JP5184182B2 - Method for producing Mg-containing oxide film-coated soft magnetic metal powder - Google Patents

Description

  The present invention relates to a method for producing a Mg-containing oxide film-coated soft magnetic metal powder, and in particular, using an oxidized soft powder such as iron powder and a magnesium powder to increase the thickness of the Mg-containing oxide film coating. The present invention relates to a production method capable of producing a Mg-containing oxide film-coated soft magnetic metal powder having a high Mg content ratio.

Conventionally, Mg-containing oxide film-coated soft magnetic metal powders are known as materials for various electromagnetic circuit components such as magnetic cores, motor cores, generator cores, solenoid cores, ignition cores, reactors, transformers, choke coil cores, or magnetic sensor cores. ing. Mg-containing oxide film-coated soft magnetic metal powder is manufactured by blending magnesium powder with oxidized iron powder to form a blended powder, and rolling this blended powder while heating in a vacuum atmosphere. (For example, refer to Patent Document 1).
JP 2006-241583 A

However, when an Mg-containing oxide film-coated soft magnetic metal powder is produced using a conventional method, an Mg-containing oxide film-coated soft magnetic metal powder with a sufficiently high Mg content cannot be obtained, and heat resistance and soft magnetic composite Insulating properties when used as a material may be insufficient.
In order to obtain a Mg-containing oxide film-coated soft magnetic metal powder having a high Mg content ratio, it is conceivable to increase the blending amount of magnesium powder contained in the blended powder as a raw material or to increase the heating time. However, it was difficult to increase the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder to a certain level or higher even if the blending amount of the magnesium powder was increased or the heating time was increased.

FIG. 4 (a) is a graph showing the relationship between the Fe concentration and the depth from the surface in the powder after the standard once treatment and the powder after the third treatment in which the same treatment as the standard one treatment was performed three times. FIG. 4B is a graph showing the relationship between the Mg concentration and the depth from the surface in the powder after the standard one-time treatment and the powder after the three-time treatment. In addition, the powder after the standard one-time treatment in FIGS. 4A and 4B is a ratio of 0.3% by mass of magnesium powder to the soft magnetic metal powder made of oxide-coated iron powder. Thus, it is the powder formed by heating the compounding powder formed by heating at a heat treatment temperature of 650 ° C. for 60 minutes. In addition, the powder after the three times treatment is a standard one-time treatment by newly adding magnesium powder to a ratio of 0.3% by mass with respect to the powder obtained by cooling once after the standard treatment. It is a powder obtained by performing heat treatment twice at the same temperature and time.
As shown in FIGS. 4 (a) and 4 (b), the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder should be increased to a certain level or more even when magnesium powder is added and heat treatment is performed multiple times. I couldn't.

 In order to obtain a Mg-containing oxide film-coated soft magnetic metal powder having a high Mg content ratio, it is conceivable to increase the thickness of the Mg-containing oxide film coating. In this case, the Mg content ratio can be improved, but there is a problem that the pretreatment time of the soft magnetic metal powder such as high-temperature heat treatment for oxidizing the iron powder must be increased, or the Mg-containing oxide film-coated soft magnetic There arises a problem that the soft magnetic properties of the metal powder deteriorate.

 The present invention has been made in view of the above problems, and without increasing the thickness of the Mg-containing oxide film coating, improves the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder, and has excellent soft magnetic properties. An object of the present invention is to provide a method for producing an Mg-containing oxide film-coated soft magnetic metal powder obtained by

The present inventor has intensively studied to solve the above problems.
That is, the present inventor assumed that magnesium vapor was excessive around the soft magnetic metal powder when the blended powder containing the soft magnetic metal powder and the magnesium powder was heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder. In addition, it was found that the Mg content ratio was not improved more than a certain level, and excess magnesium vapor was scattered. And, when the blended powder containing the soft magnetic metal powder and the magnesium powder is heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder to obtain a heat-treated powder, and magnesium vapor is supplied to the obtained heat-treated powder, it is obtained. The present inventors have found that the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder can be improved, and the present invention has been conceived. That is, the present invention relates to the following.

