type intermetallic compound (μ phase) will be produced, which will reduce the resistance to intergranular corrosion. On the basis of C-276, W content is reduced to zero, C content is reduced to less than 0.015%, and Fe addition ti is reduced at the same time, which makes Hastelloy C-4 alloy. The composition adjustment improved the thermal stability of the alloy and eliminated the precipitation of intermetallics and grain boundary segregation. Even at 650 ~ 1090 ℃ for a long time, C-4 alloy will not produce serious intergranular corrosion. However, the initial development of C-4 alloy is mainly to meet the needs of a small number of European users, and currently only appears in older equipment. In many corrosive environments, the corrosion resistance of C-4 and C-276 are similar, but in the strong reducing medium, C-276 performs better, and in the high oxidizing medium, C-4 has better corrosion resistance.
In high oxidation environment, only 16% of C-276 and C-4 can not provide effective corrosion resistance. The combination of high corrosion resistance and good thermal stability can be obtained by increasing Cr content and optimizing Cr, Mo and W balance. According to this design idea, Hastelloy C-22 was born. The corrosion resistance of C-22 is superior to C-276 and C-4 in high oxidation environment, but it is inferior to C-276 and alloy 59 in strong reduction environment and severe crevice corrosion condition. Therefore, C-22 is often used in flue gas desulfurization system and complex pharmaceutical reactor. On the basis of C-22, the content of Cr, Fe, W, Co, Mn, V and other elements can be reduced to zero, and the content of Ni and Mo can be increased properly. The high-strength C-22HS alloy of C-22 can be obtained. It belongs to precipitation hardening type. Through special heat treatment system, precipitation hardening phase Ni2 (Mo, Cr) can be precipitated, and the yield strength can be twice of that of C series alloy. At the same time, it has considerable corrosion resistance Yes.
Ni Cr SI system
There are not many commercial brands of Ni-Cr-Si system. At present, only d-205 series commercial alloys are produced in batches. It is a product designed for extremely strong oxidizing environment launched by Hastelloy in the early 1990s. It is based on the development of Ni-20Cr system. The typical components are 65% Ni, 20% Cr, 6% Fe, 5% Si, 2.5% Mo, 2% Cu, 0.03% C. if strictly classified according to the composition, it should be classified into Ni Cr system- According to the characteristics of the alloy, Fe system is classified into Ni Cr SI system. Compared with 316L stainless steel (fe-17cr-20ni-5si), the alloy not only has high resistance to stress corrosion and pitting corrosion, but also has excellent formability and high temperature brittleness. It is very suitable for application in high concentration of sulfuric acid and other high concentration of oxidizing acid medium. Typical application is high Plate heat exchanger in high temperature sulfuric acid environment.
Ni Cr Fe alloy is the most commercial series of nickel base alloy. Most of the Ni Cr Fe alloy produced by SMC company can be classified into Inconel series. Typical products include Inconel 600, 690, 693 and 718, etc., while products of Hastelloy company belong to Hastelloy G series, including G-3, G-30, G-35 and G-50. Due to the high content of Ni and Cr in Ni Cr Fe alloy, it has excellent corrosion resistance and oxidation resistance, especially the corrosion and oxidation resistance of oxidation resistant medium. It is not only an excellent corrosion-resistant alloy, but also an excellent high-temperature alloy. More alloys for high temperature applications, such as Inconel 601, 601gc, 706, X-750 and 751, are not described in detail in this paper.
Inconel600 has the highest Ni content and belongs to solution strengthening alloy. It has good high temperature corrosion resistance and oxidation resistance, excellent cold and hot processing and welding process performance. It has satisfactory thermal strength and high plasticity below 700 ℃ (but in reducing atmosphere containing hydrogen sulfide, its upper limit temperature is 535 ℃). Its typical applications are nuclear power generation equipment, heat exchanger, heat conversion water tube plate, bellows compensator, heat treatment steam basket, chemical evaporation tank, distiller, acid and alkali industrial machine, jet engine parts, turbojet engine afterburning parts, chlorination equipment, alkali pulp equipment, high temperature chlorine treatment equipment, heat treatment furnace parts, etc.
