RESEARCH OF THE THERMAL CYCLE ON THE SURFACE OF THE BILLET AS A CONSEQUENCE OF PLASTIC DEFORMATION DURING MECHANICAL PROCESSING

Abstract

While the metallurgical characteristics of machined surfaces are constantly improving, there is still a lack of understanding regarding the thermal conditions in which these surfaces are in the process of interaction between the workpiece and the side surface. During machining of high-carbon alloys, very little is known about temperature changes in the internal volume of the machined part, where the workpiece material interacts with the cutting edge of the tool. In this work, the characteristics of the thermal field and the resulting surface metallurgy induced in high carbon alloys for cutting scenarios involving various combinations of thermomechanical boundary conditions were studied. The analysis of the development of the thermal field on the surface of the workpiece made it possible to reveal the heating and cooling rates caused by cutting, allowing to describe two different types of thermal cycle, with the structure Heating-Peak-Cooling and Heating-Quasi-isothermal Deformation-Cooling depending on the aggressiveness of the process. The subsurface thermal zone is found to be related to the deformation caused by cutting because it combines information about the magnitude of the thermal field and the speed of the process. It was found that the highest rate of heat generation caused by plastic deformation occurred in the thin surface layers at the beginning of the contact between the workpiece and the side surface, which was related to the conditions under which the white layers are generated. The analysis of the energy balance indicated the development of a less strong and less impulsive deformation process at greater depths below the surface, which was related to the mechanism of the formation of material resistance layers. Thus, the thermal effect on the processed surfaces was interconnected with their final metallurgical structure, which made it possible to deeply understand the physical conditions that arise when cutting high-carbon alloys.