Complex analysis of the influence of impurity and alloying elements on the toughness of steels for the manufacture of railway axles

Abstract

The paper presents and summarizes the results of statistical analysis of industrial data on chemical composition and mechanical properties of more than 1,500 samples taken from rough railway axles made of steel grades OS and EA1N with different degrees of deformation. The analysis was performed using the parametric Student's t-test, which allows to assess the statistical significance of differences between the compared values, namely, the greater the value of the t-test, the more statistically significant differences between the compared values. A significant reserve for improving the structure and properties of axial steel is the adjustment of the chemical composition, even within the vintage composition, which will minimize the cost of additional heat treatment of steel in the manufacture of railway axles. The difference between the chemical composition of steel for railway axles and the level of impact strength, in particular manganese and sulfur, has been determined. Manganese, although a strengthening element, promotes the growth of austenite grains and enhances carbon sequestration, which leads to uneven distribution of structural components of ferrite and perlite, especially with increasing its amount and insufficient deformation. This is due to the positive effect of sulfur on toughness. Although sulfur is an element that significantly reduces the properties of steel, but in this case, its content is likely to reduce the liquation of manganese. As the temperature in the austenitic region decreases, Mn is concentrated more in the nonmetallic MnS inclusion, thereby reducing its concentration around the inclusion. The necessity of applying a greater degree of deformation of the original continuously cast steel billets of EA1N grade and the implementation of measures that will have a positive effect on the reduction of dendritic segregation is shown. The significant influence of steel production technology for railway axles of close chemical composition is emphasized.