Investigation of transformations in non-metallic inclusions by high-temperature metallography

Purpose. It is interest to research the transformations in non-metallic inclusions under high-temperature heating and laser treatment of steels. It is necessary to analyse the peculiarities of influence of slow and high-speed heating on the different transformations in different types of inclusions that can to cause the change of properties of inclusions and steels after heat or laser treatment.Also it is necessary to discover the possibilities of controlling heterogenezation of non-metallic inclusions and steel matrix in the time of formation of local gradiental and composite zones of contact interaction in systems inclusion-matrix. The goal of work is to discover the fundamental types of transformations in non-metallic inclusions by high-temperature metallography and laser heating. Methodology. The materials for investigation were commercial steels containing different non-metallic inclusions. The specimens of different steels with preliminary polished surface were exposed to heating in vacuum on the installations IMASH-5C and Rainhart and also exposed to laser beaming on the installations GOS-30M and GUANTUM-16. Methods of investigation ?vacuum metallography, petrography and optical microscopy (Neophot-21) were used. Findings. It was fixed under high-temperature heating in vacuum the different transformations in non-metallic inclusions take place which cause by polymorphism, transition into more stable condition, precipitation and dissolution of second phase, change of chemical composition. These transformations cause the stresses promoting local spontaneous recrystallization. Under high-temperature heating dissociation and dissolution ofnonmetallic inclusions takes place that in accompanied by local saturation of steel matrix of cascade type and also by precipitation of “satellite” inclusions.Redistribution of inclusions under high-temperature heating promotes decoration of high-temperature boundaries and manifestation of structural heredity. Under laser action melting and speed crystallization of non-metallic inclusions, shear polymorphic transformations, transition into more or less stable condition precipitation and dissolution of second phase change of chemical composition, reduction of metals from oxides, formation of gradiental and composite microzones takes place. Thepeculiarities of transformations in non-metallic inclusions being on the polished surface under speed heating in the condition of laser action were investigated.The peculiarities of transformations in non-metallic inclusions under ordinary and high-speed heating are discussed. Originality. The peculiarities oftrans formations in non-metallic inclusions under different conditions of heating and cooling taking place under interaction between non-metallic inclusions and steel matrix were determined. Practical value. The using of receiving results will allow to elaborate the methods and regimes of different types of treatment allowing to influence on the sizes, chemical composition, structure and distribution of non-metallic inclusions in steels with the aim of raise of mechanical properties.