Formation of the macrostructure depending on the city and the ratio of the main components in railway steel ingots

Abstract

The purpose of the work is to establish the influence of the basic elements of the chemical composition of steel for railway axles on the features of the formation of the primary structure. The problem of macrosegregation of alloying elements, which occurs during the solidification of a cast billet during continuous casting, remains relevant; it is the subject of countless experiments and theoretical judgments. A large percentage of these studies are devoted to carbon segregation, which is understandably highly relevant for the production of carbon steels. The relationship of processing, microstructure and properties indicates that the morphology and properties of the various phases at the microscopic level are largely closely related to the macroscopic behavior of materials. Basic knowledge about the mechanism of segregation shows that this is a very complex effect and it is necessary to take into account a wide range of factors that affect the continuous casting process. Due to the limited solubility of individual elements in the crystal lattice of steel, during the solidification of the melt, the residual liquid is enriched, resulting in the formation of micro- and macrosegregations (segregations, heterogeneities). The aim of the work is to reveal the influence of chemical elements on the formation of reverse segregation. As part of this work, pilot batches of steel samples were made and analyzed, which are used for the manufacture of railway axles - steel grades OS according to DSTU 31334, F according to AAR M 101 and EA1N according to EN 13261. Separate emphasis was placed on the ratio of content in steel Si and Mn. The formation of the so-called "reverse segregation" zone, observed in the studied ingots, is most likely due to the contamination and gas contamination of steel. The nature of the formation of this zone coincides with the features of the formation of places of contact between the branches of higher-order dendrites. It is established that the presence of structural heterogeneity reduces the mechanical properties. It has been shown for the first time that an increase in the ratio of Mn to Si content in axial steels of the EA1N, OC, and F grades contributes to an increase in the gas saturation of the steel and the appearance of anomalous structures.