JP6164512B2 - Fe-based soft magnetic metal powder - Google Patents

Description

  The present invention relates to an Fe-based soft magnetic metal powder, and more particularly to an Fe-based soft magnetic metal powder for a magnetic member such as a magnetic core used in a magnetic component for high frequency.

  High magnetic permeability materials such as oxide ferrite are used for magnetic cores of magnetic components such as choke coils and inductors. In recent years, in electronic devices such as mobile communication devices, the frequency range has shifted to the high frequency side, and magnetic components suitable for operation in such a frequency range are required. Here, when the frequency of the current flowing through the coil wound around the magnetic core increases, the eddy current loss due to the eddy current generated by the magnetic field applied to the magnetic core tends to increase. In particular, in a magnetic core made of oxide ferrite, eddy current loss rapidly increases in a frequency range of several kHz or more. The energy corresponding to the eddy current loss lowers the operating efficiency of the magnetic component and is released as heat from the magnetic core, which is an obstacle to downsizing the electronic device.

  As a magnetic core capable of reducing eddy current loss, a magnetic core obtained by molding a metal powder made of a soft magnetic metal together with an insulating resin is widely known. By insulating the soft magnetic metal powder particles with an insulating resin to increase the specific resistance of the magnetic core, eddy currents generated in the magnetic core can be suppressed and eddy current loss can be reduced. In addition, the component composition of soft magnetic metal can be selected widely if it can be pressure-molded, so core loss (iron loss) including eddy current loss can be effectively suppressed. It is preferable as a magnetic core used for a magnetic component for high frequency.

  For example, in Patent Document 1, gas atomized metal powder containing Fe: mass%, Si: 7-9%, Cr: -5% and organic polymer as an insulating resin are mixed and injection molded in Fe. The resulting magnetic core is disclosed. A metal powder with a prescribed component composition obtained by gas atomization after mentioning that it is difficult to heat-treat the molded product after injection molding using an organic polymer as a binder for the metal powder so as not to lose its shape. Describes that the distortion of the metal powder can be made relatively small without performing heat treatment, and the oxidation can be suppressed to a small extent, so that iron loss can be suppressed. Further, it is stated that the metal powder obtained by the gas atomization method tends to be spherical, has excellent mixing and dispersibility in an organic polymer, and is preferable for injection molding. Here, regarding Si, if the content in a predetermined range is deviated in Fe, the iron loss is increased due to accumulation of strain in the metal powder by kneading or injection molding. Also, Cr is arbitrarily added to reduce iron loss.

  For example, in Patent Document 2, an insulating resin (binder) is mixed with water atomized metal powder containing Fe: Si: 3 to 10% and Cr: 3 to 10% by mass in Fe and press-molded. A powder magnetic core obtained as described above is disclosed. The water atomized metal powder in the vicinity of zero magnetostriction containing a relatively large amount of Si in Fe has high hardness, it is difficult to press-mold a dust core at high density, and low permeability It is disclosed that the metal powder is previously heat-treated in a reducing atmosphere containing hydrogen. By this heat treatment, the oxide layer on the surface of the metal powder is reduced, the hardness is reduced to ensure formability, the magnetic permeability can be increased, and the iron loss can be improved. Here, it is stated that when Si is given out of a predetermined range in Fe, magnetostriction increases and iron loss increases. Further, it is described that Cr is added to suppress rust, discoloration, and change with time, and that iron loss increases when Fe is added so as to relatively reduce the content of Fe.

JP 2009-176974 A JP 2010-272604 A

  As described above, a magnetic member such as a magnetic core using a Fe-Si-Cr-based metal powder can obtain a high magnetic permeability, has a small iron loss, and is excellent in corrosion resistance. It is preferable as a magnetic member of a magnetic core used for magnetic parts.

  The present invention has been made in view of such a situation, and the object is to obtain a higher magnetic permeability in a magnetic member such as a magnetic core using an Fe-Si-Cr-based metal powder, And it is providing the Fe group soft magnetic metal powder which can suppress an iron loss small.

