The effect of process of warm-forging at 880 ~ 930 °C on growth of austenite grain of gear steel 20CrMnTiH3 is analyzed by examination of physicochemistry and original material austenite grain size to get that the austenite of steel is easy abnormally coarsening during carburizing process at 890 ~ 920 °C after warm-forging gear processing

that transforms to coarse martensite structure after cemented-quenching at 830 °C. There is no obvious improvement for coarse austenite grain of carburized and quenched gear steel 20CrMnTiH3 by tempering and normal normalizing process after warm forging

but the occurrence of coarse martensite of carburized and quenched steel is avoided by isothermal normalizing process at 950 °C for 1 h air cooling to 650 °C for 8 h air cooling.