Numerical Simulation Of Protection Gas In Electroslag Remelting Process And Optimization Of The Protective Cover

Electroslag remelting (ESR), which has excellent metallurgical reaction conditions and unique solidification crystallization process, can effectively remove the harmful inclusions in metal and improve the quality of the metal solidification. However, hydrogen, oxygen and other harmful gases can not be effectively removed from steel when large ingots are produced limited by the equipment. At present, the structure of protective cover of large ESR furnace is so simple that a mass of protective gas is consumed and it is difficult to control hydrogen and oxygen content at a low level. Therefore, it is significant to design a protective cover with reasonable structure in order to improve ingot quality and decrease the production cost.In this paper, different hydrogen and oxygen contents of steel in ESR process under the atmosphere and protective gas were studied by high-temperature experiments. The result showed that protection atmosphere could effectively prevent the increase of hydrogen and oxygen contents in ESR steel.Based on the basic theory of computational fluid dynamics(CFD), basic equations of the mathematical model were established, which are discreted into three-dimensional steady discrete equations. According to the characteristics of the gas flow in electroslag furnace, Realizable k-ε two-equation model and the wall function were introduced. The wall function was used to solve the problem of the flow near the wall. Based on FLUENT software, the mathematical model of flow and heat transfer of the protective gas in large electroslag furnace was established.The affect of protective cover structure on the protective gas flow field was investigated and the relationship was obtained through simulation analysis of the gas and temperature field in the eletroslag furnace. With the decrease of outlet section size, the pressure in electroslag furnace and in protective cover increases; With the decrease of inlet aperture, the pressure gradient below protective cover and the negative pressure area increases, and the pressure distribution becomes more and more asymmetry. Based on the effect of protective cover structure on protective gas flow filed in furnace, the structure of protective cover was optimized and designed.By numerical simulation of flow and temperature field of protective gas in electroslag furnace on different outlet pressure and different flow parameters, reasonable outlet pressure was confirmed; and the relationship between the depth of slag surface and protective gas supplying was confirmed, which provided theoretic directions for setting of gas supplying parameters in producing process.