Last verified 19 August 2026.
The comparison
| Property | 304L | 316L | Evidence |
|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 220 MPa | 240 MPa | E3 E3 |
| Tensile strength Rm, minimum | 520 MPa | 530 MPa | E3 E3 |
| Elongation A, minimum | 45 % | 40 % | E3 E3 |
| PREN | 18 — | 24 — | E3 E3 |
| Density | 7.9 g/cm³ | 8.0 g/cm³ | E3 E3 |
| Modulus of elasticity | 200 GPa | 200 GPa | E3 E3 |
| Thermal conductivity | 15 W/(m·K) | 15 W/(m·K) | E3 E3 |
| Proof strength Rp0.2, minimum | not established here | 170 MPa | — / E3 |
PREN — different documents — Outokumpu Core range datasheet against Outokumpu Supra range datasheet
Density — different documents — Outokumpu Core range datasheet against Outokumpu Supra range datasheet
Modulus of elasticity — different documents — Outokumpu Core range datasheet against Outokumpu Supra range datasheet
Thermal conductivity — different documents — Outokumpu Core range datasheet against Outokumpu Supra 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 304L and 316L — 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
304L. Welded fabrication that has to stay corrosion resistant at the weld. That is the whole argument. Everything else about it — price, availability, formability, the fact that every shop already knows how to handle it — is inherited from 304. If a part is welded and will see moisture, specifying 304L costs almost nothing and removes a failure mode that is invisible until it is not.
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.
Against 304L: Two reasons, in order of how often they bite. Strength: the EN cold rolled minima are the lowest in the austenitic family, and a strength-driven section in 304L is heavy. Chlorides: with no molybdenum it is no better than 304, and coastal air, de-icing salt and process water all find that out. For welded service in chlorides the honest step up is 316L, not 304L.
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.
What this comparison does not cover
- The ASTM plate minima are not established here, and they are the figures most North American projects need.
- The 0.03% carbon maximum that defines the grade is not sourced on this page.
- Elevated and cryogenic temperature behaviour, and the creep range.
- Fatigue, fracture toughness and chloride stress corrosion cracking.
- Sensitisation behaviour after long exposure in the 450–850 °C range, which the low carbon delays rather than prevents. Not sourced here; the standard and the mill datasheet are the routes.
- Whether 304L suits your application. No page can answer that.
- 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.
Generated from data/materials/304l.yaml and 316l.yaml.