JP2022031111A - METHOD FOR PRODUCING Fe-BASED NANOCRYSTAL ALLOY POWDER AND Fe-BASED AMORPHOUS ALLOY - Google Patents

Abstract

To provide a method for producing Fe-based nanocrystal alloy powder capable of obtaining satisfactory magnetic properties by suppressing the coarsening of crystal grains and the precipitation of Fe2B crystals while generating bcc-Fe(Si) fine crystals.SOLUTION: A method for producing Fe-based nanocrystal alloy powder has a process in which Fe-based amorphous alloy powder is heat-treated under the conditions that the average temperature rising speed from 300°C to 400°C upon the temperature rising of Fe-based amorphous alloy powder is defined as TA and the average temperature rising speed from 400°C to the maximum temperature is defined as TB, TA is 2 to 10°C/min, TB is 1.5 to 8°C/min and also TA>TB.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing an Fe-based nanocrystalline alloy powder and an Fe-based amorphous alloy.

By heat-treating the Fe-based amorphous alloy produced for the Fe-based nanocrystal alloy, fine crystals can be precipitated in the Fe-based amorphous alloy to obtain an Fe-based nanocrystal alloy having fine crystals.
Generally, the Fe-based amorphous alloy is obtained as a thin band-shaped Fe-based amorphous alloy (Fe-based amorphous alloy thin band) by quenching and solidifying the molten alloy by a single roll method or the like. When constructing the magnetic core of the Fe-based nanocrystalline alloy, first, the Fe-based amorphous alloy strip is formed into a shape such as a magnetic core. Next, the Fe-based amorphous alloy strip formed into a magnetic core shape is subjected to a heat treatment including in a magnetic field to precipitate fine crystal grains on the Fe-based amorphous alloy strip. Thereby, a magnetic core made of an Fe-based nanocrystal alloy strip having good magnetic properties can be obtained (see, for example, Patent Document 1).

Since the form of the Fe-based nanocrystal alloy obtained by the single roll method or the like is a thin band, the degree of freedom in the shape of the magnetic core that can be produced is limited. That is, the alloy strip is slit to a width corresponding to the desired height of the magnetic core, and the alloy strip is wound and formed according to the desired inner and outer diameters. Therefore, the shape is a toroidal shape. , Limited to race track shapes, etc.
On the other hand, conventionally, there are demands for various magnetic core shapes. Therefore, if the Fe-based nanocrystalline alloy can be produced as a powder, magnetic cores having various shapes can be relatively easily formed by applying a forming method such as pressing or extrusion. Therefore, studies have been made to obtain powder even in Fe-based nanocrystal alloys. (See, for example, Patent Document 2)

Special Fair No. 4-4393 Gazette Japanese Unexamined Patent Publication No. 2017-95773

When a Fe-based amorphous alloy is heat-treated to precipitate fine crystals (hereinafter, also referred to as nanocrystals) to obtain a Fe-based nanocrystal alloy, rapid heating is performed during the heat treatment in order to obtain a nanocrystal structure having excellent magnetic properties. Need to be applied. However, in the heat treatment of the Fe-based amorphous alloy powder, heat is generated when nanocrystals are precipitated in the amorphous region in the powder. During the heat treatment of the Fe-based amorphous alloy powder, the heating by rapid heating and the heat generated by the nanocrystallization in the powder overlap, which may cause the temperature of the powder to rise excessively. As described above, when the temperature of the powder rises excessively, the temperature of the powder exceeds an appropriate heat treatment temperature, resulting in coarsening of crystal grains and precipitation of Fe _2B crystals. As a result, Fe-based nanocrystalline alloy powder having good magnetic properties cannot be obtained.
An object of the present disclosure is to provide a method for producing Fe _- based nanocrystal alloy powder, which can obtain good magnetic properties by suppressing coarsening of crystal grains and precipitation of Fe 2B crystals while generating fine crystals. do.
Another object of the present invention is to provide an Fe-based amorphous alloy suitable for use in the method for producing the Fe-based nanocrystalline alloy powder of the present disclosure.

