JPH04324916A - Manufacture of rare earth/iron permanent magnet - Google Patents

Abstract

PURPOSE:To accomplish low cost and high efficiency in the manufacture of permanent magnet containing R(R is at least a kind of element selected from rare-earth elements containing Y), Fe and B as fundamental raw material component. CONSTITUTION:An alloy having R(R is at least a kind of element selected from rare earth elements containing Y), Fe and B as the fundamental component of raw material, is fused and cast, it is brought into an anisotropic state by conducting a hot processing at 500 deg.C or higher, Then it is heat-treated at 1000 to 1050 deg.C, and another heat treatment is conducted at 450 to 700 deg.C. In order to obtain higher coercive force and higher efficiency, a heat treatment is conducted at 1000 to 1050 deg.C, then a two-step heat treatment, in which the material is cooled down to 450 deg.C or lower at the speed of 5 deg.C/min. or higher and then reheated again to 450 to 700 deg.C and cooled down to room temperature, is repeated twice or more times.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing a permanent magnet having magnetic anisotropy due to mechanical orientation, and in particular R
is at least one rare earth element including Y), Fe,
This invention relates to a method for producing a permanent magnet using B as a basic raw material component.

0002

[Prior Art] Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from various household electrical appliances to peripheral terminal equipment for large computers.
With the recent demand for smaller and more efficient electrical products,
Permanent magnets are also required to have increasingly higher performance.

Permanent magnets are materials for generating magnetic fields without externally supplying electrical energy, and those with large coercive force and high residual magnetic flux density are suitable.

Typical permanent magnets currently in use are alnico cast magnets, ferrite magnets, and rare earth-transition metal magnets, particularly R-Co permanent magnets, which are rare earth-transition metal magnets. R-Fe-B permanent magnets have been extensively researched and developed as permanent magnets with extremely high coercive force and energy product.

Conventionally, there are the following methods for producing these R-Fe-B-based high-performance anisotropic permanent magnets.

(1) First, Japanese Patent Laid-Open No. 59-46008 and M. Sagawa, S. Fujimura, N.
Togawa, H. Yamamoto and Y. Ma
tsuura;J. Appl. Phys. Vol. 55
(6), 15 March 1984, p2083 etc., a magnetic anisotropy consisting of 8 to 30% R (however, R is at least one rare earth element including Y), 2 to 28% B, and the balance Fe. It is disclosed that a permanent magnet characterized by being an orthogonal sintered body is manufactured by sintering based on a powder metallurgy method.

[0007] In this sintering method, an alloy ingot is produced by melting and casting, and then pulverized to obtain magnetic powder with a suitable particle size (several μm). The magnetic powder is kneaded with a binder, which is a molding aid, and press-molded in a magnetic field to complete a molded product. The compact is sintered in argon at a temperature of around 1100° C. for 1 hour and then rapidly cooled to room temperature. After sintering, the permanent magnet is heat-treated at a temperature of around 600°C to further improve its coercive force.

[0008] Regarding heat treatment of this sintered magnet, Japanese Patent Application Laid-Open No. 61-217540 and Japanese Patent Application Laid-Open No. 62-165
No. 305 and the like disclose the effects of multistage heat treatment.

(2) Japanese Unexamined Patent Publication No. 59-211549 and R. W. Lee; Appl. Phys. Let
t. Vol. 46(8), 15 April1985,
P790 discloses an R-Fe-B magnet in which fine pieces of melt-spun alloy ribbon with a very fine crystalline magnetic phase are bonded together with a resin.
This permanent magnet is manufactured by making a quenched thin piece with a thickness of about 30 μm using a quenched ribbon manufacturing apparatus used for manufacturing an amorphous alloy, and then kneading the thin piece with a resin and press-molding it.

(3) Japanese Unexamined Patent Publication No. 60-100402 and R. W. Lee; Appl. Phys. Let
t. Vol. 46(8), 15 April1985,
For p790, the quenched flakes used in the method (2) above are processed into a dense and anisotropic R-Fe-
It is disclosed to obtain a B magnet.

