JP2003049234A - Method for producing sintered compact for rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a rare earth alloy sintered compact by which a rare earth alloy sintered compact can be reutilized as the raw material more efficiently than the conventional one. SOLUTION: The production method includes a stage (a) wherein a rare earth alloy sintered compact is crushed by using a hydrocrushing method to produce first coase powder, a stage (b) wherein the first coase powder is pulverized to produce first fine powder, a stage (c) wherein an alloy lump of a rare earth alloy raw material is pulverized to produce second fine powder, a stage (d) wherein a powdery mixture of the first fine powder and the second fine powder is produced, and a stage (e) wherein the powdery mixture is sintered. Both the first fine powder and the second fine powder have the main phase having a composition expressed by (LR1-x HRx )2 T14 A (0<=x<1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered body for rare earth magnets, and more particularly to a method for producing a sintered body for R-Fe-B magnets.

[0002]

2. Description of the Related Art Sintered magnets (permanent magnets) of rare earth alloys are
Generally, it is produced by press-molding a powder of a rare earth alloy, sintering the obtained powder compact, and subjecting it to an aging treatment. Magnetization for making the sintered body into a magnet is performed at any stage after the aging treatment. The “rare earth alloy sintered body” in the present specification includes both a sintered body before magnetized and a magnetized sintered body (that is, a sintered magnet).

At present, two types of magnets, samarium / cobalt magnets and neodymium / iron / boron magnets, are widely used in various fields. Among them, neodymium-iron-boron-based magnets (hereinafter referred to as "R-Fe-B-based magnets". R is a rare earth element including Y, Fe is iron, and B is boron) are various magnets. Shows the highest maximum magnetic energy product of
Since the price is relatively low, it is actively used in various electronic devices.

R-Fe-B system sintered magnets are mainly composed of R ₂ Fe.
_It is composed of a main phase composed of a ₁₄ B tetragonal compound, an R-rich phase composed of Nd and the like, and a B-rich phase. In addition,
A part of Fe may be replaced with a transition metal such as Co or Ni, and a part of B may be replaced with C. R-Fe-B based sintered magnets to which the present invention is preferably applied include, for example, US Pat. No. 4,770,723 and US Pat. No. 4,79.
2,368.

[0005] In order to produce an R-Fe-B type alloy which becomes such a magnet, an ingot casting method (die casting method) has been conventionally used. According to a general ingot casting method, a rare earth metal, electrolytic iron, and ferroboron alloy as a starting material are subjected to high frequency melting, and the obtained molten metal is cooled in a mold relatively slowly to produce an alloy ingot.

In recent years, molten alloy has been used for single roll, twin roll,
By contacting the inner surface of a rotating disk or a rotating cylindrical mold, it cools relatively quickly,
A rapid cooling method represented by a strip casting method and a centrifugal casting method for producing a solidified alloy thinner than an ingot (hereinafter referred to as “alloy flake”) has been attracting attention. The thickness of the alloy piece produced by such a quenching method is generally in the range of about 0.03 mm or more and about 10 mm or less.
According to the quenching method, the molten alloy starts solidifying from the surface in contact with the cooling roll (roll contact surface), and crystals grow columnar in the thickness direction from the roll contact surface. As a result, the quenched alloy produced by the strip casting method or the like has an R ₂ Fe ₁₄ B crystal size of about 0.1 μm or more and about 100 μm or less in the minor axis direction and about 5 μm or more and about 500 μm or less in the major axis direction. It has a structure containing a phase and an R-rich phase which exists in the grain boundary of the R ₂ Fe ₁₄ B crystal phase in a dispersed manner. The R-rich phase is a non-magnetic phase in which the concentration of the rare earth element R is relatively high.

Quenched alloys have a relatively short time (cooling rate: 10 ² ° C / sec or more, 10 ⁴ ° C / second) as compared with alloys (ingot alloys) produced by the conventional ingot casting method.
Since it is cooled for less than a second), the structure is refined and the crystal grain size is small. Further, since the area of the grain boundary is wide and the R-rich phase is widely spread in the grain boundary, there is an advantage that the dispersibility of the R-rich phase is also excellent.
Due to these characteristics, by using a quenched alloy,
It is possible to manufacture a magnet having excellent magnetic properties.

