Microstructure And Precipitate Evolution Of Rare Earth High Strength Non-oriented Silicon Steel During Preparation

As the country actively advocates "carbon peak","carbon neutral" and green energy transformation,promote the development of automobiles to the direction of new energy.Drive motor is one of the core components of new energy vehicles.Non-oriented silicon steel core is the key material to drive motor to achieve energy conversion.Non-oriented silicon steel for new energy vehicle driving motor needs to ensure high magnetic induction,low iron loss and high strength.The strength of non-oriented silicon steel was improved by means of solution strengthening,precipitation strengthening and fine grain strengthening by optimizing Si,Al and Mn composition and adding alloying elements.In this thesis,the non-oriented silicon steel added with rare earth Ce and Nb is taken as the research object,and the high-strength non-oriented silicon steel is prepared by reasonable processing technology.The evolution laws of microstructure,texture and precipitates in the preparation process are studied.The research results are as follows: the microstructure and texture of hot-rolled plate are unevenly distributed in the longitudinal section,the surface layer is very fine recrystallized grains,and the central layer is banded deformation structure.Texture the surface layer and subsurface layer are strong Goss texture and a small amount of copper texture,and the central layer is mainly α Thread texture and γ Thread texture.There are Mn S +Nb C and Nb C precipitation in hot rolled plate.After normalization,it is completely recrystallized,and the grain size tends to increase from the surface layer to the central layer.Goss texture of hot rolled plate after regularization,α Thread texture and γ The density level of linear texture decreased significantly,and {100} < 001 > texture appeared.Precipitate agglomeration and coarsening.In the continuous annealing process,the microstructure in the early stage of continuous annealing is banded fiber,and only a few recrystallized grains are deposited.A large number of Fe-Si-Nb phases along grain boundaries are precipitated during this process.Continuous annealing,rapid recrystallization,forming a complete recrystallization structure.At this time,Fe-Si-Nb phase dissolved back,and the precipitation integral number decreased.After continuous annealing,the precipitation of Mn S+Nb C and Nb C continued coarsenning,and the average size of the precipitates reached 143μm.During the continuous annealing of the NB-containing high strength unoriented silicon steel,the development of γtexture was inhibited at the early stage of continuous annealing,and a large amount of η texture appeared at the middle stage of continuous annealing.However,the γ texture gradually increased and η texture began to weaken as the inhibition of γ texture weakened.At the later stage of continuous annealing,the recrystallized grain grows up,and the change of texture is not obvious.The final texture of the annealed plate is mainly γ texture and η line texture.In the non-oriented silicon steel,Ce combines with S and O to form large-size inclusions,which can significantly reduce the precipitation of Mn S in the steel.In addition,the inclusion containing Ce will also degenerate into large-size composite inclusions with Al N inclusions,which will reduce the precipitation of Al N in the steel.It is found that there is almost no single phase precipitation of Al N and Mn S,and the addition of Ce effectively inhibits the precipitation of Mn S and Al N.