AISI 8620 Case-Hardening Ni-Cr-Mo Alloy Steel
ASTM A29/A322 · Updated: 2026-05-25
AISI 8620 is a low-carbon nickel-chromium-molybdenum case-hardening steel (0.18-0.23% C) designed for carburizing to produce a hard, wear-resistant surface (60-62 HRC) over a tough, ductile core. The nickel (0.4-0.7%) improves core toughness and case toughness; chromium (0.4-0.6%) and molybdenum (0.15-0.25%) ensure hardenability. After carburizing at 925°C, quenching, and tempering at 150-200°C, the case depth is typically 0.5-2.0 mm depending on carburizing time. Standard material for automotive transmission gears, differential pinions, camshafts, and bearing races requiring high surface hardness with shock-resistant cores.
Quick Facts
| Category | Alloy Steel |
| Standard | ASTM A29/A322 |
| Density | 7.85 g/cm³ |
| Yield Strength | 385 MPa (56 ksi) core |
| Tensile Strength | 615 MPa (89 ksi) core |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN 20NiCrMo2-2 | Compare |
| DIN 1.6523 | Compare |
| SNCM220 | Compare |
| 20CrNiMo | Compare |
| BS 805M20 | Compare |
Related Materials
🧮 Material Weight Calculator
Calculate the weight based on this material's density: 7.85 g/cm³
Frequently Asked Questions
What is the difference between 8620 and 9310 carburizing steels?
9310 has significantly higher nickel (3.0-3.5%) and chromium (1.0-1.4%) for superior core toughness and case toughness, especially at low temperatures. 9310 is specified for aerospace gears and helicopter transmissions where gear tooth fracture would be catastrophic. 8620 is the economical choice for automotive and industrial gears. 9310 costs approximately 2-3× more than 8620.