The Ca reduction method (or reduction diffusion method)
The method called is also known. This method includes the following steps. First, a mixed powder containing at least one kind of rare earth oxide, iron powder and pure boron powder, and at least one kind of ferroboron powder and boron oxide in a predetermined ratio, or an alloy powder of the above constituent elements. Alternatively, metal calcium (Ca) and calcium chloride (CaCl) are mixed with a mixed powder containing a mixed oxide in a predetermined ratio,
A reduction diffusion process is performed in an inert gas atmosphere. The obtained reaction product is slurried and treated with water to obtain an R-Fe-B based alloy solid.

In the present specification, a solid alloy ingot is referred to as an "alloy ingot", and includes an alloy ingot obtained by a conventional ingot casting method and a molten metal such as an alloy flake obtained by a quenching method such as a strip casting method. Not only solidified alloys obtained by cooling but also solid alloys in various forms such as solid alloys obtained by the Ca reduction method are included.

The alloy powder to be subjected to press molding is obtained by crushing these alloy lumps by, for example, a hydro-milling method and / or various mechanical crushing methods (for example, a feather mill, a power mill or a disc mill is used). It is obtained by finely pulverizing the obtained coarse powder (for example, average particle size 10 μm to 500 μm) by a dry pulverization method using a jet mill. From the viewpoint of magnetic properties, the average particle size of the alloy powder used for press molding is preferably in the range of 1.5 μm to 7 μm. The "average particle size" of the powder
Is the mass median diameter (ma
ss median diameter (MMD). Fine pulverization can also be performed using a ball mill or an attritor.

The rare earth alloy powder has a problem that it is easily oxidized. In order to avoid this problem, for example, a method of forming a thin oxide film on the surface of rare earth alloy powder is known. Also known is a method of coating the surface of the rare earth alloy powder with a lubricant. In the present specification, the rare earth alloy powder, the rare earth alloy powder having an oxide film formed on the surface, and the rare earth alloy powder having the surface coated with a lubricant are also referred to as “rare earth alloy powder” for simplicity. However,
The “composition of rare earth alloy powder” does not include the above oxide film or lubricant.

The raw material price of the above rare earth sintered magnet is R-
Even Fe—B based magnets are relatively expensive, so from the viewpoint of cost reduction and effective use of resources, it is considered to reuse defective defective rare earth alloy sintered bodies as raw materials without remelting. ing.

For example, in Japanese Patent No. 2746818, an oxide component is added to a powder obtained by crushing scrap of Nd-Fe-B system sintered magnet alloy (hereinafter sometimes referred to as "scrap powder"). There is disclosed a method of improving the sinterability of scrap powder and mixing it with a rare earth alloy powder (“alloy B” in the above publication) that supplements the above, and reusing it.

Further, in Japanese Patent Laid-Open No. 11-329811, Nd ₂ Fe is obtained by subjecting scrap powder of an R—Fe—B magnet to acid cleaning and Ca reduction treatment.
Disclosed is a method of utilizing scrap powder by producing an alloy powder having a ₁₄ B phase as a main phase and mixing the alloy powder for composition adjustment for improving the sinterability of the powder.

[0015]

However, in any of the above-mentioned methods, alloy powder (alloy B powder or alloy powder for composition adjustment) having a composition essentially different from that of the alloy powder for producing the target rare earth alloy sintered body is used. ) Must be prepared,
There is a problem that the entire manufacturing process is complicated. The alloy B powder or the alloy powder for composition adjustment described above is difficult to produce a sintered body for a rare earth magnet using only these, and even if it is made into a magnet, its properties are significantly low.

The present invention has been made in view of the above points, and a main object of the present invention is to reuse a rare earth alloy sintered body as a raw material more efficiently than ever before.
It is to provide a method for manufacturing a rare earth alloy sintered body.

[0017]

The method for producing a sintered body for a rare earth magnet according to the present invention comprises: (a) coarsely pulverizing a rare earth alloy sintered body using a hydro-pulverization method to obtain a first coarse powder. A step of producing, (b) a step of producing a first fine powder by pulverizing the first coarse powder, and a step of producing a second fine powder by pulverizing (c) an alloy lump of a rare earth alloy raw material. And (d) the first fine powder and the second
And a step of sintering a mixed powder containing a fine powder, wherein the first fine powder and the second fine powder are both (LR
_1-x HR _x ) ₂ T ₁₄ A (T is Fe or a mixture of Fe and at least one transition metal element other than Fe, A is boron or a mixture of boron and carbon, and LR is a light rare earth element. At least one kind, HR has at least one kind of heavy rare earth element, and has a main phase having a composition represented by 0 ≦ x <1), whereby the above object is achieved.

