AISI 431 and AISI 410 are both martensitic stainless steels and both harden on quenching. The difference is 431’s markedly higher chromium and its added nickel — which makes it the most corrosion-resistant member of the conventional martensitic family.
The chromium and nickel difference
AISI 410’s chromium runs from 11.50 to 13.50 % and nickel is an impurity (0.75 % max). In AISI 431 chromium rises to 15.00–17.00 % and nickel enters the specification. The result is a martensitic steel that can stand up to marine atmospheres.
Carpenter Technology, BGH Edelstahlwerke, Deutsche Edelstahlwerke and Universal Stainless — four separate organisations — describe 431 as the most corrosion-resistant of the hardenable 400-series grades and suitable for marine atmospheric service.
Compared in figures
| PROPERTY | AISI 431 (1.4057) | AISI 410 (1.4006) |
|---|---|---|
| Chromium (Cr) | 15.00 – 17.00 % | 11.50 – 13.50 % |
| Silicon (Si) | 1.00 % max | 1.00 % max |
| Phosphorus (P) | 0.040 % max | 0.040 % max |
| Sulphur (S) | 0.030 % max | 0.030 % max |
| Nickel (Ni) | see note below | 0.75 % max |
| Carbon (C) | see note below | 0.08 – 0.15 % |
| Proof strength (Rp0.2), +QT800 | ≥ 600 MPa | — |
| Proof strength (Rp0.2), +QT900 | ≥ 700 MPa | — |
| Proof strength (Rp0.2), +QT650 | — | ≥ 450 MPa |
| Tensile strength (Rm), +QT650 | — | 650 – 850 MPa |
| Annealed hardness | ≤ 295 HBW | — |
| Hardening temperature | 950 – 1060 °C, oil | 950 – 1010 °C |
| Sub-critical anneal | 680 – 800 °C | — |
Note on nickel: ASTM A276 and Carpenter give 1.25–2.50 %; BGH, Deutsche Edelstahlwerke and Rodacciai give 1.50–2.50 %. Note on carbon: ASTM A276, Carpenter and BGH give 0.20 % max with no minimum, while Deutsche Edelstahlwerke and Rodacciai give 0.12–0.22 % for EN 10088-3. We do not reduce these two rows to a single value — the sources genuinely diverge.
What to watch when ordering — two serious traps
An order for “431 to ASTM A276” carries no strength guarantee.
ASTM A276 tabulates no tensile requirement for Type 431 in Condition T or H; it gives only a hardness limit for Condition A. An order reading “431 to A276” is therefore empty as far as strength is concerned. Specify the strength you need separately, or order to an aerospace specification.
ASTM 431 and EN 1.4057 are not the same chemistry.
ASTM sets no carbon minimum; EN sets one at 0.12 %. A bar at 0.05 % carbon may meet ASTM 431 but will not meet 1.4057. The nickel minimum also differs. If both specifications must be met, write carbon 0.12–0.20 % and nickel 1.50–2.50 % into the contract.
The tempering range to avoid
In both steels a particular tempering range reduces toughness and corrosion resistance. Carpenter points to 371–565 °C for 431 and 399–566 °C for 410. Deutsche Edelstahlwerke adds that 1.4057 is susceptible to 475 °C embrittlement and that 420–520 °C should be avoided.
On welding the sources diverge: Carpenter requires 204–316 °C preheat and 649 °C post-weld heat treatment for 431, while Deutsche Edelstahlwerke rates 1.4057’s weldability as “good”. We do not issue a single verdict; if you are planning welded fabrication, agree the procedure with your material supplier.
Where are they used?
AISI 431: aircraft fasteners and fittings, pump shafts, valve stems, piston rods, structural parts working in marine environments.
AISI 410: turbine blades, valves, pumps, gate valves, fasteners, refinery internals, cutlery.
In short: both offer strength; when the environment is corrosive you step up to 431.
Designations, standards and AMS equivalents
The same steel is called different things depending on which system you are speaking in. Most ordering and certification confusion starts here, so a short summary:
- AISI — the American Iron and Steel Institute’s grade naming (410, 316L and so on). It is the most widely used name in everyday use, but on its own it is not a purchasing specification: composition and mechanical requirements are defined in the ASTM standards.
- UNS — the Unified Numbering System operated jointly by ASTM and SAE (S41000 and so on). It is the number used for ordering and certification in North America, and it is more precise than the AISI name.
- W.Nr / EN — the European material number (1.4006 and so on) and EN name (X12Cr13 and so on). This is the governing designation in Europe. It is usually only an approximate equivalent of the AISI grade; carbon, sulphur or molybdenum limits frequently differ.
- AMS — SAE’s Aerospace Material Specifications. An AMS specification binds not only the composition but also the melting practice, the product form, the heat treatment condition and the inspection requirements. In aerospace and defence orders this is the designation that governs.
| DESIGNATION | AISI 431 | AISI 410 |
|---|---|---|
| AISI / trade name | AISI 431 | AISI 410 |
| EN material no. (W.Nr) | 1.4057 | 1.4006 |
| UNS number | S43100 | S41000 |
| AMS specifications | AMS 5628 | AMS 5504 · AMS 5505 |
| Product page | AISI 431 technical page | AISI 410 technical page |
Two reminders. First: an AMS number is specific to a product form and condition. The same grade may have separate AMS specifications for bar, sheet and forgings, so establish which product form you need before calling up an AMS number.
Second: the AISI name, material number, UNS and AMS data in the table above are the designations shown on Defence Metal’s product pages. If you are working to a different edition of a standard or to a different product form, state the material number and the specification edition explicitly on your order.