JPH1041174A - Production of r-fe-b based magnet having low content of o2 - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an R-Fe-B based magnet containing O2 by 4000ppm or less and having excellent magnetic characteristics stably by protecting the material powder against oxidation and handling the material powder stably in the atmosphere. SOLUTION: Fine powder for R-Fe-B based magnet is immersed into liquid N2 or liquid Ar so that the surface of the fine powder is coated with the liquid N2 or liquid Ar. The fine powder is then collected and contained immediately in a container filled with N2 gas or Ar gas containing specified concentration of o. where the fine powder is kept at normal temperature. The-liquid N2 or liquid Ar is evaporated from the surface of the fine powder and N2 gas or Ar gas is adsorbed to the surface thus producing stabilized fine powder. The fine powder is molded in a magnetic field or not in a magnetic field and subjected to sintering and aging thus producing a stabilized R-Fe-B based magnet containing O2 by 4000ppm or less and excellent in magnetic characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing O ₂ containing less R-Fe-B magnet, in particular containing O ₂
There for the production of the following R-Fe-B magnet 4000 ppm, by immersing the raw material powder for R-Fe-B magnets after milling immediately in liquid nitrogen (N ₂₎ or liquid argon (Ar), wherein in a vessel of N ₂ gas or Ar gas filling of a particular O ₂ concentration after recovery by returning the fine powder to ambient temperature, vaporizing liquid nitrogen or liquid argon of the fine powder surface, N ₂ gas into a fine powder surface or adsorbing the Ar gas to obtain a fine powder stabilized, molding the powder, sintering, and aging, low O ₂ content R-Fe-B system to obtain the magnets of excellent magnetic properties stably The present invention relates to a method for manufacturing a magnet.

[0002]

2. Description of the Related Art In general, raw material powders for R-Fe-B magnets are obtained by ingot crushing, in which crushing is repeated after casting, Ca reduction diffusion, in which powder is reduced by Ca reduction, or quenching of a molten alloy with a quenching roll. An R-Fe-B-based alloy was obtained by a strip casting method or the like for obtaining a ribbon having fine crystals, and the raw material powder was obtained by pulverizing the R-Fe-B-based alloy.

[0003] The R-Fe-B obtained by the various methods described above
The raw material powder for system magnets is chemically very active and rapidly oxidizes in the air, leading to deterioration and variation in magnetic properties, and not only generates heat due to rapid oxidation,
There was also a problem in terms of safety after firing.

Therefore, a method of stabilizing the obtained raw material powder for R-Fe-B magnet by storing it in an inert gas such as N ₂ or Ar for a long time has been adopted. In addition, since the powder has a hygroscopic property, it reacts with moisture in the air to increase the amount of O ₂ , thereby deteriorating the magnetic properties of the obtained R—Fe—B magnet.

[0005]

Recently, in order to prevent oxidation of the raw material powder for R-Fe-B based magnets and to stably handle the raw material powder in the atmosphere, the raw material powder is made of mineral oil having a specific fractionation point. A method of producing a low O ₂ -containing R-Fe-B based magnet by immersing in synthetic oil to obtain a powder having a surface coated with mineral oil or synthetic oil, and molding, sintering and aging the powder. Are proposed (JP-A-7-86069, JP-A-7-90469).
No.).

In the above-mentioned production method, magnetizing is performed using a powder coated with a mineral oil or a synthetic oil, so that C, O _{2 and the} like contained in the mineral oil or the synthetic oil do not remain in the magnet. In addition, the mixed powder of the raw material powder and the mineral oil or the synthetic oil is separated by a centrifugal separator or the like, and the mineral oil or the synthetic oil adhering when the compact is sintered is removed to obtain the residual C content and O _In order to reduce the amount, it is necessary to raise the temperature and cool the furnace under specific heat treatment conditions, which has led to a problem that the work becomes complicated and the production cost increases.

According to the present invention, R-Fe-B based magnet powder can be prevented from being oxidized, can be stably handled in the atmosphere, and has an O ₂ content of 4000 ppm or less. An object of the present invention is to provide a method for producing a low O ₂ -containing R—Fe—B-based magnet capable of stably producing a B-based magnet.

[0008]

Means for Solving the Problems The present inventors have proposed R-Fe-
To prevent oxidation of the raw material powder for the B-based magnet, and to obtain a raw material powder that is stable in the air, as a result of various studies, a fine powder for the R-Fe-B-based magnet obtained by any of the known manufacturing methods was used. is immersed in the liquid N ₂ or liquid Ar, the fine powder surface liquid N ₂ or liquid Ar coating, after recovering immediately particular O ₂ concentration in the N ₂ gas or Ar gas filled the container to the The liquid N ₂ or liquid Ar coated on the surface of the fine powder
Is vaporized, and a stable fine powder is obtained by adsorbing N ₂ gas or Ar gas on the surface.After molding the fine powder in a magnetic field or without a magnetic field, sintering and aging are performed.
O ₂ content was found that following magnetic properties superior and stable R-Fe-B magnet 4000ppm obtained, and have completed the present invention.

