Boron removal from molten silicon using CaO-SiO2-BaO-CaF2 slag
(1. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China;
2. TDK Dalian Corporation, Dalian 116024, China)
2. TDK Dalian Corporation, Dalian 116024, China)
Abstract: The distribution coefficient (LB) of boron between CaO-SiO2-BaO-CaF2 slag and silicon was investigated using electromagnetic induction melting for the purpose of improving the boron removal fraction. The dependence of the boron distribution coefficient between slag and silicon on the fundamental parameters of CaO to SiO2 mass ratio and refining time and the additions of BaO and CaF2 to the slag was discussed. The results show that LB can be increased by adding BaO and CaF2 to CaO-SiO2 slag. The maximum value of LB (6.94) is obtained when the CaO to SiO2 mass ratio is 1.1:1 and the contents of BaO and CaF2 are fixed at 15% and 20%, respectively. Increasing the refining time increases the LB. After the slag treatment is performed twice, the boron content of the silicon is successfully reduced from 3.5×10-5 to 3.7×10-6, and the removal fraction of boron reaches 89.4%.
Key words: metallurgical silicon; boron removal; CaO-SiO2-BaO-CaF2