PURPOSE: To stably produce a grain-oriented silicon steel sheet with high magnetic flux density at a low cost by hot-rolling a slab of a silicon steel having a specific composition consisting of C, Si, Mn, S, Al, N, and Fe at low temp., carrying out nitriding annealing, and then performing final cold rolling.
CONSTITUTION: A slab of a silicon steel which has a composition consisting of, by weight, 0.025-0.095% C, 2.0-4.0% Si, 0.08-0.45% Mn, ≤0.012% S, 0.010-0.060% Al, 0.0030-0.0130% N, and the balance Fe with inevitable impurities and further containing, if necessary, either or both of 0.005-0.050% P and 0.05-0.25% Cr and/or ≤1.5% of one or more elements among Mo, V, Nb, Sb, Sn, Ti, Te, and B is heated up to ≤1200°C and hot-rolled. The resulting hot rolled plate is subjected, in an as-hot-rolled state or in an annealed state, to cold rolling once or is cold-rolled twice or more, while process-annealed between the cold rolling stages, and then, the resulting cold rolled sheet is subjected to decarburizing annealing and finish annealing. At this time, in the course of the process annealing before the final cold rolling, the sheet is nitrided at 600-850°C under the decomposition of nitrogen compound gas for a time as short as <2min, by which an inhibitor composed principally of (Al, Si)N is formed.
KONDO YASUMITSU
MISHIMA YOUICHI
KOBAYASHI TAKASHI
YATSUGAYO KENICHI