Specific means for solving the above problems include the following aspects.
<1> A method for producing Fe-based nanocrystalline alloy powder by heat-treating Fe-based amorphous alloy powder to produce Fe-based nanocrystalline alloy powder.
When the average temperature rise rate from 300 ° C. to 400 ° C. when the temperature of the Fe-based amorphous alloy powder is raised is TA, and the average temperature rise rate from 400 ° C. to the maximum temperature is TB, TA is 2 ° C./min to A method for producing an Fe-based nanocrystalline alloy powder by heat-treating the Fe-based amorphous alloy powder under the conditions of 10 ° C./min, TB of 1.5 ° C./min to 8 ° C./min, and TA> TB. ..
<2> A Fe-based nanocrystal alloy powder having bcc-Fe (Si) fine crystals having a crystal grain size of 100 nm or less and having 50% by volume or more of the bcc-Fe (Si) fine crystals is produced. <1 > The method for producing an Fe-based nanocrystalline alloy powder.
<3> The composition of the Fe-based nanocrystalline alloy powder is 3 to 8% for Si, 11 to 17% for B, 0.7 to 1.8% for Cu, and 0.05 to 0% for Sn in terms of atomic ratio. It is represented by 7%, Cr is 0 to 1.5%, Nb is 0 to 1.0%, Mo is 0 to 1.0%, and the balance, and the balance is <1> or <which consists of Fe and impurities. A method for producing an Fe-based nanocrystalline alloy powder according to 2>.
<4> As the Fe-based amorphous alloy powder, a powder made of an Fe-based amorphous alloy in which fine crystals of Cu having a diameter of 50 nm or less are dispersed in the amorphous phase is used. The method for producing an Fe-based nanocrystalline alloy powder according to any one item.
<5> The Fe-based nanocrystal alloy powder according to <4>, wherein the Cu microcrystals are present in the range of 1 × 10 ^-4 pieces / nm ² or more and 6 × 10 ^-4 pieces / nm ² or less. Production method.
<6> An Fe-based amorphous alloy in which fine crystals of Cu having a diameter of 50 nm or less are dispersed in an amorphous phase.
<7> The Fe-based amorphous alloy according to <6>, wherein the Cu microcrystals are present in the range of 1 × 10 ^-4 pieces / nm ² or more and 6 × 10 ^-4 pieces / nm ² or less.
<8> The composition of the Fe-based amorphous alloy is 3 to 8% for Si, 11 to 17% for B, 0.7 to 1.8% for Cu, and 0.05 to 0.7% for Sn in terms of atomic ratio. , Cr is 0 to 1.5%, Nb is 0 to 1.0%, Mo is 0 to 1.0%, and the balance is represented by the balance, which is composed of Fe and impurities <6> or <7>. The Fe-based amorphous alloy according to.

According to the present disclosure, it is possible to obtain a method for producing Fe _- based nanocrystal alloy powder, which can obtain good magnetic properties by suppressing coarsening of crystal grains and precipitation of Fe 2B crystals while producing fine crystals. Further, according to the present disclosure, an Fe-based amorphous alloy suitable for use in the method for producing the Fe-based nanocrystalline alloy powder of the present disclosure can be obtained.

6 is a transmission electron microscope observation image of the Fe-based nanocrystalline alloy powder of Example 1. It is a transmission electron microscope observation image of the Fe-based amorphous alloy of this Example. It is a schematic diagram of FIG.

Hereinafter, the present disclosure will be specifically described with reference to the embodiments of the present disclosure, but the present disclosure is not limited to these embodiments.
When the embodiments of the present disclosure are described with reference to the drawings, the description of overlapping components and reference numerals in the drawings may be omitted. The components shown by the same reference numerals in the drawings mean that they are the same components.

In the present disclosure, the numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the lower limit value and the upper limit value, respectively. In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. ..
In the present disclosure, the Fe-based amorphous alloy powder is a powder made of a Fe-based amorphous alloy.

