AISI 405 and AISI 410 are two 13 % chromium steels with very similar chromium contents. But one hardens and the other does not — and the reason is aluminium.
What does the aluminium do?
AISI 405 contains 0.10 to 0.30 % aluminium. Aluminium is a strong ferrite former: it suppresses the formation of austenite at temperature. With no austenite, there is no phase to transform to martensite on cooling. The result: AISI 405 cannot be hardened by quenching.
This is confirmed from several independent directions. Penn Stainless states that 405 resists hardening, unlike other 12 % chromium grades. The Specialty Steel Industry of North America places S40500 in its ferritic table, not the martensitic table where 410 sits. ASTM A479 defines only an annealed condition for S40500 — the T, H, 2 and 3 hardened conditions that exist for 410 do not exist for 405.
410 does harden
AISI 410 is a classic martensitic stainless. It is quenched from roughly 950–1010 °C and tempered, and that is where its strength comes from. In the +QT650 condition to EN 10088-3 its proof strength is at least 450 MPa and its tensile strength 650–850 MPa.
The price is paid in welding: 410 can be welded, but it requires preheat and post-weld heat treatment. That is exactly why 405 exists — it answers the need for a 13 % chromium steel that can be used without post-weld annealing.
Compared in figures
| PROPERTY | AISI 405 | AISI 410 |
|---|---|---|
| Structure | ferritic | martensitic |
| Carbon (C) | 0.08 % max | 0.08 – 0.15 % |
| Silicon (Si) | 1.00 % max | 1.00 % max |
| Manganese (Mn) | 1.00 % max | 1.00 % max (ASTM) / 1.50 % max (EN) |
| Phosphorus (P) | 0.040 % max | 0.040 % max |
| Aluminium (Al) | 0.10 – 0.30 % | not specified |
| Chromium (Cr) | 11.50 – 14.50 % (ASTM) | 11.50 – 13.50 % |
| Nickel (Ni) | 0.50 – 0.60 % max | 0.75 % max |
| Molybdenum (Mo) | not specified | not specified |
| Hardens on quenching | no | yes |
| Proof strength (Rp0.2) | ≥ 170 MPa (annealed plate) | ≥ 450 MPa (+QT650) |
| Tensile strength (Rm) | ≥ 415 MPa (annealed plate) | 650 – 850 MPa (+QT650) |
| Elongation | ≥ 20 % | ≥ 15 % |
The mechanical properties of AISI 405
Because 405 does not harden, there is only one supply condition: annealed. But the values differ by product form, and the difference is large enough to matter contractually — the proof strength minimum for tube is higher than for plate. Sources that publish a single “405 mechanical properties” table are therefore misleading.
| PROPERTY | Plate / sheet (ASTM A240) | Tube (ASTM A268 TP405) | Bar (ASTM A479) |
|---|---|---|---|
| Tensile strength (Rm), min | 415 MPa (60 ksi) | 415 MPa (60 ksi) | 415 MPa (60 ksi) |
| Proof strength (Rp0.2), min | 170 MPa (25 ksi) | 205 MPa (30 ksi) | 170 MPa (25 ksi) |
| Elongation (50 mm), min | 20 % | 20 % | 20 % |
| Reduction of area, min | — | — | 45 % |
| Hardness, max | 179 HBW / 88 HRB | 207 HB / 95 HRB | 207 HBW |
The bar column (ASTM A479) is taken from the text of the standard alone; no independent producer datasheet repeating it could be found. The other two columns are each confirmed by four independent organisations.
The European side: 1.4002
In EN 10088-2 the minima for 1.4002 also differ by product type. (Source: Guanyu Tube’s reproduction of EN 10088-2; Rm and elongation are also confirmed by Aalco.)
| PRODUCT TYPE (EN 10088-2) | Rp0.2 min | Rp1.0 min | Rm | A min |
|---|---|---|---|---|
| Cold rolled strip (≤ 8 mm) | 230 MPa | 250 MPa | 400 – 600 MPa | 17 % |
| Hot rolled strip (≤ 13.5 mm) | 210 MPa | 230 MPa | 400 – 600 MPa | 17 % |
| Hot rolled plate (≤ 25 mm) | 210 MPa | 230 MPa | 400 – 600 MPa | 17 % |
You cannot ask for an EN 10088-3 certificate for 1.4002 bar.
X6CrAl13 / 1.4002 is not within the scope of EN 10088-3 (long products) — it appears in neither the composition nor the mechanical property table. Bar must be ordered through ASTM A479 or A276. (Verified by scanning CEN’s EN 10088-3 text and Guanyu Tube’s grade list.)
Mind the gauge length: ASTM’s 20 % is measured over 50 mm, EN’s 17 % over 5.65√S₀. The two figures cannot be compared directly.
Annealing: the practice most sources agree on is 649–760 °C, air cooled. Some publish ranges reaching 800–870 °C (SteelPRO 700–800 °C, Artizono 800–850 °C, Lord Fin Tube 817–871 °C). It is worth saying that this is industry practice rather than a standard requirement: ASTM A240, A276 and A479 give no annealing temperature for 405.
Service temperature: approximately 704 °C in continuous service and 816 °C in intermittent exposure (Guanyu Tube, Fushun Steel Tube and Lord Fin Tube; SteelPRO gives 705 °C).
How to read this table. Rows without a source name have been confirmed by at least four independent organisations. Rows with an organisation named in brackets were found in fewer sources and are therefore given with attribution. No figure we could not verify has been published.
405 is not “soft 410”.
The non-hardening member of the martensitic family is 410S (UNS S41008 / EN 1.4000), and it achieves that through low carbon. AISI 405 achieves it through aluminium. They are different materials and must not be ordered interchangeably.
ASTM S40500 and EN 1.4002 are not identical either. In CEN’s own table 1.4002 has a chromium range of 12.0–14.0 % and a sulphur ceiling of 0.015 %; S40500 has chromium 11.5–14.5 % and sulphur 0.030 %. A heat at 11.8 % chromium meets S40500 and fails 1.4002.
Which one is right for your job?
If you need strength, 410. Valve parts, pump shafts, fasteners and turbine blades fall into this class; in the hardened and well-polished condition its corrosion resistance is also at its best.
If you need welded fabrication and strength is not a requirement, 405. It was made for tube sheets, heat exchanger fabrications, annealing boxes and similar work that cannot be annealed after welding.
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 405 | AISI 410 |
|---|---|---|
| AISI / trade name | AISI 405 | AISI 410 |
| EN material no. (W.Nr) | 1.4002 | 1.4006 |
| UNS number | S40500 | S41000 |
| AMS specifications | — | AMS 5504 · AMS 5505 |
| Product page | AISI 405 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.