JPH03167803A - Manufacturing method for rare earth permanent magnets - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an intermetallic compound magnet containing Nd and Fe as main components, particularly a Nd-Fe-B rare earth permanent magnet.

(Prior art) R-Fe-B rare earth permanent magnets have higher magnetic properties than R-C;o rare earth permanent magnets, and have a maximum energy product (
Below, (BH). ．． ．． ), Nd+IIFe
The ytB s composition has reached ~35MGOe, and 37MGOe magnets are now available at the mass production level, and currently 40MGOe.
Something beyond GOe is being developed. These R-Fe
- The raw material powder for powder metallurgy of the B-based magnet alloy is very easily oxidized, so when crushing the ingot, it must be placed in a non-oxidizing gas such as N2 gas, an inert gas such as argon, or hexane, etc. to prevent oxidation. It is carried out in an organic solvent. Furthermore, according to JP-A-1-119001, a molten rare earth permanent magnet alloy is rapidly cooled to form an alloy ribbon, subjected to hydrogen embrittlement treatment, and a filled magnet is obtained after crushing, but the effect of improving magnetic properties is sufficient. There are some disadvantages. (Problem to be solved by the invention) However, even with the methods described above, oxidation prevention is not always sufficient, and the raw material powder may oxidize, resulting in a decrease in the magnetic properties of the product magnet or the inability to maintain a certain quality. There was a problem. These problems must be overcome in order to produce products with higher magnetic properties than current products.

(Means for Solving the Problem) In order to solve the problem, the present inventors have proposed that if a magnetic alloy ingot is transformed into a material having oxidation resistance and then finely pulverized to be used as a raw material for powder metallurgy, it will be oxidized. We have discovered that magnet powder, which has a relatively large specific surface area, is significantly involved in increasing oxygen concentration, and have arrived at the present invention. The summary is as follows. Composition formula RJ41100-x-y-JvMz (However, R is at least one or two or more elements among rare earth elements including Nd, M is AI, Co, Ga
, Nb, and Zr, at least one or two or more elements, X = 10 to 25% in atomic percentage, Y
= 1 to 20%, 2 = 0 to 20%) is exposed to a hydrogen atmosphere, hydrogenated, finely pulverized, and classified to obtain a magnetic alloy powder with a size of 2 μm or more and 50 μm or less, which is then compression molded. This is a method for manufacturing rare earth permanent magnets, which is characterized by sintering and heat treatment. The present invention will be explained in detail below. First, the magnet set or composition formula RgFe that is the subject of the present invention
+ o. R-Fe-B represented by -x-v-zBJz
system magnet alloy, R is at least one kind or two or more kinds of rare earth elements including Nd, and M is AI, Go, Ga.
, Nb, and Zr, and the composition ratio is X in atomic percentage.
: 10-25%, y=i-20%, 2=0-20%. If the composition falls outside this range, R-Fe-
The magnetic properties of B-based magnets, especially the residual magnetic flux density (hereinafter referred to as B
Satisfactory results were not obtained regarding coercive force (r) and coercive force (hereinafter referred to as iHc). Next, we will describe the method for preventing oxidation of the raw material powder for powder metallurgy, which is the most distinctive feature of the present invention, and of the magnet sintered body. As an additive element that stabilizes the RmFezB intermetallic compound, which is the main phase of this magnet composition, and maintains ferromagnetism, we focused on the absorption and release effects of hydrogen gas, and fully contributed to improving oxidation resistance by forming hydrides. It was found that this method is effective in reducing the oxygen concentration contained in the magnet sintered body. Furthermore, when a magnetic alloy ingot absorbs hydrogen, hydrogen embrittlement occurs.
Hydrogen gas enters through surface defects and microcracks,
It peeled off like an onion skin, and completely disintegrated into a coarse powder of about 200 μm in hydrogen absorption saturation. Therefore, the ingot coarse crushing step in the manufacturing process using conventional technology can be omitted. This hydrogen storage is carried out by placing a magnetic alloy ingot in a pressure-resistant container and storing it at 1 G-
After exhausting to a vacuum level of 'smog level, hydrogen gas is
It is pressurized to about atmospheric pressure and stored in an ingot. The pressure inside the container gradually decreases, and when it becomes almost a vacuum, hydrogen gas is again injected and occluded.If this process is repeated until 2,000 to 4,000 ppm of hydrogen gas is occluded in the ingot, the ingot becomes an onion. It begins to peel off in the form of a skin and gradually disintegrates to obtain a coarse powder of magnetic alloy hydride about 200 μm in size. Next, it directly enters the pulverization process. Fine pulverization is performed using jet mills, pole mills, etc. In order to prevent oxidation, both are carried out in a non-oxidizing gas atmosphere such as N-rich, but an inert gas atmosphere such as Ar or an organic solvent such as hexane may also be used. The powder obtained here is 0.1
It has a particle size distribution on the order of -100 μm, with a particle size distribution of 0.
Ultrafine powder on the order of 1 μm or less is easily oxidized because it has an extremely large specific surface area, and coarse powder on the order of 100 μm or more is undesirable because it causes a decrease in the density and degree of orientation of the sintered magnet. Therefore, it is classified to remove these particles. A good classification method for magnetic powder is a wind classifier that combines airflow and rotational force, which is effective for magnetic powder.The classification is performed at two points, the upper limit point and the lower limit point, in a nitrogen gas or argon gas atmosphere. For the reasons mentioned above, the particle size distribution of
It is preferable to have a particle size of 2 to 20 μm, and a raw material powder for powder metallurgy that is prevented from oxidation can be obtained. Permanent magnet molded bodies can be produced by powder metallurgy using known methods and conditions, and fine powder with a predetermined particle size distribution is used as a raw material, molded and heat-treated to produce a permanent magnet molded body. The molding is done by mold press molding, making it magnetic? It takes place inside. The molded body is then sintered by holding it at a predetermined temperature within the range of 1,000 to 1,200°C for 30 to 120 minutes in a vacuum, an inert gas such as argon or nitrogen, or a non-oxidizing atmosphere. ,
Furthermore, what is necessary is just to heat-process within the range of 350 degreeC - sintering temperature after that for 30 minutes - 4 hours.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Examples: Middle part and percentages are based on weight unless otherwise specified. (Example 1) As a starting material, Nd with a purity of 99.7% or more, purity 99
．． A ferroboron alloy containing 9% or more of electrolytic iron and 19.4% of B, with the remainder consisting of Fe and impurities such as Al, St, and C, is used. After high-frequency melting, these are cast into a copper mold to form Nd+4Fete. . An ingot with a composition of B6.6 was obtained. 1 kg of this ingot was placed in a 2012 stainless steel airtight container, sufficiently evacuated, and then hydrogen gas was sealed at 2 atm. The pressure inside the container gradually decreases, and when it reaches an almost vacuum state, hydrogen gas is further filled in.
The occlusion was repeated until finally about 804 ml of hydrogen gas was occluded in the ingot. Ingots that store hydrogen gas are
It no longer had the lumpy shape it had before treatment, but was in a state similar to a peeled onion, and had become brittle due to hydrogen.

