18CrNiMo7-6 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.
18CrNiMo7-6
Alloy & Engineering Steel
18CrNiMo7-6 is the EN 10084 case-hardening steel (1.6587) for the largest, most heavily loaded gears in wind, marine and industrial service. Its high Cr-Ni-Mo content keeps case and core properties uniform in very large sections.
Standards: DIN 1.6587 (18CrNiMo7-6) · AISI 4320 (near)
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 | 18CrNiMo7-6 | 4320 |
|---|---|---|
| C | 0.15–0.21 | 0.17–0.22 |
| Si | ≤0.40 | 0.15–0.35 |
| Mn | 0.50–0.90 | 0.45–0.65 |
| P | ≤0.025 | ≤0.035 |
| S | ≤0.035 | ≤0.040 |
| Cr | 1.50–1.80 | 0.40–0.60 |
| Ni | 1.40–1.70 | 1.65–2.00 |
| Mo | 0.25–0.35 | 0.20–0.30 |
Properties compared
| Property | 18CrNiMo7-6 | 4320 |
|---|---|---|
| Case hardness (carburized) | 58–62 HRC | 58–62 HRC |
| Core tensile strength | 900–1200 MPa (typ.) | 750–1000 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: 18CrNiMo7-6 · 4320. Substitution decisions for certified parts stay with the design authority.