4140 vs SCM440
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
4140
Alloy & Engineering Steel
4140 is the most popular Cr-Mo engineering steel in the world: a through-hardening grade for shafts, gears, bolts and hydraulic parts that need strength with machinability. Supplied annealed, normalized or prehardened as round bar.
Standards: DIN 1.7225 (42CrMo4) · AISI 4140 · JIS SCM440 · GB 42CrMo
SCM440
Alloy & Engineering Steel
SCM440 is the JIS Cr-Mo steel matching 4140/42CrMo4 — the designation on Japanese, Korean and Taiwanese certificates for the same class of machinery steel.
Standards: DIN 1.7225 (42CrMo4) · AISI 4140 · JIS SCM440 · GB 42CrMo
Chemical composition compared (%)
| Element | 4140 | SCM440 |
|---|---|---|
| C | 0.38–0.43 | 0.38–0.43 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.75–1.00 | 0.60–0.90 |
| P | ≤0.035 | — |
| S | ≤0.040 | — |
| Cr | 0.80–1.10 | 0.90–1.20 |
| Mo | 0.15–0.25 | 0.15–0.30 |
Properties compared
| Property | 4140 | SCM440 |
|---|---|---|
| Hardness (Q&T) | 28–40 HRC typical | 28–38 HRC typical |
| Tensile strength | 850–1100 MPa (Q&T) | ≥980 MPa (Q&T reference) |
| Yield strength | ≥650 MPa (Q&T, section dependent) | — |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Elastic modulus | 210 GPa | — |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: 4140 · SCM440. Substitution decisions for certified parts stay with the design authority.