JP2011231364A - Method of producing powder for dust core, dust core using powder for dust core produced by the method of producing powder for dust core, and apparatus for producing powder for dust core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing powder for dust cores for preventing production of a secondary particle in siliconizing treatment and for increasing quality and productivity of powder for dust cores; to provide a dust core using powder for dust cores produced by the method of producing powder for dust cores; and to provide an apparatus for producing powder for dust cores.SOLUTION: In the method of producing powder for dust cores for producing powder for dust cores, powder for siliconizing including a prescribed amount of soft magnetic metal powder 21 and a prescribed amount of silicon dioxide 22 is heated for a prescribed treatment time within a furnace 2, and a silicon-penetrated layer is formed on a surface of the soft magnetic metal powder 21, thus dividing a prescribed amount of powder for siliconizing along a time base for adding to the furnace 2 while the furnace 2 is heated and rotated simultaneously.

Description

  The present invention relates to a method for producing a powder for a powder magnetic core, a powder magnetic core using the powder for a powder magnetic core produced by the method for producing the powder for a powder magnetic core, and a powder production apparatus for the powder magnetic core.

  The dust core is obtained by press-molding a dust core powder made of soft magnetic metal powder. Compared to the core material made by laminating electromagnetic steel sheets, the dust core has magnetic properties with less high frequency loss (hereinafter referred to as “iron loss”) depending on the frequency, and is suitable for shape variations. It has many advantages such as being able to cope with low cost and low material cost. Such a powder magnetic core is applied to, for example, a stator core and a rotor core of a vehicle drive motor, a reactor core constituting a power conversion circuit, and the like.

  For example, as shown in FIG. 16, the powder 101 for the powder magnetic core allows the silicon dioxide powder 103 to permeate and diffuse from the surface of the iron powder 102, thereby forming a silicon permeation layer 104 in which the silicon element is concentrated on the surface layer of the iron powder 102. The siliconization process to be performed is performed. In the siliconization treatment, the iron powder 102 and the silicon dioxide powder 103 are stirred and mixed to adhere the silicon dioxide powder 103 to the surface of the iron powder 102, and the mixed powder of the iron powder 102 and the silicon dioxide powder 103 is put into a furnace. Then, the mixed powder is heated to 1000 ° C. Then, the silicon element is detached from the silicon dioxide powder 103 and permeates and diffuses into the surface layer of the iron powder 102 to form the silicon permeation layer 104.

  When the silicon element is infiltrated to the center of the iron powder 102, the hardness of the powder 101 for dust core becomes high. In this case, when the dust core powder 101 is pressed and compacted, the dust core powder 101 is not deformed and the gap formed between the dust core powders 101 becomes larger. Density decreases. When the magnetic core density is low, there is a problem that the magnetic flux density is lowered. Therefore, it is preferable that the silicon permeation layer 104 has a distance X2 from the surface of the iron powder 102 to the center of the iron powder 102 that is less than 0.15 times the diameter D of the iron powder 102. However, if the silicon permeation layer 104 is thin or the silicon element concentration in the silicon permeation layer 104 is low, the contact portion of the iron powder 102 cannot be sufficiently insulated, and iron loss (mainly hysteresis loss and eddy current loss) is caused. Get higher. Therefore, the distance X2 and the concentration of the silicon permeation layer 104 formed on the powder 101 for dust core are very important in managing the specific resistance of the dust core (see, for example, Patent Document 1 and Patent Document 2). .

JP 2009-256750 A JP 2009-123774 A

  However, as shown in FIG. 17, the conventional method for manufacturing a powder for a powder magnetic core is to randomly extract 10 powders 101 for a powder magnetic core, and the silicon-penetrating layer 104 is iron from the surface of the iron powder 102. When the distance (distance from the surface) X2 formed toward the center of the powder 102 and the concentration of silicon element (Si concentration) in the silicon permeation layer were measured, the distance X2 from the surface and the Si concentration were between the powders. There was a lot of variation. Specifically, the extracted powder contained a powder having a poor silicification reaction (a powder having a low silicidation reaction amount) (see the graph described by a thin solid line in FIG. 17). Further, even if the powder is rich in the silicification reaction (powder having a high silicidation reaction amount) (see the graph described by the thick solid line in FIG. 17), the Si concentration on the surface of the iron powder 102 is about 2.0. The distance (thickness) X2 from the surface of the iron powder 102 of the silicon permeation layer 104 varies from about 4 μm to about 20 μm. Furthermore, the ratio of the Si concentration decreasing from the surface of the iron powder 102 of the silicon-penetrating layer 104 toward the center of the iron powder 102 varies greatly in the powder rich in the silicon immersion reaction. Therefore, in the conventional method for producing a powder for a powder magnetic core, it is not possible to cause each iron powder 102 to undergo a uniform silicidation reaction, and the silicon permeation layer 104 formed in each powder for a powder magnetic core 101 is made uniform. I couldn't plan. Therefore, when a portion having a small thickness (distance from the surface) X2 or a portion having a low Si concentration of the silicon permeation layer 104 formed on the powder 101 for dust core is in contact with each other at the time of compacting, insulation of the contact portion is performed. Therefore, there is a problem that the eddy current generated in the dust core becomes large and the specific resistance becomes low. Moreover, the powder 101 for a dust core having a large thickness (distance from the surface) X2 of the silicon-penetrating layer 104 is hard and causes a decrease in the core density and magnetic flux density.

  The reason why the thickness (distance from the surface) X2 and the Si concentration of the silicon-penetrating layer 104 varies between the powders 101 for powder magnetic cores by the conventional method for producing powders for powder magnetic cores is as follows. Because the mixed powder was heated without rotating the furnace to which the mixed powder was supplied, the arrangement of the iron powder 102 and the silicon dioxide powder 103 did not change during the siliconization treatment, and there were many silicon dioxide powders 103 around In the iron powder 102, a large amount of silicon element penetrates and diffuses into the surface layer, and the thickness and the Si concentration of the silicon infiltrated layer 104 increase. This is considered to be because the amount permeating and diffusing into the silicon is small, and the thickness and the Si concentration of the silicon-permeable layer 104 are small.

