JPH03271346A - Soft magnetic alloy - Google Patents

Abstract

PURPOSE:To obtain a soft magnetic alloy having excellent magnetic properties in a high frequency range by specifying a compsn. constituted of Fe, Cu, Si, B, Ni, Co, Nb, W, Ta, Mo, V, Cr and Mn and forming a specified crystalline structure in an alloy. CONSTITUTION:This alloy is a soft magnetic one having an atomic ratio compsn. expressed by a formula: (Fe1-aM<0>a)100-x-y-z-p-q CuxSiyBzM<1>pM<2>q (where M<0> denotes Ni or Co, M<1> denotes Nb, W, Ta or Mo and M<2> denotes V, Cr or Mn as well as 0<=a<=0.2, 0.1<=x<=3, 0<=y<=30, 0<=z<=25, 5<=y+z<=30, 0.1<=p<=30 and 0<=q<=10 are satisfied), in which the structure has crystalline grain and crystalline grains boundary and the average maximum size of each crystalline grain is regulated to 50 to 200Angstrom as well as the average of the shortest distance between the adjacent crystalline grains is regulated to 10 to 50% to the average of the maximum size of the above each crystalline grain. The alloy has high magnetic properties in a high frequency range as well as having good heat stability with a small change with the lapse of time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an Fe-based magnetomagnetic alloy having microcrystalline grains.

<Prior Art> Since amorphous alloys have a high saturation magnetic flux density, they are used in magnetic cores of high frequency transformers, saturable reactors, various choke coils, and magnetic heads.

Amorphous alloys are generally classified into Fe-based amorphous alloys containing Fe as a main component and CO-based amorphous alloys containing CO as a main component. Fe-based amorphous alloys have a high saturation magnetic flux density and are inexpensive materials, but have large losses in high frequency regions and low magnetic permeability.

On the other hand, Co-based amorphous alloys have good magnetic properties at high frequencies, but the magnetic properties change significantly over time, and the material is expensive.

Under these circumstances, Japanese Patent Application Laid-Open No. 64-39347 discloses that at least 50% of the structure consists of fine crystal grains,
An Fe-based magnetomagnetic alloy is disclosed that has an average grain size of 1000 Å or less as measured by the largest grain size. According to the publication, the area around the fine crystal grains is mainly amorphous, and exhibits sufficiently excellent magnetic properties even when the proportion of fine crystal grains becomes substantially 100%. Further, this Fe-based magnetomagnetic alloy can obtain magnetic properties comparable to those of a CO-based amorphous alloy, and moreover, its change over time can be suppressed.

<Problem to be solved by the invention> However, according to the research of the present inventors, the F described in the above publication
The following problems arise due to the structure of e-based magnetomagnetic alloys.

For example, if the area around fine crystal grains, that is, the grain boundaries, is amorphous, the magnetic permeability decreases significantly near the Curie temperature of this amorphous state. For this reason, in a high-frequency magnetic core that generates a lot of heat, the temperature stability of magnetic permeability becomes low. Also,
As amorphous materials undergo structural changes due to aging, the average magnetic properties of the entire structure deteriorate over time.

In addition, in polycrystalline alloys, the direction of the crystal lattice of a crystal grain is different from the direction of the crystal lattice of adjacent crystal grains, so if the proportion of fine crystal grains is substantially 100%, the boundaries between adjacent crystal grains The direction of the crystal lattice changes rapidly, and this becomes a pinning site, making it difficult to obtain good magnetic properties, especially at high frequencies.

The present invention was made under these circumstances, and an object of the present invention is to provide a soft magnetic alloy that has high magnetic properties in a high frequency region, has high thermal stability of magnetic properties, and has little change over time.

Means for Solving the Problems> Such objects are achieved by the present invention described in (1) and (2) below.

(1> A soft magnetic alloy having an atomic composition represented by the following formula, which has crystal grains and crystal grain boundaries, and the average maximum diameter of each crystal grain is 50 to 200 Å, A soft magnetic alloy characterized in that the average shortest distance between adjacent crystal grains is 10 to 50% of the average maximum diameter of each of the crystal grains.

