JPH03141610A - Rare-earth magnet and its manufacture - Google Patents

Abstract

PURPOSE:To impart anisotropy only by heat treatment and to reduce cost by specifying the average particle diameter and the cubical percentage of recrystal lized grains of an intermetallic compound adopting a tetragonal structure in a rare-earth magnet consisting of Nd or Pr, B with specified percentage and Fe1-xCox and inevitable impurities in the remaining. CONSTITUTION:In a rare-earth magnet consisting of 12-20atom% of R (R is a rare-earth element containing at least a kind of Nd and Pr), 2-10atom% of B, and the remaining of TM [TM=Fe1-xCox(0<=x<=0.4)] and inevitable impuri ties, 50-100% of the magnet is occupied by recrystallized grains of R2Fe14B intermetallic compound which adopts a tetragonal structure with an average particle diameter of 1-100mum, and an anisotropic degree P [P={Br()-Br(rt. angle)}/{Br ()+Br(rt. angle)}] where Br() is the residual magnetic flux density in a direction of easy magnetization and Br(rt. angle) the residual flux density in the direction orthogo nal to it. Further, the workpiece is increased in density up to over 90% and heat-treated at 750-1150 deg.C.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to an RzFe, B compound (where R is Nd or P
The present invention relates to a rare earth [fff stone containing at least one type of r] as a main phase and a method for producing the same. The magnet of the present invention is expected to be widely used in various actuators such as small motors because of its high performance and low cost.

[Conventional technology]

Rare earth element R and representative transition metal elements Fe and B at 2:1
A cold ribbon having excellent magnetic properties can be obtained by ultra-quenching a molten alloy containing a ratio close to 421 by a liquid quenching method such as a single roll method (US Pat. No. 475).
6775, JP-A-5964739, JP-A-60-9852).

A flake-like thin strip with a thickness of approximately 30 strands is obtained by applying a liquid phase and cooling method using the so-called single roll method, in which molten Nd-Fe-B alloy is injected onto the surface of a rotating copper roll. . Depending on the degree of rapid cooling, the ribbon may become amorphous or
It is known that a fine crystal grain structure with a crystal grain size of 0.01 to 0.5 //I1 is formed. This quenched ribbon exhibits high coercive force when its crystal grain size is around 0.05 μm.

By hot compression molding (hot pressing) a powder obtained by pulverizing a rapidly solidified ribbon of an Nd-Fe-B alloy, it is possible to form a molded bulk in a state close to the true density of the alloy.

This is described in U.S. Patent No. 4,792,367,
Publication No. 0-10042 and the paper published by R, W, Lee 'Hot-pressed neodymium-
4ronboron magnets J (8pplied Physics Letters,
Vol.

46, N(1B, pp790-791.April
15, 1985). It is known from the prior art that a value of about 8 kG can be obtained as the residual magnetic flux density of the above-mentioned hot compression molded body.

In order to obtain higher residual magnetic flux density, it is necessary to impart anisotropy to the magnet. The R and W rules mentioned above obstruct the anisotropy method using plastic deformation. This method uses Nd-Fe-B
After the density of a compression molded body of alloy powder is increased to a density close to the true density of the alloy by hot pressing, the molded body is plastically deformed by die upsetting again.

8 to 1 depending on the degree of upsetting or alloy composition.
It has been reported that a residual magnetic flux density of 3 kG can be obtained (e.g., Y., Nozawa et al., J., Appl., P.
hys,.

Vol, 64. NO, IO, pp5285-5289
．． November 15.1988).

Although it is possible to obtain a magnet with high magnetic properties by means of applying such plastic deformation, there are disadvantages in that the manufacturing process is long and it is difficult to produce a finished magnet shape, such as cracks occurring on the surface during plastic deformation.

In the manufacturing method of anisotropic sintered magnets, a fine powder of a size smaller than a single crystal (for example, 3 μm) is obtained by pulverizing a normal alloy slab, and then the powder is oriented in a magnetic field, press-formed, and then sintered. Perform a knot. It is known that a Nd-Fe-B based sintered magnet with high magnetic properties can be obtained by this method (Japanese Patent Publication No. 34242/1983). This method has the manufacturing difficulty of handling highly active fine powders. Furthermore, since the sintering is normal pressureless sintering, there is dimensional shrinkage and deformation due to sintering, and post-processing is always required to obtain the product shape.