According to the present invention, the raw material powder for an R—Fe—B magnet is finely pulverized and immediately immersed in liquid N ₂ or liquid Ar, and after recovery, for example, N ₂ gas having an O ₂ concentration of 1% or less. After bringing the fine powder to room temperature in a container filled with Ar gas,
This is a method for producing a low O ₂ -containing R—Fe—B-based magnet, which is subjected to molding, sintering, and aging.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
-Fe-B-based raw material powder is obtained by a known ingot grinding method, C
a A fine powder obtained by a known production method such as a reduction diffusion method or a strip casting method, or a coarse pulverized powder obtained by a strip casting method is jet-milled under a specific condition, or a mechanical pulverization method such as a ball mill. Any of the production methods, such as fine powder obtained by finely pulverizing the powder, can be used. Further, the average particle size of the powder immersed in the liquid N ₂ or liquid Ar is preferably 0.1 to 10 μm. If the average particle size is less than 0.1 μm, the press moldability is deteriorated, causing cracks and the like. It is not preferable because the density of the compact after press molding is reduced, and is more preferably a fine powder having an average particle size of 2 to 4 μm.

Particularly, as a method for producing a raw material powder, a slab or a flake obtained by a strip casting method is roughly pulverized into a coarsely pulverized powder having an average particle size of 10 to 500 μm by an H ₂ occlusion collapse method, and then O ₂ 2,000 pm or less. The method of carrying out jet mill pulverization by a supersonic inert gas stream described above is preferred. The reason for limiting the amount of O ₂ in the supersonic inert gas stream at the time of jet mill pulverization to 2000 ppm or less is that O ₂
When the amount exceeds 2,000 ppm, the fine powder reacts with O ₂ in the inert gas to oxidize at the time of fine pulverization, and O _{2 of the} obtained fine powder is
It is not preferable because the content exceeds 4000 ppm.

[0012] More specifically the manufacturing method according to the invention, the raw material powder for the above R-Fe-B magnet was immersed for 60 seconds to 100 hours in liquid N ₂ or in a liquid Ar, liquid N ₂ or liquid Ar is vaporized into N ₂ gas or Ar
Either disperse as a gas, or collect the fine powder and store it in a container filled with N ₂ gas or Ar gas having an O ₂ concentration of 1% or less. The liquid N ₂ or liquid Ar of the coating is vaporized,
The surface of the fine powder is stabilized by adsorbing N ₂ gas or Ar gas, and after shaping the fine powder in a magnetic field, sintering and aging, excellent magnetic properties with an O ₂ content of 4000 ppm or less, An R—Fe—B-based magnet with little variation can be obtained.

In the present invention, if the time for immersing the R-Fe-B-based magnet raw material powder in the liquid N ₂ or liquid Ar is less than 60 seconds, the fine powder is not sufficiently cooled and the liquid N 2 is not sufficiently cooled.
_The N ₂ gas or Ar gas cannot be adsorbed and stabilized on the surface of the fine powder without being immersed in ₂ or liquid Ar. On the other hand, if the time exceeds 100 hours, the amount of impurities O ₂ in the liquid N ₂ or liquid Ar increases depending on the storage conditions, and as a result, the amount of O ₂ in the fine powder increases or storage becomes difficult. Therefore, it is not preferable.

In the present invention, the liquid N ₂ or the liquid A
The raw material fine powder coated with r on the surface after recovery, O ₂ concentration 1
% Of N ₂ gas or Ar gas or less, and the temperature is raised to room temperature because the fine powder is mixed with O ₂ in the low temperature condition of liquid N ₂ or liquid Ar on the surface of the fine powder. This is because the surface stabilization treatment can be performed while suppressing the oxidation reaction. Further, the liquid N ₂ or liquid Ar to be immersed and coated is vaporized, and N ₂ gas or Ar
By adsorbing the gas, the contact between the fine powder and the atmosphere is cut off, which is extremely effective in preventing oxidation and excellent in stability.

In the present invention, the composition of the raw material powder for the R—Fe—B magnet is preferably as follows. Rare earth element R
Accounts for 10 to 30 atomic% of the composition, but Nd,
At least one of Pr, Dy, Ho, and Tb; or La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, Yb, Lu, and Y are preferable. Also, usually one of R is sufficient,
In practice, a mixture of two or more kinds (mish metal, dymium, etc.) can be used for reasons such as convenience in obtaining. Note that R may not be a pure rare earth element, and may contain impurities which are unavoidable in production within the industrially available range.

R is an essential element in the R—Fe—B permanent magnet, and if it is less than 10 atomic%, the crystal structure becomes a cubic structure having the same structure as α-iron, so that it has high magnetic properties, especially high coercive force. When the content exceeds 30 atomic%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is 1
A range of 0 to 30 atomic% is desirable.

B is an essential element in the above-mentioned permanent magnets. If it is less than 2 at%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained.
Since a rich non-magnetic phase increases and the residual magnetic flux density (Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is desirably in the range of 2 to 28 atomic%.

