SS321 is an austenitic stainless steel like 304 with titanium added. The titanium ties up carbon so chromium carbides do not form when the steel sits at about 430–870 °C, during welding or in service. That makes it a good choice for exhaust systems, expansion bellows, furnace parts and heat exchangers that run hot.
Quick facts
- Type
- Titanium-stabilised austenitic stainless steel
- Key addition
- Titanium, at least 5 × (C + N), max about 0.7%
- Service temperature
- Good up to about 800–870 °C in air
- Corrosion
- Similar to 304
- Magnetic
- No (annealed)
- Weldability
- Good; matching or stabilised filler wire
Equivalent grades
| Standard | Grade |
|---|---|
| AISI / ASTM | 321 |
| EN | 1.4541 (X6CrNiTi18-10) |
| UNS | S32100 |
| JIS | SUS321 |
Equivalents are close, not identical. Name the grade and standard on the drawing.
Typical chemical composition
| Element | % |
|---|---|
| Carbon (C) | 0.08 max |
| Chromium (Cr) | About 17–19 |
| Nickel (Ni) | About 9–12 |
| Titanium (Ti) | 5 × (C + N) min, about 0.7 max |
| Manganese (Mn) | Up to 2 |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
SS321 or SS304L?
| SS321 | SS304L | |
|---|---|---|
| How weld decay is avoided | Titanium ties up carbon | Very low carbon |
| Long service at 450–850 °C | Better | Can sensitise over time |
| Polishing to a mirror | Harder (titanium particles) | Easy |
| Typical use | Exhausts, bellows, furnace parts | Tanks, food and dairy equipment |
Typical uses
- Exhaust manifolds and silencers
- Expansion bellows and flexible hoses
- Heat exchangers and boiler parts
- Furnace and oven parts
- Aircraft and jet engine ducting
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Questions
- Why is titanium added to SS321?
- Titanium combines with carbon before chromium can. That stops chromium carbides forming at grain boundaries when the steel is heated, so it keeps its corrosion resistance after welding and in hot service.
- What is the maximum temperature for SS321?
- It resists scaling in air up to about 800–870 °C. For higher temperatures, SS310 is the usual choice.
- What is 321H?
- A higher-carbon version (0.04–0.10% C) for better strength at high temperature, used in pressure parts above about 500 °C.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 18 October 2026.