Investigation of Chemical Heterogeneity of Cast Metal Ingots of Different Geometries and Assessment of their Applicability for Producing Round Rolled Products

Abstract

Based on the study results, it is shown that the selected ingot geometry makes it possible to obtain a solidified metal structure with a favorable distribution of physical and chemical heterogeneities of the cast metal. The temperature profile calculations have shown that 1 h 45 min after the onset of solidification of a big-end-down ingot, the advancing crystallization front closes, and an extended “closed” zone of liquid metal is formed, the height of which reaches 37% of the height of the ingot body. The provided data correlated well with the actual shrinkage defects, the length of which constituted 36% of the height of the ingot body. The comparison of the temperature distribution profiles with the assessment of steel contamination with non-metallic inclusions and specifics of segregating impurity distribution has revealed a more uniform distribution of impurities and nonmetallic inclusions due to intensive advancement of the solid phase under the hot-top part of the ingot. In this case, the optimized thermal performance of the hot top helps move segregating impurities and tertiary inclusions to the ingot head. The assessment of applicability of the big-end-up and big-end-down ingots has demonstrated the feasibility of using the former to produce round rolled products with a diameter in excess of 250 mm. The big-end-down ingot weighing 5.9 ton is feasible to use for the production of rolled products having a diameter not exceeding 200 mm due to the formation of a closed secondary pipe cavity. The use of a low hot-top height big-end-down ingot allows increasing the yield of the usable metal, while improving the quality of the rolled products.