Abstract: The present work has found that the transverse rupture strength of WC-Co hard metals can be improved by quenching heat treatment. The icrement of transverse rupture strength(TRS) is dependent on the cobalt content of hard metal.The higher the cobalt content of hard metal is,the more the increament of transverse rupture strength is. The main rea son is that the transformtion of face centered cubic cobalt stable at high temperature to hexagonal closepacked can be depressed by quenchin g heat treatment.The transformation temperature increases with the increase of cobalt content of hard metal by means of differential thermal anaysis because binder phase of high cobalt hard metal contains higher tungsten content than that of low hard metal during reheating.