  Therefore, as shown in FIG. 19, the inventors supply mixed powder obtained by stirring and mixing iron powder 102 having an average particle diameter of 200 μm and silicon dioxide powder 103 having an average particle diameter of 50 nm to a furnace 105, and then heating the furnace 105 with a heater. The powder for a magnetic core is manufactured by heating at 106 and then stirring the mixed powder continuously for 1 hour by rotating the furnace 105 while adjusting the internal temperature of the furnace 105 to 1000 ° C. Tried. As a result, the inventors believe that the silicon dioxide powder 103 is uniformly attached around the iron powder 102 while changing the arrangement during the silicidation treatment, and a uniform silicification reaction can be generated in each iron powder 102. It was.

  However, when the above method for producing a powder for a powder magnetic core was carried out and the product was taken out from the furnace 105, as shown in FIG. It had become. The secondary particles 110 were sintered with silicon dioxide powder 103 (see dot portion) to combine a plurality of iron powders 102, and the diameters ranged from 600 μm to 700 μm. The reason why the secondary particles 110 are formed is considered as follows.

  It is known that sintering begins at a temperature of about two-thirds of the melting point. The melting point of silicon dioxide is 1600 ° C. ± 75 ° C. On the other hand, the heating temperature of the mixed powder during the siliconizing treatment is about 1000 ° C. Accordingly, the heating temperature of the mixed powder of 1000 ° C. corresponds to a temperature that is about two thirds of the melting point of silicon dioxide. By heating the mixed powder to 1000 ° C., silicon element is detached from the silicon dioxide powder 103 adhering to the surface of the iron powder 102 and diffuses and penetrates into the iron powder 102. The material moves and sintering occurs. Sintering also occurs in the silicon dioxide powder 103 that is diffusion bonded to the surface of the iron powder 102, so that the iron powders 102 are bonded together via the sintered silicon dioxide powder 103. In particular, as shown in FIG. 19, the method for producing a powder for a powder magnetic core is to mix the iron powder 102 and the silicon dioxide powder 103 by continuously rotating the furnace 105 for 1 hour while the mixed powder is heated to 1000 ° C. Agitate by repeatedly dropping the powder from high to low. In this case, the silicon dioxide powder 103 in the low place is compressed by the weight of the mixed powder falling from above, and the sintering is promoted. As described above, when the mixed powder is simply stirred while being heated to 1000 ° C. during the siliconization treatment, the silicon dioxide powder 103 is pressure-sintered to generate secondary particles 110. As a result, the quality and productivity of the powder for powder magnetic cores have deteriorated.

  The present invention has been made to solve the above-mentioned problems, and prevents the generation of secondary particles during the siliconization treatment, and improves the quality and productivity of the powder for powder magnetic core. An object of the present invention is to provide a method for producing a powder for a powder magnetic core, a powder magnetic core using the powder for a powder magnetic core produced by the method for producing a powder for a powder magnetic core, and a powder production apparatus for the powder magnetic core. .

  In order to solve the above-described problems, a method for manufacturing a powder for a powder magnetic core according to one aspect of the present invention includes a step of supplying a siliconizing powder containing a predetermined amount of soft magnetic metal powder and a predetermined amount of silicon dioxide inside a furnace. In the method for producing a powder magnetic core powder for producing a powder magnetic core powder by heating the treatment time and forming a silicon permeation layer on the surface of the soft magnetic metal powder, the furnace was rotated while being heated. In the state, there is a silicified powder addition step of adding the predetermined amount of the silicified powder along the time axis to the furnace.

  The method for producing a powder for a powder magnetic core having the above-described configuration desirably includes a sintering preventing material supplying step of supplying a sintering preventing material for preventing the sintering of the soft magnetic metal powder to the furnace.

  In the method for manufacturing a powder for a powder magnetic core having the above-described structure, in the silicon powder addition step, the predetermined amount of silicon powder is added by being sprayed and dispersed in the furnace. It is desirable to add a certain amount of siliconizing powder continuously to the furnace.

  In order to solve the above problems, a dust core according to one aspect of the present invention is obtained by filling a molding die with the powder for a dust core produced by any one of the above methods for producing a powder for a dust core. It is manufactured by pressing.

  In order to solve the above problems, a powder magnetic core manufacturing apparatus according to an aspect of the present invention includes a furnace in which a predetermined amount of siliconizing powder containing a predetermined soft magnetic metal powder and silicon dioxide powder is supplied; Heating means for heating the furnace, and a processing gas for supplying to the furnace a processing gas for accelerating the diffusion and permeation of the silicon dioxide powder into the surface of the soft magnetic metal powder by heat for heating the furnace by the heating means In a powder magnetic core powder manufacturing apparatus comprising a supply means and an exhaust means for exhausting gas from the furnace, the rotating means for rotating the furnace and the predetermined amount of the siliconized powder are divided along a time axis. A means for adding silicon powder to the furnace.

  The method for manufacturing a powder for a powder magnetic core and the powder core manufacturing apparatus for a powder magnetic core according to the above aspect are configured in such a manner that a predetermined amount of siliconized powder is divided along the time axis while being rotated while the furnace is heated. By adding, the siliconization powder is adhered to the surface of the soft magnetic metal powder, and the siliconization reaction proceeds. Since the siliconizing powder is gradually added to the furnace along the time axis, there is little siliconizing powder stirred and mixed together with the soft magnetic metal powder during the siliconizing reaction. Therefore, when the soft magnetic metal powder is mixed with stirring, the siliconizing powder is not sintered. Therefore, according to the method for manufacturing a powder for a powder magnetic core and the powder core manufacturing apparatus for a powder magnetic core according to the above aspect, secondary particles are prevented from being generated during the siliconization treatment, and the quality and production of the powder for a powder magnetic core Can be improved.

