Stainless steel / UNS S30409
304H is a controlled high-carbon (0.04–0.10%) version of 304 that keeps higher creep and tensile strength at elevated temperatures, for boilers and pressure equipment above about 500 °C.
- UNS S30409
- W.Nr. 1.4948
- Spec ASTM A240
- Density 7.93 g/cm³
Also known as / equivalents
| System | Designation |
|---|---|
| UNS | S30409 |
| W.Nr. | 1.4948 |
| EN | X6CrNi18-10 |
| Also known as | AISI 304H, 1.4948 |
Chemical composition
| Element | Min % | Max % |
|---|---|---|
| C | 0.04 | 0.10 |
| Mn | — | 2.00 |
| P | — | 0.045 |
| S | — | 0.030 |
| Si | — | 0.75 |
| Cr | 18.0 | 20.0 |
| Ni | 8.0 | 10.5 |
| 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 | 201 HB max |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.93 g/cm³ | 0.286 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 304H: Boiler tubes, superheaters, high-temperature piping. Process piping, tanks and vessels, heat exchangers, food, dairy and pharmaceutical equipment, architectural work and general engineering.
SS 304H vs SS 304
| SS 304H | SS 304 | |
|---|---|---|
| UNS | S30409 | S30400 |
| Key property | Higher high-temperature strength | General-purpose 18/8 austenitic |
| Typical use | Boiler tubes, superheaters, high-temperature piping | Food, dairy, tanks, piping, architecture |
| Cr (wt %) | 18.0–20.0 | 17.5–19.5 |
| Ni (wt %) | 8.0–10.5 | 8.0–10.5 |
| Mo (wt %) | — | — |
| C (wt %) | 0.04–0.10 | ≤ 0.07 |
| Tensile / yield (min, MPa) | 515 / 205 | 515 / 205 |
Frequently asked questions
What is the UNS number of SS 304H?
SS 304H is designated UNS S30409 (W.Nr. 1.4948, EN X6CrNi18-10).
What is SS 304H used for?
Higher high-temperature strength. Typical uses: boiler tubes, superheaters, high-temperature piping.
Is SS 304H magnetic?
Non-magnetic when annealed; may become slightly magnetic after cold work.
In which forms can I buy SS 304H 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 304H?
Yes. Actual values are given in the Mill Test Certificate (EN 10204 3.1) supplied with each order.
What is the difference between SS 304H and SS 304?
SS 304H: higher high-temperature strength. SS 304: general-purpose 18/8 austenitic. 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.
Request a quote
Need SS 304H?
Send the grade, form, size, quantity and destination. Price on request — every offer is prepared against your specification.