Data completeness: partial. Last verified 19 August 2026.
Designations
| Common name | 444 |
| UNS | S44400 |
| EN number | 1.4521 |
| Class | Ferritic stainless steel |
| Specified by | EN 10088-2 |
444 is the ferritic with molybdenum in it, and it is the most interesting substitution argument in the stainless family: the same pitting ranking number as 316L, at PREN 25 against 24, with no nickel in the composition and therefore none of the nickel price in the invoice. What it does not inherit from 316L is toughness, formability or weldability, and those are the reasons the substitution does not happen more often than it does.
Properties, with what each one rests on
| Property | Value | Unit | Condition | Evidence | Source | Retrieved |
|---|---|---|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 300 | MPa | cold rolled coil and sheet, 20 °C | E3 | EN 10088-2 via Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| Tensile strength Rm, minimum | 420 | MPa | cold rolled; datasheet gives a 420–640 range | E3 | EN 10088-2 via Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| PREN | 25 | — | from typical composition, not from a heat | E3 | Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| Density | 7.7 | g/cm³ | 20 °C | E3 | Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| Modulus of elasticity | 220 | GPa | 20 °C | E3 | Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| Thermal conductivity | 23 | W/(m·K) | 20 °C | E3 | Outokumpu Supra range datasheet — molybdenum-alloyed austenitic stainless steels | 2026-08-20 |
| Elongation A, minimum | not established | — | — | — | the elongation cells are blank in the datasheet row consulted, for every product form | — |
| Impact toughness and the ductile-to-brittle transition temperature | not established | — | — | — | not in the datasheet consulted; for a ferritic this governs thickness and minimum service temperature | — |
| Composition limits | not established | — | — | — | the datasheet gives typical values, which are not limits, and the standard is paywalled | — |
6 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). 25% above the 316L row in the same table and the same product form. Hot rolled sits at 280 MPa, Quarto plate back at 300 MPa — an unusual pattern, and a reason to read the form column rather than the grade row.
Tensile strength Rm, minimum. Below the 316L minimum, while proof strength is above it. The gap between yield and tensile is narrow, which is what a ferritic looks like and what limits its forming.
PREN. 18.0% Cr and 2.0% Mo give 24.6 in the datasheet’s own formula, printed as 25 — one point above 316L in the same table. Read it as a ranking, not as a qualification: the two alloys have different failure modes and the number does not describe crevice behaviour at all.
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 444 is usually chosen for
Hot water tanks, heat exchangers and process equipment in mild chlorides where nickel price volatility is the problem being solved. It sits at the pitting ranking of 316L without nickel, conducts heat better, expands less and does not suffer chloride stress corrosion cracking — which for a hot water application is the failure mode that actually occurs.
And what it is usually rejected for
Anything that has to be formed hard, welded thick, or stay tough cold. Elongation is not even quoted on the row consulted, weld zones lose toughness, and the transition temperature makes heavy section a bad idea. It is also thinly stocked compared with 316L, so a substitution that works on paper often fails on lead time.
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
- Elongation is not established here for any product form, and that is the property that decides whether a part can be made.
- Impact toughness and the transition temperature are not established here.
- Whether 444 substitutes for 316L in your service. The pitting ranking numbers are close; the failure modes are not the same.
- Welding procedure guidance and filler selection.
- Composition limits, not established.
Generated from data/materials/444.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.