JPS62218514A - Heat treatment of permanent magnet material - Google Patents

Abstract

PURPOSE:To obtain permanent magnet material superior in magnetic characteristic such as coersive force, residual magnetic flux density and energy product, by sintering and solid soln. heat treating rare earth Co intermetallic compd. having a prescribed component compsn., then rapidly cooling, next, repeating heat treatments composed of heating and cooling at range between prescribed temps. at >=2 times. CONSTITUTION:Rare earth Co intermetallic compd. composed of by weight 22-26% R (one kind or more among rare earth element), 2-10% Cu, 6-35% T (one kind or more among Fe, Ni, Mn and Cr), 0.5-6% M (combination of Zr and/or Hf and one kind or more among Ti, Nb, V and Ta) and the balance Co is treated as follows. Namely, the intermetallic compd. is sintered and soln. heat treated at >=1,000 deg.C, then rapidly cooled to 750-950 deg.C generally about by 1-300 deg.C/sec rate. Next, the compd. at the temp. is subjected to heat treatment in which it is cooled to <=700 deg.C at >=2 times. Thereby, the titled material having magnet characteristic improved markedly compared with conventional ageing treatment in high Fe quantity and low Cu quantity is obtd.

Description

Detailed Description of the Invention ■ Background Technical Field of the Invention The present invention relates to R2C0.7-based Cu substitution precipitation hardening which is mainly composed of an intermetallic compound of Co and a rare earth element R consisting of one or more of the cerium group and the yttrium group. The present invention relates to a method for heat treatment of permanent magnet materials of molds.

Prior art and its problems By weight percentage, 22-28% of R (R is one or more rare earth elements), Co, Cu, one or more of Fe, Ni, Mn and Cr, Zr, Ti, Hf, Nb, V
A rare earth cobalt-based R2C0. , Cu substitution precipitation hardening type permanent magnets are known.

This magnet has residual magnetic flux density (Br), coercive force (bHc,
i Hc) is large, the energy product (B-H) max is large, and the Curie temperature is high, making it a permanent magnet with excellent temperature characteristics.

To manufacture such permanent magnets, a compound is prepared by a known reduction-diffusion method or dissolution method, and then subjected to solution treatment, aging treatment, pulverization, and magnetic field orientation to form rubber or plastic compounds. By using resin as a binder to make powder molded magnets, or after crushing the compound,
Magnetic field forming is performed, followed by sintering and solution treatment, followed by aging treatment to form a sintered magnet.

In such a case, R2C0. The aging treatment of Cu-substituted magnets of the . Since the state of this precipitation and phase separation greatly affects the performance of the magnet, it is important to perform this aging treatment under optimal conditions.
This is an extremely important point in manufacturing.

Conventionally, aging treatments for R2C0.7-based Cu substitution precipitation hardening magnets include multi-stage aging from 700 to 900°C to around 400°C (Japanese Patent Application Laid-open No. 133106/1983), A method of gradually cooling from a temperature of about 400° C. (Japanese Unexamined Patent Publication No. 106624/1983) is known.

However, with these conventional aging treatments, it has not yet been possible to obtain sufficiently satisfactory magnetic properties in terms of coercive force, residual magnetic flux density, energy product, hysteresis curve squareness ratio, magnetization properties, etc. In particular, 10 wt% or less,
In particular, it is desired to improve the magnetic properties in a low-cost practical magnet material composition with a low Cu content of 8 wt% or less and a high Fe content of 6 wt% or more, particularly 10 wt% or more.

That is, to explain more specifically, these low Cu
In a practical magnet material composition with a high Fe content, approximately 12 KG of Br can be obtained by applying a conventionally known aging treatment.
Although a (B-H)max value of 30 MGOe or more is expected, the squareness is poor and the expected (B-H)max
The value cannot be changed. In this case, with a composition with a Cu content slightly less than 10 wt%, a (B-H) fflax value that is only about 1 to 2 MGOe smaller than the expected (B-H) max value can be obtained, but with conventional aging treatment, , it is not possible to realize an increase in the energy product of 1 to 2 MGOe, which causes serious problems in practical use.

Note that when the amount of Cu is reduced to about 2 to 3 wL%, Br is also extremely reduced by the conventional aging treatment method, and a magnet that can withstand practical use cannot be realized.

Furthermore, the conventional aging treatment of rare earth cobalt-based materials is
It is necessary to take a long holding time at the aging start temperature and end temperature, and there is also a drawback that the aging time is long.

In addition, in the conventional aging treatment of rare earth cobalt-based materials, attention is focused only on the method of controlling cooling, and there is no example of repeated heating and cooling multiple times.

