A study on the characteristics of electrical discharge textured skin pass mill work roll

Electrical discharge texturing induces a recast white layer on the skin pass mill work roll surface, which forms the surface topography required for outer autobody steel strips and a heat-affected zone beneath it. The characteristics of these thermally influenced layers were studied by means of optical and scanning electron microscopes, X-ray diffractometer, radio frequency-glow discharge optical emission spectrometer and microhardness tester. It was found that the electrical discharge texturing led to a dramatic hardness drop in the white layer, which was attributed to the high amount of retained austenite. Moreover, softening was observed in over tempered section within heat-affected zone. Sub-zero and cryogenic treatments seem to be potential methods in order to restore the hardness of white layer and over tempered zone with an increase in both. Additionally, de-ionised water was found to be a promising dielectric liquid to abstain from retained austenite.