News center
Hardenability of SAE 8620H Alloy Steel
SAE 8620H is a low-alloy carburizing steel widely specified for components requiring a hard, wear-resistant case combined with a tough, ductile core. The "H" suffix denotes restricted hardenability limits, ensuring consistent response to heat treatment across production batches. This makes SAE 8620H an optimal choice for critical powertrain components such as gears, pinions, camshafts, and universal joints.
The alloy contains nickel (0.40–0.70%), chromium (0.35–0.65%), and molybdenum (0.15–0.25%) as its principal strengthening elements. Nickel contributes to core toughness and impact resistance, chromium enhances hardenability and wear properties, while molybdenum prevents temper embrittlement and controls grain growth during carburizing.
Compared to standard SAE 8620, the 8620H grade offers tighter hardenability bands (typically 85–95% of the maximum achievable hardness at the Jominy position), which reduces distortion during quenching and improves manufacturing predictability.
Typical heat treatment includes carburizing at 900–950°C, followed by oil quenching and tempering. This produces a surface hardness of 58–62 HRC with a case depth of 0.8–1.5 mm, while the core maintains 25–35 HRC with excellent ductility. Fatigue resistance is notably superior to plain carbon steels, with rotating beam tests showing an endurance limit of approximately 450–550 MPa.
For automotive and heavy-duty applications, SAE 8620H consistently delivers the balance of surface durability and impact strength required for long-life gears and shafts. Its predictable hardenability ensures repeatable distortion control, reducing post-heat-treatment grinding costs.
When specifying alloy steels for case-hardened components, SAE 8620H remains a benchmark grade for reliability and performance.
The alloy contains nickel (0.40–0.70%), chromium (0.35–0.65%), and molybdenum (0.15–0.25%) as its principal strengthening elements. Nickel contributes to core toughness and impact resistance, chromium enhances hardenability and wear properties, while molybdenum prevents temper embrittlement and controls grain growth during carburizing.
Compared to standard SAE 8620, the 8620H grade offers tighter hardenability bands (typically 85–95% of the maximum achievable hardness at the Jominy position), which reduces distortion during quenching and improves manufacturing predictability.
Typical heat treatment includes carburizing at 900–950°C, followed by oil quenching and tempering. This produces a surface hardness of 58–62 HRC with a case depth of 0.8–1.5 mm, while the core maintains 25–35 HRC with excellent ductility. Fatigue resistance is notably superior to plain carbon steels, with rotating beam tests showing an endurance limit of approximately 450–550 MPa.
For automotive and heavy-duty applications, SAE 8620H consistently delivers the balance of surface durability and impact strength required for long-life gears and shafts. Its predictable hardenability ensures repeatable distortion control, reducing post-heat-treatment grinding costs.
When specifying alloy steels for case-hardened components, SAE 8620H remains a benchmark grade for reliability and performance.
