December 11, 2023
Overview of 904L super austenitic stainless steel
Material grade: 904L
US grade: UNS N08904
German brand: 1.4539
Chinese brand: 00Cr20Ni25Mo4.5Cu
1. Overview of 904L (N08904, 1.4539) super austenitic stainless steel:
904L (N08904, 1.4539) super austenitic stainless steel contains 14.0-18.0% chromium, 24.0-26.0% nickel, and 4.5% molybdenum. 904L super austenitic stainless steel is a low-carbon, high-nickel, molybdenum austenitic stainless acid-resistant steel. It is a proprietary material imported from French H·S Company. It has good activation-passivation transition ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, and good corrosion resistance in neutral chlorine-containing media. Excellent resistance to pitting corrosion, as well as good resistance to crevice corrosion and stress corrosion. It is suitable for sulfuric acid of various concentrations below 70°C. It can withstand acetic acid of any concentration and temperature under normal pressure, and has good corrosion resistance in mixed acids of formic acid and acetic acid.
Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu, N08904, 1.4539) is a high-alloy austenitic stainless steel with low carbon content. It has good corrosion resistance in dilute sulfuric acid and is specially designed for environments with harsh corrosion conditions. design. It has a high chromium content and sufficient nickel content. The addition of copper makes it highly acid-resistant, especially highly resistant to chloride gap corrosion and stress corrosion cracking. It is not prone to corrosion spots and cracks, and is resistant to spots. Its corrosion resistance is slightly better than other steel types, it has good processability and weldability, and can be used in pressure vessels.
2. Chemical composition of 904L (N08904, 1.4539) super austenitic stainless steel:
C≤ Si≤ Mn≤ P≤ S≤ Cr≥ Ni≥ Mo≥ N≤
0.02 1.00 2.00 0.045 0.035 19.0-23.0 23.0-28.0 4.00-5.00 -
Others Cu≤ Fe≤ Al≤ Ti≤ Co≤ Nb≤ W≤ V≤
1.0-2.0 Margin 0.10 - - - - -
3. Metallographic structure of 904L (N08904, 1.4539) super austenitic stainless steel:
904L (N08904, 1.4539) super austenitic stainless steel has a completely austenitic structure. Compared with general austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and α phase.
4. Physical and mechanical properties of 904L (N08904, 1.4539) super austenitic stainless steel:
1. 904L (N08904, 1.4539) super austenitic stainless steel density: 8.24g/cm3.
2. 904L (N08904, 1.4539) super austenitic stainless steel tensile strength: σb≥520Mpa.
3. 904L (N08904, 1.4539) super austenitic stainless steel yield strength: σ0.2≥216Mpa
4. Elongation of 904L (N08904, 1.4539) super austenitic stainless steel: δ≥35%.
5. Corrosion resistance of 904L (N08904, 1.4539) super austenitic stainless steel:
Since the carbon content of 904L is very low (maximum 0.020%), there will be no carbide precipitation under normal heat treatment and welding. This eliminates the risk of intergranular corrosion that normally occurs after heat treatment and welding. With a higher chromium nickel molybdenum content and added copper, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content also results in a lower corrosion rate in the active state. In pure sulfuric acid in the concentration range of 0~98%, the service temperature of 904L can be as high as 40 degrees Celsius. In pure phosphoric acid with a concentration range of 0~85%, its corrosion resistance is very good. In industrial phosphoric acid produced by wet processes, impurities have a strong impact on corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In strongly oxidizing nitric acid, 904L has lower corrosion resistance than highly alloyed steels that do not contain molybdenum. In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%. within this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel.
904L steel has high resistance to pitting corrosion. Its ability to resist crevice corrosion in chloride solutions is also very good. The high nickel content of 904L reduces the corrosion rate in pits and crevices. Ordinary austenitic stainless steel may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius. This sensitivity can be reduced by increasing the nickel content of the stainless steel. Due to its high nickel content, 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.
6. Processing properties of 904L (N0804, 14539) super austenitic stainless steel:
1. Welding performance: 904L (N08904, 1.4539) super austenitic stainless steel can be welded using various welding methods. The most commonly used welding methods are manual arc welding or inert gas shielded welding. The welding rod or wire metal is based on the composition of the base metal and has higher purity, and the molybdenum content is required to be higher than the base metal. Preheating is generally not required before welding, but in cold outdoor operations, in order to avoid condensation of water vapor, the joint part or adjacent area can be heated evenly. Pay attention to the local temperature not to exceed 100°C to avoid carbon accumulation and intergranular corrosion. When welding, small linear energy, continuous and fast welding speed should be used. Generally, heat treatment is not required after welding. If heat treatment is required, it must be heated to 1100~1150℃ and then cooled quickly.
2. Machining performance: The machining characteristics of 904L (N08904, 1.4539) super austenitic stainless steel are similar to other austenitic stainless steels. There is a tendency for tool sticking and work hardening during the machining process. Carbide tools with positive rake angles must be used, and vulcanized and chlorinated oils should be used as cutting coolants. The equipment and processes should be based on reducing work hardening. During the cutting process, slow cutting speeds and feed rates should be avoided.
7. 904L (N0804, 14539) super austenitic stainless steel matching welding materials: electrode: E385-16/17, welding wire: ER385.
8. Application fields of 904L (N0804,,14539) super austenitic stainless steel:
Petroleum and petrochemical equipment, such as reactors in petrochemical equipment, etc.; sulfuric acid storage and transportation equipment, such as heat exchangers, etc.; power plant flue gas desulfurization equipment, the main parts used are: the tower body, flue, and baffle plate of the absorption tower , internal parts, spray systems, etc.; scrubbers and fans in organic acid treatment systems; seawater treatment devices, seawater heat exchangers, paper industry equipment, sulfuric acid, nitric acid equipment, acid production, pharmaceutical industry and other chemical equipment, pressure vessels , food equipment; centrifuges, reactors, etc. in pharmaceutical factories; soy sauce tanks, cooking wine, salt tanks, food machinery for equipment and dressings; equipment and components that are highly corrosive to dilute sulfuric acid media.
9. Varieties, specifications and supply status of 904L (N0804, 14539) super austenitic stainless steel:
1. Variety classification: 904L seamless pipe, 904L steel plate, 904L round steel, 904L forgings, 904L flange, 904L ring, 904L welded pipe, 904L steel strip, 904L wire and 904L supporting welding materials.
2. Delivery status: Seamless pipe: solid solution + acid whitening, length can be fixed; plate: solid solution, pickling, trimming; welded pipe: solid solution acid whitening + RT% flaw detection, forging: annealing + polishing; Bars are in forged and rolled state, surface polished or polished; strips are cold rolled, solution soft, and descaled; wires are delivered in solution pickled disk shape or straight strip shape, solid solution straight strip fine grinding Delivered in light condition.
