Improvements in or relating to methods of manufacturing permanent magnets and permanent magnets manufactured by carrying out these methods

摘要

783,237. Magnetic compositions. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Dec. 16, 1955 [Dec. 21, 1954], No. 36158/55. Class 38 (2). An anisotropic permanent magnet having a (BH) max value exceeding 1.5 x 10SP6/SP gaussoersted, and comprising simple or mixed crystals of M x Ca( 1-x ) O, 6Fe 2 O 3 where M is one or more of Ba, Sr and Pb and 0.6#x#1, is made of suspending the powdered crystal in an inert liquid, removing the liquid whilst applying a magnetic field, granulating the residue, moulding into the required shape in a magnetic field and sintering it between 1100‹ and 1400‹ C. BaCO 3 and Fe 2 O 3 are mixed in the ratio 1.1 ; 6 mol., compressed into blocks, sintered for 15 minutes at 1280‹ C., cooled, powdered and suspended in water after the addition of 1 per cent by weight of CaCO 3 . The water is removed by filtering in a magnetic field, dried, and pressed through a 2 X 2 mm. sieve. The powder is compressed in a magnetic field and sintered for 5 minutes at 1250‹ C. In a modification, the powder obtained by pressing through a 1 X 1 mm. sieve is sprayed with 2 per cent by weight solution of camphor in alcohol before compressing in a magnetic field and firing. The camphor binds the grains together without increasing the friction during moulding. Paraffin may be substituted for camphor. Specification 747,724 is referred to.