Effect Of Normalization On The Microstructure Evolution Of The Electrical Steel In Annealing Process

Because of its high strength,high fatigue strength,high magnetic induction,low high frequency core loss and other properties,non-oriented silicon steel has become the key material for manufacturing high-efficiency drive motor core of new energy vehicles.In order to further purify the inclusions,improve the magnetic properties,reduce the iron loss,increase the grain size of the finished plate and improve the properties,researchers often add a certain amount of rare earth to the non-oriented silicon steel.This change in composition brings new characteristics to the transformation of texture and precipitate of this special material in the whole production process.However,the relevant research is not perfect.Therefore,in this paper,the effect of normalization process on the evolution of precipitate,microstructure and texture in the subsequent annealing process of hot-rolled non oriented silicon steel plate containing trace cerium was studied by means of OM,TEM and XRD.The results show that the average grain size of the normalized plate increases significantly when the holding time is increased from 1min to 5min,and the microstructure of the finished plate with the same annealing time under different normalization processes also increases significantly.Texture: after hot rolling,the main texture is brass texture and copper texture with a certain amount of A-line texture;after normalization,the texture strength of the sample is not high,and the loss of a-linear texture copper texture and brass texture strength are attenuated.After cold rolling,the main texture types are α-and γ-linear texture,and then the α-and γ-linear texture in the decarburized annealed plate is obviously weakened.Compared with 5min,the normalized holding time for 1min in the finished board can improve the η texture strength of the magnetic induction,and reduce the {111} <110> and {112} <110> texture strength of the negative magnetic induction.In high-temperature annealing,the linear texture of α and γ changes little with the holding time,while the strength of η orientation line which is beneficial to magnetic induction decreases with the holding time of high-temperature annealing increasing.Therefore,the time should be shortened when normalizing at 1000 ℃,and the texture beneficial to magnetic properties can be improved by choosing short-time low-temperature annealing after high-temperature annealing,and the unfavorable texture grains such as {112} <110> can be restrained.In the aspect of precipitates,when annealed at 850 ℃,with the prolongation of holding time,there are not only new(Nb,Ti)C precipitates in annealed plates,but also the original precipitates are coarsened;when normalized at 1000 ℃,the time should be shortened,which is conducive to the inhibition of grain growth in finished plates and the prevention of abnormal growth.In the subsequent high-temperature annealing,short-time low-temperature annealing can effectively inhibit the {112} <110> and other unfavorable texture strength.