Optimization of production technologyof continuous cast rail steel for increasing its purity by non-metallic inclusions

The purpose of the work was to examine the reasons for formation of non-deformable non-metallic inclusions in rail steel and ways to reduce the rejection of finished rails due to the defects revealed during ultrasonic testing. The study was conducted at the steelmaking plant of JSC “Ural Steel”. In the central laboratory of the combine, a chemical analysis of non-metallic inclusions was carried out in the samples of finished rails produced from blanks manufactured by JSC “Ural Steel” and rejected at the ultrasonic test unit during the rail production at the “Aktobe Rail and Section Works” LLP. Non-metallic inclusions by their composition are represented by aluminium oxides. The most probable reasons for their formation have been determined as following: the use of aluminium containing ferroalloys and interaction of the melt components with refractory materials and casting powder. The authors made analysis of the ferroalloys used in production of rail steel. Industrial trials of the manufacturing process of continuously cast blanks from rail steel were carried out, where FS65 ferrosilicon, which contains aluminium, was replaced with silicon carbide. An increasing degree of silicon and carbon recovery in trial heats was noted. Evaluation of contamination with non-metallic inclusions and mechanical properties of the rail steel manufactured using the experimental technology showed that the service characteristics of the rail steel meet requirements of the state standard GOST R 51685 – 2013. The full-scale experiment has confirmed that the technology of alloying E76F rail steel with silicon carbide at JSC “Ural Steel” is technically feasible. The yield of 100-meter rails was increased by 17 % on a trial batch produced from JSC “Ural Steel” continuously cast blanks.