Key facts
Where to buy| Property | Value | Source |
|---|---|---|
| Composition | Chromium 16.0–18.0 %, nickel 10.0–14.0 %, molybdenum 2.0–3.0 %, carbon up to 0.08 % | ASTM A240/A240M Table 1 (UNS S31600) |
| Specs | AMS 5524 annealed, AMS 5907 ¼ hard | MIL-HDBK-5J, Table 2.7.1.0(b) footnote c |
| Allowables | The 301 table applies for those two conditions only | MIL-HDBK-5J, Table 2.7.1.0(b) footnote c |
| Welding rod | 316L, AWS A5.9 | AC 43.13-1B CHG 1, Table 4-15 |
| Corrosion class | 300 series: much more corrosion resistant than 400 series, particularly in a marine environment | AC 43.13-1B par. 6-164b |
Design allowables — sheet and strip (properties of AISI 301 table, applicable to 316)
0.187 in and under. MIL-HDBK-5J Table 2.7.1.0(b), footnote c.
| Temper | Specification | Ftu L / LT, ksi | Fty L / LT, ksi | Fsu, ksi | Basis |
|---|---|---|---|---|---|
| Annealed | AMS 5524 | 73 / 75 | 26 / 30 | 50 | S |
| ¼ hard | AMS 5907 | 124 / 122 | 69 / 67 | 66 | A |
Properties of the 300-series alloys that the handbook ties to Table 2.7.1.0(b) by footnote. Only annealed and ¼ hard are covered for 316. Table 2.7.1.0(b), p. 2-223.
Thicknesses and forms
Sheet and strip in annealed and ¼ hard, design values to 0.187 in. Other forms exist but the public documents here do not detail them.
Forming
Anneal for forming. Like other austenitic stainless it work-hardens. No public bend radius for stainless; the drawing or SRM governs.
Quick check
Which tempers of 316 does MIL-HDBK-5J cover?
- All five
Not this one. Only two.
- Annealed and ¼ hard
Best fit. Right (footnote c).
- None
Not this one. It is covered by footnote.
On a real job, the SRM decides.
Welding
AISI 300-series austenitic steels are weldable with most processes except 303 and 303Se, which carry sulfur or selenium for machinability. They are slightly harder to weld than mild steel: lower melting temperature and conductivity, but higher expansion, so distortion needs skip or back-step welding, fixtures and twice the tack welds. Clean with a non-chlorinated solvent and a stainless wire brush; shield both sides with inert gas or flux (AMT Handbook, Chapter 5, p. 5-22).
AC 43.13-1B Table 4-15: 316L rod (AWS A5.9) welds 316 stainless.
Corrosion
Austenitic steels get their corrosion resistance from an oxide film that should not be removed even if the surface is discoloured. If the film is broken by abrasion it may not restore itself without repassivation. If corrosion affects the part's structural integrity or serviceability, the part is removed (AC 43.13-1B, par. 6-164b).
Where it is used on aircraft
Parts where the drawing calls 316 for its corrosion behaviour, such as fittings in wet or marine-exposed areas. The drawing names the alloy.
Data sheet
Questions people actually ask
Why molybdenum?
It is the alloying element that sets 316 apart from 304 in the spec composition tables; the benefit is resistance to pitting, the reason it is specified for harsh environments.
Limits — when NOT to use this
- Only two tempers are covered and values are borrowed from 301.
- Not a general upgrade to 304. Use what the drawing says.
Where to buy
Distributors coming soon.
Sources
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (31 Jan 2003) — Table 2.7.1.0(b), footnote c, p. 2-223. Cancelled; superseded by MMPDS.
- FAA AC 43.13-1B CHG 1 — Table 4-15 and par. 6-164.
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook, Airframe, Volume 1 — Chapter 5, p. 5-22.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.
- ASTM A240/A240M, Plate, Sheet, and Strip of Chromium and Chromium-Nickel Stainless Steel — Table 1, chemical requirements (edition 10b read).