JP4730546B2 - Rare earth permanent magnet manufacturing method - Google Patents

Description

The present invention relates to an R-Fe-B permanent magnet having high heat resistance that prevents deterioration of magnetic properties due to grinding of the surface of a sintered magnet body, and in particular, the specific surface area (S / V) of the magnet body is 6 mm. ^{The present} invention relates to a method for producing a small or thin high-performance rare earth permanent magnet material of ^-1 or more.

R-Fe-B permanent magnets typified by Nd-Fe-B are excellent in magnetic properties, and thus their applications are increasingly widespread. In recent years, R-Fe-B magnets, especially computer-related equipment, hard disk drives, CD players, DVD players, mobile phones, and other electronic devices, including magnets, have become lighter, shorter, higher performance, and more energy efficient. In particular, there is a demand for downsizing and thinning of high-performance R-Fe-B sintered magnets, and the demand for small or thin magnets with a specific surface area S / V exceeding 6 mm ^-1 is increasing. I am doing.

  In order to process a small or thin R-Fe-B sintered magnet into a practical shape and mount it on a magnetic circuit, it is necessary to grind the sintered sintered block-shaped magnet. The outer peripheral blade cutting machine, the inner peripheral blade cutting machine, the surface grinding machine, the centerless polishing machine, the lapping machine, etc. are used.

However, it is known that when the R-Fe-B sintered magnet is ground by the above apparatus, the magnetic properties deteriorate as the magnet body becomes smaller. This is thought to be because the field structure is missing on the magnet surface due to processing. As a result of various studies on the coercive force in the vicinity of the surface of the R—Fe—B based sintered magnet, the present inventors have found that when the influence of processing strain is suppressed as much as possible while paying attention to the processing speed, deterioration on the processing surface to be ground. It has been found that the average thickness of the layer is approximately the same as the average grain size determined from the area ratio of the magnet main phase. Furthermore, in order to reduce the deterioration of magnetic characteristics, a magnetic material in which the crystal grain size is controlled to 5 μm or less in the magnet manufacturing process has been proposed by the present inventors (Patent Document 1: Japanese Patent Application Laid-Open No. 2004-281492). ). According to Patent Document 1, the characteristic deterioration rate can be suppressed to 15% or less even with a micro magnet having an S / V exceeding 6 mm ⁻¹ . However, as a result of the development of the processing technology, it has become possible to produce a magnet body having an S / V exceeding 30 mm ⁻¹ , resulting in a problem that the deterioration of their magnetic properties becomes 15% or more.

The present inventors have also found a manufacturing method for recovering the magnetic properties of surface particles by dissolving only the grain boundary phase and diffusing it in the surface to be ground, with respect to a sintered magnet body that has been ground to a small size. (Patent Document 2: JP-A No. 2004-281493). However, even in a magnet body manufactured using this technique, there is a problem that the corrosion resistance is inferior when the S / V exceeds 30 mm ⁻¹ .

On the other hand, the HDDR method (Hydrogenation-Deposition-Desorption-Recombination), which is one of the methods for producing R-Fe-B bonded magnet powder, is converted into R ₂ Fe ₁₄ B compound of the main phase by heat treatment in a hydrogen atmosphere. A heat treatment method in which a disproportionation reaction is caused to decompose into RH ₂ , Fe, and Fe ₂ B, and then hydrogen is released by lowering the hydrogen partial pressure to recombine with the original R ₂ Fe ₁₄ B compound. (Non-Patent Document 1). The magnet powder produced by the HDDR method is composed of crystal grains of about 200 nm, which is one digit or more smaller than a sintered magnet, so that the properties existing on the magnet surface are deteriorated in a 150 μm powder (S / V = 40). Is 1% by volume or less, and no significant deterioration in properties is observed. Furthermore, by controlling the disproportionation and recombination reaction in the HDDR process, it is possible to achieve miniaturization while retaining the crystal orientation of the original R ₂ Fe ₁₄ B crystal grains. Can be produced. Compared to the isotropic powder produced by the liquid quenching method, there is a merit that very high magnetic properties can be obtained, but the maximum energy product of the bond magnet produced by the above method is about 17 to 25 MGOe, It remains at a low value of less than half that of sintered magnets.