Compared with Inconel 600, Inconel 625, Inconel 690 alloy can be obtained by increasing Cr content by one time and balancing Ni and Fe content properly. As the Cr content is over 27%, it has remarkable anti-oxidation ability and excellent stress corrosion resistance. It is a kind of deformation alloy with excellent resistance to a variety of water-based media and high-temperature atmosphere, and also has high strength, good metallurgical stability and excellent processing characteristics. Since its introduction in the mid-1980s, Inconel 690 has attracted market attention. It is typically used as parts of heavy oil oil fired furnaces; high-pressure water vapor generating equipment, devices, and parts for pressurized water reactors; bellows compensator expansion joints, radioactive waste treatment equipment; and machines for producing glass and silicate products. It is especially suitable for making heat transfer tubes of steam generators in nuclear power plants. At present, 690 (TT) alloy tubes are mostly used as heat transfer tubes of steam generators in international PWR nuclear power plants, including Daya Bay and Qinshan Phase II in China. According to the demand of the third generation nuclear technology for 690 alloy pipe, at least 350t 690 alloy pipe is needed every year in China. Due to the high technical content of 690 (TT) alloy tube, only a few countries can produce it independently at present. The patent product inconel693 of SMC company in 1988 was designed by adding more than 2.5% Al, proper Nb and Ti, and proper reduction of Fe content on the basis of 690 composition. The high Ni and Cr content of alloy 693 endows it with excellent oxidation and vulcanization resistance. At the same time, the addition of high content of Al significantly improves the resistance of alloy to dust and other forms of high temperature corrosion. Alloy 693 is known as the alloy with the best resistance to metal dust in chemical and petrochemical environments.
Inconel 718 Alloy is a nickel base superalloy invented in 1959 in the United States. As an age hardening alloy based on Ni-Cr-Fe-Nb containing a small amount of Mo, Ti, Al and other trace beneficial elements at the same time, it has good manufacturing adaptability, weldability and resistance to welding cracks from low temperature to 650~700, and also has high yield strength, tensile strength and endurance strength. It is one of the most famous brands in Inconel series It has been widely used in the industry, not only as an ideal material for medium temperature gas turbines, but also for rings, sleeves, various forms of sheet metal parts and low-temperature storage tanks in liquid fuel rockets, aircraft and land-based gas turbines, as well as various fasteners and instrument parts. 718 is not only an excellent high-temperature alloy, but also a corrosion-resistant alloy with excellent performance, especially in the complex environment containing H2S with high corrosion resistance, which is widely used in the manufacture of acid downhole key components.
Hastelloy G-3 alloy is a Ni Cr Fe alloy with Mo and Cu added. Meanwhile, some harmful trace elements are strictly controlled to improve the corrosion resistance and weldability of the heat affected zone of the alloy. With the combination of Ni, Cr, Mo and Cu, G-3 alloy not only has excellent corrosion resistance to oxidation and reduction medium, but also has excellent resistance to stress corrosion cracking in chlorine containing environment, as well as excellent resistance to pitting and seam corrosion. It is especially suitable for engineering of reducing acid (such as sulfuric acid and phosphoric acid), flue gas desulfurization system, chemistry, pulp and paper production Air pollution control project in production. Although G-3 has been replaced by higher-level G-30 and g-35 in Hastelloy company’s product catalog, at present, G-3 alloy oil pipe is still widely used in the field of oil and gas exploration and production, especially in the sour environment oil well pipeline containing high H2S, CO2 and Cl -, G-3 has become a popular candidate material with its excellent mechanical properties and corrosion resistance.
Hastelloy G-30 is specially designed to resist the corrosion of phosphoric acid. It has been successfully used in heat exchange tubes and other components of chemical fertilizer industry. Due to the high Cr and CO content in the alloy, it has better corrosion resistance than most other nickel and iron-based alloys in the mixed environment of high oxidizing acid medium (such as nitric acid / hydrochloric acid, nitric acid / hydrofluoric acid and sulfuric acid). G-35 is an upgraded version of G-30. It was originally designed for industrial wet process phosphoric acid. It not only has higher resistance to strong oxidizing solution and mixed acid, but also has excellent resistance to local corrosion caused by halogen ions. As a new product of Hastelloy, the design of G-30 and g-35 alloy has strong pertinence, which needs further promotion and application in the market. The G-50 alloy has been reported in the literature, but there is no official information.
