The shape change and redistribution of non-metallic inclusions in steels during working by pressure

Abstract

Peculiarities of the shape change and redistribution of non-metallic inclusions of various types during working by pressure of steels (rolling, forging, drawing) were investigated. The concept of plastic deformation of inclusions is considered from the standpoint of physical mesomechanics of heterophase alloys. It is shown that non-metallic inclusions contribute to the localization of plastic deformation, which is accompanied by the interaction of non-metallic inclusions and the steel matrix, which determines their common plastic change in shape and redistribution of inclusions in the steel matrix. The peculiarities of these processes under different types and temperature regimes of working by pressure, which determines the nature of stresses near the inclusions and the plastic flow of the steel matrix, have been established. It is shown that the temperature regime of pressure treatment determines the possibility of relaxation processes in the steel matrix near the inclusions and the level of plasticity of the inclusions themselves and the inclusion-matrix interphase boundaries. The influence of the temperature regime of hot deformation of sheet steels and wire rod on the nature of shape change and the deformability of plastic inclusions and their destruction (brittle or ductile), as well as the plasticity of the steel matrix, frictional forces at the inclusion-matrix boundaries, and the plasticity of the latter during hot rolling were established. It is shown that when considering the plastic behavior of non-metallic inclusions in a plastic steel matrix, the behavior of the inclusion-matrix interphase boundaries under different deformation conditions is of great importance. Peculiarities of the dynamic character of the joint deformation of the inclusion-matrix system, which is associated with the development of competing processes at the interphase boundaries of the inclusion-matrix: interphase friction and slipping, have been studied. The features of hot and cold slipping occurring at different deformation temperatures are discussed. It is shown that the mechanisms of each of the mentioned processes depend on the temperature regime of the deformation, the level of plasticity of the inclusions and the steel matrix. The influence of the method of cold deformation (rolling and drawing) on the shape change of plastic inclusions and the redistribution of non-deformable inclusions in the steel matrix was established. The processes that determine the level of plasticity of non-metallic inclusions and inclusion-matrix boundaries and significantly affect the nature of the shape change of inclusions and their redistribution in the steel matrix in the process of the working by pressure of steels, which affect their technological plasticity at different temperatures and methods of deformation, are considered.