Gears, as the essential powder transmitting components, are used in every industry, especially automotive gears desired with long-life, safety and reliability, and lightweight. The mechanical properties and machinability of gear steels are largely influenced by the morphology of sulphide inclusions formed in the gear steels. To eliminate or reduce the adverse effects of sulphides, this project will investigate the modification of sulphides by addition of Ca, Mg, Al and Zr elements, which is associated with entire processing of gear steels. The outcomes will help Baosteel to further improve and develop high-end gear steels with both excellent mechanical properties and machinability.