SCr420 vs SCM420
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.
SCr420
Alloy & Engineering Steel
SCr420 is the chromium-only carburizing steel of JIS G4053, the Japanese counterpart of AISI 5120. Without molybdenum it is the economy case steel for small gears and shafts in Japanese and Asian drivetrains.
Standards: DIN 1.7027 (20Cr4, near) · AISI 5120 · JIS SCr420 (JIS G4053) · GB 20Cr
SCM420
Alloy & Engineering Steel
SCM420 is the 0.20% carbon Cr-Mo carburizing steel of JIS G4053 (AISI 4120 class) — the standard Japanese grade for medium gears and transmission shafts that need a wear-resistant case over a stronger core than SCM415 gives.
Standards: DIN 20CrMo4 type (near) · AISI 4120 (near) · JIS SCM420 (JIS G4053) · GB 20CrMo (near)
Chemical composition compared (%)
| Element | SCr420 | SCM420 |
|---|---|---|
| C | 0.18–0.23 | 0.18–0.23 |
| Si | 0.15–0.35 | 0.15–0.35 |
| Mn | 0.60–0.90 | 0.60–0.90 |
| P | ≤0.030 | ≤0.030 |
| S | ≤0.030 | ≤0.030 |
| Cr | 0.90–1.20 | 0.90–1.20 |
| Mo | — | 0.15–0.25 |
Properties compared
| Property | SCr420 | SCM420 |
|---|---|---|
| Case hardness (carburized) | 58–63 HRC | 58–63 HRC |
| 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: SCr420 · SCM420. Substitution decisions for certified parts stay with the design authority.