JPH0410504A - Heat treatment method for rare-earth permanent magnet - Google Patents

Abstract

PURPOSE:To integrally manufacture a large-sized permanent magnet of 200g or more in weight without generation of cracks and chippings by a method wherein a reheating operation is conducted on the sintered body to the temperature lower by 300 deg.C from the sintering temperature, and after this state has been maintained for 10 minutes or longer, the sintered body is cooled down to the temperature which is lower by 500 deg.C or less from the sintering temperature at the cooling rate of 0.03 to 3 deg.C/min., and after it has been maintained for one hour or longer, it is gradually cooled down to about 400 deg.C or lower at the average cooling rate of 5 to 50 deg.C/min. CONSTITUTION:A sintered magnet body is cooled down to the desired low temperature which is lower by 300 deg.C than the sintering temperature, and after it has been maintained at that temperature for a specific period, the sintered magnet body is cooled down in a furnace under a protective atmosphere. The sintered body is maintained at the above-mentioned temperature for one hour or longer, desirably four hours or longer at the point of time when the sintered body is cooled down to about 500 deg.C or longer from the sintering temperature. Subsequently, it is taken out under protective atmosphere and placed in a stationary state until it is cooled down to about 300 deg.C or lower at the average cooling speed of 5 to 50 deg.C/min.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing SmCo5 anisotropic rare earth permanent magnets, and more specifically, to accelerator-related members such as wigglers and undulators, VCMs and Anisotropic Sm including large-sized ones used in drive sources such as linear actuators, electrical components for automobiles and aircraft, rotating machines for computers and OA-related equipment, and audio equipment such as speakers.
This relates to a method of manufacturing a CoB permanent magnet.

[Conventional technology]

Since Sm-Co based anisotropic rare earth permanent magnets were announced, their magnetic properties have improved year by year along with advances in physical property research, and Nd-Fe-B based permanent magnets have been announced in recent years. In addition to contributing to the miniaturization and higher performance of equipment and devices to which they are applied, they are also contributing to the development of new fields. When manufacturing this anisotropic rare earth permanent magnet, powder metallurgy is usually used. Taking a SmCo5 type rare earth cobalt magnet as an example, first, the stoichiometric composition of Sm
An alloy consisting of 33.79% by weight Co, 66.21% by weight S and 34% by weight the balance Co is high-frequency melted in, for example, an Ar atmosphere, and the ingot obtained through casting means is cast in a ball mill in a protected atmosphere. , finely pulverize by means such as a vibrating mill. The fine powder of several μm thus obtained is formed under pressure using a mold placed in a magnetic field, and this compact is sintered in a protective atmosphere at 1100° C. or higher. Next, the sintered body is coated with 5 solid state
Communications, 8 pp139-
141 (1970). Heat treatment is generally carried out at the sintering temperature or at a low temperature within approximately 300°C below the sintering temperature for a certain period of time, followed by furnace cooling to a temperature within approximately 500°C below the sintering temperature. , it is necessary to perform rapid cooling to approximately 300°C or less.S
In mCos rare earth permanent magnets, if the quenching treatment is not performed, the coercive force iHc decreases significantly due to the so-called West tendorp effect, as specified in the above academic paper, which is a feature of SmCo5 magnets. This makes it difficult to put this into practical use as a permanent magnet with a high coercive force.

Therefore, for heat treatment of SmCo5 magnets, quenching in oil, fluidized bed quenching, blast quenching with gas, and for extremely small magnets, quenching treatments such as water cooling can be used.
Permanent magnets with high coercive force have been obtained by avoiding the reduction in iHC due to magnetic defects. However, on the other hand, the SmCo-based permanent magnet has a magnetization of 6.6 x 10-'/''C with respect to the C-axis direction of the crystal grains constituting it, and 12.6 x 10-'/''C with respect to the direction perpendicular to the C-axis. Since it has a coefficient of thermal expansion of 6/''C, if there is a significant temperature difference between the inside and the surface of the permanent magnet during rapid cooling, tensile stress will be induced on the surface of the magnet, which is cooled quickly. Cracks and cracks occur in the magnet. Therefore, in order to obtain a magnet that does not generate cracks, there are restrictions on size and shape, and large S
In order to obtain an mCO5-based magnet, it was necessary to join a plurality of small magnet pieces together by means such as adhesion.

