Data completeness: partial. Last verified 19 August 2026.
Designations
| Common name | 2304 |
| UNS | S32304 |
| EN number | 1.4362 |
| Class | Lean duplex stainless steel |
| Specified by | ASTM A240/A240M, EN 10088-2 |
2304 is the lean duplex that trades molybdenum for chromium. Roughly 23% Cr with only a trace of molybdenum gets it to the same pitting ranking as 2101 and well below 2205, while the duplex structure still gives it about twice the proof strength of 316L. The proposition is structural, not chemical: buy it when the section is strength-driven and the environment is moderate.
Properties, with what each one rests on
| Property | Value | Unit | Condition | Evidence | Source | Retrieved |
|---|---|---|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 450 | MPa | cold rolled coil and sheet, 20 °C | E3 | EN 10088-2 via Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Tensile strength Rm, minimum | 650 | MPa | cold rolled; datasheet gives a 650–850 range | E3 | EN 10088-2 via Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Elongation A, minimum | 20 | % | cold rolled; A and A80 both 20 | E3 | EN 10088-2 via Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| PREN | 26 | — | from typical composition, not from a heat | E3 | Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Density | 7.8 | g/cm³ | 20 °C | E3 | Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Modulus of elasticity | 200 | GPa | 20 °C | E3 | Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Thermal conductivity | 15 | W/(m·K) | 20 °C | E3 | Outokumpu Forta range datasheet — duplex and high-strength stainless steels | 2026-08-20 |
| Composition limits | not established | — | — | — | ASTM A240 is paywalled; the datasheet gives typical values, which are not limits | — |
| Impact toughness and the transition temperature | not established | — | — | — | not in the datasheet consulted; duplex grades have one and it governs low temperature use | — |
| Maximum service temperature | not established | — | — | — | not in the datasheet consulted; duplex grades are limited by sigma phase and 475 °C embrittlement, and the limit is not a number this page can supply | — |
7 sourced values, 3 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). Nearly twice the 316L cold rolled minimum from the same source family, and 50 MPa below 2205 on the same row. Quarto plate drops to 400 MPa, so the product form moves this number more than the choice between neighbouring duplex grades does.
PREN. 23.0% Cr, 0.3% Mo and 0.1% N give 25.6 in the datasheet’s own formula, printed as 26. Two points above 316L and nine below 2205 — the gap that decides whether a lean duplex is enough for a given 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 2304 is usually chosen for
Structural work in moderate chlorides where the alternative is thick 316L. At roughly double the proof strength, a section designed to yield can be materially thinner, and the material saving usually outruns the price premium. Tanks, bridges, reinforcement and process vessels in brackish rather than sea water are the recurring uses.
And what it is usually rejected for
Fabrication discipline and temperature ceiling. Duplex needs a controlled heat input window to keep its phase balance, so procedures have to be qualified and welders have to follow them. And like every duplex it has an upper temperature limit that austenitics do not, which rules it out of hot service entirely.
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.
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What this page does not cover
- The temperature ceiling is real but not established here as a number.
- Impact toughness and the transition temperature.
- Welding procedure guidance, heat input windows and filler selection.
- Composition limits, not established.
- Crevice corrosion, which the pitting ranking number does not predict.
Generated from data/materials/2304.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.