The method for producing a Mg-containing oxide film-coated soft magnetic metal powder according to the present invention comprises heating a blended powder containing a soft magnetic metal powder and a magnesium powder at a temperature equal to or higher than a vaporization temperature of the magnesium powder. A heat treatment step of forming a powder after heat treatment having an oxide film containing magnesium oxide formed on the surface thereof, and a steam supply step of supplying magnesium vapor to the powder after heat treatment, wherein the steam supply step comprises the powder after heat treatment And magnesium powder are spaced apart from each other in a container, the magnesium powder is heated to generate magnesium vapor, and the heat-treated powder is set to a temperature lower than the vaporization temperature of the magnesium powder, and the magnesium vapor is supplied to the heat-treated powder. It is a process .

 Further, in the method for producing the Mg-containing oxide film-coated soft magnetic metal powder, the temperature of the powder after the heat treatment is set to 400 ° C. or less before the vapor supplying step. .

 Moreover, it can be set as the method of setting the temperature of the said powder after the heat processing in the said vapor | steam supply process to less than the vaporization temperature of the said magnesium powder.

 In the method for producing the Mg-containing oxide film-coated soft magnetic metal powder, the steam supplying step disposes the heat-treated powder and the magnesium powder separately in a heating container, and the magnesium powder The method may be a step of heating to generate magnesium vapor and supplying magnesium vapor to the powder after the heat treatment.

  In the method for producing a Mg-containing oxide film-coated soft magnetic metal powder according to the present invention, the blended powder containing the soft magnetic metal powder and the magnesium powder is heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder to obtain the soft magnetic metal powder. A heat treatment step in which an oxide film containing magnesium oxide is formed on the surface of the heat treatment step and a steam supply step for supplying magnesium vapor to the post-heat treatment powder. The Mg content ratio can be improved in the steam supply step, and a Mg-containing oxide film-coated soft magnetic metal powder with a high Mg content ratio can be obtained. Therefore, according to the present invention, it is not necessary to increase the thickness of the Mg-containing oxide film coating.

 The method for producing a Mg-containing oxide film-coated soft magnetic metal powder according to the present invention includes a heat treatment step in which a compounded powder containing a soft magnetic metal powder and a magnesium powder is heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder to obtain a powder after heat treatment. And a steam supply step for supplying magnesium vapor to the powder after the heat treatment.

As the soft magnetic metal powder used in the present invention, conventionally known iron powder, insulated iron powder, Fe-Al iron-based soft magnetic alloy powder, Fe-Ni iron-based soft magnetic alloy powder, Fe -Cr-based iron-based soft magnetic alloy powder, Fe-Si-based iron-based soft magnetic alloy powder, Fe-Si-Al-based iron-based soft magnetic alloy powder, Fe-Co-based iron-based soft magnetic alloy powder, Fe-Co-V Iron-based soft magnetic alloy powder or Fe-P iron-based soft magnetic alloy powder.
The soft magnetic metal powder is preferably used after being oxidized in order to improve the coverage of magnesium. Examples of the oxidation treatment include a method in which heat treatment is performed at a temperature of 200 ° C. to 250 ° C. for 10 minutes to 30 minutes in the air.
The mixing ratio of the oxidized soft magnetic metal powder and the magnesium powder is preferably added so that the magnesium powder is 0.05 to 2% by mass with respect to the oxidized soft magnetic metal powder.