[Problem to be solved by the invention]

As mentioned above, SmCos-based anisotropic rare earth cobalt magnets are mostly produced by powder metallurgy, and due to the high magnetic properties of this type of permanent magnet, the per unit volume of permanent magnet Since the amount of magnetic flux is large, there has been an attempt to make permanent magnets as small as possible when used in conventional audio equipment, automotive electrical components, computers, and OA-related parts.

However, in recent years, there has been a gradual increase in demand for large rare earth magnets, including accelerator-related parts such as wigglers, undulators, high vacuum pumps, and drive sources such as servo motors.

In particular, SmCo5 permanent magnets have a large coercive force and a high Curie point of 710°C (and have excellent heat resistance and corrosion resistance, so they are used especially in automobiles and other applications where excellent thermal stability is essential. Large, integrated SmCo5 permanent magnets are required in the fields of aircraft electrical components and accelerators.

In order to meet these demands, 10XIOXIO120x20x20.25X25
Cubic sintered bodies with dimensions of x25 x 30 x 30 mm (= indicates the anisotropic direction) were prepared, heat treated by quenching in oil, and the presence or absence of cracks was confirmed. The number of samples for each dimension was 10, but 20x20
There was no cracking in samples smaller than x20■, but
In the sample of 25×25×25 embryos, cracks occurred in 2 out of 10 embryos, and in all samples of 30×30×3 orRrn, cracks occurred.

From the above study results, it is possible to create a single large S without using adhesive.
In order to produce mCO516 stone, conventional West
It has become clear that the current composition, which has a pronounced endorp effect, cannot be manufactured. Therefore, the problem that must be solved is only by searching for a compositional region where the reaction rate is relatively slow and establishing heat treatment conditions that match the compositional region, even if the West tendorp effect exists. Since it is possible to provide a large integrated SmCo5 magnet, the objective is to find out the composition range and heat treatment conditions for these magnets.

In particular, in order to apply SmCo5-based magnets to the above-mentioned fields, heat treatment conditions including slow cooling treatment to a degree that makes coercive force iHc appear at 130,000 c or more, more preferably 150,000 c or more and prevent the occurrence of cracks are required. The most important issue to be solved is to establish a target composition range.

[Means for Solving the Problem] The problem to be solved in the present invention is the above-mentioned West
The object of the present invention is to provide a method for heat treating a large 5III CO8 magnet that suppresses the endorp effect and has a large coercive force under conditions of a relatively slow cooling rate.

In order to solve the problems existing in the above-mentioned prior art, the composition region is at least one kind of rare earth element represented by R and CO or CO and pe, Ni represented by M.

From the combination of at least one type of element in the Cu group, RMs
and R.J.? In a sintered product consisting of R and M having a composition such that a phase is generated in the sintered product, a proportion of M is selected in the range of 63 to 65% by weight in parts by weight, and the proportion of M is reduced within this composition range. In order to ensure strength against magnetic fields, the above i
Hc is 130,000c or more, preferably 150,000
In addition to the above conditions, when bHc is the coercive force on the B-H curve of the magnetic properties after sintering and heat treatment, the second
In a method for producing rare earth magnets in which the absolute value of the coercive force at the inflection point on the 4πI-H curve in the quadrant is greater than the absolute value of 1.3 × bHc, After re-heating to a temperature of 0.03 to 500°C and holding at that temperature for 10 minutes or more, cooling the furnace to a low temperature of 0.03 to 500°C and holding at that temperature for 1 hour or more, Average cooling rate 5~50° (/
It is characterized in that it is slowly cooled to approximately 400°C or less at +++in. In addition, the ratio of M is 63 to 65% by weight
When heat-treating a sintered product having a composition within the range of by the method described above, the furnace was cooled to a temperature within 500°C below the sintering temperature and maintained at that temperature for 1 hour or more. After that, it is characterized by rapid cooling by a method such as oil cooling, fluidized bed cooling, or blast cooling.

