JPS6386832A - Manufacturing method of rare earth sintered alloy permanent magnet - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a magnetically custom-made finely arranged rare earth sintered alloy that has significantly less grain growth and residual bore, and has almost no disorder of crystal orientation or deformation. We are proud of the manufacturing method for permanent magnets (hereinafter referred to as sintered rare earth magnets).

[Conventional technology]

Sintered rare earth magnets such as Sm--Co and Nd--Fe--B have been highly evaluated for their high magnetic properties, have been significantly developed in recent years, and are now in widespread practical use.

In general, these sintered rare earth magnets are made by press-molding fine powder of rare earth alloy in a magnetic field or in no magnetic field, and press-forming it in a vacuum or in a non-oxidizing gas atmosphere, for example, for 10 min.
It is manufactured by sintering at a sintering temperature of 00 to 1250'C and held for 30 to 60 minutes.

[Problems that the invention attempts to solve]

However, in the production of the conventional sintered rare earth magnets mentioned above, the sintering atmosphere? The solid state completes as a vacuum in the 7-line Natsu Kōbadai,
If crystal grain growth is unavoidable and liquid-phase sintering is carried out in a vacuum atmosphere, in addition to grain growth, disturbances in crystal orientation may occur. Type 7 is generated, and if the sintering atmosphere is set to a non-oxidizing gas, a bore will remain in the sintered body in both solid phase and liquid phase sintering. , grain growth of grains, disordered crystal orientation n1, and residual bores, both IL, are causes of a decrease in magnetic W note.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to fully manufacture sintered rare earth magnets that are free from grain growth, disturbance of crystal orientation, and residual bores, and found that they can be maintained at the sintering temperature. If hydrogen gas is used in the atmosphere during the first half of the time, under reduced pressure, normal pressure, or pressurized state, this hydrogen gas will significantly suppress the growth of crystal grains, and will also cause disturbances in crystal orientation in the case of liquid phase sintering. It has the effect of suppressing deformation, so it can prevent grain growth and crystal orientation disturbances. A primary sintered body with almost no shape is formed, and although there is no open bore on the surface of the primary sintered body, there is a closed bore inside due to hydrogen gas. When sintering is carried out by switching from this state to a high-pressure non-oxidizing gas atmosphere in the latter half of the process, in addition to the above-mentioned effects, hydrogen gas also has the effect of easily diffusing Y into the secondary sintered body. Therefore, grain growth and disturbance of crystal orientation are suppressed in the NFC state, which is included in the crystallization atmosphere and forms residual bores under the downward hydrogen gas force; expansion W! ,
Because it becomes emitted, it causes grain growth and deafness.
7'L and deformation i.
This invention was based on the above-mentioned knowledge. It is a pressed powder body made from rare earth company fine powder.
The magnetic properties can be improved by sintering in a reduced pressure, normal pressure, or pressurized hydrogen gas atmosphere for the first half of the holding time at the sintering temperature, and in a high pressure non-oxidizing gas atmosphere for the second half. The method for producing sintered famous earthen magnets is characterized by θ].

〔Example〕

Next, the tenacity of this invention will be explained with reference to examples.

Example 1 Ordinary vacuum arc melting furnace! Used, Nd, Fe, TB
A rare earth metal with the composition was melted and cast into a 250 g button mass, and this button mass was made into a coarse powder of 128 mesosh by using a stamp mill in an Ar air flow.
A rare earth @ gold fine powder having an average particle size of 4.3 μm was prepared by pulverization for 5 hours using a vibrating ball mill in a K-membrane deaerated fluorocarbon, and then the balls were completely separated and dried under vacuum to remove the fluorocarbon. After that, this dry fine powder was oriented in a mold by applying a magnetic field of 15 KOe to 1.5 to
Press molding with a pressure of n 7 cm 10) IIIX
Dimensions of 10mx x 10m+a? The obtained green compact is molded, charged into a pressure sintering furnace, and heated at room temperature.
0 mxHg vacuum, then 10 mmHg
While flowing high-purity hydrogen gas under reduced pressure, temperature: 10
After heating to 60°C and keeping at this temperature for 30 minutes, all hydrogen gas was exhausted to create an atmosphere of Y I Oxx Hg, and then Arc was introduced and the atmosphere was set to 50 atm and heated to 2
The magnet was held at 620°C for 0 minutes, then rapidly cooled in a trench at 620°C, held at this temperature for 2 hours, and then rapidly cooled at room temperature.The method 1 of the present invention was then applied to produce the sintered rare earth magnet 1 of the present invention. this.

