BEHAVIORS AND EVOLUTIONS OF MgO-Al_2O_3 IN NON-ORIENTED SILICON STEEL DURING CALCIUM TREATMENT

摘要

Behaviors and evolutions of MgO-Al_2O_3 in non-oriented silicon steel during calcium treatment were investigated by thermodynamic calculations and high-temperature experiments. MgO Al_2O_3 inclusions were the main type of inclusions before calcium treatment, which is also confirmed by the stability diagram of MgO/MgO- Al_2O_3/Al_2O_3 from thermodynamic calculations. After calcium treatment, the majority of original MgO-Al_2O_3 inclusions were mainly modified to CaO-MgO-Al_2O_3 system inclusions, this would be beneficial to improve castability and product quality of silicon steel. But there was no modification happening to some MgO- Al_2O_3 spinels which were directly surrounded by CaS inclusions. The content of Al_2O_3 occasionally existed a sudden increase besides a common decrease in the product layer of CaO-MgO-Al_2O_3. Then the evolution mechanisms of MgO-Al_2O_3 inclusions were proposed in present work. Thus, Al/Mg atom ratio had a significant influence on the modification of MgO-Al_2O_3 spinel.