In the heat treatment step, for example, a vacuum heating furnace shown in FIG. 1 is used. A vacuum heating furnace 1 shown in FIG. 1 includes a heating container 2 and a heating means 3. As shown in FIG. 1, the heating container 2 has a substantially cylindrical shape and is provided with a length direction substantially horizontal, and a diameter-enlarged portion 2 a having an enlarged outer diameter is formed at the center. In the enlarged diameter portion 2a, a blended powder 5 containing a soft magnetic metal powder and a magnesium powder is accommodated. The heating container 2 is supported so as to be rotatable about a central axis 21 and is rotated around the central axis 21 by a driving device such as a motor (not shown) as indicated by an arrow in FIG. ing.
The heating container 2 is made of molybdenum, tantalum, or tungsten, or a molybdenum alloy containing a heat-resistant element such as titanium and zirconium as necessary, stainless steel, or the like.

 The heating means 3 is for heating the blended powder 5 accommodated in the heating container 2 from the outside of the heating container 2. The heating means 3 has a cylindrical shape, and is arranged coaxially with the central axis 21 of the heating container 2 so as to surround the outer peripheral surface of the heating container 2 on the outer side of the enlarged diameter portion 2 a of the heating container 2.

 In the heat treatment step using the vacuum heating furnace 1 shown in FIG. 1, the inside of the heating container 2 is evacuated, the heating container 2 is rotated and the mixed powder 5 is agitated, and the diameter of the expanded portion 2 a of the heating container 2 is increased by the heating means 3. By heating, the blended powder 5 is heated to a temperature equal to or higher than the vaporization temperature of the magnesium powder to obtain a powder after heat treatment in which an oxide film containing magnesium oxide is formed on the surface of the soft magnetic metal powder.

The heat treatment temperature in the heat treatment step is not particularly limited as long as it is equal to or higher than the vaporization temperature of the magnesium powder, but is preferably in the range of 500 ° C to 1100 ° C, and more preferably in the range of 500 ° C to 800 ° C.
Moreover, it is preferable that the heating time of the compounding powder 5 in a heat treatment process is 30 minutes-120 minutes.

 In this embodiment, before the vapor supply step, the heat-treated powder obtained by performing the heat treatment step is cooled by a method such as air cooling, and the temperature of the heat-treated powder is 400 ° C. or less, more preferably 200 ° C. The following cooling process is performed.

Subsequently, a steam supply process is performed. In the steam supply process of the present embodiment, for example, a vacuum heating furnace shown in FIG. 2 is used. A vacuum heating furnace 11 shown in FIG. 2 includes a heating container 12 and a heating means 13. The heating container 12 has a substantially cylindrical shape and is provided with a substantially horizontal length direction, and a diameter-enlarged portion 12a having an enlarged outer diameter is formed on the left side in FIG. A powder 51 after heat treatment is accommodated in the enlarged diameter portion 12a. Further, the right side of the heating container 12 in FIG. 2 is a small-diameter portion whose outer diameter is smaller than that of the enlarged-diameter portion 12 a and has a heating region 12 b that is heated by the heating means 13. As shown in FIG. 2, magnesium powder 52 is accommodated in the heating region 12b. Therefore, in the vacuum heating furnace 11 shown in FIG. 2, the post-heat treatment powder 51 and the magnesium powder 52 are arranged separately in one heating container 12.
The heating container 12 is supported so as to be rotatable about a central axis 21 as in the heating container 2 shown in FIG. 1, and as shown by an arrow in FIG. 2, a driving device such as a motor (not shown). Thus, it is rotated around the central axis 21.

 The heating means 13 includes a heater that heats the magnesium powder 52 accommodated in the heating region 12 b of the heating container 12 from the outside of the heating container 12. The heating means 13 has a cylindrical shape, and is arranged outside the heating region 12 b of the heating container 12 and coaxially with the central axis 21 of the heating container 12 so as to surround the outer peripheral surface of the heating container 12.