  By the way, in order to increase the heat resistance of the R—Fe—B magnet, a method is known in which Dy or Tb is added as a part of R to increase the intrinsic coercive force. However, since Dy and Tb have an effect of suppressing the disproportionation reaction in hydrogen, the HDDR method cannot be applied to an alloy containing many of them.

  As described above, it has been considered that it is practically difficult to produce an R—Fe—B ultrafine magnet body that exhibits no deterioration in magnetic properties and exhibits high magnetic properties and high heat resistance.

JP 2004-281492 A JP 2004-281493 A

In view of the above-described conventional problems, the present invention provides a method for producing a rare earth permanent magnet material as an R ¹ —Fe—B anisotropic sintered magnet material in which deterioration of magnetic properties due to grinding is recovered. It is for the purpose.

The inventors of the present invention conducted extensive research on the above-mentioned problems. After the sintered magnet body after grinding was subjected to a disproportionation treatment and a recombination reaction in a hydrogen atmosphere, R ² Deterioration due to heat treatment in vacuum or inert gas with a powder containing one or more selected from oxides, fluorides of R ³ and oxyfluorides of R ⁴ present on the magnet surface It has been found that the coercive force can be increased while recovering, and the present invention has been completed.

That is, this invention provides the manufacturing method of the following rare earth permanent magnet materials.
Claim 1:
It is obtained by molding and sintering a fine powder of a mother alloy containing R ¹ , Fe, and B with a compression molding machine while orienting it in a magnetic field, and has a composition formula R ¹ _x (Fe _1-y Co _y ) _{100 -xza} B _z M _a (R ¹ is one or more selected from rare earth elements including Sc and Y, and M is Al, Cu, Zn, In, Si, P, S, Ti, V, Cr , Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, and W, and x, y, z, and a are An anisotropic sintered magnet body represented by an atomic ratio of 10 ≦ x ≦ 15; 0 ≦ y ≦ 0.4; 3 ≦ z ≦ 15; 0 ≦ a ≦ 11) has a specific surface area of 6 mm. after grinding to be ^-1 or more, R ¹ ₂ Fe ₁₄ B-type main phase by heat treatment at 600～1,100 ° C. in an atmosphere containing hydrogen gas Cause disproportionation reaction compound, subsequently by heat treatment at 600～1,100 ° C. in an atmosphere having a reduced hydrogen gas partial pressure, causing a recombination reaction to the R ¹ ₂ Fe ₁₄ B type compound The crystal grains of the R ¹ ₂ Fe ₁₄ B type compound phase are refined to 1 μm or less, and then one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride (R ² , R ³ , R ⁴ are one or more selected from rare earth elements including Sc and Y) and a powder having an average particle diameter of 100 μm or less is present on the surface of the processed magnet R ² , R contained in the powder by subjecting the magnet and the powder to a heat treatment in a vacuum or an inert gas at a temperature equal to or lower than the heat treatment temperature in the atmosphere in which the partial pressure of hydrogen gas is reduced ³ , one or more of R ^{4 in} the magnet A method for producing a rare earth permanent magnet material, wherein the rare earth permanent magnet material is absorbed.
Claim 2:
2. The method for producing a rare earth permanent magnet material according to claim 1, wherein the abundance of the powder is 10% by volume or more in an average occupancy ratio in a space surrounding the processed magnet body having a distance of 1 mm or less from the surface of the processed magnet. .
Claim 3:
Oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, R ^2, R ³ or R ⁴ to 10 atomic% or more Dy and The rare earth permanent magnet according to claim 1 or 2, wherein Tb is contained and the total concentration of Nd and Pr in R ² , R ³ or R ⁴ is lower than the total concentration of Nd and Pr in R ¹ . Material manufacturing method.
Claim 4:
Oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, the 40 mass% or more of R ³ fluoride and / or R ⁴ One or two or more selected from the oxides of R ² , carbides of R ⁵ , nitrides, oxides, hydroxides, hydrides (R ⁵ is Sc and Y). 4. The method for producing a rare earth permanent magnet material according to claim 1, comprising one or more selected from rare earth elements. 5.
Claim 5:
5. The rare earth permanent magnet material according to claim 4, wherein fluorine contained in the powder containing one or more selected from R ³ fluoride and R ⁴ oxyfluoride is absorbed by the processed magnet. Manufacturing method.
Claim 6:
The permanent magnet material according to any one of claims 1 to 5, wherein the ground work magnet is washed with at least one of an alkali, an acid, and an organic solvent before the disproportionation reaction treatment. Manufacturing method.
Claim 7:
The method for producing a permanent magnet material according to any one of claims 1 to 6, wherein the surface deteriorated layer of the ground machined magnet is removed by shot blasting before the disproportionation reaction treatment.
Claim 8:
The method for producing a permanent magnet material according to any one of claims 1 to 7, wherein the processed magnet subjected to the absorption treatment with the powder is washed with at least one of an alkali, an acid, and an organic solvent.
Claim 9:
The method for producing a permanent magnet material according to any one of claims 1 to 8, wherein the machined magnet subjected to the absorption treatment with the powder is further ground.
Claim 10:
2. The machined magnet is subjected to an absorption treatment with the powder, and then plated or painted after washing with any one or more of the alkali, acid or organic solvent after the absorption treatment, or after grinding. The method for producing a permanent magnet material according to claim 9.

