Structure And Texture Of Grain-oriented High Silicon Steel Synthesized By Pack Cementation Method

The silicon steel has been widely used as the iron core of the transformer and electrical machine,and their power loss usually occurs due to eddy current and hysteresis.The power loss by eddy current is proportional to the square of the frequency.Thus,a large amount of electric power losses in transformers at higher frequency.It is known that high silicon steel exhibited a better soft magnetic performance comparing with traditional silicon steel.Though the power loss can be reduced by increasing of Si,but brittleness maybe increased,therefore,it is difficult to produce high silicon steel by using traditional rolling technique.It is reported that high silicon steel can be synthesized through the silicon diffusion into the 3wt.%silicon steel.Now,only the chemical vapor deposition(CVD)method has been used for a small-scale production of high silicon steel in Japan,however it subjected the disadvantages including:serious corrosion of equipment induced by high siliconizing temperature and high percentage of halide,environment pollution of FeCl2 gas,complex warm-rolling process to make surface smooth and so on.Previous work shows that solid siliconizing could produce high silicon steel.The compact and smooth siliconizing layer with few defects had been obtained at 850℃.When it was applied to increase the content of Si in the sample,the Si obtained is uaually more higher than 6.5wt.%,so the Si content should be decreased.Besides,the texture transformation and diffusion thermodynamics of Si-Fe should be researched as well.In this work,low temperature solid siliconizing was carried out for grain-oriented silicon steel,and the texture,Si-Fe diffusion and phase transformation were investigated,main results can be concluded as follows:1)Dense compound layer can be obtained after siliconizing at 750℃ for 25min and its Si content can appproach to 6.5wt.%.2)Surface nanocrystallization induced by cross-shear rolling can not accelerate the diffusion of Si but influenced the quality of the siliconizing layer.3)In the initial stage of the siliconizing process,Fe3Si phase forms.With the increment of the annealing temperature,the Fe3Si phase transforms gradually into FeSi phase.Original texture of the oriented silicon steel might be changed after siliconizing.4)Two-phase hybrid zone can not form during the siliconizing process,due the reaction-diffusion.The activation energies of Si diffusion in Fe-3wt.%Si is 193kJ/mol.The diffusion coefficients at 750℃ is 2.91×10-13m2/s and 2.2×10-12～2.6×10-12m2/s at 850℃.