JP2007254768A - Soft magnetic powder material, its production method, soft magnetic compact and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic powder material provided with a coated layer having high barrier properties to the diffusion of elements to iron powder grains, to provide its production method, to provide a soft magnetic compact using the soft magnetic powder material, and to provide its production method. <P>SOLUTION: The soft magnetic powder material is provided with: iron powder grains 1 essentially consisting of iron; and a coated layer 2 essentially consisting of silicon oxide, which is applied to the surface of each iron powder grain 1 by contacting an inorganic silicon-containing compound-added aqueous solution with each iron powder grain, and further, the external layer of the coated layer 2 is coated with a ferrite layer 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a soft magnetic powder material and a manufacturing method thereof, a soft magnetic molded body and a manufacturing method thereof.

  With recent advances in industrial equipment and the like, soft magnetic materials are required to have higher magnetic permeability than before. In addition to high magnetic permeability, it is required to have a high specific resistance in order to reduce iron loss and the like. In response to these demands, various studies have been advanced so far, and various techniques relating to soft magnetic molded bodies have been proposed.

  In Patent Document 1, the surface of powder particles is selectively oxidized by heat-treating Fe—Al-based iron-based powder in the atmosphere, and aluminum oxide and iron oxide having high specific resistance are formed on the surface of the powder particles. A technique for producing a high-density magnetic core by forming soft magnetic particles coated with a film and molding a powder aggregate of the soft magnetic particles under high temperature and high pressure is disclosed.

  In Patent Document 2, the soft ferrite layer is mechanically agitated on the surface of the soft magnetic metal particles by carrying out mechanofusion by mechanically stirring the soft magnetic metal particles and soft ferrite in the drum. And a technique for producing a magnetic core by plasma activated sintering of a powder aggregate of soft magnetic metal particles.

  In Patent Document 3, the surface of soft magnetic metal powder particles is coated with a glassy oxide having a high specific resistance, and the powder aggregate of the soft magnetic metal powder particles is sintered at high temperature and high pressure. A technique for producing a soft magnetic molded body is disclosed.

Further, in Patent Document 4, 0.05 to 1 composite powder particles in which the surface of Fe-Si based soft magnetic powder particles is coated with a ferrite layer having a spinel structure and SiO ₂ powder particles having an average particle diameter of 100 nanometers. A manufacturing method is disclosed in which a mixed powder is formed by adding 0.0% by mass, a green compact is then formed from the mixed powder, and then the green compact is sintered.

  Further, in Patent Document 5, composite powder particles in which a coating layer is formed on the surface of soft magnetic powder particles are formed, and then mixed powder in which composite powder particles and powdered ferrite material are mixed and dispersed is formed, Thereafter, a method for producing a composite sintered material is disclosed in which a green compact is formed from the mixed powder and the green compact is sintered.

In Patent Document 6, soft magnetic particles in which a ferrite film is formed on iron-based powder containing chromium and molybdenum are formed, and then a compact is formed by pressing an aggregate of the soft magnetic particles, A technique for forming a composite magnetic material by sintering a green compact is disclosed.
JP-A-5-326289 Japanese Patent Laid-Open No. 5-47541 JP-A-8-167519 JP 2003-306704 A JP 2005-243794 A JP 2005-150257 A

  According to each of the prior arts described above, since the specific resistance of the soft magnetic molded body can be increased, the eddy current generated in the soft magnetic molded body can be suppressed even when the soft magnetic molded body is used, and as a result Loss due to current can be suppressed.

  However, when a soft magnetic molded body is formed by sintering, the diffusion of the iron component constituting the iron powder particles cannot be ignored. When the amount of diffusion is large, a substance with low resistance is likely to be generated at the interface between the iron powder particles. In this case, there is a problem that it is difficult to obtain the intended magnetic performance of the soft magnetic molded body.

In particular, according to the technique according to Patent Document 4, although SiO ₂ (silica) powder particles are used outside the iron powder particles, the iron powder particles → the ferrite layer → the silica powder particles are arranged in this order, Interdiffusion is likely to occur between the iron powder particles and the ferrite layer. For this reason, according to the technique concerning patent document 4, there exists a possibility that a mutual diffusion may generate | occur | produce easily between an iron powder particle and a ferrite layer, and a substance with low electrical resistance may produce | generate. In this case, an eddy current loop occurs between adjacent iron powders, which may increase eddy current loss, and it may be difficult to obtain the intended magnetic performance of the soft magnetic molded body.

