The Preparation,Organization And Properties Of High Silicon-iron Alloy With {100} Texture

High silicon-iron alloy(especially Fe-6.5wt.%Si alloy)exhibits excellent comprehensive magnetic properties(i.e.low iron loss,high permeability and nearly zero magnetostriction coefficient),and is ideal iron core material for the high-frequency alter nator,electricmoter and transformer.With the development of electromechanical equipment toward high-frequency,high-efficiency,low-noise and small-sized,the high silicon-iron alloy becomes more and more important,however When its silicon exceeds 4.5wt.%,the brittleness is large and the elongation is close to zero,which is difficult to roll in a conventional manner and is limited in application.Though NKK Corporation successfully produced Fe-6.5wt.%Si alloy in small batches by CVD method in Japan,there are still defects to be overcomes,such as high energy consumption,FeCl2 gas pollution,plate deformation and equipment corrosion,which is far from meeting market demand.However no synthesized techniques can be used in the industry production in our country up to now.In my previous investigation on the solid-siliconizing treatment,the Kirkendall effect was effectively avoided and a equilibrium diffusion between silicon and iron was achieved,then a densed compound layer was synthesized on the surface of 3wt.%grain-oriented silicon steel.After the diffusion annealing treatment for the siliconized sample,high silicon-iron alloy with {100} texture was synthesized,it iron loss was sharply reached by 80%,much higher the that reported by references(20%～50%).Base on previous work,scientific investigation to be carried out in the article were summarized as follows:to study the silicon-iron reaction diffusion mechanism during the siliconizing treatment process,and clarify the effects of the halid in the siliconizing medium,in order to enhance the density of the compound layer;to study phase transformations during the siliconizing and diffusion annealing treatment process,in order to obtain ideal single Fe3Si phase in the final sample necessary for the better magnetic properties;to study the texture transformation,and obtain sharp {100} texture excellent in magnetic properties in high silicon-iron alloy;to clarify the relationships between the micrustructures(silicon content,gradient structure,phases and texture)and the magnetic properties(high-frequency iron loss and magnetic induction intensity).It is expected to obtain deep understanding on the characters of the this alloy through this investigation,and promote the practical application of the high silicon-iron alloy in high frequency transformer.The main conclusions are as follows:(1)An ideal compound layer with smooth surface,densed internal sturcture and well-bonded with the matrix can be synthesized on the surface of non-oriented silicon steel after the solid siliconizing treatment at 800℃ for 10～20 min.Then the compound layer is composed of the surface FeSi phase and the adjacent Fe3Si phase layer.The thickness of compound layer increases and the siliconizing structure optimizes with the siliconizing duration.(2)After diffusion annealing at 1050℃ for 1 h,the interface between the compound layer and the matrix of siliconized sample disappears.The surface phase changes to α-Fe phase,the internal structure was more dense,and the silicon on both sides has a gradient distribution along the depth.In addition,after annealing for 2 h,the whole silicon of the plate tends to be uniformly distributed.(3)At high frequencies(0.0025 T,10～100 kHz),the iron loss of the siliconized and annealed sheet is generally reduced by about 50%to 80%.Among them,the gradient silicon steel with surface silicon content around 6.5wt%is the smallest and its iron loss can be reduced by 82.835%,which is smaller than the original.However,the intensity of magnetic induction is slightly reduced.(4)The micro-hardness of the sample is basically linear correspondence with the silicon content distribution,and the hardness of the surface FeSi phase region is slightly higher than that of the Fe3Si phase region.In addition,the tensile properties of the siliconized plate are slightly improved after diffusion annealing.(5)The {100} texture of the original sheet after solid siliconizing and diffusion annealing is unchanged,so high silicon-iron alloy with excellent properties can be prepared by solid siliconizing and diffusion annealing.