304 — what the data actually supports

Data completeness: partial. Last verified 19 August 2026.

Designations

The most widely produced stainless steel in the world, and the baseline everything else is compared against. No molybdenum, which is the whole difference from 316: cheaper, equally weldable, and materially worse in chlorides. The low-carbon variant 304L (S30403, EN 1.4307) carries slightly lower minima and is the one to specify where welded sections must keep their corrosion resistance.

Properties, with what each one rests on

7 sourced values, 2 gaps named. Publishing the gaps is more useful than filling them from an aggregator that does not say where its numbers came from. The routes to filling them are the standard itself, a mill datasheet, or a mill certificate for your actual heat — which supersedes both at E5.

Where the numbers come from

Proof strength Rp0.2, minimum (EN). The ASTM A240 plate minimum for 304 is a different figure and was not sourced for this page. Do not carry this number onto an ASTM-governed drawing.

PREN. Corrected on 20 August 2026. The earlier note said the source stated neither its formula nor its composition; it states both — PRE = %Cr + 3.3 × %Mo + 16 × %N, and 18.1% Cr with no molybdenum and no nitrogen, which reproduces the printed 18. It stays at E3 because the composition is a typical value, not a heat analysis. Well below any threshold usually adopted for chloride service.

Why we do not just copy an aggregator. Because then this page would be a worse copy of MatWeb with no way for you to tell which rows to trust, and the one thing we have that MatWeb does not is the evidence column. Our coverage and its limits.

What 304 is usually chosen for

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.

And what it is usually rejected for

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.

The number to be more careful with than any of the above is the difference between a specified minimum and a typical value — a floor the standard guarantees, versus what a supplier’s production usually does. The full version, and the most expensive routine mistake in material data.

Compare

304 vs 316l · 304 vs 304l

What this page 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.

Generated from data/materials/304.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.