  According to the method for manufacturing a powder for a powder magnetic core having the above configuration, when the furnace supplied with the soft magnetic metal powder and the anti-sintering material is heated, the anti-sintering material prevents the soft magnetic metal powder from being sintered. Therefore, it is possible to prevent secondary particles from being generated by using the sintered soft magnetic metal powder as a nucleus.

  According to the method of manufacturing a powder for a powder magnetic core having the above-described configuration, since a predetermined amount of siliconized powder is sprayed and dispersed in the furnace, the siliconized powder is widely distributed in the furnace and supplied to the furnace. It can be uniformly attached to the surface of a fixed amount of soft magnetic metal powder.

  According to the method of manufacturing a powder for a powder magnetic core having the above-described configuration, a predetermined amount of siliconized powder is intermittently added to the furnace in a plurality of times, or a predetermined amount of siliconized powder is continuously added to the furnace. Therefore, the amount of surplus silicon powder in the furnace during the silicification reaction is small, and the generation of secondary particles can be suppressed.

  Moreover, since the powder magnetic core which concerns on the said aspect is manufactured using the powder for powder magnetic cores with sufficient quality, an iron loss can be made small.

It is a schematic block diagram of the powder manufacturing apparatus for dust cores according to the first embodiment of the present invention. It is AA sectional drawing of FIG. It is a figure explaining the manufacturing method of the powder for dust cores. It is a figure explaining a sintering prevention material supply process. It is a schematic diagram which shows the state in the furnace before injection | throwing-in silicon dioxide powder. It is a schematic diagram which shows the state in the furnace after injection | throwing-in silicon dioxide powder. It is a figure explaining silicification reaction, Comprising: The state which silicon dioxide powder adhered to the surface of iron powder is shown. It is a figure explaining silicification reaction, Comprising: The silicon dioxide powder and the iron powder are shown in the heated state. It is a figure explaining a silicon immersion reaction, Comprising: The silicon dioxide powder shows the state which carried out the diffusion joining to the surface of the iron powder. It is a figure explaining silicification reaction, Comprising: The silicon dioxide powder diffuses osmose | permeates on the surface of iron powder, The state which the following silicon dioxide powder tends to adhere to the surface of iron powder is shown. It is a schematic diagram which shows the cross section of the powder for dust cores. It is a figure which shows the conditions of an Example and a comparative example. It is a figure which shows the manufacturing method of the powder for powder magnetic cores in a comparative example. It is a figure which shows the yield rate of a comparative example and an Example. It is a graph which shows the result of having investigated the distance of the silicon osmosis | permeation layer formed toward the center part of iron powder from the surface of iron powder about the powder for powder magnetic cores of an Example according to powder for powder magnetic cores. It is an image figure of a siliconization process. It is a graph which shows the result of having investigated the distance of the silicon osmosis | permeation layer formed toward the center part of iron powder from the surface of iron powder according to the powder for powder magnetic cores. It is drawing which made the micrograph of the powder for powder magnetic cores obtained when heating mixed powder while stirring. It is a conceptual diagram of the apparatus heated while stirring mixed powder.

  Next, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
<Schematic configuration of powder manufacturing apparatus for dust core>
FIG. 1 is a schematic configuration diagram of a powder magnetic core manufacturing apparatus 1 according to the first embodiment of the present invention.
The powder manufacturing apparatus 1 for a dust core includes a furnace 2 to which a predetermined amount of carbon-iron-based metal powder 21 (an example of soft magnetic metal powder) and a predetermined amount of silicon dioxide powder 22 (an example of siliconization powder) are supplied. And a heater 3 that heats the furnace 2 (an example of a heating means) and a treatment that promotes diffusion and permeation of the silicon dioxide powder 22 on the surface of the carbon-iron-based metal powder 21 by the heat that the heater 3 heats the furnace 2. A processing gas supply means 4 for supplying gas to the furnace 2 and an exhaust means 5 for exhausting the gas from the furnace 2 are provided. Further, the powder magnetic core production apparatus 1 includes a siliconizing powder adding means 15 for adding a predetermined amount of silicon dioxide powder 22 along the time axis to the furnace 2.

2 is a cross-sectional view taken along the line AA in FIG.
The furnace 2 is formed by cylindrically molding a material having high thermal conductivity such as stainless steel. The furnace 2 is rotated about a longitudinal axis by a motor (not shown) (an example of a rotating means). A heater 3 is provided outside the furnace 2 so as to heat the furnace 2 uniformly. Three long plate-like stirring plates 6 are erected on the inner peripheral surface of the furnace 2. Each stirring plate 6 is fixed along the longitudinal direction of the furnace 2. The three stirring plates 6 are arranged at equal intervals in the circumferential direction of the cross section orthogonal to the longitudinal direction of the furnace 2. A temperature sensor 7 is fixed to the inner wall of the furnace 2 so that the internal temperature of the furnace 2 is measured.

  As shown in FIG. 1, a processing gas supply means 4 and a siliconization powder addition means 15 are connected to one end face of the furnace 2 so that the processing gas and silicon dioxide powder 22 are supplied to the furnace 2. ing. On the other hand, the exhaust means 5 is connected to the other end face of the furnace 2. Therefore, the furnace 2 is configured such that the gas is exhausted from the furnace 2 in response to the supply of the processing gas and the silicon dioxide powder 22, and the internal pressure is maintained at a predetermined pressure.

  As shown in FIG. 1, the processing gas supply means 4 includes an air supply side pipe connection portion 8 provided on one end face of the furnace 2, a cylinder 11 filled with the processing gas, and an air supply side pipe connection portion 8. And a processing gas supply pipe 12 that connects the cylinder 11 and a processing gas control valve 13 that is disposed on the processing gas supply pipe 12 and controls the supply amount of the processing gas. Here, the processing gas preferably contains at least hydrogen in order to promote the oxidation-reduction reaction between the carbon-iron-based metal powder 21 and the silicon dioxide powder 22.

