Research On Effect Of Ball Scribing On Magnetic Properties Of Fe-3%Si Grain-oriented Silicon Steel

Grain-oriented silicon steel is a significant soft magnetic material with excellent magnetic properties, which is also an essential raw material to manufacture transformers and magnetic shielding apparatus, and it is widely applied in electrical, electronics and other related industries. The magnetic properties of grain-oriented silicon steel have attracted attention of experts and scholars. Ball scribing method is a method developed by the European Silicon Steel Corporation, which not only overcomes the shortcomings of the destruction of the insulating layer as a kind of mechanical scribing, but also achieving the desired scribing effect. The effect of ball scribing on magnetic properties of grain-oriented silicon steel directly determines its wide applications. Effect of ball scribing on magnetic properties of Fe-3%Si grain-oriented silicon steel was studied in this thesis, and revised relation models among parameters of magnetic domain, scribing width and iron loss were built. Effect of ball scribing on permeability, coercive force and magnetic shielding was analyzed, and effect of ball scribing, insulation layer and stress on Barkhausen noise was also studied. The main work and research results of this thesis are as follows:(1) Standard Epstein grain-oriented silicon steel samples were magnetized along different directions, and magnetization parameters were obtained and studied. The parabolic and hybrid models were built based on the traditional oval model, and permeability of conventional grain-oriented silicon steel BCl and high penneability grain-oriented silicon steel BH1 were simulated with sectional fitting respectively, and the simulation results of BCl and BH1 grain-oriented silicon steel coincide well with measured results.(2) The magnetic field strength and the magnetic flux density were expanded respectively according to the Fourier series, and the magnetic hysteresis loop model of Fe-3% Si grain-oriented silicon steel was built. The fixed angle method and the least squares method were applied to calculate the undetermined parameters, which achieves high fitting degree.(3) Effect of ball scribing on iron loss of Fe-3%Si grain-oriented silicon steel was researched. Iron loss reduction was illustrated from the respective of the magnetic domain energy. Relationship among iron loss and parameters such as domain width and scribing width was rederived and optimum scribing width was verified, and the calculation method of poptimum scribing width was obtained. Iron loss of grain-oriented silicon steel was separated into three parts, hysteresis loss, eddy current loss and abnormal loss, and their proportions were calculated, the effect of ball scribing on them were also analyzed.(4) Effect of ball scribing on magnetic permeability of Fe-3%Si grain-oriented silicon steel was studied, and variation of magnetic permeability with magnetic induction was analyzed from the perspective of filling of magnetic field lines. Magnetic shielding efficiency of silicon steel was analyzed, the reflection loss, absorption loss, internal multi-reflection loss were illustrated respectively. Ball scribing can significantly increase the permeability and the magnetic shielding efficiency of grain-oriented silicon steel. Meanwhile, ball scribing could decrease coercive force of the silicon steel. The skin depth of silicon steel descended apparently after ball scribing, and skin depth of conventional grain-oriented silicon steel CC1 dropped obviously, and that of high permeability grain-oriented silicon steel CHI gradually descended while the flux density is above 0.2 T.(5) Effect of ball scribing on Barkhausen noise of Fe-3%Si grain-oriented silicon steel was researched. After ball scribing Barkhausen noise of conventional grain-oriented silicon steel CC1 increased significantly, while Barkhausen noise value of high permeability silicon steel CHI declined sharply. A linear relationship between Barkhausen noise and iron loss was fitted, and the fitting degree is high. According to the relationship between Barkhausen noise and iron loss value, a non-destructive testing method was proposed. The non-destructive testing method possesses advantages of high precision, good linear fitting degree and being easy to implement. Effect of surface coating and tensile stress on Barkhausen noise was also studied, and coating removal leads to increase of Barkhausen noise of CC1 and CHI grain-oriented silicon steel. Domain wall movement velocity was calculated, and relevance of iron loss and Barkhausen noise was confirmed.