Stainless steel / UNS N08904
904L is a high-alloy, low-carbon austenitic stainless steel with copper, designed for sulphuric, phosphoric and other reducing acids and for strong chloride environments.
- UNS N08904
- W.Nr. 1.4539
- Spec ASTM A240
- Density 7.95 g/cm³
Also known as / equivalents
| System | Designation |
|---|---|
| UNS | N08904 |
| W.Nr. | 1.4539 |
| EN | X1NiCrMoCu25-20-5 |
| JIS | SUS890L |
| Also known as | Alloy 904L, 1.4539, SUS890L |
Chemical composition
| Element | Min % | Max % |
|---|---|---|
| C | — | 0.020 |
| Mn | — | 2.00 |
| P | — | 0.045 |
| S | — | 0.035 |
| Si | — | 1.00 |
| Ni | 23.0 | 28.0 |
| Cr | 19.0 | 23.0 |
| Mo | 4.0 | 5.0 |
| Cu | 1.0 | 2.0 |
| N | — | 0.10 |
| Fe | Bal. | — |
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength (min) | 490 MPa (71.1 ksi) |
| Yield strength, 0.2% offset (min) | 220 MPa (31.9 ksi) |
| Elongation in 50 mm (min) | 35 % |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.95 g/cm³ | 0.287 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
904L: Sulphuric acid plant, phosphoric acid, seawater cooling. Process piping, tanks and vessels, heat exchangers, food, dairy and pharmaceutical equipment, architectural work and general engineering.
904L vs SS 316L
| 904L | SS 316L | |
|---|---|---|
| UNS | N08904 | S31603 |
| Key property | High-alloy, acid resistant | Low-carbon molybdenum grade for welding |
| Typical use | Sulphuric acid plant, phosphoric acid, seawater cooling | Process piping, pharma, offshore, food |
| Cr (wt %) | 19.0–23.0 | 16.0–18.0 |
| Ni (wt %) | 23.0–28.0 | 10.0–14.0 |
| Mo (wt %) | 4.0–5.0 | 2.00–3.00 |
| C (wt %) | ≤ 0.020 | ≤ 0.030 |
| Tensile / yield (min, MPa) | 490 / 220 | 485 / 170 |
Frequently asked questions
What is the UNS number of 904L?
904L is designated UNS N08904 (W.Nr. 1.4539, EN X1NiCrMoCu25-20-5).
What is 904L used for?
High-alloy, acid resistant. Typical uses: sulphuric acid plant, phosphoric acid, seawater cooling.
Is 904L magnetic?
Non-magnetic when annealed; may become slightly magnetic after cold work.
In which forms can I buy 904L 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 904L?
Yes. Actual values are given in the Mill Test Certificate (EN 10204 3.1) supplied with each order.
What is the difference between 904L and SS 316L?
904L: high-alloy, acid resistant. SS 316L: low-carbon molybdenum grade for welding. 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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