JPH01164007A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To produce a permanent magnet with a high coercive force, by a method wherein a starting material employs a permanent magnet alloy consisting of a predetermined amount of gallium and the balance iron, and after the alloy is pulvierized, shaped and sintered, special aging treatments are performed. CONSTITUTION:A starting material employs a permanent magnet alloy having a composition which consists of 10-40wt.% R (but, R is at least one kinds of elements which are selected from Y and rare earth elements), 0.1-8wt.% boron, less than 13wt.% gallium, and the balance mainly consisting of iron. After the permanent magnet alloy is pulverized, shaped and sintered, a first step of aging treatment from 550-1200 deg.C to below 400 deg.C is performed, and a second step of aging treatment from 500-750 deg.C to below 400 deg.C is then repeated two times. When R is less than 10wt.%, increasing of Hc is not achieved while R is more than 40wt.%, Br is decreased, and therefore in any case, (BH)max is decreased. Now, among rare earth elements, especially, both Nd and Pr are an available element in order to obtain a high (BH)max, and therefore said R is preferred to contain at least one kinds of elements which are selected from these two elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a permanent magnet, and is particularly used for manufacturing rare earth iron-based permanent magnets.

(Prior Art) Conventionally known rare earth magnets include RCo type, R1 (Co, Cu, Fe, M) 0. Type (however.

R is a rare earth element such as Sm or Cs, M is Ti, Zr,
Rare earth cobalt-based materials such as transition elements such as Hf are known. However, this type of permanent magnet has the problem that the maximum energy product is limited to about 30 MGOa, and a large amount of relatively expensive CO must be used.

In recent years, instead of the above-mentioned rare earth cobalt-based permanent magnets, relatively inexpensive rare-earth iron-based permanent magnets have been studied (Japanese Unexamined Patent Publication No. 1983-1999).
46008 etc.). This is made of constituent elements such as Nd-Fe-B, and is a very effective material because it not only reduces cost by using Fe, but also provides a maximum energy product exceeding 30 MGOe.

However, this rare earth iron-based permanent magnet has poor magnetic properties, particularly the temperature characteristics of coercive force, and from the viewpoint of magnet stability, etc., it has been desired to increase the coercive force.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above points, and an object of the present invention is to provide a rare earth iron-based permanent magnet having a high coercive force.

[Structure of the invention]

(Means and effects for solving the problems) ゛As a result of intensive research by the present inventors to solve the above problems, we found that Ga
It has been discovered that a high coercive force can be obtained in a permanent magnet containing rare earth iron, and that an even higher coercive force can be obtained by special aging treatment.

The present invention was made based on this, and 10 to 4
0% by weight of R (however, R is at least one selected from Y and rare earth elements), 0.1 to 8% by weight boron, 1
A first stage aging treatment from 550 to 1200°C to 400°C or less after pulverizing, forming and sintering a permanent magnet alloy characterized by having a composition consisting of 3% by weight or less of gallium and the balance mainly consisting of iron. After that, from 500 to 750℃ to 400℃
The second stage aging treatment at temperatures below 0.degree. C. is repeated two or more times.

In the present invention, the content of each element is limited to the above range for the following reasons.

If R is less than 10% by weight, 1) an increase in Ic cannot be obtained;
If it exceeds 0% by weight, Br decreases, and therefore (BH)+-a decreases in any case.

The content of R is 10 to 40% by weight. Note that among the rare earth elements, Nd and Pr are particularly effective elements for obtaining a high (BH)m□, and it is preferable that at least one of these two elements be contained as R.

It is desirable that the proportion of Nd and Pr in the R amount is 70% or more (or the entire R amount may be sufficient).

When boron (B) is less than 0.1% by weight, t)(c decreases,
When it exceeds 8% by weight, the Br decreases significantly. Therefore,
The boron content is 0.1 to 8% by weight. Note that a part of B may be replaced with C, N, Si, P, Ge, or the like. This improves sintering properties and thus Br.

(BH) Saw can be increased. In this case, it is desirable that the amount of substitution is up to 80% of B.

Gallium (G(1)) is an effective element for improving coercive force, but when it exceeds 13% by weight, the Br decreases significantly.Additionally, a small amount of addition has the effect of improving iHe, but it is not practical. It is preferably 0.1% by weight or more.

Although cobalt (Go) is not an essential component, it is an effective element for increasing the Curie temperature and, by extension, for improving the temperature characteristics and corrosion resistance of magnets. However, 30% by weight
If it exceeds this value, the decrease in lHc and the deterioration of squareness will become significant. Therefore, the content of cobalt is preferably 30% by weight or less. A small amount is effective in improving Tc, but in practice, it is preferably 1% by weight or more.

Furthermore, the oxygen content in the permanent magnet alloy used in the present invention is 0.
．． The content is preferably 0.3% by weight or less.

Aging treatment is important in the present invention.