  The Fe-based soft magnetic metal powder according to the present invention contains, in Fe, mass%, Si: 7 to 9%, Cr: 2 to 8% together with inevitable impurities, and an average particle diameter D50 of 1 to 40 μm. The oxygen content is suppressed to 0.60% by mass or less.

  According to this invention, in a magnetic member such as a magnetic core obtained by molding together with a binding material, higher magnetic permeability can be obtained, iron loss can be suppressed, and corrosion resistance is excellent.

It is a figure which shows the manufacturing method of a soft magnetic metal powder and a magnetic core. It is a figure which shows the evaluation test result of a dust core. It is a perspective view of the magnetic core used for the evaluation test.

  The soft magnetic metal powder according to the present invention is made of an Fe—Si—Cr alloy having a predetermined component composition. Even when a magnetic member such as a magnetic core is obtained by a known molding method together with an insulating bonding material by suppressing the oxygen amount to a certain value or less at a predetermined average particle size, a conventional powder having the same component composition High magnetic permeability and low iron loss can be achieved as compared with a magnetic member produced by the same molding method using the. Moreover, it is very excellent also in corrosion resistance. Examples of the known molding method include a method of pressure molding with a press machine, a method of injection molding with an injection molding machine, a method of transfer molding, and a casting molding method such as potting. Also, the present invention can be applied to a method in which a soft magnetic metal powder is mixed with a binding material to form a paste-like paint and a magnetic member is obtained by printing. A magnetic member made of such a composite magnetic material is particularly suitable for use in high-frequency magnetic parts. A method for producing a soft magnetic metal powder according to one embodiment of the present invention and a method for producing a magnetic member such as a magnetic core using the same will be described below with reference to FIG.

  As shown in FIG. 1A, a mother alloy made of an Fe—Si—Cr alloy having a predetermined component composition is prepared, and a soft magnetic metal powder 1 is produced by a water atomization method. That is, vacuum deaerated water in which dissolved oxygen is reduced by a vacuum deaerator is ejected from the nozzle at a high speed, and the molten metal 3 in which the mother alloy is melted is dropped by gravity toward the nozzle tip. The molten metal 3 is cooled and solidified while being scattered, and is obtained as a fine soft magnetic metal powder 1 in a vacuum deaerated water pool below the nozzle. The particle diameter of the soft magnetic metal powder 1 can be adjusted by adjusting the amount of vacuum degassed water ejected from the nozzle. Here, as the Fe—Si—Cr-based alloy, the soft magnetic metal powder 1 as an example of the present invention containing Si: 7 to 9% and Cr: 2 to 9% by mass in Fe is used. If the average particle size D50 is 1 to 40 μm, the oxygen content of the soft magnetic metal powder 1 can be suppressed to 0.60 mass% or less as described later.

  The method of obtaining the magnetic core 10 from the soft magnetic metal powder 1 is not limited to this. For example, as shown in FIG. 1B, an insulating resin 2 is bonded to the soft magnetic metal powder 1 as a binder. Are mixed, filled into a mold having a predetermined shape, and press-molded with a press. When the resin 2 is cured by taking out from the mold and heat-treated, the magnetic core 10 can be obtained.

  Next, the results of various evaluation tests will be described for the magnetic core 10 made of the soft magnetic metal powder made of the Fe—Si—Cr alloy having the component composition shown in FIG.

  First, soft magnetic metal powder having the component composition shown in FIG. 2 was prepared by the water atomization method. Here, the water used for the water atomization method is vacuum deaerated water obtained by reducing the dissolved oxygen in water using a commercially available vacuum deaerator except for Comparative Example 1. Typically, the amount of dissolved oxygen in the vacuum degassed water is 0.5 ppm or less. On the other hand, in Comparative Example 1, general industrial water was used. The obtained powder was classified so that, except for Examples 7 and 8, the average particle diameter D50 was about 11 to 12 μm. In addition, in FIG. 2, the result of the average particle diameter D50 of the soft-magnetic metal powder measured with the laser diffraction type particle size distribution measuring apparatus was shown collectively.

  Furthermore, the oxygen content of the soft magnetic metal powder was measured by an inert gas melting method-infrared absorption method according to JIS Z2613 using an oxygen / nitrogen analyzer manufactured by LECO, and is shown in FIG.

