The structural heredity demonstration and its effect on the properties of hot-rolled tubing stocks of various diameters

Abstract

The number of redistributions decreasing tendency in the production of rolled products, with all the positive economic effect, leads to the fact that the metal is subjected to a less intense deformation effect at low temperatures. In other words, the hereditary influence of the morphological features of the primary crystallization structure associated with the distribution concentration inhomogeneity of the segregating elements during crystallization (austenite and ferrite stabilizers) will be significantly higher. An analysis of the features of the final structure hereditary formation and the properties of tubing stocks obtained from continuously-cast steels of grades 45 and 20 was carried out. Two different etching solutions were used in the work. The combined approach in revealing the structure allows correlating the location nature of the final ferrite-pearlite and primary dendritic structure. It was established that when applying high degrees of tubing stocks reduction, ferrite-pearlite inhomogeneity, which is formed in rolled products from carbon steel, is due to the predominant formation of ferrite in lakes around sulfide inclusions. It is determined that finer pearlite grain is formed with a slight deformation of 45 grade steel in areas corresponding to the former interdendritic spaces. The greatest structural inhomogeneity of the finer grain is observed in the places of growth (jointing) of second and third orders dendritic branches. Also, with a slight deformation of 45 grade steel, there is no connection between the formation of the final structure with non-metallic inclusions. It has been shown that in continuously-cast stocks with developed dendritic and zonal segregation, structural features are preserved in normal rolled products and affect the strength of steel.

Keywords

• structurization
• tubular billet
• segregation
• mechanical properties.