PURPOSE: To produce a 'Permalloy(R)' excellent in impedance relative magnetic permeability by subjecting a sheet of 'Permalloy(R)' containing specific amounts of Mo or further Cu to magnetic annealing and to rapid cooling under respective ly specified conditions.
CONSTITUTION: An ingot of a 'Permalloy(R)' which has a composition consisting of, by weight, 75-85% Ni, 4-6% Mo, and the balance Fe or further containing 4-6% Cu is hot-rolled, or a molten 'Permalloy(R)' is formed into a sheet by a direct continuous casting process. After hot rolled sheet annealing is done at ≥900°C, metal oxides are removed from the surface. This 'Permalloy(R)' sheet is cold-rolled once or cold-rolled twice or more while process-annealed between the cold rolling stages and worked to the final sheet thickness. Then, a separation agent at annealing, such as alcohol slurry of alumina, is applied and magnetic annealing is done in a hydrogen-containing atmosphere at ≥1000°C. The cooling rate in the range between 600 and 300°C in the latter stage of this annealing is controlled to (100 to 400)°C/hr, by which the 'Permalloy(R)' sheet excellent in magnetic properties, particularly in impedance relative magnetic permeability, can be produced.
Kenzo Iwayama
Sumitomo Hidehiko
Toshihiro Shimizu
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