Also, for the purpose of comparison, the shioki atmosphere? Conventional method 13 was carried out under the same conditions as the method 1 of the present invention except that the Ar gas flow was at normal pressure.
Example 2: Using a conventional high-frequency melting furnace and daytime Ar gas, Sni
(coo, 65°Cuo, o?5 Feo,...Zr
o. H) Made from rare earth metal alloy with the composition of T and s,
2.2 A part of this ingot was cast into a coarse powder bed of 128 m/y using a stamp mill in an air stream for 250 m, and then degassed with freon. Inside, using a vibrating mill, the powder was pulverized for 4 hours to produce rare earth phosphor fine powder with an average particle size of 5.6 μm.Then, the balls were separated and vacuum dried. Freon! After removal, this dry fine powder was oriented in a t-shape by applying a magnetic field of 15 KOe, and was heated at 1.5 ton/min.
110m x 10 + depth x 1 by resin molding at 32 pressure
Formed into a green compact with dimensions of 01, and this green compact is
Charge the pressurizing/sintering furnace 1c, and first heat the IO-5*w at room temperature.
, create a Hg vacuum, then introduce high-purity hydrogen gas to raise the temperature, raise the temperature to a sintering temperature of 1200'C, and hold it at this sintering temperature for the first half of 30 minutes. Atmosphere 3
Sintering was carried out under the conditions of a hydrogen gas atmosphere at atmospheric pressure and an Ar atmosphere at 3 atm for the latter half of 20 minutes.
Cool to 180°C, hold at this temperature for 1 hour for solution treatment, then age at 800°C for 7 hours, and finally cool at 1°5°C/min. Method 2 of the present invention was carried out by cooling at a speed of 4 UO°C and then rapid cooling to produce sintered rare earth magnet 2 of the present invention.

For the purpose of comparison, the conventional method 27 was also prepared under the same conditions as the method 2 of the present invention, except that the sintering atmosphere was a normal pressure Ar gas flow.
A conventional rare earth magnet 2 was manufactured.

Example 3 The composition of the rare earth alloy was set to 'i S m C84,1s, the grinding time of the coarse powder was set to 8 hours, the average particle size of the obtained rare earth alloy fine powder was set to 45 μm, and the compacting of the compact was carried out. Pressure 'e 2. In addition, the sintering temperature was 120'C, the atmosphere was 30 minutes for the first half of the holding time at this sintering temperature, and the atmosphere was a high-strength hydrogen gas flow at normal pressure. for 20 minutes in an Ar gas atmosphere of 150 atm, and then cooled to F, (,800°C) after sintering.
The method 3 of the present invention was carried out under the same conditions as in Example 2 except that the temperature was slowly cooled at a cooling rate of 1°C/min until the temperature reached 1° C. For the purpose of comparison, a conventional sintered rare earth magnet 3 was manufactured under the same conditions as the method 3 of the present invention, except that the sintering atmosphere was changed to a vacuum of lo+amHg.

Next, the uninvented sintered rare earth magnets 1 to 3 obtained as a result
And for conventional sintered rare earth magnets 1 to 3, average crystal grain size, theoretical density ratio, and magnet customization? It was measured. These measurement results are shown in the first garment.

〔Effect of the invention〕

From the results shown in Table 1, it can be seen that the sintered rare earth magnets 1 to 3 of the present invention manufactured by the methods 1 to 3 of the present invention had almost no growth of crystal grains, had relatively fine grains, and Since there are almost no closed bores, they exhibit a high theoretical density ratio, and as a result, exhibit constant magnetic characteristics, whereas conventional sintered rare earth magnets 1 to 3 manufactured by conventional methods 1 to 3 In addition to exhibiting a relatively high crystal grain size due to grain growth, magnet No. 3 is relatively inferior to the sintered rare earth magnets No. 1 to No. 3 of the present invention due to residual closed bores. It is clear to show.

As mentioned above, according to the method of the present invention, it is possible to produce a well-defined sintered rare earth foundation stone for a magnet, which has almost no grain growth, no residual bore, and no disturbance or deformation of crystal orientation.

Claims (1)

[Claims] A green compact press-formed from rare earth alloy fine powder is held at the sintering temperature in a reduced pressure, normal pressure, or pressurized hydrogen gas atmosphere for the first half of the time, and a high-pressure non-oxidizing gas atmosphere for the second half. A method for producing permanent magnets made of rare earth sintered alloys with excellent magnetic properties characterized by sintering under certain conditions.