GRAIN-ORIENTED MAGNETIC STEEL SHEET WITH EXTREMELY HIGH MAGNETIC PROPERTY AND PROCESS FOR PRODUCING THE SAME

摘要

A grain-oriented magnetic steel slab comprising given components is re-heated at a temperature which is 1,280°C or higher and is not lower than the solid-solution-forming temperature of an inhibitor, hot-rolled, annealed, cold-rolled, annealed with decarburization, nitrided in the state of running as a strip, coated with an annealing separating agent, and subjected to finish annealing. In this process, the hot rolling is conducted so that the proportion of nitrogen precipitated as AlN is 20% or lower based on all nitrogen and the average diameter of primary particles formed by recrystallization is in the range of 7-20 µm, excluding 20 µm. Furthermore, the nitriding is conducted so as to result in a nitrogen increase ?N within the range shown by the relationship (1) and in nitrogen contents in parts located in 20% thickness positions on each side of the steel sheet, sN1 and sN2 (front and back; mass%), within the range shown by the relationship (2). 0.007-([N]-14/48 × [Ti]) = ?N = [solAl] × 14/27-([N]-14/48 × [Ti])+0.0025 relationship (1) |sN1-sN2|/?N=0.35 relationship (2)