Data completeness: partial. Last verified 19 August 2026.
Designations
| Common name | 441 |
| UNS | S43932 |
| EN number | 1.4509 |
| Class | Ferritic stainless steel |
| Specified by | EN 10088-2 |
441 is a ferritic stainless with no nickel in it, dual-stabilised with niobium and titanium. Two consequences follow from the crystal structure and they are the whole story. It is not susceptible to chloride stress corrosion cracking, which austenitics are. And it conducts heat roughly two thirds better than 304 while expanding about a third less, which is why it ends up in exhaust systems and heat exchangers rather than in vessels.
Properties, with what each one rests on
| Property | Value | Unit | Condition | Evidence | Source | Retrieved |
|---|---|---|---|---|---|---|
| Proof strength Rp0.2, minimum (EN) | 250 | MPa | cold rolled coil and sheet, 20 °C; test orientation not stated by this source | E3 | EN 10088-2 via Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Proof strength Rp0.2, longitudinal | 230 | MPa | cold rolled, thickness up to 8 mm, annealed, longitudinal | E3 | EN 10088-2 via thyssenkrupp Materials (UK) — stainless steel 441 / 1.4509 data | 2026-08-20 |
| Tensile strength Rm, minimum | 430 | MPa | cold rolled; datasheet gives a 430–630 range | E3 | EN 10088-2 via Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Elongation A, minimum | 18 | % | cold rolled; A and A80 both 18 | E3 | EN 10088-2 via Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| PREN | 18 | — | from typical composition, not from a heat | E3 | Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Density | 7.7 | g/cm³ | 20 °C | E3 | Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Modulus of elasticity | 220 | GPa | 20 °C | E3 | Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Thermal conductivity | 25 | W/(m·K) | 20 °C | E3 | Outokumpu Core range datasheet — standard austenitic and ferritic stainless steels | 2026-08-20 |
| Impact toughness and the ductile-to-brittle transition temperature | not established | — | — | — | not in the datasheet consulted; for a ferritic this is the property that decides thickness and minimum service temperature | — |
| Composition limits | not established | — | — | — | the datasheet gives typical values, which are not limits, and the standard is paywalled | — |
| ASTM designation and minima | not established | — | — | — | no ASTM source was checked for this grade | — |
| Test orientation for the 250 MPa figure | not established | — | — | — | the datasheet that prints it does not state one, and the second source shows the number depends on it | — |
8 sourced values, 4 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). Higher than the 304 row in the same table, which is the opposite of what most people expect from a ferritic. It buys that at the cost of elongation: 18% against 45%. The figure was queried on 20 August 2026 because it looked high for this grade, and the answer is in the row below: an independent distributor datasheet quoting the same standard and the same product form gives 230 MPa longitudinal and 250 MPa transverse. Neither document says which orientation the 250 belongs to, but on that evidence it is the transverse figure. That is an inference and is not stated anywhere, which is why it lives in a note rather than in the condition column.
Proof strength Rp0.2, longitudinal. The same grade, the same product form and the same standard as the row above, 20 MPa lower, because the test piece was cut the other way. Rolled ferritic sheet has a crystallographic texture and its proof strength is directional; austenitics are far less so, which is why this problem does not appear on the other grade pages here. A 1.4509 figure quoted without its orientation carries an 8% ambiguity, and neither source states the orientation of the higher number.
PREN. 18% Cr, no molybdenum, no nitrogen gives 18 in the datasheet’s own formula. Level with 304 on the ranking number — which is a good demonstration of what PREN does not tell you, because the two grades fail in completely different ways.
Thermal conductivity. Two thirds higher than any austenitic in the same datasheet, which is the property that puts ferritics into heat exchangers.
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 441 is usually chosen for
Heat exchange, exhaust and appliance work where the environment is mild but thermal behaviour matters. High conductivity, low expansion, no nickel in the price, and immunity to the chloride stress corrosion cracking that catches austenitics. In flat product at moderate thickness it is often a straight substitution for 304 at a lower and much less volatile cost.
And what it is usually rejected for
Thickness, toughness and welding. Ferritics have a ductile-to-brittle transition and it moves up with section thickness, so heavy plate is not the place for them. Weld zones coarsen and lose toughness, which limits practical welded construction. And elongation at 18% is less than half what an austenitic gives, so deep drawing and severe forming go elsewhere.
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
What this page does not cover
- Impact toughness and the transition temperature are not established here, and for a ferritic they govern the safe thickness and the minimum service temperature.
- Elevated temperature strength and creep.
- Welding procedure guidance, which matters more for ferritics than for austenitics.
- Composition limits, not established.
- No ASTM designation or minima on this page.
- Which orientation the higher proof strength figure belongs to. Two sources, one number each way, neither says.
Generated from data/materials/441.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.