Abstract: Aiming at the distortion problem of pinion shaft of industrial robot planetary reducers during high-temperature carburizing and quenching, the vacuum low pressure carburizing and high pressure gas quenching processes of the precision shaft were studied. The results show that in the heating-up stage, the multi-step heating up method is adopted, the boost stage is used to carry out strong carbon infiltration and diffusion with the alternately pulsed input of acetylene-nitrogen, and the quenching cooling stage with accurately controlled and stabilized the nitrogen pressure at 1.8 MPa (18 bar), the total distortion of the pinion shaft can be controlled within 0.005-0.015 mm. The actual production results show that, by using vacuum low pressure carburizing and high pressure gas quenching technology, the martensitic grade of the pinion shaft in the carburized layer is grade 1, and the retained austenite and carbide are grade 1 to 2, the core microstructure is 1 to 2 grades, and the average surface hardness, core hardness and effective hardened depth of the precision pinion shaft produced by the mass production are 59.7 HRC, 38.6 HRC and 0.681 mm, respectively, all of which meet the technical requirements.

Key words: precision reducer pinion shaft, vacuum low pressure carburizing, high pressure gas quenching