2017 Volume 58 Issue 681 Pages 936-942
In the processing of austenitic stainless steel SUS304, strain-induced martensitic deformation occurrs. In micropart processing, the effect on grain size becomes greater than that in the macropart processing. We reported that the grain size affects the stability of the sheared surface length in micropierced parts. In parthicular, the stability of the fractured surface length is affected by the grain size. The grain size of 3.0 µm yields the most stable fractured surface length. However, stabilization mechanism of start position of the fractured surface has not been clarified. In this study the grain deformation and transformation in micropiercing with coarse and ultrafine-grained SUS304 were investigated by EBSD (electron backscatter diffraction) analysis. Furthermore, the effects on the grain phase and misorientation angle in process-affected zones are reported. It was found that strain-induced martensitic deformation affected the stability of the sheared surface. The selection of an appropriate grain size is required to enable micropiercing.