  Further, the exhaust means 5 is disposed on the exhaust pipe 5a, the exhaust pipe connection 10 provided on the other end face of the furnace 2, the exhaust pipe 5a connecting the exhaust pipe connection 10 to an exhaust pump (not shown), and the exhaust pipe 5a. And an exhaust valve 5b for controlling the exhaust flow rate.

  The powder addition means 15 for siliconization includes an injection nozzle 9 fixed to one end face of the furnace 2, a storage tank 16 for storing the silicon dioxide powder 22, and a sealed box 17 in which the storage tank 16 is provided. A pressurized gas supply pipe 18 for supplying a pressurized gas to the storage tank 16, and a silicon powder feed pipe 19 for connecting the treatment tank 16 to the injection nozzle 9 and carrying the silicon dioxide powder 22 to the furnace 2. An ejection control valve 20 provided on the silicon powder delivery pipe 19 for controlling the operation of ejecting the silicon dioxide powder 22 from the ejection nozzle 9.

The sealed box 17 is filled with an inert gas such as N ₂ gas so that the internal pressure becomes higher than the external pressure. This prevents the outside air from contacting the silicon dioxide powder 22 in the storage tank 16 and altering the silicon dioxide powder 22.
Further, the pressurized gas is preferably a gas having the same component as the inert gas or the processing gas so as not to hinder the atmosphere in which the silicidation reaction in the furnace 2 is performed. In the present embodiment, the storage tank 16 and the cylinder 11 are connected by a pressurized gas supply pipe 18, and the processing gas is used as the pressurized gas.

  In such a silicon powder addition means 15, the space between the cylinder 11 and the ejection control valve 20 is constantly pressurized by a pressurized gas (processing gas). Therefore, when the ejection control valve 20 is changed from the valve closed state to the valve opened state, the silicon dioxide powder 22 in the storage tank 16 is injected into the furnace 2 from the injection nozzle 9 together with the processing gas. The injection nozzle 9 is disposed along the longitudinal axis of the furnace 2, and the ejection port 9 a is disposed on the axis of the furnace 2. This is because when the furnace 2 rotates and the mixed powder 23 is stirred and mixed, the silicon dioxide powder 22 is blown against the mixed powder 23 that falls from the top to the bottom of the furnace 2, and the carbon-iron-based metal powder 21. This is because the silicon dioxide powder 22 easily adheres to the surface.

  An air supply side pipe connection portion 8 is provided near the injection nozzle 9. Thereby, the silicon dioxide powder 22 injected from the injection nozzle 9 is carried to the position far from the outlet 9 a on the processing gas injected from the air supply side pipe connection portion 8, and reaches the entire furnace 2. Has been.

<Composition of powder for powder magnetic core>
FIG. 11 is a schematic view showing a cross section of the powder 28 for a powder magnetic core.
In the powder 26 that has been subjected to the siliconization treatment by the powder magnetic core powder manufacturing apparatus 1, a silicon permeation layer 25 having a predetermined thickness X 1 is formed on the surface of the iron powder 24. Here, the predetermined thickness X1 refers to a distance from the surface of the iron powder 24 of the silicon permeation layer 25 toward the center. The predetermined thickness X1 is desirably 0.15 times the diameter D of the iron powder 24 in order to increase the dust density and the magnetic flux density. The powder 28 for powder magnetic core has a silicone resin coating layer 27 formed by coating the surface of the powder 26 that has been subjected to siliconization treatment with a silicone resin.

<Method for producing powder for powder magnetic core>
FIG. 3 is a diagram for explaining a method for producing a powder for a powder magnetic core. FIG. 4 is a diagram for explaining a sintering preventing material supplying step. FIG. 5 is a schematic diagram showing a state in the furnace before the silicon dioxide powder is charged. FIG. 6 is a schematic diagram showing a state in the furnace after the silicon dioxide powder is charged. 7-10 is a figure explaining the silicification reaction.

A: Sintering Preventive Material Supply Step As shown in FIG. 4, a mixed powder 23 obtained by stirring and mixing a predetermined amount of carbon-iron-based metal powder 21 and a predetermined amount of sintering preventive material 31 is provided on the wall surface of the furnace 2. It is supplied to the inside of the furnace 2 from the opened opening 2a. The sintering preventing material 31 prevents the carbon-iron-based metal powder 21 from being sintered. The sintering preventing material 31 is preferably made of a material that does not easily react with the carbon-iron-based metal powder 21 and the silicon dioxide powder 22. The anti-sintering material 31 has an appearance with an average particle size larger than that of the silicon dioxide powder 22 and smaller than that of the carbon-iron-based metal powder 21. This is because the sintering preventing material 31 enters between the carbon-iron-based metal powders 21 during the rotation of the furnace 2 to facilitate separation of the carbon-iron-based metal powders 21. The anti-sintering material 31 does not inhibit the silicidation reaction of the carbon-iron-based metal powder 21, and is interposed between the carbon-iron-based metal powder 21 during the stirring and mixing of the carbon-iron-based metal powder 21. The supply amount is adjusted to prevent ligation. The mixed powder 23 may be automatically charged into the furnace 2 by, for example, a charging device, or may be manually charged into the furnace 2 by an operator. The opening 2a is opened and closed by the open / close door 2b.

  Here, the silicon dioxide powder 22 is not supplied to the furnace 2 until the furnace 2 reaches the processing temperature required for the silicidation reaction. This is because if the silicon dioxide powder 22 is put in from the beginning, the silicon dioxide powders 22 may be sintered when the furnace 2 reaches the processing temperature.

