When a customer says “I want 410, but weldable”, the answer is AISI 415. Both steels are martensitic and both are around 13 % chromium; the difference is 415’s very low carbon and its added nickel and molybdenum.
Why does carbon matter so much?
In martensitic steels, carbon is the root of the welding problem. The hard martensite that forms in the weld zone becomes more brittle as carbon rises, and the risk of cracking increases. AISI 410’s carbon is 0.08–0.15 %; AISI 415’s (1.4313) is 0.05 % maximum.
The British Stainless Steel Association puts it directly: low-carbon martensitic grades such as 1.4313 are more weldable than the other martensitics because the reduced carbon lowers the pre- and post-weld heat treatment requirement. But “more weldable” does not mean “no preheat needed” — 415 still requires preheat and post-weld tempering. It does not behave like an austenitic steel.
Nickel and molybdenum
Lowering the carbon costs strength; 415 wins it back with 3.5 to 4.5 % nickel. On top of that it adds 0.30 to 0.70 % molybdenum, which AISI 410 does not have at all. The result is a steel with higher proof strength than 410, far greater toughness and better corrosion behaviour.
415 is normally supplied double tempered — a practice not seen in the other members of the family, and the source of its toughness.
Compared in figures
Composition figures are EN 10088-3 cast analysis limits.
| PROPERTY | AISI 415 (1.4313) | AISI 410 (1.4006) |
|---|---|---|
| Carbon (C) | 0.05 % max | 0.08 – 0.15 % |
| Silicon (Si) | 0.70 % max | 1.00 % max |
| Manganese (Mn) | 1.50 % max | 1.50 % max (EN) |
| Phosphorus (P) | 0.040 % max | 0.040 % max |
| Sulphur (S) | 0.015 % max | — |
| Chromium (Cr) | 12.00 – 14.00 % | 11.50 – 13.50 % |
| Nickel (Ni) | 3.50 – 4.50 % | 0.75 % max |
| Molybdenum (Mo) | 0.30 – 0.70 % | not specified |
| Nitrogen (N) | ≥ 0.020 % | — |
| Proof strength (Rp0.2) | ≥ 520 MPa (+QT650/700) | ≥ 450 MPa (+QT650) |
| Tensile strength (Rm) | 700–800 / 700–850 MPa | 650 – 850 MPa |
| Elongation | ≥ 15 % | ≥ 15 % |
| Tempering | double temper | single temper |
Note on tensile strength: for 1.4313, CEN (EN 10088-3, +QT700) and METALCOR give 700–800 MPa; Swiss Steel Group (Acidur 4313, +QT650) and Virgamet give 700–850 MPa. We publish both and do not average them.
What to watch when ordering
EN 1.4313 and UNS S41500 are not the same specification.
Nickel is 3.5–4.5 % in EN against 3.5–5.5 % in ASTM; molybdenum 0.30–0.70 % against 0.50–1.00 %; sulphur 0.015 % max against 0.030 % max. A heat can meet one and fail the other — in either direction. Dual certification is not automatic.
“AISI 415” is a commercial convenience name, not a classic AISI type. Every primary source works from S41500, 1.4313 or ASTM A182 F6NM. Put the material number on the order.
CA6NM (J91540) is the casting grade. A CA6NM certificate should not be accepted against an order for wrought 1.4313.
The sour-service (NACE) specification is a different product. In the NACE MR0175 / ISO 15156 version of F6NM, hardness is capped at 23 HRC and the strength minima are lower. Two different “415”s circulate; state which one you want.
Where is it used?
Hydroelectric turbine runners and components, pumps, compressors, valves, turbine rotors, oil and petrochemical equipment, shipbuilding. What these have in common is large sections, welded construction and dynamic loading — the places where 410’s toughness is not enough.
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 415 | AISI 410 |
|---|---|---|
| AISI / trade name | AISI 415 | AISI 410 |
| EN material no. (W.Nr) | 1.4313 | 1.4006 |
| UNS number | S41500 | S41000 |
| AMS specifications | — | AMS 5504 · AMS 5505 |
| Product page | AISI 415 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.