The permanent magnet having the above-mentioned composition range obtained by the heat treatment method of the present invention has an excellent feature that it can be particularly applied to large-sized magnets weighing 200 g or more and can be manufactured in one piece without cracking or cracking.

In addition, as a means for manufacturing a magnet having the above composition and shape, raw material powder having an M ratio in the range of 63 to 65% by weight is passed through a mold provided to impart anisotropy to the outside. It is characterized in that it is press-molded in a direction parallel or perpendicular to a magnetic field to form an integral square, disk-shaped, ring-shaped or cylindrical molded body.

Depending on the application, it may also be press-formed in a direction perpendicular to the direction of a parallel external magnetic field passing through a mold provided to impart anisotropy to form an integral rectangular parallelepiped or plate-shaped molded product. In the subsequent steps, it may be processed into a disk shape, a ring shape, or a cylindrical shape.

In the heat treatment method of the present invention, the ratio of M is 63 to 65 wt.
The reason for limiting it to % is as follows. That is, the magnet of the present invention exists in a phase ranging from a single solid phase of RM5 intermetallic compound to a second RM, which is a solid with a higher R content than RMS, at the sintering temperature. From this state, in the aging treatment or heat treatment of the present invention to be described later, a second phase, which becomes RzMt, precipitates from the solid solution phase in a direction that increases the coercive force 1) 1c of RM. FIG. 1 is a phase diagram of the Sm-Co system, and as is clear from this diagram, in order to cause precipitation by the heat treatment of the present invention from a solid solution phase represented by the SmCo phase at the sintering temperature, , its composition must be close to the R-side boundary line that defines the RMS intermetallic compound phase region. In the composition of the boundary line close to the R side, by applying the heat treatment method of the present invention, the influence of the West tendorp effect is reduced, and even with gradual cooling treatment, the influence of the West tendorp effect is reduced.
Hc can be made to appear. However, during heat treatment, if there are too many precipitated phases, the ratio of the 115 phase responsible for ferromagnetism decreases, so even if iHc is large, the residual magnetic flux density Br decreases, so the amount of precipitated phases must be controlled to a preferable level. This is the reason why the ratio of M is limited to the above range.

Next, the heat treatment conditions used in the present invention will be described in detail.

In the conventional technology, as mentioned above, the temperature is 500°C higher than the sintering temperature.
Usually, the furnace is cooled to a low temperature within 100 mL, and the quenching process is performed immediately when the quenching start temperature is reached. In the heat treatment method of the present invention, the magnet sintered body is brought to a desired low temperature within about 300°C below the sintering temperature, held for a certain period of time, and then heated at a very gentle rate of about 0.0 to 3°C/min. Furnace cooling is performed in a protective atmosphere at a cooling rate to a temperature within approximately 500°C below the sintering temperature. Once the temperature reaches a temperature approximately 500°C lower than the sintering temperature, the temperature is maintained for at least 1 hour, preferably for at least 4 hours. Thereafter, it was taken out under a protective atmosphere and left to stand until the temperature reached approximately 300°C or less. By this heat treatment method, 10
00 g or more in the form of an angular, disc, ring or cylindrical RM, without cracking, and in addition, the absolute value of the inflection point on the 4π1-H curve in the second quadrant is 1. .3 × bHc.

Of course, small-sized magnets have the same magnetic properties as described above even if they are subjected to quenching treatment such as quenching in oil after being held for at least 1 hour, more preferably at least 4 hours, as in the prior art. Permanent magnets can be obtained.

However, the heat treatment of the present invention obtains favorable results for the composition range of the present invention, and the conventional CO amount is 6.
It should be noted that when this heat treatment is applied to a 5.8 to 66.0% by weight 5IIICo5 magnet, the residual magnetic flux density Br is significantly reduced.

