40 vs 1040
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.
40
Carbon Steel
40 is the GB/T 699 counterpart of AISI 1040 / JIS S40C — a step below 45 (1045) in carbon, chosen where weldability and toughness matter slightly more than peak strength.
Standards: DIN 1.0511 (C40) · AISI 1040 · JIS S40C · GB 40 (GB/T 699)
1040
Carbon Steel
1040 is a medium carbon steel for moderately stressed shafts, bolts and gears. It is the plain-carbon predecessor of 5140/40Cr in many cost-sensitive designs, with similar carbon but no chromium hardenability boost.
Standards: DIN 1.0511 (C40) · AISI 1040 · JIS S40C · GB 40
Chemical composition compared (%)
| Element | 40 | 1040 |
|---|---|---|
| C | 0.37–0.44 | 0.37–0.44 |
| Si | 0.17–0.37 | — |
| Mn | 0.50–0.80 | 0.60–0.90 |
| P | ≤0.035 | ≤0.040 |
| S | ≤0.035 | ≤0.050 |
| Cr | ≤0.25 | — |
Properties compared
| Property | 40 | 1040 |
|---|---|---|
| Tensile strength | ≥570 MPa (GB/T 699 reference, normalized blank) | 570–660 MPa (normalized, typ.) |
| Yield strength | ≥335 MPa (reference) | — |
| 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: 40 · 1040. Substitution decisions for certified parts stay with the design authority.