(4) JP-A No. 62-276803 discloses that R (R is at least one of rare earth elements including Y) 8 to 30 atomic %, B 2 to 28 atomic %, Co
After melting and casting an alloy consisting of 50 at% or less Al, 15 at% or less Al, and the balance being iron and other impurities unavoidable in manufacturing, the cast ingot is hot worked at a temperature of 500°C or higher to form crystal grains. A rare earth-iron permanent magnet is disclosed, which is characterized by making the cast alloy magnetically anisotropic by making the cast alloy finer and orienting its crystal axis in a specific direction.

Regarding the heat treatment of this hot-processed magnet, an appropriate temperature range is disclosed in JP-A-63-114105, and the effect of two-stage heat treatment is disclosed in JP-A-1-72732. In addition, Japanese Patent Application No. 2-122582, Japanese Patent Application No. 2-127
412, Japanese Patent Application No. 2-127413 shows the appropriate heat treatment according to the constituent elements, Japanese Patent Application No. 2-127414 shows the heat treatment time, and Japanese Patent Application No. 2-127415 shows the heat treatment after heat treatment to prevent cracking. The cooling rate is shown.

[0013]

[Problem to be solved by the invention] (1) to (4) above
The conventional method for manufacturing R-Fe-B permanent magnets has the following drawbacks.

[0014] The permanent magnet manufacturing method (1) requires the alloy to be powdered, but R-Fe-B
Since the alloy is very active against oxygen, oxidation becomes even more intense when it is powdered, and the oxygen concentration in the sintered body inevitably increases.

[0015] Furthermore, when molding the powder, a molding aid such as zinc stearate must be used, and this is removed beforehand during the sintering process, but several percent of the molding aid is , the carbon remains in the magnet body in the form of carbon, which is undesirable because it significantly reduces the magnetic performance of the R-Fe-B magnet.

[0016] The molded body after press molding with the addition of a molding aid is called a green body, which is very brittle and difficult to handle. Therefore, a major drawback is that it takes a considerable amount of effort to arrange them neatly in the sintering furnace.

Due to these drawbacks, generally speaking, the production of R-Fe-B sintered magnets not only requires expensive equipment, but also has poor production efficiency. As a result, the manufacturing cost of the magnet increases. Therefore,
It is not possible to take advantage of the advantages of R-Fe-B magnets, which have relatively low raw material costs.

Next, in the methods (2) and (3) for manufacturing permanent magnets, a vacuum melt spinning device is used.
This equipment is currently very unproductive and expensive.

Since the permanent magnet (2) is isotropic in principle, it has a low energy product, and the squareness of the hysteresis loop is also poor, which is disadvantageous in terms of temperature characteristics and use.

The method (3) for manufacturing permanent magnets is a unique method of using hot press in two stages, but it cannot be denied that it is inefficient when considering actual mass production. Furthermore, in this method, at high temperatures, e.g., 800°C or higher, the crystal grains become significantly coarsened, which reduces the coercive force.
The iHc is extremely low and it cannot be used as a practical permanent magnet.

[0021] The method (4) for manufacturing permanent magnets does not involve a powder process and requires only one step of hot pressing, so it is the manufacturing method that simplifies the manufacturing process the most and can reduce mass production costs. However, there was a problem that the magnetic properties were lower than those of the sintering method and had large variations.

The present invention solves the above-mentioned drawbacks of the prior art, especially (
4) This method solves the drawbacks of permanent magnet performance and its large variation, and its purpose is to provide a high-performance, low-cost manufacturing method for rare earth-iron permanent magnets. be.

[0023]

[Means for Solving the Problems] The method for producing a rare earth-iron permanent magnet of the present invention uses R (where R is at least one rare earth element including Y), Fe, and B as basic raw material components, and The alloy as a basic component is melted and cast, then the cast ingot is hot worked at a temperature of 500 to 1100°C, then heat treated at 1000 to 1050°C,
The next heat treatment is characterized by heat treatment at 450 to 700°C.

Further, in order to further improve the performance and increase the coercive force, after the hot working according to claim 1, heat treatment is performed at 1000 to 1050°C, and then cooling to 450°C or less at a rate of 5°C/min or more. It is characterized in that it is then heated again and heat treated at 450 to 700°C.

