Original Article

Non-uniform distribution of the cleanliness in a high manganese steel rail

¹ School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, PR China
² College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, PR China

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Received: 25 July 2025
Accepted: 29 October 2025

Abstract

In the current study, the distribution of non-metallic inclusions and characteristics of steel cleanliness in the vertical direction of a high manganese steel rail were evaluated. Inclusions in high manganese steel rails were mainly Mg-Al-Ca-O and Al-Ca-O inclusions enveloped with precipitated MnS during steel solidification and cooling. The average composition of oxide inclusions was 63.61% Al₂O₃, 17.82% CaO, 8.09% MgO, 8.92% MnO and 1.55% SiO₂. The distribution and quantity of inclusions along the height of the rail were relatively non-uniform, with smaller inclusions near the rail head top, primarily averaging 4.3 µm in diameter. Thermodynamic calculations were performed using the FactSage software to predict the composition of inclusions in the steel. As the aluminum content in the steel increased, liquid inclusions were transform into solid phases of CaO · 2Al₂O₃ and CaO · 6Al₂O₃. The CaO content in inclusions steadily increased with the increase of the calcium content in the steel. When the calcium content exceeded 5.66 ppm, liquid inclusions were transformed into CaO · 2Al₂O₃. In the Ca-Al and Si-Ca binary equilibrium phase diagram, the phase Ca₂SiO₄ stably existed, and as the oxygen content decreased, the stable zone of Ca₂SiO₄ gradually shrank, agreeing well with the measurement. As solidification progressed,with the increase of the T.Ca content in the steel, the Al₂O₃ content in inclusions decreased while the contents of CaO, CaS, and SiO₂ inclusions gradually increased.