Preheating of motorcycle sprocket before carburizing

The heat treatment process standard of mil-h-6857g-83 steel in the United States clearly stipulates that the final processed parts and parts with abrupt change or sharp concave angle in section shall be preheated at 540c or 650C before heating to 704c. For example, carburized parts are carburized after preheating at 500C for 90min. This is beneficial to reduce deformation and adjust carbon potential.