4815 vs 4820
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.
4815
Alloy & Engineering Steel
4815 is a high-nickel (3.5%) Ni-Mo carburizing steel for premium gears needing maximum core toughness and case fatigue resistance at low temperature. Its alloy cost confines it to aerospace and high-end industrial gearing.
Standards: AISI 4815
4820
Alloy & Engineering Steel
4820 is the higher-carbon companion of 4815 in the 3.5% nickel carburizing family, giving a stronger core at the same case performance. It is used for large, heavily loaded gears in mining and aerospace service.
Standards: AISI 4820
Chemical composition compared (%)
| Element | 4815 | 4820 |
|---|---|---|
| C | 0.13–0.18 | 0.18–0.23 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.40–0.60 | 0.50–0.70 |
| P | ≤0.035 | ≤0.035 |
| S | ≤0.040 | ≤0.040 |
| Ni | 3.25–3.75 | 3.25–3.75 |
| Mo | 0.20–0.30 | 0.20–0.30 |
Properties compared
| Property | 4815 | 4820 |
|---|---|---|
| Case hardness (carburized) | 58–62 HRC | 58–63 HRC |
| Core tensile strength | 800–1050 MPa (typ.) | 850–1100 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: 4815 · 4820. Substitution decisions for certified parts stay with the design authority.