In the method for producing an Fe-based nanocrystalline alloy powder according to an embodiment of the present disclosure, the average temperature rise rate from 300 ° C. to 400 ° C. when the temperature of the Fe-based amorphous alloy powder is raised is set to TA, and the temperature is raised from 400 ° C. to the maximum temperature. When the average temperature rise rate of is TB, TA is 2 ° C./min to 10 ° C./min, TB is 1.5 ° C./min to 8 ° C./min, and TA> TB. This is a method for producing an Fe-based nanocrystalline alloy powder by heat-treating an Fe-based amorphous alloy powder. This Fe-based amorphous alloy powder is an Fe-based amorphous alloy powder for Fe-based nanocrystalline alloy powder produced so as to become an Fe-based nanocrystalline alloy powder by heat treatment.

In one embodiment of the present disclosure, the Fe-based nanocrystal alloy powder has bcc-Fe (Si) fine crystals (hereinafter, also referred to as "bcc-Fe fine crystals" or "nanocrystals"). The bcc-Fe fine crystals of the Fe-based nanocrystal alloy powder preferably have a crystal grain size of 100 nm or less. The bcc-Fe fine crystals preferably have an average crystal grain size of 10 to 50 nm. Further, the Fe-based nanocrystal alloy powder of the present disclosure preferably contains 50% by volume or more of bcc-Fe fine crystals. In the Fe-based nanocrystal alloy powder, the portion other than the bcc—Fe fine crystals may be an amorphous phase. Here, for the volume fraction of the bcc-Fe fine crystals, the alloy structure of the Fe-based nanocrystal alloy powder is observed with a transmission electron microscope (TEM), and the areas of the substantially spherical structures (bcc-Fe fine crystals) are totaled. , Can be calculated from the ratio to the observation field area.

In one embodiment of the present disclosure, the composition of the Fe-based nanocrystalline alloy powder is such that Si is 3 to 8%, B is 11 to 17%, Cu is 0.7 to 1.8%, and Sn is 0. It is preferably represented by 05 to 0.7%, Cr of 0 to 1.5%, Nb of 0 to 1.0%, Mo of 0 to 1.0%, and the balance. Here, the balance consists of Fe and impurities. In addition, Cr, Nb, and Mo may be 0% respectively.
When the composition of the Fe-based nanocrystal alloy powder is this composition, the Fe-based nanocrystal alloy powder obtained by the heat treatment method of the present disclosure can stably provide a nanocrystal structure having excellent magnetic properties.
Further, in the embodiment of the present disclosure, it is preferable that the Fe-based amorphous alloy powder for the Fe-based nanocrystalline alloy powder and the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder have the same composition.

Two important factors are required for the appearance of nanocrystal structures by the heat treatment method of the present disclosure. The first is that in the temperature range of 300 ° C to 400 ° C when the temperature rises, a phase different from the amorphous phase mainly composed of Cu and Sn, which is the core of nanocrystals (hereinafter, also referred to as “heterogeneous phase”) is sufficient. It exists in a number density. This is largely related to the amount of Cu and the amount of Sn. The total content (atomic%) of Cu and Sn is preferably 1.2 atomic% or more, more preferably 1.3 atomic% or more. This gives a heterogeneous phase with a sufficient number density. Further, when the total of them is 1.85 atomic% or less, the coarsening of the cluster can be suppressed and the high number density is maintained. Further, the total of Cu and Sn is preferably 1.8 atomic% or less.

The second is the range of overheating in the temperature range of 400 ° C. or higher at the time of temperature rise. Here, the overheating means that the temperature of the powder exceeds the target heat treatment temperature. In the crystallization of the amorphous phase, heat is generated by collective crystallization, which causes excessive temperature rise in the temperature range of 400 ° C. or higher. According to the manufacturing method of the present disclosure aiming at both production efficiency and magnetic characteristics, even if an overheating occurs, the range of the overheating is suppressed to about 20 to 30 ° C., coarsening of crystal grains and Fe ₂ Precipitation of B crystals can be suppressed. At that time, if the thermal stability of the residual amorphous phase is high, excessive crystal grain growth can be suppressed and non-uniformity of excessive temperature rise can be tolerated, and the desired powder can be easily obtained. B, Nb, Mo, and Si are largely related to the improvement of the thermal stability of the residual amorphous phase. Therefore, it is necessary to contain an appropriate amount of B, Si, Nb, and Mo. Therefore, it is preferable that B is 11 atomic% or more and Si is 3 atomic% or more. Further, it is more preferable that B is 13 atomic% or more and Si is 4 atomic% or more. Although Nb and Mo are not essential elements, it is preferable to contain at least one of Nb and Mo. When Nb or Mo is contained, it is more preferably 0.2 atomic% or more.

