The study of the structure and mechanical properties of T and K + Al + N + Ti steels after casting and hot plastic deformation (HPD)

Abstract

Purpose. To perform comparative studies of structural features and mechanical properties of test steel for railway wheels with microalloy complex Al + N + Ti and known steel for high-strength railway wheels of brand T, microalloyed with vanadium.
 Methodology. Microstructural, micro-X-ray spectral and X-ray phase analyzes were used to determine the structural state of the alloys.
 Results. Comparative analysis of the structure and mechanical properties of steels for high-strength railway wheels of brand T and K + Al + N + Ti. It is shown that in K + Al + N + Ti steel after crystallization the structure becomes finer-grained and increase in the volume fraction of perlite was observed in comparison with steel of T brand. It was found that the HPD leads to the decrease in the volume fraction and size of oxides, and in aluminum oxides Al2O3 there is a partial replacement of aluminum atoms by iron and titanium atoms.
 Originality. It is shown that the reduction of vanadium content in steel and complex alloying with aluminum, titanium and nitrogen leads to the formation of the finer-grained structure and increase in the volume fraction of fine perlite. In the microstructure of K + Al + N + Ti steel, the formation of oxides, nitrides and carbonitrides was observed, which were located along the grain boundaries and in the body of the perlite grain.
 It was shown for the first time that HPD leads to the fact that in the inclusions of aluminum oxides Al2 O3 the partial replacement of aluminum atoms by atoms of iron or titanium, with the formation of oxides of Fe2(Al)O3 and (Al, Ti)2O 3, take place.
 Practical value. The use of complex alloying of steel leads to improvement of mechanical properties: increase in toughness at the high level of hardness and strength of steel grade K + Al + N + Ti in comparison with steel of brand T.