Improvement Of Microstructure And Magnetic Properties Of Mid-low Grade Non-oriented Silicon Steels

Mid-low grade non-oriented silicon steel is the main iron core material of the small and medium-sized motors,such as automobile motors,household appliances motors and so on.The magnetic performance has an important influence on the development of the energy saving and miniaturization of the motor.The research is based on the properties of Sha-steel mid-low grade non-oriented silicon steel,and take the methods of laborary development and field test,including chemical composition,temperature of the hot rolling,annealing process and so on,to study on optimizing control of composition and processing of non-oriented silicon steel.The results are as follows:(1)The content of the Si has a significient effect on the mid-low non-oriented silicon hot rolling steel of recrystallization ratio.The grain of the hot rolling plate can be fully recrystallized when the silicon content is less than 0.9%.The recrystallization ratio of the hot rolled plate decrease gradually with the increase of silicon content,when the silicon content is(1.27～1.82)%.Optimization of finishing temperature can effectively increase the recrystallization ratio with different silicon content and improve the magnetic properties of coil.(2)It is difficult to form {100}texture due to the phase transformation during hot rolling when the silicon content is less than 0.9%.The texture {100} in slab can be retained effectively in hot rolling process when the silicon content is(1.27～1.82)%.Especially when the silicon content is up to 1.82%,strong texture {100} can be obtained after annealing.(3)The factory production show that,the chemical composition,process of the hot rolling and annealing is the three key factors which controlling the magnetic properties of the sheet.Among them,the influence of components is relatively greater.It is important for the mid-low grade non-oriented silicon steel as controling the elements S、P and Sb.We can apparently decrease the iron loss when the harmful elements S is less than 25ppm.Proper P(0.03%)can improve the stampinig and shearing properties.It will significant deterioration of magnetic properties when the element P increase to 0.08%and above.The magnetic induction intensity(B50)increases to 0.02T and above as adding 0.05%Sb.Also it can be improving the stability of the magnetic performance in coil.The reason is that Sb precipitates on the grain boundary and inhibits the growth of {111} texture.(4)By optimizing the finishing rolling temperature,annealing temperature and time,the grain size of(0.37～1.43)%Si non-oriented silicon steel increases by 10～16μm,the grain size of 1.82%Si increases by 28μm,and the iron loss decreases remarkably.The magnetic properties are improved effectively.The finish rolling temperature was controlled more than 870℃,and ensure its stability,on the premise of optimization of composition and stability of final annealing process,the magnetic properties qualification of the(0.37～1.43)%Si mid-low grade non-oriented silicon steel can be increased to more than 95%.