The Structure?Texture And Properties Of Grain-Oriented High Silicon Steel

Grain-oriented high silicon steel(Fe-6.5wt.%Si)has excellent comprehensive magnetic properties(low iron loss,high permeability and smallest magnetostriction coefficient),and is mainly used as the transformer iron core with high efficiency,low noise,low iron loss.However,the increase of the silicon content deteriorates its processability,so it is difficult to be produced by the rolling process.At present,only the chemical vapor deposition(CVD)method can be used for the high silicon steel production in small-scale in Japan,but disadvantages of the CVD still exists such as high processing temperature,halide corrosion of steel sheet and equipment.Compared with the CVD method,the solid powder embedding method can realize solid siliconizaing treatment under the conditions of lower temperature and corrosive halide content,so it is possible to be used to increase the silicon content of grain-oriented silicon steel without changing its texture,then grain-oriented high silicon steel can be synthesized.In this work,research activities were focused on the solid siliconizaing treatment of the grain-oriented silicon steel,including:to carry out the solid siliconzaing and diffusion annealing treatment for the grain-oriented silicon steel to explore the evolution of microstructure,phase and chemical composition,as well as the influence of related factors;to test the magnetic properties and the hardness of typical samples to clarify the relationships between microstructure,phase,chemical composition and properties;to measure texture of the original sample and the sample after the solid siliconizing and the diffusion annealing treatment in order to determine the possibility to produce grain-oriented high silicon steel by means of the solid siliconizing+diffusion annealing treatment.Main results are as follows:(1)An ideal compound layer with smooth surface,densed internal structure and well-bonded with the matrix can be synthesized on the surface of grain-oriented silicon steel after the solid siliconizing treatment at 750?850?,its thickness increases with the treatment temperature and duration,and the influence of the temperature is greater.(2)After the diffusion annealing at 950?1050?,the interface between the compound layer and matrix of the siliconized sample disappears,the microstructure becomes more uniform and the distribution of Si along the depth tends to be uniform.Increasing the annealing temperature is more helpful to speed up this process.After 950??1?2 h diffusion annealing,Fe3Si phase forms in the surface layer,and with the increment of diffusion annealing temperature and duration,the Fe3Si phase in the surface layer transformes into ?-Fe phase.(3)After solid siliconizing and diffusion annealing,the iron loss of the sample at low frequency is higher than that of the original grain oriented silicon steel,and that is significantly reduced(up to 93.93%)at high frequency;meanwhile,the magnetic induction intensity decreases slightly.(4)The hardness of the samples increases with the increment of silicon content,and the hardness of the FeSi phase is higher than that of the Fe3Si phase.With the increment of diffusion annealing temperature and duration,the hardness of the surface layer of the siliconized sample decreases,and the hardness of the matrix increases.The hardness keeps constant along the depth after the diffusion annealing at 1050?.(5)Goss texture in the grain-oriented silicon steel can not be changed after the solid siliconizing and diffusion annealing treatment,so it is reasonably to say that grain-oriented high silicon steel can be synthesized by means of the solid siliconizing and diffusion annealing treatment.