Studies on Heat-treatments of High Alloy Tool Steels (3rd Report). On Stepped-Quenching of High-Carbon High-Chromium Steel

Abstract

It was described in previous reports that the stepped-quenching method may be adapted to such high-alloy steels to prevent quenching deformation and quenching crack. In this report the effects of stepped-quenching on the hardness, the quantity of retained austenite and the mechanical properties were investigated in comparison with ordinary quenching method by means of hardness measurement, magnetic analysis, repeated impact test and bending test. The results are summarized as follows: (1) The amount of retained austenite in stepped-quenched steel is more than that in ordinarily-quenched steel. (2) The hardness and the amount of retained autsenite decrease with increase of the holding time in the hot bath (500°) in stepped quenching. (3) The amount of retained austenite also increases remarkably with decrease of the cooling rate from the hot-bath temperature (500°). (4) The stepped-quenching method improves the mechanical properties.