JP4150983B2 - Permanent magnet having gradient function of electrical resistivity and manufacturing method thereof - Google Patents

Description

【００４０】
【発明の効果】
この発明による磁石はＲＴＢを主成分としているため、基本的に高い磁気特性を実現でき、さらに磁化容易方向に電気抵抗率の勾配を有するので、渦電流の発生を低減できる効果を有している。また、例えばモータ等の場合、いわゆる表皮効果によって、渦電流は周波数に応じて変化することから、磁石表面側、すなわちロータとステータとの間の空隙側に近いほど渦電流が大きいため、渦電流の大きさに応じて傾斜層の厚みを変えることによって、より最適な構成、機能を付与でき、渦電流の低減が可能となる。
【００４１】
この発明による磁石は、全て母層からなるものに比較して磁気特性の若干の低下が否めないが、電気抵抗率の向上の効果により、渦電流の発生が大きいモータ、発電機用途に極めて有効である。さらに表皮効果は、モータや発電機の回転数及びサイズで変化するが、傾斜層数、傾斜層厚みを変えることにより、種々のモータ、発電機への最適なる適用が可能である。
【図面の簡単な説明】
【図１】この発明による電気抵抗率の傾斜機能を有する永久磁石の構成を示す模式図である。
【符号の説明】
１ 母層
２，３，４ 傾斜層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to improvements in permanent magnets (hereinafter referred to as RTB magnets) mainly composed of rare earths (including Y), transition metals, and boron, and the inside of the magnet is different from the conventional uniform composition, and the composition is sequentially different. The present invention relates to a new permanent magnet having an inclined structure and having an electric resistivity gradient function in the magnetization direction and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, a configuration using RTB magnets has been adopted because of the trend of miniaturization, weight reduction, high efficiency, and energy saving of motors and generators for electrical equipment. For the same reason, it is also used for electric motors and generators.
[0003]
RTB magnets tend to generate eddy currents inside the magnet because the electrical resistivity of the magnet itself is low, causing a reduction in magnetic efficiency. Therefore, in general, measures are taken to reduce eddy currents by applying an insulating film to the magnet surface after processing into a final magnet shape, such as a motor core material, for example, a silicon steel plate. .
[0004]
[Problems to be solved by the invention]
However, since the conventional insulating film insulates only the magnet surface, there is a problem that it cannot cope with the field of use, application, and use conditions.
[0005]
On the other hand, when the electrical resistivity is increased by changing the composition of the RTB magnet itself, the magnetic properties are deteriorated. Therefore, no configuration or means for increasing the electrical resistivity has been proposed by improving the RTB magnet itself.
[0006]
For example, in the case of a magnet for a motor, it is predicted that the generation of eddy current can be suppressed if the electric resistivity is high only on the gap side where the magnetic field acts. No proposal has been made regarding a RTB magnet having a function.
[0007]
SUMMARY OF THE INVENTION In view of the above-described problems related to the electrical resistivity of an RTB magnet, an object of the present invention is to provide a permanent magnet having a gradient function of electrical resistivity in the magnetization direction of the magnet and a method for manufacturing the permanent magnet.
[0008]
[Means for Solving the Problems]
As a result of various investigations for the purpose of a permanent magnet having a gradient function of an electric resistivity that is optimal as a magnet for a motor, for example, the inventors have composed of a magnet having a high electric resistivity only in a required portion on the air gap side where a magnetic field acts. , Sintering a molded body formed by stacking multiple layers of raw material powders with different compositions and particle sizes on a normal raw material powder layer for high performance RTB magnets, and orienting them in the stacking direction As a result, it has been found that a sintered RTB magnet having a desired electrical resistance value can be obtained with little decrease in the magnetic properties of the entire magnet, and the object can be achieved.
