METHOD FOR HEAT-TREATING UPPERMOST SURFACE OF SPHEROIDAL GRAPHITE CAST IRON AND SPHEROIDAL GRAPHITE CAST IRON HEAT-TREATED BY THE SAME

摘要

Disclosed are a method for heat-treating a surface of a spheroidal graphite cast iron, particularly, heat-treating an uppermost surface of spheroidal graphite cast iron, and spheroidal graphite cast iron heat-treated by the same. The method may include first heat treating for forming ferrite and second heat treating for oxy-nitriding. The spheroidal graphite cast iron heat-treated includes an oxidation layer and a compound layer having a thickness of about 15 to 30 μm, which may be uniform. The method of the heat-treating may decrease the pearlite fraction in the uppermost surface of spheroidal graphite cast iron and increase the ferrite fraction by forming ferrite, thereby forming a compound layer having a thickness of about 15 to 30 μm during an oxy-nitriding heat treatment.