Texture Control Mechanism Of Low Silicon Non-oriented Silicon Steel With High Magnetic Induction

At present,the output of non-oriented silicon steel accounts for 80%～90%of the output of electrical steel in China.Medium and low silicon steel has a large proportion in non-oriented silicon steel.Non-oriented silicon steel with high magnetic induction is mainly used to make iron core material of high efficiency motor,which can effectively improve motor efficiency,reduce energy consumption and protect environment.Due to the large number of manufacturers of medium and low silicon steel and fierce competition in the market,it is urgent to realize high magnetic impact.Therefore,the development of manufacturing technology for non-oriented silicon steel with low cost and high magnetic induction has become a hot topic both at home and abroad.The purpose of this study is to carry out the composition design and process optimization of 0.3%Si non-oriented silicon steel,and to reveal its effect on the microstructure,texture and magnetic properties of the material,and to develop a high magnetic-inductance and low silicon non-oriented silicon steel.The main contents of the study are as follows:（1）The effects of Mn and Al contents on microstructure,texture and magnetic properties were studied.Three kinds of test steels with different contents of Mn and Al were designed,and hot rolling,cold rolling and annealing experiments were carried out under the same process conditions.The results showed that the contents of Mn and Al could significantly affect the γ/αphase transition temperatures,which would affect the microstructure,texture evolution and magnetic properties.When the steel contained 0.15%Mn and 0.2%Al,the γ/α phase transition temperature was lower,and the hot rolled microstructure was equiaxed ferrite structure.After annealing,the grain size was larger,and the unfavorable y-fiber texture strength was lower.When the steel contained 0.1%Mn,0.3%Al,and 0.15%Mn,0.4%Al,the y/a phase transition temperatures were higher,and there were a small amount of elongated deformation structure in the hot rolled microstructure.The texture strength of a in the cold-rolled sheet increased significantly,and the strong points moved downward along the a orientation line.The unfavorable y-fiber texture strength of the finished product was increased.Therefore,properly reducing the γ/α phase transition temperature is beneficial to improve the magnetic induction and reduce the iron loss.（2）The effects of micro-alloying element Sn on the microstructure,texture evolution and magnetic properties were studied.It was found that Sn element has an important influence on the magnetic properties of non-oriented silicon steel.Compared with the ordinary 0.3%Si nonoriented silicon steel,when Sn was added to the steel,the grain size of the annealed microstructure decreased.The unfavorable y-fiber texture strength of the finished sheeet was significantly reduced,and the texture was optimized.After adding Sn,the average magnetic induction increased by about 0.02T,reaching 1.775T with a slightly increased of iron loss.However,the segregation behavior of Sn needs further study.（3）The effects of finishing temperature on microstructure evolution was studied.It is found that when the final rolling temperature was less than Ar₁-100℃ the rolling deformation of the steel in the ferrite region was large,which led to a small amount of elongated deformable structures.When the final temperature was between Ar₁-100℃-Ar₁,the rolling deformation was smaller in the ferrite region,so microstructure was mainly equiaxed ferrite structure.The closer the final temperature was to Ar₁,the smaller the hardening degree of ferrite grains,and the bigger grain size after grain recovery and growth.When the final rolling temperature was more than Ar₁,the rolling deformation of the steel sheet was not in the ferrite region,which mainly occured in the two-phase region.The large deformation amount provided a large number of nucleation points for phase transition of γ/α,which led to a significant decrease in the grain size after hot rolling.Because the microstructure was heredity,the larger the grain size of the equiaxed ferrite in hot rolled sheets,the larger the grain size of the annealed sheets.Therefore,the closer the final rolling temperature is to Ar₁,the larger the grain size after annealing,and the lower the iron loss.（4）The effect of finishing temperature on the texture evolution and magnetic properties were studied.The initial microstructural state which is considered an important factor in the texture control.When the final rolling temperature was less than Ar₁-100℃,there was deformed microstructure in the hot rolled sheet and {001}<110>texture was strong.Due to the heredity of the texture,the y-fiber texture after annealing was strong.When the final rolling temperature was between Ar₁-1000C～Ar₁,the microstructure of the hot rolled steel is mainly equiaxed ferrite structure,and the λ-fiber texture was stronger,resulting in a stronger λ-fiber texture after annealing.The closer the final rolling temperature was to Ar₁,the larger the grain size,and the weaker the y-fiber texture after annealing.When the final rolling temperature was greater than Ari,the hot rolled grain size decreased,and the unfavorable y-fiber texture was enhanced after annealing.Therefore,the closer the final rolling temperature is to Ar₁,the γ-fiber texture strength after annealing is weaker.It helps improve magnetic properties.