Managing Distortion Through Carburizing and Hardening of Gears
Covers steel hardenability, carburizing temperature uniformity at 920-940°C, and quenching medium selection for controlling gear deformation.
Variables That Drive Distortion
Steel hardenability
As the hardenability of a steel rises, so does its tendency to distort. 20CrMnTi is a common carburizing grade whose hardenability sits in the middle range, which keeps distortion manageable. Where tighter accuracy is demanded, grades offering more consistent hardenability — 20CrNiMo or 20CrMo, for instance — can be specified.
Uniformity of carburizing temperature
A typical carburizing cycle runs at 920~940°C. Across the furnace, temperature variation must stay inside ±5°C. Should the temperature field be uneven, case depth will vary from one region of the gear to another, and the resulting distortion will not be uniform.
Quenching medium choice
- Hot oil (80~120°C): distortion is kept low; fits gears of module M≤6
- High-speed quenching oil (40~60°C): a middle cooling rate; fits gears of module M6~M12
- Salt bath (160~220°C): little distortion, yet equipment cost is high; fits precision gears
How parts are loaded into the furnace
- Hang gears vertically or lay them flat; do not stack them
- For long shaft-type gears, vertical hanging prevents bending
- Dedicated fixtures should hold thin-walled gears in place
Distortion Countermeasures
| Application Scenario | Measure | Effect |
|---|---|---|
| Ground gears | Reserved gear grinding allowance | 0.15~0.30mm per side |
| Thin-walled gears | Press quenching | Deformation can be reduced by 50% |
| High-precision gears | Cryogenic treatment (-80°C) | Stabilizes dimensional accuracy |
| All carburized and quenched gears | Secondary tempering | Stress relief |
PinyiGear relies on proven carburizing and quenching methods. Module, diameter, tooth count and accuracy grade follow the customer drawing.