4340 at a glance
Where to buy
Designation
| Item | Value |
|---|---|
| Designation | 4340 |
| Class | Steel and stainless |
| Type | alloy steel |
Composition
| Item | Limit | Source |
|---|---|---|
| Composition | Nickel 1.65–2.00 %, chromium 0.70–0.90 %, molybdenum 0.20–0.30 %, carbon about 0.40 % | AZoM AISI 4340 composition table |
Properties
| Property | Value | Source |
|---|---|---|
| Against 4140 | Heat treated in thicker sections and to higher strength levels | MIL-HDBK-5J, par. 2.3.1.0 |
| Bars, forgings, tubing (consumable electrode melted) | AMS 6414 | MIL-HDBK-5J, Table 2.3.1.0(b) |
| Sheet, strip, plate | AMS 6454 (consumable electrode), AMS 6359 (air melted); neither lists minimum properties | MIL-HDBK-5J, Tables 2.3.1.0(a) and (b) |
| Bars and forgings (air melted) | AMS-S-5000, AMS 6415 | MIL-HDBK-5J, Table 2.3.1.0(a) |
| Strength levels used | Ftu = 260 ksi or higher; not used at 220 ksi | MIL-HDBK-5J, par. 2.3.1.0 |
| Tempering trap | Embrittlement when tempered in the range 500 to 700 °F | MIL-HDBK-5J, par. 2.3.1.0 |
Design allowables — AISI 4340, quenched and tempered
Bars, forgings and tubing, consumable-electrode (vacuum) melted only. MIL-HDBK-5J Table 2.3.1.0(f1).
| Property | S basis | Unit |
|---|---|---|
| Ftu | 260 | ksi |
| Fty | 217 | ksi |
| Fcy | 235 | ksi |
| Fsu | 156 | ksi |
| Elongation, L (S basis) | 10 | % |
| Specification | AMS 6414 | — |
Applicable to consumable-electrode vacuum-melted material only (footnote a), and only to parts for which the Ftu has been substantiated by quality control testing (footnote b). The maximum section depends on the quench; the table's footnotes give it for oil, salt and water. Source: MIL-HDBK-5J (31 Jan 2003), Table 2.3.1.0(f1), p. 2-22. E = 29.0 × 10³ ksi and density 0.283 lb/in³ are printed for the low-alloy steels in Table 2.3.1.0(c1).
Notes from the guide
- Vacuum-melted values only. They do not apply to air-melted material.
- Not a repair stock. Replacement of a 4340 part is by part number, not by a bar from a catalog.
- No welding or hand-sanding advice. Corrosion and cracks go to engineering.
Where to buy
AmericaDistributor coming soonOur partner for this region is on its way
EuropeDistributor coming soonOur partner for this region is on its way
OceaniaDistributor coming soonOur partner for this region is on its way
Distributors coming soon.
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), (b) and (f1) p. 2-22. 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.
- AZoM, AISI 4340 alloy steel — Chemical composition table (carbon given as 0.37-0.43; page says about 0.40).
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.