The first fine powder and the second fine powder are
25% to 40% by mass of the rare earth element R (R
= LR _1-x HR _x ) and 0.6 mass% to 1.6 mass% of A
It is preferable to include and. The rest other than R and A is T
In addition, it contains trace elements and unavoidable impurities. The trace addition element is preferably at least one of Al, Cu, Ga, Cr, Mo, V, Nb and Mn. It is preferable that the total amount of trace additives be 1% by mass or less. The content of the rare earth element R in the finally obtained sintered body for a rare earth magnet is preferably 34% by mass or less, and more preferably 33% by mass or less.

The rare earth alloy sintered body and the alloy ingot of the rare earth alloy raw material are both (LR _1-x HR _x ) ₂ T ₁₄
It is preferable to contain the compound represented by A in an amount of 80% by volume or more.

The mass fraction of the first fine powder in the mixed powder is 0.1% to 10% of the mass of the second fine powder.
It is preferably within the range of not more than%.

X in the composition formula of the main phase of the first fine powder
And the value of x in the composition formula of the main phase of the second fine powder are different from each other, the first powder in the mixed powder
The mass fraction of the fine powder is preferably less than 5% of the mass of the second fine powder. From the viewpoint of magnetic properties, it is more preferably less than 3%.

In the step (a), the rare earth alloy sintered body is preferably subjected to coarse pulverization by a hydrogenation pulverization method as a plurality of lumps each weighing 50 g or less.

The step (c) includes a step of coarsely crushing the alloy ingot to produce a second coarse powder, and a step of finely pulverizing the second coarse powder to produce the second fine powder. Including, mixing the first coarse powder and the second coarse powder, and then pulverizing the first coarse powder and the second coarse powder to obtain the first fine powder and the second fine powder. Preferably, a mixed powder of is prepared.

Alternatively, in the step (c), a step of producing a second coarse powder by coarsely pulverizing the alloy ingot and a step of producing the second fine powder by finely pulverizing the second coarse powder. And a step of producing a mixed coarse powder of the first coarse powder and the second coarse powder by hydrogenating and pulverizing in a state of mixing the alloy ingot and the rare earth alloy sintered body. A process of producing a mixed powder of the first fine powder and the second fine powder by finely pulverizing the coarse powder may be adopted.

The alloy ingot in the step (c) is preferably prepared by a quenching method from the molten metal of the rare earth alloy raw material.

As the rare earth alloy sintered body, a defective sintered body for rare earth magnet can be used.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for producing a rare earth alloy sintered body according to the present invention will be described below.

The method for producing a sintered body for a rare earth magnet according to the present invention comprises: (a) a step of producing a first coarse powder by roughly pulverizing a rare earth alloy sintered body using a hydrogenation pulverization method; b) pulverizing the first coarse powder to give the first
A step of producing a fine powder, (c) a step of producing a second fine powder by crushing an alloy ingot obtained by cooling the molten metal of the rare earth alloy raw material, (d) a first fine powder and a first fine powder Sintering a mixed powder containing two fine powders. Both the first fine powder and the second fine powder are (L
R _1-x HR _x ) ₂ T ₁₄ A having a main phase of a composition represented by A.

In the present specification, the composition of the main phase of the R-Fe-B system alloy sintered body is (LR _1-x HR _x ) ₂ as described above.
The composition formula of T ₁₄ A will be used. T is Fe or a mixture of Fe and at least one transition metal element other than Fe, A is boron or a mixture of boron and carbon,
LR is at least one kind of light rare earth element, and HR is at least one kind of heavy rare earth element. Further, LR and HR are collectively denoted by R.

The light rare earth element LR is La, Ce, Pr,
It is Nd, Pm, Sm, Eu, Gd, etc., and preferably contains at least one of Nd and Pr. Heavy rare earth elements HR are Y, Tb, Dy, Ho, Er, Tm, Y
b, Lu, etc., and preferably contains at least one selected from Dy, Ho and Tb. It should be noted that x indicating the substitution amount (atomic ratio) of the heavy rare earth element HR with respect to the light rare earth element LR is within the range of 0 ≦ x <1, and the heavy rare earth element HR may not be included.

The transition metal elements are Ti, V, Cr and M.
It is preferably n, Fe, Co, Ni, or the like, and T is preferably Fe or a part of Fe substituted with at least one of Ni and Co.

