AUSTEMPERING HEAT TREATMENT METHOD

摘要

PURPOSE: An austempering heat treatment method is provided which is capable of shortening heat treatment time and reducing energy consumption accordingly by partially austempering heat treating a desired part of work only. CONSTITUTION: In a method for austempering a work formed of ductile cast iron, the austempering heat treatment method comprises a preheating step (S101) of preheating the work; an isothermal heat treating step (S103) of rapidly heating the preheated work and isothermally heat treating the rapidly heated work by induction heating to partially austenitize a specific part of the work only; a quenching step (S105) of bainitizing the surface of the work by cooling the surface of the work; and a tempering step (S107) of maintaining the work to an isothermal temperature to stably form bainite structure on the surface of the work, wherein the work is preheated to the temperature range of 500 to 600 deg.C in the preheating step, and wherein the work is isothermally heat treated to the temperature range of 890 to 930 deg.C for 1 to 10 minutes in the isothermal heat treating step.