Development of technological solutions to improve the quality of railway rails by improving the technology of smelting, out-of-furnace processing and continuous casting of rail electric steel.

Abstract

Based on a complex of metallographic and X-ray phase studies for the conditions of EVRAZ ZSMK, which is a leading domestic manufacturer of railway rails, the nature of characteristic defects of rails of metallurgical origin has been determined. These defects, which are the cause of rejection of rails during ultrasonic quality control in the flow of rail-block mill, are stratifications, in the localities of which accumulations of silicate, alumina and sulfide non-metallic inclusions are concentrated; at the same time, these defects in the vast majority of cases are located in the neck of the rail profiles. Analysis of contamination with non-metallic inclusions of suitable rails of the current production of EVRAZ ZSMK showed that, unlike the locations of defects in rejected rails, alumina non-metallic inclusions have an extremely low concentration, while manganese sulfides and silicate inclusions have the highest relative concentration. Based on the results obtained, technological measures were developed, pilot-industrial and implemented to improve the production technology of rail steel in the conditions of the electric steelmaking workshop of EVRAZ ZSMK. In order to reduce the concentration of oxide nonmetallic inclusions in rail steel, a new technology of ladle treatment of steel using a low-ash carburizer and calcium carbide for slag deoxidation has been developed. To reduce sulfide inclusions contamination, measures have been implemented to ensure the sulfur content in the finished steel at a level of no more than 0.008%. The optimization of the modes of electromagnetic mixing in the mold and the temperature regimes of continuous casting of steel was carried out, which also had an effect on reducing the concentration of non-metallic inclusions in continuously cast billets of rail steel and finished rails. The introduction of a set of these technological solutions and measures allowed to reduce the rejection of rails for internal defects from 7% to less than 2%