In order to obtain a sintered magnet having excellent magnetic properties, both the first fine powder and the second fine powder contain 25% by mass to 40% by mass of a rare earth element R (R = LR _1-x HR). _x )
And 0.6% by mass to 1.6% by mass of A are preferable. The balance other than R and A contains T, trace addition elements, and unavoidable impurities. Trace addition elements are Al and C
It is preferably at least one of u, Ga, Cr, Mo, V, Nb and Mn. It is preferable that the total amount of trace additives be 1% by mass or less. Furthermore, the alloy ingot of the rare earth alloy sintered body and the rare earth alloy materials are both preferably comprises _{(LR 1-x HR x)} 2 T 14 a compound represented by A or 80 vol%. Since the alloy ingot obtained by cooling the melt of the rare earth alloy raw material has not undergone the sintering step, its oxygen content is usually 1000 ppm or less on a mass basis.

In the method for producing a rare earth alloy sintered body according to the present invention, the second fine powder used for producing the rare earth magnet sintered body is mixed with the first fine powder produced from the rare earth alloy sintered body. The powder does not have to have a special composition,
This alone can be used to manufacture the intended sintered body for a rare earth magnet.

For example, the second fine powder may be a fine powder for producing a rare earth alloy sintered body which is a raw material of the first fine powder, or may be different. The composition of the rare earth alloy sintered body is adjusted according to various uses. In general, rare earth alloy sintered bodies of various grades are manufactured in a rare earth alloy sintered body manufacturing plant. For example, by changing the value of x in the above composition formula, it is possible to manufacture a rare earth alloy sintered body having different residual magnetic flux density Br or coercive force iHc. In such a manufacturing plant, alloy lumps for respective grades having different values of x in the above composition formula are prepared, and a rare earth alloy sintered body of a target grade is manufactured. Therefore, alloy lumps of various grades and sintered bodies (good and defective products) are present in the manufacturing plant. As materials for the first fine powder and the second fine powder, materials for the same grade may be used, or materials of different grades may be used. Of course, the composition and blending amount of the first fine powder and the second fine powder are appropriately adjusted in order to keep the magnetic characteristics of the target rare earth sintered magnet within the desired range.

However, the composition of the sintered body differs from the composition of the raw material fine powder because the constituent elements (particularly rare earth elements) are oxidized during the sintering process or the like. The first fine powder produced by crushing the sintered body tends to have low liquid-phase sinterability because the rare earth element is consumed by oxidation. In order to compensate for the low sinterability of the raw material produced from the sintered body, the conventional recycling method described above uses alloy B (Patent No. 2).
No. 746818) and alloy powder for composition adjustment (JP-A-1
No. 1-329811) are mixed.

On the other hand, in the present invention, when the sinterability of the recycled raw material is low, it is dealt with by suppressing the blending amount of the first fine powder. Specifically, the first in the mixed powder
The mass fraction of the fine powder is preferably set within the range of 0.1% to 10% of the mass of the second fine powder. 1st fine powder (regenerated raw material fine powder) 2nd fine powder (new raw material fine powder)
If the mass fraction relative to is set to 10% or less, sufficient sinterability (for example, sufficient sintered body density can be obtained), and a sintered magnet having sufficient magnetic characteristics can be manufactured. can do. When the mass fraction of the first fine powder with respect to the second fine powder exceeds 10%, the residual magnetic flux density decreases due to the decrease in the density of the sintered body and the increase in the oxygen content in the sintered body due to the decrease in the sinterability. Br or coercive force iHc may decrease. On the other hand, when the compounding ratio of the first fine powder is low, the reuse efficiency (mainly the cost reduction effect) is low, so the mass fraction of the first fine powder to the second fine powder is 0.1.
% Or more is preferable.

When the value of x in the composition formula of the main phase of the first fine powder and the value of x in the composition formula of the main phase of the second fine powder are different from each other, that is, sintering of different grades in the above example When the first fine powder is produced using the body, the mass fraction of the first fine powder in the mixed powder is 5% of the mass of the second fine powder.
Is preferably less than 3% from the viewpoint of magnetic properties
It is more preferable that it is less than. A plurality of powders having different compositions may be used as the first fine powder,
As the second fine powder, a plurality of powders having different compositions may be used. In addition, it is preferable to analyze the composition of each of them before mixing them (coarse powder stage or fine powder stage) and determine the blending amount based on the result. The content of the rare earth element R in the finally obtained sintered body for rare earth magnet is preferably 34% by mass or less, and more preferably 33% by mass or less.

