Effect of Li ₂O addition on crystallization behavior of CaO-Al ₂O ₃-MgO based inclusions

The crystallization behavior of CaO-Al ₂O ₃-MgO oxide powder which is one of the major non-metallic inclusions in Al-killed steel was systematically examined in the present study. 33mass%CaO-62mass% Al ₂O ₃-5mass%MgO and 30mass%CaO-57mass% Al ₂O ₃-5mass%MgO-8mass%Li ₂O glass powders were heat-treated at 1 073-1 673 K for 8-512 s under air. CaO-Al ₂O ₃-MgO glass was found to be crystallized immediately after the heat treatments. Moreover, it was revealed that the addition of Li ₂O accelerated the crystallization of the glass powders, and controlled aggregation of crystal particles. Additionally, the indentation hardness of crystallized glasses after 512 s heat-treatments was investigated by using a nano-indenter. The addition of Li ₂O had the effect of lowering the hardness of samples, which indicates that Li ₂O would improve the deformation behavior of aluminate based inclusions.