B: Temperature rising step In the powder core manufacturing apparatus 1 shown in FIG. 1, the processing gas control valve 13, the exhaust valve 5b, and the ejection control valve 20 are closed during standby. After the powder mixture 23 is charged into the furnace 2, the powder magnetic core powder manufacturing apparatus 1 switches the processing gas control valve 13 and the exhaust valve 5 b from the valve closed state to the valve opened state, and supplies the processing gas and the gas flow. Exhaust starts. And the powder manufacturing apparatus 1 for powder magnetic cores makes the heater 3 start the heating of the furnace 2. The internal temperature of the furnace 2 is monitored by a temperature sensor 7. The carbon-iron-based metal powder 21 is stirred and mixed with the sintering preventing material 31 and put into the furnace 2 together. Therefore, even if the furnace 2 reaches the processing temperature, the carbon-iron-based metal powder 21 is prevented from being sintered by the anti-sintering material 31 interposed between the other carbon-iron-based metal powders 21.

C: Silica powder addition process As shown by the solid line in FIG. 3, the internal temperature of the furnace 2 has reached a treatment temperature (silica treatment temperature) required for the silicification reaction from the measured value measured by the temperature sensor 7. If it is confirmed, the powder magnetic core production apparatus 1 starts rotating the furnace 2 by a motor (not shown). Thereby, after the mixed powder 23 in the furnace 2 is lifted from the bottom of the furnace 2 to a predetermined height by the stirring plate 6, the mixed powder 23 is repeatedly stirred and mixed by sliding down from the stirring plate 6 facing obliquely downward.
Note that the heating operation of the heater 3 is controlled so that the measured value measured by the temperature sensor 7 maintains the processing temperature while the furnace 2 is rotated.

  The powder manufacturing apparatus 1 for a powder magnetic core rotates the furnace 2 and simultaneously switches the ejection control valve 20 from the valve closed state to the valve open state. Thereby, the silicon dioxide powder 22 flows from the storage tank 16 to the injection nozzle 9 together with the processing gas, and is injected into the furnace 2 from the outlet 9 a of the injection nozzle 9. At this time, the silicon dioxide powder 22 disperses so as to spread on the processing gas and spread into the furnace 2, and flies like snow in the furnace 2. Moreover, the processing gas is jetted into the furnace 2 along the axial direction from the supply side pipe connection portion 8. Thereby, turbulence is generated inside the furnace 2. Therefore, the silicon dioxide powder 22 ejected to the furnace 2 rides on the turbulent air flow in the furnace 2 so as to spread over the entire internal space of the furnace 2 and is scattered. Therefore, the silicon dioxide powder 22 is distributed almost uniformly throughout the furnace 2.

  Then, as shown in FIG. 2, the silicon powder addition means 15 is directed toward the mixed powder 23 (carbon-iron metal powder 21, sintering preventing material 31) that falls according to the rotation of the furnace 2. The silicon dioxide powder 22 is sprayed from the nozzle 9a. Therefore, as shown in FIG. 5, the carbon-iron-based metal powder 21 is prevented from being sintered by the sintering preventing material 31 before the silicon dioxide powder 22 is jetted, but as shown in FIG. 6, After the silicon dioxide powder 22 is ejected into the furnace 2, the silicon dioxide powder 22 passes through the silicon dioxide powder 22 widely scattered inside the furnace 2, and the surface comes into contact with the silicon dioxide powder 22. As a result, each carbon-iron-based metal powder 21 stirred and mixed in the furnace 2 is prevented from being sintered by the sintering preventing material 31, and the silicon dioxide powder 22 adheres almost uniformly to the surface.

  The carbon-iron-based metal powder 21 is heated to the processing temperature by heating the furnace 2 to the processing temperature with the heater 3. As shown in FIG. 7, the silicon dioxide powder 22 adhering to the surface of the carbon-iron-based metal powder 21 is heated by the heat of the carbon-iron-based metal powder 21 as shown in FIG. Due to this heat, the carbon-iron-based metal powder 21 and the silicon dioxide powder 22 cause an oxidation-reduction reaction, and the silicon element desorbed from the silicon dioxide powder 22 is carbon-iron-based metal powder 21 as shown in FIG. It gradually diffuses and penetrates into the surface. Then, as shown in FIG. 10, when the silicon dioxide powder 22 diffuses and penetrates into the surface of the carbon-iron-based metal powder 21, another silicon dioxide powder 22 adheres to the surface of the carbon-iron-based metal powder 21, and Similarly, the silicon dioxide powder 22 diffuses and penetrates into the surface of the carbon-iron-based metal powder 21. By repeating such a siliconization reaction, the silicon permeation layer 25 formed on the surface of the carbon-iron-based metal powder 21 has a longer distance (thickness) from the surface of the carbon-iron-based metal powder 21, The silicon concentration is increased.

  The oxidation-reduction reaction between the carbon-iron-based metal powder 21 and the silicon dioxide powder 22 is promoted by hydrogen contained in the processing gas. When performing the siliconizing treatment, the carbon element of the carbon-iron-based metal powder 21 is combined with the oxygen of the silicon dioxide powder 22 to generate a monoxide gas (CO gas). 2 is discharged to the outside. Therefore, the internal pressure of the furnace 2 is maintained at a predetermined pressure while the siliconization process is performed.

  By the way, the distribution of the amount of the silicon dioxide powder 22 and the carbon-iron-based metal powder 21 necessary for the siliconization reaction is to make the thickness X1 of the silicon-penetrating layer 25 0.15 times the diameter D of the iron powder 24 or less. In advance. As shown at t1, t2, and t3 in FIG. 3, the silicon powder adding means 15 is defined in advance by periodically switching between the valve closing state and the valve opening state of the ejection control valve 20 during the siliconizing process. The predetermined amount of silicon dioxide powder 22 is intermittently added to the furnace 2 in a plurality of times.

