Effects of Boric Acid and Ammonium Tungstate Additions on the Chromium-free Insulating Coating of Grain-oriented Silicon Steel
YANG Hao1, WANG Cheng1, XIAO Xiaobo1, WANG Chen1, CHEN Junfeng1, WANG Bingshu1, ZHANG Weilin2, CUI Xigui3
1 College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China 2 New Wanxin (Fujian) Precision Sheet Co., Ltd., Putian 351200, China 3 School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
Abstract: The effects of boric acid and ammonium tungstate on the microstructure and properties of chromium-free insulating coatings for grain-oriented silicon steel were studied. It is shown that the wettability of coating solution can be significantly improved by the properly combined additions of boric acid and ammonium tungstate in the chromium-free phosphate coating solution. The coating surface becomes more compact and smooth, and the bonding quality between the insulating coating and the steel substrate is better. The best comprehensive properties can be obtained in the steel coated with the solution containing 2.0wt% boric acid and 0.5wt% ammonium tungstate. The lamination factor is 98.2%, the core loss P17/50 is 1.155 W·kg-1, the magnetic induction intensity B8 is 1.876 T and the interlamination resistance is 19 366 Ω·mm2. Furthermore, the improvements of the moisture resistance of coating and the corrosion resistance of grain-oriented silicon steel can also be observed.
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