JPH07138672A - Production of rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To improve magnetic properties, such as coercive force and squareness ratio, and product yield by subjecting a rare earth containing permanent magnet material of specific composition to primary sintering at a liquid phase crystallization temp. and then to secondary sintering at a temp. higher than the temp. CONSTITUTION:The rare earth permanent magnet alloy has a composition consisting of, by weight ratio, 22-27% R (one or more kinds among Sm, Nd, Pr, Y, and Ce as rare earth elements), 10-25% Fe, 5-10% Cu, 0.1-6% M(one or more elements among Mn, Ti, Zr, and Hf), and the balance essentially Co. This magnet material is subjected to primary sintering at 1120-1200 deg.C as a liquid phase crystallization starting temp. and then to secondary sintering at a temp. higher by 20-30 deg.C than the primary sintering temp. By this method, the dense rare earth permanent magnet having uniform composition and fine crystal structure can be obtained. Further, if necessary, one or >=2 kinds among 0.003-0.015% B, 0.003-0.010% P, and 0.003-0.010% S are incorporated into this magnet material.

Description

Detailed Description of the Invention

[0010]

BACKGROUND OF THE INVENTION The present invention relates to a R ₂ M ₁₇ system containing a rare earth element or a rare earth element and a transition element as main components (however,
R is a rare earth element containing Sm, Nd, Pr, Y and Ce, M
Mainly represents a transition element), particularly, a coercive force (bHc) and a squareness ratio ((BH) max / Br)
² ) It relates to a manufacturing method for improving. It also relates to a manufacturing method for improving the manufacturing cost of the permanent magnet alloy.

[0020]

2. Description of the Related Art In recent years, Sm-Co type 2-17 type has been developed and widely used as a rare earth permanent magnet having excellent magnetic properties such as coercive force, residual magnetic flux density and squareness ratio. Further, since this permanent magnet contains a large amount of expensive Sm, Sm
Many permanent magnets (2-17 low-cost type) have been developed in which a part of Nd, Pr is replaced with an inexpensive rare earth element.
On the other hand, in this 2-17 low cost type, part of Sm is Nd, Pr.
And the like, the magnetic characteristics are deteriorated. Therefore, in order to improve it, transition elements such as Mn and Zr and B and P
Trace elements such as are added.

In addition to the development of the improvement of the magnetic characteristics by the composition of such rare earth permanent magnet, many improvements of the magnetic characteristics by the manufacturing method have been proposed. For example, there is the following disclosure regarding improvement of aging treatment. B) In Japanese Examined Patent Publication No. 2-48616, the squareness ratio and the coercive force iHc are obtained by aging treatment methods for a specific alloy composition a plurality of times.
Improvements have been disclosed. B) JP-A-61-136631 and JP-A-61-2
In No. 10161, the maximum energy product (BH) ma was determined by the repeated aging treatment (3 times) in a specific alloy composition.
An improvement in x is disclosed. Next, there is the following disclosure regarding improvement by a combination of solution treatment and aging treatment. C) In Japanese Patent Publication No. 27425/1990, improvement of coercive force iHc is reported by a method of solution treatment at a temperature lower than the sintering temperature by 10 to 50 ° C. and then repeated aging treatment (twice) in a specific alloy composition. ing.

Further, there is the following disclosure for improvement by a combination of sintering and aging treatment. D) According to Japanese Examined Patent Publication No. 60-34632, primary sintering is performed at a temperature of 1100 to 1250 ° C. in a specific alloy composition, then at a temperature of 1150 to 1250 ° C., and a temperature 3 to 30 ° C. higher than the primary sintering temperature. After performing secondary sintering in
Improvements in squareness ratio and coercive force iHc have been reported by the two-step aging treatment method. Further, there is the following disclosure regarding improvement by a combination of sintering, solution treatment and aging treatment. (E) In Japanese Patent Publication No. 28502/1989, improvement of coercive force iHc and squareness ratio is reported by a specific sintering / solution treatment and a two-step aging treatment in a specific alloy composition.

According to the above reports on the improvement of the magnetic properties by the composition of the rare earth permanent magnet or the improvement of the magnetic properties by the manufacturing method, the coercive force is improved for iHc. The coercive force bHc and the i
The relationship of Hc is shown in Fig. 1 by quoting "Development of permanent magnets, material design and analysis of magnetic circuits, design application technology" (1986) issued by Sogo Gijutsu Center. bHc is dominated by remanent magnetization, and its upper limit value is 4πI _r . Note that the magnitude relationship between the values of bHc and iHc is bHc <i
Hc.