Next, in the heat treatment method of the present invention, when the coercive force on the B-H curve is bHc, the absolute value of the coercive force at the inflection point on the 4πI-H curve in the second quadrant is 1.3 × bHc. We will explain in detail the reason why it is stipulated that the

Drive sources such as automobile rotating machines are all used under demagnetized field conditions, such as wigglers, undulators, and MRs.
Even when using applications such as I, an assembly process is essential to construct a magnetic circuit, but when magnets are sequentially incorporated, the assembly process is affected by the magnetic field from the magnets that have already been incorporated into the circuit. There was a problem in that some magnets were demagnetized and as a result, the required amount of magnetic flux could not be secured. FIG. 2 is a diagram showing the undulator in the middle of being assembled. In the figure, ■ indicates a magnetic pole such as permenda or permendur, and ■ and ■ indicate a permanent magnet. Further, the electron beam is incident from the direction (2), and generates synchrotron radiation by meandering through the undurator, but the undulator magnet is required to have severe demagnetization resistance. Third
The figure schematically shows a method of assembling the undulator shown in FIG. 2. In the figure, ■ indicates a state in the middle of assembly, and ■ indicates a magnetic pole such as permender or permendur. ■ indicates the permanent magnet #l that is being assembled, and ■ is the symmetry reference plane. Figure 4 shows the result of resimulating on a computer the state of the flow of magnetic flux lines that occurs between magnet #1 and the nearest adjacent magnet #2 and the second adjacent magnet during the assembly process shown in Figure 3. . Note that FIG. 3 shows only the area above the center line (■). As is clear from the figure, it can be seen that a large demagnetizing field acts on the second adjacent magnet #3 (indicated by a dotted line in the figure) having the same polarity as the magnet #1 that is currently being assembled.

The maximum value of this demagnetizing field (reverse magnetic field) is plotted against the distance from the final installation position with ■ as the origin.
It is a diagram. In the figure, ■, ■, and [phase] are #1, respectively. #2
and #3 magnet are shown. The Br of the permanent magnet at this time is 9
000G, and from Figure 5, the maximum demagnetizing field is 2
I love that it is 5000e.

Considering the permeance of the magnet from these relationships, the demagnetization resistance required for the coercive force bHc on the B-H curve of the magnet is 1.2 × bHc, preferably 1.3 × b
If Hc is calculated and the position of the inflection point (shoulder) of the 4πI-H curve is 1.3×bHc or more, a permanent magnet can be obtained that can be used sufficiently for drive sources other than wigglers and undulators. I can do it.

The present invention will be specifically explained below using Examples.

Example I A permanent magnet alloy consisting of a Co amount of 62.50 to 65.80% by weight, a weight interval of 0.25 to 0.30% by weight, and the balance Sm was produced by high frequency melting in an argon atmosphere, Cast into ingots. The obtained ingot was coarsely crushed to about 30 meshes using a Joe crusher, and finely crushed to an average particle diameter of about 5 μm using a jet mill using N2 gas as a fluid. Particle size was measured with a Fisher subsieve sizer. The obtained powder was filled into a mold having a molding space with a cross section of 153,5 N3-7.4 mm, and a parallel magnetic field of 13 kOe was applied in the horizontal direction, and a hydraulic press with a lifting flow control was used to press the powder in a direction perpendicular to the magnetic field. 0.8 t/c
Apply a pressure of 153.5 x 131.3 x
A preformed body of 37.4 degrees (→ is the direction of anisotropy) was obtained.

Next, place the preform into a latex rubber mold 3
Isostatic pressing (CIF) was performed at a pressure of 141.5 x 126.0x34.
．． It shrunk to 3mm.

The weight of each of these rectangular parallelepiped (plate) shaped molded bodies was approximately 3300 g. In addition, some of these molded bodies were weighed approximately 1660 g per piece under N2 atmosphere for each composition.
Processed into a ring shape. These plate-shaped and ring-shaped molded bodies were sintered in an argon atmosphere at a temperature range of 1150 to 1210°C depending on the composition.

Re126 X103 X30 and φ100 Xφ40
It was approximately 30 mm. - indicates the magnetization direction. Next, these plate-shaped and ring-shaped sintered bodies are processed according to their compositions.
2 in the temperature range of 950-1100°C under argon atmosphere
After holding for h, furnace cooling is performed at a cooling rate of 0.1 to 2°C/min, and the temperature is 12 to 12°C at a temperature of 690 to 870°C depending on the composition.
After 24 hours of holding, a volume of 20
! Static cooling was performed in a steel container. After cooling to room temperature, the magnets with a total of 14 compositions were hand-polished to remove their outer skins and observed for cracks. As a result, no cracks were observed.

