| 摘要 |
PURPOSE:To form a good forsterite insulation coating composed of oxidation film containing greater SiO2 content compared with usual method and a least fayalite, by decarbonizing and annealing applying metal sulfate water solution on both faces of directional silicon steel sheets. CONSTITUTION:Sulphate water solution of metals containing one kind or more of Fe, Co, Ni, Cr, Zn, Mg, Mn, Al, is applied on the directional silicon steel sheets rolling at the last sheet thickness. Next, the above sheets are dried and used weight per unit area of sulphate is made 0.1-1.0g/m<2> in drying condition. Then, applied and dried sheets are decarbonized and annealed in wet hydrogen at 700-900 deg.C successively and oxidation film mainly composed of SiO2 and fayalite (Fe2SiO4), having used weight per unit area of oxygen of 1.0-2.0g/m<2>, is formed. Further, decarbonized and annealed sheets are rolled around a coil after applying annealing separation agent mainly composed of MgO having hydration quantity of 1-4%. Then, constant temperature of secondary recrystallization is kept in the above condition and moreover, desired forsterite insulati coating is formed on the sheets carrying out a high temperature hydrogen annealing at 1100-1200 deg.C. |
