Manufacturing method of Fe-based nanocrystalline alloy powder and Fe-based amorphous alloy

Abstract

The present invention provides a method for manufacturing Fe-based nanocrystalline alloy powder and an Fe-based amorphous alloy. The present invention provides a method for manufacturing Fe-based nanocrystalline alloy powder, which can suppress the coarsening of grains and the precipitation of Fe2B crystals while generating bcc-Fe(Si) fine crystals, thereby obtaining good magnetic properties. A method for manufacturing Fe-based nanocrystalline alloy powder, wherein when the Fe-based amorphous alloy powder is heated, the average heating rate from 300°C to 400°C is set as TA, and the average heating rate from 400°C to the maximum temperature is set as TB, the Fe-based amorphous alloy powder is heat-treated under the conditions of TA of 2°C / min to 10°C / min, TB of 1.5°C / min to 8°C / min, and TA>TB.

Description

Technical Field

[0001] The invention relates to a method for producing Fe-based nanocrystalline alloy powder and a Fe-based amorphous alloy. Background Art

[0002] By subjecting the Fe-based amorphous alloy used to produce the Fe-based nanocrystalline alloy to heat treatment, fine crystals can be precipitated in the Fe-based amorphous alloy, thereby obtaining the Fe-based nanocrystalline alloy having fine crystals.

[0003] Usually, Fe-based amorphous alloy is obtained by rapidly solidifying alloy melt by a single-roll method or the like and in the form of a thin ribbon-shaped Fe-based amorphous alloy (Fe-based amorphous alloy ribbon). In the case of a magnetic core constituting an Fe-based nanocrystalline alloy, first, the Fe-based amorphous alloy ribbon is formed into a shape of a magnetic core or the like. Then, the Fe-based amorphous alloy ribbon formed into the shape of the magnetic core is subjected to a heat treatment in a magnetic field to separate fine crystal grains in the Fe-based amorphous alloy ribbon. Thus, a magnetic core (for example, with reference to patent document 1) consisting of an Fe-based nanocrystalline alloy ribbon with good magnetic properties can be obtained.

[0004] Because the Fe-based nanocrystalline alloy obtained by the single-roll method is in the form of a thin ribbon, the degree of freedom in the shape of the magnetic core that can be produced is limited. Specifically, the alloy ribbon is cut to a width corresponding to the desired magnetic core height and then wound to form the desired inner and outer diameters. As a result, the resulting shape is limited to a toroidal shape, a racetrack shape, and the like.

[0005] On the other hand, there was a variety of requirements for core shapes in the past. Therefore, if the Fe-based nanocrystalline alloy can be produced with powder, then by using forming methods such as pressing and extrusion, it is possible to more easily shape a core with various shapes. Therefore, research has been conducted to obtain powder in the Fe-based nanocrystalline alloy. (For example, with reference to patent documentation 2)

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 4-4393

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-95773 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] Under the situation that Fe-based amorphous alloy is heat-treated and fine crystal (hereinafter, also referred to as nanocrystal) is separated out and obtains Fe-based nanocrystalline alloy, in order to obtain the nanocrystalline structure of magnetic property excellence, need to implement rapid heating when thermal treatment.But, in the thermal treatment of Fe-based amorphous alloy powder, can be accompanied by heat release when the amorphous region in the powder separates out nanocrystal.When the thermal treatment of Fe-based amorphous alloy powder, the heat release of the nanocrystallization that overlaps based on the heating of rapid heating and follows the powder, thus, the excessive temperature rise of powder sometimes.Like this, if the excessive temperature rise of powder, then the temperature of powder can surpass suitable thermal treatment temperature, produces the coarsening of crystal grain, the separation of Fe2B crystal.As a result, can't obtain the Fe-based nanocrystalline alloy powder of good magnetic property.

[0012] The present disclosure aims to provide a method for producing Fe-based nanocrystalline alloy powder, which can generate fine crystals while suppressing the coarsening of crystal grains and the precipitation of Fe2B crystals, thereby obtaining good magnetic properties.

[0013] Another object is to provide an Fe-based amorphous alloy suitable for use in the method for producing the Fe-based nanocrystalline alloy powder disclosed herein.

[0014] Methods for solving problems

[0015] Specific methods for solving the above-mentioned problems include the following.

