4130 at a glance
Where to buy
Designation
| Item | Value |
|---|---|
| Designation | 4130 |
| Class | Steel and stainless |
| Type | chromium-molybdenum steel |
Composition
| Item | Limit | Source |
|---|---|---|
| Composition | Chromium 0.80–1.10 %, molybdenum 0.15–0.25 %, carbon 0.28–0.33 % | AC 43.13-1B CHG 1, Chapter 4, Section 1, designation of “4130”; Table 4-2 |
Properties
| Property | Value | Source |
|---|---|---|
| Interchangeable tubing | Welded to MIL-T-6731 and seamless to MIL-T-6736 | AC 43.13-1B CHG 1, par. 4-3a |
| Sheet, strip and plate specification | AMS 6345, normalized or otherwise heat treated | SAE AMS6345 (title) |
| Normalizing | Heat to about 150–225 °F above the critical range, cool in still air; soak about ¼ hour per inch of thickness | AC 43.13-1B CHG 1, par. 4-1c |
| TIG welding, wall under 0.120 in | Preheat not necessary; post-weld stress relief still recommended | FAA-H-8083-31, Chapter 5, TIG Welding 4130 Steel Tubing |
Table 4-6 (bend radii) covers aluminum only, so there is no bend radius for 4130 on this page. The drawing or SRM gives it.
Design allowables — AISI 4130 sheet, strip, plate and tubing
0.188 in and under, normalized and tempered, stress relieved. MIL-HDBK-5J Table 2.3.1.0(c1). S basis in ksi unless a unit is shown.
| Property | S basis | Unit |
|---|---|---|
| Ftu | 95 | ksi |
| Fty | 75 | ksi |
| Fcy | 75 | ksi |
| Fsu | 57 | ksi |
| Fbru, e/D = 1.5 | — | ksi |
| Fbru, e/D = 2.0 | 200 | ksi |
| Fbry, e/D = 1.5 | — | ksi |
| Fbry, e/D = 2.0 | 129 | ksi |
| Elongation, sheet, strip and plate, under 0.062 in (minimum) | 8 | % |
| Property | S basis | Unit |
|---|---|---|
| Elongation, sheet, strip and plate, over 0.062 to 0.125 in (minimum) | 10 | % |
| Elongation, sheet, strip and plate, over 0.125 to 0.187 in (minimum) | 12 | % |
| Elongation, tubing (L), full tube, wall up to 0.035 in (minimum) | 10 | % |
| Elongation, tubing (L), full tube, wall over 0.035 to 0.188 in (minimum) | 12 | % |
| E | 29.0 | 10³ ksi |
| Ec | 29.0 | 10³ ksi |
| G | 11.0 | 10³ ksi |
| Density | 0.283 | lb/in³ |
Form: sheet, strip, plate and tubing; condition: normalized and tempered, stress relieved; specification: AMS 6360, AMS 6373, AMS 6374, AMS-T-6736 and AMS-S-18729; thickness or diameter 0.188 in and under. The handbook gives S basis only for 4130, with no A or B values and no L or LT direction, so there is no B column. Design values apply only to parts for which the Ftu has been substantiated by adequate quality control testing (handbook footnote b). Elongation is from Table 2.3.1.0(d), p. 2-21 (condition N). Source: MIL-HDBK-5J (31 Jan 2003), Table 2.3.1.0(c1), p. 2-17. MIL-HDBK-5J (2003) is superseded by MMPDS; check current MMPDS before design use. Density 0.283 lb/in³ is about 7.83 g/cm³ (converted); the sheet weight calculator uses the same figure.
Heat treatment and conditions
| Condition | Design strength | Source |
|---|---|---|
| Normalized and tempered, stress relieved (sheet, tube) | Ftu 95 / Fty 75 ksi up to 0.188 in | MIL-HDBK-5J, Table 2.3.1.0(c1) |
| Quenched and tempered tube, low level | Ftu 125 / Fty 100 ksi | MIL-HDBK-5J, Table 2.3.1.0(c2) |
| Quenched and tempered tube, middle level | Ftu 150 / Fty 135 ksi | MIL-HDBK-5J, Table 2.3.1.0(c2) |
| Quenched and tempered tube, high level | Ftu 180 / Fty 165 ksi, all walls | MIL-HDBK-5J, Table 2.3.1.0(c2) |
Forms and thicknesses in stock
| Distributor sheet | Listed | Thickness, in |
|---|---|---|
| 4130 Steel Sheets | MIL-S-6345A · 0.025"–0.250" | .025, .032, .040, .050, .063, .071, .080, .090, .100, .125, .190, .250 |
| 4130 Steel Sheet | 0.025"–0.250" · sheared sizes | .025, .032, .040, .050, .063, .071, .080, .090, .100, .125, .190, .250 |
| 4130 Alloy Steel Round Seamless | 3/16"–2-3/4" OD · 1–24 ft | .028, .035, .049, .058, .065, .083, .095, .120, .125, .156, .188, .250 |
| 4130 Airframe Square & Rectangular Tubing MIL-T-6736 Normalized | MIL-T-6736 · 14 sizes · lb/ft | .035, .049, .065 |
| 4130 Streamline Tubing | 13 sizes · round equivalents | .035, .049, .065 |
As distributors list them, not a statement of what a specification allows.
Notes from the guide
- Not a source of design allowables. The strength depends on heat treatment and form. Use MMPDS with the basis; the SRM governs a repair.
- Not a substitute for an aluminum tube or the reverse. Different weight, stiffness and corrosion behaviour. Material substitution in a structural repair is approved-data territory.
- Weld repair of tube structure is a procedure, not a tip. The AC and the SRM define acceptable repairs (AC 43.13-1B, Chapter 4).
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Sources
- FAA AC 43.13-1B CHG 1, Chapter 4 — Section 1, pars. 4-1 to 4-3, Table 4-2; par. 4-89 — composition, steel numbering, tubing interchangeability, normalizing, and parts not to be welded.
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 5 (Steel including SAE 4130, p. 5-16; TIG welding 4130 steel tubing) — use, designation and TIG welding practice.
- SAE AMS6345, Steel, Sheet, Strip, and Plate 0.95Cr-0.20Mo (0.28-0.33C) (SAE 4130), Normalized or Otherwise Heat Treated — title of the governing sheet, strip and plate specification.
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures — density (Table 2.3.1.0(c1)), and the home of the 4130 design allowables (Chapter 2, steels). Cancelled; replaced by MMPDS.
- MIL-HDBK-5J (31 Jan 2003), Table 2.3.1.0(c1), p. 2-17 — AISI 4130 sheet, strip, plate and tubing, normalized and tempered, stress relieved, 0.188 in and under: S-basis allowables, E, Ec, G and density.
- MIL-HDBK-5J (31 Jan 2003), Table 2.3.1.0(d), p. 2-21 — minimum elongation values for low-alloy steels in condition N.
- FAA AC 43.13-1B CHG 1 — Table 4-15, par. 6-164 to 6-167.
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (31 Jan 2003) — Tables 2.3.1.0(a), (c1) and (c2), pp. 2-16 to 2-18. Cancelled; superseded by MMPDS.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables with A, B and S basis. Cancelled MIL-HDBK-5J was superseded by it. A repair substantiation cites MMPDS or the SRM, not a website.
- Distributor listings — stock forms, sizes and listed facts, read 30 September 2026.
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.