Process for Producing Magnetic Powder and Process for Producing Dust Core

Abstract

A process for producing a magnetic powder which is sufficiently reduced in core losses such as iron loss and hysteresis loss and has sufficient strength; and a process for producing a dust core. The process for magnetic powder production comprises using a magnetic-material powder produced by water atomization as a raw powder and subjecting the powder to spheroidizing in which a mechanical impact is applied to the powder to spheroidize the powder particles. After the spheroidizing, the powder is subjected to a grain enlarging treatment in which the powder is annealed at a temperature not lower than the austenite transformation point. The process for dust core production comprises compacting the magnetic powder thus produced.

1 . A method of producing magnetic powder by a water atomizing method, wherein
 the magnetic powder produced by water atomization is used as raw powder,   a spheroidization treatment is performed by applying mechanical impact on the powder to spheroidize a shape of the powder, and   after the spheroidization treatment, a grain enlarging and decarburizing treatment is performed by annealing the powder at a temperature equal to or higher than an austenite transformation point to enlarge grains and reduce an amount of carbon.   
     
     
         2 . The method producing magnetic powder according to  claim 1 , wherein
 a coating treatment is performed by coating silicone resin on a surface of the powder to form a silicon oxide layer after the grain enlarging and decarburizing treatment.   
     
     
         3 . A method of producing a dust core by compacting magnetic powder, wherein
 the magnetic powder produced by water atomization is used as raw powder,   a spheroidization treatment is performed by applying mechanical impact on the powder to spheroidize a shape of the powder, and   after the spheroidization treatment but before compacting, a grain enlarging and decarburizing treatment is performed by annealing the powder at a temperature equal to or higher than an austenite transformation point to enlarge grains and reduce an amount of carbon.   
     
     
         4 . The method producing magnetic powder according to  claim 3 , wherein
 a coating treatment is performed by coating silicone resin on a surface of the powder to form a silicon oxide layer after the grain enlarging and decarburizing treatment but before the compacting.