[0016] <1> A method for manufacturing Fe-based nanocrystalline alloy powder, comprising heat-treating Fe-based amorphous alloy powder to manufacture Fe-based nanocrystalline alloy powder, wherein the average heating rate from 300°C to 400°C when heating the Fe-based amorphous alloy powder is set as TA, and the average heating rate from 400°C to the maximum temperature is set as TB, and the Fe-based amorphous alloy powder is heat-treated under the conditions that TA is 2°C / min to 10°C / min, TB is 1.5°C / min to 8°C / min, and TA>TB.

[0017] <2> according to <1> The method for producing Fe-based nanocrystalline alloy powder comprises producing Fe-based nanocrystalline alloy powder having bcc-Fe(Si) fine crystals with a crystal particle size of 100 nm or less and the bcc-Fe(Si) fine crystals accounting for 50% or more by volume.

[0018] <3> according to <1> or <2> The method for producing the Fe-based nanocrystalline alloy powder, wherein the composition of the Fe-based nanocrystalline alloy powder is represented by 3-8% Si, 11-17% B, 0.7-1.8% Cu, 0.05-0.7% Sn, 0-1.5% Cr, 0-1.0% Nb, 0-1.0% Mo and the balance, which is composed of Fe and impurities.

[0019] <4> according to <1> ~ <3> The method for producing an Fe-based nanocrystalline alloy powder according to any one of the preceding claims, wherein the Fe-based amorphous alloy powder is composed of an Fe-based amorphous alloy in which Cu crystallites having a diameter of 50 nm or less are dispersed in an amorphous phase.

[0020] <5> according to <4> The method for producing Fe-based nanocrystalline alloy powder, wherein the Cu crystallite is 1×10 -4 pcs / nm 2 Above and 6×10 -4 pcs / nm 2 The following ranges exist.

[0021] <6> An Fe-based amorphous alloy in which Cu crystallites having a diameter of 50 nm or less are dispersed in an amorphous phase.

[0022] <7> according to <6> The Fe-based amorphous alloy, wherein the Cu crystallite is 1×10 -4 pcs / nm 2 Above and 6×10 -4 pcs / nm 2 The following ranges exist.

[0023] <8> according to <6> or <7> The Fe-based amorphous alloy, wherein the composition of the Fe-based amorphous alloy is represented by 3-8% Si, 11-17% B, 0.7-1.8% Cu, 0.05-0.7% Sn, 0-1.5% Cr, 0-1.0% Nb, 0-1.0% Mo and the balance in atomic ratio, and the balance is composed of Fe and impurities.

[0024] Effects of the Invention

[0025] According to the present disclosure, a method for producing Fe-based nanocrystalline alloy powder can be obtained, which can generate fine crystals while suppressing grain coarsening and precipitation of Fe2B crystals, thereby obtaining good magnetic properties. In addition, according to the present disclosure, an Fe-based amorphous alloy suitable for use in the method for producing Fe-based nanocrystalline alloy powder of the present disclosure can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1This is a transmission electron microscope image of the Fe-based nanocrystalline alloy powder of Example 1.

[0027] Figure 2 This is a transmission electron microscope image of the Fe-based amorphous alloy of this example.

[0028] Figure 3 yes Figure 2 Schematic diagram of . DETAILED DESCRIPTION

[0029] Hereinafter, the present disclosure will be described in detail using the embodiments of the present disclosure, but the present disclosure is not limited to these embodiments.

[0030] When describing the embodiments of the present disclosure with reference to the drawings, descriptions of components and reference numerals that overlap in the drawings may be omitted. Components denoted by the same reference numerals in the drawings refer to the same components.

[0031] In the present disclosure, the numerical range represented by “to” represents a range that includes the numerical values recorded before and after “to” as the lower limit and upper limit, respectively. In the numerical ranges recorded in stages in the present disclosure, the upper limit or lower limit recorded in a certain numerical range may also be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical ranges recorded in the present disclosure, the upper limit or lower limit recorded in a certain numerical range may also be replaced by the value shown in the examples.

[0032] In the present disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0033] In the present disclosure, the Fe-based amorphous alloy powder is a powder composed of an Fe-based amorphous alloy.

