Effect of Superheat, Cooling Rate, and Refractory Composition on the Formation of Non-metallic Inclusions in Non-oriented Electrical Steels

The magnetic properties of electrical steels are improved with additions of silicon and aluminum; however, these elements also promote the formation of non-metallic inclusions. The presence of non-metallic inclusions in electrical steels severely affects its magnetic properties. In this work, the effect of cooling rate, superheat, and refractory composition on the formation of non-metallic inclusions has been investigated. The evolution in chemical composition has been reported using a new representation employing pseudo-quinary phase diagrams. It has been found that the concentration of MnO in the non-metallic inclusions plays a big role to control its population density. A critical value has been identified above which it is possible to achieve a large decrease in the total number of non-metallic inclusions in electrical steels, in addition to this, it was also possible to define the influence of cooling rate, superheat, and refractory chemical composition on the composition and population density of non-metallic inclusions. It was found that increasing cooling rate and a change of crucible from alumina-based to MgO-based, both increase the population density of NMI, on the contrary, superheat decreases the population density, depending on the concentration of MnO in the inclusions.