Further, the amount of Fe greatly affects the saturation magnetic flux density, and a higher content allows a higher saturation magnetic flux density to be obtained. Therefore, the amount of Fe is preferably 89% by weight or more, more preferably 90% by weight or more. In terms of atomic ratio, the Fe amount is preferably 78% or more, more preferably 80% or more.

Hereinafter, the process order of the method for producing the Fe-based nanocrystalline alloy powder according to the embodiment of the present disclosure will be described.
In the present disclosure, when producing Fe-based nanocrystalline alloy powder, first, Fe-based amorphous alloy powder for Fe-based nanocrystalline alloy powder is produced. Next, the Fe-based nanocrystalline alloy powder is produced by heat-treating the Fe-based amorphous alloy powder. This is in line with the method of first producing an Fe-based amorphous alloy and then heat-treating the Fe-based amorphous alloy to produce an Fe-based nanocrystalline alloy when producing a Fe-based nanocrystalline alloy.

First, the Fe-based amorphous alloy powder used in this embodiment will be described.
The Fe-based amorphous alloy powder used in this embodiment is a powder made of an Fe-based amorphous alloy, and can be obtained by quenching and solidifying the molten alloy by an atomizing method or the like. At this time, the molten alloy is adjusted to the alloy composition for obtaining the desired Fe-based nanocrystalline alloy powder.

<Alloy molten metal>
The molten alloy is prepared by blending each element source such as pure iron, ferroboron, and ferrosilicon so as to have a desired alloy composition, and heating and melting to the melting point of the alloy in an induction heating furnace or the like. This makes it possible to obtain an alloy molten metal having an alloy composition of the desired Fe-based nanocrystalline alloy powder.

<Atomize method>
As a method for producing Fe-based amorphous alloy powder, there is an atomizing method in which a medium such as gas or water is made to collide with a molten alloy at high speed to be pulverized. The Fe-based amorphous alloy powder of the present embodiment can also be produced by using the atomizing method.
For example, an atomizing method using the manufacturing apparatus (jet atomizing apparatus) described in JP-A-2017-155341 can be used.
Various atomizing methods are known, and the production conditions thereof can be appropriately selected from known production techniques to obtain an Fe-based amorphous alloy.

Further, in the present embodiment, it is preferable to produce an Fe-based amorphous alloy powder by using, for example, the metal powder production apparatus described in International Publication No. 2019/49965.
The Fe-based amorphous alloy powder of the present embodiment is obtained by quenching and solidifying the molten alloy. Therefore, after crushing the molten alloy, it is necessary to quickly solidify and cool the crushed fine powder (melted alloy). Therefore, water or solvent with high cooling capacity is adopted, and the water or solvent with high cooling capacity is sprayed onto the crushed fine powder (alloy molten metal), or the crushed fine powder (alloy molten metal) is cooled. It is preferable to plunge into high water or solvent.
The metal powder manufacturing apparatus described in International Publication No. 2019/49965 uses a swirling water flow and is suitable for quenching and solidifying a molten alloy.

<Fe-based amorphous alloy and Fe-based amorphous alloy powder>
The Fe-based amorphous alloy powder in the present disclosure is an alloy powder having an amorphous phase. In the Fe-based amorphous alloy constituting the alloy powder having the amorphous phase, it is preferable that nanoscale Cu microcrystals are present in the amorphous phase. The nanoscale Cu microcrystals have a diameter of 50 nm or less. Further, the diameter is preferably 30 nm or less, and more preferably 20 nm or less. Further, the diameter is preferably 1 nm or more, more preferably 5 nm or more.
Further, it is preferable that the microcrystals of Cu are dispersed in the amorphous phase in the range of 1 × 10 ^-4 pieces / nm ² or more and 6 × 10 ^-4 pieces / nm ² or less.
The presence of these Cu microcrystals is useful for heat treatment to generate bcc—Fe microcrystals and is useful for obtaining Fe-based nanocrystal alloy powder with good magnetic properties.
Further, in the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder of the present disclosure, it is preferable that the portion other than the microcrystals of Cu is an amorphous phase.
That is, the Fe-based amorphous alloy in which fine crystals of Cu having a diameter of 50 nm or less are dispersed in the amorphous phase is the Fe group constituting the Fe-based amorphous alloy powder for the Fe-based nanocrystalline alloy powder of the present disclosure. Suitable as an amorphous alloy.

