1. Standards & Origin
- AISI 304: Defined by the American Iron and Steel Institute (AISI), widely used in North America.
- SUS 304: Follows Japanese JIS G4304 standard, dominant in Asian markets.
Key Point: Both share similar base composition (18% Cr, 8% Ni), but differ in trace element controls.
2. Chemical Composition
| Element | AISI 304 (%) | SUS 304 (%) |
| Carbon | ≤0.08 | ≤0.08 |
| Silicon | ≤1.0 | ≤1.0 |
| Phosphorus | ≤0.045 | ≤0.045 |
| Sulfur | ≤0.03 | ≤0.03 |
| Copper | - | ≤0.3 (Optional) |
Note: SUS 304 allows trace copper addition to improve cold working performance.
3. Performance Comparison
- Corrosion Resistance
AISI 304 performs better in chloride-rich environments (e.g., coastal areas).
- Formability
SUS 304's copper content reduces cracking risk during deep drawing.
- Certification
AISI 304 often complies with ASTM A240, while SUS 304 meets JIS G4304.
4. Application in Door Hardware: Comparative Advantages
AISI 304 for High-Corrosion Environments
- Advantages:
Superior chloride resistance, ideal for coastal sliding door hardware or bathroom door hinges.
ASTM A240 certification ensures stability in humid environments (RH>85%).
- Limitations:
Higher hardness (HRB 92-95) increases machining tool wear.
SUS 304 for Complex-Structure Components
- Advantages:
Copper content improves formability, suitable for decorative sliding door hardware with curved designs.
JIS G4304 allows ±10% wider thickness tolerance for cost-sensitive projects.
Limitations:
Lower pitting resistance in salt spray tests (72h vs AISI 304's 96h).