[Problem to be solved by the invention]

In order to manufacture rare earth magnets at low cost, there is a method that can be mass-produced and also eliminates cutting or grinding after forming, the so-called near-net type (near-net type).
5hape) molding method is desirable.

An object of the present invention is to provide a magnet having a high residual magnetic flux density by an anisotropy method using only heat treatment from a rapidly solidified Nd-Fe-B alloy powder.

[Means to solve the problem]

The present invention provides R(
However, R is a rare earth element containing at least one type of Nd or Pr), B of 2% or more and 10% or less, and the balance is TM.
(However, TM=Fe+-x Cox, (0≦x≦0.4)) and in a rare earth magnet consisting of unselectable impurities, R2Fe+ a has a tetragonal structure with an average grain size of 1 to 100n.
The recrystallized grains of the B intermetallic compound account for 50 to 100% of the rare earth magnet in terms of volume percentage, and the degree of anisotropy P (P = (
Br(‖)-BrCL)) / (Br(‖)+Br(
13) A rare earth magnet characterized in that Br (II) is the residual magnetic flux density in the direction of easy magnetization and Br (1) is the residual magnetic flux density in the direction orthogonal to the easy magnetization direction) is 0.1 or more. Further, a molded body produced by producing an alloy powder having the above composition range by a liquid quenching method, and densifying the alloy powder to 90% or more of the true density of the alloy by hot compression molding. After that, the molded body was heated to 75
The gist of the invention is a method for producing a rare earth magnet, which is characterized by heating at a temperature of 0° C. or higher and 1150° C. or lower, and then, if necessary, aging treatment at a temperature of 450° C. or higher and 750° C. or lower.

The rare earth magnet of the present invention can be manufactured with high productivity by performing hot compression molding by electrical heating under pressure.

Here, adding 5% or less of Cu in atomic percentage,
The coercive force of the magnet can be increased by setting ay to 20% or less of the total R3l, or both.

(Function) Nd-F made of microcrystals produced by liquid quenching method
The e-B alloy powder can be easily solidified in a state close to the true density of the alloy by hot compression molding at 600 to 900°C. The compact formed by solidifying this powder is almost magnetically isotropic. The present inventors have discovered that it is possible to make the molded body magnetically anisotropic by subjecting the molded body to an appropriate heat treatment and recrystallizing the microcrystalline structure.

The details of the present invention will be explained below. 77 in atomic percentage
．． The ultra-quenched powder having a composition of 5%Fe-16%Nd-5%B-1,5%Cu (hereinafter referred to as Nd+aF'ett, 5B5cu+, s) can be easily molded and solidified by electrical heating under pressure. The demagnetization curve of the compact was measured in the pressing direction (11) and in the direction (1) perpendicular to the pressing direction, and the results are shown in FIG. 1(a). As can be seen from the figure, the difference in residual magnetic flux density in both directions is small and almost isotropic. When this molded body is heated to 1000°C to cause recrystallization, the molded body exhibits strong magnetic anisotropy, and the first
A magnetic curve ‖i as shown in Fig. 7 is obtained.

In this case, a high residual magnetic flux density of 9.16 kG was obtained in the pressurizing direction. The coercive force of the compact decreases due to recrystallization heat treatment, but increases to a certain extent by subsequent aging treatment at <600°C (see Figure 1 (C)).
. Changes in the demagnetization curve of the compact due to such heat treatment are as follows:
Nd-Fe-83 element system, Cu added Nd-Fe-B-Cu
4-element system, Dy-added Nd-Dy-Fe-84-element system, Cu
It is observed in any of the Nd-Dy-Fe-B-Cu five-element systems with composite addition of and Dy. However, Cu and/or D
Addition of y has a remarkable effect on improving the coercive force of the anisotropic molded body.

As a parameter representing the degree of anisotropy of a magnet, the degree of anisotropy P is defined as follows.

P= (Br(‖) Br(⊥)) / (Br(‖
)+ (BrCIJ) Here, Br((‖) is the residual magnetic flux density in the pressing direction, and Br(11 is the residual magnetic flux density in the direction perpendicular to the pressing direction.

