Overview of 904L super stainless steel;
904L super austenitic stainless steel belongs to low carbon, high nickel and high molybdenum austenitic stainless and acid-resistant steel, which is a proprietary material imported from H S company in France. It has good activation-passivation conversion ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid and phosphoric acid, good pitting corrosion resistance in neutral chlorine-containing media, and good crevice corrosion resistance and stress corrosion resistance. It is suitable for sulfuric acid with various concentrations below 70℃, and has good corrosion resistance in acetic acid with any concentration and temperature and mixed acid of formic acid and acetic acid under normal pressure.
Super austenitic stainless steel 904L is a kind of high-alloy austenitic stainless steel with low carbon content, which has good corrosion resistance in dilute sulfuric acid and is specially designed for harsh corrosion conditions. It has high chromium content and sufficient nickel content. The addition of copper has strong acid resistance, especially high resistance to chloride crevice corrosion and stress corrosion cracking, and corrosion spots and cracks are not easy to appear. The pitting corrosion resistance is slightly better than other steels, and it has good machinability and weldability, and can be used for pressure vessels.
904L Super Stainless Steel Brand:
00Cr20Ni25Mo4.5Cu (national standard), unsn08904 (standard designed by American Society of Automotive Engineers and American Society of Materials and Testing in1967 * *), DIN 1.4539 (German standard), SUS890L, Al-904L, F904L and F904L.
904L super stainless steel standard:
Feitm A240/american society of mechanical engineers SA-240(ASTM A240/ american society of mechanical engineers SA-240; The new standard classifies it as stainless steel series, and the original standard ASME SB-625 classifies it as nickel-based alloy series), ASTM A276, ASTM A182/ASME SA-182, ASTM A312/ASME A312, ASTM B625/ASME B625 and ASTM.
Metallographic structure of 904L super stainless steel:?
904L has a completely austenitic structure. Compared with ordinary high molybdenum austenitic stainless steel, 904L is insensitive to the precipitation of ferrite and α phase.
Cutting performance of 904L super stainless steel;
welding performance
Like ordinary stainless steel, 904L can be welded by various welding methods. The most commonly used welding method is manual arc welding or inert gas shielded welding. Covered electrode or welding wire metal is based on the composition of base metal, which has high purity and requires molybdenum content higher than that of base metal. Generally, preheating is not required before welding, but when working outdoors in cold weather, to avoid condensation of water vapor, the joint parts or adjacent areas can be heated uniformly. Note that the local temperature should not exceed 10 0℃ to avoid carbon deposition and intergranular corrosion. Small line energy, continuous and fast welding speed should be adopted in welding. Generally, heat treatment is not required after welding. If heat treatment is needed, it must be heated to1100 ~1150℃ and then quickly cooled.
Matching welding materials and welding technology: ER385 welding wire and E385 covered electrode are selected for 904L welding.
machinability
The processing characteristics of 904L are similar to those of other austenitic stainless steels, and there is a tendency to stick to the knife and harden during processing. Carbide cutter with positive rake angle should be used, and vulcanized and chlorinated oil should be used as cutting coolant. Equipment and technology should be based on reducing work hardening. Slow cutting speed and feed speed should be avoided during cutting.
Corrosion resistance and main application environment of 904L;
904L is a low-carbon and high-alloy austenitic stainless steel, which is designed for harsh corrosive environment. Compared with 3 16L and 3 17L, 904L has better corrosion resistance, which gives consideration to both price and performance, and has higher cost performance. Due to the addition of 1.5% copper, it has excellent corrosion resistance to reducing acids such as sulfuric acid and phosphoric acid. It also has excellent corrosion resistance to stress corrosion, pitting corrosion and crevice corrosion caused by chloride ion and good intergranular corrosion resistance. In the concentration range of 0-98%, the service temperature of 904L can be as high as 40 degrees Celsius. The corrosion resistance of pure phosphoric acid is very good in the concentration range of 0-85%. In industrial phosphoric acid produced by wet process, impurities have great influence on corrosion resistance. Among all kinds of phosphoric acid, the corrosion resistance of 904L is better than that of ordinary stainless steel. In strongly oxidizing nitric acid, the corrosion resistance of 904L is lower than that of high alloy steel without molybdenum. In hydrochloric acid, the use of 904L is limited to the lower concentration of 1-2%. In this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high pitting resistance. Its crevice corrosion resistance in chloride solution. The strength is also very good. The high nickel content of 904L reduces the corrosion rate in pits and cracks. When the temperature is higher than 60 degrees Celsius, ordinary austenitic stainless steel may be sensitive to stress corrosion in chloride-rich environment. This sensitivity can be reduced by increasing the nickel content in stainless steel. Due to the high nickel content, 904L has high stress corrosion cracking resistance in chloride solution, concentrated hydroxide solution and environment rich in hydrogen sulfide.
904L application areas:
Petrochemical equipment, such as reactors in petrochemical equipment, sulfuric acid storage and transportation equipment, such as heat exchangers, flue gas desulfurization devices in power plants, are mainly used in towers, flues, baffles, absorber internals and spray systems in organic acid treatment systems, scrubbers and fans, seawater treatment devices, seawater heat exchangers, paper industry equipment, sulfuric acid and nitric acid equipment, acid production, pharmaceutical industry and other chemical equipment. Pharmaceutical factory: centrifuges, reactors, etc. Plant food: soy sauce cans, cooking wine, salt cans, equipment and dressings, which are suitable for 904L, a medium with strong corrosiveness to dilute sulfuric acid.
Main specifications of 904L:
904L seamless pipe, 904L steel plate, 904L round steel, 904L forging, 904L flange, 904L ring, 904L welded pipe, 904L steel belt, 904L straight bar, 904L welding wire and its supporting welding materials, 904L round cake, 904L flat steel, 904L hexagon bar, 904L big head, 904L steel belt.