Effect of Oxide Shape on Magnetic Properties of Semiprocessed Nonoriented Electrical Steel Sheets

The effect of oxide shape on magnetic properties of semiprocessed nonoriented electrical steel sheets produced by single reduction cold rolling process was studied. When oxides in steel sheets were elongated inclusions which were prescribed as B type by JIS, the oxides inhibited grain growth during consumer annealing and average grain size became small. As a result, core loss was bad. When oxides were spherical inclusions which were prescribed as C type by JIS, the oxides did not inhibit grain growth and average grain size became large. As a result, core loss was good. Oxide composition affected the shape remarkably. The degree of elongation of oxides had much to do with the viscosity during hot rolling. The viscosity of oxides containing less MnO and much SiO2 was high, and the degree of elongation was small. Consequently, these oxides became spherical C type inclusions.