Furthermore, JP-A-57-161044 discloses that primary sintering and secondary sintering are performed, and after isothermal treatment, cooling is performed from a higher temperature. However, this method is extremely complicated in that sintering must be performed twice, leading to an increase in the cost of the product. Also, the squareness ratio of the demagnetization curve is insufficient.

Furthermore, the aging treatment method is different from the aging treatment method of the present invention in that after isothermal treatment at a low temperature, the next aging treatment is performed at a raised temperature.

■ Purpose of the Invention The present invention was made in view of the above circumstances, and its main purpose is to improve magnetic properties such as coercive force, residual magnetic flux density, energy product, squareness ratio, and magnetization characteristics. Fe amount,
At a low Cu content, R2C0.
An object of the present invention is to provide a heat treatment method for Cu-based permanent magnet materials.

Such objects are achieved by the invention described below.

That is, the present invention contains, in weight percentage, 22 to 28% R (R is one or more rare earth elements), 2 to 10% Cu, and 6 to 35% T (T is F
one or more of e, Ni, Mn and Cr), 0.6
~6% M (M is Zr and/or Hf and Ti.

After sintering and solution treatment of a rare earth cobalt-based intermetallic compound having a composition consisting mainly of Nb, V and Ta (combination with one or more of Nb, V and Ta), and the remainder being Co, it is rapidly cooled and then heated to 750 to 950°C. This is a heat treatment method for a permanent magnet material, which is characterized in that a heat treatment of cooling from a temperature of

Note that the method for manufacturing a permanent magnet described in Japanese Patent Application Laid-Open No. 58-219704, which is an earlier application of the present application, involves multi-stage aging of the same type as the present invention, but the R2C0I7-based material is
and/or has only Hf as a constituent element,
This is different from the present invention, which contains one or more of Ti, Nb, V, and Ta as essential components in addition to Zr and/or Hf.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

In the heat treatment method of the present invention, the sintered alloy is subjected to solution treatment prior to multiple heat treatments for aging.

During solution treatment, even if bath treatment is performed after sintering,
Solution treatment and sintering may be performed at the same time or both.

Sintering and solution treatment are preferably performed at 1000°C or higher. This is because the squareness of the hysteresis curve and the coercive force decrease below 1000°C.

In such cases, solution treatment is usually carried out at 1000°C to 1
It is applied at 200°C for about 0.5 to 10 hours.

After solution treatment, the material is rapidly cooled.

This rapid cooling is generally performed at a cooling rate of 1 to b. Then, the rapid cooling may be performed to any temperature below the first cooling start temperature of 750 to 950°C.

Thereafter, if necessary, heating is performed to a cooling start temperature for a predetermined heat treatment, and then heat treatment is performed a plurality of times.

That is, each heat treatment performed multiple times is 750 to 9
It consists of a cooling process from a cooling start temperature of 50°C to a cooling end temperature of 700°C or less.

By repeating such heat treatment two or more times, the desired effects of the present invention are achieved.

In this case, the number of repetitions may be any number of times as long as it is two or more times, but from the viewpoint of shortening the aging treatment time, it is preferably 2 to 4 times.

The cooling start temperature each time may be different from each other, but is 750 to 950°C, preferably 780 to 920°C.
It is ℃.

If the cooling start temperature is less than 750°C, precipitation hardening will be insufficient, and if it exceeds 950°C, the precipitated particles will become coarse and the coercive force will decrease, which is unsuitable.

The cooling end temperature for each round may be different, but is 700°C or less.

If the cooling end temperature exceeds 700° C., the precipitated particles may become coarse, or precipitation hardening may become insufficient, resulting in a decrease in coercive force, which is not preferable.

In this case, if the cooling end temperature is in the range from 600° C. to room temperature, particularly in the range from 500° C. to room temperature, more favorable results will be obtained in terms of improved magnetic properties. Note that such improvement in characteristics becomes greater as the cooling end temperature is lowered, but the effect remains almost unchanged below 400°C.

There is no particular limit to the cooling rate each time, but usually,
0.05-b or 2-b In this case, the cooling profile may be multi-stage cooling in which the temperature is once maintained, or continuous cooling in which the cooling rate is changed as needed. However, in order to shorten the aging treatment time, continuous cooling is preferable, and in particular,
It is preferable to reduce the cooling rate at the final stage compared to the initial stage.

Note that the optimum conditions for the cooling profile can be easily determined through experiments depending on the difference in composition and the like.

Furthermore, although the heating profile for each heat treatment time is arbitrary, it is usually set to 2 to b degrees.