[Formula] %Formula% (However, in the above formula, Mo represents one or more elements selected from Ni and CO, and Ml represents Nb, W,
Represents one or more elements selected from Ta and MO, M2 represents one or more elements selected from ■, Cr and Mn, 0≦a≦0.2, O11≦X≦3゜0≦ y≦30°O≦Z≦25°5≦y+z≦30°0.1≦p≦30, O≦q≦10. ) (2) The soft magnetic alloy according to (1) above, wherein in a cross section, the area of the grain boundary divided by the area of the grain is 20 to 100%.

<Function> The soft magnetic alloy of the present invention has crystalline grain boundaries;
The thermal stability of magnetic properties is good and there is very little change over time.

In addition, the grain boundaries in the present invention have the effect of preventing pinning sites from occurring at the boundaries of each grain, and the relationship between the grain size and the grain boundary size is configured as described above. , exhibits extremely excellent magnetic properties, especially in the high frequency range.

Moreover, since it has fine crystal grains, magnetostriction is extremely small.

<Specific configuration> Hereinafter, the specific configuration of the present invention will be explained in detail.

The atomic ratio composition of the soft magnetic alloy of the present invention is expressed by the following formula % Formula % [Formula] % Formula % However, in the above formula, Mo represents one or more elements selected from Ni and Co, Ml represents Nb, W,T
represents one or more elements selected from a and MO,
M2 represents one or more elements selected from V, Cr and Mn, 0≦a≦0.2゜0.1≦X≦3, O≦y≦30, O≦2≦25゜5≦y+z ≦30°0, l≦p≦30°O≦q≦10°.

The reasons for limiting the above composition will be explained.

When a representing the content of Mo exceeds the above range, iron loss may increase.

Cu is an essential element when forming a microcrystalline phase by heat treatment described below. If X representing the Cu content is outside the above range, the magnetic properties will deteriorate, particularly the magnetic permeability will become low.

Ml is contained in order to obtain a uniform microcrystalline phase without producing coarse crystal grains. Furthermore, by containing Ml, extremely high magnetic permeability can be obtained.

As Ml, it is preferable to use Nb and/or Mo because the magnetic properties are improved, and it is particularly preferable to make Nb essential.

In addition, since corrosion resistance is improved, W and/or M
It is preferable to use o.

If p, which represents the content of M', is outside the above range, the magnetic properties will deteriorate.

Si and B are contained to make the alloy amorphous. In the present invention, an amorphous alloy is produced by high-speed quenching of alloy infiltration, and fine crystal grains are formed by heat-treating this amorphous alloy.
The inclusion of at least one of these is essential.

If y representing the Si content, 2 representing the B content, and y+z are outside the above ranges, it will be difficult to make the alloy amorphous and the magnetic properties will deteriorate.

In addition to Si and B, C and Ge are used as vitrification elements.
, P, Ga, Sb, In%Be, and As. These vitrifying elements, together with Si and B, have the effect of promoting amorphization, and also have the effect of adjusting the Curie temperature and magnetostriction. These vitrifying elements are preferably contained so as to replace 30% or less of the total content of SL and B, that is, y+Z.

M2 is contained in order to improve the corrosion resistance and magnetic properties of the soft magnetic alloy, and to adjust the magnetostriction.

When q representing the content of M2 exceeds the above range, the saturation magnetic flux density decreases.

Among M2, Cr and ■ have a high effect of improving corrosion resistance, and it is preferable to contain one or more of these, and it is particularly preferable to make Cr essential. Note that in order to significantly improve corrosion resistance, , q are preferably 2 or more, particularly 3 or more.

In addition to the elements listed above, the soft magnetic alloy of the present invention also contains Zr.
, Hf, Ti, A11, platinum group elements, Sc%Y, rare earth elements, Au, Zn%Sn, and Re. Among these elements, Zr, Hf and Ti have the same effect as Ml described above. In addition, A11, platinum group elements, Sc, Y,
The rare earth elements, Au, Zn, Sn, and Re have the same effect as M2 described above. When these elements are contained, the total content is preferably 10% or less with respect to the composition represented by the above formula.

Note that the soft magnetic alloy may contain unavoidable impurities such as N, 0, and S, as long as they do not adversely affect the magnetic properties.

