AISI 416 is the free-machining version of AISI 410, with sulphur added. The chromium bands are nearly the same and both harden on quenching. The one deliberate difference is sulphur — and it changes three things at once: machinability, welding and corrosion resistance.
Sulphur is a MINIMUM
In AISI 416 sulphur runs from 0.15 to 0.35 %, and that is a minimum. In AISI 410 sulphur is an impurity with a ceiling of 0.030 % max. The difference is more than fivefold. The most common mistake in the field is to read that range as a ceiling: a certificate showing 0.02 % sulphur is not 416.
The sulphur combines with manganese to form manganese sulphide inclusions, and those inclusions break the chip. The result makes AISI 416 the easiest to machine of all stainless steels. Machinability is around 85 % or better of a free-machining carbon steel (Aalco, Righton Blackburns and United Performance Metals say 85 %; BSSA gives 0.95 on its own index). We do not publish a single ratio — the organisations use different reference bases. What is certain is the ordering: 416 machines markedly more easily than 410.
The price is paid in two places
Welding. BSSA, Aalco, Righton Blackburns, Thames Stockholders and Outokumpu — five separate organisations — rate 416’s weldability as poor and do not recommend it for welded fabrication, because sulphur promotes hot cracking. AISI 410, by contrast, is welded routinely with preheat and post-weld heat treatment. 416 should not be substituted into a welded assembly designed for 410.
Corrosion. The same sulphide inclusions act as pit initiation sites. 416’s corrosion resistance is lower than 410’s, and it is unsuitable for seawater or chloride environments.
Compared in figures
Composition to EN 10088-3; mechanical values for bar in the +QT650 condition.
| PROPERTY | AISI 416 (1.4005) | AISI 410 (1.4006) |
|---|---|---|
| Carbon (C) | 0.06 – 0.15 % | 0.08 – 0.15 % |
| Silicon (Si) | 1.00 % max | 1.00 % max |
| Manganese (Mn) | 1.50 % max | 1.50 % max |
| Phosphorus (P) | 0.040 % max | 0.040 % max |
| Sulphur (S) | 0.15 – 0.35 % (minimum) | 0.030 % max |
| Chromium (Cr) | 12.00 – 14.00 % | 11.50 – 13.50 % |
| Molybdenum (Mo) | 0.60 % max | not specified |
| Proof strength (Rp0.2) | ≥ 450 MPa | ≥ 450 MPa |
| Tensile strength (Rm) | 650 – 850 MPa | 650 – 850 MPa |
| Elongation | ≥ 12 % | ≥ 15 % |
| Hardens on quenching | yes | yes |
| Machinability | best of the stainless steels | limited |
| Weldability | poor — not recommended | suitable with preheat + PWHT |
| Corrosion resistance | lower than 410 | moderate |
What to watch when ordering
Four points
1. The elongation difference is contractual: 12 % for 416 against 15 % for 410 in +QT650. If a drawing calls for 15 % minimum elongation, 416 does not meet it.
2. In ASTM A582 the phosphorus ceiling for 416 is 0.060 % max; in EN 1.4005 it is 0.040 % max. A bar at 0.05 % phosphorus passes ASTM and fails EN.
3. Carbon differs too: EN 1.4005 sets a 0.06 % minimum, while ASTM A582/A276 give only a 0.15 % maximum with no minimum.
4. Do not confuse 416 with 416Se (S41623), 416 Plus X or 416LH; these are separate products with different chemistry and behaviour.
Where is it used?
Valve parts, pump and motor shafts, automatic screw machine parts, gears, bolts, nuts and studs, precision machined components, automotive injector and solenoid valve parts. What they have in common is high volume, a dry or mildly corrosive environment, and no 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 416 | AISI 410 |
|---|---|---|
| AISI / trade name | AISI 416 | AISI 410 |
| EN material no. (W.Nr) | 1.4005 | 1.4006 |
| UNS number | S41600 | S41000 |
| AMS specifications | AMS 5610 | AMS 5504 · AMS 5505 |
| Product page | AISI 416 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.