Effects Of Normalization And Annealing Processes On Properties Of Rare-earth 50W470 Non-oriented Silicon Steel

Non-oriented silicon steel is widely used in electric power,electronic military magnetic properties and other fields as an important soft magnetic material.With the formal implementation of the new standard"Motor Energy Efficiency Limit value and Energy Efficiency Grade",the demand for medium and high grade non-oriented silicon steel increases sharply.50W470 non-oriented silicon steel as a high grade non-oriented silicon steel,the market demand is huge,is expected to reach 3 million tons/year in2035.Magnetic property is an important factor to evaluate the properties of non-oriented silicon steel,but the loss and magnetic induction intensity of rare earth 50W470non-oriented silicon steel produced by a factory cannot fully meet the market demand for magnetic property.Therefore,in combination with the field production conditions,this paper optimized the normalization and annealing process in the laboratory to improve the magnetic properties of rare-earth 50W470 non-oriented silicon steel,providing theoretical guidance for the field production.In this paper,the effects of different normalizing and annealing processes on the microstructure,inclusions and texture of 50W470 unoriented rare earth silicon steel produced by a factory were studied by using box resistance furnace and continuous annealing furnace to simulate the field production environment.The normalized temperatures were 930℃,950℃,970℃,and the normalized time was 3min,5min,7min,respectively.The annealing temperature was 870℃,890℃,and the annealing rate was60m/min,70m/min,80m/min.The microstructure of hot rolled plate,tempered plate and annealed plate was observed by Zeiss metallo sgraphic microscope and scanning electron microscope.The types,morphology and quantity of inclusions in hot-rolled and normalized tissues were observed and counted by scanning electron microscope combined with EDS.X-Ray Diffractometer（XRD）was used to detect the macroscopic texture of hot rolled plate,normalized plate,cold rolled plate and annealed plate,and field emission scanning electron microscope（SEM）was used to detect the microscopic texture of annealed plate with different annealing processes.The iron loss and magnetic induction intensity of annealed plate were measured by single chip method.The experimental results show that the deformation structure disappears and recrystallization occurs after the hot rolled plate is normalized.The average recrystallized grain size increases with the increase of the temperature from 930℃to 970℃for 5min.The maximum average recrystallized grain size is 203.67μm at 970℃,but the uniformity of recrystallized microstructure is poor.The size of recrystallized grain increases with the increase of the normalization time from 3min to 7min at 950℃.At 950℃for 5min,the recrystallized grain size is large,with a diameter of 166.96μm,and the recrystallized structure is uniform.The inclusions of rare earth 50W470 non-oriented silicon steel are Al N,Al₂O₃,Ce₂O₂S and Ce Al O₃under different normalizing conditions.The strength of the 1/2 layer rotating cubic texture of the rare earth 50W470non-oriented silicon steel decreases from 11.48 to 2.01 at 950℃for 3min compared with that of the hot rolled steel.The texture components under different normalization processes are basically the same,1/8 layer is mainly Gaussian texture,1/2 layer is mainly{001}<110>rotated cubic texture,{111}<112>texture and a small amount of{011}<100>Gaussian texture.When the normalization time is 5min,the texture strength of{111}<112>increases from 1.34 to 2.89 as the normalization temperature increases from 930℃to970℃.With the increase of annealing temperature,the proportion of favorable texture decreases,the recrystallized grain size increases,and the iron loss value decreases.At the annealing rate of 60m/min,with the increase of annealing temperature from 870℃to890℃,the proportion of favorable texture{100}and{110}decreases from 55.7%to33.9%,the average grain size increases from 60.42μm to 97.57μm,and P1.5 decreases from 2.83 to 2.71W/Kg.Under the conditions of our laboratory,the optimal production process of rare-earth50W470 non-oriented silicon steel is normalizing for 5min at 950℃and annealing at60m/min at 890℃.At this time,P_1.5is 2.71W/Kg and B₅₀is 1.7289T.