🔩 1. 304 Stainless Steel
Type: Austenitic stainless steel
Composition: ~18% Cr, ~8% Ni
Key Properties:
Good corrosion resistance
Excellent formability and weldability
Cost-effective
Applications:
General piping systems
Food processing
Household equipment
🔩 2. 304L Stainless Steel
Type: Low-carbon version of 304
Carbon Content: ≤ 0.03%
Key Properties:
Better resistance to intergranular corrosion after welding
No need for post-weld heat treatment
Applications:
Pressure vessels
Welded piping systems
Pharmaceutical and dairy equipment
🔩 3. 316 Stainless Steel
Type: Austenitic with molybdenum (~2-3%)
Key Properties:
Superior corrosion resistance, especially to chlorides
Higher strength than 304
Applications:
Marine environments
Chemical processing
Medical devices
🔩 4. 316L Stainless Steel
Type: Low-carbon version of 316
Key Properties:
Same corrosion resistance as 316
Better weldability and stress-corrosion resistance
Applications:
High-purity systems
Offshore piping
Food-grade flanges
🔩 5. 321 Stainless Steel
Type: Titanium-stabilized austenitic
Key Properties:
Resistant to intergranular corrosion in heat-affected zones
Suitable for high-temperature service
Applications:
Heat exchangers
Jet engine parts
Exhaust systems
🔩 6. 347 Stainless Steel
Type: Niobium-stabilized austenitic
Key Properties:
Similar to 321, with better creep strength
High resistance to sensitization
Applications:
Pressure vessels
Aerospace components
Superheaters
🔩 7. 904L Stainless Steel
Type: High-alloy austenitic stainless steel
Composition: High levels of Ni (23–28%) and Cr (19–23%), plus Mo (~4–5%) and Cu (~1.5%)
Key Properties:
Excellent resistance to strong reducing acids and chloride stress corrosion
Non-magnetic
Applications:
Chemical and petrochemical industry
Seawater systems
Acid handling
✅ Summary Table
| Grade | Mo | Carbon | Corrosion Resistance | Weldability | Cost | Applications |
|---|---|---|---|---|---|---|
| 304 | No | ≤0.08% | Good | Excellent | Low | General-purpose, food, plumbing |
| 304L | No | ≤0.03% | Good (after welding) | Excellent | Low | Welded vessels, dairy, pharma |
| 316 | Yes | ≤0.08% | Very Good | Good | Medium | Marine, chemical |
| 316L | Yes | ≤0.03% | Very Good | Excellent | Medium | Offshore, high-purity |
| 321 | No | ≤0.08% | High-temp use | Excellent | Medium | Aerospace, heat systems |
| 347 | No | ≤0.08% | High-temp & creep | Excellent | Medium | Boilers, high-pressure equipment |
| 904L | Yes | ≤0.02% | Excellent | Good | High | Seawater, chemical acids |
