JP7421742B2 - Nanocrystalline soft magnetic material - Google Patents

Description

The present invention relates to a soft magnetic material in which crystal grains are dispersed in an amorphous matrix made of an Fe-based alloy, a method for producing the same, and an Fe-based alloy used therein, and in particular, nanocrystalline particles are dispersed in the amorphous matrix by heating. The present invention relates to a nanocrystalline soft magnetic material obtained by dispersing and crystallizing a nanocrystalline soft magnetic material, a method for producing the same, and an Fe-based alloy used therein.

As the frequency band used moves toward higher frequencies, soft magnetic materials used in electronic components such as in-vehicle reactors are required to have high saturation magnetic flux density, low magnetostriction, and low coercive force. However, since magnetic flux density and loss generally have a trade-off relationship with each other, it is not easy to achieve both. Here, it has been discovered that by making a crystalline soft magnetic material amorphous, it is possible to lower the coercive force and increase the saturation magnetic flux density.

For example, in Patent Document 1, in atomic %, B: 3.0 to 6.0%, Si: ≦8.0%, P: 4.0 to 8.0%, Cu: 0.3 to 1.0 %, C: 8.0 to 12.0%, Cr: 1.0 to 4.0%, and the balance is Fe. has been done. It is said that such soft magnetic materials can have low coercive force and low core loss.

Furthermore, soft magnetic materials having a two-phase structure in which crystal grains are dispersed and crystallized in an amorphous matrix have also been proposed. Patent Document 1 also mentions a nanocrystalline soft magnetic material having a two-phase structure in which BCC-Fe crystal particles having nano-sized particles are crystallized in an amorphous matrix.

Patent Document 2 also discloses a nanocrystalline soft magnetic material having a two-phase structure in which BCC-Fe crystal particles having a particle size of 20 nm or less are crystallized in an amorphous matrix. Such a nanocrystalline soft magnetic material contains, in atomic percent, P: 6-10%, C: 6-8%, B: 2-6%, Cu: 0.4-1%, Si: 1-3%, Cr. : 2 atomic % or less, and the balance is Fe. The amorphous powder obtained by rapid solidification is heat treated to crystallize fine BCC-Fe crystal particles to obtain a two-phase structure. It is said that a magnetic body of a predetermined shape can be manufactured by compacting this material.

Japanese Patent Application Publication No. 2016-211017 JP2016-23340A

As mentioned above, in a nanocrystalline soft magnetic material in which crystal particles are dispersed in an amorphous matrix, the magnetocrystalline anisotropy is based on the RAM (random magnetic anisotropy) theory. It is directly proportional to the reciprocal of the particle size of the crystalline phase particles. Therefore, in order to lower the coercive force, it is preferable to make the particle diameter of the crystalline phase particles small and uniform. On the other hand, in order to obtain finer crystal phase particles by heat treatment, a method of high-speed heating is generally known, but it is difficult to control and has poor productivity.

The present invention has been made in view of the above circumstances, and its object is to provide a nanocrystalline soft magnetic material in which crystal particles are dispersed in an amorphous matrix made of an Fe-based alloy. An object of the present invention is to provide a nanocrystalline soft magnetic material having excellent soft magnetic properties and high productivity, a method for producing the same, and an Fe-based alloy used therein.

The nanocrystalline soft magnetic material according to the present invention is a nanocrystalline soft magnetic material in which crystal grains with an average particle size of 15 nm or less are dispersed in an amorphous parent phase made of an Fe-based alloy, and has Si: 0.1 atomic %. ~5.0%, B: 5.0~12.0%, C: 0.1~5.0%, P: 2.0~6.0%, Cu: x% (1.0<x< 2.5), Cr:y% (1.0<y<3.0), however, x+y>2.6, the balance is Fe and unavoidable impurities, and the coercive force Hc is 15 [A /m], and the saturation magnetic flux density Bs is larger than 1.40 [T].

According to this invention, it has excellent soft magnetic properties and high productivity.

In the invention described above, the alloy composition is, in atomic %, Si: 0.1 to 3.0%, B: 10.0 to 12.0%, C: 0.1 to 3.0%, P: 3. .0 to 5.0%, Cu: x% (1.0<x<1.5), Cr:y% (1.0<y<2.0), however, x+y>2.6, balance Fe and unavoidable impurities. Further, the alloy composition may be characterized in that it contains Fe in an amount of 80.0 atomic % or more. According to this invention, excellent soft magnetic properties can be obtained relatively easily while maintaining high productivity.