Note that it is preferable to provide a holding time at the cooling start temperature. The holding time is usually about 5 minutes to 20 hours, preferably 10 minutes to 6 hours. This holding time is determined empirically based on a combination of the number of repetitions, cooling rate, etc.

On the other hand, at the cooling end temperature, it is not necessarily necessary to provide a holding time.

The composition of the permanent magnet material subjected to such heat treatment multiple times is as described above.

In this case, the rare earth element R contained in the range of 22 to 28 wt% may be one or more of cerium and yttrium, but it is particularly preferable to include samarium or cerium.

Moreover, the content of Cu is 2 to 10 wt%.

Otherwise, the effectiveness of the present invention will be reduced.

In this case, the Cu content is 2.5 to 8 wt%, especially 3 to 8 wt%.
At 7.5 wt%, the rate of increase in magnetic properties compared to conventional aging treatment becomes extremely large. As a result, a magnet with extremely good magnetic properties is realized. Furthermore, Fe.

T of one or more of Ni, Mn, and Cr is contained in an amount of 6 to 35 wt%. If the T content is other than this, the effectiveness of the present invention will be reduced.

In this case, T contains Fe as an essential element, and if necessary, one or more of Ni, Mn, and Cr is included to obtain more preferable results. And the Fe content is 10 to 25
When it becomes wt%, especially 14 to 25 wt%, the rate of increase in magnetic retention compared to conventional aging treatment becomes extremely large, and a magnet with extremely good magnetic properties is realized.

In addition, the permanent magnet material in the present invention contains Zr and/or Hf, Ti, and Nb.

(2) M, which is a combination with at least one of Ta and Ta, is contained in an amount of 0.5 to 6 wt%.

If the M content is outside this range, the magnetic properties will deteriorate. In addition to Zr and/or Hf, Ti,
By containing at least one of Nb, V and Ta, residual magnetic flux density (Br) and coercive force (b
Hc.

f Hc) is large, and the energy product ((B-H)max
) and a high Curie temperature, making it possible to create a magnet with excellent temperature characteristics.

In order to manufacture a permanent magnet using such a heat treatment method of the present invention, a compound is crushed, subjected to magnetic field molding, then subjected to sintering and solution treatment, rapidly cooled, and then subjected to multiple heat treatments of the present invention. administer.

A sintered magnet is thereby formed.

(2) Specific Effects of the Invention According to the present invention, magnetic properties such as coercive force, residual magnetic flux density, energy product, squareness ratio, and magnetization properties are improved compared to when conventional aging treatment is performed.

That is, in a practical magnet material composition with a low Cu content of 10 wt% or less and a high Fe content, magnetic properties that are sufficiently satisfactory for practical use can be obtained.

In this case, in a Cu amount range relatively close to 10 wt%, for example 4 to 10 wt%, especially 4 to 8 wt%, the squareness can be improved while keeping Br equal to or higher than conventional aging treatment. , the coercive force improves, so the expected (B-H)
The max value can be changed, and the characteristics are sufficiently satisfactory for practical use.

In addition, it is possible to obtain a lower Cu composition, for example, 2 to 4 wt%, especially 2.5 to 4 wt%, which is completely unusable with conventional aging treatment.
At 4 wt%, both Br and coercive force increase at an extremely high rate, and as a result, the properties are still sufficiently satisfactory for practical use.

Furthermore, in each cooling process, the holding time at the cooling start or end temperature can be made shorter than before, and overall the aging treatment time can be made shorter than before.

Furthermore, there is no need to perform sintering twice.

■Specific embodiments of the invention Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Weight percentage: 24.5% Sm, 5% Cu, 15% Fe
, 1.0%Zr10.5%Hf.

An alloy consisting of 0.5% Ti and the remainder Co was produced by high frequency induction melting.

Next, this was coarsely crushed using a show crusher and finely crushed using a jet mill. This is molded in a magnetic field, and 1
Sintering and solution treatment were carried out at 200° C. for 1 hour, followed by cooling to room temperature.

This is set in a profile as shown in FIG. 1, with a cooling start temperature T4 and a cooling end temperature 1. The heat treatment was repeated twice by changing T and tl.

Figure 3 shows the relationship between iHc and T1, and Figure 4 shows the relationship between iHc and t.
The relationship with , is shown by a solid line.

In addition, Fig. 3 and Fig. 4 show the profile of the conventional multi-stage aging treatment shown in Fig. 2, when the holding times are a = 2Hr, b = IHr, and c = IHr. The result is shown by the dashed line.

From these results, it is clear that the present invention is effective in performing predetermined aging heat treatment two or more times.

Moreover, TI is 750 to 950°C, 1. It can also be seen that the temperature is preferably 700°C or less.

Furthermore, it can be seen that the total aging treatment time is also shortened.

