抄録
Cold forging process is one of the most popular processes to manufacturing the automotive parts such as gears and shafts. However, abnormal austenitic grain growth sometimes occurs when the cold forged parts are heated for carburizing treatment without normalizing process between cold forging and carburizing. This grain coarsening is often harmful to fracture toughness and fatigue strength.
We have been studying about the influence of elements and process on the grain coarsening property of case hardenig steels and has developed a new niobium steel “ATOM steel”.
ATOM steel is characterized by increasing the amount of carbide and nitride precipitates to suppress the abnormal grain coarsening. It shows 50K higher grain coarsening temperature than conventional steels.
