JPH0853710A - Method for heat-treating nano-crystalline alloy - Google Patents

Abstract

PURPOSE:To produce a nano-crystalline alloy excellent in magnetic properties by subjecting an amorphous alloy to heat treatment in a gaseous atmosphere having a specified dew point, crystallizing the same and allowing crystal grains having a specified average grain size to occupy a part of the structure. CONSTITUTION:An amorphous alloy is prepd. by a superrapid cooling method such as a single roll method, which is subjected to heat treatment and is crystallized to produce a nano-crystalline alloy in which crystal grains having 430nm average grain size occupy at least a part of the structure. At this time, it is subjected to heat treatment (at about 550 deg.C) in an atmosphere of gaseous argon, gaseous helium, gaseous nitrogen or a gaseous mixture thereof. Thus, the nano- crystalline alloy having an ultrafine grain structure and excellent in magnetic properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for a nanocrystalline alloy used for magnetic parts having an ultrafine grain structure.

[0002]

2. Description of the Related Art Since nanocrystalline alloys have excellent soft magnetic properties, common mode choke coils, high frequency transformers,
It is used in magnetic cores such as leakage alarms and pulse transformers. Typical composition systems include Japanese Patent Publication No. 4393/1992 and Japanese Patent Laid-Open No. 1-2427.
The alloy system and the like described in JP-A-55 are known. These nanocrystalline alloys are usually produced by rapidly cooling from a liquid phase or a vapor phase to form an amorphous alloy, and then microcrystallizing the amorphous alloy by heat treatment. As a method of quenching from a liquid phase to obtain an amorphous alloy, a single roll method, a twin roll method, a centrifugal quenching method, a rotating submerged spinning method, an atomizing method, a cavitation method and the like are known. Further, as a method of quenching from a vapor phase to form an amorphous alloy, a sputtering method, a vapor deposition method, an ion plating method and the like are known. Nanocrystalline alloy is a microcrystal of amorphous alloy produced by these methods, and it has almost no thermal instability as seen in amorphous alloy, high saturation magnetic flux density, low magnetostriction and excellent softness. It is known to exhibit magnetic properties. Furthermore, the nanocrystalline alloy has a small change over time,
It is also known to have excellent temperature characteristics.

[0003]

The heat treatment of the nanocrystalline alloy is usually carried out in an inert gas such as nitrogen gas or argon, but the gas used often causes deterioration in magnetic properties, which has been a problem. . An object of the present invention is to provide a heat treatment method for a nanocrystalline alloy having a uniform and ultrafine grain structure and excellent magnetic properties.

[0004]

In order to solve the above problems, the inventors of the present invention have made earnest studies, and as a result, when the surface has an altered layer such as oxide or hydroxide, the magnetic properties It was found that the magnetic field deteriorates and the magnetic characteristics themselves vary widely. Therefore, in order to prevent the generation of this deteriorated layer, it was found that the amount of water in the gas atmosphere during the heat treatment should be controlled, that is, the dew point in the gas atmosphere should be controlled, and the present invention was conceived. That is, the present invention is a heat treatment method for producing a nanocrystalline alloy in which an amorphous alloy is crystallized to have a crystal grain having an average crystal grain size of 30 nm or less occupying at least a part of the structure, and the heat treatment has a dew point of −30 ° C. It is a heat treatment method for a nanocrystalline alloy, which is characterized in that it is carried out in the following gas atmosphere. The dew point is limited to -30 ° C or lower because when the dew point exceeds -30 ° C, the alloy surface alteration layer increases and magnetic properties such as magnetic permeability deteriorate.

Particularly in a gas atmosphere having a dew point of -60 ° C or lower, the magnetic properties are further improved and more preferable results are obtained. The dew point is -30 ° C, the water content is 337.7 mg / m ³ , and the dew point is -60 ° C.
This corresponds to a water content of 10.93 mg / m ³ . When an inert gas such as argon gas, helium gas, nitrogen gas or a mixed gas thereof is used as the atmosphere gas, excellent magnetic properties are obtained and the effect of the present invention is remarkable.

[0006] Nanocrystalline soft magnetic alloy is particularly the general formula: represented by _{(Fe 1-a M a)} 100-xyzb A x M 'y M''z X b ( atomic%), M in the formula is Co, Ni At least one element selected from, A is at least one element selected from Cu, Au, M'is at least 1 selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W. Species element, M '' is at least one selected from Cr, Mn, Al, Sn, Zn, Ag, In, white metal element, Mg, Ca, Sr, Y, rare earth element, N, O and S. Element, X represents at least one element selected from B, Si, C, Ge, Ga and P, a, x, y, z and b are 0 ≦ a ≦ 0.5, 0 ≦ x ≦ 10, 0.1 ≦ y ≦ 20, 0 ≦ z ≦ 2
Excellent soft magnetic properties are obtained in the case of a composition represented by a number satisfying 0 and 2 ≦ b ≦ 30.

The above-mentioned crystal is mainly a bccFe phase, and when Si is contained, Si may form a solid solution in the bcc phase and may contain an ordered lattice. In addition, elements other than Si, such as B, Al, Ge, Zr, and Ga, may be solid-solved. The balance other than the crystalline phase is mainly an amorphous phase, but in some cases it may consist essentially of the crystalline phase. The alloy according to the present invention is produced by forming an amorphous alloy having the above composition by an ultra-quenching method such as a single roll method, processing it into a shape of a magnetic core, and crystallizing it in a gas atmosphere with a dew point of -30 ° C or less. Average particle size
It is produced by forming ultrafine crystal grains of 30 nm or less.
A magnetic field may be applied during the heat treatment to perform the heat treatment in the magnetic field.