Another method for producing a rare earth-iron permanent magnet is to use R (where R is at least one rare earth element including Y), Fe, and B as basic raw material components, and to produce an alloy as the basic component. is melted and cast, then the cast ingot is hot worked at a temperature of 500 to 1100°C, then heat treated at 900 to 1000°C, and then heated to 450°C.
It is characterized by repeating two or more times a two-stage heat treatment in which the material is cooled down to below 5°C at a rate of 5°C/minute or more, heated again, heat-treated at 450-700°C, and cooled to room temperature.

The preferred composition range of the permanent magnet in the present invention will be explained below.

[0027] Rare earths include Y, La, Ce, Pr,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, and Lu are listed as candidates, and one or more of these may be used in combination. The highest magnetic performance is obtained with Pr, so Pr,
Pr-Nd alloy, Ce-Pr-Nd alloy, etc. are used. A small amount of heavy rare earth elements, such as Dy and Tb, is effective in improving coercive force.

The main phase of the R-Fe-B magnet is R2Fe14
It is B. Therefore, if R is less than 8 at %, the above-mentioned compound is no longer formed and high magnetic properties cannot be obtained. On the other hand, if R exceeds 30 atomic %, the nonmagnetic R-rich phase increases and the magnetic properties deteriorate significantly. Therefore, the range of R is 8 to 30
Atomic % is appropriate. However, for high residual magnetic flux densities, preferably R 8 to 25 atom % is suitable.

B is an essential element for forming the R2Fe14B phase, and if it is less than 2 atomic %, the rhombohedral R-F
Because it is e-based, high coercive force cannot be expected. Also 28 atomic%
If the value exceeds 1, the amount of B-rich nonmagnetic phase increases, and the residual magnetic flux density decreases significantly. However, in order to obtain a high coercive force, the B content is preferably 8 atomic % or less, and if it is more than that, it is difficult to obtain a fine R2Fe14B phase and the coercive force is small.

The temperature during hot working is preferably at least the recrystallization temperature, and in the case of the R-Fe-B alloy of the present invention, it is preferably at least 500°C. At temperatures above 1100°C, the R2Fe14B phase rapidly grows grains and loses its coercive force, so a temperature below this temperature is preferred.

[0031] The heat treatment temperature is preferably 900°C or higher in order to quickly diffuse the primary Fe crystals and to homogenize the composition of the grain boundary phase in the liquid state, and the outflow of the liquid phase in the magnet is preferably 1050°C. If the temperature is higher than that, the shape of the magnet will be severely lost, so a temperature lower than that is preferable. Also, 1000℃
Above this, diffusion of Fe and homogenization of the grain boundary phase occur quickly, but
At temperatures below 1000°C, a long time is required. but,
In the case of this temperature of 900 to 1000℃, the required time is 4
It can be shortened by cooling and heat treating to 50 to 700°C.

[0032] Furthermore, cooling from a high temperature around 1000°C to 450°C or lower, which is below the final solidification temperature, at a rate of 5°C/min or more is necessary to maintain the uniformity of the grain boundary phase. If the magnet is cooled at a speed lower than this, the composition distribution of the grain boundary phase will be severe, changing the magnetic properties of each magnet particle and deteriorating the coercive force and squareness of the magnet.

Heat treatment at 450 to 700° C. is preferable because the temperature is set just above the eutectic temperature of the grain boundary phase, so that the grain boundary phase, which has become a liquid phase, cleans the surface of the magnet particles and a high coercive force can be obtained. temperature range.

[0034]

[Examples] Examples of the present invention will be described below.

(Example 1) Using an induction heating furnace in an argon atmosphere, Pr10Nd6Fe77.5B5.1Cu
An alloy of composition 1.4 was melted and then cast. At this time, rare earth, iron, and copper raw materials with a purity of 99.9% were used, and boron was ferroboron.

Next, this cast ingot was placed in a capsule made of SS41 steel and sealed under vacuum. 9 to this
Hot rolling at 75° C. with a workability of 20% was carried out twice in air, and then hot rolling at a workability of 30% was carried out three times in air, resulting in a final workability of 78%. During this hot working, the axis of easy magnetization of the crystal was oriented parallel to the direction in which the alloy was pressed, creating magnetic anisotropy. After that, the surface of the sample cut out from this rolled ingot was polished to a surface roughness Rmax≦50 μm, and then heat treated in an Ar atmosphere furnace for 20 hours at a temperature T1 of 800 to 1100°C shown in Table 1, in the furnace 2
Cool to 550°C at a rate of ~3°C/min, then cool to 550°C.
A heat treatment was performed at ℃ for 3 hours.

