Quality improvement through microstructure control for superior machinability of cast irons

Abstract

The purpose of this research was to study the influence of microstructure on chip formation and other machinability criteria for cast irons. It is recognized that machinability of cast irons is influenced by a complex interplay of graphite morphology and matrix structure. However, the effect of these microstructural variables on the measures of machinability of cast irons has not been adequately investigated. As a consequence the problem of variability in the machinability of this group of materials is not well understood. In this study, slow speed machining and the quick-stop device method were used to investigate the mechanism by which graphite morphology and the matrix structure influence the machining properties of cast irons. Furthermore, turning tests were used to study machinability as characterized by tool life, machining forces and surface roughness for these materials. Relationships between chip formation and other machinability criteria were then developed and analyzed. Finally, empirical models that relate machinability to microstructures for cast irons were developed. The study showed that chip formation and other machinability parameters for cast irons were influenced by both graphite morphology and matrix structure. In addition, the empirical models revealed that machinability of cast irons was not only influenced by microstructural variables but also by the interaction of the variables with cutting conditions.