In order to evaluate the magnetic properties of these magnets,
A test piece of ×8ffi was cut out and the measurement results are shown in Table 1.

As is clear from the table, as the Co content decreases and the number of precipitated phases increases, although it can be said that there is some variation, iHc tends to increase, but the residual magnetic flux density Br decreases. The magnetic properties used in automobile electrical equipment and the like are 8000G or more in Br, more preferably 8500G or more.

In addition, the higher the coercive force iHc is, the more desirable it is, but when considering the above relationship of 1.3
It is 0e or more. Among the compositions shown in the table, the composition range that satisfies the more preferable magnetic properties Br≧8500G and iHc≧150000e is 63% by weight of Co. O~65.0%
It is within the range of , and fully satisfies the specifications in each field. In addition, a magnet with a Co content of 65.80% by weight has an iH
c has decreased to 38,000e, indicating that it is inappropriate to apply the heat treatment method of the present invention to magnets with conventional compositions.

The magnetic properties were measured using test pieces cut from both a plate-shaped magnet and a ring-shaped magnet, but the influence of the shape and weight on the heat treatment method of the present invention was extremely small, and there was no significant difference in Br. , iHc is approximately 330
A decrease of about 100 to 200 G in a large plate magnet weighing 0 g was only found for a test piece cut from a ring-shaped magnet weighing approximately 1660 g shown in Table 1, and the heat treatment method of the present invention It can be seen that this method is extremely effective in producing large integrated RMs rare earth magnets with excellent magnetic properties without the occurrence of cracks.

Example 2 A permanent magnet alloy with a conventional composition having a Co content of 66.0% by weight and the balance Sra was treated in the same manner as in Example 1 to obtain a φ100×
A ring-shaped sintered body of φ40×30 tmm was obtained. Next, by the heat treatment method of the present invention, it was held at 1000°C for 1 hour, then furnace cooled at 1°C/min to 800°C, and after holding at 800°C for 24 hours, it was treated in the same manner as in Example 1. It was placed in a cooling box. Although no cracks were observed after manual polishing, the magnetic properties evaluated in the same manner as in Example 1 were as follows: Br=9360G bHc=16500e
1Hc=31600e (BH)max=8.7MG
00e, and although Br is a high value, i
Hc has decreased significantly, and Co 65.80 in Table 1
In combination with the weight % results, it can be seen that the decrease in iHc due to the West tendorp effect is so large that it is difficult to put it into practical use.

In addition, a 1010X9X8 test piece with a Co content of 66.0% by weight and a φ of 64.00% by weight of Co shown in Table 1 were also used.
After holding a ring-shaped sintered body of 100×φ40×30 tmm at 1050°C for 1 hour, it was furnace-cooled to 800°C at a cooling rate of 1.0°C/min, and when it reached 800°C, As a result of conventional heat treatment of quenching in oil, C.
o For the test piece with 66.0% by weight, Br=925
0G b) lc=88000e.

iHc=200000e, (BH)max=20.4
Excellent magnetic properties of MGOe were obtained, but Co64.0
The large ring magnet containing 0% by weight was not only accompanied by cracks, but also cracked. From this fragment, lQX9
As a result of cutting out a test piece of X8mm and measuring its magnetic properties, Br=7600G, bHc=64400e
, 1Hc=163000e(BH)max-13,4M
GOe, and in particular, it became clear that the decrease in Br was remarkable.

This example shows that the conventional heat treatment method is necessary for the SmCo5 magnet with the conventional composition, and the 5r6Co5 magnet with the present composition.
In the case of magnets, high magnetic properties cannot be obtained with the heat treatment method of the present invention, and with conventional compositions and heat treatment techniques, large SmCo5 [stones] cannot be produced without cracking and/or cracking. I understand that.