  The present invention has been made in view of the above circumstances, and is a soft magnetic powder that is advantageous for obtaining a desired magnetic performance by forming a coating layer having a high barrier property against element diffusion on the surface of iron powder particles. It is an object to provide a material and a manufacturing method thereof, a soft magnetic molded body, and a manufacturing method thereof.

  The present inventor has been intensively developing technologies relating to soft magnetic particles and soft magnetic compacts. If the surface of the iron powder particles is coated with a coating layer mainly composed of silicon oxide, the coating has a high barrier property against element diffusion even when the soft magnetic particles are heated to a high temperature region and sintered. A layer was obtained, and as a result, it was found that it was possible to suppress the generation of a nonmagnetic substance having a low electrical resistance at the interface between the iron powder particles, which was confirmed by a test to complete the present invention.

  (1) That is, the soft magnetic powder material according to aspect 1 includes iron powder particles mainly composed of iron and a coating layer mainly coated with silicon oxide and coated on the surface of the iron powder particles. Features. The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside. Thereby, it can suppress that the nonmagnetic substance with low electrical resistance is produced | generated in the interface of iron powder particle | grains.

  (2) The soft magnetic powder material according to aspect 2 is mainly composed of iron powder particles mainly composed of iron, a coating layer coated on the surface of the iron powder particles and mainly composed of a silicon oxide layer, and silicon oxide. It has a coating layer as a component and a ferrite layer coated on the coating layer, and a coating layer mainly composed of silicon oxide is interposed between the iron powder particles and the ferrite layer. And

  The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside. Moreover, it is suppressed that the component which comprises a ferrite layer diffuses into the inside of an iron powder particle. Thereby, it can suppress that the nonmagnetic substance with low electrical resistance is produced | generated in the interface of iron powder particle | grains.

  (3) The method for producing a soft magnetic powder material according to aspect 3 includes a first step of preparing iron powder particles mainly composed of iron, and a coating layer mainly composed of silicon oxide on the surface of the iron powder particles. The second step of covering is performed in order.

  The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside. Thereby, it can suppress that the nonmagnetic substance with a low electrical resistance and a low magnetic permeability is produced | generated in the interface of iron powder particle | grains.

  (4) The method for producing a soft magnetic powder material according to aspect 4 includes a first step of preparing iron powder particles mainly composed of iron, and a coating layer mainly composed of silicon oxide on the surface of the iron powder particles. A second step of covering, and a third step of covering the iron powder particles coated with silicon oxide with a ferrite layer and interposing a coating layer mainly composed of silicon oxide between the iron powder particles and the ferrite layer; Are performed in order.

  The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside (ferrite layer). Moreover, it is suppressed that the component which comprises a ferrite layer diffuses into the inside of an iron powder particle. Thereby, it can suppress that the nonmagnetic substance with low electrical resistance is produced | generated in the interface of iron powder particle | grains.

  (5) The soft magnetic molded body according to aspect 5 is characterized in that particles of a powder aggregate mainly composed of the soft magnetic powder material according to the above aspect are bonded to each other.

  The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside. Moreover, when the ferrite layer is coat | covered, it is suppressed that the component which comprises the ferrite layer diffuses inside the iron powder particle. Thereby, it can suppress that the nonmagnetic substance with low electrical resistance is produced | generated in the interface of iron powder particle | grains.

  (6) In the method for producing a soft magnetic molded body according to aspect 6, the operation of pressing and heating the powder aggregate mainly composed of the soft magnetic powder material according to the above aspect is performed simultaneously or for a time. It is characterized in that a soft magnetic molded body is formed by deviating. Thereby, a soft magnetic compact is obtained. The coating layer has a high barrier property against element diffusion. For this reason, it is suppressed that the iron component which comprises an iron powder particle diffuses outside. Moreover, when the ferrite layer is coat | covered, it is suppressed that the component which comprises the ferrite layer diffuses inside the iron powder particle. Thereby, it can suppress that the nonmagnetic substance with low electrical resistance is produced | generated in the interface of iron powder particle | grains.

