Investigation into the role of cooling/lubrication effect of cryogenic minimum quantity lubrication in machining of AISI H13 steel by three-dimensional finite element method

Abstract

This article developed a three-dimensional finite element model of cryogenic minimum quantity lubrication machining in order to investigate the role of cooling/lubrication effect of cryogenic minimum quantity lubrication in machining of AISI H13 steel. In this model, the cryogenic cooling effect provided by refrigerated compressed air is modeled with a convective heat transfer coefficient. A heat transfer window with the temperature and convective heat transfer coefficient of refrigerated compressed air was defined on tool face and workpiece, respectively, which could move at the same speed as cutting tool so as to simulate continuous cryogenic cooling process of cutting zone under cryogenic minimum quantity lubrication condition. The temperature of refrigerated compressed air was set at −10 °C, −30 °C, −50 °C, −100 °C, and −140 °C to study the influence of cryogenic cooling effect of cryogenic minimum quantity lubrication. Frictional contact between tool and chip was modeled with a simple constant shear stress model. Comparative simulations were conducted under different cooling/lubrication conditions, those are, dry cutting, refrigerated compressed air, and cryogenic minimum quantity lubrication. The simulation results show that both cryogenic cooling effect and lubrication effect resulted in reduction in cutting force and tool temperature when machining AISI H13 steel under cryogenic minimum quantity lubrication condition. With a decrease in temperature of refrigerated compressed air, cutting force and tool temperature did not decrease continuously. The reduction in cutting force, maximum tool temperature, and average temperature of rake face and flank face at low and high cutting speeds was strongly attributed to the cryogenic cooling effect and lubrication effect provided by cryogenic minimum quantity lubrication, respectively. A significant reduction in cutting force and tool temperature was caused by the improvement in lubrication effect provided by cryogenic minimum quantity lubrication irrespective of the cutting speed. The trends revealed by the simulations provide helpful information for the development of this technique.