321 Stainless Steel (UNS S32100)
Austenitic (Ti-stabilized) · ASTM A240/A240M · Density 7.92 g/cm³
Type 321 (UNS S32100) is a titanium-stabilized austenitic stainless steel. The titanium addition prevents chromium carbide precipitation at 400–800 °C, so 321 keeps its corrosion resistance during prolonged high-temperature service — the standard choice for exhaust systems, expansion joints and heat-exchanger parts.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Ni | Ti | P | S |
|---|---|---|---|---|---|---|---|
| ≤0.08 | ≤2.00 | ≤0.75 | 17.0–19.0 | 9.0–12.0 | 5×(C+N) min, ≤0.70 | ≤0.045 | ≤0.030 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A240/A240M.
Mechanical Properties
| Tensile strength | ≥515 MPa (75 ksi) |
|---|---|
| Yield strength (0.2%) | ≥205 MPa (30 ksi) |
| Elongation (50 mm) | ≥40% |
| Max intermittent service | ≈870 °C |
Room-temperature minimum values are summarized for annealed flat product under ASTM A240/A240M unless a condition is named in the property label; product form and thickness can change the requirement.
Physical Properties & Structure
| Density | 7.92 g/cm³ |
|---|---|
| Magnetic response | Essentially non-magnetic after solution annealing; cold work can introduce a measurable magnetic response. |
| Microstructure | Austenitic (Ti-stabilized) |
Corrosion Resistance & Limits
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
Fabrication & Heat Treatment
| Welding | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. |
|---|---|
| Forming | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. |
| Machining | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. |
| Heat treatment | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. |
Equivalent Grades
The closest international equivalents of 321 Stainless Steel are 1.4541 (X6CrNiTi18-10) in the EN system, SUS321 in the JIS system, 06Cr18Ni11Ti in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S32100 |
| EN | 1.4541 (X6CrNiTi18-10) |
| JIS | SUS321 |
| GB | 06Cr18Ni11Ti |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 321 stainless steel: Sheet / Plate, Coil / Strip, Pipe / Tube, Bar.
| Finishes | No.1, 2B |
|---|---|
| Sheet / coil thickness | 0.5–6.0 mm |
| Plate thickness | 6–60 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Annealed and pickled, descaled or polished tube finish as specified; Hot rolled, peeled, bright drawn, ground or polished bar condition according to tolerance.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Exhaust manifolds and flexible pipe
- Expansion joints and bellows
- Aircraft and heater components
- Heat exchangers
Frequently Asked Questions
Why choose 321 over 304 for high temperature?
Between roughly 400 and 800 °C, standard 304 slowly forms chromium carbides at grain boundaries and loses local corrosion resistance. Titanium in 321 ties up the carbon first, so the alloy survives long service in that temperature window without sensitizing.
What is the maximum service temperature of 321?
About 870 °C for intermittent service and around 800–850 °C continuously, depending on load and atmosphere. Above that, heat-resistant grades such as 310S are the better choice.
Is 321 harder to weld than 304?
No — 321 welds with standard austenitic practice. Use a stabilized or low-carbon filler (347 is common) to keep the joint's high-temperature corrosion resistance.
321 Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201310S4104302205202301309S316Ti347904L409L4204394414442507303317L254 SMO440C17-4 PH2304
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