JPS61238938A - Sintering method for permanent magnet alloy - Google Patents

Abstract

PURPOSE:To manufacture a permanent magnet alloy having high maximum energy product and excelling in magnetic properties by subjecting an alloy containing as essential components rare earth elements, B and Fe to crushing, compacting, heating and holding under specific conditions and then cooling. CONSTITUTION:The alloy consisting of, as essential components, about 8-30atom% R (at least one element among rare earth elements including Y), about 2-28atom% B, and the balance Fe with inevitable impurities is crushed to about 0.34-80mu average grain size and compacted under a pressure of about 0.5-10t/cm<2>. The green compact is subjected to temp. raise from ordinary temp. in vacuum or in an inert gas (Ar etc.) or reducing gas (H2 etc.) and then to heating and holding at 900-1,200 deg.C in an H2 gas atmosphere, followed by cooling in vacuum or in an inert gas (Ar etc.) at a rate of about 0.5-100 deg.C/min.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for sintering an R-B-Fe-based permanent magnet alloy, and in particular to a method for sintering a permanent magnet alloy that is effective in improving the maximum energy product (BH) max. The present invention relates to a sintering method.

(Prior Art) In recent years, magnetic alloys, that is, R-B-Fe-based permanent magnet alloys, have been developed that do not contain expensive am and Co and have magnetic properties that exceed those of conventional Sm-Go-based permanent magnet alloys. Invented. According to JP-A-59-46008 and JP-A-59-217504, as an atom,
An alloy powder consisting of 8 to 50 inches of R, 2 to 28 inches of B, and Fe containing unavoidable impurities is pressurized and sintered at 900 to 1200°0 in a reducing or non-oxidizing atmosphere. This is disclosed. For example, 1O-2 TOrr
Sintering is carried out at a temperature of 900 to 1200° C. for a predetermined period of time in the following vacuum or under a pressure of 1 to 760'rorr in an atmosphere of an inert gas or reducing gas with a purity of 99.9 volume or more. In addition, as an example of the sintering atmosphere, 200 to 76
Only Ar gas at 0'rorr is disclosed.

(Problems to be Solved by the Invention) However, with these conventional sintering methods, the squareness of the knee H curve is poor and the characteristics are sufficiently satisfactory in terms of magnetic properties, especially the maximum energy product ((BH) MAX) has not yet been achieved.

It is an object of the present invention to provide a sintering method capable of solving the problems of the prior art described above and obtaining an R-B-Fe-based permanent magnet alloy with a high maximum energy product and excellent magnetic properties. It is something.

(Means for Solving the Problems) The method for sintering a permanent magnet alloy of the present invention includes R(
After pulverizing and forming a permanent magnetic alloy consisting of B and Fe (at least one rare earth element containing Y), the temperature is raised from room temperature in a vacuum, in an inert gas such as AI-, or in H2
It is characterized by being heated and held at 900 to 1200°O in a H2 gas atmosphere, and then cooled down after being heated and held in a vacuum or in an inert gas such as Ar. be.

(Function) To explain in detail below, alloy powder (average particle size 0.3 to 80 μm) of R-B-Fe-based permanent magnet alloy having predetermined components,
Bath melting-casting and known crushing means (e.g. 1-crusher, Brown mill).

This is because if the thickness is less than 0.3 μm, the residual magnetic flux density Br decreases, and if it exceeds 80 μm, the coercive force He decreases. The composition of the alloy powder is 8 to 30% R (rare earth metal containing Y), 2 to 2% by atomic percentage.
8% B and Fe containing unavoidable impurities are essential components, and one or more of the following specified elements (however, if two or more types are included, the total amount of element A is determined by the amount of the element in question) (within the maximum value).

The rare earth element R needs to be at least 8 inches in terms of coercive force, and is combustible and still expensive due to industrial handling and manufacturing difficulties, so it is set at less than 30 inches. If B is less than 2%, coercive force cannot be obtained, and if it exceeds 28 inches, Br decreases, so the range is set to 2 to 28 inches. In addition, the addition of less than the specified amount of element A (however, when two or more types of elements are included, the content of element A is less than or equal to the value of the one with the maximum value among the contained A elements) does not impair the effects of the present invention. .

The alloy powder described above is molded and compacted using a compression press or the like.

In addition, the above-mentioned molding-consolidation is 0,5-10 t/c!
The It9 molding pressure is good, and the magnetic properties can be improved by applying a magnetic field (5 KOe or more) during molding if necessary. The series of molding and compaction may be performed wet or dry, and may be performed at a high temperature other than room temperature. The atmosphere is preferably a non-oxidizing atmosphere, and may be carried out, for example, in a vacuum, an inert gas, or a reducing gas. The obtained molded body is sintered at a temperature of 900 to 1200°0. 900
This is because if the temperature is less than 'O, the density does not increase, so Br is not sufficient, and if the temperature exceeds 1200°C, Br and squareness deteriorate. H2 gas is preferable as the atmosphere for heating and holding at 900 to 1200°C. It is thought that by using H2 gas, the oxides present in the compact are reduced and at the same time the surfaces of the alloy particles are chemically activated, further promoting densification and thus improving the magnetic properties.

Note that the rate of temperature rise from room temperature is not particularly specified, but
By holding the temperature in the temperature range of 00-800'0 for at least 5 hours, it becomes possible to improve the temperature uniformity of the heated part and to perform degassing treatment in a vacuum.

