Key facts
Where to buy| Property | Value | Source |
|---|---|---|
| Composition | Carbon 0.08 %, chromium 18 %, nickel 11 %, columbium or tantalum | AC 43.13-1B CHG 1, Table 4-3 |
| Class | Austenitic | AC 43.13-1B CHG 1, Table 4-3 |
| Sheet, strip, plate | AMS 5512 | SAE AMS 5512 (title) |
| As filler | AISI 347 is among the filler metals for welding austenitic stainless | AMT Handbook, p. 5-22 |
| Allowables | Not in MIL-HDBK-5J (checked) | MIL-HDBK-5J |
Thicknesses and forms
Sheet, strip and plate (AMS 5512), plus tube and bar to their specs. The public documents give no thickness range.
Forming
Anneal for forming; no public stainless bend radius, the drawing or SRM governs.
Quick check
Which element stabilizes 347?
- Titanium
Not this one. That is 321.
- Columbium (niobium) or tantalum
Best fit. Right (AC Table 4-3).
- Copper
Not this one. That is in 17-4PH.
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).
Filler for austenitic stainless includes AISI 309, 310, 316, 317 and 347, chosen from the base metal composition; follow the manufacturer's recommendation (AMT Handbook p. 5-22).
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
Hot-section sheet and tube, such as exhaust and heat-exchanger parts, where austenitic strength and corrosion resistance at temperature matter (AMT Handbook, Chapter 5).
Data sheet
Questions people actually ask
321 or 347?
Both are stabilized austenitic grades. 321 uses titanium, 347 columbium or tantalum (AC Table 4-3). The drawing or SRM names which one.
Limits — when NOT to use this
- No allowables here.
- The drawing's alloy only.
Where to buy
Distributors coming soon.
Sources
- FAA AC 43.13-1B CHG 1 — Table 4-3, par. 6-164.
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook, Airframe, Volume 1 — Chapter 5, TIG welding stainless steel, p. 5-22.
- SAE AMS 5512 — title of the sheet, strip and plate specification.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.