Example 2゜ As in Example 1, the alloy No. shown in Table 1.

I got 1-8.

After crushing, sintering, and solution treatment in the same manner as in Example 1, the following heat treatments A, B, and C were applied to samples IA to i.
I got oc.

A: In the profile shown in Figure 1, T, = 850°C, t, = 400°C.

B: In the three profiles in Figure 5, T = 90
0°C, T2=850°C, T3=800°C, t,=soo°C, t2=450°C, t3=400°C.

C: In the one-time profile shown in Figure 2, T, =
850°C, t, = 400°C, a = 6Hr, b = IHr,
When c=4Hr.

Magnetic properties of samples IA-IOC, Br.

Table 2 shows i Hr , (B - H) max and magnetization rate. In this case, the magnetization rate is the value obtained by dividing the value of Br at the time of magnetization by applying Oe to 15 by the value of Br at the time of complete magnetization.

Further, Table 2 shows the increase rate of each of these characteristics with respect to treatment C.

From the results in Table 2, the effects of the present invention are clear.

In addition, the alloy N0. of the present invention. Samples No. 1 to No. 7 treated with A and H are alloy No. 1 to which Zr is added alone. 8 shows magnetic properties comparable to those of the samples treated with A and B.

Comparative Example Alloy powder with the same composition as Example 1 was molded using a magnetic field press,
This is heated in an argon stream depending on the Cu content.
180-1,210'C for 30 minutes, then 1,190'C
Sintering at ~1,220"C for 1 hour, then isothermal treatment at 650°C for 1 hour, then sintering at 3°C with a starting temperature of 800°C.
The alloy was continuously cooled to 400 t' at a cooling rate of 0.1 DEG C./min, and the squareness ratio of the alloy (comparative example) thus obtained according to JP-A-57-161044 was measured.
The squareness ratio is expressed as )(, /IHc, H, is BrX0.9
is the value of H on the I-8 curve at the point. The results are shown below along with the samples of the invention.

Sample No.0. Squareness ratio (%) IHC (koe)
Comparative example 90 7.2

[Brief explanation of drawings]

FIG. 1 is a graph of a one-hour temperature profile showing an example of the heat treatment method of the present invention. FIG. 2 is a graph of a one-hour temperature profile showing an example of a conventional heat treatment method. FIGS. 3 and 4 are graphs of the coercive car T1 and the coercive car t1 when T and t of the profiles of FIGS. 1 and 2 are changed, respectively. In this case, in FIGS. 3 and 4, the solid line corresponds to the profile in FIG. 1, and the broken line corresponds to the profile in FIG. 2. FIG. 5 is a graph of a one-hour temperature profile showing another example of the heat treatment method of the present invention.

Claims (1)

[Claims] 1. In terms of weight percentage, 22-28% R (R is one or more rare earth elements), 2-10% Cu, 6-35% T (T is one of Fe, Ni, Mn and Cr). ), 0.5 to 6% M (M is a combination of Zr and/or Hf and one or more of Ti, Nb, V and Ta), with the remainder being Co. A permanent magnet characterized in that a rare earth cobalt-based intermetallic compound is subjected to sintering and solution treatment, then rapidly cooled, and then subjected to heat treatment of cooling from a temperature of 750 to 950°C to a temperature of 700°C or less twice or more. Methods of heat treatment of materials. 2. The method of heat treating a permanent magnet material according to claim 1, wherein the Cu content is 2.5 to 8%. 3. T consists of Fe or a combination of Fe and one or more of Ni, Mn and Cr, and the Fe content is 10
25%. The method of heat treating a permanent magnet material according to claim 1 or 2, wherein the heat treatment method is 25%. 4. The method of heat treating a permanent magnet material according to any one of claims 1 to 3, wherein the sintering and solution treatment temperatures are 1000° C. or higher. 5. Any one of claims 1 to 4, wherein the quenching end temperature after sintering and solution treatment is within the temperature range from the first cooling start temperature of 750 to 950°C to room temperature. A method for heat treatment of permanent magnet materials described in . 6. The method of heat treating a permanent magnet material according to any one of claims 1 to 5, wherein the cooling end temperature of each cycle is within a temperature range from 650°C to room temperature. 7. The method of heat treating a permanent magnet material according to any one of claims 1 to 6, wherein the heat treatment is repeated 2 to 4 times. 8. The method for heat treating a permanent magnet material according to any one of claims 1 to 7, wherein a holding time of 5 minutes to 20 hours is provided at each cooling start temperature. 9. The method for heat treating a permanent magnet material according to any one of claims 1 to 8, wherein the cooling rate for each cooling step is 0.05 to 15° C./min.