Triangles P <b> 1, P <b> 2, P <b> 3 shown in the dot part of FIG. 3 indicate the amount of silicon dioxide powder 22 remaining in the furnace 2 without diffusing and penetrating into the carbon-iron-based metal powder 21. When all of the previously added silicon dioxide powder 22 diffuses and penetrates into the carbon-iron-based metal powder 21 and does not remain in the furnace 2, the silicon dioxide powder addition means 15 adds the next silicon dioxide powder 22. In this case, as shown by the dotted line portion in FIG. 3, the silicon dioxide powder adding means 15 has an addition amount integrated value P4 obtained by integrating the addition amounts of the silicon dioxide powder 22 each time. The operation (opening / closing timing, valve opening time, valve opening) of the ejection control valve 20 is controlled so as to match the amount of 22 (the amount of SiO ₂ required for the silicidation reaction).

  Therefore, in the siliconization treatment, the addition (injection) of the silicon dioxide powder 22 and the siliconization reaction for diffusing and penetrating the silicon element into the surface of the carbon-iron-based metal powder 21 are repeated alternately. The amount of silicon powder 22 added is adjusted. Therefore, when the amount of the silicon dioxide powder 22 stirred together with the carbon-iron-based metal powder 21 and the sintering preventing material 31 supplies a predetermined amount of the silicon dioxide powder 22 to the furnace 2 at the start of the siliconization treatment. Less than Therefore, the silicon dioxide powder 22 heated in the furnace 2 is not pressure-compressed by being stirred and mixed as the furnace 2 rotates, and secondary particles are not generated. Further, the carbon-iron-based metal powder 21 (iron powder 24) is also prevented from being sintered by the sintering preventing material 31, and is not formed into secondary particles even when continuously stirred and mixed under the processing temperature condition. Furthermore, the silicon dioxide powder 22 does not sinter like a snowman with the sintered carbon-iron metal powder 21 as a core, and does not become secondary particles.

D: Extraction process After the processing time has elapsed, the powder magnetic core manufacturing apparatus 1 causes the processing gas control valve 13, the exhaust valve 5b, and the ejection control valve 20 to be closed, and then the rotation of the furnace 2 and the heater 3 are used. The heating is stopped and the powder in the furnace 2 is cooled. When the internal temperature of the furnace 2 decreases to room temperature, the powder 26 subjected to the siliconization treatment is taken out of the furnace 2. Here, the processing time is the temperature required for the silicification reaction between the carbon-iron-based metal powder 21 and the silicon dioxide powder 22 supplied to the furnace 2 at a predetermined ratio necessary for the silicidation reaction (predetermined processing temperature). The time from the start of the siliconization reaction to the end of the siliconization reaction. In this embodiment, as shown in FIG. 3, the silicon dioxide powder 22 first added (injected) to the furnace 2 after the silicon dioxide powder 22 is added (injected) to the carbon-iron-based metal powder 21. The time until the diffusion and penetration is completed corresponds to the processing time.

E: Washing Step The powder 26 subjected to the siliconization treatment is washed so as to wash away the sintering preventing material 31 and the silicon dioxide powder 22 mixed in the iron powder 24 and then dried. Thereby, only the iron powder 24 remains.

F: Coating treatment The powder 26 produced as described above is put into a solution obtained by dissolving a silicone resin in ethanol and stirred. After stirring for a predetermined time, the ethanol is further stirred while evaporating, and the silicone resin is fixed to the surface of the powder 26 subjected to the siliconization treatment. Thereby, the powder 28 for dust cores in which the silicon permeation layer 25 is covered with the silicone resin coating layer 27 is generated.

  The powder 28 for powder magnetic core manufactured as described above is filled into a molding die and pressed. Thereby, a dust core is manufactured.

FIG. 12 is a diagram showing conditions for the siliconizing treatment in the comparative example and the example.
The powder for powder magnetic cores of the examples is manufactured under the following conditions. A carbon-iron-based metal powder (iron powder) having an average particle size of 150 to 212 μm and a specific gravity of 7.8 and an antisintering material made of silicon dioxide having an average particle size of 7 μm and a specific gravity of 2.2 were mixed with stirring. Things are fed into the furnace 2. With respect to the total weight of the mixed powder, 3% by weight of the sintering preventing material and 97% by weight of the carbon-iron-based metal powder 21 are supplied. Then, the furnace 2 is heated while supplying and exhausting a processing gas in which hydrogen and nitrogen are mixed. When the furnace 2 is heated to the processing temperature (1000 ° C.), the furnace 2 is rotated at a rotational speed of 25 rpm, and the carbon-iron-based metal powder and the sintering preventing material are mixed with stirring. Simultaneously with the rotation of the furnace 2, silicon dioxide powder having an average particle diameter of 50 nm and a specific gravity of 2.2 starts to be ejected into the furnace 2 together with a mixed gas of hydrogen and nitrogen. The silicon immersion reaction is performed under the conditions of 95 to 97% by weight of carbon-iron metal powder and 3 to 5% by weight of silicon dioxide powder. In this case, the silicon dioxide powder divides the amount (3 to 5% by weight) necessary for the silicification reaction into three equal parts. Then, when the furnace 2 was started to rotate, one third of the silicon dioxide powder necessary for the silicification reaction was injected into the furnace 2, and 20 minutes had elapsed since the first silicon dioxide powder was injected. Sometimes one third of the silicon dioxide powder required for the silicidation reaction is injected into the furnace 2, and then the remaining one third when 40 minutes have passed since the first silicon dioxide powder was injected. An amount of silicon dioxide powder is injected into the furnace 2. If processing time (1 hour) passes, the heating and rotation of the furnace 2 will be stopped, and the siliconization process will be complete | finished.

  Here, the sintering preventing material is composed of silicon dioxide as in the case of silicon dioxide powder. However, the anti-sintering material has an average particle size larger than 10 times the average flow rate of the silicon dioxide powder, and is harder than the silicon dioxide powder and difficult to be heated. Therefore, even when the furnace 2 rotates and is stirred and mixed, the sintering preventing material does not sinter with other sintering preventing materials or carbon-iron metal powder.

