SUS 321 vs alloy 316: What are the differences?
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When comparing SUS321 stainless steel and Alloy 316 stainless steel, buyers often want to understand the difference in chemical composition, corrosion resistance, temperature performance, and cost. Both grades belong to the austenitic family, but their alloying elements and industrial applications differ significantly.
What is SUS321 Titanium?
SUS321 is a titanium-stabilized grade designed to resist intergranular corrosion in the 450–850°C range and maintain stability in high-temperature environments. It offers a tensile strength of 515 MPa, a yield strength of 205 MPa, and a continuous service temperature up to 900°C. It can be processed into various practical product forms, including plates, coils, pipes, bars, and wires.
What is Alloy 316?
316 (Alloy 316 / EN 1.4401 / UNS S31600) contains 2–3% molybdenum, offering superior pitting and crevice corrosion resistance, especially in chloride environments. Its typical tensile strength is 490–620 MPa, yield strength ≥170 MPa, and excellent performance in seawater and chemical media.
SUS321 vs Alloy 316：Equivalent materials
| Stainless Steel Grade | UNS Number | ASTM/EN Standard | Japanese (JIS) | Other International Equivalents |
|---|---|---|---|---|
| 316 | S31600 | ASTM A193 B8M / EN X5CrNiMo17-12-2 | SUS316 | STS316, 1.4401, 04Cr17Ni12Mo2 |
| 321 | S32100 | ASTM A240 Type 321 / EN X6CrNiTi18-10 | SUS321 | AFNOR Z6CNT18-10, DIN X6CrNiTi18-11, GB 0Cr18Ni10Ti, Swedish 2337, Russian GOST X6CrNiTi18-10 |
SUS321 vs Alloy 316：Chemical Composition
| Grade | C (%) | Cr (%) | Ni (%) | Mo (%) | Ti (%) | Key Purpose |
|---|---|---|---|---|---|---|
| SUS321 | ≤0.08 | 17.0–19.0 | 9.0–12.0 | - | ≥5×C | Stabilized against carbide precipitation |
| 316 (Alloy 316) | ≤0.08 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | - | Superior corrosion & chloride resistance |
SUS321 vs Alloy 316：Mechanical Properties
| Property | SUS 321 | Alloy 316 |
|---|---|---|
| Tensile Strength (MPa) | 515 | 490–620 |
| Yield Strength (MPa) | 205 | ≥170 |
| Elongation (%) | 40 | 35–40 |
| Hardness | ≤217 HB | ≤217 HB |
| Max Service Temperature | Up to 900°C | Up to 550°C |
SUS321 vs SUS 316: Corrosion Resistance
SUS316 generally exhibits superior corrosion resistance compared to SUS321, especially in humid, chloride-containing (such as marine environments), or strong acidic media. SUS316 contains more molybdenum, which enhances its corrosion resistance. SUS321, on the other hand, improves its resistance to intergranular corrosion by adding titanium, making it more suitable for high-temperature applications because it prevents carbide deposition during welding, thus avoiding intergranular corrosion.
SUS321 vs SUS 316：Heat Resistance
One of the most critical differences between 321 and 316 stainless steel is their high-temperature performance. This factor is especially important in industries such as aerospace, power generation, furnace manufacturing, and chemical processing.
| Property | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Maximum Continuous Service Temperature (air) | 870°C | 900°C |
| Maximum Continuous Service Temperature (steam) | 925°C | 950°C |
| Sensitization during welding | High risk | Very low risk due to Ti stabilization |
| Thermal Expansion Coefficient (20–100°C) | 16.0 × 10⁻⁶ /°C | 16.2 × 10⁻⁶ /°C |
Welding
Weldability is critical in fabrication, piping, and industrial installations. Both 316 and 321 stainless steels are easily weldable, but there are differences:
| Property | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Sensitization Risk | High (needs Mo or stabilized) | Very low (Ti stabilized) |
| Common Welding Methods | TIG, MIG, Spot, Resistance | TIG, MIG, Spot, Resistance |
Applications
| Industry | SUS321 | Alloy 316 |
|---|---|---|
| Heat exchangers | ✔✔ | ✔ |
| Furnaces, high-temperature ducting | ✔✔✔ | - |
| Marine equipment | - | ✔✔✔ |
| Chemical processing | ✔ | ✔✔✔ |
| Food & hygiene systems | ✔ | ✔✔ |
| Exhaust systems / thermal components | ✔✔✔ | - |
Which one is cheaper: SUS321 or SS316?
Generally, SS316 is priced slightly lower than SUS321 because SS316 uses the more common austenitic stainless steel, while SUS321 has added titanium stabilizers. For example, the typical market price for SS316 sheet is approximately $2.3-2.7/kg, while the price for SUS321 is approximately $2.6-3.1/kg.
GNEE currently has SUS 321 (UNS S32100) products in stock, including: sheets, plates, coils, strips, tubes, bars, and wires. In addition, we offer a variety of surface treatments for your selection, such as: No. 1, 2B, 2D, BA, No. 3, No. 4, HL, No. 8, sandblasting, etc.
We guarantee 100% quality. We will never deliver any defective products to our customers. Please contact us to customize your product specifications, including shape, condition, surface treatment, and processing technology.
