5120 vs 8615
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.
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
8615
Alloy & Engineering Steel
8615 is the low-carbon member of the 86xx triple-alloy carburizing family, sharing 8620 alloy content at slightly lower carbon. It is chosen for small gears and parts where a ductile core is paramount.
Standards: AISI 8615
Chemical composition compared (%)
| Element | 5120 | 8615 |
|---|---|---|
| C | 0.17–0.22 | 0.13–0.18 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.70–0.90 | 0.70–0.90 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.040 | ≤0.040 |
| Cr | 0.70–0.90 | 0.40–0.60 |
| Ni | — | 0.40–0.70 |
| Mo | — | 0.15–0.25 |
Properties compared
| Property | 5120 | 8615 |
|---|---|---|
| Case hardness (carburized) | 58–62 HRC | 58–62 HRC |
| Core tensile strength | 600–850 MPa (typ.) | 650–900 MPa (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: 5120 · 8615. Substitution decisions for certified parts stay with the design authority.