  On the other hand, the powder for powder magnetic core of the comparative example is manufactured under the following conditions. A carbon-iron-based metal powder (iron powder) having an average particle diameter of 150 to 212 μm and a specific gravity of 7.8, a silicon dioxide powder having an average particle diameter of 50 nm and a specific gravity of 2.2, It puts in the furnace 2 in the ratio which becomes 95 to 97 weight% and silicon dioxide powder becomes 3 to 5 weight%. That is, as shown by the thick line in FIG. 13, all of the silicon dioxide powder necessary for the siliconization reaction is put into the furnace 2 at the start of the siliconization process. Then, as shown by the solid line in FIG. 13, the furnace 2 is heated while supplying and exhausting the processing gas mixed with hydrogen and nitrogen. When the furnace 2 is heated to the processing temperature (1000 ° C.), the furnace 2 is rotated at a rotation speed of 25 rpm, and the carbon-iron-based metal powder and the silicon dioxide powder are mixed with stirring. If processing time (1 hour) passes after rotating the furnace 2, the heating and rotation of the furnace 2 will be stopped, and the siliconization process will be complete | finished.

<About the yield of an Example and a comparative example>
The inventor examined the yield of the example and the comparative example. FIG. 14 shows the experimental results. Here, it is assumed that as the yield is closer to 0%, the generation rate of secondary particles is higher, and as the yield is closer to 100%, the generation rate of secondary particles is lower (in powder form).
The yield of the comparative example was about 5%. That is, almost all of the comparative examples were secondary particles.
On the other hand, the yield of the example was almost 100%. That is, in the example, a fine powdery magnetic core powder could be produced by forming a silicon permeation layer on the surface of each iron powder, and almost no secondary particles were formed.

  From the above experimental results, at the time of the siliconization treatment, a predetermined amount of silicon dioxide powder necessary for the siliconization reaction is divided along the time axis and supplied to the furnace 2 to generate secondary particles. It was proved that a silicon permeation layer can be formed on the iron powder and the productivity of the powder for the dust core is improved.

<Regarding the uniformization of the silicon-permeable layer>
The inventors took out 10 powders at random from the examples, cut them, and observed the cut surfaces with an electron microscope. And the distance of the silicon osmosis | permeation layer formed toward the center part of iron powder from the surface of iron powder was measured according to the powder for powder magnetic cores. The measurement results are shown in FIG.

  As shown in FIG. 15, iron powder and silicon dioxide powder cause oxidation-reduction reaction in all of the randomly extracted powder. Each powder was converged in a range where the Si concentration on the surface of the iron powder was 4.0% or more and 6.0% or less. Each powder had substantially the same rate of decrease in Si concentration from the surface of the iron powder toward the center of the iron powder. Furthermore, each powder has a distance from the surface of the iron powder of the silicon-permeable layer (thickness of the silicon-permeable layer) of about 20 μm, and the distance from the surface of the iron powder of the silicon-permeable layer is made uniform between the powders. It was.

  Therefore, a silicon permeation layer formed on the surface layer of each iron powder by supplying a predetermined amount of silicon dioxide powder necessary for the silicidation reaction along the time axis and supplying it to the furnace 2 during the silicidation treatment. Was able to produce a uniform powder for powder magnetic cores, and proved that the quality of powder for powder magnetic cores was improved.

  In addition, the dust core manufactured using the powder for a dust core having a uniform silicon permeation layer and high quality as described above can increase the dust density and the core density and reduce the iron loss.

(Second Embodiment)
Subsequently, a second embodiment of the present invention will be described.
The method for manufacturing a powder for a powder magnetic core according to the present embodiment is performed using the powder core powder manufacturing apparatus 1, and the powder for a powder magnetic core according to the first embodiment is manufactured except for the method of adding the silicon dioxide powder 22. It is common with the method. Here, it demonstrates centering on a different point from 1st Embodiment, about the structure which is common in 1st Embodiment, the code | symbol same as 1st Embodiment is used and description is abbreviate | omitted suitably.

  In the present embodiment, when the furnace 2 reaches the processing temperature, the silicon powder addition means 15 switches the ejection control valve 20 from the valve closed state to the valve opened state, and continuously injects the silicon dioxide powder 22 into the furnace 2. . That is, the ejection control valve 20 maintains the valve open state during the processing time of the siliconization reaction. The silicon powder addition means 15 is configured so that the integrated amount of silicon dioxide powder continuously ejected into the furnace 2 within the processing time matches the amount of silicon dioxide powder 22 required for the siliconization reaction. The operation (valve opening time, valve opening) of the ejection control valve 20 is controlled.

  In the powder magnetic core powder 1 and the powder magnetic core manufacturing method of this embodiment, the ejection control valve 20 is kept open until the processing time elapses after the internal temperature of the furnace 2 reaches the processing temperature. Thus, a predetermined amount of silicon dioxide powder 22 required for the siliconization reaction is added to the furnace 2 little by little. In this case, the injection amount of the silicon dioxide powder 22 is adjusted so that the injected silicon dioxide powder 22 adheres to the surface of the carbon-iron-based metal powder 21 and undergoes a silicification reaction. That is, the injection amount is adjusted so that the silicon dioxide powder 22 is not surplus in the furnace 2 and is stirred and mixed together with the carbon-iron-based metal powder 21. Thereby, the addition of the silicon dioxide powder 22 and the silicon immersion reaction for diffusing and penetrating silicon element into the surface of the carbon-iron-based metal powder 21 proceed in parallel. Therefore, the amount of the silicon dioxide powder 22 stirred together with the carbon-iron-based metal powder 21 and the sintering preventing material 31 causes the silicon dioxide powder 22 required for the siliconization reaction at the time of the siliconization treatment to be processed in the furnace. 2 compared with the case where all are supplied. Therefore, the silicon dioxide powder 22 heated in the furnace 2 is not pressure-compressed by being stirred and mixed as the furnace 2 rotates, and secondary particles are not generated. Further, the carbon-iron-based metal powder 21 (iron powder 24) is also prevented from being sintered by the sintering preventing material 31, and is not formed into secondary particles even when continuously stirred and mixed under the processing temperature condition.

