Effect Of Fluidized In-Situ Vapor Deposition Process Parameters On Microstructure And Properties Of High Silicon Steel Composite Core

High silicon steel core has excellent properties such as high permeability,low core loss,near zero magnetostriction coefficient and low coercivity,so it is widely used in electrical equipment such as generators and transformers.However,due to its high brittleness at room temperature,it is difficult to be formed by conventional rolling process,which seriously limits its application in industrial field.Therefore,the development of new preparation method is the main research point of high silicon steel core.In this paper,FeSi/SiO₂ soft magnetic composite cores with core-shell heterogeneous structure were prepared by depositing SiO₂ insulating medium on the surface of high silicon steel alloy powder using fluidized gas-phase in-situ deposition technique,combined with electrically pressurized sintering technique.The effect of Ar dilution gas flow rate on the microscopic morphology of FeSi/SiO₂ soft magnetic composite powder was proposed.The effect of different dilution gas flow rates,deposition times and precursor concentrations on the SiO₂ insulating medium inside the FeSi/SiO₂ soft magnetic composite core was systematically investigated.The quantitative relationships between the deposition time,precursor concentration and the saturation magnetization strength M_s,resistivityρand eddy current loss P_eddy of FeSi/SiO₂ soft magnetic composite core were described based on the experimental data with the thickness of the SiO₂ insulating medium layer as the intermediate variable,and the controlled preparation of FeSi/SiO₂ soft magnetic composite core under a single process parameter.composite cores under a single process parameter.The results show that the microscopic characteristics of SiO₂ deposited on the surface of high silicon steel substrate powder during the fluidised vapour phase in-situ deposition process increase from 125m L/min to 350m L/min with the increase of the Ar dilution gas flow rate as follows:"submicron SiO₂ clusters→incomplete SiO₂ layer→complete SiO₂ insulating layer→porous SiO₂ film".The saturation magnetization strength of FeSi/SiO₂ soft magnetic composite cores first decreases and then increases.The core loss shows the opposite trend.The lowest iron loss of 215.7W/kg was achieved at an Ar dilution gas flow rate of 250m L/min.The crystal structure of the amorphous SiO₂ insulating coating was transformed into a hexagonal crystal system ofβ-square quartz structure during the electrically pressurised sintering process,but did not affect the crystal structure of high silicon steel alloy particles.And the crystal structures of FeSi/SiO₂ composite powder and soft magnetic composites were schematically plotted by refinement of XRD data with Fullprof and Vesta software.The thickness of the SiO₂ insulation layer in FeSi/SiO₂ soft magnetic composite cores is linearly related to the deposition time and the concentration of the gas-phase precursor as the deposition time and the concentration of the gas-phase precursor increase.concentration increases linearly.On the basis of experimental and theoretical results,the resistivity and eddy current losses of FeSi/SiO₂ soft magnetic composite cores are cubic with respect to deposition time,using the thickness of the SiO₂insulation layer as an intermediate variable and based on a simplified unit resistance model and Bertotti’s classical theory.Based on the simplified unit resistance model,the cubic of the gas phase precursor concentration is proportional to the resistivity and eddy current loss.The results of this paper provide a basis for the efficient and controllable preparation of FeSi/SiO₂ soft magnetic composite cores and provide some basis for the improvement of the fluidised vapour phase in-situ deposition technology.The relational equation can be used to predict the corresponding magnetic properties of soft magnetic composite cores,providing important information for the subsequent development and research of the production control system for FeSi/SiO₂ soft magnetic composite cores.