The soft magnetic alloy of the present invention has fine crystal grains and crystalline grain boundaries. According to the results of X-ray diffraction, the crystal grains usually have a structure in which each of the above elements is dissolved in a bcc structure of α-Fe. In addition, although it is difficult to identify the crystal structure of grain boundaries, the b
Since only the peak derived from the cc structure is observed,
Usually, it is considered to be a structure in which each of the above elements is dissolved in the bcc structure of α-Fe, similar to crystal grains.

In the present invention, the average maximum diameter of each crystal grain is 50 to 20
The average shortest distance between adjacent grains, that is, the average minimum width of grain boundaries, is 10 to 50%, preferably 10 to 40%, of the average maximum diameter of each grain. .

By setting the dimensions of the crystal grains and the dimensions of the crystal grain boundaries within such ranges, good magnetic properties, particularly high magnetic permeability in a high frequency region, can be obtained.

More specifically, when the width of the grain boundary is less than the above range,
The pinning site prevention effect becomes insufficient, and high magnetic permeability cannot be obtained, especially in the high frequency region.

In addition, in order to achieve higher magnetic permeability in the high frequency region, the value obtained by dividing the area of grain boundaries by the area of crystal grains in the cross section of the soft magnetic alloy must be 20 to 100%, especially 20 to 8
Preferably it is 0%.

Note that the dimensions and areas of crystal grains and grain boundaries can be measured using a transmission electron microscope. In this case, measurement is performed in a visual field in which two or more crystal grains do not overlap.

A difference in concentration occurs between crystal grains and grain boundaries due to differences in the direction of the crystal lattice and the solid solution state of each element, and a crystal lattice structure can also be observed within the crystal grains and within the grain boundaries.

The method for manufacturing the soft magnetic alloy of the present invention will be explained below.

The soft magnetic alloy of the present invention is produced by rapidly cooling a molten metal of the alloy represented by the above formula to obtain an amorphous alloy, and then subjecting it to heat treatment to form the above crystal grains and grain boundaries.

There is no particular restriction on the method for rapidly cooling the molten alloy, and it can be selected from various rapid cooling methods such as a single roll method, a twin roll method, an atomization method, a water atomization method, and the like.

There are no restrictions on the atmosphere during quenching, and it may be in air, an inert gas atmosphere, or the like.

In addition, a ribbon-shaped amorphous alloy is obtained by the single-roll method or the twin-roll method. In these methods, when the molten alloy collides with the roll surface, it entrains gases in the atmosphere.
The thinner the ribbon, the worse its surface properties.

On the other hand, when a ribbon-shaped soft magnetic alloy is wound to form a wound magnetic core,
The better the surface properties of the ribbon, the better its magnetic properties at high frequencies, so when used for such purposes, it is preferable to perform the rapid cooling under reduced pressure. There is no particular limit to the degree of pressure reduction, but for example, 2 X IO' to I X 10-'
It is preferable to set it to about Pa.

Moreover, by rapidly cooling in a reduced pressure atmosphere in this way, crystallization of grain boundaries can be favorably promoted during heat treatment.

The temperature and time of the heat treatment applied to the amorphous alloy varies depending on the composition, dimensions, etc. of the amorphous alloy to be heat treated, but is preferably 450 to 700°C for 5 minutes to 24 hours.

If the heat treatment temperature is less than the above range, it will be difficult to form fine crystal grains, and if it exceeds the above range, the crystal grains will become coarse, making it impossible to obtain a soft magnetic alloy with high magnetic properties.

If the heat treatment time is less than the above range, it will be difficult to perform uniform heating, and if it exceeds the above range, the crystal grains will become coarse, making it impossible to obtain a soft magnetic alloy with high magnetic properties.

In addition, the more preferable heat treatment temperature and heat treatment time are 5.
00 to 650°C for 5 minutes to 6 hours.
There is no particular restriction on the atmosphere during the I heat treatment, and the heat treatment may be carried out in air, but it is preferably carried out in vacuum or in an inert gas atmosphere such as nitrogen, hydrogen, or Ar.