Ni Fe System
Compared with other series, Ni Fe System (Ni content is more than 30%, Fe + Ni content is more than 50%, also known as Fe Ni system) has a certain advantage in cost due to the increase of Fe content, up to 45%, and the decrease of Ni content, but it still remains at a high level. At the same time, it also contains elements such as Cr, Mo, Cu, Ti and al. Generally, Cr content is still more than 20%, according to ternary system Class a belongs to Ni-Fe-Cr (part belongs to Fe-Ni-Cr). Although its corrosion resistance is slightly inferior to that of Ni Cr Fe system, its main performance is basically equivalent to that of it. The commercial series mainly belongs to Incoloy and nickel, and the typical brands are Incoloy 800 (800H, 800ht), 825, 864 and 925, etc.
Incoloy 800 was launched by inco (the predecessor of SMC) in the 1950s. At that time, nickel was considered as a strategic metal. The introduction of Incoloy800 alloy was used to fill the market demand of heat-resistant and corrosion-resistant alloy with relatively low nickel content. Alloy 800 is a single-phase austenitic alloy. Due to its high temperature strength, oxidation resistance, carburization resistance and other forms of high temperature corrosion resistance, it has been widely used up to now. Typical applications include baskets, pallets and clamps in heat treatment equipment, heat exchangers and other piping systems used in chemical and petrochemical processes to require resistance to chloride stress corrosion, nuclear power Steam generator tube in the station, shell of electric heating element in household appliances, heater of cooking solution in pulp production, heat exchanger in petroleum industry, etc. As the 800 alloy with higher carbon content has higher creep and fracture properties than the material with lower carbon content, the design stress can be increased by increasing the carbon content from 0.05% to 0.05% ~ 0.10%, and increasing the requirement of average grain size to astm5 or larger, which becomes Incoloy800H alloy. In order to maintain a higher allowable design stress, control the content of C, Al and Ti within the upper limit of the specified range, and obtain a higher creep resistance and cracking performance than 800H alloy, the incoloy 800HT variant of Incoloy 800H alloy is obtained. Table 2 shows the composition (mass fraction /%), grain size requirements and service temperature comparison of 800, 800H and 800ht alloys.
Incoloy825 is a Ni Fe Cr solid solution strengthening alloy invented by inco company. It has excellent resistance to chloride ion stress corrosion cracking, pitting corrosion and crevice corrosion in reducing and oxidizing media. It can handle and store reducing acids such as sulfuric acid and phosphoric acid solution. It can also be used in nitric acid solution, nitrite and other oxidizing media. It also has Excellent seawater corrosion resistance. Its typical applications are heating pipes and vessels for sulfuric acid pickling, sea water cooling heat exchangers, marine product pipeline systems, heat exchangers, evaporators, washing and impregnating pipes for phosphoric acid production, air heat exchangers for petroleum refining, and flame-retardant alloys for oxygen weariness. Incoloy864 alloy is a high-performance and cost-effective Ni Fe Cr alloy specially developed by inco in 1998 for automobile exhaust system joints, exhaust gas recirculation pipes, manifolds and exhaust pipes. It has excellent fatigue resistance, thermal stability and resistance to hot salt corrosion, pitting corrosion and chloride stress corrosion cracking.
Incoloy 925 alloy is a kind of age hardening iron nickel base alloy invented by the United States in 1970s. As a Ni Fe Cr age hardening alloy with Mo, Cu, Ti and Al, γ – strengthening phase (Ni3 (al, Ti) is precipitated in the aging process. With the increase of temperature, other intermediate phases, including η, σ, etc., may also be precipitated. The optimized matching of Ni, Cr, Mo and Cu in the alloy not only makes it have good mechanical properties, but also has a wide range of corrosion resistance, including resistance to chloride ion stress corrosion, stress corrosion in H2S containing acid oil and gas environment, local corrosion, as well as good corrosion resistance in various reducing oxidizing media. Incoloy 925 alloy has been widely used in aviation, shipbuilding, energy and other industries. It is commonly used to manufacture parts of oil and gas drilling equipment, such as pipes, valves, stub ends, positioning joints, drilling tool joints, flanges, and also to manufacture some fasteners.
