INNER CASE FOR FINISH ANNEALING OF GRAIN-ORIENTED ELECTRICAL STEEL SHEET, AND FINISH ANNEALING METHOD

• Main Authors: FUKUDA HIROYUKI, SHIDARA EITARO, OKADA NORIHISA, NAKADA NAOKI, NARA MASAKATSU
• Format: Patent
• Language: English
• Published: 12.11.2012
• Subjects: CHEMISTRY; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS

PROBLEM TO BE SOLVED: To provide an inner case for finish annealing that improves inhomogeneous distribution of temperature at each position in a coil generated when performing finish annealing of a grain-oriented electrical steel sheet and effectively suppresses shape defects and iron loss deterioration, and to provide a finish annealing method using the inner case.SOLUTION: The inner case for finish annealing is provided, which covers an upended coil when performing finish annealing of a stock coil of a grain-oriented electrical steel sheet in a batch-wise box-type annealing furnace. The inner case includes a cylindrical recess of dual tube structure in which an outer tube opposed to the inner periphery of the coil and an inner tube inside the outer tube are disposed, in the upper central part of the inner case. Preferably, the outer diameter of the outer tube in the cylindrical recess is 0.3 times or more smaller than the inner diameter of the coil, the distance between the outer tube and the inner periphery of the coil is 50 mm or more, and the inner cross-sectional area of the inner tube in the cylindrical recess is 0.3-0.7 times smaller than the inner cross-sectional area of the cylindrical recess.