The above invention may be characterized in that the average particle diameter of the crystal particles is 5 nm or less. According to this invention, even better soft magnetic properties can be obtained.

Further, the method for producing a nanocrystalline soft magnetic material according to the present invention is a method for producing a nanocrystalline soft magnetic material in which crystal particles having an average particle size of 15 nm or less are dispersed in an amorphous matrix composed of an Fe-based alloy, %, Si: 0.1 to 5.0%, B: 5.0 to 12.0%, C: 0.1 to 5.0%, P: 2.0 to 6.0%, Cu: x % (1.0<x<2.5), Cr:y% (1.0<y<3.0), however, x+y>2.6, the balance having an alloy composition consisting of Fe and inevitable impurities. For the amorphous single-phase alloy ribbon obtained by rapidly solidifying the alloy, the coercive force Hc is smaller than 15 [A/m] and the saturation magnetic flux density Bs is larger than 1.40 [T], The method is characterized in that the crystal particles are dispersed by heating at a rate of 200° C./min or less.

According to this invention, a nanocrystalline soft magnetic material having excellent soft magnetic properties can be obtained with high productivity.

In the above invention, the alloy composition is, in atomic %, Si: 0.1 to 3.0%, B: 10.0 to 12.0%, C: 0.1 to 3.0%, P: 3. .0 to 5.0%, Cu: x% (1.0<x<1.5), Cr:y% (1.0<y<2.0), however, x+y>2.6, balance Fe and unavoidable impurities. Further, the alloy composition may be characterized in that it contains Fe in an amount of 80.0 atomic % or more. According to this invention, a nanocrystalline soft magnetic material having excellent soft magnetic properties can be obtained relatively easily while maintaining high productivity.

The above invention may be characterized in that the average particle diameter of the crystal particles is 5 nm or less. According to this invention, a nanocrystalline soft magnetic material having even better soft magnetic properties can be obtained.

Furthermore, the Fe-based alloy for nanocrystalline soft magnetic material according to the present invention is an Fe-based alloy for nanocrystalline soft magnetic material as a master alloy used in the above-described method for producing the nanocrystalline soft magnetic material, and is Si: 0.1 to 5.0%, B: 5.0 to 12.0%, C: 0.1 to 5.0%, P: 2.0 to 6.0%, Cu: x% (1 .0 < x < 2.5), Cr: y% (1.0 < y < 3.0), provided that x + y > 2.6, the balance being Fe and inevitable impurities. do.

According to this invention, it is possible to obtain an alloy for producing a nanocrystalline soft magnetic material having excellent soft magnetic properties with high productivity.

In the invention described above, the alloy composition is, in atomic %, Si: 0.1 to 3.0%, B: 10.0 to 12.0%, C: 0.1 to 3.0%, P: 3. .0 to 5.0%, Cu: x% (1.0<x<1.5), Cr:y% (1.0<y<2.0), however, x+y>2.6, balance Fe and unavoidable impurities. Further, the alloy composition may be characterized in that it contains Fe in an amount of 80.0 atomic % or more. According to this invention, an alloy for manufacturing a nanocrystalline soft magnetic material having excellent soft magnetic properties can be obtained relatively easily while maintaining high productivity.

FIG. 2 is a flow diagram showing a method for manufacturing a nanocrystalline soft magnetic material in one embodiment according to the present invention. This is a list of the composition of alloys used in manufacturing tests and the properties of the obtained alloy ribbons. This is a list of heat treatment conditions and characteristics of soft magnetic materials obtained in manufacturing tests.

A method for manufacturing a nanocrystalline soft magnetic material as one embodiment of the present invention will be described with reference to FIG. 2 along with FIG.

As shown in FIG. 1, first, an amorphous single-phase alloy ribbon made of an Fe-based alloy is manufactured (S1).

Referring also to FIG. 2, the Fe-based alloy for obtaining such an alloy ribbon is an alloy having a chemical composition represented by Alloys 1, 5 to 7. In detail, in atomic %, Si: 0.1 to 5.0%, B: 5.0 to 12.0%, C: 0.1 to 5.0%, P: 2.0 to 6.0 %, Cu:x% (1.0<x<2.5), Cr:y% (1.0<y<3.0), and further, regarding the content of Cu and Cr, x+y>2 It is an Fe-based alloy with a rating of .6. In particular, the resulting nanocrystalline soft magnetic material contains a large amount of Cu and Cr, which are elements that promote nanocrystallization. Note that the amorphous single-phase alloy ribbon referred to herein may be substantially amorphous single-phase, and preferably has a crystallinity of 10% or less.

