Studying on the Internal Quality of Steel at Various Stages of Production: Slab-Rolled Metal

Abstract

In this work, the characteristics of the cast structure formed under various conditions of slab casting and the micro-structure of hot-rolled sheets made from them are studied by a complex of chemical and metal-graphic analysis methods. This article presents the results on cast structure's dispersion studying of continuously cast slab that depend on the casting speed as well as hot rolled steel's the microstructure and mechanical properties produced from experimental slabs. A comprehensive study shows that continuously cast slab's solidification rate determines the dispersion of the dendritic structure and the microscopic inhomogeneity degree. It is established that the dendritic structure density is the degree indicator of cast steel’s microchemical homogeneity. In all structural zones and in the whole thickness of a continuous slab with a thickness of 105 mm, the dendritic structure density and the micro-chemical homogeneity increases with increasing crystallization rate. Using the methods of quantitative metallography, it is shown that with an increase in the crystallization rate, the resulting cast structure becomes significantly dispersed. The study revealed a pattern between the initial austenitic structure of a continuously cast slab obtained at different crystallization rates and the structure of hot-rolled rolled products obtained by direct rolling, when hot slabs are placed in a heating furnace before phase transformations γ→α in the steel structure.