MANUFACTURING METHOD OF GRAIN-ORIENTED SILICON STEEL SHEET, AND ITS CONTINUOUS DECARBURIZING-NITRIDING ANNEALING APPARATUS

摘要

PPROBLEM TO BE SOLVED: To provide the manufacturing method of a grain-oriented silicon steel sheet for feeding atmospheric gas at a low cost and attaining highly stabilized film performance and magnetism, and its continuous decarburizing-nitriding annealing apparatus. PSOLUTION: In the manufacturing method of the grain-oriented silicon steel sheet and its continuous decarburizing-nitriding annealing apparatus with which a cold-rolled steel sheet of the predetermined thickness containing Si of 2.0-4.8% is subjected to primary recrystallization annealing and nitriding annealing including a decarburizing step, and further subjected to finish annealing by coating an annealing separation material, atmospheric gas is collected from a nitriding zone performing the nitriding annealing or an atmospheric partition before and behind the nitriding zone and dehydrated to produce re-generated atmospheric gas mainly composed of HSB2/SBand inert gas and containing, by volume, 1% NHSB3/SB(in terms of dry gas). The component of the re-generated atmosphere gas is adjusted by adding inert gas, NHSB3/SBand HSB2/SBO to the re-generated gas so that the atmosphere of the nitriding zone after the feed contains, by volume, 25% (in terms of dry gas) HSB2/SBconcentration, 0.1-10% (in terms of dry gas) NHSB3/SB, with the dew point being 10C, and the balance inert gas, and then the re-generated atmospheric gas is supplied to the nitrizing zone. PCOPYRIGHT: (C)2009,JPO&INPIT