SNCM220 vs 4320
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.
SNCM220
Alloy & Engineering Steel
SNCM220 is the JIS Ni-Cr-Mo carburizing steel — the exact JIS designation of the AISI 8620 gear steel concept, and also cross-referenced to the 4320 family. It is the standard Japanese case steel for transmission gears needing a hard case over a fatigue-resistant core.
Standards: DIN 1.6523 (21NiCrMo2-2, near) · AISI 8620 · JIS SNCM220 (JIS G4053) · GB 20CrNiMo
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
Chemical composition compared (%)
| Element | SNCM220 | 4320 |
|---|---|---|
| C | 0.17–0.23 | 0.17–0.22 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.60–0.90 | 0.45–0.65 |
| P | ≤0.030 | ≤0.035 |
| S | ≤0.030 | ≤0.040 |
| Cr | 0.60–0.90 | 0.40–0.60 |
| Ni | 0.40–0.70 | 1.65–2.00 |
| Mo | 0.15–0.25 | 0.20–0.30 |
Properties compared
| Property | SNCM220 | 4320 |
|---|---|---|
| Case hardness (carburized) | 58–63 HRC | 58–62 HRC |
| Core tensile | 700–950 MPa | — |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Core tensile strength | — | 750–1000 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: SNCM220 · 4320. Substitution decisions for certified parts stay with the design authority.