JPH0684624A - Rare earth metal-iron-boron based powder for anisotropic permanent magnet and production thereof - Google Patents

Abstract

PURPOSE:To obtain a powder material for permanent magnet having high anisotropy and excellent magnet characteristics by subjecting a rare earth-iron- boron based alloy ingot for permanent magnet, containing specified vol.% or more of crystal having specified particle size, to hydrogenation. CONSTITUTION:A rare earth-iron-boron based alloy ingot containing 90vol.% or more of crystal having particle size of 0.1-50mum in short axis direction and 0.1-100mum in long axis direction is employed as a material for permanent magnet. The alloy ingot is subjected to hydrogenation to produce a rare earth-iron- boron based powder for anisotropic permanent magnet. This powder exhibits high anisotropy and quite excellent magnet characteristics and thereby employed as a material for resin magnet or bond magnet. Furthermore, the powder for anisotropic permanent magnet having excellent characteristics can be produced easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth metal-iron-boron anisotropic anisotropic permanent magnet powder having excellent magnet characteristics and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, alloy ingots for permanent magnets are generally produced by a die casting method in which a molten alloy is cast in a die. However, when solidifying the alloy melt by the die casting method, in the heat removal process of the alloy melt,
In the initial stage of heat removal, the heat transfer rate is controlled by the mold, but when solidification proceeds, heat transfer between the mold and the solidification phase and in the solidification phase becomes heat control, and even if the mold cooling capacity is improved, the casting inside the ingot and in the vicinity of the mold In the ingot, the cooling conditions are different, and such a phenomenon occurs especially when the ingot thickness is large. When there is a large difference in the cooling conditions between the inside of the ingot and the vicinity of the surface as described above, the primary structure γ-F,
There is a large amount of e, and for this reason the grain size is 10 to 1 in the center of the ingot.
00 μm of α-Fe remains, and at the same time, the size of the rare earth metal-rich phase surrounding the main phase also increases.

Further, in the ingot structure obtained by the die casting method, the minor axis direction is 0.1 to 50 μm, and the major axis direction is 0.1 to 50 μm.
It is known that there is a crystal having a crystal grain size of 100 μm, but the content of the crystal is small and has not yet exerted a good influence on the magnet characteristics.

On the other hand, in the homogenization treatment process in the magnet powder manufacturing process, the homogenization treatment is usually performed at around 1000 ° C., but in the case of the ingot obtained by the die casting method,
Since it contains α-Fe having a large particle size and a large phase rich in rare earth metal, it is difficult to homogenize it, and it is difficult to be anisotropic during the recrystallization by the subsequent hydrotreatment, so that it is finally obtained. However, there is a drawback that the magnetic characteristics of the permanent magnets are deteriorated.

Further, a rare earth metal element, cobalt and, if necessary, iron, copper and zirconium are added and dissolved in a crucible, and then a strip casting method in which twin rolls, single rolls, twin belts and the like are combined is used. 0.01 ~
A method for producing an alloy for rare earth metal magnets, which is solidified to have a thickness of 5 mm, has been proposed.

According to this method, an ingot having a uniform composition can be obtained as compared with the die casting method, but the raw material component is a rare earth metal element,
Since cobalt and, if necessary, a combination of iron, copper, and zirconium are components, there is a problem in that the magnet performance cannot be sufficiently improved by the strip casting method.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rare earth metal-iron-boron-based anisotropic permanent magnet having a high anisotropy and a crystal structure that most affects the properties of the permanent magnet. To provide a powder and a manufacturing method thereof.

[0008]

According to the present invention, a rare earth metal-iron containing 90% by volume or more of crystals having a crystal grain size of 0.1 to 50 μm in the minor axis direction and 0.1 to 100 μm in the major axis direction. Α-Fe having a grain size of less than 10 μm, which is a peritectic nucleus, in the alloy ingot for a boron-based permanent magnet or in the main phase crystal grains of the alloy.
And / or rare earth metal-iron-boron-based anisotropic permanent magnet powder obtained by homogenizing the alloy ingot for permanent magnet in which γ-Fe is finely dispersed, if necessary, and then hydrotreating. Will be provided.

Further, according to the present invention, the rare earth metal-iron-boron alloy melt is uniformly solidified under cooling conditions of a cooling rate of 10 to 1000 ° C./sec and a supercooling degree of 10 to 500 ° C. Metal-iron-boron-based alloy ingots for permanent magnets are characterized by performing hydrogenation treatment by injecting and releasing hydrogen atoms in a hydrogen atmosphere, recrystallizing, and then crushing. A method for producing a powder for an anisotropic boron permanent magnet is provided.

The present invention will be described in more detail below.