The aging treatment temperature in the first stage is less than 550℃ and 1200℃
When the temperature exceeds ℃, the squareness deteriorates. Furthermore, if the second stage aging treatment temperature is less than 500°C or more than 900°C, the coercive force will decrease.

Therefore, the temperature of the first stage aging treatment is 500°C or higher and 120°C.
The temperature is 0°C or lower, then the temperature is 400°C or lower, and the second
The aging treatment temperature for the stages is 500 to 900°C.

By performing this second stage aging twice or more, a higher coercive force can be obtained in a shorter time.

The method for producing a permanent magnet according to the present invention will be explained in more detail below with reference to Examples.

(Example) A magnetic alloy consisting of 31.3% by weight of neodymium, 1.3% by weight of boron, 14.1% by weight of cobalt, 1.0% by weight of gallium, and the balance iron was created by arc melting in an argon atmosphere. did.

The obtained permanent magnet alloy was coarsely pulverized in an Ar atmosphere, and further finely pulverized to an average particle size of 37 m in a nitrogen atmosphere using a jet mill.

This fine powder was filled into a predetermined press die and compression molded at a pressure of 2 tons/a& while applying a magnetic field of 200,000 e. The obtained molded body was sintered in vacuum at 1080° C. for 1 hour and rapidly cooled to room temperature. Thereafter, a first aging treatment was performed at 900° C. for 1 hour in a vacuum, and then rapidly cooled to room temperature. Further, the material was reheated to 600° C. in a vacuum, subjected to an aging treatment for 1 hour, and the second aging treatment, in which the material was rapidly cooled to room temperature, was repeated three times. This was designated as sample 1.

A magnet was produced in the same manner as Sample 1, except that the second aging stage was 600°C, continuous holding for 10 hours, and then quenching. This was designated as sample 2. The magnetic properties of each sample are shown in Table 1.

Table 1 As is clear from Table 1, multi-stage aged blood 1 has a larger coercive force.

Late Emperor Gol 32.0% by weight of neodymium, 14.6% by weight of cobalt.

Sintering was performed in the same manner as in Example 1 using a permanent magnet alloy consisting of 1.6% by weight of boron, 1.0% by weight of gallium, and the balance iron as a starting material. Thereafter, first stage aging was performed at 900° C. for 1 hour and cooled to room temperature. Furthermore, the process of reheating to 600° C. in vacuum, holding for 2 hours, and cooling to room temperature was repeated 10 times. This was designated as sample 3.

A magnet was produced in the same manner as Sample 3, except that the second aging was carried out at 600° C., continuously held for 20 hours, and then rapidly cooled. This was designated as sample 4.

For Sample 3, the coercive force was measured after each repeated cooling after the completion of the second stage aging, and for Sample 4, the coercive force was measured after the completion of the second stage aging. The results are shown in FIG.

As is clear from Figure 1, sample 3 was obtained by the repeated aging method.
In this case, the highest coercive force was reached after an aging time of 4 hours.
This coercive force is larger than the final coercive force of Sample 4.

Nd 31.0% by weight, Boron 1.2% by weight, Gallium 1
．． Sintering was performed in the same manner as in Example 1 using an alloy consisting of 0% by weight and the balance iron as a starting material.

Thereafter, first stage aging was performed at 900° C. for 1 hour and cooled to room temperature. Furthermore, the process of reheating to 600° C. in vacuum, holding for 2 hours, and cooling to room temperature was repeated six times. This was designated as sample 5.

A magnet was produced in the same manner as Sample 5, except that the second aging was carried out at 600° C., continuously held for 12 hours, and then rapidly cooled. This was designated as sample 6.

The magnetic properties of these samples are shown in Table 2.

Table 2 [Effects of the Invention] According to the present invention, a permanent magnet having a large coercive force can be obtained with short aging, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the aging time dependence of coercive force. Agent: Patent Attorney Noriyuki Chika Same as Mitsuyuki Matsuyama

Claims (3)

[Claims] (1) Consisting of 10-40% by weight of R (R is at least one selected from Y and rare earth elements), 0.1-8% by weight of boron, 13% by weight or less of gallium, and the balance is iron. A permanent magnet alloy having the following composition is used as a starting material, and after pulverizing, forming, and sintering the alloy, a first stage aging treatment is performed in which the alloy is cooled from a temperature of 550 to 1200 °C to 400 °C or less,
A method for manufacturing a permanent magnet, which comprises subsequently performing a second stage aging treatment consisting of cooling from a temperature of 500 to 750°C to 400°C or less twice or more. (2) The method for producing a permanent magnet according to claim 1, wherein the permanent magnet alloy contains 30% by weight or less of cobalt. (3) Claims 1 to 2, characterized in that the permanent magnet alloy contains 0.1% by weight or more of gallium.
2. Method for manufacturing permanent magnets described in Section 1.