In the Fe-based nanocrystal alloy powder, as a method for refining the crystal grains of the nanocrystals contained in the alloy after heat treatment, finer bcc-Fe fine crystals are contained in the amorphous phase obtained by quenching and solidifying the molten alloy. There is a method of precipitating. However, in the case of an alloy strip that can obtain a uniform thickness, uniform heat treatment is easy, but in the case of alloy powder, it is difficult to control the progress of crystallization due to the variation in powder volume (powder particle size). Especially for large-diameter powders whose cooling rate tends to be slow, nanocrystals become coarse due to the progress of excessive crystallization, and phases that significantly deteriorate magnetic properties such as precipitation of Fe-B compounds precipitate. Was not easy.

However, in the case of the Fe-based amorphous alloy powder made of the Fe-based amorphous alloy in which nanoscale Cu microcrystals are present according to the present disclosure, the Cu microcrystals present before the heat treatment are fine bcc-Fe in the heat treatment process. It has the role of a crystal nucleation site and has the effect of increasing the generation probability of bcc-Fe fine crystals. On the other hand, when the generation probability of bcc-Fe fine crystals increases, the number density of bcc-Fe fine crystals increases, and as a result, the average crystal grain size of the fine crystals decreases. When the average crystal grain size of the bcc-Fe fine crystals decreases, the magnetic permeability increases due to the effect of random magnetic anisotropy, and it becomes easy to realize low loss.

In addition, since the Cu microcrystals existing before the heat treatment in the heat treatment process serve as a nucleation site for the bcc-Fe fine crystals, the heat generated during the precipitation of the bcc-Fe fine crystals that gradually precipitates at 300 ° C. or higher gradually increases. It is possible to suppress a rapid temperature rise of the entire powder to be heat-treated, and it is possible to prevent coarsening of bcc-Fe fine crystals.

<Heat treatment>
In the present embodiment, the Fe-based amorphous alloy powder is heat-treated to produce the Fe-based nanocrystalline alloy powder.
The furnace used for the heat treatment can be a continuous furnace or a fixed furnace as long as the desired temperature can be obtained. When a continuous furnace is used, a method may be used in which powder is placed in a container (for example, ceramics) that does not react with the Fe-based amorphous alloy, and the powder is transported and carried out into a furnace whose temperature is continuously set by a continuous transfer device. Further, as shown in Japanese Patent Application Laid-Open No. 2018-204072, the powder may be continuously put into the heat treatment furnace. In a fixed furnace, the powder in a container that does not react with the Fe-based amorphous alloy can be heated by continuously raising the temperature by a temperature control program.

In either case, in order to suppress the oxidation of the powder, it is desirable to have an inert atmosphere in which an inert gas such as argon or nitrogen is enclosed or inflowed. In this case, in addition to the method of creating an inert atmosphere in the entire furnace, a method of filling the powder container with the inert gas and enclosing or inflowing the gas may be used.

In the heat treatment of the present embodiment, the precipitation and growth of bcc-Fe fine crystals generated in the amorphous phase at the time of temperature rise, and the average temperature rise rate TA from 300 ° C. to 400 ° C., which is the temperature range in which Cu precipitates, are 2 ° C. The temperature is from / min to 10 ° C / min.

When the average temperature rise rate TA is slower than 2 ° C./min, the number density of bcc-Fe fine crystals precipitated in the amorphous phase is insufficient, resulting in coarse crystals and deteriorating magnetic properties. Further, although microcrystals of Cu are also precipitated, the temperature rise is gradual, so that the size of each microcrystal of Cu becomes coarse. For this reason, it is not possible to obtain the state of Cu microcrystals that are finely dispersed and exist as the core of bcc-Fe microcrystals, and as a result, it causes the nanocrystal particles to become coarse. Therefore, the average temperature rise rate TA is set to 2 ° C./min or more. It is preferably 3 ° C./min or higher.

