GRADE PROFILE
321 stainless steel — 1.4541 / X6CrNiTi18-10
321 is a titanium-stabilised 304. With no molybdenum it holds chlorides no better than a 304L, but it takes continuous service to around 600 °C without sensitising. It is the grade of hot lines: exhaust systems, boilers, reactors.
- Austenitic
- PREN 18–20
- Cost index 115
- Welded · Seamless · Heat exchanger
- Ø 10 to 610 mm
When to choose it
On anything that runs hot and is welded. Exhaust manifolds and lines, boiler bundles, thermal process piping, reactors. Titanium prevents intergranular corrosion in heat-affected zones, which is decisive on welded assemblies that then see repeated thermal cycling.
It is also the motorsport manifold grade, where the trade-off between hot strength, formability and price is better than that of a heat-resistant grade.
When not to choose it
In chlorinated media, at any concentration. Without molybdenum, 321 behaves like a 304: it pits. Titanium only protects against sensitisation.
Where the specification calls for 321H. The H imposes a carbon range and a grain size that deliver creep strength; an ordinary 321 guarantees neither, and substituting is a compliance failure, not an approximation.
Where strictly low carbon is required: at 0.08% maximum, 321 is out of specification if the requirement caps carbon at 0.030%.
Composition
| Element | % |
|---|---|
| C | ≤ 0.08 |
| Cr | 17–19 |
| Ni | 9–12 |
| Ti | 0.3–0.7 |
| Mn | ≤ 2 |
| Si | ≤ 1 |
Mechanical properties
We only publish mechanical properties tied to a specific standard and product form — welded tube, seamless tube and bar do not share the same values, and the gap routinely exceeds 30%. The figures that apply to your specification appear on the material certificate; ask us at enquiry stage.
Designations and standards
| Reference | Designation |
|---|---|
| EN (numeric) | 1.4541 |
| EN (symbolic) | X6CrNiTi18-10 |
| ASTM / AISI | 321 |
| UNS | S32100 |
| JIS | SUS321 |
| AFNOR | — |
Tube product standards :
- EN 10216-5
- ASTM A312
- ASTM A213
Availability
Welded, seamless and heat exchanger tube, Ø 10 to 610 mm, plus fittings, flanges and bar. Partner stock or mill depending on the size and quantity. EN 10204 3.1 material certificates supplied with the goods.
Related grades
- 304L (1.4307) — the same chemistry without stabilisation, for cold service.
- 316Ti (1.4571) — titanium stabilisation with molybdenum, where there are both chlorides and heat.
- 347H (S34709) — niobium stabilisation and guaranteed creep strength, for high-temperature steam.
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Frequently asked questions
- 321 or 304L for a hot line?
- 321 as soon as there is continuous service above 400 °C on a welded assembly. Below that, or on an unwelded part, 304L is enough and costs less.
- Is 321 suitable for a motorsport exhaust?
- Yes, and it is one of its classic uses: a good balance of hot strength, bending formability and price. Beyond that, as manifold temperatures climb further, 310S takes over.
- What is the difference between 321 and 321H?
- The H imposes a minimum carbon content and a controlled grain size, both needed for the creep strength the code guarantees. A 321 may have carbon too low to creep properly. On hot pressure equipment the distinction is normative, not commercial.