  According to the present invention, by forming a coating layer having a high barrier property against element diffusion on the surface of iron powder particles, a soft magnetic powder material advantageous for obtaining a desired magnetic performance, a method for producing the same, and soft magnetic molding The body can be provided.

  The iron powder particles according to the present invention include pure iron (Fe), iron-aluminum system (Fe-Al system), iron-silicon system (Fe-Si system), iron-nickel system (Fe-Ni system), iron -At least one of silicon-aluminum (Fe-Si-Al system), iron-chromium system (Fe-Cr system), and iron-cobalt system (Fe-Co system) can be used. good. When the iron powder particles are 100%, by mass ratio, C can be 0.1% or less, especially 0.01% or less, and O is 0.5% or less, especially 0.1% or less. It can be. The iron powder particles may be manufactured by a water atomizing method, may be manufactured by a gas atomizing method, or may be manufactured by a mechanical crushing method in some cases.

  When the particle size of the iron powder particles is excessively small, it is difficult to obtain satisfactory magnetic time. When the particle size of the iron powder particles is excessively large, the compression moldability is lowered when the soft magnetic molded body is compression molded. Therefore, the particle size of the iron powder particles may be 10 μm to 2000 μm, 10 μm to 1000 μm, preferably 50 to 250 μm, and more preferably 100 μm to 200 μm.

  The ferrite layer is basically an oxide layer mainly composed of iron oxide and having high electrical insulation, and has high specific resistance and high magnetic permeability. Therefore, if the surface of the iron powder particles containing iron as a main component is coated with a ferrite layer, it is advantageous to exhibit high specific resistance and high magnetic permeability. Therefore, when used in an application in which an alternating magnetic field such as a high-frequency alternating magnetic field acts, the eddy current is reduced and the loss caused by the eddy current is reduced.

Generally, a spinel structure can be adopted as the ferrite layer. Since the spinel structure has a relatively small magnetocrystalline anisotropy, the permeability and saturation magnetic flux density are high. In this case, a form having a composition formula of (Fe, M) ₃ O ₄ can be adopted as the ferrite layer. M is at least one of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), zinc (Zn), copper (Cu), chromium (Cr), aluminum (Al), and titanium (Ti) It can be. When M is Ni or Zn, it is also called NiZn ferrite. Although the thickness of the ferrite layer depends on the composition of the ferrite layer, the particle diameter of the iron powder particles, etc., it can be 0.01 μm to 10 μm, particularly 0.01 μm to 2 μm, 0.2 μm to 1 μm. It is not limited to.

  When the thickness of the ferrite layer is excessive, it takes a long time to form the ferrite layer, which is not preferable in terms of industrial production. If the thickness of the ferrite layer is too small, it becomes difficult to obtain the desired specific resistance of the soft magnetic particles and the soft magnetic compact, and there is a possibility that the loss caused by the eddy current increases when used in an alternating magnetic field.

The coating layer contains silicon oxide (generally SiO ₂ ) as a main component. Silicon oxide has high electrical insulation. The thickness of the coating layer is influenced by the composition and size of the iron powder particles, but is exemplified by 1 to 500 nanometers, particularly 5 to 100 nanometers.

The soft magnetic molded body according to the present invention can be formed by performing a pressing operation and a sintering operation simultaneously or at different times on a powder aggregate mainly composed of a soft magnetic powder material. it can. In this case, the powder aggregates of soft magnetic particles are joined together. In producing a soft magnetic molded body, a step of preparing a powder aggregate mainly composed of the above-mentioned soft magnetic particles, and soft magnetic molding by pressing the powder aggregates of the soft magnetic particles and bonding them together And a binding step to obtain a body. Examples of the pressure molding include a mold pressing system and a hydrostatic pressure system (CIP). The applied pressure varies depending on the type of iron powder particles, the pressure molding pressure, etc., but is 2.0 to 10 tonf / cm ² (≈196 to 980 MPa), especially 4.5 to 7 tonf / cm ² (≈441 to 441). 686 MPa) can be exemplified, but is not limited thereto. Although the pressurization time varies depending on the type of iron powder particles, the pressure molding temperature, etc., it can be exemplified by 5 to 120 seconds, particularly 10 to 60 seconds, but is not limited thereto. Examples of the pressure forming atmosphere include an air atmosphere and a non-oxidizing atmosphere (such as an argon gas atmosphere and a vacuum atmosphere).

