Justification and development of effective modes of inert gas purging of rail steel during ladle treatment

The complex of studies carried out in order to substantiate the directions for improving the modes of purging rail steel with inert gas in a ladle in relation to the conditions of steel treatment in the operating ladle furnace of an industrial electric steel workshop includes mathematical modeling and statistical analysis. According to the research results, a significant effect of increasing the intensity of argon injection through bottom porous plugs in a wide range of changes in this parameter (from 2 to 85 m³/h) was established on an increase in indicators characterizing the efficiency of mixing and refining steel from non-metallic inclusions (mixing power and effective diffusion coefficient). The authors, in relation to the rails of the studied enterprise current production, using optical and electron microscopy techniques, determined that at low contamination of the rails bulk with non-metallic inclusions at individual heats, inclusions accumulate, which are the causes of the internal defects formation and rejection of rails during ultrasonic quality control in the production stream. Based on the results obtained, a new method for purging rail steel was developed with a dedicated period of intensive purging lasting about 20 % of the total argon purging time. Pilot testing of the developed purging mode on a series of 76KhF rail steel heats of current production (115 heats) showed a significant (by 0.31 abs. % or 11 rel. %) reduction of rail rejection by non-metallic inclusions relative to the comparison base. The additional metallographic studies confirmed the reduction of contamination with non-metallic inclusions of rails made of steel treated with a new argon purging mode in a ladle. 

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