Next, in the method for producing a rare earth alloy sintered body according to the present invention, a method for producing the first fine powder from the rare earth alloy sintered body will be specifically described.

To prepare the first fine powder from the rare earth alloy sintered body, first, the coarse powder is prepared. Usually, also when producing fine powder from an alloy lump, after producing coarse powder once, it is finely pulverized to produce fine powder. This is because the rare earth alloy powder has low press formability, and therefore, fine powder having a desired particle size distribution can be efficiently produced. As the coarse pulverization method, a hydrogenation pulverization method or a mechanical pulverization method is adopted. In the manufacturing method according to the present invention, the sintered body is roughly crushed by using the hydrogenation crushing method. Since the rare earth element is hydrogenated by using the hydro-grinding method, the rare earth element is suppressed from being oxidized in the subsequent steps, as compared with the case of other mechanical grinding methods. Therefore, it is possible to suppress an increase in the oxygen content rate due to the reuse of the rare earth alloy sintered body as a raw material. Further, since the hydrogenated rare earth element is dehydrogenated in the sintering process to be metallized and become a liquid phase, the sinterability is also improved. The use of the hydro-pulverization method has an advantage that productivity in coarse pulverization and fine pulverization is improved several times as compared with the mechanical pulverization method. The hydro-grinding is preferably carried out, for example, by exposing the rare earth alloy sintered body to a hydrogen gas atmosphere of 1 MPa or less for about 0.5 hours to about 10 hours.

The hydro-pulverization method is a method in which when a rare earth alloy raw material (typically an alloy ingot) is exposed to a hydrogen gas atmosphere, a hydride of a rare earth element is produced, and the volume expansion that occurs in the hydrogenation process causes the alloy ingot to lump. Minute cracks occur inside,
It is a crushing method that utilizes the phenomenon. Therefore, it was considered to be difficult to industrially use for crushing a sintered body in which a part of the rare earth element has been oxidized. However, as a result of the study by the present inventor, it was found that the sintered body can be sufficiently used for coarse pulverization. Further, in order to efficiently pulverize the sintered body, it is preferable that the sintered body to be hydrogenated and pulverized (specific gravity: about 7.5 g) is a mass of about 50 g or less. If the individual mass of the sintered body is more than 50 g (for example, 25 mm × 24 mm × 11 mm or more), the entire sintered body cannot be coarsely crushed, and an uncrushed portion is formed at the center of the sintered body. May remain. In order to completely roughly pulverize the sintered body, it is preferable to subject the sintered body to hydrogen pulverization in the form of lumps each having a mass of about 25 g or less. When the weight of the defective sintered product exceeds about 50 g, it is preferable to mechanically grind (for example, using a jaw crusher).

Coarse powder obtained by hydro-milling (first
The coarse powder) is further mechanically pulverized (for example, using a disc mill) if necessary, and then finely pulverized by a dry pulverization method using a jet mill. The average particle size of the resulting fine powder (first fine powder) is preferably in the range of 1.5 μm to 7 μm. When the dry pulverization method using a jet mill is used, it is desirable to partially remove fine powder of 1 μm or less containing a large amount of oxygen.

The step of finely pulverizing the coarse powder using a jet mill can be carried out in the same step as the fine pulverizing step for producing the second fine powder (new raw material fine powder). As described above, the second fine powder is obtained by coarsely crushing an alloy ingot having a predetermined composition using a hydro-pulverization method or the like, and further obtaining the obtained coarse powder (second coarse powder) by mechanical pulverization. It is prepared by pulverizing (for example, using a disc mill) and then finely pulverizing by a dry pulverizing method using a jet mill. Also, the second
The average particle size of the fine powder is also preferably in the range of 1.5 μm to 7 μm. Therefore, after dry mixing (eg, using a rocking mixer) the first coarse powder and the second coarse powder,
By finely pulverizing the obtained mixed coarse powder with a jet mill, a mixture of the first fine powder and the second fine powder can be obtained. If necessary, a lubricant may be added to cover the surfaces of the first and second fine powders with the lubricant in the dry mixing step and the fine pulverizing step.

