Analysis of Inclusions in U75V Heavy Rail Steel

Manganese sulfide inclusions are more common in heavy rail steel, and it is very important to control the sulfide in heavy rail steel. In this paper, an optical microscope, scanning electron microscope, etc., are used to construct a three-dimensional model analysis of inclusions in U75V rail, and the precipitation law of MnS is obtained by combining Thermo-calc software and the growth coupling prediction model. The results show that the inclusion types in the U75V rail are mainly composite inclusions with magnesia-alumina spinel as the core and MnS on the periphery. The inclusions are elongated along the rolling direction, and the inclusions at the rail head and rail bottom are more slender, with an average aspect ratio of 9.10 and 7.48, while the inclusions at the rail waist are relatively flat, with an average aspect ratio of 5.92. Considering the precipitation of inclusions and the segregation of solute elements, it is found that MnS precipitates when the concentration product of Mn and S exceeds the equilibrium value, and reducing the S content is a reasonable choice to prevent the precipitation and growth of MnS.