 In the steam supply process using the vacuum heating furnace 11 shown in FIG. 2, the inside of the heating vessel 12 is evacuated, the heating vessel 12 is rotated, and the heat-treated powder 51 is produced in the enlarged diameter portion 12a, and the magnesium powder 52 is produced in the heating region 12b. Are heated individually to a temperature equal to or higher than the vaporization temperature of the magnesium powder 52 by the heating means 13 to generate magnesium vapor. The obtained magnesium vapor is diffused in the heating container 12 and supplied to the powder 51 after the heat treatment. As a result, an Mg-containing oxide film-coated soft magnetic metal powder having a high Mg content can be obtained from the heat-treated powder 51 and magnesium vapor.

 The temperature of the magnesium powder 52 in the steam supply step is not particularly limited as long as it is equal to or higher than the vaporization temperature of the magnesium powder, but is preferably set to 500 ° C to 900 ° C, for example, in the range of 500 ° C to 800 ° C. More preferred. If the temperature is less than 500 ° C., magnesium vapor cannot be efficiently generated from the magnesium powder 52, which is not preferable. Moreover, when the said temperature exceeds 900 degreeC, the installation for performing a steam supply process will become expensive.

The temperature of the powder 51 after heat treatment in the steam supply step is preferably lower than the vaporization temperature of the magnesium powder, for example, preferably 20 ° C to 400 ° C, and more preferably 50 ° C to 200 ° C. .
Moreover, it is preferable that the supply time of the magnesium vapor | steam to the powder 51 after heat processing in a vapor | steam supply process is 30 minutes-120 minutes.

 Further, the amount of the magnesium powder 52 supplied to the heating region 12b in the steam supply step is 0.05 to 2% by mass with respect to the amount of the heat-treated powder 51 supplied to the enlarged diameter portion 12a. It is preferable to add.

 The Mg-containing oxide film coating thickness of the Mg-containing oxide film-coated soft magnetic metal powder obtained after the vapor supply step is preferably 50 nm to 200 nm, and more preferably 60 nm to 150 nm. If the thickness of the Mg-containing oxide film coating is less than the above range, the effect of improving the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder by the steam supply process may not be sufficiently obtained. If the thickness of the Mg-containing oxide film coating exceeds the above range, the magnetic flux density of the Mg-containing oxide film-coated soft magnetic metal powder may not be sufficiently obtained.

  The Mg-containing oxide film-coated soft magnetic metal powder thus obtained is molded into a predetermined shape at a predetermined temperature and pressure by adding a binder such as a resin, and fired at a predetermined temperature and pressure. Therefore, it is made into a soft magnetic composite material and used as various electromagnetic circuit components.

  In the manufacturing method of the Mg-containing oxide film-coated soft magnetic metal powder of the present embodiment, the blended powder 5 containing the soft magnetic metal powder and the magnesium powder is heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder 52, and the soft magnetic Since it has a heat treatment step for forming a powder 51 after heat treatment in which an oxide film containing magnesium oxide is formed on the surface of the metal powder, and a steam supply step for supplying magnesium vapor to the powder 51 after heat treatment, the heat treatment step provides The Mg content ratio of the powder 51 after heat treatment can be improved in the steam supply step, and an Mg-containing oxide film-coated soft magnetic metal powder with a high Mg content ratio is obtained.

  Moreover, in the manufacturing method of the Mg-containing oxide film-coated soft magnetic metal powder according to the present embodiment, when the cooling step of setting the temperature of the powder 51 after heat treatment to 400 ° C. or less is performed before the vapor supply step, Since the powder 51 can be made to be easily deposited with magnesium vapor by performing the vapor supplying step, an Mg-containing oxide film-coated soft magnetic metal powder having a still higher Mg content can be obtained.

  Further, when the temperature of the powder 51 after heat treatment in the steam supply step is lower than the vaporization temperature of the magnesium powder, magnesium vapor is likely to adhere to the powder 51 after heat treatment, so that the Mg content is further increased. An oxide film-coated soft magnetic metal powder is obtained.

