Makruha T. The increase of physical and mechanical properties of steel by the formation of polygonization nanosized subgrains

The thesis is devoted to the solution of scientific and technical task of increasing the level of physico-mechanical and performance characteristics of steel products by the formation of polygonization nanosized subgrains due to the combination of cold dynamic deformation and static deformation with subsequent pre-recrystallization heat treatment. The method of increasing physico-mechanical and performance characteristics of steel products is developed. It consists in that steel products after preliminary dynamic deformation by 30 % are subjected to static deformation by 30 % and then are heated up to the temperature of primary recrystallization initiation, then held during time up to 60 minutes and cooled down to the temperature of surrounding with cooling rate that makes subgrain growth impossible. Conducted experimental and theoretical studies allowed selection and justification of the type and rate of steel deformation as well as the development of physical and technological bases of the formation of nanosized polygonization substructure. The impact of the type and rate of deformation on the hardness of technically clear iron is experimentally determined. The regularities of the increase of hardness of technically clear iron and steels after combined deformation (dynamic deformation by 30 % and static deformation by 30 %) using fixation of grinded polygonization substructure using pre-recrystallization heat treatment are experimentally determined for the first time. It is found out, that stabilization of the substructure of technically clear iron and nickel after their combined deformation and pre-recrystallization heat treatment during 60 minutes takes place independently on materials crystal lattice.