Data completeness: partial. Last verified 19 August 2026.
Designations
| Common name | 317L |
| UNS | S31703 |
| EN number | 1.4438 |
| Class | Austenitic stainless steel |
| Specified by | ASTM A240/A240M, EN 10088-2 |
317L is 316L with a percentage point more molybdenum, and the pitting ranking moves from 24 to 28 for it. That is a real step but a small one, and it is the reason 317L occupies an awkward position: too close to 316L to justify itself in mild service, too far below the six-molybdenum grades to be trusted in seawater. Where it earns its place is flue gas desulphurisation and pulp bleaching, where the attack is acid as much as chloride.
Properties, with what each one rests on
| Property | Value | Unit | Condition | Evidence | Source | Retrieved |
|---|---|---|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 220 | MPa | Quarto plate, 20 °C | E3 | EN 10088-2 via Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Tensile strength Rm, minimum | 520 | MPa | Quarto plate; datasheet gives a 520–720 range | E3 | EN 10088-2 via Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Elongation A, minimum | 40 | % | Quarto plate; A and A80 both 40 | E3 | EN 10088-2 via Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| PREN | 28 | — | from typical composition, not from a heat | E3 | Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Density | 8.0 | g/cm³ | 20 °C | E3 | Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Modulus of elasticity | 200 | GPa | 20 °C | E3 | Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Thermal conductivity | 14 | W/(m·K) | 20 °C | E3 | Outokumpu Ultra range datasheet — high-alloy austenitic stainless steels | 2026-08-20 |
| Cold rolled and hot rolled minima | not established | — | — | — | the datasheet consulted lists only Quarto plate and wire rod for this grade | — |
| Composition limits | not established | — | — | — | ASTM A240 is paywalled; the datasheet gives typical values, which are not limits | — |
| Critical pitting temperature | not established | — | — | — | not in the datasheet consulted | — |
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). Plate, not cold rolled sheet — the datasheet consulted lists only the plate and wire rod rows for this grade. Comparing it with a cold rolled figure for another grade is comparing product forms, not materials, and the same source notes that cold rolled product generally carries higher strength values than plate.
PREN. 18.2% Cr and 3.1% Mo with no nitrogen give 28.4 in the datasheet’s own formula. Four points above 316L, fifteen below 254 SMO. A useful demonstration that the ranking scale is not linear in cost.
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 317L is usually chosen for
Flue gas desulphurisation, pulp and paper bleaching, and process streams where 316L is pitting but the environment does not justify a six-molybdenum alloy. It is also specified where an existing 316L design is being uprated without redrawing it, because the mechanical minima on plate are identical and nothing structural has to change.
And what it is usually rejected for
Availability and the size of the step. Four points of pitting ranking is a modest gain for a grade that many stockists do not hold in every form, and where the service is genuinely aggressive it is not enough. In practice the decision is usually between staying at 316L and jumping to a super-austenitic or a duplex, with 317L squeezed in between.
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
- Only plate minima are established here; sheet and hot rolled are not.
- Critical pitting temperature, which is what separates this grade from 316L in service.
- Elevated temperature strength, fatigue and fracture toughness.
- Composition limits, not established.
- Crevice corrosion, which the pitting ranking number does not predict.
Generated from data/materials/317l.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.