In recent years, the general trend is to minimize the carbon content of austenitic stainless steel for the enhancement of corrosion resistance and the restriction of the formation of carbides. Despite the wide use of low-carbon SUS 304, basic research on the machinability of these materials is rare. In order to clarify the effect of carbon content on the machinability of SUS 304, the relationships between the carbon content and mechanical properties, carbon content and cutting characteristics are investigated and the mechanism by which drill life is shortened with high-carbon SUS 304 is examined. The following results are obtained from this study. A sharp drop in drill life with increasing carbon content occurs for austenitic stainless steed. The tensile strength, the yield strength and the shearing energy of high-carbon SUS 304 are higher than those of low-carbon SUS 304. In addition, the work hardenability of high-carbon SUS 304 is larger, and as a consequence, the cutting forces and the cutting temperature increase, leading to drill wear and a higher propensity for chip adhesion and consequently, shorter drill life. Work hardening of the upper layer of the drilled surface of high-carbon SUS 304 is severe compared with low-carbon SUS 304. The shorter drill life associated with drilling high-carbon SUS 304 is attributed to the high hardness of the work-hardened layer over a greater depth.
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