When the average temperature rise rate TA exceeds 10 ° C./min, the temperature rises sharply due to heat generated when bcc-Fe fine crystals are precipitated in the amorphous phase. As a result, the temperature of the powder rises sharply, resulting in the powder temperature greatly exceeding 400 ° C., or causing variations in the precipitation of bcc-Fe fine crystals among powders having different particle sizes. Therefore, the average temperature rise rate TA is set to 10 ° C./min or less. Further, it is preferably 9.8 ° C./min or less.

The maximum temperature of the heat treatment is measured by measuring the Fe-based amorphous alloy with a differential scanning calorimeter (DSC) (heating rate 20 ° C./min), and the first (first, low temperature side) exothermic peak (bcc-Fe fine crystal precipitation). It is preferable that the temperature is equal to or higher than the temperature at which the exothermic peak) appears and is lower than the temperature at which the second (high temperature side) exothermic peak (exothermic peak due to coarse crystal precipitation) appears. At this time, when heat-treating a large amount of alloy powder in one batch, it is effective to set the temperature of about ± 30 ° C. of the first heat generation peak as the maximum temperature in consideration of the rate of temperature rise and heat generation.

The average temperature rise rate TB from 400 ° C. to the maximum temperature is 1.5 ° C./min to 8 ° C./min.
If the average temperature rise rate TB is slower than 1.5 ° C./min, the time to reach the maximum temperature becomes long, which causes the nanocrystal particles to become coarse. When the average temperature rise rate TB exceeds 8 ° C./min, the temperature rises sharply due to heat generated when bcc-Fe fine crystals are precipitated in the amorphous phase. As a result, the desired maximum temperature is exceeded, and a phase that significantly deteriorates magnetic properties such as coarsening of nanocrystals and precipitation of Fe—B-based compounds is precipitated. It is preferably 2 ° C./min or higher, and more preferably 3 ° C./min or higher. Further, it is preferably 7 ° C./min or less, and more preferably 6 ° C./min or less. Further, when the maximum temperature is reached, the temperature rise rate is preferably slow so that the temperature of the powder becomes uniform, and the average temperature rise rate TB is 30% to 70% of the average temperature rise rate TA. It is preferable, more preferably 40% to 60%.

Therefore, in the heat treatment of the present disclosure, when the average temperature rise rate from 300 ° C. to 400 ° C. at the time of temperature rise of the Fe-based amorphous alloy powder is TA and the average temperature rise rate from 400 ° C. to the maximum temperature is TB. TA is 2 ° C./min to 10 ° C./min, TB is 1.5 ° C./min to 8 ° C./min, and TA> TB.

When the above heat treatment is applied, it may be a step of keeping at the maximum temperature. At this time, the holding time at the maximum temperature may be sufficiently shorter than the temperature rising time. For example, it may be 5 to 15 minutes. Cooling of the alloy powder after reaching the maximum temperature can be carried out gradually in the furnace, but it may be carried out quickly in order to shorten the time to the next step. At this time, the entire container can be taken out of the furnace and exposed to the inert atmosphere outside the furnace for cooling.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Each element source such as pure iron, ferroboron, and ferrosilicon was blended so as to have the alloy composition shown in Table 1, and heated in an induction heating furnace to obtain a molten alloy. The molten alloy was atomized and rapidly cooled and solidified using the quenching solidification device (jet atomizing device) described in International Publication No. 2019/49965 to obtain an Fe-based amorphous alloy powder. The estimated temperature of the frame jet was 1300 to 1600 ° C., and the swirling flow velocity was about 160 m / sec.

In order to confirm the particle size of the obtained Fe-based amorphous alloy powder and determine the maximum temperature during heat treatment, particle size distribution measurement and DSC measurement were performed. For the particle size distribution, d10 = 10.0 μm, d50 = 24.4 μm, and d90 = 49.8 μm were collected using a particle size distribution measuring device (MT3000) manufactured by Microtrac Bell. The DSC measurement was performed using a Hitachi High-Tech (EXTRA6000) device with a measured powder amount of 30 to 40 mg, a temperature range of 200 to 750 ° C., and a heating rate of 20 ° C./min. The maximum temperature at the time of heat treatment was determined from the first peak 408 ° C. and the second peak 534 ° C. of the obtained profile.