It is more preferable to forcibly move the atmospheric gas in the furnace, because the heat generated by crystallization from the surface of the magnetic core can be dissipated better, and an abnormal rise in the magnetic core temperature can be suppressed. The result can be obtained.
The same effect can be obtained by introducing the atmospheric gas into the furnace from the outside of the furnace, discharging the gas in the furnace, and forcibly moving the atmospheric gas in the furnace. By forcibly stirring and moving the atmosphere gas in the furnace with a fan or the like, the heat radiation from the surface of the magnetic core can be improved, and the same effect can be obtained.

By providing a mechanism for adjusting the moving amount of the atmospheric gas in the furnace so that the difference between the surface temperature of the nanocrystalline alloy and the set temperature of the furnace is 50 ° C. or less, even if the shape becomes large, it becomes easy. It will be possible. Particularly, when the difference between the surface temperature of the nanocrystalline alloy and the set temperature of the furnace is 10 ° C or less, the deterioration of the characteristics and the variation of the characteristics are small, and a preferable result is obtained.

[0010]

In the present invention, when the dew point of the atmospheric gas used during the heat treatment is set to -30 ° C or less, the alloy surface-altered layer affecting the magnetic properties can be reduced, and the deterioration of the magnetic properties can be reduced.

[0011]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. (Example 1) Cu 1%, Nb 3%, Si 15.4%, B 6.5% in atomic%
The rest of the molten alloy consisting essentially of Fe was rapidly cooled by a single roll method to obtain an amorphous alloy with a width of 5 mm and a thickness of 18 μm. This amorphous alloy was wound around an outer diameter of 20 mm and an inner diameter of 12 mm to produce a toroidal magnetic core. The manufactured magnetic core was inserted into a heat treatment furnace maintained at 550 ° C. in a nitrogen gas atmosphere having different dew points shown in Table 1, held for 30 minutes, taken out of the furnace, and air-cooled. After heat treatment, bcc crystals with a grain size of about 12 nm occupy most of the structure. Table 1 shows the relative initial permeability μ _r at 1 kHz. Table 1
As can be seen from the above, μ _r remarkably improves when the dew point is -30 ° C or lower. In particular, high magnetic permeability was obtained at -60 ° C or lower.

[0012]

[Table 1]

Example 2 A molten alloy having the composition shown in Table 2 was rapidly cooled by a single roll method to obtain an amorphous alloy having a width of 25 mm and a thickness of 16 μm. This amorphous alloy was wound around an outer diameter of 20 mm and an inner diameter of 12 mm to produce a toroidal magnetic core. Each of the magnetic cores produced was inserted into a heat treatment furnace in which the dew points were −65 ° C. and −10 ° C. and the atmosphere gas shown in Table 2 was kept at 550 ° C. After holding for 30 minutes, it was taken out of the furnace and air cooled. The alloy after heat treatment has a particle size of about 12 nm.
The bcc crystals occupy most of the texture. The magnetic properties obtained are shown in Table 2. As can be seen from Table 2, the lower the dew point is -65 ° C, the better the magnetic permeability. Further, the alloy having a length of 200 mm was heat-treated under the same conditions, and the relative permeability μ _r at 1 kHz was measured. The sample surface after the measurement was removed by etching, and the relative magnetic permeability μ _re was measured again. Ratio of relative permeability before etching and relative permeability after etching μ _re / μ _r
Is shown in Table 3.

[0014]

[Table 2]

[0015]

[Table 3]

When the dew point is as high as −10 ° C., μ _re / μ _r is considerably larger than 1, and the magnetic permeability is greatly improved by removing the surface layer. On the other hand, when the dew point is as low as -65 ° C, there is almost no effect of etching and the value is close to 1. This indicates that when the dew point is as low as -65 ° C, it is difficult to form a surface-altered layer that affects the magnetic properties.

[0017]

According to the present invention, it is possible to provide a heat treatment method for a nanocrystalline alloy having an ultrafine grain structure and excellent magnetic properties.

Claims (4)

[Claims] 1. A heat treatment method for crystallizing an amorphous alloy to produce a nanocrystalline alloy in which crystal grains having an average crystal grain size of 30 nm or less occupy at least a part of a structure,
A heat treatment method for a nanocrystalline alloy, characterized in that the heat treatment is performed in a gas atmosphere having a dew point of -30 ° C or lower. 2. The heat treatment method for a nanocrystalline alloy according to claim 1, wherein the dew point is in a gas atmosphere at -60 ° C. or lower. 3. The heat treatment method for a nanocrystalline alloy according to claim 1, wherein the atmosphere gas is argon gas, helium gas, nitrogen gas, or a mixed gas thereof. 4. The nanocrystalline alloy general formula is represented by _{(Fe 1-a M a)} 100-xyzb A x M 'y M''z X b ( atomic%), M in the formula is Co, the Ni At least one element selected, A is at least one element selected from Cu, Au, M'is at least one selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W , M '' is at least one element selected from Cr, Mn, Al, Sn, Zn, Ag, In, white metal element, Mg, Ca, Sr, Y, rare earth element, N, O and S. , X represents at least one element selected from B, Si, C, Ge, Ga and P, a, x, y, z and b are 0 ≦ a ≦ 0.5, 0 ≦ x ≦ 10, 0.1, respectively. ≤y≤20, 0≤z≤2
The heat treatment method for a nanocrystalline alloy according to any one of claims 1 to 3, wherein the composition has a composition represented by a number satisfying 0 and 2 ≤ b ≤ 30.