Masahide Umino

Role of alloying elements on machinability of plastic-molding steels

Abstract The influence of silicon and other alloying elements of plastic-molding steels on machinability in face-milling and ball-nose end-milling was investigated. Increase of silicon content decreased the adhesion of chips to a tool and as a result, tool life increased in a dry cutting condition. Vanadium had a similar effect, especially at relatively low cutting speed. To understand these phenomena, the chip surface was analyzed. From these results, it is proposed that low melting temperature oxides of the Fe–Si–O and Fe–V–O systems are formed on the chip surface of high-silicon steel and vanadium-added steel; these oxides lubricate the interface between chip and tool. On the other hand, manganese and chromium that on believed to are form the Fe–Mn–O and Fe–Cr–O oxide film of high melting temperature reduced the lubrication effect. Carbon also decreased tool life due to an increase of pearlite, while the addition of sulfur did not influence tool life.