SUS321 vs. SUS316 Stainless Steel: How to Choose the Best One for Your Project?
Apr 16, 2025
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SUS321 vs. SUS316 Stainless Steel: How to Choose the Best Material for Your Project?
When designing industrial equipment, piping systems, heat exchangers, or chemical installations, selecting the right stainless steel is essential to ensure reliability and long service life. SUS321 and SUS316 are both austenitic stainless steels known for their corrosion resistance, but their different alloying elements and characteristics make them suitable for distinct applications.
This guide compares SUS321 and SUS316 in terms of chemical composition, corrosion resistance, high-temperature behavior, weldability, and application fields to help you make the best material selection.
1. SUS321 vs. SUS316 Stainless Steel：Chemical Composition
| Property | SUS321 | SUS316 |
|---|---|---|
| Basic Type | Austenitic (Titanium-stabilized) | Austenitic (Molybdenum-enhanced) |
| Main Alloying Elements | Cr 17–19%, Ni 9–12%, Ti 0.3–0.8% | Cr 16–18%, Ni 10–14%, Mo 2–3% |
| Key Features | Excellent intergranular corrosion resistance, high-temperature stability | Superior resistance to pitting and crevice corrosion |
2. SUS321 vs. SUS316 Stainless Steel：Corrosion Resistance Comparison
| Environment | SUS321 Performance | SUS316 Performance |
|---|---|---|
| General Atmospheric | Excellent, suitable for outdoor and mild climates | Even better, ideal in marine or humid environments |
| Chloride-Rich (e.g., seawater) | Moderate pitting resistance, not recommended | Excellent resistance due to Mo content |
| Acidic Media | Suitable for mild acids (e.g., phosphoric acid) | More suitable for sulfuric, acetic, and other corrosive acids |
| Intergranular Corrosion | Very low risk, ideal for post-weld structures | Good with low-carbon grades or stabilization treatment |
3. SUS321 vs. SUS316 Stainless Steel：High-Temperature Performance
| Feature | SUS321 | SUS316 |
|---|---|---|
| Continuous Use Temp | Up to 870°C | Recommended ≤ 550–600°C |
| Creep Resistance | Excellent, suitable for heat exchangers and high-temp pipes | Moderate, best for medium-temp use |
| Oxide Scale Stability | Strong (resistant to flaking) | Slightly weaker |
4.Mechanical Properties Comparison: SUS321 vs SUS316 Stainless Steel
| Property | SUS321 | SUS316 |
|---|---|---|
| Tensile Strength (MPa) | 520–750 | 515–760 |
| Yield Strength (0.2% offset, MPa) | ≥205 | ≥205 |
| Elongation (%) | ≥40 | ≥40 |
| Brinell Hardness (HB) | ≤187 | ≤217 |
| Impact Toughness (J/cm²) | Good | Good |
| Elastic Modulus (GPa) | ~193 | ~193 |
| Density (g/cm³) | 7.92 | 7.99 |
5. SUS321 vs. SUS316 Stainless Steel：Weldability and Fabrication
| Metric | SUS321 | SUS316 |
|---|---|---|
| Weldability | Excellent, low intergranular corrosion risk | Excellent, requires controlled heat input |
| Workability | Good | Better, more ductile |
| Recommended Filler | ER321 (with Ti), ER347 (with Nb) | ER316L or ER316LSi |
6. SUS321 vs. SUS316 Stainless Steel： Application
| Application | SUS321 | SUS316 |
|---|---|---|
| Petrochemical heat exchangers, gas ducts | ✅ High-temp durability | ❌ Not ideal above 600°C |
| Aerospace/automotive exhaust systems | ✅ Vibration-resistant, Ti-stabilized | ❌ Not suitable for high-temp sensitization |
| Marine equipment | ❌ Prone to pitting | ✅ Excellent in seawater environments |
| Food & pharmaceutical equipment | ✅ Usable in non-chloride settings | ✅ Preferred for high hygiene and corrosion resistance |
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