Research On Microstructure And Recrystallization Behavior Of 3.2wt.%Si High Strength Non-oriented Electrical Steel

As an essential soft magnetic alloy in the electrical,electronic and communication industries,fully processed non-oriented electrical steel is widely used as the core material of motors.With the development of industry,motors have been required to operate at higher frequency and speed,while conventional rotor cores are difficult to withstand the centrifugal force generated by high-speed rotation.The selected core material should not only have excellent magnetic properties,but also have outstanding mechanical properties under various service conditions to prevent the deformation and failure of the rotor core.However,while the mechanical properties of non-oriented electrical steel are improved,it will to some extent deteriorate its magnetic properties,leading to the inability of non-oriented electrical steel to have excellent mechanical and magnetic properties at the same time.Therefore,it is necessary to adjust and optimize the production process of high-strength non-oriented electrical steel.In this paper,3.2 wt.%Si Cu-bearing non-oriented electrical steel and 3.2 wt.%Si Nb-bearing non-oriented electrical steel were taken as the research materials.The mechanical and magnetic properties of 3.2 wt.%Si non-oriented electrical steel were synchronously optimized using the step-by-step control theory,and the recrystallization behavior and strengthening mechanism during the preparation process were analyzed and discussed.The findings of the paper include:（1）The effects of the two-step annealing process on the recrystallization behavior and magnetic properties of 3.2 wt.%Si Cu-bearing non-oriented electrical steel were studied.The results indicate that the annealing process of low-temperature nucleation and high-temperature growth inherits and develops the{100}texture in the low-temperature nucleation sheet during the high-temperature growth process,resulting in a{100}<001>texture that is favorable for magnetic properties and occupies a dominant position.This process can obtain the best magnetic properties,with a magnetic induction strength of 1.653 T and iron losses of 2.948 W/kg(P_15/50),22.807 W/kg(P_10/400),and 26.219W/kg(P_5/1000),respectively.（2）The effect of the aging process on the mechanical properties of the two-step annealed sheets of Cu-bearing non-oriented electrical steel was studied.After the aging treatment,the segregation of Cu elements appeared in the matrix and formed obvious nano-sized Cu-rich clusters,which can improve the yield strength and tensile strength of the annealed sheets in various processes to varying degrees while meeting the application requirements.The tensile strength of the low-temperature nucleation and high-temperature growth process aged sheet reaches 695 MPa.Therefore,the low-temperature nucleation and high-temperature growth process can achieve the best match between mechanical and magnetic properties of 3.2 wt.%Si Cu-bearing non-oriented electrical steel.（3）The effect of the Nb element on the recrystallization behavior and properties of3.2wt.%Si non-oriented electrical steel after final annealing was studied.The results indicate that although the addition of the Nb element can reduce the magnetic induction strength of the experimental steel,it can also significantly improve the strength of the non-oriented electrical steel matrix.Although prolonging the annealing time reduces the strength of Nb containing non-oriented electrical steel,it also optimizes its texture and magnetic properties to some extent.The aging treatment process can not only optimize the texture of the final annealed sheet of Nb containing non-oriented electrical steel,but also improve its magnetic properties.It can also increase the quantity and density of Nb rich precipitates,further improving the mechanical properties of annealed sheets.Therefore,adding an aging process to Nb containing non-oriented electrical steel can achieve synchronous optimization of magnetic and mechanical properties.