Example 3 A permanent magnet alloy consisting of a Go type weight of 63.50.64.25% and a balance of 64.50% Sm was prepared in the same manner as in Example 1.
126 ingots and pears using the same method as in Example 1.
A sintered body measuring 53 mm x 30 mm and weighing 2000 g was obtained. Next, the initial holding temperature T+ by the heat treatment method of the present invention
The treatment was carried out by variously changing the conditions of the furnace cooling rate Vt and the standing temperature T2 on the low temperature side, and the process was carried out in the same manner as in Example 1, and the samples were allowed to stand and slowly cool under an Ar atmosphere. A portion of the results are shown in Table 2. From the table, it can be seen that in sample 9, where T was lower than the sintering temperature by more than 300°C, the holding force decreased significantly. This can be said to be because the precipitation of the 2/7 phase that increases iHc does not occur sufficiently because the temperature is below. In addition, in sample 6 where the furnace cooling rate Vt was as high as 4" (/11in), both Br and bHc decreased, which is thought to be because the precipitation at each temperature during furnace cooling could not be followed. On the other hand, T
Sample Nα5 where 2 was lower than the sintering temperature by 500°C or more
However, a decrease in coercive force occurs, but this is interpreted to be due to the occurrence of an -es tendorp effect, although it is mild. Although it is quite possible to generate a sufficient coercive force iHc even at an extremely slow rate with Vt of 0.03°C or less, from an industrial perspective, it is important to avoid spending too much time on heat treatment. It's not a good idea. From the above results shown in Table 2, the holding temperature T on the high temperature side is the temperature range that can be used in the heat treatment method of the present invention.

is lower than the sintering temperature by 300°C, and the furnace cooling rate Vt
was limited to 0.03 to 3°C, and the low-temperature side holding temperature T2 was limited to a low temperature within 500°C below the sintering temperature.

Moreover, within the composition range in which the Co amount is 63.00 to 65.00% by weight, a permanent magnet with excellent magnetic properties can be manufactured within the above-mentioned limited range. In addition, T1 shown in Table 2
Since the magnets are large, the retention times for T2 and T2 are 2 hours and 1 hour, respectively, in order to equalize the heat between the magnet surface and the inside.
The evaluation was performed by setting the time to 5 hours.

Example 4 Metal CeMM (Mitshu Metal) 37% by weight, Co6
2% by weight, 1% by weight of one of Fe, Ni, and Cu were weighed and blended, and then CeMM-Co-Fe and CeM were melted in a high-frequency melting furnace under an Ar protective atmosphere, respectively.
Permanent magnet alloys having compositions of M-Co-Ni and CeMM-Co-Cu systems were melted and cast into ingots. Next, the fine powder obtained by pulverization in the same manner as in Example 1 was filled into molds having disk-shaped and ring-shaped molding spaces, respectively, and heated at 1.2 t/min in a direction parallel to an applied magnetic field of 10 kOe.
By applying a pressure of cm2, each plate has a disc shape of approximately 33 mm.
A ring-shaped molded product weighing approximately 280 g/piece was obtained. Next, sintering was carried out in argon at a temperature range of NO□-1200"c depending on the composition, and the disc shape was approximately φ50 x 20 tmm and the ring shape was φ50 x φ.
A sintered body of 2°×20tIII+ was obtained. The shape varies by about 1 mm depending on the composition. These ring magnets were heat-treated under substantially the same conditions as in Example 1, including cooling in Ar. Table 2 shows the measurement results of magnetic properties.

The magnetic properties in Table 3 are lower than those in Table 1. The reason for this is that rare earth elements have good magnetic properties but are also expensive instead of Sm. This is because the raw material is CeMM, an alloy consisting of several kinds of rare earth elements, mainly Ce. Alternatively, by making it cylindrical, the permeance coefficient is increased and the total amount of magnetic flux is increased, so that it can be used industrially. In addition, since the molding method in this example applies pressure parallel to the direction of the external magnetic field, Example 1
Compared to the case of pressure forming in the direction perpendicular to the external magnetic field mentioned above, the Br value is reduced by about 10%.

The obtained magnet was visually inspected after manual polishing in the same manner as in Example 1, but no cracks or cracks were observed.

On the other hand, as in Example 1, cracks were generated in all samples as a result of conventional heat treatment including cold treatment.