For real magnetic permeability, iron loss, and corrosion resistance, the above soft magnetic metal powder was processed into a ring-shaped toroidal core 10 having an outer diameter of φ19 mm, an inner diameter of φ13 mm, and a thickness of 4.8 mm as shown in FIG. The measurement was performed. That is, an epoxy resin having a mass fraction of 2.5% was added to the soft magnetic metal powder as a binder, and the soft magnetic metal powder was mixed and dispersed in the epoxy resin and filled in a mold. This was compression-molded at a surface pressure of 6 ton / cm ² and held at 170 ° C. in the air for 1 hour to cure the epoxy resin, thereby producing the core 10.

The real magnetic permeability was measured under conditions of a frequency of 1 MHz and 0.5 mA using an LCR meter (E4980A) manufactured by Agilent Technologies, with a 40-turn winding provided to the core 10. In consideration of the permeability required for the obtained magnetic core, the target value of the real permeability of the core 10 in this evaluation test was set to 25 or more. In addition, the iron loss was measured by using a BH analyzer (SY-) manufactured by Iwatsu Measurement Co., Ltd. using the same core 10 provided with 40 turns of winding on the primary side and 8 turns of winding on the secondary side. 8258) was measured under the conditions of a magnetic flux density of 0.05 T and a frequency of 500 kHz. Here, the target value of the core loss of the core 10 in this evaluation test was set to 6000 kw / m ³ or less. The respective measurement results are also shown in FIG.

  Corrosion resistance was evaluated by visually observing the surface of the core 10 after 96 hours by a salt spray test according to JIS C60068-2-11. Although the evaluation results are also shown in FIG. 2, when discoloration can be confirmed in the core 10, it is determined that the corrosion resistance is lower than the corrosion resistance required for the magnetic core, “None”, otherwise In the case of, it was determined that the required corrosion resistance was satisfied, and indicated as “present”.

In the above, first, in Comparative Example 1 using industrial water and Example 1 using vacuum deaerated water in the water atomization method, the component composition of the soft magnetic metal powder is equivalent (Si: 8% by mass) , Cr: 5% by mass), the oxygen content was 0.67% by mass in Comparative Example 1 and 0.27% by mass in Example 1. The real magnetic permeability was 21 in Comparative Example 1, whereas it increased to 29 in Example 1 to satisfy the target value. Also, the iron loss, while was 8358kw / ^{m 3} in Comparative Example 1, as small as 4713kw / ^{m 3} in Example 1, was satisfied the target value. That is, by suppressing the amount of oxygen contained in the soft magnetic metal powder, the magnetic permeability can be increased and the iron loss can be reduced.

  In general, the powder produced by the water atomization method is likely to be a powder having irregularities on the surface and a large surface area ratio. That is, the surface is easily oxidized. On the other hand, the soft magnetic metal powder 1 has an average particle diameter D50 before classification of 1 to 40 μm, and can obtain a relatively spherical powder even in the water atomization method. It is considered that the amount of oxygen contained in the powder 1 could be suppressed.

  Next, when Example 1 thru | or Example 4, and Comparative Example 2 and Comparative Example 3 which changed Cr amount in a Fe-Si-Cr type-alloy are compared, in Comparative Example 2 which made Cr content 1 mass%, In the salt spray test, discoloration due to rust was observed in the form of dots. That is, the corrosion resistance is judged as “none”. Moreover, in the comparative example 3 which made content of Cr 9 mass%, the real number magnetic permeability was 24 and was lower than the target value. In contrast, in Example 2 in which the Cr content was 2% by mass, Example 3 in which the Cr content was 4% by mass, and Example 4 in which the Cr content was 8% by mass, salt spray Discoloration in the test was not observed, and in all cases, the corrosion resistance was judged as “present”, and the real permeability and iron loss satisfied the target values.