[0060]

[Figure 1]

[0070]

DISCLOSURE OF THE INVENTION Disclosure of these manufacturing methods is, firstly, a manufacturing method for improving magnetic properties in a specific alloy composition, and secondly, specific aging treatment is indispensable. A third or improved magnetic property consisting of only or an aging treatment in combination with another treatment relates to the squareness ratio, the coercive force iHc or the maximum energy product (BH) max. Further, although the disclosure for improving the magnetic characteristics as described above has been made, no improvement in the manufacturing method for reducing the manufacturing cost of the expensive rare earth permanent magnet has been reported. An object of the present invention is to improve the magnetic properties of 2-17 type rare earth permanent magnets, especially the coercive force (bHc) and the squareness ratio, only by the sintering method. In addition, 2-17
The present invention provides a sintering method for improving the manufacturing yield at the time of sintering a rare earth permanent magnet of the type.

[0080]

DISCLOSURE OF THE INVENTION The inventors of the present invention relate to a 2-17 type rare earth permanent magnet and note that the sintering method is liquid phase sintering, and the coercive force (bHc) and the squareness ratio ((BH ) M
ax / Br ² ) and the production yield at the time of sintering. As a result of intensive research, as a result of the two-stage sintering method of performing primary sintering at a liquid phase crystallization start temperature and then performing secondary sintering, The inventors have found that the object is achieved and completed the present invention.

The present invention will be described in detail below. The present invention relates to a 2-17 type rare earth permanent magnet, and to a method for sintering a 2-17 type rare earth permanent magnet, the sintering of which is liquid phase sintering. The alloy composition of this 2-17 type rare earth permanent magnet is preferably set to the following practical range. this
2-17 type rare earth permanent magnet R (Sm, N
If the content of d, Pr, Y, or Ce) is less than 22%, iHc decreases and (BH) max also decreases. Two
This is because if it exceeds 7%, Br decreases. If the Fe content is less than 10, Br decreases, and if it exceeds 25%, i decreases.
This is because Hc decreases. Transition element M (Mn, Ti,
This is because if the content of one or more of Zr and Hf) is less than 0.5%, sufficient iHc cannot be obtained, and if it exceeds 6%, Br decreases. This is because if the content of the trace element B is less than 0.003, the effect of improving the squareness is small, and if it exceeds 0.015%, the iHc decreases. If the trace elements P and S are less than 0.003, the effect of improving the squareness is small, and
This is because iHc decreases when it exceeds 10%. In addition,
In the present invention, when it is desired to improve the coercive force bHc and squareness ratio of a 2-17 type rare earth permanent magnet formed by liquid phase sintering, or to improve the manufacturing yield during sintering, the range is limited to the above alloy composition. Not a thing.

This 2-17 type rare earth permanent magnet is manufactured by
After molding the alloy powder consisting of predetermined components with a magnetic field press,
The steps include sintering, solution treatment, and aging treatment in an atmosphere of an inert gas (for example, argon gas) or a reducing gas (for example, hydrogen gas). In the method of the present invention, in this sintering step, primary sintering is performed at a liquid phase crystallization temperature of 1120 to 1200 ° C., and then 20 to 30 ° C. higher than the primary sintering temperature.
Perform secondary sintering at a high 1140-1230 ° C. In the conventional two-stage sintering method, primary sintering is performed at a high sintering temperature in order to obtain a dense (= increased density of the sintered body) and homogeneous permanent magnet, and then a temperature higher than the primary sintering temperature. High temperature 1
Secondary sintering is performed at 150 to 1260 ° C. That is, the 2-17 type rare earth permanent magnet is being sintered due to mutual diffusion of two phases, a liquid phase and a solid phase. Therefore, it is disclosed that by increasing the sintering temperature, a large amount of liquid phase is crystallized, so that the density of the sintered body is increased and the squareness ratio is improved.

In the present invention, the primary sintering is 1120-120.
It is performed at a temperature lower than the sintering temperature of 0 ° C., which is a liquid phase crystallization start temperature. Since the temperature is low, the sintering proceeds in a state where the generation of the liquid phase is small. Therefore, when the primary sintering is completed, the solid is solidified by the peritectic reaction to homogenize the composition. Further, since the low temperature sintering is performed prior to the next high temperature sintering, the deformation of the sintered body caused by the liquid phase sintering during the high temperature sintering is reduced. Next, 20-30 ° C from the primary sintering temperature
Secondary sintering is carried out at high temperatures of 1140-1230 ° C.
As a result, a sintered body having a dense and fine composition and a uniform crystal structure was obtained, and it was confirmed that the squareness ratio and the coercive force bHc were improved.