[0034] A method for producing an Fe-based nanocrystalline alloy powder according to one embodiment of the present disclosure is as follows: when heating the Fe-based amorphous alloy powder, the average heating rate from 300°C to 400°C is defined as TA, and the average heating rate from 400°C to the maximum temperature is defined as TB, and the Fe-based amorphous alloy powder is heat-treated under conditions where TA is 2°C / min to 10°C / min, TB is 1.5°C / min to 8°C / min, and TA>TB, thereby producing the Fe-based nanocrystalline alloy powder. The Fe-based amorphous alloy powder is an Fe-based amorphous alloy powder for use in Fe-based nanocrystalline alloy powder produced by heat treatment to form an Fe-based nanocrystalline alloy powder.

[0035] In one embodiment of the present disclosure, the Fe-based nanocrystalline 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 nanocrystalline alloy powder preferably have a crystal particle size of 100 nm or less. The average crystal particle size of the bcc-Fe fine crystals is preferably 10 to 50 nm. In addition, the Fe-based nanocrystalline alloy powder of the present disclosure preferably has bcc-Fe fine crystals of 50% by volume or more. It should be noted that, in the Fe-based nanocrystalline alloy powder, the portion other than the bcc-Fe fine crystals may also be an amorphous phase. Here, the volume fraction of bcc-Fe fine crystals can be calculated by observing the alloy structure of the Fe-based nanocrystalline alloy powder with a transmission electron microscope (TEM), summing up the area of the roughly spherical structure (bcc-Fe fine crystals), and calculating the ratio relative to the area of the observation field of view.

[0036] In one embodiment of the present disclosure, the composition of the Fe-based nanocrystalline alloy powder is preferably represented by 3-8% Si, 11-17% B, 0.7-1.8% Cu, 0.05-0.7% Sn, 0-1.5% Cr, 0-1.0% Nb, 0-1.0% Mo, and the balance, in terms of atomic ratio. Here, the balance is composed of Fe and impurities. It should be noted that Cr, Nb, and Mo can each be 0%.

[0037] By having the composition of the Fe-based nanocrystalline alloy powder be this composition, the Fe-based nanocrystalline alloy powder obtained by the heat treatment method of the present disclosure can stably have a nanocrystalline structure having excellent magnetic properties.

[0038] Furthermore, in the embodiment of the present disclosure, 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 also preferably have the same composition.

[0039] The emergence of the nanocrystalline structure according to the heat treatment method disclosed herein requires two important elements. The first is that in the temperature range of 300°C to 400°C when heating, a phase different from the amorphous phase with Cu and Sn as the main body, which becomes the core of the nanocrystal (hereinafter also referred to as "heterogeneous phase"), exists with a sufficient number density. This is closely related to the amount of Cu and the amount of Sn. The total content (atomic %) of Cu and Sn is preferably more than 1.2 atomic %, and more preferably more than 1.3 atomic %. Thus, a heterogeneous phase with sufficient number density can be obtained. In addition, when their total is less than 1.85 atomic %, the coarsening of the clusters can be suppressed and a high number density can be maintained. Furthermore, the total of Cu and Sn is preferably less than 1.8 atomic %.

[0040] The second is the range of excessive temperature rise in the temperature range above 400°C during heating. Here, excessive temperature rise refers to raising the powder temperature above the target heat treatment temperature. Crystallization of the amorphous phase generates heat due to collective crystallization, which causes excessive temperature rise in the temperature range above 400°C. According to the disclosed method, which aims to balance production efficiency and magnetic properties, even if excessive temperature rise occurs, the range of excessive temperature rise is limited to approximately 20-30°C, which can suppress grain coarsening and the precipitation of Fe2B crystals. At this time, if the thermal stability of the residual amorphous phase is high, excessive grain growth can be suppressed, and unevenness in excessive temperature rise can be tolerated, making it easier to obtain the target powder. B, Nb, Mo, and Si play a significant role in improving the thermal stability of the residual amorphous phase. Therefore, appropriate amounts of B, Si, Nb, and Mo are necessary. Therefore, B is preferably at least 11 atomic % and Si is at least 3 atomic %. Furthermore, B is more preferably at least 13 atomic % and Si is at least 4 atomic %. In addition, Nb and Mo are not essential elements, but it is preferable to contain at least one of Nb and Mo. When Nb or Mo is contained, the content is more preferably 0.2 atomic % or more.

