Wear mechanisms of the rough form tools in the automatic screw machine test

Abstract

Tool wear mechanisms of the rough form tools in the automatic screw machine test during machining of bismuth-bearing low carbon resulfurized free machining steel under practical machining conditions were investigated. Four mechanisms, namely mild adhesive wear, abrasive wear, continuous wear, and plastic deformation have been observed to play some roles simultaneously. Mild adhesive wear, which is a wear process taking place during detachment of an adhered chip, is believed to be enhanced by fatigue. Abrasive wear could take place either by oxide inclusions in the workpiece or by the primary carbide particles of the tool freed by some wear mechanisms. Continuous wear has been attributed to some type of atomic process, most probably dissolution of tool material into the chip. On the flank face, continuous, abrasive, and mild adhesive wear are believed to be the major wear mechanisms. On the rake face, continuous wear appears to be the predominant tool wear mechanism. Based on this investigation and consideration of the effect of built-up edge (BUE), reduction of cutting force, optimization of BUE size, stabilization of BUE, and reduction of oxide inclusions are found to be important for reduction of tool wear under practical machining conditions.