General information
SAE 8620 is a versatile, cost-effective low-alloy carburising steel. After carburising, hardening and tempering it develops a hard, wear-resistant case (58–63 HRC) over a tough, shock-resistant core — one of the most widely used case-hardening grades in general engineering and automotive manufacture.
Similar designations
SAE 862021NiCrMo21.6523805M20SNCM220
Chemical composition
Typical composition limits (weight %). Balance iron.
| Element | Min % | Max % |
|---|---|---|
| Carbon (C) | 0.18 | 0.23 |
| Silicon (Si) | 0.15 | 0.35 |
| Manganese (Mn) | 0.70 | 0.90 |
| Phosphorus (P) | — | 0.025 |
| Sulphur (S) | — | 0.035 |
| Chromium (Cr) | 0.40 | 0.60 |
| Nickel (Ni) | 0.40 | 0.70 |
| Molybdenum (Mo) | 0.15 | 0.25 |
Mechanical properties
Typical values in the carburised, hardened and tempered condition.
| Property | Typical value |
|---|---|
| Case hardness (surface) | 58–63 HRC |
| Core hardness | 30–45 HRC |
| Core tensile strength | 650–950 MPa |
| Core yield strength | 400–700 MPa |
| Core elongation A5 | 10–15 % |
| Supply hardness (annealed) | max. 197 HB |
Case and core properties depend on carburising depth, section size and heat treatment. A mill test certificate is supplied with every dispatch.
Transformation temperatures
| Transformation point | Temperature (°C) |
|---|---|
| Ac1 | 720 |
| Ac3 | 840 |
| Ms (core) | 400 |
Heat treatment recommendations
| Treatment | Temperature cycle | Cooling / quenching |
|---|---|---|
| Normalizing | 870–900 °C | In still air |
| Carburising | 880–930 °C | Case depth to requirement |
| Core refining | 870–900 °C | Quench in oil |
| Hardening | 780–820 °C | Quench in oil |
| Tempering | 150–200 °C | In air |
| Soft annealing | 680–710 °C | Furnace cool |
Typical case-hardness profile
Indicative hardness gradient from the carburised surface into the tough core, for a typical effective case depth. Actual profile is set by the carburising cycle.
Hardness vs depth from surface
Physical properties
Typical values at ambient temperature unless stated.
| Property | Typical value |
|---|---|
| Young’s modulus | 205 GPa |
| Poisson’s ratio | 0.30 |
| Shear modulus | 80 GPa |
| Density | 7,850 kg/m³ |
| Thermal expansion (20–300 °C) | 11.6 µm/m·K |
| Specific heat | 470 J/kg·K |
| Thermal conductivity | 46 W/m·K |
| Electrical resistivity | 0.20 µΩ·m |
Typical applications
GearsCamshaftsGudgeon pinsBushingsBearingsSprocketsKing pins
Disclaimer. The information above is provided for general guidance only and represents typical values for the grade; it is not a warranty or guarantee. Actual properties depend on dimension, heat treatment and processing. Every dispatch is accompanied by a mill test certificate stating the actual results for that heat. Please confirm suitability for your specific application with our technical team.
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