  The method for producing a soft magnetic powder material includes a first step of preparing iron powder particles mainly composed of iron, and a second step of covering a surface of the iron powder particles with a coating layer mainly composed of silicon oxide, A ferrite layer is coated on the coating layer of iron powder particles, and a third step is sequentially performed in which a coating layer mainly composed of silicon oxide is interposed between the iron powder particles and ferrite.

  The second step is exemplified by an embodiment in which an inorganic silicon-containing compound is used and a contact operation in which the aqueous solution to which the silicon-containing compound is added and the iron powder particles are brought into contact with each other is performed. As the contact operation, iron powder particles may be immersed in an aqueous solution to which a silicon-containing compound is added, or an aqueous solution to which a silicon-containing compound is added may be sprayed onto the iron powder particles. In order to increase the reactivity, it is preferable to heat the aqueous solution.

Water glass can be used as the silicon-containing compound. Water glass is an alkali silicate and exhibits alkalinity. The alkali is generally sodium, and the water glass includes sodium silicate. As a general formula, Na ₂ O · nSiO ₂ may be mentioned. For example, n = 2 to 4. The alkali constituting the alkali silicate may be potassium.

  Here, when the water glass is too thin in the aqueous solution, the time for the silicon oxide to adhere to the surface of the iron powder particles becomes long, and the productivity is lowered. If the water glass is too concentrated in the aqueous solution, silicon oxide will not adhere uniformly to the iron powder particles. For this reason, as a density | concentration of the water glass in aqueous solution, about 1 to 10% by mass ratio, especially about 1 to 5% are mentioned.

  The contact operation described above is preferably carried out while adding an alkali adjusting agent (basic substance) to the aqueous solution and setting the pH value of the aqueous solution to the alkaline region. An alkali metal hydroxide can be used as the alkali adjuster. Examples thereof include sodium hydroxide and potassium hydroxide. The reason for setting the pH value of the aqueous solution in the alkaline region is to suppress the generation of rust and the formation of an oxide film on the surface of the iron powder particles. If rust or an oxide film is generated on the surface of the iron powder particles, it is presumed that the silicon oxide hardly adheres to the surface of the iron powder particles. The PH value of the aqueous solution may be in the alkaline range, and the PH value may be 7.5 to 14 or 8 to 13. In this case, even if the alkalinity is too strong or too weak, the silicon oxide hardly adheres to the surface of the iron powder particles.

  Examples of the soft magnetic molded body include a stator core of a motor, a rotor core of a motor, and a soft magnetic core of an electromagnetic actuator. The motor may be a known motor, and includes a rotary motor and a linear motor. The electromagnetic actuator means an actuator that is operated by a magnetic force or an electromagnetic force by energizing a coil, and includes a solenoid valve used in a fluid circuit such as a plunger-type solenoid device, a hydraulic circuit or a pneumatic circuit. .

  Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 shows a conceptual diagram of iron powder particles 1. First, a powder aggregate of iron powder particles 1 having the following soft magnetism is prepared. The composition of the iron powder particles 1 is close to that of pure iron, and in terms of mass ratio, Fe-0.25% C-0.25% O-0.03% Si-0.1% Mn-0.001% P. The manufacturing method is a gas atomizing method, and the average particle diameter of the particles is about 100 μm.

And the coating layer 2 is coat | covered by the wet process on the surface of the iron powder particle | grains 1. FIG. In this case, water glass (alkali silicate, Na ₂ O · nSiO ₂ , n = 2 to 4), which is an inorganic silicon-containing compound, is used. And water glass is added to 70 degreeC water. The addition ratio of water glass is about 1% by mass ratio. Then, the pH value of the aqueous solution is adjusted to around 12 with sodium hydroxide as a PH adjuster. This is the adjustment liquid.