An alloy ribbon is manufactured by using a Fe-based alloy having such a composition as a master alloy, for example, by a single roll method. That is, a mother alloy is melted and the molten metal is extracted and solidified on the surface of a copper cooling roll rotating at high speed to obtain an amorphous single-phase ribbon-like rapidly solidified thin body, which is used as an alloy ribbon. Here, it is preferable to rapidly cool the molten metal by setting the circumferential speed of the cooling roll within a range of 20 to 30 m/s, thereby making the alloy ribbon a single amorphous phase.

Next, the obtained alloy ribbon is heat treated (S2).

As mentioned above, the alloy ribbon obtained by the single roll method has a single amorphous phase, and by heat treatment that controls the heating rate, holding temperature, and holding time, α-Fe crystal particles are formed into a predetermined shape in the amorphous matrix. It can be dispersed and crystallized. In particular, by controlling the average particle diameter of crystal grains to be dispersed and crystallized to 15 nm or less, the coercive force Hc of the obtained nanocrystalline soft magnetic material can be made smaller than 15 [A/m], and saturation is achieved. The magnetic flux density Bs can be made larger than 1.40 [T]. This heat treatment relaxes the local structure of the alloy ribbon and provides high toughness. However, if the holding time is too long, the base material, which had high toughness, may become brittle. Furthermore, in order to suppress precipitation of compound phases such as Fe ₃ B, the holding time should not be made too long. Therefore, as for the above-mentioned heat treatment, it is preferable to adjust the temperature increase rate and the holding time in the range of 10 to 70 minutes and the holding temperature in the range of 440 to 470°C, which will be described later.

At this time, if the temperature increase rate of the heat treatment is too slow, the α-Fe crystal grains will grow coarsely, impairing the above-mentioned soft magnetic properties. Therefore, the temperature increase rate during heating is generally set at 200°C/min or more, but high-speed heating at such a temperature increase rate not only consumes a large amount of energy, but also becomes difficult to control as the lot size increases. Productivity becomes poor. On the other hand, even if the lot size is made smaller, the amount of production relative to the energy used and the amount of production per hour are reduced, resulting in poor productivity. However, if an amorphous single-phase alloy ribbon is obtained from an alloy having the above-mentioned composition, the above-mentioned dispersed crystallization of crystal grains can be obtained even at a heating rate of 200° C./min or less. Here, it is preferable that the temperature increase rate is 95 to 200° C./min. For example, even at a temperature increase rate of 100° C./min, the above-mentioned soft magnetic properties can be obtained.

Furthermore, by heating the amorphous single-phase alloy ribbon as described above at a relatively fast temperature increase rate within the range of 200°C/min or less, α-Fe crystal particles crystallize. There is a tendency that the average crystal grain size can be reduced. For example, the average particle diameter can be set to 5 nm or less.

Furthermore, regarding the component composition of the Fe-based alloy, in atomic %, Si: 0.1 to 3.0%, B: 10.0 to 12.0%, C: 0.1 to 3.0%, P: 3.0 to 5.0%, Cu: x% (1.0<x<1.5), Cr:y% (1.0<y<2.0), however, x+y>2.6 , is also preferable. With such a component composition, an amorphous single-phase alloy ribbon can be obtained more easily, and a nanocrystalline soft magnetic material having the above-mentioned soft magnetic properties can be easily manufactured. It is also preferable to contain Fe in an amount of 80 atomic % or more because an amorphous single-phase alloy ribbon can be easily obtained.

[Manufacturing test]
Next, the results of actually manufacturing the nanocrystalline soft magnetic material will be explained using FIGS. 2 and 3.

As shown in FIG. 2, alloy ribbons were first manufactured from alloys having the compositions shown in Alloy 1 to Alloy 12, respectively. A single roll method was used to manufacture the alloy ribbon, and the peripheral speed of the roll, the tapping temperature of the molten metal tapped from the nozzle, and the differential pressure before and after the nozzle were as shown in the manufacturing conditions column.