[0041] Furthermore, the amount of Fe significantly affects the saturation magnetic flux density. A higher Fe content leads to a higher saturation magnetic flux density. Therefore, the Fe content is preferably 89% by weight or greater, more preferably 90% by weight or greater. Furthermore, expressed in atomic ratio, the Fe content is preferably 78% or greater, more preferably 80% or greater.

[0042] Hereinafter, a method for producing Fe-based nanocrystalline alloy powder according to one embodiment of the present disclosure will be described in order of steps.

[0043] In the present disclosure, when manufacturing Fe-based nanocrystalline alloy powder, Fe-based amorphous alloy powder for Fe-based nanocrystalline alloy powder is first manufactured. Then, the Fe-based amorphous alloy powder is heat-treated to manufacture Fe-based nanocrystalline alloy powder. This is achieved by the following method: when manufacturing Fe-based nanocrystalline alloy, Fe-based amorphous alloy is first manufactured, and the Fe-based amorphous alloy is heat-treated to manufacture Fe-based nanocrystalline alloy.

[0044] First, the Fe-based amorphous alloy powder used in this embodiment will be described.

[0045] The Fe-based amorphous alloy powder used in this embodiment is a powder composed of an Fe-based amorphous alloy and can be obtained by rapidly solidifying an alloy melt by atomization, etc. In this case, the alloy melt has an alloy composition for obtaining the target Fe-based nanocrystalline alloy powder.

[0046] <Alloy Molten Metal>

[0047] The alloy melt is prepared by mixing various element sources such as pure iron, ferroboron, and ferrosilicon to form a desired alloy composition, and heating and melting the alloy to the alloy melting point in an induction heating furnace, etc. In this way, an alloy melt having the alloy composition of the target Fe-based nanocrystalline alloy powder can be obtained.

[0048] <Atomization method>

[0049] As a method for producing Fe-based amorphous alloy powder, there is an atomization method in which a medium such as gas or water is collided with a molten alloy at high speed to pulverize the molten alloy. The Fe-based amorphous alloy powder of this embodiment can be produced using the atomization method.

[0050] For example, an atomization method using the production apparatus (jet atomization apparatus) described in Japanese Patent Application Laid-Open No. 2017-155341 can be used.

[0051] Various methods are known for the atomization method, and the production conditions can be appropriately selected from known production techniques to obtain an Fe-based amorphous alloy.

[0052] In addition, in this embodiment, for example, the metal powder production apparatus described in International Publication No. 2019 / 49865 is preferably used to produce Fe-based amorphous alloy powder.

[0053] The Fe-based amorphous alloy powder of this embodiment is obtained by rapidly solidifying an alloy melt. Therefore, after the alloy melt is crushed, it is necessary to rapidly solidify and cool the crushed fine powder (alloy melt). Therefore, it is preferred to use water or a solvent with high cooling capacity, spray the water or solvent with high cooling capacity onto the crushed fine powder (alloy melt), or flush the crushed fine powder (alloy melt) into water or a solvent with high cooling capacity.

[0054] In the metal powder production apparatus described in International Publication No. 2019 / 49865, a swirling water flow is used, which is suitable for rapidly cooling and solidifying the alloy melt.

[0055] <Fe-based amorphous alloy and Fe-based amorphous alloy powder>

[0056] The Fe-based amorphous alloy powder in the present disclosure is an alloy powder having an amorphous phase. The Fe-based amorphous alloy constituting the alloy powder having the amorphous phase preferably contains nanoscale Cu crystallites within the amorphous phase. It should be noted that nanoscale Cu crystallites have a diameter of 50 nm or less. Furthermore, a diameter of 30 nm or less is preferred, and a diameter of 20 nm or less is more preferred. Furthermore, a diameter of 1 nm or greater is preferred, and a diameter of 5 nm or greater is more preferred.

[0057] In addition, the Cu crystallite is preferably 1×10 -4 pcs / nm 2 Above and 6×10 -4pcs / nm 2 The following ranges exist dispersedly in the amorphous phase.

