8740 at a glance
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Designation
| Item | Value |
|---|---|
| Designation | 8740 |
| Class | Steel and stainless |
| Type | alloy steel |
Composition
| Item | Limit | Source |
|---|---|---|
| Composition | Nickel 0.40–0.70 %, chromium 0.40–0.60 %, molybdenum 0.20–0.30 %, carbon about 0.40 % | Metal supplier's AISI 8740 datasheet |
Properties
| Property | Value | Source |
|---|---|---|
| Role | AISI 8630, 8735 and 8740 are the alternates to 4130, 4135 and 4140 | MIL-HDBK-5J, par. 2.3.1.0 |
| Sheet, strip, plate | AMS 6358 | MIL-HDBK-5J, Table 2.3.1.0(a) |
| Bars and forgings | AMS-S-6049 (noncurrent), AMS 6327, AMS 6322 | MIL-HDBK-5J, Table 2.3.1.0(a), (c3) |
| Tubing | AMS 6323 | MIL-HDBK-5J, Table 2.3.1.0(a) |
| Condition for design values | Quenched and tempered | MIL-HDBK-5J, Table 2.3.1.0(c3) |
Design values — AISI 8740 bars and forgings, quenched and tempered
Bars and forgings. MIL-HDBK-5J Table 2.3.1.0(c3).
| Property | S basis | Unit |
|---|---|---|
| Ftu | 125 | ksi |
| Fsu | 75 | ksi |
| E | 29.0 | 10³ ksi |
| G | 11.0 | 10³ ksi |
| Density | 0.283 | lb/in³ |
Only Ftu and Fsu are listed here: the table prints one block for 8630 and 8740 with several specifications and thicknesses (1.500 and 1.750 in appear), and the 8740 yield and bearing columns cannot be separated reliably from the printed layout. Read Table 2.3.1.0(c3), p. 2-19, for them. Design values apply only to parts whose Ftu has been substantiated by quality control testing (footnote b).
Notes from the guide
- Partial table only. Yield and bearing values are not reproduced here; open Table 2.3.1.0(c3).
- No welding or bend data in the public documents.
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Sources
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (31 Jan 2003) — par. 2.3.1.0; Tables 2.3.1.0(a) and (c3), p. 2-19. Cancelled; superseded by MMPDS.
- FAA AC 43.13-1B CHG 1 — par. 4-89c and par. 6-165.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.
- Metal supplier's AISI 8740 datasheet — Chemical composition table.
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.