Stainless steel 304, often called "18/8 stainless steel," is the most widely used austenitic stainless steel grade in industrial applications worldwide. The designation "18/8" refers to its typical composition of 18% chromium and 8% nickel, which provides excellent corrosion resistance and formability for diverse manufacturing needs.
- Chromium (Cr): 18-20%
- Nickel (Ni): 8-10.5%
- Carbon (C): Maximum 0.08% (304), 0.03% (304L), 0.04-0.10% (304H)
- Manganese (Mn): Maximum 2%
- Silicon (Si): Maximum 0.75%
- Nitrogen (N): Maximum 0.10%
- Iron (Fe): Balance
The chromium content forms a protective chromium oxide film on the surface, which is what makes stainless steel "stainless." However, this doesn't mean it's completely rust-proof. As one Amazon buyer technically explained: "Stainless doesn't rust because of chromium, like 18% in 304, forms protective chromium oxide film. You can still get red rust if not properly treated. Passivation removes stray iron from surface that can create rust initiation sites."
Mechanical Properties of Stainless Steel 304
| Property | Value | Test Standard |
|---|---|---|
| Tensile Strength | 515 MPa (75 ksi) minimum | ASTM A370 |
| Yield Strength (0.2% offset) | 205 MPa (30 ksi) minimum | ASTM A370 |
| Elongation | 40% minimum in 50mm | ASTM A370 |
| Hardness | 201 HB / 92 HRB maximum | ASTM A370 |
| Density | 8000 kg/m3 | ASTM A484 |
| Melting Point | 1400-1450C | ASTM A484 |
The 304L variant (Low carbon) has a maximum carbon content of 0.03%, which prevents carbide precipitation during welding and eliminates the need for post-weld annealing in most cases. The 304H variant (High carbon) contains 0.04-0.10% carbon, designed for high-temperature service applications where enhanced strength is required.