When P=O, it is completely isotropic, and when P=quantity, it is completely anisotropic. In the case of FIG. 1(a) immediately after molding, P=0
．． 04, 0.37 in the case of FIG. 1(b) after the recrystallization heat treatment, and 0.37 in the case of FIG. 1(C) after the aging treatment.
It is 35. A degree of anisotropy of P = 0.1 or more can be easily achieved by subjecting the hot compression molded body to recrystallization heat treatment.

The above recrystallization is noticeable when the molded body is heated to a temperature of 750° C. or higher, although it varies depending on the components. Figure 2 shows the changes in residual magnetic flux density and coercive force when the temperature of the compact was raised from 700°C to high temperature. In this example, 80
The difference between B r (l l) and Br (1) begins to widen at 0° C., and the difference becomes even larger at higher temperatures. The effect is 1
It reaches saturation at around 000°C and persists up to the melting point of 1150°C or lower. In Figure 3 (a) (Ndo, qDyo, +)
Figures 3 (1) and (C) show photographs of the structure of the powder containing the components of +6FetJ6 immediately after hot compression molding.
The microstructure photographs are shown when each sample was held at 0°C and 1000"C for 10ml. As observed in Figure 3(b), large recrystallized grains of 1 to 100μm were formed from the flaky powder. The recrystallized grains are a tetragonal R2Fe14B intermetallic compound that has the same crystal structure as the fine crystal grains that exist before heat treatment.The easy axis of magnetization of these recrystallized grains preferentially points in the pressing direction, so that they do not form in the compact. Anisotropy is induced (see the X-ray diffraction results in Figure 8).In order to obtain a magnet with sufficiently high anisotropy, an average particle size of 1 to 1OOp [I
It is necessary that the positive recrystallized grains occupy 50 to 100% of the compact by volume.

This volume percentage can be determined by measuring the area percentage occupied by recrystallized grains on a photograph of the recrystallized structure taken by an optical microscope as shown in FIG. 3(C), and easily converting it from that value.

This recrystallization heat treatment is desirably performed for 1 minute or more and 1000 minutes or less, and a long time heat treatment exceeding 1000 minutes cannot be expected to improve the anisotropy.

Although the coercive force decreases due to the recrystallization heat treatment, this is recovered to some extent by the subsequent aging treatment. As shown in FIG. 4, a sufficiently high coercive force can be obtained by aging treatment at 450 to 750° C. after recrystallization heat treatment, especially in the case of a component system to which Cu is added.

In particular, aging treatment at 500 to 700°C is desirable, and a treatment time of 1 minute or more and 100 minutes or less is sufficient.

The reasons for limiting the components of the present invention are as follows.

Although the composition of the rare earth element R is not particularly limited, it is desirable that at least 60% of the total R be Nd and/or Pr in order to obtain a magnet with high characteristics. The main feature of the present invention is anisotropy by heat treatment, but in order to obtain a magnet with high characteristics through the anisotropy treatment, the amount of R must be 12% in atomic percentage.
The above must be 20% or less. If the amount of R is less than 12%, a sufficient coercive force cannot be obtained, and if the amount of R exceeds 20%, the decrease in residual magnetic flux density cannot be ignored. In order to improve the coercive force, it is effective to make a portion of the above-mentioned R Dy within a range not exceeding 20% of the total R amount. If the proportion of Dy in R exceeds 20%, the decrease in residual magnetic flux density cannot be ignored.

In the magnet that has undergone the anisotropy treatment by the heat treatment of the present invention, the addition of Cu is extremely effective in improving the coercive force.

In order to improve the coercive force, it is effective to add Cu in an amount not exceeding 5% in atomic percentage. Added amount of Cu is 5%
If the value exceeds 1, the degree of anisotropy caused by the recrystallization heat treatment decreases, and the decrease in residual magnetic flux density cannot be ignored. In order to minimize the decrease in the residual magnetic flux density and improve the coercive force, it is effective to add Dy and Cu in combination within the above effective composition range.

