| 摘要 |
PURPOSE: Provided is a method for manufacturing oriented electrical steel sheets having superior punchability where a tension coating agent is applied on the surface of steel sheet free of glass film to micronize magnetized grain size and then organic/inorganic complex coating solution is applied thereon for increasing punchability. CONSTITUTION: The oriented electrical steel sheets having superior punchability is manufactured by reheating a steel slab comprising Si 2.9-3.4wt.%, C 0.045-0.062wt.%, P 0.020wt.% or less, sol-Al 0.022-0.032wt.%, N 0.006-0.009wt.%, S 0.010wt.% or less, Mn 0.08-0.12wt.% or less, Cu 0.012-0.021wt.% or less, a balance of Fe, and other inevitable impurities within the temperature range of 1150 to 1200deg.C; hot rolling the steel slab to 2.0-2.3mm; annealing the hot rolled steel sheet at below 1100deg.C; pickling; cold rolling to 0.35mm; simultaneous decarburization/nitriding under wet ammonia contained hydrogen/nitrogen gas mixture atmospheric condition of 840-890deg.C; applying slurry phase of fusion preventing agent comprising MgO, alumina-sol, and MgCl2; drying it at below 700deg.C followed by coiling; final annealing it under 10% nitrogen contained hydrogen atmospheric condition for at least 20hrs within the temperature range of 1200 ±10deg.C after elevating temperature at a temperature elevation rate of 15°C/hr within the temperature range of 700 to 1200deg.C; and then applying insulation coating agent where a tension coating solution comprising phosphate 45-55%, colloidal silica 45-60%, anhydrous chromic acid 1.5-5% is firstly coated on the surface of the steel sheet in an amount of 1.5-3g/m2 and then a coating solution comprising acrylic resin 28-35%, magnesium dichromate 35-60%, colloidal silica 15-30% is secondly coated thereon in an amount of 0.5-1.5g/m2. Further, the amount of MgCl2 is calculated from the equation, MgCl2(%)=9.5xSiO2(g/m2)±0.4 wherein SiO2 represents SiO2 content of steel sheet.
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