[0009]
The inventors have further studied various methods for producing a permanent magnet having a gradient function of electrical resistivity, and as a method for producing a molded body, alloy powders having different compositions and particle sizes are formed in the mold when forming the raw material powder. A method in which a plurality of layers are stacked, filled, oriented in the laminating direction and molded in a magnetic field, or a mother layer molded body of a required thickness composed of an alloy powder mainly composed of a magnet and a raw material powder for high electrical resistivity A molded body for lamination having a required thickness is prepared, and a molded body can be easily produced by a method such as laminating a plurality of layers on the mother layer or laminating both surfaces of the mother layer, and has a required gradient function. The present invention was completed by discovering that a sintered permanent magnet can be produced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Rare earth elements (including Y) R occupy 10 atomic% to 30 atomic% of the composition, but at least one of Nd, Pr, Dy, Ho, and Tb, or La, Ce, Sm, Gd, Those containing at least one of Er, Eu, Tm, Yb, Lu, and Y are preferred. In addition, one type of R is usually sufficient, but in practice, a mixture of two or more types (Misch metal, shidim, etc.) can be used for reasons of convenience. The R may not be a pure rare earth element, and may contain impurities that are inevitable in production within a commercially available range.
[0011]
R is an essential element in the above system magnet powder, and if it is less than 10 atomic%, the crystal structure has a cubic structure having the same structure as α-iron, so that high magnetic properties, particularly high coercive force cannot be obtained, and 30 atoms. If it exceeds 50%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R is preferably in the range of 10 atomic% to 30 atomic%.
[0012]
Boron B is an essential element in the above-mentioned system magnet powder. If it is less than 2 atomic%, the rhombohedral structure is the main phase, and a high coercive force (iHc) cannot be obtained. If it exceeds 28 atomic%, B-rich nonmagnetic Since the number of phases increases and the residual magnetic flux density (Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atomic% to 28 atomic%.
[0013]
A transition metal, particularly Fe, is an essential element in the above-described magnet powder, and if it is less than 65 atomic%, the residual magnetic flux density (Br) decreases, and if it exceeds 80 atomic%, a high coercive force cannot be obtained. The content is preferably from atomic percent to 80 atomic percent. Replacing part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. However, if the amount of Co substitution exceeds 20% of Fe, the magnetic characteristics are reversed. Since it deteriorates, it is not preferable. When the substitution amount of Co is 5 atom% to 15 atom% in terms of the total amount of Fe and Co, (Br) is increased as compared with the case where no substitution is performed, and thus it is preferable for obtaining a high magnetic flux density.
[0014]
In addition to the main components described above, the presence of impurities unavoidable for industrial production can be allowed. For example, C, P, S, Cu, etc., Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, At least one of W, Sb, Ge, Ga, Sn, Zr, Ni, Si, Zn, and Hf improves the coercive force of the magnet powder, the squareness of the demagnetization curve, or improves the manufacturability. It can be added because it is effective in reducing the price. In particular, it is also effective to add Co, Al, Si, Mo, Ta, and W as a small amount of additive elements in order to improve magnetic characteristics.
[0015]
For the raw materials for magnets, the required R—Fe—B alloy is melted and dissolved and pulverized after casting, the direct reduction diffusion method for obtaining powder directly by Ca reduction, and the required R—Fe—B alloy. A rapid cooling alloy method in which a ribbon foil is obtained with a melting jet caster and then pulverized and annealed, a required R-Fe-B alloy is melted, a gas atomization method in which this is pulverized and heat treated, and a required raw material metal is pulverized After that, it is obtained by various manufacturing methods such as mechanical alloying method in which fine powder is formed by mechanical alloying and heat treatment and required R-Fe-B alloy is heated in hydrogen to decompose and recrystallize (HDDR method). Isotropic and anisotropic powders can be used.
[0016]
As a method for manufacturing the RTB magnet according to the present invention, an ordinary powder sintering method is used. A feature of the magnet of the present invention is that in order to form a gradient composition, several kinds of alloy powders having different particle sizes and / or compositions are produced. For example, in the case of mold forming, each powder is magnetized in the direction of magnetization (NS The product after sintering has an inclined structure in which the electrical resistivity changes in the magnetization direction by filling the mold in layers in the direction).
[0017]
As shown in FIG. 1, for example, the inclined structure of the RTB magnet according to the present invention comprises a main layer 1 having a low electrical resistivity and inclined layers 2, 3, and 4 having a high electrical resistivity. Specifically, the density after sintering is different in each layer, or the electrical resistivity is different in each layer due to the difference in components.
[0018]
That is, the mother layer 1 which is a normal RTB magnet alloy powder part has a low electrical resistivity as in the normal product, while the graded layers 2, 3 and 4 having different particle sizes and compositions have a high electrical resistivity. it can. In order to continuously change the electrical resistivity, it is desirable to arrange the inclined layers in multiple layers. However, practically, even two or three layers can sufficiently function.