However, since the grain boundaries can be easily crystallized, it is preferable to perform the heat treatment in a pressurized atmosphere.
The degree of pressurization is 0.11M Pa or more, especially 0.2M
It is preferable to set it as about Pa-IGPa.

Note that this heat treatment may be performed in a magnetic field if necessary.

The shape of the soft magnetic alloy of the present invention is not limited, and it can be used for various purposes in the form of ribbons, flakes, granules, etc., or it may be crushed and used as powder.

Furthermore, the soft magnetic alloy of the present invention is ideal for applications that require high magnetic properties, particularly at high frequencies, such as high frequency transformers, saturable reactors, and magnetic cores of various choke coils.

<Examples> Hereinafter, the present invention will be explained in more detail by giving specific examples.

(Fea, 5coo, x)yscu+Taasl+
A molten metal of an alloy represented by Je (numbers are atomic ratios) was rapidly cooled by a single roll method to obtain an amorphous alloy ribbon having a thickness of log and a width of 5 mm. In addition, the rapid cooling is performed at 5×10-”Pa
It was carried out in a vacuum.

This amorphous alloy ribbon was heat treated at 500° C. for 2 hours to form fine crystal grains. Heat treatment is IMP
The test was carried out in an Ar gas atmosphere (a).

This alloy ribbon was polished and used as a measurement sample, and the average maximum diameter d of the crystal grains, the average minimum width t of the grain boundaries, the area 81 of the crystal grains, and the area 82 of the grain boundaries were determined using a transmission electron microscope. was measured, and t/d and s 2 /s 1 were determined.
The results are shown in Table 1 below.

Furthermore, a transmission electron micrograph of this measurement sample is shown in FIG. In addition, FIG. 2 is a diagram schematically showing the crystal lattice structure of the grain boundaries by enlarging the area E-e in FIG. 1.

Next, the ribbon is wound into a toroidal shape to form a magnetic core sample N.
It was set as O43.

For this sample, the initial permeability μ at 100 kHz is
m was measured. The results are shown in Table 1.

Further, magnetic core samples shown in Table 1 were prepared in the same manner as the above samples except that the pressure during quenching and the pressure during heat treatment were changed, and the same measurements as above were performed. Table 1 shows the results.
Shown below.

Table 1 1 (comparison) 121 5 11 500002
107 16 34 900003
98 33 71 1100004 (comparison)
8658131 The effects of the present invention are clear from more than 60,000 examples.

As shown in FIG. 2, it is clear that a crystal lattice with a lattice spacing of about 2 people exists at the grain boundaries in FIG. Crystal lattices at grain boundaries were also confirmed in other samples.

<Effects of the Invention> Since the soft magnetic alloy of the present invention has crystalline grain boundaries, it has good magnetic properties at high frequencies and has little change over time.

[Brief explanation of drawings]

FIG. 1 is a photograph substituted for a drawing showing the crystal structure, and is a transmission electron micrograph of the soft magnetic alloy of the present invention. FIG. 2 is an explanatory diagram schematically showing a part of FIG. 1 in an enlarged manner.

Claims (2)

[Claims] (1) A soft magnetic alloy having an atomic composition represented by the following formula, which has crystal grains and crystal grain boundaries, and the average maximum diameter of each crystal grain is 50 to 200 Å, A soft magnetic alloy characterized in that the average shortest distance between adjacent crystal grains is 10 to 50% of the average maximum diameter of each of the crystal grains. [Formula] (Fe_1_-_aM^0_a)_1_0_0_-_x
＿−＿y＿−＿z＿−＿p＿−＿qCu_xSi_yB
＿zM^1_pM^2_q (However, in the above formula,
M^0 represents one or more elements selected from Ni and Co, M^1 represents one or more elements selected from Nb, W, Ta, and Mo, and M^2 represents V, Cr, and Mo. Represents one or more elements selected from Mn, 0≦a
≦0.2, 0.1≦x≦3, 0≦y≦30, 0≦z≦25, 5≦y+z≦30, 0.1≦p≦30, 0≦q≦10. ) (2) The soft magnetic alloy according to claim 1, wherein in a cross section, a value obtained by dividing the area of the grain boundary by the area of the grain is 20 to 100%.