Therefore, the conventional coarse pulverization step was omitted and the fine pulverization step was directly performed. Fine pulverization was performed using a jet mill in a nitrogen stream to obtain raw material magnet powder with an average particle size of about 3 μm. This raw material powder was fed into a wind classifier while being dispersed by the ejector effect, and classified in a nitrogen stream with classification points of 4 μm and 20 μm, resulting in a particle size distribution of 2 to 22
Raw material magnet powder of μm size was obtained. Next, a magnet sintered body was obtained by a normal magnet manufacturing process. The oxygen concentration and magnetic properties (Br, tHc, (BH)+max) contained in the sintered body were measured, and the results are shown in Table 1. For comparison, it was treated and measured in the same manner as in Example 1 except that it was not hydrogenated, and the results are shown in Table 1 (Comparative Example 1). (Example 2) As starting materials, Nd and oy with a purity of 99.7% or more,
Electrolytic iron with a purity of 99.9%, Co, B with a purity of 99.5%,
Using AI, these were high-frequency melted, then cast into a copper mold, and N(1+s.osDy+.4s Fet
n. sycOi. ssBaAlo. An ingot having a composition of t was obtained. The hydrogen gas storage amount was set to approximately 75β, and the classification points were set to 4μm and 25μm, resulting in the following results:
Raw material magnet powder was prepared by processing in the same manner as in Example 1, except that raw material magnet powder with a particle size distribution of 2 to 26 μm was obtained, a magnet packed body was obtained by a powder metallurgy method, and the magnetic properties were measured. are also listed in Table 1. For comparison, it was treated and measured in the same manner as in Example 2 except that it was not hydrogenated, and the results are shown in Table 1 (Comparative Example 2).

(Effects of the Invention) Magnets made by hydrogenating a magnet alloy ingot according to the present invention, classifying the brittle and collapsed coarse powder into a predetermined particle size distribution, molding, sintering, and heat-treating the magnet have an extremely low oxygen concentration and can be easily stored. The magnetic force is increased, and there is no decrease in density or orientation due to coarse powder, and a rare earth permanent magnet with excellent magnetic properties and constant quality is obtained, and its industrial value is extremely high.

No. l table

Claims (1)

[Claims] 1. Composition formula R_xFe_1_0_0_-_X_-_Y_
-_ZB_YM_Z (However, R is at least one or two or more elements among rare earth elements including Nd,
M is at least one or two or more elements among Al, CO, Ga, Nb, and Zr, and X = 10 in atomic percentage
~25%, Y = 1 ~ 20%, Z = 0 ~ 20%)) is exposed to a hydrogen atmosphere, hydrogenated, finely pulverized, and classified to obtain a magnet with a size of 2 μm or more and 50 μm or less. A method for producing rare earth permanent magnets, which comprises compression molding alloy powder, sintering, and heat treating it.