Of course, the hydro-grinding step for producing the first coarse powder and the second coarse powder and the subsequent steps may be performed in the same step. That is, the raw material of the first coarse powder (for example, a lump of a sintered body) and the raw material of the second coarse powder (for example, a strip cast alloy lump) are mixed before hydro-grinding, and this mixture is hydrogenated in the same step. A mixed coarse powder may be produced by crushing. In any case, in order to suppress oxidation, it is preferable to mix these materials before producing the first fine powder and the second fine powder.

As the second fine powder, it is preferable to use one prepared by a quenching method. This is because when the second fine powder produced by the quenching method is used, not only the magnetic properties are excellent but also the sinterability is excellent, and therefore the effect of supplementing the low sinterability of the first fine powder is high. It is speculated that the reason why the second fine powder produced by the quenching method has a high sinterability is that the R-rich phase is finely dispersed on the surface of the fine powder produced by the ingot method.

The oxygen content of the first fine powder and the second fine powder is preferably low. If the oxygen content is too high, the desired magnetic properties may not be obtained even within the above range of the compounding ratio. The oxygen content of the first fine powder is 1
It is in the range of 500ppm to 10000ppm, and the oxygen content of the second fine powder is 1500ppm to 7000p.
It is preferably in the range of pm. However, even if the oxygen content of the first fine powder exceeds the above range,
If a material having a low oxygen content is selected as the fine powder, sufficient magnetic properties may be obtained. The blending amount of the first fine powder may be set in consideration of the target magnetic characteristics.

In the following, according to a known method, a mixed powder is press-molded to form a molded body having a desired shape, which is optionally subjected to binder removal treatment, and the molded body is sintered and then aged. By performing the treatment, a sintered body is obtained.

The press molding of the mixed powder is performed, for example, by using an electric press, while orienting it in a magnetic field of about 0.2 MA / m to 4 MA / m, while applying 0.2 ton / cm ^{2 to} 2.0 ton /.
^{cm 2 (1.96 × 10 4 kPa~1.96} × 10 5 kP
It is carried out at the pressure of a).

The obtained molded body is, for example, about 1000 ° C.
Sintering is performed at a temperature of about 1100 ° C. in an inert gas (rare gas or nitrogen gas) atmosphere or in a vacuum for about 1 to about 5 hours. The obtained sintered body is, for example, about 450 ° C. to about 800 ° C.
By aging treatment at a temperature of about 1 to about 8 hours,
An R-Fe-B based alloy sintered body is obtained. The aging treatment may be omitted. Incidentally, in order to reduce the amount of carbon contained in the sintered body and improve the magnetic properties, before the sintering step,
If necessary, the lubricant covering the surface of the alloy powder may be removed by heating. The heat removal (binder removal) step is performed, for example, at a temperature of about 100 ° C. to about 600 ° C. in a reduced pressure atmosphere for about 0.5 hours to about 6 hours, depending on the type of lubricant. In addition, before sintering at a temperature of about 1000 ° C. to about 1100 ° C., the molded body is temporarily held at about 800 ° C. to about 950 ° C. for about 0.1 to 2.0 hours to remove hydrogenated rare earth elements. Sinterability can be improved by releasing hydrogen from the molded body containing the hydrogen.

By magnetizing the obtained sintered body,
The sintered magnet is completed. The magnetizing step can be performed at any time after the sintering step. The sintered body is completed through finishing (for example, chamfering) and surface treatment (for example, plating) as necessary. The rare earth alloy sintered body manufactured by the manufacturing method of the present invention may have substantially the same characteristics as the sintered body manufactured using only the second fine powder (new raw material powder).

Hereinafter, the method for producing a rare earth alloy sintered body and a sintered magnet according to the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

The first fine powder (regenerated raw material powder) is a defective rare earth alloy sintered body (about 500 g, about 50 mm × 38 mm).
X35 mm). Here, before being subjected to hydro-pulverization, the above-mentioned sintered body was mechanically pulverized by using a jaw crusher, and hydro-pulverization (in a 0.2 MPa hydrogen gas atmosphere in each of the obtained masses (mass)) was performed. Hold for 3 hours)
Then, the obtained coarse powder is further pulverized by a disc mill (for example, a gap width of 0.3 mm), and then finely pulverized by a jet mill (average particle diameter of fine powder: about 4.5 μm) to obtain a first powder. Fine powder (Sample No. 1 to 1 in Table 1
5) was obtained. The sample that was subjected to hydrogenation pulverization without pulverizing the sintered body could not be completely pulverized, and an unpulverized portion (core) remained near the center of the sintered body.