Regarding the obtained alloy ribbon, the saturation magnetic flux density Bs and coercive force Hc were measured as soft magnetic properties in the as-cast state before heat treatment, and the crystallinity and toughness were also investigated. The saturation magnetic flux density Bs was measured using a vibrating sample magnetometer, and the coercive force Hc was measured using an Hc meter (coercive force meter). Moreover, the crystallinity was calculated based on the XRD pattern. Specifically, it was calculated as the ratio of the areal intensity I _C of the crystalline peak (half width <5°) to the total integrated intensity I _T in the diffraction angle range of 20° < 2θ < 120°. That is, crystallinity (%)=I _C /I _T ×100. Toughness was evaluated by conducting a close bending test (180° bending test) and determining whether or not it would break.

For Alloy 1, Alloy 5 to Alloy 7, and Alloy 10, amorphous single-phase alloy ribbons with relatively low crystallinity could be obtained. Furthermore, since the content of Cu and Cr, which are elements that promote nanocrystalization, was relatively high, nanocrystalization was expected to occur during the subsequent heat treatment.

For Alloy 2, Alloy 4, and Alloy 9, the degree of crystallinity was as high as 20% or more, and there was little possibility of nanocrystallization even with subsequent heat treatment. In response to this result, Alloy 4 was not subjected to subsequent heat treatment. For Alloy 3 and Alloy 8, although the degree of crystallinity was relatively low, the content of Cu and Cr, which are elements that promote nanocrystalization, was low, and the prospect of nanocrystalization by heat treatment was small. Of these, Alloy 3 was not subjected to subsequent heat treatment.

Next, the results of heat treating the alloy ribbon will be explained.

As shown in FIG. 3, the alloy ribbons obtained from Alloy 1, Alloy 2, and Alloys 5 to 12 were heat treated at the heating rate, holding temperature, and holding time shown in "Heat treatment conditions". As a result, in Examples 1 to 8, the saturation magnetic flux density Bs was larger than 1.40 [T] and the coercive force Hc was smaller than 15 [A/m]. Note that Examples 6 to 8 used Alloys 5 to 7, respectively, and were able to reduce the coercive force Hc compared to before heat treatment (see FIG. 2). It is thought that nanocrystalization could be achieved through heat treatment.

On the other hand, in Comparative Example 1 and Comparative Example 2, the coercive force Hc was large. This is thought to be because the holding temperature of the heat treatment was low and the α-Fe crystal particles became coarse.

In Comparative Example 3, the coercive force Hc was large. Although the holding temperature was set at 450°C, the rate of temperature increase was as low as 40°C/min, which is thought to be because the α-Fe crystal particles grew coarsely.

In Comparative Example 4, the holding temperature was also 450° C. and the temperature increase rate was 100° C./min, but the coercive force Hc was still large. In Example 3, even at the same heating rate, the coercive force Hc was kept low by increasing the holding temperature to 470°C. In Comparative Example 4, the holding temperature was low, so the α-Fe crystal It is thought that the particles have become coarser.

In Comparative Examples 5 and 6, the same holding temperature as in Example 3 was set at 470° C., but the coercive force Hc was large. This is thought to be because the temperature increase rates were small, 30° C./min and 40° C./min, respectively, and as a result, α-Fe crystal particles grew coarsely.

In Comparative Examples 7 to 9, Alloy 2 was used, and the temperature increase rate of the heat treatment was increased to 200° C./min in all cases. Although the holding temperature was set to 430°C, 450°C, and 470°C, the coercive force Hc increased in all cases. In Alloy 2, the Cu content was low, and the value of x+y was small when Cu: x atomic % and Cr: y atomic %, and it is thought that nanocrystallization was not sufficient and the crystal grain size was large.

In Comparative Example 10, Alloy 8 was used, but the coercive force Hc was large and the crystal grain size was large. It is considered that nanocrystallization was not sufficient because the value of x+y was small.

In Comparative Examples 11 to 13, Alloy 9 was used and the holding temperature was changed, but the coercive force Hc was large in all cases. Since the Cr content was low and x+y was also small, it is thought that nanocrystalization was not sufficient and the crystal particle size was large, similar to the above. In addition, it is considered that the effect of shortening the holding time of the heat treatment to 10 minutes was not large.

In Comparative Example 14, Alloy 10 was used, but the saturation magnetic flux density Bs was small. This is probably because the Cr content was high and the Fe content was relatively low.

By the way, the composition range of the Fe-based alloy that can provide soft magnetic properties almost equivalent to those of the nanocrystalline soft magnetic materials including the above-mentioned Examples is determined as follows.