Although nickel base alloy has good corrosion resistance, excellent mechanical and physical properties, its wide application is limited because of its high nickel content and high price. When the content of Ni is further reduced to 20% – 30% and the content of Fe is increased to more than 50%, it becomes an iron-based alloy, which usually also contains high Cr content, as well as Mo, Cu, N and other elements, so the corrosion resistance and mechanical properties are better, which is usually called super stainless steel. The Mo content of some brands is as high as 6% – 7%, also known as 6Mo stainless steel or 7mo stainless steel. Early brands include B6 or 904L, B66, 20 alloy, 028 alloy and 254SMO, which have been widely used in the market. The newer brands include al-6x and AL-6XN, 654smo, 25-6mo, 1925hmo and 27-7mo. Table 3 shows the typical composition (mass fraction /%) of some super austenitic stainless steels. The results show that the super austenitic stainless steel with Mo content of more than 6% has excellent resistance to SSC, and it still has good SSC resistance when it is coupled with carbon steel after cold deformation of up to 80%. Therefore, it can be well applied in acid environment. In some acid oil and gas environment, there is a trend to replace nickel base corrosion resistant alloy, which is a great development at present Trend.
At present, the development and production of “traditional” high-performance nickel base corrosion resistant alloy is still one of the focuses in this field due to the extensive existence of harsh corrosion environment. People have been trying to develop superalloys with more outstanding properties, and at the same time, they want to have more extensive properties to adapt to a wider service environment. But this is a contradiction in itself. At present, there is no “universal” alloy, or even “universal” alloy can never be developed. Therefore, according to the requirements of the use environment, considering the performance and cost and refining the alloy development is another research trend of foreign companies. The successful development of Inconel 945 / 945x alloy of SMC company is the perfect embodiment of this concept, as shown in Table 4 (mass fraction /%). This is the embodiment that foreign companies pay great attention to the segmentation of products to improve market competitiveness.
With the continuous development of national economy, especially the rapid development of oil and gas, nuclear power, chemical energy, marine engineering, electric power and environmental protection industries, the demand for nickel base corrosion-resistant alloy is increasing. At present, the development of Nickel Base Corrosion-Resistant Alloy in China is far from meeting the market demand. Compared with developed countries, there is still a large gap, which may be in the catch-up stage for a long time. It is suggested to strengthen the relevant work from the following aspects in order to narrow the gap and promote China to become a strong country in nickel base alloy R & D and production as soon as possible, so as to provide a more solid foundation for the sustainable development of the national economy.
- (1) Strengthen the basic theoretical research of alloy, such as the theory and method of new alloy design, the influence mechanism and relationship law of alloy elements, second relative corrosion resistance, especially stress corrosion, corrosion fatigue and other properties.
- (2) Due to the high alloy content, high temperature strength, poor plasticity and narrow deformation temperature range, nickel base alloy is easy to crack and scrap in the process of hot processing, which leads to many nickel base alloy products, especially seamless steel pipes, can only be imported. Starting from microalloying, it is an important way to improve the hot working performance of nickel base alloy by strengthening the key technology, strictly controlling the content of harmful impurity elements, fine controlling the level of trace beneficial elements, and improving the pure purification and homogenization of microstructure.
- (3) Although the nickel base alloy has good strength, toughness and corrosion resistance, its price is generally high, which has become a material barrier for many new users. At the same time, with the continuous emergence of the new service environment, the requirements for material selection are becoming higher and more comprehensive. Only by strengthening the application research and technology promotion and forming a virtuous circle of the development and application feedback of new alloy, can we break through the obstacles of material selection, stimulate the development of new alloy and fully meet the market demand.
Source: China Alloy Steel Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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