Direct Alloying of Silicon in Liquid Steel by Molten Slag Electrolysis

Abstract

The present study aimed at completing the direct alloying operations of Si in liquid steel by the way of electrochemical method. In the traditional steelmaking process, the ferrosilicon is prepared by preliminary smelting the oxide ores, and then added into the liquid steel for alloying. In this study, the direct alloying operations will be completed by electrolyzing CaO–SiO₂–Al₂O₃ molten slags, in which process the alloy elements are produced in the slag-steel interface and then diffuse into the liquid steel when direct current pass through the two electrodes which are placed in liquid steel (cathode) and slag (anode), respectively. It is a new attempt to applying the electrochemistry on the steelmaking process. Experimental results showed that after electrolysis for 2 hours, as applying larger current and using slag with a higher content of SiO₂, there will be a higher content of Si generated in the liquid steel. It was found that during the electrolysis process, Al content in the steel also slightly increases, while there was no obvious change of Ca content. Meanwhile, reduction of Al₂O₃ and CaO is not the main factor to decrease current efficiency (calculated by the ratio of generated Si in liquid steel to the theoretical silicon by Faraday law).