Effects of EDM on Thermal Fatigue of Die Steel (2nd Report)

Chracteristics of Thermal Fatigue of Quenched and Tempered SKD61 Die Surface after EDM and WEDM

Abstract

It has been found that the eroded layers of die steels which are formed after the electric discharge machining (EDM) and the wire electric discharge machining (WEDM) affect the quality or accuracy of dies. The effects of EDM and WEDM on the thermal fatigue of quenched and tempered SKD61 die surface have been studied by measuring residual stress and observing cracks. The residual stress in the surface of die was measured using the X-ray method. The main results obtained are as follows. (1) The tensile stress in the die surface, which was generated during EDM and WEDM decreased with increasing the heating and cooling cycles. (2) The residual stress change curve suggests that compression stress is generated in the deep region of the die surface after the thermal fatigue test. (3) The number of cracks generated during the thermal fatigue test decreased with increasing the energy supplying duration, τ_on.