Table 1 shows the magnetic properties and surface roughness Rmax of these heat-treated samples. All magnetic properties were measured using a B-H tracer after pulse magnetization at 40 kOe.

[0038]

[Table 1]

[0039] From Table 1, heat treatment at 1000 to 1050°C improves residual magnetization and coercive force.
It can be seen that the maximum energy product has been improved. It is also understood that it is not preferable that the heat treatment temperature exceeds 1050° C. because the loss of surface shape due to elution of the liquid phase is large.

(Example 2) Pr15Tb1.0Fe68
An alloy with a composition of Co10B4.8Cu1.2 (Sample 2a) and Pr10Nd7Fe76.5B5Cu1.0
Alloy with a composition of Ga0.5 (Sanfil 2b) and Ce1
．． 0Nd14.5Dy2Fe75.5B5.3Cu1.
An alloy having a composition of 0Al0.7 (Sanfil 2c) was melted and cast in the same manner as in Example 1 to obtain a cast ingot.

Next, from this cast ingot, 15 mm
A cylindrical sample of φ x 15 mmh was cut out, a 5 mm thick iron ring was fitted around it, and hot pressed at 950° C. in an argon atmosphere to a working degree of 80%. The press pressure at this time is 0.2 to 0.9 to
n/cm2, and the strain rate is 10-3 to 10-4/se
It was c.

[0042] After this, the temperature was increased to 1010°C using an Ar atmosphere furnace.
After heat treatment for 12 hours at
The sample was cooled at a rate of 10°C/min, then heat treated at 580°C for 2.5 hours, and then cooled at a rate of 10°C/min as before, cut and polished, and its magnetic properties were measured.

The magnetic properties of this magnet are shown in Table 2.

[0044]

[Table 2]

As shown in Table 2, it can be seen that even when the hot pressing method is employed as the hot working method, the same heat treatment effect as in the case of the hot rolling method of Example 1 is obtained.

(Example 3) Using an induction heating furnace in an argon atmosphere, Pr13.2Nd3.8Fe77.0B5
．． An alloy having a composition of 2Cu0.8 was melted and then cast. At this time, the raw materials for rare earths, iron and copper are 99.9
% purity, and ferroboron was used as boron.

Next, this cast ingot was placed in a capsule made of SS41 steel and sealed under vacuum. 10 for this
After heating to 00℃, hot rolling with a working degree of 20% in air.
Then, hot rolling with a working degree of 30% was performed twice in air, and finally hot rolling was performed once with a working degree of 15%, so that the final working degree was 73%.

[0048] Thereafter, a sample was cut out from this rolled ingot, polished, and then heat treated at 1030°C for 15 hours in an Ar atmosphere furnace, and heated to 400°C by gas cooling in the furnace at 3 to 15°C as shown in Table 3. The sample was cooled at a rate of 7° C./min, then heat treated at 550° C. for 4 hours, and cooled to room temperature at a rate of 7° C./min.

Table 3 shows the magnetic properties of the samples after these heat treatments. All magnetic properties were measured using a B-H tracer after pulse magnetization at 40 kOe.

[0050]

[Table 3]

Table 3 shows that when the cooling rate after heat treatment at 1000 to 1050°C is 5°C/min or more, the squareness and coercive force are improved, and the maximum energy product is improved. I understand.

(Example 4) A sample was cut out from the rolled ingot used in Example 3, polished, and then heat treated in an Ar atmosphere under the following conditions.

Condition 1: After heat treatment at 950°C for 20 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 4 hours, then cooled at a rate of 7°C/min.

Condition 2: After heat treatment at 1020°C for 20 hours, cooling at a rate of 10°C/min, then heat treatment at 550°C for 4 hours, then cooling at a rate of 7°C/min.

Condition 3: After heat treatment at 950°C for 40 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 8 hours, then cooled at a rate of 7°C/min.

Condition 4: After heat treatment at 950°C for 20 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 4 hours, then cooled at a rate of 7°C/min. Repeat this twice.

Condition 5: After heat treatment at 950°C for 20 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 4 hours, then cooled at a rate of 7°C/min. Repeat this three times.

