Last verified 19 August 2026.
The comparison
| Property | 304 | 316L | Evidence |
|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 230 MPa | 240 MPa | E3 E3 |
| Tensile strength Rm, minimum | 540 MPa | 530 MPa | E3 E3 |
| Elongation, minimum | 45 % | 40 % | E3 E3 |
| PREN | 18 — | 24 — | E3 E3 |
| Modulus of elasticity | 200 GPa | 200 GPa | E3 E3 |
| Density | 7.9 g/cm³ | 8.0 g/cm³ | 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
Modulus of elasticity — different documents — Outokumpu Core range datasheet against Outokumpu Supra range datasheet
Density — 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 304 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
304. Availability, price and familiarity. It is stocked everywhere in every form, every fabricator has procedures for it, and for indoor, freshwater, food-contact and general architectural use it does the job at the lowest cost of any stainless. Where the environment is benign, choosing anything else needs a reason.
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 304: Chlorides, and only chlorides, most of the time. With no molybdenum its pitting resistance is materially below 316L, and coastal air, de-icing salt, swimming pool atmospheres and process water are all enough to find that out. The failure is usually cosmetic first and structural much later, which is why it tends to be discovered by a client rather than by a calculation.
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 minimum is not established here, and it is the figure most projects need.
- 304 and 304L have different minima; this page carries 304 only.
- Elevated and cryogenic temperature behaviour.
- Fatigue, fracture toughness and stress corrosion cracking. Austenitics are susceptible to chloride SCC above a threshold temperature commonly quoted around 60 °C — a rule of thumb, not sourced on this page, and not a design limit.
- Composition limits, not established.
- Composition limits are not established, and they are what a purchase order actually specifies.
- 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/304.yaml and 316l.yaml.