Effect of annealing on microstructure, texture and magnetic properties of Fe-6.5 wt%Si-0.03 wt%Nb alloy

Abstract

Fe-6.5 wt% Si alloy (high silicon electrical steel) is an ideal core material for making motors and transformers with low noise and low power loss. Controlling microstructure and texture is key to improving the magnetic properties of high silicon electrical steel. In order to improve the warm rolling and cold rolling workability of high silicon electrical steel, in this paper, 0.03 wt% Nb is added to the alloy, and a strip sample with a thickness of 0.13 mm was prepared. The effect of annealing temperature on microstructure, texture and magnetic properties of the samples was studied. The results show that annealing at 800 ℃–1300 ℃ for 1 h, with the increase of annealing temperature, the {1 0 0} texture content of the sample decreased from 9.47% to 1.09%, {1 1 0} texture content gradually increased from 1.26% to 33.1%, {1 0 0}+{1 1 0} texture content increased significantly from 10.73% to 34.19%. Nb-rich precipitates are formed in high silicon electrical steel with a size of about 100 nm. When the annealing temperature is lower than 1200 ℃, the Nb-rich precipitates can inhibit the grain growth. When the annealing temperature is higher than 1200℃, the Nb-rich precipitates dissolves and the pinning force to the grain boundary is weakened. The 0.13 mm Nb-microalloyed high silicon electrical steel strip has good magnetic properties at 800–1300 °C for 1 h. At 1200 °C, the grain growth and iron loss decrease due to the dissolution of the Nb-rich precipitates, so that the sample has a high comprehensive magnetic property: B8 is 1.31 T, B50 is 1.61 T, and P10/50 is 0.411 W/kg, P10/400 is 5.416 W/kg.