If the amount of B is less than 2% in atomic percentage, RzFe+□
A large amount of Br1ch phase appears, and when it exceeds 10%, a large amount of Br1ch phase appears. Either phase inhibits densification of the powder by hot compression. Therefore, the amount of B is 2% or more and 10%
Limited to:

In order to raise the Curie temperature of the alloy and reduce the temperature change in magnetic flux density at the operating temperature, a portion of Fe may be replaced with Co. Also in the magnet of the present invention, Co accounts for 40% or less of the total transition metal elements (i.e., TM=Fe+-x COX (0≦x≦0.4)
)Is possible. When the Go substitution amount exceeds 40%, the coercive force decreases.

The alloy powder having the limited components as described above is produced by a liquid quenching method. The liquid quenching method will be explained below. first,
An alloy having the above components is melted and a ribbon is produced by a conventional single roll method. Alternatively, other twin roll methods or gas atomization methods may be used. In the case of a single roll method, the thickness is 20 to 30 pm, the width is 1.5 to 2 mm, and the length is 1
0-20 M flake-like ribbons are obtained: The magnetic properties of the single-roll quenched ribbons vary depending on the degree of quenching, which is controlled by the rotational speed of the roll. Under optimal quenching conditions, a ribbon consisting of fine crystal grains with a size of 0.01 to 0.1 μm is obtained, and the ribbon exhibits excellent magnetic properties. On the other hand, under superquenching conditions, a nearly amorphous ribbon is obtained, but the ribbon is crystallized by heat treatment and exhibits high magnetic properties. Both ribbons are ground into alloy powder. The particle size of the powder is 10 to 500 μm.
is suitable. When the powder particle size is less than 10 μm, not only the powder is easily oxidized, but also the degree of anisotropy caused by heat treatment is low (see Example 5). In addition, the particle size is 500μ
If it exceeds m, it becomes difficult to fill the cavity of the die with powder during hot compression molding.

Hot compression molding is performed at a temperature range of 500 to 900°C under a pressure of 0.1 to 5 ton/cJ.

This is easily done in a conventional hot press using high frequency induction heating. In addition, in order to increase productivity, an electric sintering machine is used to rapidly heat the powder by electric heating under pressure, making it possible to complete the desired hot forming in a short time (1 to 5 minutes). .

Electric heating is extremely fast and highly productive.

Recrystallization heat treatment of the molded body is carried out at an optimal temperature of 750°C or higher, but the heating rate to reach that temperature is usually 0.1 to 1
00° (:/min, and the holding time at that temperature is 1
The duration is not less than 1000 minutes. In addition, aging treatment to increase coercive force is performed at an optimal temperature of 450°C or higher, the heating rate to that temperature is usually 1 to 100°C/min, and the holding time at that temperature is 1 minute or more. It is 100 minutes or less. The above two types of heat treatments are performed in a normal heat treatment furnace in vacuum or in an inert gas atmosphere such as Ar. Due to these heat treatments, there is almost no dimensional change in the molded product,
There is almost no need for post-processing such as polishing to ensure the product shape of the magnet.

〔Example〕

Example 1 77.5%Fe-16%Nd-5%B1 in atomic percentage
．． 5%Cu (Nd+6Fet7.5BsCu+,s
) is melted by high-frequency induction heating, and the diameter ‖
The molten metal was injected from a quartz nozzle with one hole onto the surface of a rotating copper roll. The surface speed of the roll at this time was 25 m/sec, which is the optimum rapid cooling condition for obtaining fine crystal grains. The thickness of the obtained ribbon is 20-30
μm, width is approximately 1.5 mm, and length is 10-20 mm. This ribbon was pulverized to 355 μm or less.

The powder obtained by the above procedure was hot compression molded using an electric current sintering machine. In this experiment, the powder was loaded into the cavity of a carbon die, and the powder was loaded at 400 kg/cm.
The powder was heated by applying a current of 1500 A while applying a pressure of +fl. Here, the cavity has a cylindrical shape with a diameter of 20M. Under the above pressure, the actual temperature of the sample was approximately 8
When the temperature reached 00°C, the density of the powder reached 7.5 g/ca, which is close to the true density of the alloy. The time required from the start of heating to the end of sintering was 2 to 3 minutes. The obtained compact was heat-treated and subjected to pulse magnetization of 5 QkOe, and then its magnetic properties were measured using a self-recording magnetometer.

