904L · UNS N08904 · W. Nr. 1.4539 · 015Cr20Ni25Mo4.5Cu · 2RK65
Stainless Steel 904L (N08904) (N08904): composition, properties, fittings and flanges
904L (UNS N08904, W. Nr. 1.4539) is a low carbon super austenitic stainless steel nominally containing 20 % chromium, 25 % nickel, 4.5 % molybdenum and 1.5 % copper. The high alloy content, particularly copper, gives excellent resistance to reducing acids such as dilute sulphuric acid and good resistance to phosphoric acid,…
- UNS
- N08904
- W. Nr.
- 1.4539
- Density
- 8.00 g/cm³ (0.289 lb/in³)
- Key strength
- 490 MPa / 71 ksi
Identification and standards
| Short form | 904L · UNS N08904 · W. Nr. 1.4539 · 015Cr20Ni25Mo4.5Cu · 2RK65 |
|---|---|
| Classification | Low carbon super austenitic stainless steel with copper |
| UNS | N08904 |
| Werkstoff number | 1.4539 |
| Material family | Stainless Steel |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Chromium (Cr) | 19.0 - 23.0 | Passive film, oxidising media resistance |
| Nickel (Ni) | 23.0 - 28.0 | Austenite stability, chloride SCC resistance |
| Molybdenum (Mo) | 4.0 - 5.0 | Pitting and crevice resistance |
| Copper (Cu) | 1.0 - 2.0 | Reducing acid resistance, particularly sulphuric |
| Manganese (Mn) | 2.00 max | - |
| Silicon (Si) | 1.00 max | - |
| Nitrogen (N) | 0.10 max | - |
| Phosphorus (P) | 0.045 max | - |
| Sulphur (S) | 0.035 max | - |
| Carbon (C) | 0.02 max | Low carbon for as-welded service |
| Iron (Fe) | Balance | Matrix |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (annealed, ASTM B625) | 490 MPa / 71 ksi |
|---|---|
| 0.2 % yield strength, min | 220 MPa / 32 ksi |
| Elongation in 2 in, min | 35 % |
| Typical hardness, annealed | 150 - 200 HB |
| Typical pitting resistance equivalent number | About 35 |
| Recommended service temperature range | -196 °C to 400 °C |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 8.00 g/cm³ (0.289 lb/in³) |
|---|---|
| Melting range | 1300 - 1390 °C (2370 - 2535 °F) |
| Modulus of elasticity | 195 GPa (28.3 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 12.0 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 15.3 µm/m·°C |
| Electrical resistivity at 20 °C | 0.95 µΩ·m |
Specifications by product form
| Plate / sheet / strip | ASTM B625 / ASME SB-625 |
|---|---|
| Bar / rod / shapes | ASTM B649 / ASME SB-649 |
| Seamless pipe & tube | ASTM B677 / ASME SB-677 |
| Welded pipe & tube | ASTM B673 / B674 / ASME SB-673 |
| Forgings & flanges | ASTM B649 or ASTM A182 by agreement; commonly supplied to customer specification |
| Butt weld fittings | ASTM B366 or ASTM A403 by agreement to ASME B16.9 dimensions |
| Welding consumables | Over-alloyed nickel filler such as ERNiCrMo-3 or matching 904L consumables |
| UNS / EN / China | UNS N08904 · W. Nr. 1.4539 · GB 015Cr20Ni25Mo4.5Cu |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Seamless and welded pipe and tube
- Butt weld elbows, tees, reducers and stub ends to ASME B16.9
- Forged flanges to ASME B16.5 Class 150-600
- Machined pump bodies, valve parts and heat exchanger components
Typical applications
- Sulphuric acid handling, pickling plants and acid recovery systems
- Phosphoric acid production, storage and fertiliser plant equipment
- Seawater cooling heat exchangers and condensers at moderate temperature
- Pulp and paper bleach and sulphate processes
- Pharmaceutical reactors requiring low metal ion release
- Oil and gas produced water and moderately sour gathering lines
Welding, forming and machining
- Welding
- Weld readily using GTAW or GMAW with matching 904L consumables or an over-alloyed nickel filler for critical joints. Keep interpass temperature low - about 100 °C - and use argon backing gas.
- Hot forming
- Solution anneal at 1090-1175 °C then quench rapidly in water. Hot work between 1175 °C and 950 °C.
- Machining
- High alloy content increases cutting forces. Use rigid setups, positive rake carbides, low cutting speeds and continuous feed.
- Selection advice
- Compare 904L carefully against Incoloy 825 and Hastelloy C-276. In many duties they offer much greater safety margin for a modest price increase.
Buy Stainless Steel 904L (N08904) from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.