If the temperature higher than the primary sintering temperature is lower than 20 ° C., the crystallized amount of the liquid phase is small and the density cannot be increased, and the squareness ratio and the coercive force bHc are improved as compared with the conventional one-step sintering. It has not been. On the other hand, when the temperature exceeds 30 ° C, crystallization of the liquid phase increases and densification progresses. However, the crystal grains become coarse, and Sm, Cu, etc., which are the main components, begin to segregate. In order to eliminate this segregation and recover bHc and the squareness ratio, it is necessary to carry out the solution treatment for a long time at the next solution treatment time. In FIG. 2, 1
6.2% Sm-9.3% Nd-13.6% Fe-6.3
% Cu-2.4% Zr-0.3% Mn-0.3% Ti-
The influence of the secondary sintering temperature on the density, and the coercive force bHc and squareness is shown for an alloy composition of 0.006% B. The abscissa represents the liquid phase crystallization temperature T _LS and the temperature higher than the primary sintering temperature during the secondary sintering, the ordinate represents the density of the secondary sintered body, and the temperature of the secondary sintered body. The values of coercive force bHc and squareness ratio are shown. The density of the primary sintered body sintered at the liquid phase crystallization temperature T _LS is
7.80 g / cm ^3, which is +20 to +30 when the secondary sintering is performed at a temperature higher than the liquid phase crystallization temperature T _LS.
Density of ℃ secondary sintered body 8.17~8.20g / cm ³
Is saturated with. Further, the coercive force bHc and the squareness ratio are also low in the density of the primary sintered body sintered at the liquid phase crystallization temperature T _LS , but due to the increase in the temperature of the secondary sintering in the secondary sintering,
It shows an increasing tendency, but changes to a decreasing tendency with a peak at +20 to + 30 ° C. FIGS. 3 and 4 show the microstructure of the alloy composition shown in FIG. 2 which is obtained by subjecting the secondary sintered body according to the present invention to solution treatment, and FIG. The microstructure examined by the above is shown in FIG.

[0130]

[Fig. 2]

[0140]

[Figure 3]

[0150]

[Figure 4]

In the conventional method, since the compact is heated to a high temperature to crystallize a large amount of the liquid phase, the liquid phase moves to the lower part of the compact during sintering due to its own weight. Therefore, the lower part of the sintered body swells and is deformed. In addition, the liquid phase that has reached the bottom surface of the molded body during sintering is welded to the sintering tray used by placing the molded body during sintering and cracks during cooling after sintering, or the sintered body is detached from the tray. It breaks when you do. However, in the present invention, high temperature secondary sintering is carried out using a sintered body which is primary sintered at low temperature. At this time, compared with the case of performing high temperature sintering from the beginning, since low temperature primary sintering has already been performed, a sintered body that has been solidified by a peritectic reaction and has a uniform composition has been subjected to high temperature sintering. It is used as a base material. Therefore, it is considered that even if the temperature is raised to a high temperature, the movement of the liquid phase toward the lower part of the base material is hindered and the occurrence of deformation or cracking is prevented.

The sintered body which has been subjected to the two-stage sintering method according to the present invention is subsequently subjected to solution treatment and aging treatment. Even if these treatments are performed by a known method, the effect of the two-step sintering method of the present invention is not diminished. In addition to the present invention, the effect of the two-step sintering method of the present invention is not reduced by adopting a specific method in the solution treatment or aging treatment.

[0180]

[Examples] Table 1 shows the compositions of matchmaking funds A1 to C5. The alloy composition shown in claim 1 is shown as A and B series, and the alloy composition shown in claim 2 is shown as C series.

[0180]

[Table 1]

Table 2 shows the liquid crystal crystallization start temperatures of the matchmaking funds A1 to C5. The liquid phase crystallization onset temperature was measured by the DTA (differential thermal analysis) method. That is, powder of match money was molded into a diameter of 3.0 mm and a height of 1.5 mm, and the powder compact was heated at 5 ° C. per minute with DTA to raise the temperature. An endothermic peak appears when the liquid phase begins to crystallize. The temperature range having about 5 ° C. on the high temperature side from this peak appearance temperature was defined as the liquid phase crystallization temperature.

[0200]

[Table 2]

Table 3 shows the sintering conditions according to the method of the present invention for the alloy compositions A1 to C5. The primary sintering temperature was the liquid phase crystallization start temperature shown in Table 2, and the secondary sintering temperature was set to a temperature 20 to 30 ° C. higher than the primary sintering temperature. The secondary sintering temperature was obtained by molding a powder of match alloy into 14φ × 12 mm, then sintering at the primary sintering temperature, and then conducting an experiment for setting the secondary sintering temperature. Further, for comparison with the two-step sintering of the present invention, the alloy compositions A1 to C5 were subjected to one-step sintering as a conventional method. As the conditions for the first-stage sintering, the conditions for the secondary sintering in the two-stage sintering of the present invention were used. The holding time at the primary sintering temperature is 45 minutes, and the holding time at the secondary sintering temperature is 60 minutes. The sintering time for the first-stage sintering according to the conventional method was the same as the holding time at the secondary sintering temperature according to the method of the present invention, which was 60 minutes.