Example 5 In Examples 1 to 3, using the composition and heat treatment method of the present invention,
We have specifically discussed large rare earth magnets. However, the composition system of the present invention can be sufficiently applied to conventional small-sized magnets, and the heat treatment can be performed at a temperature lower than the sintering temperature by 500°C for 1 hour or more, preferably 4 hours. After the above holding, a magnet with excellent magnetic properties can also be obtained by performing a quenching treatment such as quenching in oil.

A permanent magnet alloy having a Co content of 63.0 to 65.0% by weight and the balance being Sm was treated in the same manner as in Example 1 to obtain a 120X6
A sintered body of 0×12 mm was obtained. Next, by punching using ultrasonic waves, the sintered body was cut into φ10×φ5×12tl.
A cylindrical magnet with two poles in the longitudinal direction was used. The weight of each magnet was approximately 5 g.

The obtained cylindrical magnet was heated in the same manner as in Example 1 at a low temperature of about 300°C or less than the sintering temperature, that is, 950°C to 11°C.
After holding at 00°C for 1 hour, furnace cooling was performed at 0.1 to 2°C/min, and the temperature was kept at a low temperature of about 500'C or less than the sintering temperature, that is, 690 to 870'C, for more than 4 hours. After cooling, the test piece was cut out and the magnetic properties measured are shown in Table 4.

As is clear from the table, the magnet of the present invention, in the case of a small size, has high magnetism even when it is held at a low temperature approximately 500"C or less than the sintering temperature for a certain period of time and then rapidly cooled. However, as a result of subjecting the cylindrical magnet obtained in this example to the conventional heat treatment including rapid cooling described in Example 2, the Br was 74 as in the result of Example 2.
The characteristics were low at the 00-7800G level.

〔Effect of the invention〕

Since the heat treatment method of the present invention has the structure and operation as described above, it is possible to treat RM5 rare earth permanent magnets with high magnetic properties of 200 g or more, even 1000 g or more, which was previously impossible, without causing cracks. It has the advantage that it can be provided in square, disc, ring, or cylindrical shapes without any accompanying magnets, and that conventional small-sized magnets can also be obtained in the same way.

[Brief explanation of drawings]

Fig. 1 is a phase diagram of the Sm-Co system, Fig. 2 is a diagram showing an example of a wiggler in which the permanent magnet according to the present invention is used, Fig. 3 is a schematic assembly diagram of a hybrid undulator according to the present invention, FIG. 4 is a diagram showing a simulation of the flow of magnetic flux during the assembly shown in FIG. 3 according to the present invention, and FIG. 5 is a diagram showing changes in the strength of the demagnetizing field depending on the installation position of the magnet according to the present invention.

Claims (2)

[Claims] (1) The RM_5 and R_2M_7 phases are formed in the sintered product from a combination of at least one rare earth element represented by R and Co or Co and at least one element from the Fe, Ni, and Cu group, represented by M. In a sintered product consisting of R and M having a composition such that the proportion of M is 63% by weight
The coercive force in the second quadrant on the B-H curve of magnetic properties after sintering and heat treatment is bH.
This is a manufacturing method for rare earth permanent magnets in which the absolute value of the inflection point on the 4πI-H curve in the second quadrant is greater than the absolute value of 1.3×bHc, and the sintering temperature is 300
The temperature was raised again to a low temperature within °C, and the temperature was increased for 10
After holding for more than 1 hour, furnace cooling was performed at a cooling rate of 0.03 to 3°C/min to a lower temperature within 500°C than the sintering temperature, and after holding at this temperature for more than 1 hour, an average cooling rate of 5 ~
A method for heat treatment of rare earth magnets, characterized by slow cooling to approximately 400°C or less at a rate of 50°C/min. (2) When heat-treating the sintered product having the composition described in claim (1) by the method described in claim (1), furnace cooling is performed to a temperature lower than the sintering temperature by 500°C or less. conduct,
A method for heat treatment of rare earth magnets, which comprises maintaining the temperature at the temperature for one hour or more, and then rapidly cooling it by oil cooling, fluidized bed cooling, blast cooling, or the like.