Next, when Example 1, Example 5, Example 6, Comparative Example 4 and Comparative Example 5 in which the amount of Si in the Fe—Si—Cr alloy was changed were compared, the Si content was 6.5 mass%. In both Comparative Example 4 and Comparative Example 5 in which the Si content was 10% by mass, the real magnetic permeability was 30 and 27, respectively, and the target value was satisfied, but the iron loss was 6635 kw / m. ³ and 6247 kw / m ³ , which were larger than the target values. On the other hand, in Examples 5, 1, and 6 in which the Si content was 7, 8, and 9% by mass, the real permeability was as high as 30, 29, and 28, satisfying the target value, and the iron loss was 5554 kW. / M ³ , 4713 kw / m ³ and 5290 kw / m ³ were small and satisfied the target value. In other words, there is an optimum value of the Si amount, and if it deviates from this, the iron loss is increased.

Next, when Example 1, Example 7 and Example 8 in which the average particle diameter D50 was changed were compared, Example 1, in which the average particle diameter D50 was 11.2 μm, 23.9 μm, and 34.2 μm, respectively. In Example 7 and Example 8, the real magnetic permeability, 29, 32, and 35, satisfy the target values, respectively, and tend to increase as the average particle diameter D50 increases. In Example 1, Example 7, and Example 8, the iron loss was 4713 kw / m ³ , 5283 kw / m ³ , and 5749 kw / m ³ , all of which met the target values, but with the average particle diameter D50 It has a tendency to become large.

  By the way, as described above, the range of the component composition of the soft magnetic metal powder 1 according to the present invention is determined as follows in consideration of the magnetic characteristics and corrosion resistance required for the magnetic core 10 obtained therefrom.

  Si increases the iron loss of the obtained magnetic core 10 even if the content is too much or too little. That is, Si is in the range of 7 to 9% by mass%.

  Cr imparts corrosion resistance to the magnetic core 10. On the other hand, when it becomes excessive, the magnetic permeability of the magnetic core 10 obtained will be reduced and the iron loss will be increased. Therefore, Cr is in the range of 2 to 8% by mass%.

  In addition, about inevitable impurities, as a range which does not impair the magnetic characteristic and corrosion resistance of the above-mentioned magnetic core 10, in mass%, C: 0.04% or less, Mn: 0.3% or less, P: 0.06% or less S: 0.06% or less, N: 0.06% or less, Cu: 0.05% or less, Mo: 0.05% or less, Ni: 0.1% or less.

  Further, as described above, oxygen contained in the soft magnetic metal powder 1 according to the present invention is determined as follows in consideration of magnetic characteristics required for the magnetic core 10 obtained from the oxygen. That is, oxygen mainly forms an oxide, lowers the magnetic permeability of the magnetic core 10 obtained, and increases iron loss. Therefore, the oxygen content is 0.60% or less, preferably 0.50% or less, in mass%.

  Furthermore, as described above, the average particle diameter D50 of the soft magnetic metal powder 1 according to the present invention is determined as follows in consideration of the magnetic characteristics required for the magnetic core 10 obtained therefrom. That is, when the average particle diameter D50 is small, the eddy current in the magnetic core 10 can be suppressed when the coil is applied to the obtained magnetic core 10, and in particular, even if the current flowing through the coil is shifted to the high frequency side, it is generated in the magnetic core 10. The eddy current can be suppressed and eddy current loss can be reduced. However, if it is too small, the magnetic permeability of the obtained magnetic core 10 will be reduced. Therefore, the average particle diameter D50 is in the range of 1 to 40 μm.

  The exemplary embodiments according to the present invention have been described so far, but the present invention is not necessarily limited thereto. Those skilled in the art will recognize a variety of alternative embodiments and modifications without departing from the scope of the appended claims.

1 Soft magnetic metal powder 10 Core (magnetic core)

Claims (1)

A water-atomized metal powder having an uneven surface, while Fe, in mass%, Si: 8~9%, Cr : 4 ~8% together with unavoidable impurities of the magnetic member made of an alloy of including chemical composition Fe-based soft magnetic metal powder for
An Fe-based soft magnetic metal powder characterized in that the average particle diameter D50 is 1 to 40 μm and the amount of oxygen is suppressed to a range of 0.19 to 0.60 mass%.

Images