Study On Microstructure,Texture And Precipitation Of Ultra-low Carbon Oriented Silicon Steel

In this thesis,the production process of a new type of inhibitor of ultra-low carbon oriented silicon steel was studied.The evolution of microstructure,texture,precipitates and secondary recrystallization and magnetic properties under different cold rolling and intermediate annealing process was studied by means of electron microscope,EBSD and TEM.The results show that:(1)The surface of the ultra-low carbon oriented silicon steel hot-rolled sheets is fine equiaxed grains,the subsurface is a mixed zone of partially elongated deformed grains and fine equiaxed grains,the central layer is elongated deformed structure;the texture of the surface layer is Goss component,the central is a component.Precipitates are mainly MnS,NbN and its composite precipitation,and the average size is small.Normaling of hot-rolled sheets of the organization,texture is less affected,with the normalization temperature increases,the surface density increases and the average size first increases and then decreases.(2)The one-stage cold-rolling sheets have non-uniform thickness in the thickness direction,a large number of fibrous structures exist in the center layer.The cold-rolled texture is strong a and relatively weak ? and ? components.Two-stage cold rolling can improve the homogeneity of the cold-rolled microstructure,weaken the ? and ? components in the coldrolled sheets,and enhance the ? component.(3)In the two-stage cold-rolling,the precipitates of the intermediate annealing sheets are mainly Cu2S,NbN,Cu and their composite precipitates.The average size of the precipitates is large,and a large amount of finely dispersed Cu is present on the matrix,with the annealing temperature increases,the surface density decreases.The precipitates in the primary recrystallization sheets and intermediate annealing sheets have little change,but the average size decreases more.The change of the cold rolling reduction has no obvious effect on the precipitates.(4)During the one-stage cold rolling,the primary recrystallization microstructure is nonuniform and Goss seeds are few,which makes it difficult for the annealed sheet to recrystallize.During the two-stage cold rolling,the primary recrystallization grains of Goss significantly increased.The first cold rolling deformation and the intermediate annealing temperature significantly affected the homogeneity of the primary recrystallized structure,resulting in different degrees of perfect secondary recrystallization.(5)The secondary recrystallization of the finished product sheets is the best with two-stage cold-rolling process with a cold-rolling reduction of 64%and intermediate annealing temperature of 850?.The average grain size is about 25mm,and the magnetic induction is B8=1.844T,the iron loss is P15/50=1.974W/kg.