SCM420 is a chromium-molybdenum low-alloy case-hardening steel specified under JIS G 4053. Designed for carburizing applications, it delivers surface hardness of 58–62 HRC combined with core toughness in the HRC 32–42 range after heat treatment. Equivalent to GB 20CrMo, DIN 25CrMo4 (1.7218), and AISI 4120 / 4118, SCM420 is widely specified for heavy-duty transmission components and oilfield equipment requiring high surface wear resistance with a strong, ductile core.
SCM420 Equivalent Grades
| Standard | Designation |
|---|---|
| JIS G 4053 | SCM420 / SCM420H |
| GB/T 3077 | 20CrMo / 20CrMoH |
| DIN EN 10084 | 20CrMo4 (1.7321) / 18CrMo4 (1.7243) |
| DIN | 25CrMo4 (1.7218) |
| AISI/SAE | 4120 / 4118 |
| ISO 683-11 | 20MnCr5 |
| GOST | 20ХМ |
SCM420 Applications in Oil & Gas
SHUNFU METAL SCM420 Supply Range
SCM420 Chemical Composition (JIS G 4053)
| Element | Content (wt%) |
|---|---|
| C | 0.18 – 0.23 |
| Si | 0.15 – 0.35 |
| Mn | 0.60 – 0.90 |
| P | ≤ 0.030 |
| S | ≤ 0.030 |
| Cr | 0.90 – 1.20 |
| Mo | 0.15 – 0.25 |
| Ni | ≤ 0.25 |
| Cu | ≤ 0.30 |
SHUNFU METAL melts SCM420 via EAF + LF + VD route, with optional ESR for premium cleanliness. Residual elements (P, S, Cu, Ni) are tightly controlled below JIS limits to ensure consistent carburizing response.
SCM420 Mechanical Properties
Quenched & Tempered (880°C Q + 500°C T)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 885 MPa |
| Yield Strength | ≥ 685 MPa |
| Elongation (δ₅) | ≥ 12% |
| Reduction of Area | ≥ 50% |
| Impact (Akv) | ≥ 78 J |
| Hardness | ≤ 197 HBW |
Carburized + Quenched + Low-Temp Tempered
| Location | Hardness |
|---|---|
| Case (surface) | 58 – 62 HRC |
| Core | 32 – 42 HRC |
Typical case depth: 0.75–1.25 mm at 926°C × 4h gas carburizing. SCM420 achieves 3–5 HRC higher core hardness than SCM415 under identical quench conditions. Hardenability verified by Jominy end-quench per JIS G 0561.
SHUNFU METAL Manufacturing & Quality Control for SCM420
SCM420 Heat Treatment & Processing Guide
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