The Siliconizing Behavior Of Grain-oriented Silicon Steels

The grain-oriented silicon steels are the excelent soft magnetic material due to its superior comprehensive soft magnetic properties,such as high permeability,very low core loss and nearly zero magnetostriction,so it can be widely used in power and electric industries.However,it is extremely difficult to produce high silicon steel sheet by conventional rolling techniques at room temperature.Up to know,many methods were proposed for the synthesizing of high silicon steel,however only the chemical vapor deposition CVD method can be used for a small-scale production in Japan,the key problems,that restrains the large-scale application of the CVD method,included the follows:serious corrosion of equipment and sheet surface owing to high percentage of halide and high siliconizing temperature,complex warm-rolling process(necessary for the reduction of roughness of sheet surface induced by high percentage of halide),iron loss of the sheet surface and environment pollution of FeCl2 gas.Low temperature siliconizing technology can solve the problems of CVD method,on the basis of the previous research,we obtained dense siliconizing layer rely on silicon-iron balance.If applied it to the grain-oriented silicon steels,will not happen replies and recrystallization in siliconizing process,because of no defects in it.we not only improve the content of silicon,Goss texture also be preserved,the grain-oriented high silicon steel can be obtained.Then,we select Fe-3%Si grain-oriented silicon steels with strong Goss texture to siliconize to siliconize and diffusion annealing at low temperature.By analyzing the organization and material composition,determine the siliconizing parameters on the morphology and phase of siliconizing layer.The main conclusions are as follows:1)The enhancements of temperature and duration in the siliconizing process and the Si content in original sheet in some ranges are helpful for the increment of the density of the compound layer and the reduction of the surface roughness.2)The phases in siliconizing initial is Fe3Si,with the extension of time,begin to form FeSi phase.3)During diffusion annealing process,Si diffusion from surface compound layer to internal matrix.With the increase of temperature and heat preservation time,silicon tend to be evenly distributed.4)After diffusion annealing,the surface phase from FeSi to Fe3Si phase.5)After siliconizing and difusion annealing,the samples due to form the FeSi and Fe3Si ordered phase,the hardness increased significantly,and the fracture mode from ductile fracture to brittle fracture.