Study On Microstructure And Properties Of Non-oriented 4.5wt%Si Steel Containing Cr

As an important soft magnetic material used in generators,motors and transformers,non-oriented silicon steel is one of the key basic materials for electric power,communications,military industry and new energy vehicles.The unoriented 4.5wt%Si steel has good mechanical properties and excellent soft magnetic properties.To meet the current demand of high frequency motor,it is necessary to further improve the strength and magnetic properties.The strength of non-oriented silicon steel can be greatly improved by adding Cr element,and the magnetic properties can be optimized by adjusting rolling and annealing process.Based on the two ingredients no orientation 4.5wt%Si steel as the research material,the rolling,respectively,intermediate annealing,the recrystallization temperature tensile and critical deformation process,such as the Cr element in the microstructure,texture of sample of each phase,the influence of the magnetic and mechanical properties was tested and analyzed,in this paper,the main research content is as follows:（1）The effects of intermediate annealing process and Cr element on microstructure and properties of 4.5wt%Si steel were studied.The effects of Cr element on microstructure,texture evolution,magnetic properties and mechanical properties of 4.5wt%Si steel under different annealing process were analyzed.The results show that the strength ofγ-line texture in 4.5wt%Si Cr-containing non-oriented steel increases with the extension of recrystallization annealing time after intermediate annealing.The strength ofγ-line texture in 4.5wt%Si steel without Cr and orientation decreases greatly,and the rotational cubic texture increases significantly.The 4.5wt%Si steel without Cr and orientation has excellent magnetic properties with B₅₀ of 1.725T and iron loss of 2.97W/kg(P_1.5/50),15.71W/kg(P_1.0/400)and 15.92W/kg(P_0.5/1000).The strength and elongation of 4.5wt%Si steel containing Cr are up to 705MPa and 19.33%respectively.（2）The change of internal microstructure and its effect on mechanical properties of4.5wt%Si steel after medium temperature tension were studied,and the reasons for the change of mechanical properties of non-oriented silicon steel used as rotor or core at different operating temperatures were analyzed.The results show that with the increase of tensile temperature,the microstructure of silicon steel hardly changes,the tensile strength does not decrease obviously,and the elongation increases slightly.The segregation of Cr element at grain boundary is not obvious,and the addition of Al and Cr element at the same time will affect the segregation of Cr element at grain boundary,which will further affect the microstructure and texture evolution of silicon steel during processing.（3）The effects of critical deformation on microstructure evolution,mechanicalproperties and texture characteristics of 4.5wt%Si steel were investigated.The results show that the ductility decreases obviously after critical deformation.With the increase of the reduction of critical deformation,the tensile strength increases gradually.When the reduction reaches 10%～15%,the increase of tensile strength is not obvious.The introduction of a large number of sub grain boundaries in the critical deformation process improves the mechanical properties and has a significant impact on the texture characteristics.Finally,the{111}harmful texture in the steel is greatly reduced and the{001}favorable texture component is significantly increased.