Si, B, and C are amorphous forming elements and cooperate with each other to form an amorphous state in the alloy ribbon. On the other hand, if Si is contained excessively, the ability to form an amorphous state will be reduced, and the saturation magnetic flux density of the resulting nanocrystalline soft magnetic material will be reduced. When B is contained excessively, compound phases such as Fe ₃ B and Fe ₂ B having high crystal magnetic anisotropy are precipitated, which also leads to an increase in cost. Excessive content of C lowers the crystallization temperature from the amorphous phase, leading to coarsening of crystal grains. Considering these and the balance between the content of each element, the content was determined as follows. That is, Si is in the range of 0.1 to 5.0%, preferably in the range of 0.1 to 3.0%, in atomic %. Further, B is in the range of 5.0 to 12.0%, preferably in the range of 10.0 to 12.0% in atomic %. Further, C is in the range of 0.1 to 5.0%, preferably in the range of 0.1 to 3.0% in atomic %.

Although P is an amorphous-forming element, it does not interact much with other amorphous-forming elements, and the amorphous-forming ability can be improved by increasing the content alone. On the other hand, when P is contained excessively, the saturation magnetic flux density of the resulting nanocrystalline soft magnetic material is reduced. Considering these, P is in the range of 2.0 to 6.0%, preferably in the range of 3.0 to 5.0%, in atomic %.

Cu combines with P to form clusters of nanoheterostructures and is finely dispersed in the amorphous matrix, thereby suppressing coarsening of α-Fe crystals. On the other hand, when Cu is contained excessively, the coercive force of the resulting nanocrystalline soft magnetic material increases. Taking these into consideration, Cu is defined as x% in atomic %, within the range of 1.0<x<2.5, preferably within the range of 1.0<x<1.5.

Cr is concentrated in the remaining amorphous phase during the nanocrystallization heat treatment and promotes stabilization. This suppresses the coarsening of nanocrystal grains and facilitates obtaining a fine and uniform nanocrystalline structure. It also improves corrosion resistance, suppresses the occurrence of rust, and maintains the coercive force of the resulting nanocrystalline soft magnetic material at a low level. On the other hand, when Cr is contained excessively, the amorphous formation ability is reduced and the coercive force of the resulting nanocrystalline soft magnetic material is increased. Taking these into consideration, Cr is expressed as y% in atomic %, and is within the range of 1.0<y<3.0, preferably within the range of 1.0<y<2.0.

Moreover, x+y is an index of the content of Cu and Cr, which are elements that promote nanocrystallization in the obtained nanocrystalline soft magnetic material, and is within the range of x+y>2.6.

Although typical embodiments of the present invention have been described above, the present invention is not necessarily limited to these, and those skilled in the art will understand without departing from the spirit of the present invention or the scope of the appended claims. , various alternative embodiments and modifications may be found. For example, the nanocrystalline soft magnetic material according to the invention may be a ground powder material.

Claims (4)

A nanocrystalline soft magnetic material in which crystal particles with an average particle size of 15 nm or less are dispersed in an amorphous matrix consisting of an Fe-based alloy,
In atomic percent,
Si: 1.08 to 5.0%,
B: 10.0-12.0%,
C: 1.25 to 5.0%,
P: 2.0-6.0%,
Cu: x% (1.0<x<2.5),
Cr: y% (1.0<y≦2.3), however, x+y>2.6,
has an alloy composition consisting of the remainder Fe and unavoidable impurities,
Nanocrystalline soft magnetism characterized by having a crystallinity of 60% or more, a coercive force Hc smaller than 15 [A/m], and a saturation magnetic flux density B:s larger than 1.40 [T]. material. The alloy composition is in atomic %,
Si: 1.08 to 3.0%,
B: 10.0-12.0%,
C: 1.25 to 3.0%,
P: 3.0-5.0%,
Cu: x% (1.0<x<1.5),
Cr: y% (1.0<y<2.0), however, x+y>2.6,
The nanocrystalline soft magnetic material according to claim 1, characterized in that the remainder consists of Fe and unavoidable impurities. 3. The nanocrystalline soft magnetic material according to claim 1, wherein the alloy composition contains Fe at 80.0 atomic % or more. The nanocrystalline soft magnetic material according to claim 1, wherein the average particle diameter of the crystal particles is 5 nm or less.

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