[0058] The presence of Cu microcrystals facilitates heat treatment to form bcc-Fe fine crystals, thereby contributing to obtaining Fe-based nanocrystalline alloy powder having excellent magnetic properties.

[0059] Furthermore, it is preferable that the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder of the present disclosure has a portion other than Cu crystallites in an amorphous phase.

[0060] That is, an Fe-based amorphous alloy in which Cu crystallites having a diameter of 50 nm or less are dispersed in an amorphous phase is suitable as the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder for the Fe-based nanocrystalline alloy powder disclosed herein.

[0061] In Fe-based nanocrystalline alloy powder, as the method for the grain refinement of nanocrystal contained in the alloy after the heat treatment, there is a method for separating out finer bcc-Fe fine crystals in the amorphous phase obtained by quenching and solidifying the molten alloy. However, when an alloy ribbon of uniform thickness can be obtained, uniform heat treatment is easily carried out, but in the case of alloy powder, due to the deviation of powder volume (particle size of powder), the degree of progress of crystallization is difficult to control. Particularly in the large-diameter powder that cooling rate is easy to slack off, due to excessive crystallization, nanocrystal coarsening is made, or Fe-B system compounds etc. are separated out, which makes the phase that magnetic properties are greatly deteriorated, and is therefore not easy to apply.

[0062] However, in the case of the Fe-based amorphous alloy powder disclosed herein, which is composed of an Fe-based amorphous alloy containing nanoscale Cu microcrystals, the Cu microcrystals present before heat treatment act as nucleation sites for bcc-Fe microcrystals, increasing the probability of bcc-Fe microcrystal formation. On the other hand, an increase in the probability of bcc-Fe microcrystal formation increases the number density of bcc-Fe microcrystals, resulting in a decrease in the average crystal size of the microcrystals. A decrease in the average crystal size of bcc-Fe microcrystals increases the magnetic permeability due to the effects of random magnetic anisotropy, making it easier to achieve low losses.

[0063] Furthermore, during the heat treatment process, the Cu microcrystals existing before the heat treatment serve as nucleation sites for bcc-Fe microcrystals. Therefore, the heat released during the precipitation of the bcc-Fe microcrystals that gradually precipitate above 300°C is gradually generated, which can suppress the rapid temperature rise of the entire powder undergoing the heat treatment and prevent the coarsening of the bcc-Fe microcrystals.

[0064] Heat treatment

[0065] In this embodiment, Fe-based amorphous alloy powder is heat-treated to produce Fe-based nanocrystalline alloy powder.

[0066] The furnace used in the heat treatment can be a continuous furnace or a fixed furnace as long as the desired temperature can be obtained. In the case of using a continuous furnace, it is also possible to place the powder in a container (such as ceramic) that does not react with the Fe-based amorphous alloy, and use a continuous conveying device to continuously transport and move it out to a furnace with a set temperature. In addition, as shown in Japanese Patent Publication No. 2018-204072, the powder can also be continuously put into a heat treatment furnace. If it is a fixed furnace, the temperature of the powder placed in the container that does not react with the Fe-based amorphous alloy can be continuously increased and heated by a temperature control program.

[0067] In either case, to suppress oxidation of the powder, an inert atmosphere, in which an inert gas such as argon or nitrogen is enclosed or flowed, is preferably used. In this case, in addition to creating an inert atmosphere throughout the furnace, other methods such as filling the powder container with the inert gas and then enclosing or flowing the inert gas can also be employed.

[0068] In the heat treatment of this embodiment, the average heating rate TA in the temperature range of 300°C to 400°C for precipitation and growth of bcc-Fe fine crystals generated in the amorphous phase and Cu precipitation during heating is set to 2°C / min to 10°C / min.

[0069] When the average heating 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. Furthermore, Cu crystals also precipitate, but the temperature rise is slow, causing the size of each Cu crystal to coarsen. Consequently, it is impossible to obtain a state where finely dispersed Cu crystals, such as the nuclei of bcc-Fe fine crystals, exist, resulting in the coarsening of nanocrystals. Therefore, the average heating rate TA is set to 2°C / min or higher. Preferably, it is set to 3°C / min or higher.

