Effects of Sodium Tungstate on Properties of Insulation Coating for Grain-oriented Silicon Steel

The effect of sodium tungstate in insulation coating solution of grain-oriented silicon steel on the microstructure and properties of the prepared phosphate insulation coating was investigated by using scanning electron microscopy (SEM) , Epstein square, insulating resistance tester and Fourier transform infrared spectrum (FTIR) et al. The results show that, with the gradually increasing content of sodium tungstate in the coating solution, the wetting angle between the coating solution and the grain-oriented silicon steel substrate first decreases and then increases; the interlamination resistance, lamination factor and magnetism induction intensity of grain-oriented silicon steel first increase and then decrease, the iron loss first decreases and then increases. When the sodium tungstate content is 2. 0%(mass fraction) , the coating solution shows the best wettability on the grain-oriented silicon steel substrate, the wetting angle is 39. 3 degrees; at the same time, the formed insulation coating is dense and smooth, there is a diffusion area about 0. 8 mu m at the junction between the insulation coating and the magnesium silicate bottom layer, furthermore, the humidity resistance of the insulation coating is not significantly changed; the interlamination resistance, lamination factor, magnetism induction intensity and iron loss of grain-oriented silicon steel reach the optimal values, which are 14073 Omega . mm(2), 97. 0%, 1. 893T and 1. 051W . kg(-1), respectively.