As the alloy ingot for producing the second fine powder, alloy flakes having a predetermined composition were produced by the strip casting method. Oxygen content in alloy flakes is 320 pp
It was m. A second coarse powder was obtained by pulverizing the alloy flakes by a hydro-pulverization method. The second coarse powder was further pulverized with a disc mill and then finely pulverized with a jet mill to obtain a second fine powder having an average particle diameter of about 4.5 μm. The jet mill pulverization for producing the first fine powder and the second fine powder was performed in a nitrogen gas atmosphere containing a slight amount of oxygen in order to suppress the oxidation of the rare earth element. The sintered body used as the raw material of the first fine powder is also formed by using the fine powder produced by the same manufacturing method as the second fine powder. The crushing process using a jet mill is described in JP-A-2002-33206 and US Patent Application No. 09 / 851,423.

Table 2 shows the compositions of the first fine powder and the second fine powder. The composition of the first fine powder shows the analysis value after crushing with a disk mill, and the composition of Sample No. All of 1 to 5 had substantially the same composition within the measurement error range. The numerical values in Table 2 are% by mass, and the balance not shown in the table is Fe and unavoidable impurities.

Sample No. A sintered body was produced using a mixed powder obtained by mixing 5% by mass of the first fine powder of 1 to 5 with the second fine powder. Further, a sintered body was produced using only the second fine powder (Sample No. 6).

The process after the press molding process was carried out under the following conditions.

The above-mentioned mixed powder (Sample Nos. 1 to 5) and the second fine powder (Sample No. 6) were press-molded (pressing pressure 0.8 ton / cm ² (7.84 × 10 ⁴ kPa), orientation magnetic field). 0.96 MA / m (1.2 T)) to obtain a molded product (length 40 mm x width 30 mm x height 20 mm)
Got The direction of the orientation magnetic field is the direction perpendicular to the compression direction. The compact was held in a reduced pressure Ar atmosphere at 900 ° C. for 1 hour for dehydrogenation treatment, and then sintered at 1050 ° C. for 4 hours. The obtained sintered body was subjected to an aging treatment at 500 ° C. for 1 hour and then processed into a test piece of 5.4 mm × 12 mm × 12 mm. The magnetic characteristics of the obtained sintered magnet are B-
Evaluation was performed using an H tracer. Table 1 shows the density and magnetic characteristics of the obtained sintered magnets (sintered bodies).

As can be seen from the results in Table 1, the magnetic properties (coercive force) deteriorate when the mass of the lump of the sintered body to be subjected to hydro-grinding exceeds 50 g. Furthermore, the mass of the sintered compact is 7
If it exceeds 0 g, the density of the sintered body also decreases. It is considered that the decrease in the density and magnetic properties of the sintered body is due to the fact that coarse powder, which should not be mixed, is mixed in the finely pulverized powder, resulting in a decrease in sinterability and generation of coarse crystal grains. . On the other hand, when the mass of the lump of the sintered body was 50 g or less, almost the same magnetic characteristics as when using only the second fine powder were obtained. Furthermore, when using a lump of 25 g or less,
Substantially the same magnetic properties were obtained as when only the second fine powder was used. From this, the mass of the lump of the sintered body to be subjected to the hydropulverization is preferably 50 g or less, and 25 g
The following is more preferable. That is, when the mass of the sintered body is 50 g or less, it is hydro-pulverized up to the vicinity of the center of the sintered body in the hydro-pulverization step, and then in the fine powder in the fine-pulverization step (for example, using a jet mill). It is possible to prevent the remaining hard powder. A step of removing the coarse powder remaining after the pulverizing step may be provided. Usually, the sintered body is 350 by mass.
It contains 0 ppm to 6500 ppm of oxygen.

Further, the size of the crystal grains (main phase) of the sintered body is preferably 20 μm or less. If the size of the crystal grains exceeds 20 μm, there is a problem that the pulverizability by the jet mill deteriorates.