FIG. 1(a) shows a demagnetization curve of an untreated molded product after hot compression molding. As a recrystallization heat treatment, after rapidly heating the molded body to 600°C (the heating rate here does not have much effect on the properties), it is heated at 0.5°C/m from 600°C to 1000'c.
A heat treatment was performed in which the temperature was raised at in and maintained at that temperature for 10w1n. The demagnetization curve of the molded body subjected to this heat treatment is shown in FIG. 1(b). Figure 1 (C) shows 6
The demagnetization curve of a molded article subjected to aging treatment at 00° C. for 10 ml is shown. In each case, demagnetization curves in the pressing direction (11) and in the direction (1) perpendicular to the pressing direction are shown. In the case of Fig. 1(a), the degree of anisotropy P = 0.04, in the case of Fig. 1(b) after recrystallization heat treatment, P = 0.37, and the degree of anisotropy after aging treatment is P = 0.04. In the case of Figure 1 (C), P=0.35. The magnetic properties in the pressing direction are Br-9,
16kG + s Hc = 9, 0 koe, (B
H) max=17.6 MGOe.

Example 2 Changes in magnetic properties due to heat treatment temperature were measured.

In the alloy composition, 10% of Nd was replaced with Dy (Ndo,
qD'! o, l)+6Pe14B6 and (Ndo, 9
D3'O,IL bF(3qq, 5BSCLI+,
It is 5.

According to the manufacturing method described in Example 1, a superzoon of the above composition,
A cold powder was produced and a hot compression molded body was produced.

These molded bodies were subjected to heat treatment for 10 ml at each temperature from 700°C to 1100°C. Here, the temperature of each sample was raised stepwise, and after heat treatment at each temperature, the magnetic properties were measured at room temperature. Note that the rate of temperature increase to each temperature is 60° (:/min).

FIG. 2 shows the residual magnetic flux density Br (|) in the pressing direction, the residual magnetic flux density Br (1) in the direction perpendicular to the pressing direction, and the coercive force iHc measured in the pressing direction. As can be seen from the figure, the difference between B r (l l) and Br (1) begins to widen from so o 'c, and the difference becomes larger at higher temperatures, indicating that a large anisotropy is induced by this heat treatment. There is.

The degree of anisotropy P is 0.04 to 0.05 before heat treatment, and is 8
It becomes 0.1 or more at 50℃ or higher, and the maximum is 0.20 to 0.2.
Reach 1. The coercive force decreases rapidly at a temperature of 800 to 850°C, but takes a relatively constant value of 10 to 14 kOe at higher temperatures.

In Figure 3, (Ndo, JVo, +) + hFeteB
A photograph of the cross-sectional structure including the pressing direction, which was obtained by etching the hot compression molded product having the composition No. 6 and observing it with an optical microscope, is shown.

Figure 3 (a) shows the untreated product after hot compression molding, (b) shows the product heat-treated at 800°C for 10 m1n, and (C
) was heat treated at 1000°C for 10ml. As can be seen from Figure 3(b), new crystal grains of R, Fe, and 4B with distinct habit planes from inside the ribbon-shaped powder (recrystallized grains, a typical example is shown by X in the photo) has appeared. At 1000° C. in FIG. 3(C), most of the compact is occupied by recrystallized grains. Magnetic anisotropy occurs because the axis of easy magnetization of these recrystallized grains tends to be oriented in the direction of pressure.

Ru.

lQ at 1000℃ for hot compression molded bodies of the above two compositions.
After being subjected to recrystallization heat treatment for 400 min, it was rapidly cooled and
Aging treatment was performed stepwise for 10 sins at each temperature from "C to 800 °C.The magnetic properties after aging at each temperature were measured at room temperature, and the coercive force (iHc) in the pressing direction is shown in Figure 4. .

In the component system containing Cu, the aging temperature is 500 to 700.
The coercive force increases significantly at ℃.

