Study On Preparation Of High-Performance Electrical Steel Based On CVD

6.5%high silicon steel has the advantages of low iron loss at high frequency,reduced hysteresis and low noise.It is an ideal soft magnetic material with high efficiency,energy saving and portability.However,the brittleness of 6.5%high silicon steel is relatively high,and it can not be produced by traditional rolling process.At present,only CVD method can realize the industrial production of 6.5%high silicon steel.Because of the technical blockade of Japan,the domestic related technical research is not mature enough to realize industrial production.And with the application of 6.5%high silicon steel becoming more and more widespread,it is urgent to establish a continuous siliconizing production line by CVD method.The effects of process parameters on the composition,structure and properties of CVD siliconizing process provide theoretical and experimental data for the industrial production of 6.5%high silicon steel.The following conclusions are drawn:(1)The effects of reaction temperature,gas concentration and reaction time on the process of siliconizing were investigated.The composition of samples after siliconizing was detected by EPMA energy spectrum and line scan technique.The results of EDS show that the siliconizing rate increases with the increase of temperature,and the effect of temperature on the siliconizing rate decreases after 1100?.The concentration of SiCl4 in mixed gas can be accurately controlled by controlling the temperature of water bath,and the effect of SiCl4 concentration on the siliconizing process can be detected.The experimental results show that the higher the concentration of SiCl4,the better the siliconizing process.The faster the siliconizing rate is,the more the siliconizing time prolongs,the silicon content in silicon steel changes linearly with the siliconizing time,so the siliconizing time can be controlled to prepare high silicon steel with different content.(2)The distribution of silicon content along the thickness will affect not only the mechanical properties but also the magnetic properties of silicon steel.The silicon steel with high surface silicon content and low core silicon content is called gradient silicon steel,because the core silicon content is low,the toughness and ductility are improved;because the surface silicon content is high,the hysteresis loss is concentrated on the material surface,and the high frequency iron loss is reduced.Gradient silicon steel can be prepared by adjusting diffusion temperature or diffusion time,and its properties can be tested.It is found that the high frequency iron loss of gradient silicon steel is lower than average silicon content steel.In addition,gradient silicon steel with different composition can be manufactured by adjusting the experimental material or gas concentration.The test results show that the surface silicon of gradient silicon steel is increased.The iron loss can be effectively reduced by the content.(3)The effect of siliconizing conditions and material preparation process on the texture of CVD products was studied.The experimental results show that the main texture types of the primary cold rolled sheet with 0.2mm thickness after siliconizing are gamma texture and alpha texture.The texture of the finished sheet will change with the change of siliconizing temperature or holding time,but the intensity of the refractory gamma texture is always high;the main texture distribution of the secondary cold rolled sheet with 0.2mm thickness after siliconizing is scattered.Chaotic,cube texture,Goss texture is relatively strong.(4)The effect of phase transformation annealing on the structure and properties of low carbon electrical steel was studied.Firstly,the effect of cooling mode on phase transformation annealing structure was studied.After rapid cooling,columnar crystals were obtained only in two-phase annealing condition,while columnar crystals appeared in both two-phase and austenite annealing structures under slow annealing condition.The flow rate of protective gas also affected the phase transformation annealing process.When the flow rate is small,the transformation process from the surface to the inside is slow,the axis diameter of columnar crystals formed after transformation is small,and when the gas flow rate is large,the coarse columnar crystals are formed after transformation;moreover,the axis diameter of columnar crystals increases with the increase of temperature or the prolongation of annealing time;and the surface state of the sample also has an important influence on the transformation structure.When the surface is clean and smooth,the columnar crystal can grow to the center after phase transformation annealing,and the equal crystal disappears.If the surface is oxidized,the equal crystal structure in the process center will not disappear in any case.By reasonable phase transformation annealing process,more {100} and {110} oriented columnar crystals can be obtained,which greatly improves the magnetic properties.