Preparation,Microstructure And Property Of Non-oriented High-silicon Steel

The high silicon steel has excellent soft magnetic properties.It is the ideal core material of transformers and electrical Equipment for applicationsof low core loss,low noise under medium-high frequency.With increasing silicon content,toughness deteriorates.High silicon steel sheet is difficult to produce by conventional rolling techniques at room temperature.Only the chemical vapor deposition(CVD)method was used for a small-scale production in Japan,the key problems:serious corrosion of equipment and sheet surface due to high percentage of Cl-ion and high siliconizing temperature,complex warm-rolling process and environment pollution of FeCl2 gas.In our previous work,we proposed a new method(i.e.asymmetric rolling and solid siliconizing)to produce high silicon steel.Nanostructure was synthesized in the top surface layer of non-oriented silicon steel by means of asymmetric rolling.Large volume fraction of grain dislocations,boundaries and vacancy defects in the surface layer can provide diffusion channels for silicon atom,and the large amount of active atoms existing in the top surface layer can reduce dependence on halide catalyst.The combination of the nanostructure and active atoms existing can significantly reduce the siliconizing temperature and the series negative effect of the high percentage of Cl-ion.But the asymmetric rolling involved in the asymmetric rolling and solid siliconizing has not been applied in the industry.Previous work has systematically studied the technology of solid siliconizing,and now the technology of preparing high silicon compound layer on surface of cold-rolling silicon steel is mature.0.3%non-oriented silicon steel was selected to be rolled to 0.3mm thickness.Solid siliconizing treatments were performed to obtain compound layer of the cold rolled samples at Ts for different durations by powder embedding method.The 20min and 30min siliconizing samples were selected to diffusion annealing under different parameters(include temperature,durations and atmosphere).The cross-sectional microstructure,Si variation along the depth and phases in the top surface layer of the samples after the cold rolling,siliconizing and diffusion annealing were examined by using OM,XRD,SEM and EDS,and the effects of siliconizing and diffusion annealing parameters on the Si diffusion behaviors were analyzed.The hardness,tensile and ODF test of the typical samples were analyzed.The main conclusions are as follows:1.By using solid siliconizing technology,hard compound layer with the thickness of several tens micrometers can be obtained for the 3%Si cold-rolled non-oriented silicon steel surface.Our research work shows that the enhancement of duration in the siliconizing process is helpful for the increment of the density and thickness of the compound layer and the reduction of the hole in compound layer the surface roughness.There is a flat interface between the compound layer and the matrix,and a slump in the silicon element at the interface.2.The phase in the top surface layer of the sample after the initial siliconizing is Fe3Si,and with the increment of sicliconzing duration,the surface phases transformation from Fe3Si to FeSi phase.3.Diffusion annealing can promoted the Si diffusion from surface compound layer to the matrix.And with the increment of treatment temperature and duration,the interface between compound layer and matrix disappears,the density becomes worse,pore in compound layer increases,and oxidation is serious.4.After the siliconizing and diffusion annealing,the surface phase of the sample was transformed from FeSi phase to Fe3Si phase after the infiltration,and the FeSi phase was eventually formed.5.After the siliconizing and diffusion annealing,machinability is improved and surface texture of sample significantly weakens.