Fe is an essential element in the above-mentioned permanent magnets. When the content is less than 65 at%, the residual magnetic flux density (Br) decreases, and when it exceeds 80 at%, a high coercive force cannot be obtained. % To 80 atomic%.
Further, substituting part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet. However, when the amount of Co exceeds 20% of Fe, the conversely occurs. It is not preferable because the magnetic properties deteriorate. When the substitution amount of Co is 5 atomic% to 15 atomic% in the total amount of Fe and Co, (Br) increases as compared with the case where the substitution is not performed, so that it is preferable to obtain a high magnetic flux density.

Further, in addition to R, B, and Fe, the presence of unavoidable impurities in industrial production can be tolerated. For example, a part of B may be 4.0 wt% or less of C, 2.0 wt% or less of P, .0
By replacing at least one of S by wt% or less and Cu by 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the productivity and reduce the cost of the permanent magnet.

Further, Al, Ti, V, Cr, Mn, B
i, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr,
At least one of Ni, Si, Zn, and Hf is R
-It can be added to the Fe-B-based permanent magnet because it has the effect of improving the coercive force and the squareness of the demagnetization curve, improving the productivity, and reducing the price. Note that the upper limit of the addition amount is desirably in a range that satisfies the above condition because (Br) must be at least 9 kG or more in order to make the (BH) max of the magnet material 20 MGOe or more.

[0021]

【Example】

Example 1 An R-Fe-B based alloy ingot having a composition of Nd13.28-B5.95-Fe80.67 wt% was heated at 1100 ° C. in N ₂ gas.
After 10 hours solution treatment, after coarse grinding to an average particle size of 500μm with H ₂ occlusion decay process, the coarsely pulverized powder O ₂ 450
It was pulverized by a jet mill using a supersonic N ₂ gas stream containing ppm to obtain a finely pulverized powder having an average particle size of 3.5 μm.

Thereafter, the finely pulverized powder is immersed in liquid N ₂ for 1 hour, and the fine powder is held in a container filled with N ₂ gas having an O ₂ concentration of 0.1% for 3 hours. After that, the maximum temperature of the powder when the fine powder is left in the air (25 ° C. × 75% RH) for 600 minutes is shown in FIG.

The fine powder is magnetically molded at a molding pressure of 1 ton / cm ² in a magnetic field strength of 15 kOe, sintered at 1050 ° C. for 5 hours, and then subjected to an aging treatment at 580 ° C. for 2 hours to obtain RF.
An eB magnet was obtained. Table 1 shows the O ₂ content and magnetic characteristics of the obtained magnet, and FIG. 2 shows a demagnetization characteristic curve.

Comparative Example 1 A coarsely pulverized powder having the same composition as in Example 1 was jet-milled in a supersonic N ₂ stream containing 450 ppm of O ₂ to obtain a fine powder having an average particle size of 3.5 μm. When this fine powder was stored in the atmosphere, it ignited in 30 seconds as shown in FIG. 1 and could not be made into a permanent magnet.

[0025] Comparative Example 2 Example 1 and coarse pulverized powder having the same composition O ₂ 10000 ppm
The resulting powder was pulverized by a jet mill using a supersonic N ₂ gas stream to obtain a fine powder having an average particle size of 3.5 μm, and then formed into a permanent magnet under the same conditions as in Example 1. Table 1 shows the O ₂ content and magnetic characteristics of the obtained magnet, and FIG. 2 shows a demagnetization characteristic curve.

[0026]

[Table 1]

[0027]

According to the present invention, R-Fe-B having a low O ₂ content is obtained.
The method for producing a magnet based on R-Fe-B magnet raw material powder is immediately pulverized, then immediately immersed in liquid nitrogen or liquid argon, and after collection, filled with a specific O ₂ concentration of N ₂ gas or Ar gas. Returning the fine powder to normal temperature in a container, vaporizing liquid nitrogen or liquid argon on the surface of the fine powder, and obtaining a stabilized fine powder by adsorbing N ₂ gas or Ar gas on the surface of the fine powder, By molding, sintering and aging the fine powder, a magnet having excellent magnetic properties with a content of O ₂ of 4000 ppm or less can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a standing time and a maximum attained temperature.

FIG. 2 is a graph showing a demagnetization characteristic curve, in which an alternate long and short dash line indicates Example 1 and a solid line indicates Comparative Example 2.

Claims (2)

[Claims] 1. A raw material powder for an R—Fe—B magnet is finely pulverized and immediately immersed in liquid nitrogen or liquid argon. After recovery, the powder is brought to room temperature, and then molded, sintered, and aged. A method for producing a low O ₂ -containing R—Fe—B-based magnet, comprising: 2. The raw material powder for an R—Fe—B magnet is finely pulverized, immediately immersed in liquid nitrogen or liquid argon, recovered, and placed in a container filled with N ₂ gas or Ar gas having an O ₂ concentration of 1% or less. A method for producing a low O ₂ -containing R-Fe-B magnet, which comprises subjecting the fine powder to room temperature, followed by molding, sintering and aging.