Evolution Law of Grain Size of High Alloy Gear Steel in Hot Deformation

The change rules of deformation parameters such as temperature, strain and strain rate at different zones of forgings are very complex in the forging process of high alloy chromium-cobalt gear steel, and the deformation parameters have great influence on grain sizes. In this paper, recrystallization model for the steel was established with the material characteristic parameters obtained from the Gleeble isothermal compression test, influencing factors were analyzed based on the model. The results indicate that recrystallization grain size increases with increasing temperature and decreasing strain and strain rate, and the effect of temperature is more obvious than the other two. The average grain sizes are between 27.7μm∼40μm at 1040°C of forging temperature, grain size degree 6∼6.5, meeting the product requirements.