Last verified 19 August 2026.
The comparison
| Property | 316L | 904L | Evidence |
|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 240 MPa | 240 MPa | E3 E3 |
| Tensile strength Rm, minimum | 530 MPa | 530 MPa | E3 E3 |
| Elongation, minimum | 40 % | 35 % | E3 E3 |
| PREN | 24 — | 34 — | E3 E3 |
| Modulus of elasticity | 200 GPa | 195 GPa | E3 E3 |
| Density | 8.0 g/cm³ | 8.0 g/cm³ | E3 E3 |
| Thermal conductivity | 15 W/(m·K) | 12 W/(m·K) | E3 E3 |
| Proof strength Rp0.2, minimum | 170 MPa | not established here | E3 / — |
PREN — different documents — Outokumpu Supra range datasheet against Outokumpu Ultra range datasheet
Modulus of elasticity — different documents — Outokumpu Supra range datasheet against Outokumpu Ultra range datasheet
Density — different documents — Outokumpu Supra range datasheet against Outokumpu Ultra range datasheet
Thermal conductivity — different documents — Outokumpu Supra range datasheet against Outokumpu Ultra range datasheet
The trap on this comparison
Proof strength Rp0.2 is specified twice: 170 MPa (ASTM A240/A240M, plate, annealed, 20 °C) and 240 MPa (EN 10088-2, cold rolled coil and sheet, 20 °C) — 41% apart. Both correct. Which one governs is a question about your drawing and your product form, not about the material.
Where each side’s numbers come from
See 316L and 904L — each page lists every source, every demotion and every gap. Nothing on this page is derived from anything not on those two, and our coverage limits are stated separately.
Where a PREN appears above, read it as a ranking number rather than a qualification: what PREN can and cannot tell you.
When to choose which
316L. It is the default molybdenum-bearing austenitic, and the reasons are practical rather than exceptional. Single phase, so no phase balance to manage in welding. Forgiving heat input. Formable. Stocked by everyone in every product form. Every fabricator has qualified procedures for it. When a design is not strength-driven and the environment is not aggressive, 316L is chosen because choosing anything else has to be justified.
904L. Sulphuric and phosphoric acid service, and mixed acids with chlorides in them, where austenitic grades below it corrode generally rather than pit. The copper addition is specifically there for reducing acids. Pickling lines, acid plants, flue gas cleaning and some pharmaceutical process equipment are where it earns the price.
Against 316L: Two things. Strength: at the 170 MPa ASTM A240 plate minimum it is weak for a structural section, and a strength-driven part in 316L is thick. Chlorides: the molybdenum helps against pitting relative to 304, but 316L is marginal in warm chloride service, and the failure mode that usually appears is crevice corrosion at gaskets and joints, which PREN does not predict.
Against 904L: Price, and the fact that a cheaper grade usually does the job. Where the problem is chlorides rather than acid, 2205 has a higher pitting ranking, twice the proof strength and a fraction of the alloy content; where the problem is severe chlorides, 254 SMO is the better answer. 904L gets specified out of habit more often than out of analysis.
What this comparison does not cover
- Composition limits are not established, and they are what a purchase order actually specifies.
- Elevated and cryogenic temperature behaviour.
- Fatigue, fracture toughness and stress corrosion cracking.
- Welding procedure guidance, filler selection and post-weld treatment.
- Product forms other than plate, where minima differ.
- Whether 316L suits your application. No page can answer that.
- No corrosion rate data, which is the only reason to choose this alloy over a duplex.
- Critical pitting and crevice temperatures are not established here.
- Elevated temperature strength, fatigue and fracture toughness.
- Composition limits, not established.
- Welding practice for high-alloy austenitics, including filler overmatching.
Generated from data/materials/316l.yaml and 904l.yaml.