Microstructure And Texture Evolution Of Secondary Recrystallization In High Silicon Steel Thin Sheets

High silicon steel containing 6.5wt%Si has excellent magnetic properties:high permeability,higher resistivity,near zero magnetostriction and lower magnetic anisotropy,result in low noise,low core lose.Therefore,it is favorable to used as motor cores,high-frequency transformers and magnetic shielding materials.Recrystallization texture is one of the key factors affecting the magnetic properties,by means of abnormal grain growth of Goss grains the soft magnetic properties were improved drastically in conventional grain oriented silicon steel.Currently,grain-oriented high silicon steel sheets are still far more from large-scale production.In this study,the 0.25mm thin sheets were finally fabricated through the two-stage cold rolling process,and strong recrystallization η fiber(<100>//RD,Rolling Direction)was achieved after final annealing.NbC was selected as the inhibitor,and the texture evolution of the process was analyzed by X ray diffraction and electron back scatter diffraction(EBSD).(1)The microstructure of hot bands is characterized by deformed grains and no obvious dynamic recrystallization occurred during hot rolling process.The texture of first stage cold rolled bands is characterized by texture gradient through thickness,with strong a and y fiber in the subsurface layer and strong a fiber in the center layer.Shear bands widely distributed in the matrix of the second stage stage cold rolled samples,the final cold rolling texture is consisted of y fiber with the peak at{111}<112>,which is considered to be benefit to the nucleation and growth of ηgrains during the annealing process.(2)The primary grain size is between 15μm and 20μm,the primary recrystallization texture is composed of η and γ fiber(<111>//ND,Normal Direction).Secondary recrystallization occurred in the sheets with different NbC content,the oneset temperature is about 920℃ and the orientation of abnormal grains belong to<001>//RD fiber.(3)The abnormal grain growth of η grains is closely related to the primary recrystallization microstructure and texture:numerous primary η grains ensured adaquate secondary nucleis in the primary recrystallization matrix,and the effective pinning of NbC particles promoted the abnormal growth of secondary nucleus.(4)The size of abnormal grains reached mm scale after secondary recrystallization,however,the secondary recrystallization process is not so much perfect and a number of residual fine grains exist.The reason possibly may be attributed to the lack of inhibition ability of sole inhibiter NbC under high temperature.Complete secondary recrystallization can be achieved by means of introduction of multiple inhibiters in the future.