Effect of Niobium on Microstructure Evolution and Behaviors of Second Phase Particles of the Reheated As-cast Grain-oriented Silicon Steel

The grain oriented silicon steels with different Nb contents were prepared,and the effect of niobium on the microstructure evolution and the behaviors of second phase particles of the as-cast grain-oriented silicon steel during reheating process was studied by high-temperature confocal laser-scanning microscope（HTCLSM） and Nova 400 Nano field emission scanning electron microscope（FE-SEM）.The results show that the inclusions in all as-cast specimens are mainly complex inclusions,which takes Al₂O₃ as its core.During the cooling stage,MnS mainly precipitates in the first precipitation stage,and Nb（C,N） also precipitates in the Nb-containg specimens.And the volume fraction of the second phase particles in the first precipitation stage can be effectively increased by adding Nb,which will effectively enhance the pinning ability of the second phase particles.However,niobium has little effect on the behaviors of precipitation of AlN.Meanwhile,the homogeneity of microstructure of reheated specimens can be improved by adding Nb.