Excellent Oxidation Resistance of 321 Stainless Steel
Stainless Steel 321 is a titanium-stabilized austenitic stainless steel known for its excellent resistance to intergranular corrosion, good high-temperature strength, and superior oxidation resistance up to 870 °C. It is especially suitable for prolonged service in high-temperature environments where carbide precipitation resistance is critical.
This article will introduce the composition, performance, application fields and advantages of 321 stainless steel to help you choose the right material in heat treatment equipment, chemical containers and exhaust systems.
What is 321 Stainless Steel?
321 stainless steel (UNS S32100) is an austenitic stainless steel alloy stabilized with titanium to resist sensitization—the formation of chromium carbides at grain boundaries during exposure to high temperatures. It is ideal for high-temperature structural applications, particularly in environments involving thermal cycling.
321 is essentially Type 304 with added titanium, offering similar mechanical properties but better long-term heat resistance.
321 Equivalent Grades
| Standard / System | Equivalent Designation |
| UNS | S32100 |
| ASTM / ASME | ASTM A240, A312, A479, A182 |
| EN / DIN | 1.4541 (X6CrNiTi18-10) |
| JIS | SUS 321 |
| ISO | X6CrNiTi18-10 |
321 Chemical Composition
| Element | Content (%) |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | ≥ 5 × C and ≤ 0.70 |
| Carbon (C) | ≤ 0.08 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Iron (Fe) | Balance |
321 Mechanical Properties
| Property | Typical Value |
| Tensile Strength | ≥ 515 MPa |
| Yield Strength | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Hardness (HBW) | ≤ 217 |
321 Physical Properties
| Property | Value |
| Density | 7.9 g/cm³ |
| Melting Point | 1398–1446 °C |
| Thermal Conductivity | ~16.2 W/m·K |
| Electrical Resistivity | ~0.73 µΩ·m |
| Modulus of Elasticity | ~193 GPa |
| Service Temperature | Continuous up to ~870 °C |
Applications of 321 Stainless Steel
- Exhaust Systems: Automotive and aerospace exhaust manifolds, heat shields.
- Heat Exchangers: Tubes and pipes in refinery and petrochemical industries.
- Furnace Parts: Thermal processing baskets, radiant tubes.
- Chemical Processing: Vessels, tanks, and piping handling oxidizing acids.
- Boiler and Superheater Components: Especially in power generation.
Advantages of 321
- Excellent resistance to intergranular corrosion after welding or exposure to elevated temperatures.
- Good creep and stress rupture strength at temperatures above 600 °C.
- Similar weldability and formability to 304, but with better thermal stability.
- No post-weld annealing required for most applications.
Limitations of 321
- Not suitable for reducing acid environments like sulfuric or hydrochloric acid.
- Lower corrosion resistance than molybdenum-alloyed grades like 316.
- Limited resistance to strong chloride pitting or crevice corrosion.
- Not recommended for cryogenic service—use 304L or 316L instead.
321 vs Other Stainless Steels
| Feature | 304 | 321 | 316L |
| Titanium Stabilized | No | Yes | No |
| Intergranular Corrosion Resistance | Moderate | Excellent | Good |
| Oxidation Resistance | Good | Excellent | Very Good |
| High-Temp Strength | Good | Very Good | Good |
| Chloride Resistance | Moderate | Moderate | High |
| Cost | Low | Moderate | High |
Summary
321 stainless steel is an excellent choice for high-temperature environments where resistance to oxidation and intergranular corrosion is critical. Its titanium stabilization makes it especially valuable for welded structures or equipment subjected to thermal cycling.
MT.BOLTS supplies 321 stainless steel fasteners, bars, pipes, flanges, and fittings for use in high-temperature, structural, and process applications. Contact us for technical support or to request a quote.
