Pavlov S. Development of resource-efficient technology of the treatment of steel in the ladle furnace based on the rationale locations of purge plugs

The process of steel treatment in the ladle furnace. The scientific substantiation of the resource-efficient technology of the treatment of steel in the ladle furnace based on the rationale locations of purge plugs in the steel ladle, which provides decreasing of consumption of argon and electricity; increase of refractory lining performance; improvement of the quality of continuous and processing billets due to chemical and structural heterogeneity, content and distribution of non-metal inclusions is presented. Modern methods of statistical data processing, advanced numerical simulation methods, calculation and analytical estimation and providing of industrial experiments are used in this paper. It was established that the share of electricity consumed to compensate for the thermal losses of the steel pool during argon purging is 68.8% - 72.8%. The tendencies of increase of electricity consumption with increasing the duration of the treatment of steel in the ladle furnace due to cooling of the melt from 0.5 to 1.75 degrees/min are presented. The new reliable information about hydrodynamic and heat transfer processes, which accompany the treatment of steel in the ladle furnace while stiring the melt with an inert gas through the purging plugs was obtained. The research of the processes in the steel pool has determined the possibility of increasing the mixing efficiency due to the change in the location of the purging plugs, compared with the nominal layout. It is determined for investigated variants of distance of purging plugs from the center of the bottom of the ladle (0.5RDn - 0.7RDn) that the most effective stirring is achieved for such variants of the purge plugs location, in which the angle between them is 80-100 degrees. The location of purging plugs with the angles within these limits reduces the duration of the mixing of the metal in the ladle by 4 - 15% and reduces the volume of stagnant zones to 16% relative. It has been established that the upper limit of argon consumption at the level of stabilization of flow's speed and the duration of homogenization of the melt for the investigated variants of the location of two purging plugs corresponds to argon consumption in the range of 800 - 1000 l/min on the ladle. On the basis of the obtained theoretical results, the technology of the treatment of steel in the ladle furnace was developed and in the conditions of PJSC "Dniprovsky Iron & Steel Integrated Works", which is characterized by asymmetric distance of two purging plugs from the center of the ladle bottom, by the establishment of two periods of purging with argon with the observance of its total consumption in periods according to the ratio Q2 = 0,5Q1 and providing the same ratio for each plug. Using such technology will reduce the consumption of argon by 18.4% and electricity by 3.8%, increase the resistance of the refractory lining in the campaign by 10.7 - 18.9%, improve structural homogeneity and reduce nonmetallic inclusions from 2.5 - 3.5 to 1.5 - 2.0 points. The results of the research presented in the dissertation paper are recommended for further use at metallurgical plants of Ukraine to clarify the layout parameters of the location of purge plugs in steel ladle, technological purging modes and electric arc heating at ladle furnace in order to reduce the consumption of material and energy resources.