Materials / Grade-critical stainless
904L
- UNS
- N08904
- W.Nr
- 1.4539
- EN
- X1NiCrMoCu25-20-5
A high-alloy austenitic stainless with copper added for sulphuric acid resistance, sitting between standard stainless and the nickel alloys in both performance and price.
Composition
| Element | Min | Max |
|---|---|---|
| Ni | 23.0 | 28.0 |
| Cr | 19.0 | 23.0 |
| Mo | 4.0 | 5.0 |
| Cu | 1.0 | 2.0 |
| Mn | — | 2.0 |
| N | — | 0.10 |
| C | — | 0.020 |
| Fe | — | bal |
Per cent by weight, to the governing standard.
- Fe47.5
- Ni25.5
- Cr21.0
- Mo4.5
- Cu1.5
Per cent by weight, at the midpoint of each specified window. Elements given only as a maximum have no midpoint to take, so they sit inside the balance rather than being estimated; trace elements below 0.5 % are not shown. Indicative only; the composition table above and the governing standard are what define the limits.
Mechanical
- Tensile strength, min
- 490 MPa
- Yield strength (0.2%), min
- 220 MPa
- Elongation, min
- 35 %
- Condition
- Solution annealed
Standards by form
| Plate, sheet & strip | ASTM A240 / B625 | |
|---|---|---|
| Pipe & tube | ASTM B673 / B677 | |
| Bar | ASTM B649 |
Where it is specified
- Sulphuric and phosphoric acid service
- Good resistance to chloride pitting and stress-corrosion cracking
- Low carbon gives good as-welded performance
Diluted on nickel, because nickel is most of what it costs
904L is the natural substitute to offer against an Incoloy 825 order, and nickel is most of what it costs, so nickel is where the dilution pressure sits. Copper below the 1.0 % floor removes the sulphuric acid resistance that is the reason to choose it.
What we specify and check
- PMI reading nickel against the 23.0–28.0 % window
- Copper verified against the 1.0–2.0 % window
- Carbon verified against the 0.020 % maximum
- Confirmation the order is 904L and not a substituted 825 requirement
We commission an accredited independent laboratory to test the heat before the material leaves China. You will receive that report unedited, whether it passes or not.
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