Table 1 shows the results when the mixed powder in which the blending amount of the first fine powder was 5% by mass was used, and Table 3 shows the results of examining other blending amounts. Sample No. 1 in Table 1 was used as the first fine powder. The same as 5 was used. As is clear from Table 3, when the compounding amount of the first fine powder exceeds 15% by mass, the sintered density and the magnetic properties are decreased, while the content is 10%.
When the content is less than or equal to mass%, magnetic characteristics equivalent to those obtained when only the second fine powder was used were obtained.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

According to the present invention, there is provided a method for producing a rare earth alloy sintered body, which enables the rare earth alloy sintered body to be reused as a raw material more efficiently than before. In the method for producing a rare earth alloy sintered body according to the present invention, since it is not necessary to produce a rare earth alloy having a special composition because the regenerated raw material powder (first fine powder) produced from the rare earth alloy sintered body is used, It is easily performed without complicating the existing manufacturing process.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 38/00 303 C22C 38/00 303D H01F 1/08 H01F 1/08 B 41/02 41/02 G F Term (reference) 4K017 AA04 BA06 BB12 BB13 DA04 EA03 EA08 EK07 4K018 AA27 BA18 BB08 BC12 KA45 5E040 AA04 BD01 CA01 HB03 HB17 NN01 NN06 5E062 CC05 CD04 CE01 CG01

Claims (10)

[Claims] 1. A step of (a) producing a first coarse powder by coarsely pulverizing a rare earth alloy sintered body using a hydrogenation pulverization method, and (b) finely pulverizing the first coarse powder. By the first
A step of producing fine powder, (c) a step of producing second fine powder by crushing an alloy ingot of a rare earth alloy raw material, (d) including the first fine powder and the second fine powder And a step of sintering the mixed powder, wherein the first fine powder and the second fine powder are both (L
R _1-x HR _x ) ₂ T ₁₄ A (T is Fe, or Fe and Fe
Other than a transition metal element other than at least one, A is boron or a mixture of boron and carbon, LR is at least one light rare earth element, HR is at least one heavy rare earth element, 0 ≦ x <1) Having a main phase of composition represented by
A method for manufacturing a sintered body for a rare earth magnet. 2. The first fine powder and the second fine powder are both 25% by mass to 40% by mass of a rare earth element R.
(R = LR _1-x HR _x ) and 0.6% by mass to 1.6% by mass
The method for producing a sintered body for a rare earth magnet according to claim 1, which comprises A and A. 3. The rare earth alloy sintered body and the alloy ingot of the rare earth alloy raw material are both (LR _1-x HR _x ) ₂ T
_The method for producing a sintered body for a rare earth magnet according to claim 1 or 2, which contains 80% by volume or more of the compound represented by _14A . 4. The mass fraction of the first fine powder in the mixed powder is 0.1% or more of the mass of the second fine powder.
The method for producing a sintered body for a rare earth magnet according to claim 1, which is within a range of 0% or less. 5. The value of x in the composition formula of the main phase of the first fine powder and the value of x in the composition formula of the main phase of the second fine powder are different from each other, and The method for manufacturing a sintered body for a rare earth magnet according to claim 4, wherein the mass fraction of the first fine powder is less than 5% of the mass of the second fine powder. 6. The method according to claim 1, wherein in step (a), the rare earth alloy sintered body is subjected to coarse pulverization by a hydropulverization method as a plurality of lumps each having a weight of 50 g or less. A method for producing a sintered body for a rare earth magnet as described. 7. The step (c) comprises a step of coarsely crushing the alloy ingot to produce a second coarse powder, and a step of finely pulverizing the second coarse powder to produce the second fine powder. And mixing the first coarse powder and the second coarse powder, and then finely pulverizing the first coarse powder and the second coarse powder to obtain the first fine powder and the second fine powder. The method for producing a sintered body for a rare earth magnet according to claim 1, wherein a mixed powder with a powder is produced. 8. The step (c) comprises a step of coarsely crushing the alloy ingot to produce a second coarse powder, and a step of finely pulverizing the second coarse powder to produce the second fine powder. A step of producing a mixed coarse powder of the first coarse powder and the second coarse powder by hydrogenating and pulverizing in a state of mixing the alloy ingot and the rare earth alloy sintered body. The method for producing a sintered body for a rare earth magnet according to claim 1, wherein a mixed powder of the first fine powder and the second fine powder is produced by finely pulverizing the coarse powder. 9. The sintered body for a rare earth magnet according to claim 1, wherein the alloy ingot in the step (c) is produced by a quenching method from a molten metal of the rare earth alloy raw material. Production method. 10. The method for producing a sintered body for a rare earth magnet according to claim 1, wherein the rare earth alloy sintered body includes a defective sintered body for a rare earth magnet.