Effect Of Rare Earth Y On Microstructure And Properties Of High Strength 4.5wt% Si Steel For New Energy Vehicles

With the development of new energy vehicles,the requirement for magnetic and mechanical properties of non-oriented electrical steel become more strict because of the application of equipment with high frequency and the improvement of energy efficiency standards.Compared with 6.5%Si steel,4.5%Si steel has better magnetic and mechanical properties,which is suitable for the material of stator and rotor of driving motor in the future.However,the difficulty is how to greatly improve the strength and ensure excellent magnetic properties with high silicon content.Considering the purification and inclusion modification of rare earth,this paper improves the magnetic properties by adding an appropriate amount of rare earth Y to 4.5%Si steel,ensures the strength of non-oriented silicon steel by optimizing the final annealing process,and the final sheets of 4.5%Si steel with high strength,high magnetic induction and low iron loss were produced.The effect of rare earth Y on the properties and recrystallization texture of 4.5%Si steels were systematically studied,and the main conclusions were obtained:（1）After annealing at 850℃for 2 min,the magnetic and mechanical properties of 4.5%Si steels containing 0.012%Y are better.The magnetic induction strength B₅₀ is 1.662 T,the iron loss P_10/400 is 15.72 W/kg,and the yield strength is 537.9 MPa.Under the same yield strength,the iron loss P10/400 is nearly 10 W/kg lower than that of the existing commercial high-strength silicon steel.Rare earth Y improves the impact toughness of 4.5%Si steel at 200℃.When the content of rare earth Y is 0.016%,the impact toughness of the sample is the best.（2）An appropriate amount of rare earth Y reduces the density of fine inclusions and increases the average size of inclusions.Moreover,Y can effectively modify nano square inclusions into spherical composite inclusions and inhibit the separate precipitation of nano square inclusions.An appropriate amount of rare earth Y reduces the grain boundary migration activation energy,and increases the grain size of the final sheets.According to the magnetocrystalline anisotropy parameters and iron loss separation model,rare earth Y reduces the iron loss by increasing the grain size and optimizing the texture.（3）An appropriate amount of rare earth Y enhances{001}<130>texture and weakens theγtexture of final sheets.The segregation of rare earth Y at the grain boundary reduces the nucleation advantage of{111}grains at the grain boundary.Compared with Al₂O₃ inclusion,Y₂O₂S inclusion with the same size produced more distortion in the matrix under the same strain,and accumulated larger misorientation,making the deformed grains with low energy storage nucleate faster at early recrystallization stage,which provided more preferential nucleation positions of{223}<110>and{001}deformed grains for{001}<130>and{114}<481>grains,to prevent early recrystallization from being engulfed by{111}<112>grains.{100}<013>and{114}<481>grains have faster grain boundary mobility in the{001}<110>-{223}<110>deformed matrix at the early recrystallization stage.At the early stage of recrystallization,the{111}and{114}<481>grains with quantitative and size advantages can become the main part of the recrystallized grains.With the grain growth,the cluster phenomenon of{111}grains causes orientation pinning and the grain growth is inhibited.The{001}<130>grains with low surface energy are easier to grow to become the main texture of final sheets.