Siliconizing Behavior Of 3%Non-Grain Oriented Silicon Steel

Silicon steel,as a kind of soft magnetic material,is widely used as iron core of transformer and motor.It is known that 6.5%Si-Fe alloy(i.e.high silicon steel)exhibits excellent soft magnetic properties,such as low core loss,high permeability and nearly zero magnetostriction,unfortunately the silicon steel(owing to its poor elongation)can not be produced through cold rolling in industry while the Si content is higher than 4%.Now,only the CVD method is applied for the production of high silicon steel in Japan,however the application just be restrained in a small scale due to the obstacles as high deposition temperature,serious corrosion of the equipment and steel sheet induced by SiCl4 gas and environment pollution originated from FeCl2 gas.Recently,more research activities were focus on the solid siliconizing technology,by which dense compounder layer can be synthesized for the silicon steel with a nano structured surface layer when both the siliconizing temperature and the corrosive halide content are much lower than that of conventional CVD method.However,due to that the asymmetrical rolling has not been successfully in industry,it is difficult to apply the solid siliconizing technology based on surface nanocrystallizition induced by the asymmetrical rolling.On the basis of the previous investigation,research activities were focus on the siliconized behaviors of cold rolled 3%non-grain oriented silicon steel,including:to siliconize the silicon steel at lower temperature and examine the effects of the treatmental parameters and structure;to carried out diffusion annealing for the siliconized sample and examine the effects of the treatmental parameters on the microstructure and the Si distribution along the depth;to perform the conventional rolling and asymmetrical rolling for the siliconized sample and investigate the variation of density and surface roughness of the compounder layer.Main results are as follows:(1)Compounder layer can be synthesized on the surface of cold rolled 3%non-oriented silicon steel after solid siliconizing at 750? for 20 minutes,which consists of FeSi and Fe3Si phases.With the inceasement of treatment temperature and duration,both the thickness of the compounder layer and the content of FeSi increase;Activited silicon powder,0.5%of the halide and argon gas protection are helpful for the increasement of the density of the compounder layer.(2)In the initial stage of the diffusion annealing of the siliconized sample,Si diffuses primarily from the compounder layer to the matrix.While the temperature increase to above 900? Si diffusion in the top surface layer occurs,leading to the transformation Fe3Si in the compounder layer to ?-Fe.The increasement of the thickness of the compounder layer may affected the variations of the chemical composition and the phases,and the Ar protection has contributed to reduce the number of hole in the compounder layer.(3)By using conventional rolling,the reduction is about 2%When cracks appear in Fe3Si phase at room temperature,which can be increased slightly when asymmetrical rolling is adopted.Cold rolling can not reduce the holes in the compounder layer significantly,but can reduce the roughness of the sheet.