The rare earth metal-iron-boron-based anisotropic permanent magnet powder of the present invention (hereinafter referred to as anisotropic permanent magnet powder 1) has a minor axis direction of 0.1 to 50 μm and a major axis direction of 0.1. 1 to
90% by volume or more of crystals having a crystal grain size of 100 μm,
Preferably, a rare earth metal-iron-boron-based anisotropic permanent magnet powder obtained by hydrotreating a rare earth metal-iron-boron-based alloy ingot (hereinafter referred to as alloy ingot 2) containing 98% by volume or more. And the particle size of the powder is 200 to 400 μm.
It is preferably m. The alloy ingot 2 has, in particular, α-Fe and // which are usually contained as peritectic nuclei in the main phase crystal grains.
Or preferably contains no γ-Fe, and in the case of containing the α-Fe and / or γ-Fe,
The particle size of the α-Fe and / or γ-Fe is preferably less than 10 μm and finely dispersed. At this time, if the content ratio of the crystals having the specific crystal grain size is less than 90% by volume, excellent alloy properties cannot be imparted to the obtained alloy ingot, and the target anisotropic permanent magnet powder is obtained. I can't get 1. When the lengths in the minor axis direction and the major axis direction are out of the above range, or the α-Fe and / or γ-Fe
If the particle size is 10 μm or more and is not finely dispersed, the homogenization time in the homogenization process in the permanent magnet powder manufacturing process becomes long, and the magnetic properties of the final magnet powder are low. Therefore, it is not preferable. Further, the thickness of the alloy ingot 2 is preferably in the range of 0.05 to 15 mm. When the thickness exceeds 15 mm, the manufacturing method described later for obtaining a desired crystal structure becomes difficult, which is not preferable.

The raw material components forming the alloy ingot 2 used for the anisotropic permanent magnet powder 1 are not particularly limited as long as they are a rare earth metal-iron-boron system, and they are unavoidable during normal production. It may also contain other impurity components that are inherently contained. The rare earth metal may be a single substance or a mixture. The mixing ratio of the rare earth metal, boron, and iron is
It may be the same as the compounding ratio in the usual alloy for permanent magnets, preferably 25 to 40: 0.5 to 2.0: remaining amount by weight.

In the production method of the present invention, first, a rare earth metal-
Cool the iron-boron alloy melt at a cooling rate of 10 to 1000 ° C.
/ Sec, preferably 100 to 1000 ° C / sec, supercooling degree 10
To 500 ° C., preferably 200 to 500 ° C., to uniformly solidify to obtain the alloy ingot 2 and then to inject and release hydrogen atoms into the alloy ingot 2 in a hydrogen atmosphere to form a main phase. The present invention is characterized in that after recrystallizing crystals and the like, hydrogenation treatment of crushing is performed.

In this case, the degree of supercooling is a value of (melting point of alloy)-(actual temperature of alloy melt) and has a correlation with a cooling rate. If the cooling rate and the degree of supercooling are outside the above-mentioned essential ranges, an alloy ingot having a desired structure cannot be obtained.

The production method of the present invention will be described in more detail. First, for example, by a vacuum melting method, a high frequency melting method, or the like,
Preferably using a crucible or the like, under an inert gas atmosphere, after making a rare earth metal-iron-boron alloy into a melt, the melt is, for example, on a single roll, twin rolls or on a disc, etc., under the above conditions. The alloy ingot 2 for a permanent magnet having a desired crystal structure is obtained by a method using a strip casting method such as a continuous solidification, preferably under continuous solidification. That is, when solidified by a strip casting method or the like, the thickness of the alloy ingot is preferably 0.05 to 15 mm.
The easiest method is to appropriately select the casting temperature, the pouring speed, etc. so that the above range is satisfied and to perform the treatment under the above conditions.
Next, in order to inject and release hydrogen atoms into the obtained alloy ingot for permanent magnet 2 for recrystallization, for example, 1 to 1
Grind to about 0 mm square, preferably 5 to 50 hours, 90
After performing homogenization treatment at 0 to 1100 ° C., preferably in a hydrogen atmosphere at 1 atm and holding at 800 to 850 ° C. for 2 to 5 hours, and then rapidly desorbing to 10 to ² to 10 to ³ Torr. The alloy ingot for permanent magnet may be recrystallized.
The powder 1 for anisotropic permanent magnets can be obtained by, for example, a method of pulverizing to 400 μm.

The anisotropic permanent magnet powder 1 can be made into, for example, a resin magnet, a bonded magnet, etc. by a usual magnet manufacturing method.

[0017]

INDUSTRIAL APPLICABILITY The rare earth metal-iron-boron-based anisotropic permanent magnet powder of the present invention specifies crystals having a crystal grain size of 0.1 to 50 μm in the minor axis direction and 0.1 to 100 μm in the major axis direction. Content, homogenization processability, is a powder obtained by hydrogenating a rare earth metal-iron-boron-based alloy ingot for permanent magnets excellent in crystal orientation, etc., showing high anisotropy, and magnet characteristics It is extremely excellent and is useful as a raw material for permanent magnets such as resin magnets and bond magnets. Further, in the manufacturing method of the present invention,
It is possible to easily obtain the anisotropic permanent magnet powder having the excellent properties.