[0019]
In addition, the thickness of the inclined layer is appropriately selected from various conditions such as the application of the magnet, required characteristics, function, shape, and the number of inclined layers. For example, in the case of a certain type of motor, the actual motor Since the skin effect varies depending on the maximum number of revolutions used for the above, in other words, the frequency, it is necessary to change the thickness of the inclined layer according to these conditions. Usually, the thickness of the inclined layer is 1 mm to 15 mm, preferably 2 mm to 10 mm.
[0020]
This inclined layer is usually only on the air gap side of the magnetic circuit, in the example of the motor, only on the side where the eddy current is generated in the space between the rotor and the stator, but depending on the motor structure, it is formed on both sides of the mother layer. A so-called sandwich structure is also effective.
[0021]
In the present invention, alloy powders having different particle sizes and / or compositions include alloy powders having a large particle size with respect to the mother layer (high electrical resistivity), and alloy powders having a composition with a large amount of rare earth or boron with respect to the mother layer. (High electrical resistivity) can be applied, and these can be used in appropriate combination.
[0022]
The magnet according to the present invention enables the magnet itself to have a function of inclining electrical resistivity, so that the magnet manufacturing process can be performed without applying an insulating film to the surface of the permanent magnet used in the motor as in the prior art. It is possible to save labor of the process that can provide such a function. In addition, since a tilt function can be arbitrarily added, various tilt functions can be implemented depending on the field of use, application, and use conditions.
[0023]
【Example】
Example 1
An alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting, and ball milling was performed. Four types of pulverized alloy powders of 2.8 μm (powder a), 4.8 μm (powder b), 6.9 μm (powder c), and 12.5 μm (powder d) were produced.
[0024]
The mold for press molding is layered in the order of 20 mm of powder a as a mother layer, powder b, powder c, and powder d as slant layers in this order to a height of 2 mm each, and the total filling thickness is After the thickness was about 26 mm, a molded body was produced by press molding. Further, sintering was performed in a high purity argon atmosphere at 1100 ° C. for 3 hours, and heat treatment was performed at 580 ° C. for 3 hours to produce a sintered magnet.
[0025]
Comparative Example 1
As a comparative example, an alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting. Then, a 2.8-micron pulverized powder was produced by ball milling, filled in a press-molding die to a height of 26 mm, and press-molded to produce a compact. Further, sintering was performed in a high purity argon atmosphere at 1100 ° C. for 3 hours, and heat treatment was performed at 580 ° C. for 3 hours to obtain a sintered magnet.
[0026]
Table 1 shows the results of cutting out each layer of the sintered magnets of Example 1 and Comparative Example 1 into layers and measuring the electrical resistivity by the four-terminal method. As is apparent from Example 1, it can be seen that a dramatic improvement in electrical resistivity was achieved, although the magnetic properties were slightly reduced.
[0027]
Example 2
An alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting, and ball milling was performed. Two kinds of pulverized alloy powders of 2.8 μm (powder e) and 4.8 μm (powder f) were produced.
[0028]
In a mold for press molding, the powder e is filled to 20 mm as a mother layer and the powder f as an inclined layer is filled to a height of 2 mm, the total filling height is about 22 mm, and press molding is performed to produce a molded body. did. Further, sintering was performed in a high purity argon atmosphere at 1100 ° C. for 3 hours, and heat treatment was performed at 580 ° C. for 3 hours to obtain a sintered magnet.
[0029]
Comparative Example 2
As a comparative example, an alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting. Then, pulverized powder of 2.8 microns was prepared by ball milling, filled in a press mold to a height of 22 mm, press molded, and further sintered at 1100 ° C. for 3 hours in a high purity argon atmosphere. A sintered magnet was produced by heat treatment at 580 ° C. for 3 hours.
[0030]
As a result of cutting out each layer of the sintered magnets of Example 2 and Comparative Example 2 into layers and measuring the electrical resistivity by the four-terminal method, and the results of measuring the magnetic properties of the sintered magnets of Example 2 and Comparative Example 2 Is shown in Table 1.
[0031]
Example 3
An alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting, and ball milling was performed. Two kinds of pulverized powders of 2.8 μm (powder g) and 12.5 μm (powder h) were produced.