[0070] If the average heating rate TA exceeds 10°C / min, the temperature rises rapidly due to the heat generated during the precipitation of bcc-Fe fine crystals in the amorphous phase. This results in a rapid rise in the powder temperature, significantly exceeding 400°C, or causing variations in the precipitation of bcc-Fe fine crystals in individual powders with different particle sizes. Therefore, the average heating rate TA is set to 10°C / min or less. Preferably, it is 9.8°C / min or less.

[0071] The maximum heat treatment temperature for the Fe-based amorphous alloy is preferably determined by differential scanning calorimetry (DSC) (heating rate 20°C / minute) to be at or above the temperature at which the first (initial, low-temperature side) exothermic peak (the exothermic peak caused by the precipitation of bcc-Fe fine crystals) appears, and below the temperature at which the second (high-temperature side) exothermic peak (the exothermic peak caused by the precipitation of coarse crystals appears). When heat treating a large amount of alloy powder in a single batch, it is effective to set the maximum temperature to approximately ±30°C of the first exothermic peak, taking into account the heating rate and heat release.

[0072] The average heating rate TB from 400° C. to the maximum temperature is 1.5° C. / min to 8° C. / min.

[0073] When the average heating rate TB is slower than 1.5°C / min, the time to reach the maximum temperature becomes longer, which causes the nanocrystals to coarsen. When the average heating rate TB exceeds 8°C / min, the temperature rises rapidly due to the heat release when bcc-Fe fine crystals are precipitated in the amorphous phase. As a result, the desired maximum temperature is exceeded, the nanocrystals coarsen, or phases such as Fe-B compounds are precipitated that greatly deteriorate the magnetic properties. It is preferably 2°C / min or more, and more preferably 3°C / min or more. In addition, it is preferably 7°C / min or less, and more preferably 6°C / min or less. In addition, when reaching the maximum temperature, the heating rate is preferably slow so that the temperature of the powder becomes uniform, and the average heating rate TB is preferably 30% to 70% of the average heating rate TA, and more preferably 40% to 60%.

[0074] Therefore, in the heat treatment disclosed herein, when the average heating rate from 300°C to 400°C when heating the Fe-based amorphous alloy powder is set to TA, and the average heating rate from 400°C to the maximum temperature is set to TB, TA is set to 2°C / min to 10°C / min, TB is set to 1.5°C / min to 8°C / min, and TA>TB.

[0075] When performing the above heat treatment, a process may also be performed in which the alloy powder is held at the maximum temperature. In this case, the holding time at the maximum temperature is preferably sufficiently short relative to the heating time. For example, it may be 5 to 15 minutes. After reaching the maximum temperature, the alloy powder may be cooled slowly in the furnace, but it may also be cooled quickly to shorten the time until the next step. In this case, the alloy powder may be removed from the furnace along with the container and exposed to an inert atmosphere outside the furnace for cooling.

[0076] Example

[0077] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0078] Pure iron, ferroboron, ferrosilicon, and other elemental sources were blended to form the alloy composition shown in Table 1 and heated in an induction heating furnace to obtain a molten alloy melt. The alloy melt was atomized and rapidly solidified using a rapid cooling and solidification device (jet atomization device) described in International Publication No. 2019 / 49865 to obtain Fe-based amorphous alloy powder. The estimated temperature of the frame jet was 1300-1600°C, and the swirling flow velocity was approximately 160 m / s.

[0079] [Table 1]

[0080] [at%]

[0081] Fe Cr Si B Cu Nb Mo C Sn 79.1 0.5 6 12 1.5 0 0.7 0 0.2

[0082] 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. The particle size distribution was measured using a particle size distribution measuring device (MT3000) manufactured by Microtrac.BEL, and d10 = 10.0 μm, d50 = 24.4 μm, and d90 = 49.8 μm were collected. In addition, the DSC measurement was performed using an EXTRA6000 device manufactured by Hitachi High-Tech Corporation, under the conditions of a powder amount of 30 to 40 mg, a temperature range of 200 to 750 ° C, and a heating rate of 20 ° C / minute. The maximum temperature during heat treatment was determined by the first peak of 408 ° C and the second peak of 534 ° C of the obtained curve.

