Effect of calcium treatment on magnetic properties of non-oriented electrical steels

The effect of calcium treatment on magnetic properties of non-oriented electrical steels was studied. Inclusions, precipitates, grain size and textures of final annealed sheets were analyzed and their effects on magnetic properties of the steel were discussed. Inclusions varied from Al2O3-MnS to Al2O3-CaS-(CaO) due to the reaction of calcium and sulfur after calcium treatment. The number density of (Mn, Cu)S precipitates decreased with the increasing Ca/S in the steel, which also favored to the grain growth of final products. Both of the texture factors of {100}/{111} and ({100}+{110})/{111} were increased from 0.22 and 0.34 to 0.37 and 0.50, respectively, due to the increase of the volume fraction of {100} from 8.34% to 15.80% with the increasing Ca/S from 0 to 1. The core loss decreased by 0.25 W/kg with Ca/S increasing from 0 to 1 in the steel, due to less (Mn, Cu) S precipitates and larger grain size. However, the increase in the number density of Al2O3-CaS-(CaO) inclusions caused by calcium treatment increased the volume fraction of {111} fiber textures, having a detrimental effect on the magnetic induction of the steel. Therefore, in order to improve the steel magnetic properties, inclusions of Al2O3-CaS-(CaO) formed after calcium treatment should be removed as much as possible.