Plyakhtur O. Control of structure, properties and heredity of steels in the charge-melt-casting system.

The object of research is the proceses of crystallization, structure formation and emplacement of the genetic characteristics of the metal in cast carbon and alloy steels under intensive and regulated cooling; the laws of heredity and transformation of the cast structure at various time-temperature conditions subsequent remelting and crystallization. Subject of research - the characteristics of the cast structure, phase composition, dispersion and density of dendrite structure, segregation of chemical elements, physical and mechanical properties. Using the methods of metallographic, electron microscopy, X-ray, chemical, thermal and differential-simultaneous colorimetric assay, as well as methods for determining the mechanical properties of mathematical statistics and computer processing of the experimental results. On the basis of the systematic investigations of the influence regularities of primary cast structure formation and transformation, phase composition and physical-mechanical properties of carbon and alloy steels due to the time-temperature conditions of crystallization and cooling castings were established. The interaction of the main factors determining the structure and properties of cast steels is reviewed and manifestations of structural and steel heredity summarized. The dominant role of time-temperature conditions of crystallization and structure formation in connection with the presence of heredity in various post-processing operations of cast steels is shown. It was found that the intensity increase of the heat sink and the creation of a significant temperature gradient in the two-phase region opens up the possibility of effective control grain size, dispersion and density of dendritic structure, segregation, solid solution doping, the degree of disequilibrium and the formation of certain hereditary features in cast steel structure. It is shown that rapidly cooled steel crystallized with dispersed, more uniform and nonequilibrium initial structure and provide a high level of mechanical properties of castings for subsequent remelting and final processing. For the first time it was found that the temperature of the melt equilibrium microinhomogeneous (Tr), which determines the temperature range structural and metallurgical heredity is not constant, and the degree of disequilibrium is caused by the initial properties of charge. It was shown that the charge laid down in the metal phase-structural elements with positive or negative inheritance can be strengthened or weakened in the remelting of steel using the appropriate temperature in the melt processing precrystallization between the heat sink and regulated in the crystallization and solid phase transformations of steels. The results of research and pilot test give new opportunities of focused control of cast structure, improve the properties of steel castings, the development of new casting technologies and materials.