  Further, in the present embodiment, the steam supplying step arranges the heat-treated powder 51 and the magnesium powder 52 separately in one heating container 12 and heats the magnesium powder 52 as shown in FIG. Since it is a step of generating magnesium vapor and supplying magnesium vapor to the powder 51 after heat treatment, an Mg-containing oxide film-coated soft magnetic metal powder having a high Mg content can be easily manufactured.

 Note that the cooling process and the steam supply process described above may be performed once or more after the heat treatment process, and the cooling process and the steam supply process may be repeated once more after the steam supply process. By performing the cooling step and the vapor supply step one or more times after the vapor supply step, the Mg-containing oxide film-coated soft magnetic metal powder having a higher Mg content can be produced.

"Example"
Table 1 shows a blended powder 5 containing soft magnetic metal powder and magnesium powder in the mixing ratio shown in Table 1 (shown as the ratio of magnesium powder to soft magnetic metal powder) using the vacuum heating furnace 1 shown in FIG. A heat treatment step was performed by heating at a heat treatment temperature for 120 minutes to obtain a powder 51 after the heat treatment.
Thereafter, if necessary, a cooling step was performed in which the heat-treated powder 51 obtained in the heat treatment step was cooled to the cooling temperature shown in Table 1 by air cooling.
Next, the heat-treated powder 51 after the cooling step is supplied to the diameter-enlarged portion 12a of the vacuum heating furnace 11 shown in FIG. 2, and the usage amount shown in Table 1 (the ratio of the magnesium powder 52 to the heat-treated powder 51 in the heating region 12b). Magnesium powder 52 is supplied, and the magnesium powder 52 is heated at the heating temperature shown in Table 1 for 60 minutes to perform a steam supply step of supplying magnesium vapor to the powder 51 after heat treatment. An oxide film-coated soft magnetic metal powder was obtained.

 As the soft magnetic metal powder, oxide-coated iron powder obtained by subjecting pure iron powder having an average particle diameter of 100 μm to heat treatment in the atmosphere at a temperature of 220 to 250 ° C. for 20 minutes was used.

The thickness of the Mg-containing oxide film coating of the Mg-containing oxide film-coated soft magnetic metal powders of Experimental Examples 1 to 15 thus obtained and the composition at a position 40 nm deep from the surface were determined as follows. . The results are shown in Table 1.
"Thickness of Mg-containing oxide coating"
The thickness of the film was measured by observing the cross section of the Mg-containing oxide film-coated soft magnetic metal powder with an electron microscope.
“Composition at a depth of 40 nm from the surface”
Measured with an Auger electron spectrometer.

For Experimental Example 1, regarding the post-heat treatment powder obtained after the heat treatment step and the Mg-containing oxide film-coated soft magnetic metal powder obtained after the vapor supply step, the relationship between the depth from the surface and the Mg concentration and Fe concentration was Examined. The result is shown in FIG.
FIG. 3 is a graph showing the relationship between the depth from the surface and the Mg and Fe concentrations. As shown in FIG. 3, the Mg-containing oxide film-coated soft magnetic metal powder and the heat-treated powder both have a lower Mg concentration and a higher Fe concentration as the depth from the surface increases.
However, the Mg-containing oxide film-coated soft magnetic metal powder has a higher Mg concentration and a lower Fe concentration than the heat-treated powder. Further, the difference between the Mg concentration and the Fe concentration between the Mg-containing oxide film-coated soft magnetic metal powder and the heat-treated powder increases as the depth increases in the range up to 80 nm from the surface. Further, as shown in FIG. 3, the difference in Mg concentration and Fe concentration between the Mg-containing oxide film-coated soft magnetic metal powder and the heat-treated powder is particularly large in the range of 20 nm to 100 nm from the surface. It is even larger in the range of 80 nm.