Next, the aggregate of the iron powder particles 1 is immersed in the adjustment liquid, and the iron powder particles 1 are held in the adjustment liquid at a predetermined time (about 1 hour) and at a predetermined temperature (about 70 ° C.). Thereafter, the aggregate of the iron powder particles 1 is taken out from the adjustment liquid, and the iron powder particles 1 are dried. Thereby, the coating layer 2 is formed on the surface of the iron powder particles 1. FIG. 2 schematically shows a conceptual cross section of the soft magnetic powder particles thus produced. The covering layer 2 is basically formed with silicon oxide (SiO ₂ ) as a main component. The thickness of the coating layer 2 can be about 1 to 500 nanometers.

As described above, according to this embodiment, the coating layer 2 containing silicon oxide (SiO ₂ ) as a main component is formed on the surface of the iron powder particles 1 by immersing the aggregate of the iron powder particles 1 in the adjustment liquid. To form. With such a method, a large amount of soft magnetic powder particles coated with the coating layer 2 can be produced while reducing costs.

  Hereinafter, FIG. 3 and FIG. 4 are demonstrated about Example 2 of this invention. According to this example, the aggregate of iron powder particles 1 coated with the coating layer 2 manufactured in Example 1 is used. And the ferrite layer 4 is coat | covered on the coating layer 2 of this iron-powder particle 1 (refer FIG. 4). Thereby, the coating layer 2 containing silicon oxide as a main component is interposed between the iron powder particles 1 and the ferrite layer 4 (see FIG. 4).

  When the ferrite layer 4 is coated, the mechanofusion apparatus shown in FIG. 3 is used. In this case, as shown in FIG. 3, the mechano-fusion device is arranged in a cylindrical case 100 (inner diameter 150 mm), a scraper 102 rotatably arranged in the case 100, and rotatably in the case 100. An inner piece 104.

  And the aggregate | assembly of the iron powder particle | grains 1 which coat | covered the coating layer 2, and the aggregate | assembly of a ferrite powder particle (average particle diameter: 5-300 nanometer) 3 are inserted in the cylindrical case 100 of a mechanofusion apparatus. . In this case, the blending ratio was, as a mass ratio, iron powder particles 1 covering the coating layer 2: ferrite powder particles 3 = 99.4: 0.6.

The ferrite powder particles 3 are Ni—Zn—Cu ferrite. That is, the ferrite powder particles 3 are mainly composed of iron oxide (Fe ₂ O ₃ ) and include nickel oxide, zinc oxide, and copper oxide. Specifically, the composition of ferrite is about 45% of nickel oxide, about 2% of zinc oxide, about 3% of copper oxide, and the balance of iron oxide and inevitable impurities by mass ratio. Since the ferrite powder particles 3 contain a copper component, the sintering temperature between the ferrite powder particles 3 can be lowered as compared with the case where no ferrite component is contained. The sintering temperature between the ferrite powder particles 3 can be lowered from about 1100 ° C. to 750 to 850 ° C.

  Then, the mechano-fusion device is operated, and the scraper 102 and the inner piece 104 are rotated at a rotation speed of 800 rpm for 40 minutes while supplying an inert gas (argon gas) into the case 100 at a flow rate of 5 liters / minute. As a result, the scraping action by the scraper 102 and the compression action by the inner piece 104 act on the iron powder particles 1 and the ferrite powder particles 3 arranged in the case 100. As a result, the ferrite powder particles 3 are deposited on the iron powder particles 1 coated with the coating layer 2 containing silicon oxide as a main component, and the ferrite layer 4 is formed on the coating layer 2. As a result, the coating layer 2 containing silicon oxide as a main component is interposed between the iron powder particles 1 and the ferrite layer. FIG. 4 schematically shows a conceptual cross section of the soft magnetic powder particles thus produced.

  Embodiment 3 of the present invention will be described below. According to this example, the soft magnetic powder particles produced in Example 2 are used. The soft magnetic powder particles have an iron powder particle 1 coated with a coating layer 2 containing silicon oxide as a main component, and a ferrite layer 4 coated with the coating layer 2 of the iron powder particle 1. Between the iron powder particles 1 and the ferrite layer 4, there is a coating layer 2 mainly composed of silicon oxide (see FIG. 4).

