20Cr vs 5120
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.
20Cr
Alloy & Engineering Steel
20Cr is China’s basic carburizing chromium steel (GB/T 3077), the counterpart of AISI 5120 and JIS SCr420 for case-hardened gears and shafts.
Standards: DIN 1.7027 (20Cr4) · AISI 5120 · JIS SCr420 · GB 20Cr (GB/T 3077)
5120
Alloy & Engineering Steel
5120 is a chromium case-hardening steel for small gears and wear parts. With about 0.8% chromium it forms a hard carburized case over a tougher core than plain carbon carburizing grades give.
Standards: DIN 1.7027 (20Cr4, near) · AISI 5120 · JIS SCr420 · GB 20Cr
Chemical composition compared (%)
| Element | 20Cr | 5120 |
|---|---|---|
| C | 0.17–0.24 | 0.17–0.22 |
| Si | 0.17–0.37 | 0.15–0.35 |
| Mn | 0.50–0.80 | 0.70–0.90 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.035 | ≤0.040 |
| Cr | 0.70–1.00 | 0.70–0.90 |
Properties compared
| Property | 20Cr | 5120 |
|---|---|---|
| Tensile strength | ≥835 MPa (GB/T 3077 reference Q&T) | — |
| Yield strength | ≥540 MPa (reference) | — |
| Case hardness (carburized) | 58–62 HRC | 58–62 HRC |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Core tensile strength | — | 600–850 MPa (typ.) |
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: 20Cr · 5120. Substitution decisions for certified parts stay with the design authority.