4145 vs 4142
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.
4145
Alloy & Engineering Steel
4145 is the high-carbon end of the standard Cr-Mo bar family, widely specified in oilfield practice (drill collars, subs) where 4140 hardness is not enough. The modified 4145H chemistry used by the oil industry is a related but distinct supply grade.
Standards: AISI 4145
4142
Alloy & Engineering Steel
4142 is a Cr-Mo steel a touch higher in carbon than 4140, giving slightly higher attainable hardness at the cost of toughness and weldability. Many mills dual-certify 4140/4142 because the windows overlap.
Standards: DIN 1.7225 (42CrMo4, near) · AISI 4142 · JIS SCM440 (near) · GB 42CrMo (near)
Chemical composition compared (%)
| Element | 4145 | 4142 |
|---|---|---|
| C | 0.43–0.48 | 0.40–0.45 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.75–1.00 | 0.75–1.00 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.040 | ≤0.040 |
| Cr | 0.80–1.10 | 0.80–1.10 |
| Mo | 0.15–0.25 | 0.15–0.25 |
Properties compared
| Property | 4145 | 4142 |
|---|---|---|
| Hardness (Q&T) | 32–44 HRC typical | 30–42 HRC typical |
| Tensile strength | 950–1200 MPa (Q&T, typ.) | 900–1150 MPa (Q&T, typ.) |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
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: 4145 · 4142. Substitution decisions for certified parts stay with the design authority.