Research On Silicon Diffusion In Preparing High Silicon Steel By CVD Method

Silicon steel,as an essential material in transformer core,is widely used in electronic power equipment.It has good soft magnetic properties.In particular,its magnetostriction is almost zero when content reach 6.5wt%.Low iron loss,high coercive force,so it is almost perfect electrical steel material.CVD method is only way realize industrial production of high silicon steel so far.This paper,based on the principle of preparing it by CVD method,put forward grain boundary diffusion plays an important role in silicon integrated diffusion,and build a numerical model combining silicon diffusion and grain boundary diffusion to used to predict silicon content distribution in the siliconizing process.The paper analyzes the influence of pretreatment of base material on siliconizing diffusion.It has important reference value for realizing industrialized production of high silicon steel.Based on the requirement of CVD method to build equipment preparing high silicon steel.Measuring low and high temperature zone of tube furnace.Determine numerical relationship between content of reaction gas SiCl4 and temperature of water bath pot,it has nothing to do with carrier gas N2 flow rate.Introducing experimental operation and control method of process parameter.CVD siliconizing experiments is happen in vacuum furnace.Along penetrating direction,using SEM and EDS quantificationally measure silicon content near grain boundary(GB)and inner grain.It is found that silicon content and penetrating depth near grain boundary significantly higher than intracrystalline.It is indicated that GB is rapid diffusion channel.Using SEM and software to get GB width and grain size and applied them to building the microscopic geometry model.Basing on the principle of Voronoi diagram,then under the environment of Matlab and ABAQUS,silicon diffusion model has been built.Body diffusion coefficient is obtained by using Boltzmann-Matano method and apply it to model calculation By comparing the average silicon content in the grain and near the GB,it obtains GB diffusion coefficients under 1100? and 1200?.They are 103?104 times higher than the body diffusion coefficient.After validated,diffusion model is good predict distribution of silicon content.By doing heat treatment for base material,explores temperature,time and heating mode influence on grain size.By comparing siliconizing differences of base material before and after annealing,it is found that siliconizing efficiency of cold rolling base material is higher than base material after heat treatment.The relation between average silicon content and siliconizing time is built,it has important guiding significance for the construction of continuous siliconizing device.