[0083] Prepare a container (stainless steel or aluminum) that does not react with the Fe-based amorphous alloy. Place Fe-based amorphous alloy powder in this container. Insert a thermocouple into the center of the added powder to measure the powder temperature. The container is preheated to a temperature higher than the target heating temperature to allow the heated gas to be released from surface deposits such as moisture.

[0084] A container containing Fe-based amorphous alloy powder is placed in a soaking zone within a heat treatment furnace, and an inert gas is flowed in. The inflow amount of the inert gas is adjusted to an oxygen concentration of 0.1% or less.

[0085] Heat treatment was performed by setting a temperature control program in the temperature control device that controlled the heating of the furnace. Heating was performed continuously, but as the target temperature approached, the temperature control program automatically reduced the heating rate. Therefore, alloy powder was placed in a powder container in advance, and a thermocouple was inserted to measure the temperature. The program was then implemented to achieve the predetermined heating rate. The heat treatment temperature conditions for the Examples and Comparative Examples are shown in Table 2.

[0086] [Table 2]

[0087] TA (℃ / min) TB (℃ / min) Maximum temperature (℃) Comparative Example 1 0.5 0.24 411 Comparative Example 2 0.46 0.34 432 Example 1 8.5 4.5 421 Example 2 9.7 4.34 416

[0088] Fe-based nanocrystalline alloy powders of Examples 1 and 2 and Comparative Examples 1 and 2 were produced under the heat treatment conditions described in Table 2. The following evaluations were performed on the powders of Examples 1 and 2 and Comparative Examples 1 and 2. The evaluation results are shown in Table 3.

[0089] <Saturation magnetic flux density>

[0090] The saturation magnetic flux density (Ms) of each powder from Examples 1 and 2 and Comparative Examples 1 and 2 was measured using a vibrating sample magnetometer (VSM) (BHV-35). 0.25 to 0.30 g of each powder was weighed and placed in a resin capsule as a sample. Measurements were performed within a magnetic field range of -10,000 to 10,000 Oe.

[0091] Core loss

[0092] 5 wt% of each powder of Examples 1, 2, Comparative Examples 1, 2 and silicone resin were added to form a 1 t / cm 2 The toroidal core was formed to have an outer diameter of 13.5 mm, an inner diameter of 7.50 mm, and a thickness of 2.5 mm. Using a BH analyzer (SY-8218), under the conditions of magnetic flux density Bm = 20 and frequency f = 3000 kHz, a sample was wound 18 times around the toroidal core (magnetic core) to obtain the core loss P. The sample was wound 18 times with a primary winding copper wire and a secondary winding copper wire each having a diameter of 0.25 mm.

[0093] [Table 3]

[0094] Ms(emu / g) <![CDATA[Core loss P (kW / m 3 )]]> Comparative Example 1 161.2 10600 Comparative Example 2 161.6 11460 Example 1 162.2 6291 Example 2 162 7339

[0095] As shown in Table 3, the saturation magnetic flux density (Ms) of Examples 1 and 2 is equivalent to that of the comparative example, showing a high value of more than 160 emu / g. In addition, the core loss P of Examples 1 and 2 is significantly reduced relative to that of the comparative example. As described above, according to this embodiment, an Fe-based nanocrystalline alloy powder with excellent magnetic properties is obtained.

[0096] The cross sections (interior) of the Fe-based nanocrystalline alloy powders of Examples 1 and 2 and Comparative Examples 1 and 2 were observed using a transmission electron microscope to obtain transmission electron microscope images (TEM images). Figure 1 TEM images of Example 1 are shown in Figure 2. In the Fe-based nanocrystalline alloy powder of Example 1, bcc-Fe fine crystals are well-developed throughout the entire region. The diameter of the bcc-Fe fine crystals is approximately 30 nm, demonstrating a structure characterized by excellent magnetic properties. Note that Example 2 also exhibits a similar structure.

[0097] In the Fe-based nanocrystalline alloy powders of Examples 1 and 2, the cross-section (internal portion) of the Fe-based amorphous alloy powder before heat treatment was observed using a transmission electron microscope to obtain a transmission electron microscope image (TEM image). The Fe-based amorphous alloy powder is a powder obtained by atomization, and is equivalent to the structure after rapid cooling and solidification caused 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.

[0098] Figure 2 TEM images of the Fe-based amorphous alloy of this embodiment are shown. Figure 3 Shown in Figure 2 Schematic diagram of the TEM image obtained by processing.

