Electrical-discharge wire cutting of ADI and its effect on impact energies

This study built up a set of machining data for electrical-discharge wire cutting (EDWC) of austempered ductile iron (ADI). The treated ADIs with the optimum toughness and the superior strength and hardness were very difficult to machine by the traditional technique. The EDWC process was used to cut the specimens of ADI and the remelted layer and the heat affected zone of the cut surfaces were measured and observed. Optimum cutting conditions were suggested for ADIs with different nodular counts and/or with varying matrix structures. Experimental results showed that if ADIs are cut by EDWC, then the formation of microvoids due to the decarburization and vaporization of graphite nodules at the remelted layer greatly deteriorate the quality of the machined surface. A severe bubbling was observed during cutting. This bubbling in the pool of dielectric fluid markedly lowered the cutting feedrate of EDWC. A model was proposed to correlate the cutting feedrate with the thickness of the workpiece, the time of the discharge spark, the feedrate override of the table, nodule counts of irons and the per cent retained austenite of ADIs.