DUST CORE AND PROCESS FOR PRODUCING SAME

摘要

Provided are a dust core having excellent direct-current BH characteristics and a process for producing the dust core, in which a soft-magnetic powder is prevented from sintering into a hard mass when heat-treated, and hysteresis loss can be effectively reduced. In a first mixing step, a soft-magnetic powder consisting mainly of iron is mixed with an inorganic insulating powder by means of a mixer, the amount of the insulating powder being 0.4-1.5 wt.% of the soft-magnetic powder. The mixture obtained through the first mixing step is heat-treated in a nonoxidizing atmosphere having a temperature which is 1,000ºC or higher but not higher than the temperature at which the soft-magnetic powder begins to sinter. In a binder addition step, a silane coupling agent is added in an amount of 0.1-0.5 wt.%. A binder, e.g., a silicone resin, is added in an amount of 0.5-2.0 wt.% to the soft-magnetic alloy powder to which the inorganic insulating powder has been adhered with the silane coupling agent, and the particles of the soft-magnetic alloy powder are bonded to one another to form granules. Thereafter, a lubricating resin is mixed therewith, and the mixture is press-molded to obtain a molded object. In an annealing step, the molded object is annealed in a nonoxidizing atmosphere.