Then, as shown in FIG. 5, a mold 200 having a first split mold 201 and a second split mold 202 is used to load the above-described aggregate of soft magnetic powder particles into the cavity 203 of the mold 200. Thereafter, the aggregate of soft magnetic powder particles in the cavity 203 of the mold 200 is pressure-molded to form the green compact 6. Thereafter, the green compact 6 is sintered in a sintering atmosphere in a nitrogen atmosphere at a sintering temperature of 750 ° C. for 1 hour. Thereby, the soft magnetic powder particles constituting the green compact 6 are bonded to each other. Thereby, the soft magnetic molded body 7 is formed. As the conditions for the pressure molding, the atmosphere is an air atmosphere, the temperature is about 25 ° C., and the surface pressure is about 8 tonf / cm ² (≈800 MPa).

According to the soft magnetic molded body 7 manufactured as described above, the soft magnetic powder particles are bonded to each other. Between the iron powder particles 1 constituting the soft magnetic powder particles and the ferrite layer 4, the coating layer 2 is interposed in the form of a film. The covering layer 2 contains silicon oxide (SiO ₂ ) having high electrical insulation as a main component. For this reason, when the soft magnetic molded body 7 is used in a site where an alternating magnetic field acts, the coating layer 2 mainly composed of silicon oxide (SiO ₂ ) having high electrical insulation prevents the eddy current loop. Thus, loss due to eddy current is suppressed.

  In order to improve the sinterability of the soft magnetic powder particles, the sintering temperature is preferably set to a certain level or more. However, when sintered at a high temperature, element diffusion proceeds between the iron powder particles 1 and the ferrite layer 4, and a nonmagnetic substance (for example, FeO) having a low electric resistance and a low magnetic permeability is converted into the iron powder particles 1 and the ferrite layer 4. May be generated between

In this respect, according to the present embodiment, the coating layer 2 having a high diffusion barrier property mainly composed of silicon oxide (SiO ₂ ) is provided between the iron powder particles 1 constituting the soft magnetic powder particles and the ferrite layer 4. Is interposed in the form of a film. For this reason, when the green compact 6 is sintered in the sintering temperature region, the iron component of the iron powder particles 1 is suppressed from diffusing to the ferrite layer 4 side. Similarly, the diffusion of the components of the ferrite layer 4 to the iron powder particle 1 side is suppressed. Thus, during the sintering, even when the sintering temperature is high, the diffusion of elements is suppressed by the coating layer 2. For this reason, generation | occurrence | production of the nonmagnetic substance (for example, FeO) with a low electrical resistance and a low magnetic permeability between the iron powder particle 1 and the ferrite layer 4 is suppressed. Therefore, good magnetic properties of the soft magnetic molded body 7 can be obtained.

By the way, since the ferrite powder particles forming the ferrite layer are oxides, the sintering temperature region of the ferrite powder particles needs to be higher than 1000 to 1200 ° C. as compared with the case where only iron powder is sintered. . In this regard, according to the present embodiment, the ferrite powder particles 3 forming the ferrite layer 4 contain iron oxide (Fe ₂ O ₃ ) as a main component and include nickel oxide, zinc oxide, and copper oxide. Thus, since the ferrite powder particle 3 contains a copper component, the sintering temperature between the ferrite powder particles 3 can be lowered as compared with the case where the ferrite powder particle 3 does not contain a copper component. For this reason, the sintering temperature of the iron powder particles 1 can be brought close to the sintering start temperature of the ferrite powder particles 3. For this reason, sinterability can be improved.

Hereinafter, test examples of the present invention will be specifically described. In this test example, for convenience, a test piece 10 made of an iron plate (thickness: 2 millimeters, length: 1 centimeter, width: 1 centimeter) was regarded as an iron-based particle and used as a test piece. The composition of the test piece 10 substantially corresponds to the composition of the iron powder particles 1 and contains 0.25% carbon, 0.03% silicon, and 0.16% manganese. According to the present embodiment, the silicon oxide (SiO ₂ ) coating layer 20 is formed on the surface of the test piece 10 by wet processing. A procedure for forming the coating layer 20 will be described.

  First, water glass was added to 70 ° C. water. The addition ratio of water glass was about 1% by mass ratio. In this case, the pH value was adjusted to around 12 with sodium hydroxide as a pH adjusting agent, and the adjusting liquid 12 was formed.

