PRODUCTION OF GRAIN-ORIENTED SILICON STEEL SHEET

PURPOSE:To produce a grain-oriented silicon steel sheet excellent in magnetic properties by subjecting a dead soft high silicon steel slab to hot rolling and annealing, thereafter subjecting it to cold rolling to regulate its sheet thickness into a final one and successively executing primary recrystallization annealing, nitriding treatment and final finish annealing. CONSTITUTION:The dead soft high silicon steel slab having a compsn. contg., by weight, 0.0005 to 0.004% C, 2.0 to 4.5% Si, 0.010 to 0.080% acid soluble Al, 0.001 to 0.020% N, 0.0020 to 0.060% S and 0.01 to 0.1% Sn, and the balance Fe is subjected to rough rolling at 1000 to 1200 deg.C, then is annealed in the temp. range of 780 to 1100 deg.C for about 2min after the completion of finish hot rolling. Next, the hot rolled sheet is subjected to pickling treatment, and is thereafter subjected to cold rolling to regulate its sheet thickness into a final thickness of about 0.30mm, which is heated at 800 to 1200 deg.C for 1 to 200sec, is subjected to primary recrystallization annealing and is subsequently subjected to nitriding treatment in a gaseous mixture of NH3+H2 to regulate the N2 content into 150 to 1500ppm. Finally, it is coated with a separation agent for annealing of MgO series and is subjected to finish annealing at >=800 deg.C as secondary recrystallization annealing.