[0032]
Powder g is 20mm as a base layer in layers in a mold for press molding, powder h is filled to a height of 2mm as an inclined layer, after the total filling height of about 22 mm, a molded body by press molding did. Further, sintering was performed in a high purity argon atmosphere at 1100 ° C. for 3 hours, and heat treatment was performed at 580 ° C. for 3 hours to obtain a sintered magnet.
[0033]
Comparative Example 3
As a comparative example, an alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting. Then, a 2.8 μm pulverized powder was produced by ball milling, filled in a press mold to a height of 22 mm, press molded, and further sintered at 1100 ° C. for 3 hours in a high purity argon atmosphere. A sintered magnet was produced by heat treatment at 580 ° C. for 3 hours.
[0034]
Table 1 shows the results of measuring the electrical resistivity by the four-terminal method by cutting out the layers of the sintered magnets of Example 3 and Comparative Example 3 into layers, and the results of measuring the magnetic properties of Example 3 and Comparative Example 3. Show.
[0035]
Example 4
As the parent layer alloy A, composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe, graded layer alloy B The composition of 29 wt% Nd-3.5 wt% Dy-1.4 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% Ti-0.7 wt% W-balFe was dissolved in each vacuum. The pulverized powder of 2.9 μm was prepared for both the alloy A powder and the alloy B powder by ball milling.
[0036]
In a mold for press molding, the alloy A powder is filled to a height of 20 mm as a mother layer, and the alloy B powder is filled to a height of 2 mm as an inclined layer. The total filling height is about 22 mm, and then press molding is performed. Sintered in a pure argon atmosphere at 1080 ° C. for 3 hours and heat treated at 600 ° C. for 3 hours to produce a sintered magnet.
[0037]
Comparative Example 4
As a comparative example, an alloy having a composition of 28 wt% Nd-3.5 wt% Dy-1.1 wt% B-0.2 wt% Si-0.5 wt% Al-0.4 wt% W-balFe was prepared by vacuum melting. Then, a pulverized powder of 2.9 μm was prepared by ball milling, filled in a press mold at a height of 22 mm, press molded, and further sintered at 1100 ° C. for 3 hours in a high purity argon atmosphere. A sintered magnet was produced by heat treatment at 580 ° C. for 3 hours.
[0038]
Table 1 shows the results of measuring the electrical resistivity by the four-terminal method by cutting out the layers of the sintered magnets of Example 4 and Comparative Example 4 into layers, and the results of measuring the magnetic properties of Example 4 and Comparative Example 4. Show.
[0039]
[Table 1]

[0040]
【The invention's effect】
Since the magnet according to the present invention has RTB as a main component, it can basically realize high magnetic characteristics, and further has an effect of reducing the generation of eddy current because it has a gradient of electrical resistivity in the direction of easy magnetization. . For example, in the case of a motor or the like, the eddy current changes depending on the frequency due to the so-called skin effect. By changing the thickness of the gradient layer in accordance with the size of the layer, a more optimal configuration and function can be provided, and eddy current can be reduced.
[0041]
The magnet according to the present invention cannot be denied a slight decrease in magnetic properties as compared with the one composed entirely of the mother layer, but it is extremely effective for motors and generators that generate large eddy currents due to the effect of improving electrical resistivity. It is. Furthermore, the skin effect varies depending on the rotation speed and size of the motor or generator, but by changing the number of inclined layers and the thickness of the inclined layers, it can be optimally applied to various motors and generators.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a permanent magnet having an electrical resistivity gradient function according to the present invention.
[Explanation of symbols]
1 Mother layer 2, 3, 4 Inclined layer

Claims (2)

Rare earth (except including Y), the main component of a transition metal and boron, a plurality of powder layers the particle size of the same composition are made of different alloys powders in a range of 2.8 μ m ~ 12.5 μ m is laminated on the magnetization direction of the magnet A permanent magnet which is a sintered magnet that has been sintered, and has an electric resistivity gradient function in the magnetization direction. Rare earth (except including Y), the main component of a transition metal and boron, the step of particle size in the same composition to prepare a plurality of kinds of alloy powders different in the range of 2.8 μ m ~ 12.5 μ m, the plurality of kinds of alloy powder In a mold for press molding in a desired thickness in the direction of magnetization, a step of press-molding a plurality of laminated alloy powders to form a molded body, and sintering and aging treatment of the molded body A method for producing a permanent magnet having a gradient function of electrical resistivity, comprising steps .

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