Next, the test piece 10 was immersed in the adjustment liquid 12 for a predetermined time (1 hour), and the test piece 10 was held in the adjustment liquid 12 at a predetermined temperature (70 ° C.). Then, the test piece 10 was taken out from the adjustment liquid 12, and the test piece 10 was dried. Thereby, a thin coating layer 20 is formed on the surface of the test piece 10. The covering layer 20 is basically formed of silicon oxide (SiO ₂ ). The thickness of the coating layer 20 was about 1 micrometer when measured with a film thickness meter (model K-402B, manufactured by ANRITSU ELECTRIC Co., Ltd.).

  About the test piece 10 which coat | covered the coating layer 20, it heat-processed by heating at 450 degreeC for 1 hour in nitrogen gas atmosphere. Further, another test piece 10 coated with the coating layer 20 was heated at 600 ° C. for 1 hour in a nitrogen gas atmosphere to perform heat treatment, thereby promoting bonding at the interface of the test piece 10. Furthermore, another test piece 10 coated with the coating layer 20 was heated at 800 ° C. for 1 hour in a nitrogen gas atmosphere to perform heat treatment.

  In performing the heat treatment in this way, as shown in FIG. 8, two test pieces 10 were overlapped to obtain a sample. In the sample, the coating layers 20 coated on the test piece 10 are overlapped and in contact with each other.

The comparative example was tested. According to the comparative example, one ferrite sheet 40 (Ni-Zn-Cu ferrite sheet, thickness 1 micrometer) was placed on the surface of the test piece 10S made of an iron plate. The ferrite sheet 40 corresponds to the ferrite layer 4. The ferrite sheet 40 contains iron oxide (Fe ₂ O ₃ ) as a main component and includes nickel oxide, zinc oxide, and copper oxide. Specifically, the composition of the ferrite sheet 40 was 45% of nickel oxide, 2% of zinc oxide, 3% of copper oxide, and the balance of iron oxide and inevitable impurities by mass ratio. And two test pieces 10S were laminated | stacked in the contact state so that the ferrite sheet 40 might overlap. This was used as a sample for comparison.

  And the electrical resistance of the thickness direction was measured about the sample which concerns on the example, and the sample which concerns on a comparative example by the 2 terminal method. The test results are shown in FIG. In FIG. 10, a characteristic line W1 indicates the test result of the sample according to the example. The characteristic line W2 shows the test result of the sample according to the comparative example.

  As shown by the characteristic line W2 in FIG. 10, according to the sample according to the comparative example, when the heat treatment temperature was 450 ° C., the electrical resistance of the sample was maintained high, but when the heat treatment temperature was 600 ° C. The electrical resistance of the sample dropped rapidly. From this, according to the sample according to the comparative example, when heated to the sintering temperature region, the diffusion is promoted, and the ferrite sheet 40 formed on the surface of the test piece 10 has a low electrical resistance (FeO ) Is generated, it is assumed that the electrical resistance in the thickness direction of the sample was reduced. This means that, when applied to a soft magnetic powder material, the electrical conductivity between the iron powder particles 1 is increased, the eddy current loop easily flows, and the eddy current loss increases.

  On the other hand, as shown by the characteristic line W1, according to the sample according to the example, the electrical resistance of the sample was kept high even when the heat treatment temperatures were 450 ° C., 600 ° C., and 800 ° C. . From this, according to the sample which concerns on an Example, since the diffusion barrier property of the coating layer 2 currently formed in the surface of the test piece 10 is high, spreading | diffusion of the iron component of the iron powder particle 1 is suppressed, and it is in a high temperature area | region. Even when heated, it is presumed that the electrical insulation of the coating layer 2 formed on the surface of the test piece 10 is well maintained.

XRD analysis was performed using an X-ray diffractometer. In this case, a sample in which two test pieces 10 on which the coating layer 20 was formed was overlapped so that the coating layers 20 overlap each other was subjected to a heat treatment in which the sample was heated at 800 ° C. for 1 hour in a nitrogen atmosphere. . The XRD analysis results are shown in FIG. 11 (the horizontal axis is 2θ, and the vertical axis is intensity). As shown in FIG. 11, the SiO ₂ peak (identified by the ASTM card) was recognized even under the condition of heating at a high temperature of 800 ° C. for 1 hour. That is, even when sintered in a high temperature region, silicon oxide remains well in the coating layer 2, which is advantageous for maintaining diffusion barrier properties between the iron powder particles 1 and maintaining electrical insulation. It becomes.

