Patent ID: 7166171
Filing Date: 2007-01-23
Classification: B22F,C22C,H01F

Abstract:
1. A longitudinal magnetic field compacting method for manufacturing a rare earth magnet in the shape of a butterfly for use in VCM of HDD or DVD, a disk or coin for use in coreless motors, and a block for linear motors, comprising the following steps of: melting an alloy including 27–36 wt % RE/59–73 wt % Fe/0–5 wt % TM/0–2 wt % B by a vacuum induction heating process, to obtain a molten alloy, which is then subjected to a strip casting process or a chill mold casting process, to prepare an alloy ingot; hydrogenating the alloy ingot in a range of room temperature to 200° C. to increase pulverizability of the alloy ingot; pulverizing the alloy ingot by means of a jet mill, an attritor mill, a ball mill or a vibration mill, to prepare rare earth powders having a particle size of 2–6 μm; applying a pulse magnetic field to the rare earth powders so that the rare earth powders are oriented in a direction of an applied magnetic field and subjected to a longitudinal magnetic field compacting, based on the principle that a magnetic material is attracted to a center of a magnetic field coil by the pulse magnetic field, to form a compacted body; sintering the compacted body at 1000–1100° C. in a vacuo or argon atmosphere, to prepare a sintered body; and heat-treating the sintered body at 400–900° C., thereby obtaining a rare earth magnet.