Introduction:
Super austenitic stainless steel 904L is an ultra-low carbon steel with high chromium, nickel, and molybdenum-containing copper. It has good corrosion resistance, especially in phosphoric acid and sulfuric acid environments, and has excellent overall corrosion resistance. Compared with austenitic 304 stainless steel and 316L stainless steel, it has better anti-pitting and crevice corrosion, intergranular corrosion, stress corrosion cracking, and general corrosion resistance.
Therefore, it is widely used in sewage treatment, chemical, paper, and other manufacturing industries. As my country’s current chemical and other equipment manufacturing industries urgently need steel materials, it has been monopolized by foreign coauntries, and domestic manufacturers can only rely on high-priced imports.
In April 2008, TISCO successfully developed the first 904L plate in China, with various performance indicators reaching the level of imported products. Its successful development and market recognition have made TISCO the first domestic manufacturer of mass production of super austenitic stainless steel 904L medium and heavy plates, and it has also made TISCO the only domestic manufacturer that can simultaneously produce super austenitic, super duplex, and super iron. Manufacturer of ferrite and super martensitic stainless steel.
904L Stainless Steel Plate
According to the relevant person in charge of the marketing department of Taiyuan Iron and Steel, after extensive market research, super austenitic stainless steel 904L was listed as a key development product of Taiyuan Iron and Steel in 2007. In August of the same year, Taiyuan Iron and Steel set up a special national steel product development group in short supply, and the technical center established a super austenitic stainless steel development group to tackle key problems. In April 2008, mass production started. By the end of this year, the 904L cold-rolled sheet is expected to be trial-produced.
904L Chemical Composition
Grade | C | Mn | P | S | Si | Ni | Cr | Mo | Cu |
904L | ≤0.02 | ≤2.00 | ≤0.045 | ≤0.035 | ≤1.0 | 23.0-28.0 | 19.0-23.0 | 4.0-5.0 | 1.0-2.0 |
904L Mechanical Properties
Distinguish | YS（MPa） | TS（MPa） | EL | HRB |
Standard | ≥216 | ≥490 | ≥35 | ≤90 |
Actual | 340 | 624 | 46 | 175（Hv） |
â‘ Like other commonly used Cr-Ni austenitic steels, it has good cold and hot workability;
② The maximum heating temperature during hot forging can reach 1180 degrees Celsius, and the minimum forging stop temperature is not less than 900 degrees Celsius. The hot forming of this steel can be carried out at 1000-1150 degrees Celsius. The heat treatment process of the steel is 1100–1150 degrees Celsius, and it is quickly cooled after heating.
904L Welding Performance:
Although this steel can be welded by a general welding process, the most appropriate welding method is manual arc welding and argon tungsten arc welding. When manual arc welding is used to weld plates no larger than 6 mm, the electrode diameter is no more than 2.5 mm; when the plate thickness is greater than 6 mm, the electrode diameter is less than 3.2 mm.
When heat treatment is required after welding, it can be heated at 1075-1125 degrees Celsius and then quickly cooled for treatment. When using tungsten argon arc welding, the filler metal can be the same material electrode, and the weld must be pickled and passivated after welding.
904L corrosion resistance: 904L steel is mainly developed to solve the corrosion of sulfuric acid, and it is also resistant to corrosion of acetic acid at any concentration and temperature under normal pressure. It also has good corrosion resistance in formic acid, phosphoric acid, and mixed acid of formic acid and acetic acid.
The results of testing the intergranular corrosion tendency of 904L by the T method in GB1223-75 show that when the steel contains 0.038% carbon, the intergranular corrosion of this steel needs to be sensitized for more than 1 hour, so even if the welding thickness is not greater than 30mm parts At the same time, as long as the welding process is appropriate, there is no danger of intergranular corrosion.
The pitting potential measurement and pitting test results show that 904L is better than 304L (00Cr18Ni10) 316L (00Cr18Ni14Mo2) and other low-grade Cr-Ni austenitic steels. As the amount of Ni in 904L steel reaches 25%, its stress corrosion resistance is also better than that of general Cr-Ni austenitic steel. Generally speaking, in an aqueous medium containing chloride ions, when 18-8, 18-12-Mo stainless steel is used for stress corrosion cracking, choosing 904L can often prevent accidents.
Stress Corrosion Resistance of 904L Steel
| Grade | Test medium | Time for stress corrosion cracking, h |
| 00Cr18Ni10 | 40%CaCl2, Boiling temperature | <12 |
| 00Cr18Ni13Mo2 | Same as above | <12 |
| 904L | Same as above | 1000, No stress corrosion |
| 00Cr18Ni10 | 25%NaCl+1%K2Cr2O7,pH=5, boiling | <20 |
| 00Cr18Ni13Mo2 | Same as above | <321 |
| 904L | Same as above | 1000, No stress corrosion |