  As described above, the powder magnetic core powder manufacturing apparatus and the powder magnetic core powder manufacturing method of the present embodiment are configured so that a predetermined amount of silicon dioxide powder is applied along the time axis while the furnace 2 is rotated while being heated. Then, the silicon dioxide powder 22 is attached to the surface of the carbon-iron-based metal powder 21 and the silicidation reaction is advanced by adding it separately to the furnace 2. Since the silicon dioxide powder 22 is continuously added to the furnace 2 little by little along the time axis, there is little silicon dioxide powder 22 stirred and mixed together with the carbon-iron-based metal powder 21 during the silicidation reaction. Therefore, when the carbon-iron-based metal powder 21 is mixed with stirring, the silicon dioxide powder 22 is not sintered. Therefore, according to the method for manufacturing a powder for a powder magnetic core and the powder manufacturing apparatus 1 for a powder magnetic core, secondary particles are prevented from being generated during the siliconization treatment, and the powder 28 for powder magnetic core (the siliconization treatment is performed). The quality and productivity of the applied powder 26) can be improved.

The present invention is not limited to the above embodiment, and various applications are possible.
(1) For example, in the above-described embodiment, a sintering inhibitor made of silicon dioxide is used, but a sintering inhibitor made of ceramics such as zirconia or alumina may be used.
(2) For example, in the above embodiment, the inside of the rotary furnace 2 is an atmosphere filled with a mixed gas of oxygen and nitrogen, but an atmosphere in which the rotary furnace 2 is in a vacuum state may be used. Further, the siliconizing treatment may be performed in a reduced pressure atmosphere, or in a low gas partial pressure, specifically in a low carbon monoxide (CO) atmosphere or in a low nitrogen (N ₂ ) atmosphere. The processing gas may be another gas such as carbon gas as long as it promotes the oxidation-reduction reaction between the soft magnetic metal powder and the silicon immersion powder.
(3) For example, in the above embodiment, the stirring plate 6 fixed to the inner wall of the rotary furnace 2 is provided in a straight line parallel to the axis of the rotary furnace 2, but the stirring is fixed to the inner wall of the rotary furnace 2. The plate may be provided in a spiral shape. In this case, since the mixed powder supplied to the rotary furnace 2 is placed on a spiral stirring plate and gradually falls as the rotary furnace 2 rotates, the silicon dioxide powder added by the siliconization powder adding means 15 is carbon- It can be easily attached to the surface of the iron-based metal powder 21.
(4) For example, in the said embodiment, although the carbon-iron type metal powder 21 was raised as an example of a soft magnetic metal powder, Fe-Si alloy, Fe-Al alloy, Fe-Si-Al alloy, titanium, aluminum, etc. May be soft magnetic metal powder.
(5) For example, in the said embodiment, the heater 2 was mentioned as an example of a heating means. On the other hand, it is good also as a heating means which arrange | positions a coil around the furnace provided with the insulating material, and heats a soft magnetic metal powder by induction heating.

DESCRIPTION OF SYMBOLS 1 Powder manufacturing apparatus for dust core 2 Furnace 3 Heater (an example of a heating means)
15 Powder Addition Means for Silica 21 Carbon-Iron Metal Powder (Example of Soft Magnetic Metal Material)
22 Silicon dioxide (an example of powder for silicon immersion)
25 Silicon permeation layer 28 Powder for powder magnetic core

Claims (7)

A powder for siliconization containing a predetermined amount of soft magnetic metal powder and a predetermined amount of silicon dioxide is heated in a furnace for a predetermined processing time, and a silicon-penetrating layer is formed on the surface of the soft magnetic metal powder, thereby compacting the powder. In the method for producing a powder for a powder magnetic core for producing a powder for a magnetic core,
A powder magnetic core comprising a step of adding a powder for siliconization, wherein the predetermined amount of powder for siliconization is added along the time axis while the furnace is rotated while being heated. Powder manufacturing method. In the manufacturing method of the powder for powder magnetic cores described in claim 1,
A method for producing a powder for a powder magnetic core, comprising: a sintering preventing material supplying step of supplying a sintering preventing material for preventing sintering of the soft magnetic metal powder to the furnace. In the manufacturing method of the powder for powder magnetic cores described in Claim 1 or Claim 2,
In the silicon powder addition step, the predetermined amount of silicon powder is added by spraying and dispersing the powder into the furnace. In the manufacturing method of the powder for powder magnetic cores as described in any one of Claims 1 thru | or 3,
In the said siliconization powder addition manual process, the said predetermined amount of siliconization powder is intermittently added to the said furnace in multiple times, The manufacturing method of the powder for powder magnetic cores characterized by the above-mentioned. In the manufacturing method of the powder for powder magnetic cores as described in any one of Claims 1 thru | or 3,
In the said siliconization powder addition manual process, the said predetermined amount of siliconization powder is continuously added to the said furnace, The manufacturing method of the powder for powder magnetic cores characterized by the above-mentioned.   A powder magnetic core powder produced by the method for producing a powder magnetic core powder according to any one of claims 1 to 5 is filled in a molding die and pressed. Dust magnetic core. A furnace supplied with a predetermined amount of siliconizing powder containing a predetermined soft magnetic metal powder and silicon dioxide powder, a heating means for heating the furnace, and the soft magnetic metal by heat that the heating means heats the furnace A powder manufacturing apparatus for a powder magnetic core, comprising: a processing gas supply means for supplying a processing gas for promoting diffusion and permeation of the silicon dioxide powder to the surface of the powder; and an exhaust means for exhausting the gas from the furnace. In
Rotating means for rotating the furnace;
An apparatus for producing a powder for a powder magnetic core, comprising means for adding a silicon powder for dividing the predetermined amount of silicon powder along the time axis and adding the powder to the furnace.

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