  The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention. According to the above-described embodiment, when the water glass is added to water, the addition ratio of the water glass is about 1% by mass ratio, but is not limited thereto, and may be about 0.1 to 8%. . According to the above embodiment, the ferrite powder particles may be Ni—Zn ferrite or Ni—Cu ferrite.

It is a block diagram which shows typically the concept of the iron powder particle used in Example 1. FIG. It is a block diagram which shows typically the concept of the state which coat | covered the coating layer on the iron powder particle of Example 1. FIG. It is a block diagram which shows typically the method which concerns on Example 2 and coat | covers the ferrite layer on the surface of the iron powder particle | grains which coat | covered the coating layer. It is a block diagram which shows typically the concept of the soft-magnetic particle which concerns on Example 2 and coat | covered the ferrite layer on the surface of the iron powder particle | grains which coat | covered the coating layer. FIG. 10 is a configuration diagram schematically showing a process of forming a green compact according to Example 3. FIG. 6 is a configuration diagram schematically showing a soft magnetic molded body formed by sintering a green compact according to Example 3. It is a block diagram which shows typically the process which concerns on Example 4 and coat | covers a coating layer on a test piece. It is a block diagram which shows typically the state which concerns on Example 4 and measures the electrical resistance of the thickness direction of the test piece which coat | covered the coating layer. It is a block diagram which shows the state which concerns on a comparative example and measures the electrical resistance of the thickness direction of the test piece which coat | covered the coating layer. It is a graph which shows the relationship between resistance and the temperature of heat processing concerning a test result. It is a graph which shows the result of XRD analysis.

Explanation of symbols

  In the figure, 1 is an iron powder particle, 2 is a coating layer, 3 is a ferrite powder particle, 4 is a ferrite layer, 6 is a green compact, and 7 is a soft magnetic compact.

Claims (9)

  A soft magnetic powder material comprising: iron powder particles containing iron as a main component; and a coating layer covering a surface of the iron powder particles and containing silicon oxide as a main component.   Comprising iron powder particles mainly composed of iron, a coating layer coated on the surface of the iron powder particles and mainly composed of silicon oxide, and a ferrite layer coated on the coating layer. A soft magnetic powder material, characterized in that the coating layer containing an oxide as a main component is interposed between the iron powder particles and the ferrite layer.   3. The iron powder particles according to claim 1, wherein the iron powder particles are pure iron (Fe), iron-aluminum system (Fe-Al system), iron-silicon system (Fe-Si system), iron-nickel system (Fe-Ni system). ), Iron-silicon-aluminum (Fe-Si-Al system), iron-chromium system (Fe-Cr system), and iron-cobalt system (Fe-Co system) Powder material.   A first step of preparing iron powder particles containing iron as a main component and a second step of covering the surface of the iron powder particles with a coating layer containing silicon oxide as a main component are sequentially performed. A method for producing a soft magnetic powder material.   A first step of preparing iron powder particles containing iron as a main component, a second step of coating the surface of the iron powder particles with a coating layer containing silicon oxide as a main component, and coating the ferrite layer on the coating layer And the 3rd process of interposing the said coating layer which has the said silicon oxide as a main component between the said iron powder particle and the said ferrite layer is implemented in order, The manufacturing method of the soft-magnetic powder material characterized by the above-mentioned.   6. The soft magnetic powder material manufacturing method according to claim 4, wherein the second step is performed through a contact operation in which the aqueous solution containing the inorganic silicon-containing compound is brought into contact with the iron powder particles. Method.   7. The method for producing a soft magnetic powder material according to claim 6, wherein the contact operation is performed while adding an alkali adjusting agent to the aqueous solution and setting the PH value of the aqueous solution to an alkaline region.   A soft magnetic molded body, wherein particles of a powder aggregate mainly composed of the soft magnetic powder material according to any one of claims 1 to 7 are bonded to each other.   By performing a pressurizing operation and a heating operation on the powder aggregate mainly composed of the soft magnetic powder material according to any one of claims 1 to 8 simultaneously or at different times. A method for producing a soft magnetic molded body, comprising forming a soft magnetic molded body.

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