Last verified 19 August 2026.
The comparison
| Property | 304 | 304L | Evidence |
|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 230 MPa | 220 MPa | E3 E3 |
| Tensile strength Rm, minimum | 540 MPa | 520 MPa | E3 E3 |
| Elongation, minimum | 45 % | 45 % | E3 E3 |
| PREN | 18 — | 18 — | E3 E3 |
| Modulus of elasticity | 200 GPa | 200 GPa | E3 E3 |
| Density | 7.9 g/cm³ | 7.9 g/cm³ | E3 E3 |
| Thermal conductivity | 15 W/(m·K) | 15 W/(m·K) | E3 E3 |
All shared rows compare like for like.
Where each side’s numbers come from
See 304 and 304L — 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.
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.
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 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.
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.
- 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.
Generated from data/materials/304.yaml and 304l.yaml.