Example 3 The influence of heating rate in recrystallization heat treatment was investigated. The composition of the alloy used was 10% of Nd replaced with Dy (Ndo
, qDVo, +) IbFet-t, 5Bscu
+, s. An ultra-quenched powder having the above composition was produced based on the manufacturing method described in Example 1, and hot compression molded under the same conditions as in Example 1. The molded body is heated at 0.5 to 60°C/min.
The sample was heated up to 1000° C. at various heating rates in the range of 1000° C., held at that temperature for 10 ml, and then rapidly cooled. After quenching, the magnetic properties were measured at room temperature.

FIG. 5 shows the values of residual magnetic flux density Br(It) and Br(1) with respect to the heating rate. From the figure, the slower the heating rate, the B
It can be seen that the difference between r(11) and Br(1) widens, and the degree of anisotropy increases.

Example 4 Compositions Nd16FetsBa and Nd with different Cu contents
+bFe7q−xBscux (x=1.5.3.0.
4.5.6.0) was produced, and subjected to recrystallization heat treatment and aging treatment under the same conditions as detailed in Example 1.

FIG. 6 shows the magnetic properties of the molded body subjected to the aging treatment with respect to the Cu content. As you can see from the figure, 1.5 to 4.
Coercive force is improved by adding 5% Cu.

Addition of up to 6% Cu not only reduces the absolute value of the residual magnetic flux density, but also reduces the degree of anisotropy. The degree of anisotropy P is 0, 1.5, 3.0, 4.5°6, O
%Cu alloy, respectively 0.39 and 0.35゜0
．． It was 25.0.15.0.06.

Example 5 5% of Nd was replaced with Dy (Ndo, qsDyo,
. , ) 1°Fe77,5Bscu+,s The effect of recrystallization heat treatment was investigated. Based on the manufacturing method described in Example 1, super 2. A cold ribbon was produced and the ribbon was pulverized to prepare a powder having an average particle size of 200 μm.

Here, for comparison, further fine pulverization was performed to obtain a particle size of 5n.
A powder was also prepared. These powders were hot compression molded under the same conditions as in Example 1, and subjected to the same recrystallization heat treatment and aging treatment as detailed in Example 1.

FIG. 7 shows the demagnetization curve in the pressing direction (11) and the direction (1) perpendicular to the pressing direction. It can be seen that when the particle size is 200 μm, there is a large anisotropy, and when the particle size is 5-μm, the degree of anisotropy is small.

FIG. 8 shows the intensity profile of X-ray diffraction obtained when X-rays (CuKα) are incident on a plane perpendicular to the pressing direction for the case of the molded body having a particle size of 20 on. Figure 8 (
FIG. 8(a) is before the recrystallization heat treatment, and FIG. 8(b) is after the recrystallization heat treatment. Almost all peaks in both profiles are indexed as diffraction lines coming from the tetragonal R2Fe+J intermetallic compound. Furthermore, it is confirmed that the peak of 006 reflection becomes significantly stronger after the heat treatment compared to before the heat treatment. This indicates that the proportion of the easy axis of magnetization (C axis) oriented in the pressing direction was increased by the recrystallization heat treatment. That is, this proves that anisotropy was induced by the recrystallization heat treatment.

Example 6 Hot compression molded bodies made of ultra-quenched powders of various compositions were prepared and subjected to recrystallization heat treatment and aging treatment under the same conditions as detailed in Example 1. Table 1 shows the alloy composition and the magnetic properties (iHc, Br(‖), Br(1), degree of anisotropy P) after aging treatment. It can be seen from the table that anisotropy is induced by recrystallization heat treatment in Co-containing alloys and alloys using Pr as the rare earth element.

〔Effect of the invention〕

The characteristics of the anisotropic rare earth magnet of the present invention are the button-G of vertical magnetic field forming.
o Comparable to the characteristics of sintered magnets. In the case of the present invention, inexpensive Nd is mainly used as the rare earth material, and anisotropy is achieved only by heat treatment, so it is possible to provide a low-cost magnet. There is almost no change in the shape of the magnet due to the anisotropy heat treatment, and the shape of the magnet becomes close to the shape of the cavity of the die used in hot compression molding. As a result, Nd-Fe-
It can also be advantageous in terms of cost compared to B (i-stone).

