Effect of annealing process on recrystallization behavior of non-oriented silicon steel with Nb-rich for new energy vehicles

Abstract

Baiyun Ebo ore in Inner Mongolia in China is an associated ore rich in RE, Nb, Ti and other elements, which still have trace residues after smelting. In order to promote the comprehensive utilization of superior mineral resources and give full play to the role of these alloying elements in steel, the microstructure, texture and precipitates evolution of non-oriented silicon steel containing Nb were studied in different annealing processes in this research. The results show that when the non-oriented silicon steel containing Nb is annealed at 850°C, with the extension of annealing time, the recrystallized grains preferably nucleate and grow in the deformation band and grain boundary on the surface of the annealing plate. When the holding time is 3 min, the recrystallization proportion is about 20%. When the holding time reaches 9 minutes, recrystallization occurs completely, and the final recrystallization texture is mainly {111}<112> orientation. The precipitates of the steel is mainly Fe16Nb6Si7 after annealing, the particle size can reach 100 nm. When annealed at 850°C, the volume fraction of Fe16Nb6Si7 phase decreases with the increase of annealing time, from 0.03236% to 0.01036%. When annealed at 850 °C for 3 min, the strength of the second phase increases to 9.4 MPa, and when the annealing time reaches 9 min, the strength of the second phase increases to 3.88 MPa. Therefore, when annealed at 850 °C, the precipitation of Fe16Nb6Si7 particles has little effect on the intensity increment. In the design of annealing process, the Nb-rich phase should be solid dissolved into the matrix as much as possible, on one hand, the adverse effects of particles on magnetic induction and iron loss are reduced, on the other hand, the strength of non-oriented silicon steel can be improved by solid solution strengthening.