A container (made of stainless steel / aluminum) that does not react with the Fe-based amorphous alloy was prepared, the Fe-based amorphous alloy powder was placed in the container, and a thermocouple was inserted into the center of the charged powder to measure the temperature of the powder. The container was preheated to a temperature higher than the target heating temperature in advance, and gas due to heating from deposits such as moisture on the surface was released in advance.
A container containing Fe-based amorphous alloy powder was installed so as to be located in the tropics in the heat treatment furnace, and the inert gas was allowed to flow in. The inflow of the inert gas was adjusted so that the oxygen concentration was 0.1% or less.

A temperature control program was set in the temperature control device that controls the heating of the furnace, and heat treatment was performed. Heating is performed continuously, but when the target temperature is approached, the heating rate is automatically reduced by the temperature control program. Therefore, an alloy powder-filled thermocouple was inserted into the powder container in advance, the temperature was measured, and a program was applied so that the temperature rise rate reached a predetermined level. Table 2 shows the heat treatment temperature conditions of Examples and Comparative Examples.

The Fe-based nanocrystalline alloy powders of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared under the heat treatment conditions shown in Table 2. The following evaluations were performed as evaluations of the powders of Examples 1 and 2 and Comparative Examples 1 and 2. The evaluation results are shown in Table 3.
<Saturation magnetic flux density>
The saturation magnetic flux density (Ms) of each of the powders of Examples 1 and 2 and Comparative Examples 1 and 2 was measured using a vibration sample magnetometer (VSM) device (BHV-35). 0.25 to 0.30 g of each powder was weighed and packed in resin capsules to prepare a sample. The measured magnetic field was measured in the range of 10,000 to 10,000 Oe.

<Core loss>
5 wt% of each powder of Examples 1 and 2 and Comparative Examples 1 and 2 and a silicone resin were added and molded at a molding pressure of 1 t / cm ² , and a ring core having an outer diameter of 13.5 mm, an inner diameter of 7.50 mm and a thickness of 2.5 mm was formed. Made. Using a BH analyzer (SY-8218), a sample in which a primary-wound copper wire having a diameter of 0.25 mm and a secondary-wound copper wire are wound 18 times each on the prepared ring core (magnetic core) is used, and the measured magnetic flux density is Bm = 20. The core loss P was obtained by measurement under the condition of frequency f = 3000 kHz.

As shown in Table 3, in Examples 1 and 2, the saturation magnetic flux density (Ms) is equivalent to that of the comparative example, and shows a high value of 160 emu / g or more. Further, in Examples 1 and 2, the core loss P is significantly reduced as compared with the comparative example. As described above, according to this example, Fe-based nanocrystalline alloy powder having good magnetic properties was obtained.

The cross section (inside) of the Fe-based nanocrystal alloy powders of Examples 1 and 2 and Comparative Examples 1 and 2 was observed with a transmission electron microscope to obtain a transmission electron microscope observation image (TEM image). FIG. 1 shows a TEM image of Example 1. In the Fe-based nanocrystal alloy powder of Example 1, bcc-Fe fine crystals are developed over the entire area. The diameter of the bcc-Fe fine crystal is about 30 nm, and the structure has the characteristics of a structure having good magnetic properties. In addition, Example 2 had the same organization.

In the Fe-based nanocrystalline alloy powders of Examples 1 and 2, the cross section (inside) of the Fe-based amorphous alloy powder before heat treatment was observed with a transmission electron microscope to obtain a transmission electron microscope observation image (TEM image). .. This Fe-based amorphous alloy powder is a powder obtained by atomization, and corresponds to the structure after quenching and solidification by atomization. That is, the TEM image of the Fe-based amorphous alloy powder is also a TEM image of the Fe-based amorphous alloy.
FIG. 2 shows a TEM image of the Fe-based amorphous alloy of this example. Further, FIG. 3 shows a schematic diagram obtained by processing the TEM image of FIG. 2.

