What Is The Best Steel For Spur Gear ?
Dec 29, 2025| 🛠️ High-Frequency Recommended Steel Types and Suitable Applications
1. 20CrMnTi (infiltrated carbon steel)
• Features: Low carbon alloy structural steel, with a surface hardness of 58-62HRC after carburizing and quenching, and good core toughness (≥ 900MPa tensile strength).
• Applicable scenarios: gears with medium to low speeds and moderate loads (such as automotive gearbox gears and machine tool gears), with extremely high cost-effectiveness.
2. 40CrNiMoA (quenched and tempered steel)
• Features: Medium carbon alloy structural steel, with a hardness of 28-32HRC after quenching and tempering, and excellent comprehensive mechanical properties (tensile strength ≥ 980MPa, impact toughness ≥ 63J).
• Applicable scenarios: High speed heavy-duty gears (such as wind turbine gearboxes, ship transmission gears) with outstanding fatigue resistance.
3. 18CrNiMo7-6 (high hardenability carburizing steel)
• Features: European standard high-end carburizing steel, uniform depth of carburizing layer, surface hardness of 58-64HRC, and core hardness of 30-45HRC.
• Applicable scenarios: High precision, high reliability gears (such as aviation engine gears, robot reducers), high cost but top-notch performance.
4. 20Cr2Ni4A (high-strength carburizing steel)
• Features: High nickel content (3.25-3.75%), surface hardness of 60-63HRC after carburizing, and core impact toughness ≥ 70J.
• Applicable scenarios: Heavy duty gears that withstand impact loads (such as mining machinery, rolling mill gears).
📊 Quick Selection Reference Table
| Working Condition | Recommended Materials | Heat Treatment Method | Typical Applications |
| Low speed light load (such as toy gears) | 45 steel (ordinary carbon steel) | Normalization/tempering | Small transmission mechanism |
| Medium speed medium load (car gearbox) | 20CrMnTi | Carburizing quenching+low-temperature tempering | Passenger car manual transmission gear |
| High speed heavy-duty (wind turbine gearbox) | 40CrNiMoA | Quenching and surface hardening | 1.5MW wind power main gear |
| High precision and high impact (robot) | 18CrNiMo7-6 | Carburizing quenching+grinding | Industrial robot RV reducer gear |
💡 Key selection principles
Hardness and toughness balance: Surface hardness ensures wear resistance, and core toughness prevents fracture (carburizing steel is suitable for "surface hardness and core toughness", quenched and tempered steel is suitable for overall toughness).
Process adaptability: Carbon steel requires reserved machining allowance (deformation after carburizing), while quenched and tempered steel can be directly precision cut.
Cost control: 20CrMnTi is preferred for ordinary machinery, and imported steel grades such as 18CrNiMo7-6 are considered for high-end equipment.