Effect of slab reheating temperature on recrystallization microstructure, texture and magnetic properties of Nb-containing grain-oriented silicon steel

Abstract

In this study, a Nb-containing grain-oriented silicon steel was chosen to investigate the effect of different slab reheating temperatures on the microstructure and texture of primary recrystallization and secondary recrystallization by optical microscope (OM), field emission scanning electron microscope (FE-SEM) equipped with electron backscatter diffraction (EBSD) system and transmission electron microscope (TEM). The magnetic properties of finished product were also measured. The results show that Nb(C,N) can be formed and worked as the main inhibitor after adding Nb into the traditional grain-oriented silicon steel to lower the reheating temperature of the slab. At different low slab reheating temperatures, primary recrystallization takes place in all decarburized specimens, and at 1220°C, the microstructure is the most fine and uniform. The types of primary recrystallization texture are consistent composed of strong {411}〈148〉 texture, dominated γ-fiber texture {111}〈112〉 and {111}〈110〉, weak α-fiber texture and some Goss components. The proportions of HEGB and Σ9 boundary are the highest at 1220°C after decarburization annealing, which is beneficial to the grain growth of primary recrystallization. After high temperature annealing, the specimen of 1220°C slab reheating temperature can be fully recrystallized to obtain secondary recrystallization grains on the centimeter scale, and the texture component is characterized by a single Goss texture. The magnetic properties of finished product are the best, and B800=1.88T, P1.7/50=1.31W/kg.