- Grade / Alloy
- SAE 4140
- EN / W.Nr.
- —
- AISI / SAE
- 4140
- UNS
- —
- Family
- Alloy steel
Chemical composition
Chemical composition
Composition limitsPublished ASTM A29 composition ranges for AISI 4140; excludes modified 4140 variants.
| Element | Content (% by mass) |
|---|---|
| CCarbon | 0.38–0.43 |
| SiSilicon | 0.15–0.35 |
| MnManganese | 0.75–1 |
| PPhosphorus | ≤ 0.035 |
| SSulfur | ≤ 0.04 |
| CrChromium | 0.8–1.1 |
| MoMolybdenum | 0.15–0.25 |
Values describe the grade, not the analysis of a specific batch. The applicable product specification and material certificate determine acceptance. A dash does not mean zero.
What kind of steel is SAE 4140?
SAE 4140 is a chromium-molybdenum alloy steel widely used in machine parts such as shafts, gears and pins. Its medium-carbon composition suits mechanical applications needing strength and toughness together. It belongs to a different family from stainless steels: load-carrying capability defines its role. This makes it a familiar engineering steel for force-transmitting components across many types of machinery.
Balancing strength and toughness
A shaft or pin carries load while retaining its shape. Forces may change during service, and sudden loads can occur. The strength and toughness of 4140 are useful in these mechanical duties. Available in different strength conditions, the grade has a broad application range, from bar products to large machine components that use these mechanical characteristics.
Machinery and automotive applications
Shafts, axles, gears, studs and connecting pins are familiar examples. Transmitting force between parts is a common duty across automotive and general machinery equipment. Rather than belonging to a single sector, the grade serves the requirements of widely used machine elements. It does not provide stainless corrosion protection, so environmental exposure remains a separate consideration in its use.
Distinct from 42CrMo4 and 4340
42CrMo4 / 1.7225 is a related European alloy steel. Composition limits and specification requirements do not coincide completely, so the grades are not exact equivalents in every case. 4340 adds nickel to chromium and molybdenum and is known for more demanding mechanical applications requiring strength and toughness. Within this family, 4140 has a broad established role in machinery and automotive components.
Typical application areas
Shafts, gears, pins and loaded machinery components.
Product and cutting options
Relevant product forms for this material are listed below. Availability varies with grade and dimensions.