Compact, method for producing compact, reactor, converter, and power conversion device

Abstract

A low-loss compact and a method for producing the compact are provided. A method for producing a compact by using coated soft magnetic powder that includes coated soft magnetic particles constituted by soft magnetic particles and insulating coatings coating outer peripheries of the soft magnetic particles includes a raw material preparation step and an irradiation step. In the raw material preparation step, a raw compact is prepared by press-forming coated soft magnetic powder. In the irradiation step, part of a surface of the raw compact is irradiated with a laser. Irradiating a part of a surface of a raw compact with laser increases the number of disrupted portions of conductive portions where constituent materials of the soft magnetic particles at the surface of the raw compact have become conductive to each other, and the loss of the compact can be decreased.

1 . A compact produced by press-forming coated soft magnetic powder that includes a plurality of coated soft magnetic particles constituted by soft magnetic particles and insulating coatings coating outer peripheries of the soft magnetic particles,
 wherein an oxide film containing iron is present in at least part of a surface of the compact, and   when a total content of iron and oxygen in a surface portion where the oxide film is present is assumed to be 100 mass %, an oxygen content is 9 mass % or more and 20 mass % or less.   
     
     
         2 . The compact according to  claim 1 , wherein a portion in which an oxygen content is less than 6 mass % is also present in the surface of the compact. 
     
     
         3 . The compact according to  claim 1 , wherein the oxide film has a portion having a thickness of 0.1 μm or more. 
     
     
         4 . The compact according to  claim 1 , wherein at least part of the surface of the compact includes
 a disrupted region that electrically disrupts adjacent soft magnetic particles from each other, and   a gathered portion on a surface of the soft magnetic particle adjacent to the disrupted region, the gathered portion not bridging between the adjacent particles and being constituted by an oxide film that is thicker at a central portion than at an outer peripheral portion.   
     
     
         5 . The compact according to  claim 1 , wherein at least part of the surface of the compact includes
 a disrupted region that electrically disrupts adjacent soft magnetic particles from each other, and   an aggregated portion on a surface of the soft magnetic particle adjacent to the disrupted region, the aggregated portion protruding toward an outer peripheral side of the soft magnetic particle and locally having a large thickness,   wherein the oxide film is present in at least part of the aggregated portion.   
     
     
         6 . The compact according to  claim 5 , wherein the oxide film in the aggregated portion includes a portion that has a thickness of 0.5 μm or more. 
     
     
         7 . The compact according to  claim 1 , wherein the oxide film contains at least one selected from FeO, α-Fe 2 O 3 , γ-Fe 2 O 3 , and Fe 3 O 4 . 
     
     
         8 . The compact according to  claim 1 , wherein a density d of the compact is 7.0 g/cm 3  or more. 
     
     
         9 . The compact according to  claim 1 , wherein the soft magnetic particles are composed of iron having a purity of 99 mass % or higher. 
     
     
         10 . A method for producing a compact by using coated soft magnetic powder that includes a plurality of coated soft magnetic particles constituted by soft magnetic particles and insulating coatings coating outer peripheries of the soft magnetic particles, the method comprising:
 a raw material preparation step of preparing a raw compact by press-forming the coated soft magnetic powder; and   an irradiation step of irradiating at least part of a surface of the raw compact with a laser.   
     
     
         11 . The method for producing a compact according to  claim 10 , wherein the irradiation step is performed on at least part of a surface of the raw compact, the surface being a surface that have come into sliding contact with a die. 
     
     
         12 . The method for producing a compact according to  claim 10 , wherein the irradiation step is performed on a surface of the raw compact, the surface being a surface that serves as at least part of a parallel surface parallel to a direction of a magnetic flux generated by excitation using the compact as a magnetic core. 
     
     
         13 . The method for producing a compact according to  claim 12 , wherein the irradiation step is performed on a surface of the raw compact, the surface being the parallel surface, and in a region that extends across the entire length of the compact in the direction of the magnetic flux. 
     
     
         14 . The method for producing a compact according to  claim 10 , wherein the laser is one type of laser selected from a YAG laser, a YVO 4  laser, and a fiber laser. 
     
     
         15 . The method for producing a compact according to  claim 10  wherein a wavelength of the laser is in a wavelength absorption range of the soft magnetic particles. 
     
     
         16 . The method for producing a compact according to  claim 10 , wherein, when an average output of the laser is P (W) and an irradiation area of the laser is S (mm 2 ), an energy density U (W/mm 2 )=P/S of the laser satisfies 37.0≦U≦450.0. 
     
     
         17 . The method for producing a compact according to  claim 10 , wherein a ratio of an irradiation interval to a beam diameter of the laser is 0.35 or less. 
     
     
         18 . The method for producing a compact according to  claim 10 , wherein the number of times of laser overlap is 5 or more. 
     
     
         19 . A compact produced by the method for producing a compact according to  claim 10 . 
     
     
         20 . A reactor comprising a coil formed by winding a wire and a magnetic core that is arranged on an outer side and an inner side of the coil and forms a closed magnetic circuit,
 wherein at least part of the magnetic core is formed of a compact, and   the compact is the compact according to  claim 1 .   
     
     
         21 . A converter comprising a switching element, a drive circuit configured to control operation of the switching element, and a reactor configured to smoothen the operation of the switching element, the converter converting an input voltage by operation of the switching element,
 wherein the reactor is the reactor according to  claim 20 .   
     
     
         22 . A power conversion device comprising a converter configured to covert an input voltage and an inverter that is connected to the converter and performs conversion between DC and AC, the power conversion device being configured to drive a load by using power converted by the inverter,
 wherein the converter is the converter according to  claim 21 .