Effects of calcium treatment on non-metallic inclusions and magnetic properties of non-oriented silicon steel sheets

Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied.The thermodynamics of CaS inclusion formation was analyzed,and the morphology and the size distribution were observed.Furthermore,the change in inclusion characteristics after calcium treatment and the effect of calcium treatment on magnetic properties were discussed.The results show that the formation of MnS and AlN inclusions were restrained,and the aggregating,floating and removing of microinclusions after calcium treatment were effectively promoted.The cleanliness of liquid steel was obviously increased.The main type of inclusions was single phase of CaO,with some complex inclusions composed of CaO,SiO2 and MgO.No CaS inclusion was observed after an appropriate calcium treatment.The size of all inclusions was distributed in the range of 2-20 μm,and the number was about 1.8×105 /mm3.In addition,as an increasing amount of calcium was added,the core loss gradually decreased to a stable level,and the magnetic induction decreased quickly after a slow increase.The optimal calcium treatment mode depends on the chemical composition of steel.