Y30 vs Y40Mn
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.
Y30
Carbon Steel
Y30 is the 0.30% carbon member of the GB/T 8731 free-cutting family: sulfur (0.15–0.25%) keeps it fast on the lathe while the medium-carbon base allows real heat treatment, bridging free-cutting bar and plain machinery steel.
Standards: GB Y30 (GB/T 8731)
Y40Mn
Carbon Steel
Y40Mn is the top-strength grade of China’s GB/T 8731 free-cutting family: 0.40% carbon with 1.20–1.55% manganese (the concept of AISI 1141/1144) plus 0.15–0.25% sulfur for chip control. It is used where turned parts must carry real loads after heat treatment.
Standards: AISI 1141 (near) · GB Y40Mn (GB/T 8731)
Chemical composition compared (%)
| Element | Y30 | Y40Mn |
|---|---|---|
| C | 0.27–0.34 | 0.37–0.44 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.70–1.00 | 1.20–1.55 |
| P | ≤0.06 | ≤0.06 |
| S | 0.15–0.25 | 0.15–0.25 |
Properties compared
| Property | Y30 | Y40Mn |
|---|---|---|
| Tensile strength | 490–610 MPa (hot rolled, typ.) | 590–740 MPa (hot rolled, 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: Y30 · Y40Mn. Substitution decisions for certified parts stay with the design authority.