Austenitic · UNS S32100
321 Stainless Steel
321 is 304 stabilized with titanium, which ties up the carbon so it cannot form chromium carbide at the weld or in elevated-temperature service. It is the grade to specify when a welded 304 part will run hot — roughly up to 800 °C in service — where ordinary 304L would lose its corrosion resistance through sensitization.
Quote within 24 working hours · Certificate type stated on the quote
Austenitic · UNS S32100 · 8.00 g/cm³
At a glance
321 Stainless — The Short Version
| Alloy family | Austenitic (UNS S32100) |
|---|---|
| Density | 8.00 g/cm³ |
| Standards | ASTM A240 · EN 10088-2 · JIS G4305 |
| Forms supplied | Stainless Steel Sheet & Plate · Stainless Steel Tube & Pipe · Stainless Steel Bar & Rod · Stainless Steel Fittings & Flanges |
Chemistry
321 Chemical Composition Limits
Percent by weight. These are the registered limits, not a typical analysis — a heat that sits anywhere inside them is still 321.
| Element | Limit (% wt) | Element | Limit (% wt) |
|---|---|---|---|
| C | 0.08 max | Mn | 2.00 max |
| P | 0.045 max | S | 0.030 max |
| Si | 0.75 max | Cr | 17.0 – 19.0 |
| Ni | 9.0 – 12.0 | Mo | — |
| N | 0.10 max |
Composition limits are the ASTM A240 registered ranges, which EN 10088-2 refers back to. Mechanical values are typical for the solution-annealed condition, not acceptance minima — the minima are set by the product standard, and the mill certificate reports the measured values for your heat.
Mechanicals
Typical Mechanical Properties (Solution Annealed)
Room temperature. Use these to compare grades — the acceptance figures for your order come from the product standard and are reported on the mill certificate for the actual heat.
| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) |
|---|---|---|---|
| Annealed | 515 | 205 | 40 |
Cold-worked tempers are available to order — values are quoted with the offer rather than assumed from this table.
Forms
321 in the Forms We Supply
The same grade behaves differently as coil, plate and tube because the forming route sets the surface and the final mechanical condition. Pick the form first.
321 Stainless Steel Sheet & Plate
Cold-rolled sheet and hot-rolled plate for structural and decorative use.
0.3 – 120 mm · 1,000 – 2,000 mm
321 Stainless Steel Tube & Pipe
Seamless and welded round, square and rectangular tube.
Wall 0.5 – 40 mm · OD 6 – 630 mm
321 Stainless Steel Bar & Rod
Round, flat, square and hexagonal bar, cold drawn or hot rolled.
Ø 3 – 600 mm · —
321 Stainless Steel Fittings & Flanges
Elbows, tees, reducers, flanges, fasteners and custom fabricated parts.
DN 15 – DN 600 · —
Selection
Choose 321 When — and When Not To
Choose 321 when
Elevated-temperature welded service — heat exchangers, exhaust systems, furnace parts and chemical plant running hot. The titanium stabilization keeps the weld resistant to intergranular corrosion without a post-weld anneal.
Think again if
General indoor or non-welded service where 304 does the job for less. The titanium adds cost and 321 is not stocked as widely, so specify it only when the heat or the weld actually calls for it.
Before you ask
321 — Questions Buyers Ask
What does titanium do in 321?
It ties up the carbon as titanium carbide instead of chromium carbide, so the chromium stays in solution and the alloy does not sensitize at weld or service temperature.
Is 321 better than 304L?
For hot service above roughly 425 °C, yes — 321 keeps its corrosion resistance at temperatures where the L grades start to sensitize. Below that, 304L is the cheaper choice.
Where is 321 used?
Aircraft exhaust, heat exchangers, furnace parts and chemical process equipment running continuously hot, typically up to about 800 °C.
Can 321 be polished like 304?
Its surface finish behavior is similar to 304, but titanium can produce fine surface streaks, so name the finish requirement clearly on the order.
Also compare
Other Stainless Grades
- 304 Stainless SteelAustenitic · UNS S30400
- 316L Stainless SteelAustenitic · UNS S31603
- 2205 Stainless SteelDuplex · UNS S32205
- 304L Stainless SteelAustenitic · UNS S30403
- 316 Stainless SteelAustenitic · UNS S31600
- 201 Stainless SteelAustenitic · UNS S20100
- 430 Stainless SteelFerritic · UNS S43000
- 310S Stainless SteelAustenitic · UNS S31008
- All stainless grades →The full stainless grade map
Quote on 321 Stainless Steel
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