This article presents the effect of multifunctional modification on reducing the content of harmful impurities, stabilizing the chemical composition, and improving the morphology of non-metallic inclusions. As determined, modifier elements increase the level of mechanical characteristics of КП-Т wheel steel used in railway vehicles in Ukraine and other countries. The results of the influence of modifier elements on the total activity of harmful impurities of sulphur and phosphorus are presented. The thermodynamic characteristics of compounds formed under the influence of multifunctional modifiers on the melt are given. As shown, during modification, crystallization centres are formed due to the interaction of special multicomponent deoxidizers-modifiers with steel melt. They are quite evenly distributed in the bulk of the metal due to the special physical and chemical properties, the composition of modifier-deoxidizers, the constancy of their geometric shape and mass. Studies of the structures of serial and modified with multifunctional modifier steel КП-Т are carried out. As established, in unmodified serial steel of this grade, excess ferrite (about 5–7%) is released outside the former austenite grains, which decorates them. As determined, due to the action of modifier elements in the modified steel, highly dispersed fine-grained pearlite is formed with single ferrite precipitates outside the grains in the modified steel of the КП-Т grade. As proved, modifiers improve the mechanical characteristics of КП-Т grade steel. This is because, during the curing of the modified ingot, mainly volumetric, rather than oriented, heat-removing crystallization takes place, as for serial metal. As proved, after modification, the morphology of non-metallic inclusions is significantly improved. As determined, thanks to the modifier elements, this problem is levelled, since, due to them, the globulization of non-metallic inclusions occurs. As a result, the quality of finished wheels is significantly improved.