[0018]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0019]

Example 1 An alloy in which each metal element consisting of 14 atom% neodymium, 6 atom% boron, and 80 atom% iron was blended into a melt by an induction melting method using an alumina crucible in an argon gas atmosphere. . Then, after the temperature of the obtained melt was maintained at 1350 ° C., an alloy ingot for permanent magnet was obtained by the following method using the apparatus shown in FIG. Table 1 shows the results of structural analysis of the obtained alloy ingot.

FIG. 1 is a schematic view for producing an alloy ingot for a permanent magnet by a strip casting method using a single roll, and 1 is a crucible containing a melt melted by the high frequency melting method. . The melt 2 held at 1350 ° C. was continuously poured onto the tundish 3, and then on a roll 4 rotating at about 1 m / s, cooling conditions of a cooling rate of 500 ° C./sec and a supercooling degree of 200 ° C. So that the melt 2 is continuously solidified in the rotation direction of the roll 4.
Was dropped to produce an alloy ingot 5 having a thickness of 0.2 to 0.4 mm.

The obtained alloy ingot 5 was crushed into 5 mm square,
The homogenization treatment was performed at 1000 ° C. for 40 hours, and the area ratio of α-Fe at 5, 10, 15, 20, and 40 hours after the start of the treatment was measured by image analysis from an image by a scanning electron microscope. The results are shown in Table 2. When the crystal grain size was measured by the same scanning electron microscope, the average crystal grain size in the major axis direction after 60-hour homogenization treatment was 60 μm.

Next, the alloy ingot subjected to the homogenization treatment is placed in a vacuum heating furnace and heated at 820 ° C. for 3 hours in a hydrogen atmosphere at 1 atm.
After holding for a period of time, the mixture was degassed to 10 to ² Torr within 2 minutes, transferred to a cooling container and rapidly cooled. The alloy ingot after the treatment was taken out of the container, crushed to an average particle size of 300 μm, and a pressure of 0.5 t / cm ² was applied in a magnetic field of 15 kOe to form a green compact by uniaxial compression. The degree of crystal orientation of the green compact was measured by X-ray diffraction, the degree of orientation F was calculated according to the following equation 1, and the magnetic characteristics were measured. The crystal orientation is shown in Table 3,
The magnetic properties are shown in Table 4.

[0023]

[Equation 1]

[0024]

Comparative Example 1 The alloy melt produced in Example 1 was melted by a high frequency melting method, and a 25 mm thick alloy ingot for permanent magnet was obtained by a die casting method. The obtained alloy ingot was analyzed in the same manner as in Example 1. Table 1 shows the analysis results of the alloy ingot.

The obtained alloy ingot was homogenized in the same manner as in Example 1 and the area ratio of α-Fe was measured. The results are shown in Table 2. Further, when the crystal grain size when the homogenization treatment was performed for 10 hours was measured in the same manner as in Example 1, the average crystal grain size in the major axis direction was 220 μm.

Then, hydrogenation treatment was carried out in the same manner as in Example 1, and the powder was pulverized, and the crystal orientation degree and magnetic characteristics of the obtained powder were measured. The crystal orientation is shown in Table 3 and the magnetic properties are shown in Table 4.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[Brief description of drawings]

FIG. 1 is a schematic diagram when manufacturing an alloy ingot for a permanent magnet by the strip casting method used in Example 1.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 1/053

Claims (3)

[Claims] 1. A rare earth metal-iron-boron-based alloy ingot for permanent magnet, containing 90% by volume or more of crystals having a crystal grain size of 0.1 to 50 μm in the minor axis direction and 0.1 to 100 μm in the major axis direction. Rare earth metal-iron-boron-based anisotropic permanent magnet powder obtained by hydrogenation. 2. The rare-earth metal-iron-boron-based alloy ingot for permanent magnet has a grain size of 10 peritectic nuclei in main phase grains.
The rare earth metal-iron- according to claim 1, characterized in that α-Fe and / or γ-Fe of less than μm are finely dispersed.
Boron-based anisotropic permanent magnet powder. 3. A rare earth metal-iron-boron alloy melt is cooled at a rate of 10 to 1000 ° C./sec and a degree of supercooling is 10 to 500 ° C.
Rare earth metal produced by uniform solidification under cooling conditions of
A rare earth metal-iron-characterized in that an iron-boron-based alloy ingot for permanent magnets is subjected to hydrogenation treatment by injecting and releasing hydrogen atoms in a hydrogen atmosphere, recrystallizing, and then pulverizing.
A method for producing powder for anisotropic boron permanent magnets.