As shown in FIGS. 2 and 3, in the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder of this example, microcrystals of Cu are dispersed and exist. The round shape in this figure is a microcrystal of Cu. It was confirmed by SEM energy dispersive X-ray analysis (SEM-EDX) analysis that this was Cu.
The diameter of the Cu microcrystals is about 10 nm, and when calculated from the TEM image, they are dispersed at a density of about 3 × 10 ^-4 pieces / nm ² . The density of the Cu microcrystals was set to the number per area (pieces / nm ² ) by confirming the number of Cu microcrystals that can be confirmed from the TEM image.
The conditions for obtaining a TEM image were an acceleration voltage of 200.0 kV and a magnification of 600,000 times, and JEM-2800 manufactured by JEOL Ltd. was used as the apparatus.
By heat-treating the Fe-based amorphous alloy powder made of the Fe-based amorphous alloy in which the Cu microcrystals are present by the heat treatment method of the present disclosure, an Fe-based nanocrystal alloy powder having good magnetic properties was obtained. That is, the Fe-based amorphous alloy in which fine crystals of Cu having a diameter of 50 nm or less are dispersed in the amorphous phase is the Fe-based amorphous alloy powder for producing the Fe-based nanocrystalline alloy powder having good magnetic properties. It is an alloy suitable for.

Claims (8)

A method for producing Fe-based nanocrystalline alloy powder by heat-treating Fe-based amorphous alloy powder to produce Fe-based nanocrystalline alloy powder.
When the average temperature rise rate from 300 ° C. to 400 ° C. when the temperature of the Fe-based amorphous alloy powder is raised is TA, and the average temperature rise rate from 400 ° C. to the maximum temperature is TB, TA is 2 ° C./min to A method for producing an Fe-based nanocrystalline alloy powder by heat-treating the Fe-based amorphous alloy powder under the conditions of 10 ° C./min, TB of 1.5 ° C./min to 8 ° C./min, and TA> TB. .. The first aspect of claim 1, wherein an Fe-based nanocrystal alloy powder having bcc-Fe (Si) fine crystals having a crystal grain size of 100 nm or less and having 50% by volume or more of the bcc-Fe (Si) fine crystals is produced. Method for producing Fe-based nanocrystalline alloy powder. The composition of the Fe-based nanocrystalline alloy powder is 3 to 8% for Si, 11 to 17% for B, 0.7 to 1.8% for Cu, and 0.05 to 0.7% for Sn in terms of atomic ratio. Cr is 0 to 1.5%, Nb is 0 to 1.0%, Mo is 0 to 1.0%, and the balance is represented by claim 1 or claim 2, wherein the balance is composed of Fe and impurities. The method for producing a Fe-based nanocrystalline alloy powder according to the above method. Any one of claims 1 to 3 which uses, as the Fe-based amorphous alloy powder, a powder made of an Fe-based amorphous alloy in which microcrystals of Cu having a diameter of 50 nm or less are dispersed in an amorphous phase. The method for producing an Fe-based nanocrystalline alloy powder according to the above item. The method for producing an Fe-based nanocrystal alloy powder according to claim 4, wherein the Cu microcrystals are present in the range of 1 × 10 ^-4 pieces / nm ² or more and 6 × 10 ^-4 pieces / nm ² or less. An Fe-based amorphous alloy in which fine crystals of Cu having a diameter of 50 nm or less are dispersed in an amorphous phase. The Fe-based amorphous alloy according to claim 6, wherein the Cu microcrystals are present in the range of 1 × 10 ^-4 pieces / nm ² or more and 6 × 10 ^-4 pieces / nm ² or less. The composition of the Fe-based amorphous alloy is 3 to 8% for Si, 11 to 17% for B, 0.7 to 1.8% for Cu, 0.05 to 0.7% for Sn, and Cr in terms of atomic ratio. The 6th or 7th claim, wherein 0 to 1.5%, Nb is 0 to 1.0%, Mo is 0 to 1.0%, and the balance is represented by the balance, which is composed of Fe and impurities. Fe-based amorphous alloy.

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