Alternatively, cranking (hydrothermal decomposition method) of stearate used as a lubricant can also be performed in a hydrogen gas atmosphere. Therefore, the atmosphere for raising the temperature is preferably a vacuum or a non-oxidizing atmosphere such as an inert gas (for example, Ar) or a reducing gas (for example, H). The cooling rate after heating and holding is not particularly specified, but is 0.5 to 1000
/min is good, generally 1-10゛0/min is good. This is because by slowing down, variations in magnetic properties due to subsequent heat treatment are reduced. Further, cooling may be performed once to room temperature, or sintering and heat treatment may be performed continuously, such as cooling to 500° 0 value and raising the temperature again for the next heat treatment. However, 900-1200
In the case of heating and holding at ℃ as in the present invention (in a Hz gas atmosphere, during the cooling process.

At least the atmosphere must be such that the H2 removal process can be performed, that is, a vacuum or an inert gas such as Ar.

The reason for this is that the rare earth FeCo compound easily absorbs hydrogen gas. If H2 gas is used during cooling, the sintered body will absorb hydrogen gas and collapse after cooling.

After the above sintering, in order to further improve the magnetic properties, 55
Aging treatment is performed at 00 to 700°C, but if necessary, an intermediate heat treatment of holding and slow cooling at SOO to 1000°C is performed before aging to further improve the magnetic properties. By carrying out the above-described sintering method according to the present invention, the magnetic properties, particularly the maximum energy product (BH) ms, are improved compared to conventional methods.

(Example) The present invention will be described in detail below, but the following examples do not limit the present invention.Example Purity: 99. 'Wt Chi's electrolytic iron, 99wt Chi's B, 9
Using 9.7% Nd, the atomic composition was Nd (Fe0.0
An alloy ingot of 1 Bo, 09) 5.8 was obtained. The above ingot was coarsely crushed using a Jian crusher, a brown crusher, and a mill, and then a jet and a mill with an average particle size of 55 μm.
m finely pulverized powder. The obtained fine powder was used as a molding raw material and filled into a molding space formed by a die and upper and lower punches, and pressed in a magnetic field (1 oxoe) at a molding pressure of 3 t/d. The obtained molded body was sintered by the sintering method shown in Table 1 and Figures 1 to 6, heated at 900° for 2 hours, slowly cooled to room temperature at 2'C/night, and heated again at 600°C. 2
After being heated and maintained at Hr, it was rapidly cooled to room temperature (oil cooling) and subjected to magnetic measurement. The sample shape is 10x10x10-. All heat treatments other than sintering were performed in Ar gas.

The results of magnetic properties are shown in Table 1.

Sample-1 (Comparative Example 1) was sintered using the following sintering method (Fig. 1):
After heating at 5°0/min and processing at 1080°0X2Hr, 4
It was cooled at ゛C/min, and the atmosphere was the same as the conventional method A.
It is r gas.

As can be seen from Margin Table 1 below ((BH) MAX = 38.8 MGOe.

Sample-2 (Comparative Example 2) was prepared at a sintering temperature of 10% as shown in Figure 2.
Everything was the same as -1 except that it was set to 50"0. As shown in Table 1, ((BH) MAX = 37.IMGOa, and as the sintering temperature decreased, the magnetic properties also decreased.

Sample-3 (Example 1) is the same as Sample-2, as shown in FIG. 3, except that the atmosphere for heating and holding was changed from Ar to H2. -2, the magnetic properties are (BH
) Improved to MAX41.5MGOe. -4 (Comparative example 5
) is the same as -6 except that the atmosphere during cooling was changed from Ar to H2, as shown in Figure 1X4. 114
could not maintain the desired shape after sintering. -5
(Example 2), as shown in FIG. 5, compared to Ik3,
The atmosphere during temperature rise was changed from H2 to vacuum (10””’ Torr).
) is the same except that it is changed to (BH)MAX
=4Q, 8MGOe was shown. Floor 6 (Example 6) is the 6th
As shown in the figure, compared to -2, it is the same except that the holding atmosphere was changed from Ar to H2, but (BH)MA
Xha 37.1 Kara 40.5MGOe To improvement L*.

As described above, according to the method of the present invention (Example 1, 2.3),
In particular, (BH) MAX exceeds 4 Q MGOe.

(Effect of the invention) The magnetic properties of the permanent magnet alloy obtained by the sintering method of the present invention are higher than those of the conventional method, and the maximum energy product (B
H) MAX is extremely large and its industrial value is great.

[Brief explanation of the drawing]

1, 2, and 4 are diagrams showing patterns according to the conventional sintering method, and FIGS. 5, 5, and 6 are diagrams showing patterns according to the sintering method according to the present invention.゛・Milli・1st self878＼12N 5th eye 5th figure 2ﾓta, ncx;s Bird 41 month tlj7j 'cme 2H Cause

Claims (1)

[Claims] 1. After pulverizing and forming an alloy consisting of R (at least one rare earth element including Y), B, and Fe as essential elements, the temperature is raised from room temperature in a vacuum or under an inert gas. A method for sintering a permanent magnet alloy, the method comprising: heating and holding at 900 to 1200°C in an H_2 gas atmosphere; and cooling after heating and holding in a vacuum or inert gas. . 2. A method for sintering a permanent magnet alloy according to claim 1, characterized in that Ar is used as the inert gas.