Stainless steel / UNS S32109
321H is the controlled high-carbon version of 321, giving higher creep strength for pressure parts operating above about 540 °C.
- UNS S32109
- W.Nr. 1.4878
- Spec ASTM A240
- Density 7.9 g/cm³
Also known as / equivalents
| System | Designation |
|---|---|
| UNS | S32109 |
| W.Nr. | 1.4878 |
| EN | X8CrNiTi18-10 |
| Also known as | AISI 321H, 1.4878 |
Chemical composition
| Element | Min % | Max % |
|---|---|---|
| C | 0.04 | 0.10 |
| Mn | — | 2.00 |
| P | — | 0.045 |
| S | — | 0.030 |
| Si | — | 0.75 |
| Cr | 17.0 | 19.0 |
| Ni | 9.0 | 12.0 |
| Ti | 4×(C+N) | 0.70 |
| Fe | Bal. | — |
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength (min) | 515 MPa (74.7 ksi) |
| Yield strength, 0.2% offset (min) | 205 MPa (29.7 ksi) |
| Elongation in 50 mm (min) | 40 % |
| Hardness | 217 HB max |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.9 g/cm³ | 0.285 lb/in³ |
| Magnetic response | Non-magnetic when annealed; may become slightly magnetic after cold work | — |
Available forms & specifications
| Form | Specification | Size range |
|---|---|---|
| Sheets, plates & coils | ASTM A240 / ASME SA240 | 0.3 mm – 6 mm |
| Seamless & welded pipe | ASTM A312 / ASME SA312 | 1/8" – 24" NB |
| Tubes | ASTM A213, A249, A269 | 1/8" – 24" NB |
| Bars & rods | ASTM A276, A479 | 3 mm – 500 mm |
| Flanges & forgings | ASTM A182 / ASME SA182 | 1/2" – 48" NB (larger on request) |
| Buttweld fittings | ASTM A403 / ASME SA403 | 1/2" – 48" NB |
| Fasteners | ASTM A193 / A194, F593 / F594 | M3 – M56 |
Corrosion & temperature resistance
Corrosion resistance rises with chromium, molybdenum and nitrogen: 304 handles general atmospheric and food-contact service, 316/317 add resistance to chlorides and pitting, 904L handles strong reducing acids, and stabilised 321/347 resist intergranular attack after welding or high-temperature exposure.
Applications
SS 321H: Refinery heaters, boilers, high-temperature piping. Process piping, tanks and vessels, heat exchangers, food, dairy and pharmaceutical equipment, architectural work and general engineering.
SS 321H vs SS 321
| SS 321H | SS 321 | |
|---|---|---|
| UNS | S32109 | S32100 |
| Key property | Higher creep strength than 321 | Titanium-stabilised, high-temperature use |
| Typical use | Refinery heaters, boilers, high-temperature piping | Exhaust systems, expansion joints, heaters |
| Cr (wt %) | 17.0–19.0 | 17.0–19.0 |
| Ni (wt %) | 9.0–12.0 | 9.0–12.0 |
| Mo (wt %) | — | — |
| C (wt %) | 0.04–0.10 | ≤ 0.08 |
| Tensile / yield (min, MPa) | 515 / 205 | 515 / 205 |
Frequently asked questions
What is the UNS number of SS 321H?
SS 321H is designated UNS S32109 (W.Nr. 1.4878, EN X8CrNiTi18-10).
What is SS 321H used for?
Higher creep strength than 321. Typical uses: refinery heaters, boilers, high-temperature piping.
Is SS 321H magnetic?
Non-magnetic when annealed; may become slightly magnetic after cold work.
In which forms can I buy SS 321H from Rajkamal Metals?
Coils & Strips, Sheets & Plates, Pipes & Tubes, Round Bars & Rods, Structural Sections, Flanges, Buttweld Fittings, Socket Weld & Threaded Fittings, Fasteners, Ferrule / Instrumentation Fittings, Dairy Fittings, Dish Ends, SS Tanks, Custom Orders. Sizes as per standard; other sizes on request.
Do you supply a Mill Test Certificate with SS 321H?
Yes. Actual values are given in the Mill Test Certificate (EN 10204 3.1) supplied with each order.
What is the difference between SS 321H and SS 321?
SS 321H: higher creep strength than 321. SS 321: titanium-stabilised, high-temperature use. See the comparison table on this page.
Last updated: 30 October 2026. Grade names identify the supply range; designations are not engineering equivalents. Availability, make, origin and documentation are confirmed at quotation.
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