904L
UNS N08904
Overview
High-alloy austenitic stainless steel with superior resistance to sulfuric acid and chloride-induced pitting. The combination of high nickel (23-28%), chromium (19-23%), molybdenum (4-5%), and copper (1-2%) delivers exceptional performance in reducing acid environments. Originally developed for sulfuric acid service, it has become the premium choice for seawater cooling, phosphoric acid production, and pollution control equipment.
Chemical Composition (wt%)
| Element | Min | Max |
|---|---|---|
| C (Carbon) | — | 0.02 |
| Mn (Manganese) | — | 2 |
| Si (Silicon) | — | 1 |
| P (Phosphorus) | — | 0.045 |
| S (Sulfur) | — | 0.035 |
| Cr (Chromium) | 19 | 23 |
| Ni (Nickel) | 23 | 28 |
| Mo (Molybdenum) | 4 | 5 |
| Cu (Copper) | 1 | 2 |
Mechanical Properties
| Property | Value | Condition |
|---|---|---|
| Tensile Strength | ≥ 490 MPa (71 ksi) | — |
| Yield Strength (0.2%) | ≥ 220 MPa (31 ksi) | — |
| Elongation | ≥ 35% | — |
| Hardness | ≤ 90 HRB | annealed |
| Density | 8.0 g/cm³ | — |
Physical Properties
| Property | Value |
|---|---|
| Melting Range | 1300 – 1390 °C |
| Thermal Conductivity | 13.5 W/m·K (at 20°C) |
| PREN | 35 – 39 |
Corrosion Resistance
Superior resistance to sulfuric acid at all concentrations up to 60°C — the defining advantage. Excellent resistance to phosphoric acid, acetic acid, and formic acid. Good resistance to chloride pitting (PREN 35-39) and crevice corrosion. Resistant to stress corrosion cracking in chloride environments. Copper addition provides unique resistance to reducing acids. Performs well in seawater and brackish water.
Typical Applications
Related Standards
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