4320 vs 8620
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.
4320
Alloy & Engineering Steel
4320 is a Ni-Cr-Mo carburizing steel whose ~1.8% nickel gives a markedly tougher core than 8620. It is specified for larger, shock-loaded gears in mining, truck and industrial transmissions.
Standards: DIN 20NiCrMo2-2 family (near) · AISI 4320 · JIS SNCM420 · GB 20CrNiMo
8620
Alloy & Engineering Steel
8620 is the standard carburizing (case-hardening) gear steel of the Americas: a low-carbon Ni-Cr-Mo grade that forms a hard wear-resistant case over a tough core.
Standards: DIN 1.6523 (21NiCrMo2-2) · AISI 8620 · JIS SNCM220 · GB 20CrNiMo
Chemical composition compared (%)
| Element | 4320 | 8620 |
|---|---|---|
| C | 0.17–0.22 | 0.18–0.23 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.45–0.65 | 0.70–0.90 |
| P | ≤0.035 | — |
| S | ≤0.040 | — |
| Cr | 0.40–0.60 | 0.40–0.60 |
| Ni | 1.65–2.00 | 0.40–0.70 |
| Mo | 0.20–0.30 | 0.15–0.25 |
Properties compared
| Property | 4320 | 8620 |
|---|---|---|
| Case hardness (carburized) | 58–62 HRC | 58–63 HRC |
| Core tensile strength | 750–1000 MPa (typ.) | — |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Core tensile | — | 700–950 MPa |
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: 4320 · 8620. Substitution decisions for certified parts stay with the design authority.