Condition 6: After heat treatment at 900°C for 20 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 4 hours, then cooled at a rate of 7°C/min. Repeat this twice.

Condition 7: After heat treatment at 975°C for 20 hours,
Cooled at a rate of 10°C/min, then heat treated at 550°C for 4 hours, then cooled at a rate of 7°C/min. Repeat this twice.

Table 4 shows the magnetic properties of each sample after these seven types of heat treatment.

[0061]

[Table 4]

From the results in Table 4, after heat treatment at 900 to 1000°C, cooling at a cooling rate of 5°C/min or more resulted in a temperature of 475 to 1000°C.
Repeating heat treatment at 700℃ two or more times
It can be seen that it is effective in improving the squareness and coercive force, and increasing the maximum energy product.

(Example 5) Alloys having the compositions shown in Table 5 were melted and cast in the same manner as in Examples 1 to 4. The raw materials used were also of similar purity.

Next, this cast ingot was placed in a capsule made of SS41 steel and sealed under vacuum. 10 for this
After heating to 00℃, hot rolling with a working degree of 30% in air.
The process was repeated four times until the final degree of processing was 76%.

[0065] After that, a sample was cut out from this rolled ingot, polished, and then heat treated at 1030°C for 12 hours in an Ar atmosphere furnace, and then cooled to 400°C at a rate of 15°C/min by gas cooling in the furnace. and then 600
Heat treated for 4 hours at ℃, then heated to room temperature at 10℃
Cooled at a rate of 1/min.

Table 6 shows the magnetic properties of these heat-treated samples. All magnetic properties were measured using a B-H tracer after pulse magnetization at 40 kOe.

[0067]

[Table 5]

[0068]

[Table 6]

From the above examples, it can be seen that permanent magnets whose basic raw materials are R (where R is at least one rare earth element including Y), Fe, and B can be anisotropically formed by hot working at 500°C or higher. It is then heat treated at 1000 to 1050℃, and then heat treated at 450 to 700℃ to increase coercive force and improve performance.
Heat treated at 0 to 1050℃, then cooled to 450℃ or less at a rate of 5℃/min or more, and then heated again to 45℃.
Heat treatment at 0 to 700℃ further increases coercive force and improves squareness, and after hot working,
Two-stage heat treatment is repeated two or more times: heat treatment at 900-1000°C, then cooling at a rate of 5°C/min or more to below 450°C, heating again, heat-treating at 450-700°C, and cooling to room temperature. As a result, the same higher coercive force and improved squareness as above were achieved, resulting in the best (B
It is clear that H) max exceeds 30 MGOe.

[0070]

[Effects of the Invention] As described above, the method for manufacturing a permanent magnet of the present invention has the following effects.

(1) The c-axis orientation rate can be increased, the residual magnetic flux density Br can be significantly increased, and the coercive force iHc can be increased by making the crystal grains finer.
It was possible to significantly improve the maximum energy product (BH) max.

(2) The manufacturing process is simple, so the cost is low.

(3) Compared to conventional sintering methods, the number of processing steps and production investment can be significantly reduced.

(4) Compared to the conventional method of producing magnets using melt spinning, it is possible to produce magnets with high performance and at low cost.

(5) Magnetic properties can be improved compared to conventional hot-processed magnets.

Claims (3)

[Claims] [Claim 1] R (where R is at least one rare earth element including Y), Fe, and B as basic raw material components,
The alloy as the basic component is melted and cast, then the cast ingot is hot worked at a temperature of 500 to 1100°C, then heat treated at 1000 to 1050°C, and then heat treated at 450 to 700°C as the next heat treatment. A method for producing a rare earth-iron permanent magnet, characterized by: [Claim 2] After the hot working of Claim 1, 1000 to 1
Heat treated at 050℃, then 5℃ below 450℃
Cool at a rate of at least 450-7 minutes and then heat again.
2. The method for producing a rare earth-iron permanent magnet according to claim 1, characterized in that the heat treatment is carried out at 00°C. Claim 3: After hot working according to Claim 1, 900-1
Heat treated at 000℃, then 5℃ to below 450℃
Cool at a rate of at least 450-7 minutes and then heat again.
A method for producing a rare earth-iron permanent magnet, characterized by repeating two or more times a two-stage heat treatment of heat treatment at 00°C and cooling to room temperature.