[0220]

[Table 3]

Next, regarding the sintered body thus obtained,
Then, solution treatment and aging treatment were performed by a conventionally known method. That is, the solution treatment is performed at a temperature higher than the secondary sintering temperature by 2
The aging treatment temperature is 750.
After isothermal treatment at ~ 900 ° C, 400 at 0.5-5 ° C / min
It was gradually cooled to 0 ° C and then rapidly cooled. Table 4 shows the results of measuring the coercive force bHc and the squareness ratio of the rare earth permanent magnet prepared by the conventional method as a comparison with the method of the present invention for the alloy compositions A1 to C5.

[0240]

[Table 4]

From the results shown in Table 4, the coercive force bHc is improved by 0.3 to 1.1 kOe as compared with the conventional one-step sintering method by performing the two-step sintering method according to the present invention regardless of the alloy composition. It is recognized that the squareness ratio is also improved by 0.03 to 0.06.

Further, from the experiment of the two-step sintering method of the present invention, it was found that the sintered body was not deformed in the secondary sintering, and the welding to the sintering tray was not observed. Therefore, for alloy compositions A1, B2, B4 and C5, 20 alloy powders were used.
20 pieces each were formed in φx20 mm. Next, the results of examining the number of welds on the sintering tray and the number of deformations of the sintered body by performing 10 sinterings each by the method of the present invention and the conventional method are shown in Table 5.
Shown in. The number of pieces welded to the sintering tray means the number of pieces welded so that the sintered body cannot be taken out from the sintering tray after sintering. The number of deformed sintered bodies means the number of deformed diameters of the sintered body before and after sintering exceeding 10%. The sintering conditions of the method of the present invention and the conventional method were the same as those in Table 3. From Table 5, in the conventional method, welding to the sintering tray or deformation of the sintered body occurs and the product yield is lowered, but in the method of the present invention, there is no welding number to the sintering tray and no deformation number of the sintered body. Therefore, the product yield is improved and the manufacturing cost is reduced.

[0270]

[Table 5]

[0280]

The two-stage sintering method of the present invention, that is, the primary sintering is performed at the liquid phase crystallization temperature, and then 20 to 20
The magnetic properties of the rare earth permanent magnet obtained by the secondary sintering method at a sintering temperature of 30 ° C. are higher than those of the conventional one-stage sintering method in the coercive force bHC and the squareness ratio ((B
H) max / Br ² ) is excellent. In addition, the product yield is remarkably improved because neither deformation during welding nor welding to the sintering tray occurs.

[0290]

[Brief description of drawings]

FIG. 1 shows the relationship between coercive force bHC and iHC.

FIG. 2 shows the effects of secondary sintering temperature on density, squareness ratio and coercive force bHc.

FIG. 3 shows a microstructure of a material obtained by subjecting a secondary sintered body according to the present invention to a solution treatment.

FIG. 4 shows a microstructure of a material obtained by subjecting a sintered body by a conventional method to a solution treatment.

[Procedure amendment]

[Submission date] September 6, 1994

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a drawing-substitute photograph of a microstructure of a material obtained by subjecting a secondary sintered body according to the present invention to a solution treatment.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a drawing-substituting photograph of a microstructure of a material obtained by subjecting a sintered body to a solution treatment by a conventional method.

Claims (2)

[Claims] 1. A weight ratio of 22 to 27% R (wherein R is one or more of rare earth elements Sm, Nd, Pr, Y and Ce),
10-25% Fe, 5-10% Cu, 0.1-6%
Of M (where M is one or more of Mn, Ti, Zr, and Hf) and the balance substantially consists of Co, the primary sintering is performed at 1120 to 1200 ° C., which is the start of the liquid phase crystallization temperature. Then, a method for producing a rare earth permanent magnet, characterized by performing secondary sintering at 1140 to 1230 ° C and at a temperature 20 to 30 ° C higher than the primary sintering temperature. 2. A weight ratio of R of 22 to 27% (where R is one or more of rare earth elements Sm, Nd, Pr, Y and Ce),
10-25% Fe, 5-10% Cu, 0.5-6%
Of M (M is one or more of Mn, Ti, Zr, and Hf), and 0.003 to 0.015% B, 0.0
A liquid phase crystallization starting temperature of a magnet material containing 03 to 0.010% of P and 0.003 to 0.010% of S, which is one or two or more, and the balance of which is substantially Co. Is 11
Primary sintering at 20-1200 ° C., followed by 1140-1
A method of manufacturing a rare earth permanent magnet, which comprises performing secondary sintering at a temperature of 230 ° C and 20 to 30 ° C higher than the primary sintering temperature.