Austenitic Stainless Steel
904L - UNS N08904/EN 1.4539
General Characteristics:
904L is an Austenitic Steel with Nickel (25%) and Molybdenum (4.5%) providing good corrosion resistance to stress corrosion cracking in severe chloride environment. Low carbon content of 904L improves its welding characteristic by good resitance to intergranular corrosion. Annealed 904L provides excellent toughness even at sub-zero temperature. It contains a combination of chromium and molybdenum which provides it an improved level of resistance to pitting and crevice corrosion by chlorides compared to 316L Stainless Steel. The copper addition provides added resistance to reducing media such as hot phosphoric acid and dilute sulfuric acid.
Chemical Composition
| UNS / EN | %C | %Mn | %S | %P | %Si | %Ni | %Cr | %Mo | %N | %Cu | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| UNS N08904 EN 1.4539 |
Min | - | - | - | - | - | 23.0 | 19.0 | 4.00 | - | 1.00 |
| Max | 0.020 | 2.00 | 0.035 | 0.045 | 1.00 | 28.0 | 23.0 | 5.0 | 0.10 | 2.00 |
Mechanical Properties
| Mechanical Properties | UTS (MPa) | YS (MPa) | %EL | %Hardness(HRB) |
|---|---|---|---|---|
| ASTM A240 - UNS N08904 | 490 min | 220 min | 35 min | 90 HRB max |
Physical Properties:
| Density (Kg/m3) | Modules of Elasticity (Gpa) | Coefficient of thermal expansion (um/m/0C) | Thermal Conductivity (W/m 0C) | Specific Heat (J/Kg 0C) | Electrical Resistivity (uΩm) |
|---|---|---|---|---|---|
| 7950 | 195 | 15.6 | 11.5 | 450 | 95.2 |
Applications
- 904L is widely used in chemical industries for components such tanks and other products used in handling sulphuric and phosphoric acid.
- Fertilizer production equipments.
- Bleaching equipments in pulp and paper industry.
- Heat exchangers handling sea water.
Corrosion Resistance:
This alloy provides excellent general corrosion resistance and pitting or crevice corrosion that is usually higher than 316 Stainless Steel. 904L provides very good resistance to sulphuric acid, phosphoric and acetic depends on the percentage of nickel, with 25% nickel 904L offers more resistance stress corrosion cracking compared to an 8% nickel alloy like 304 Stainless Steel.
Heat Treatment
904L in annealed state provides excellent impact strength at room temperature and at cryogenic temperatures.