[0099] like Figure 2 、 3 As shown, the Fe-based amorphous alloy constituting the Fe-based amorphous alloy powder of this example contains dispersed Cu crystallites. The circular shapes in the figure are Cu crystallites. SEM energy dispersive X-ray analysis (SEM-EDX) confirmed that these are Cu.

[0100] The diameter of the Cu crystallite is about 10 nm, and the result is calculated based on the TEM image, which is 3×10 -4 pcs / nm 2 The density of Cu crystallites was determined by measuring the number of Cu crystallites that could be confirmed by TEM images, and the number of crystallites per unit area (crystals / nm) was used. 2 ).

[0101] The TEM images were obtained under conditions of an accelerating voltage of 200.0 kV and a magnification of 600,000 times, using a JEM-2800 manufactured by JEOL Ltd. as the apparatus.

[0102] By heat-treating Fe-based amorphous alloy powder composed of an Fe-based amorphous alloy containing Cu microcrystals using the heat treatment method disclosed herein, Fe-based nanocrystalline alloy powder having excellent magnetic properties is obtained. Specifically, an Fe-based amorphous alloy in which Cu microcrystals having a diameter of 50 nm or less are dispersed in an amorphous phase is an alloy suitable for producing Fe-based amorphous alloy powder having excellent magnetic properties.

Claims

1. A method for producing Fe-based nanocrystalline alloy powder, comprising: heat-treating Fe-based amorphous alloy powder to produce Fe-based nanocrystalline alloy powder, wherein: When the average heating rate from 300°C to 400°C when the Fe-based amorphous alloy powder is heated is set as TA, and the average heating rate from 400°C to the maximum temperature is set as TB, the Fe-based amorphous alloy powder is heat treated under the conditions of TA of 2°C / min to 10°C / min, TB of 1.5°C / min to 8°C / min and TA>TB.

2. The method for producing Fe-based nanocrystalline alloy powder according to claim 1, wherein: An Fe-based nanocrystalline alloy powder is produced, which has bcc-Fe(Si) fine crystals with a crystal grain size of 100 nm or less and the bcc-Fe(Si) fine crystals account for 50% by volume or more.

3. The method for producing Fe-based nanocrystalline alloy powder according to claim 1 or 2, wherein: The composition of the Fe-based nanocrystalline alloy powder is represented by 3-8% Si, 11-17% B, 0.7-1.8% Cu, 0.05-0.7% Sn, 0-1.5% Cr, 0-1.0% Nb, 0-1.0% Mo and the balance, which is composed of Fe and impurities.

4. The method for producing Fe-based nanocrystalline alloy powder according to claim 1 or 2, wherein: As the Fe-based amorphous alloy powder, a powder composed of an Fe-based amorphous alloy in which Cu crystallites having a diameter of 50 nm or less are dispersed in an amorphous phase is used.

5. The method for producing Fe-based nanocrystalline alloy powder according to claim 3, wherein: As the Fe-based amorphous alloy powder, a powder composed of an Fe-based amorphous alloy in which Cu crystallites having a diameter of 50 nm or less are dispersed in an amorphous phase is used.

6. The method for producing Fe-based nanocrystalline alloy powder according to claim 4, wherein: The Cu crystallite is 1×10 -4 pcs / nm 2 Above and 6×10 -4 pcs / nm 2 The following ranges exist.

7. The method for producing Fe-based nanocrystalline alloy powder according to claim 5, wherein: The Cu crystallite is 1×10 -4 pcs / nm 2 Above and 6×10 -4 pcs / nm 2 The following ranges exist.

8. An Fe-based amorphous alloy, wherein: Cu crystallites with a diameter of 50 nm or less are dispersed in the amorphous phase. -4 pcs / nm 2 Above and 6×10 -4 pcs / nm 2 The following ranges exist.

9. The Fe-based amorphous alloy according to claim 8, wherein: The composition of the Fe-based amorphous alloy is represented by 3-8% Si, 11-17% B, 0.7-1.8% Cu, 0.05-0.7% Sn, 0-1.5% Cr, 0-1.0% Nb, 0-1.0% Mo and the balance, which is composed of Fe and impurities.

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