Further, a ring having an outer diameter of 35 mm, an inner diameter of 25 mm, and a thickness of 5 mm at a temperature of 150.degree. And was baked for 30 minutes at a temperature of 650 ° C. in a nitrogen atmosphere to obtain a soft magnetic composite material.
The density of the obtained soft magnetic composite material, the magnetic flux density, and the iron loss value at 1T and 400 Hz were measured. The results are shown in Table 1.

As shown in Table 1, in Experimental Examples 1 to 5 in which the steam supply process was performed after the cooling process at 200 ° C. or lower, the cooling process and the steam supply process were performed even when the Mg-containing oxide film coating had the same thickness. Compared with Experimental Example 12 in which the thickness is 40 nm, the Mg concentration at a depth of 40 nm from the surface is very high, and is equivalent to Experimental Example 15 in which the thickness when the cooling process and the steam supply process are not performed is 300 nm. The Mg concentration is 40 nm deep from the surface. Therefore, it can be seen that the Mg content ratio of the Mg-containing oxide film-coated soft magnetic metal powder can be improved without increasing the thickness of the Mg-containing oxide film coating by performing the cooling step and the steam supply step.
Moreover, in Experimental Examples 1-5, compared with Experimental Example 9 and 10 whose cooling temperature is 200 degreeC-400 degrees C or less, and Experimental Example 11 whose cooling temperature is 400 degreeC or more, it is 40 nm deep from the surface. The Mg concentration is high. Therefore, it is understood that the cooling temperature is preferably 400 ° C. or lower, and more preferably 200 ° C. or lower.
Moreover, in Experimental Examples 1-11 which performed the steam supply process, the iron loss value was small compared with Experimental Examples 12-15 which did not perform the cooling process and the steam supply process. Further, in Experimental Examples 14 and 15 in which the cooling process and the steam supply process were not performed, the Mg concentration at a depth of 40 nm from the surface was 47% by mass or more, but the thickness of the Mg-containing oxide film coating was large. The material density and magnetic flux density were low.

FIG. 1 is a schematic configuration diagram showing an example of a vacuum heating furnace used in the method for producing an Mg-containing oxide film-coated soft magnetic metal powder of the present invention. FIG. 2 is a schematic configuration diagram showing an example of a vacuum heating furnace used in the method for producing a Mg-containing oxide film-coated soft magnetic metal powder of the present invention. FIG. 3 is a graph showing the relationship between the depth from the surface and the Mg and Fe concentrations. FIG. 4 (a) is a graph showing the relationship between the Fe concentration and the depth from the surface in the powder after the standard once treatment and the powder after the third treatment in which the same treatment as the standard one treatment was performed three times. FIG. 4B is a graph showing the relationship between the Mg concentration and the depth from the surface in the powder after the standard one-time treatment and the powder after the three-time treatment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Vacuum heating furnace, 2,12 ... Heating container, 2a, 12a ... Diameter expansion part, 2b ... Other end part, 3,13 ... Heating means, 5 ... Compounding powder, 12b ... Heating area, 51 ... After heat processing Powder, 52 ... magnesium powder.

Claims (2)

A powder after heat treatment in which a compounded powder containing a soft magnetic metal powder and a magnesium powder is heated at a temperature equal to or higher than the vaporization temperature of the magnesium powder to form an oxide film containing magnesium oxide on the surface of the soft magnetic metal powder. A heat treatment step,
A steam supply step of supplying magnesium vapor to the powder after the heat treatment ,
In the steam supply step, the heat-treated powder and the magnesium powder are disposed separately in a container, the magnesium powder is heated to generate magnesium vapor, and the heat-treated powder is set to a temperature lower than the vaporization temperature of the magnesium powder. A method for producing an Mg-containing oxide film-coated soft magnetic metal powder, characterized by being a step of supplying magnesium vapor to the powder after the heat treatment . The method for producing an Mg-containing oxide film-coated soft magnetic metal powder according to claim 1, wherein the temperature of the powder after the heat treatment is set to 400 ° C or lower before the vapor supplying step.

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