[Brief explanation of the drawing]

Figure 1 is a diagram showing the change in the demagnetization curve of the residual magnetic flux density Br (l It) in the pressing direction and the residual magnetic flux density Br (1) in the direction perpendicular to the pressing direction of the compact after hot compression molding. (a) shows the untreated Q demagnetization curve after hot compression molding, (b) shows the demagnetization curve after recrystallization heat treatment, and (C) shows the demagnetization curve after aging treatment. 3 shows the change in magnetic properties with respect to heat treatment temperature. FIG. 3 is an optical micrograph showing the cross-sectional structure of the molded product after hot compression molding, and (a) shows the microstructure after hot compression molding and untreated microstructure; (b) shows the microstructure after heat treatment at 800°C, and (C) shows the microstructure after heat treatment at 1000°C. Figure 4 shows the change in coercive force with aging temperature. Figure 5 shows the recrystallization 1000" in heat treatment
The change in residual magnetic flux density with respect to the heating rate up to C is shown. FIG. 6 shows the dependence of magnetic properties on added Cul. FIG. 7 shows demagnetization curves after recrystallization heat treatment and aging treatment for powders of different sizes. FIG. 8 is a diagram showing the intensity profile of X-ray diffraction of the molded body, (a) shows the X-ray diffraction profile before recrystallization heat treatment, and (b) shows the X-ray diffraction profile after recrystallization heat treatment. shows. 4πI (C) Fig. 3 Fig. 2 Tl ('c) Kabuto 1 lamp 1 Rino 4 degrees, TfC'') Fig. 4 Tz (C) Aging temperature, TzCc) Fig. 5 °C/min ) H (kOe) Figure 6 u (αtZ) Figure 8 ((1) Procedural amendment (voluntary) March 1, 1990

Claims (9)

[Claims] (1) R in an atomic percentage of 12% or more and 20% or less (R is a rare earth element containing at least one of Nd or Pr), B is 2% or more and 10% or less, and the balance is TM (however, TM= Fe_1_−_xCo_x, (0≦x≦0.
4)) In rare earth magnets consisting of unavoidable impurities, R has a tetragonal structure with an average grain size of 1 to 100 μm.
The recrystallized grains of the _2Fe_1_4B intermetallic compound account for 50 to 100% of the rare earth magnet in terms of volume percentage, and the degree of anisotropy of the magnet is P (P = (Br (‖) - Br (⊥) / (Br (‖)) +B
A rare earth magnet characterized in that r (⊥), where Br (‖) is the residual magnetic flux density in the direction of easy magnetization, and Br (⊥) is the residual magnetic flux density in the direction orthogonal to the easy magnetization direction) is 0.1 or more. . (2) The rare earth magnet according to claim 1, wherein Cu is added in an amount of 5% or less by atomic percentage. (3) The rare earth magnet according to claim 1, wherein 20% or less of the total R amount is Dy. (4) Addition of 5% or less Cu in atomic percentage and total R
2. The rare earth magnet according to claim 1, wherein 20% or less of the amount is Dy. (5) R in an atomic percentage of 12% or more and 20% or less (R is a rare earth element containing at least one of Nd or Pr), B is 2% or more and 10% or less, and the balance is TM (however, TH= Fe_1_−_xCo_x, (0≦x≦0.
After producing an alloy powder consisting of 4)) and unavoidable impurities by a liquid quenching method, and obtaining a compact with a high density of 90% or more of the true density of the alloy by hot compression molding from the alloy powder, The molded body is heated at a temperature of 750°C or more and 1150°C or less, and then heated at a temperature of 450°C or more and 7
A method for producing a rare earth magnet, characterized by aging treatment at a temperature of 50°C or lower. (6) The method for producing a rare earth magnet according to claim 5, characterized in that Cu is added in an atomic percentage of 5% or less. (7) The method for producing a rare earth magnet according to claim 5, wherein Dy accounts for 20% or less of the total R amount. (8) Addition of 5% or less Cu in atomic percentage and total R
6. The method for producing a rare earth magnet according to claim 5, wherein 20% or less of the amount is Dy. (9) The method for producing a rare earth magnet according to claim 5, 6, 7 or 8, wherein the hot compression molding is carried out by electrical heating under pressure.