According to the present invention, it is possible to provide a small or thin rare earth permanent magnet with S / V = 6 mm ⁻¹ or more that exhibits good magnetic properties and high heat resistance by preventing deterioration of magnetic properties due to grinding.

The present invention is a small or thin high heat resistance in which the specific surface area S / V of the magnet body is 6 mm ⁻¹ or more, preventing deterioration of magnetic properties due to grinding of the surface of the R ¹ —Fe—B sintered magnet body material. Is a method for producing a conductive rare earth permanent magnet material.
Here, the R ¹ —Fe—B based sintered magnet body material can be obtained by roughly pulverizing, finely pulverizing, molding, and sintering the mother alloy according to a conventional method.
In the present invention, R and R ¹ are both selected from rare earth elements including Sc and Y. R is mainly used for the obtained magnet body, and R ¹ is mainly used for the starting material. .

In this case, the master alloy contains R ¹ , Fe, and B. R ¹ is one or more selected from rare earth elements including Sc and Y, specifically, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er , Yb and Lu, preferably Nd and Pr. These rare earth elements including Sc and Y are preferably 10 to 15 atomic%, particularly 11.5 to 15 atomic% of the whole alloy, and more preferably Nd and Pr or any ^{one of} them in R ¹ is 10 atomic%. As mentioned above, it is suitable to contain especially 50 atomic% or more. B is preferably contained in an amount of 3 to 15 atom%, particularly 5 to 8 atom%. In addition, Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, One or two or more selected from W may be contained in an amount of 0 to 11 atomic%, particularly 0.1 to 4 atomic%. The balance is inevitable impurities such as Fe or C, N, and O, but Fe is preferably contained in an amount of 50 atomic% or more, particularly 65 atomic% or more. Further, a part of Fe, for example, 0 to 40 atomic%, particularly 0 to 20 atomic% of Fe may be substituted with Co.

The mother alloy can be obtained by melting a raw metal or alloy in a vacuum or an inert gas, preferably in an Ar atmosphere, and then casting it in a flat mold or a book mold, or by strip casting. Also, an alloy close to the R ₂ Fe ₁₄ B compound composition that is the main phase of this alloy and an R-rich alloy that becomes a liquid phase aid at the sintering temperature are separately prepared, and are weighed and mixed after coarse pulverization. A two alloy method is also applicable to the present invention. However, for alloys close to the main phase composition, α-Fe tends to remain depending on the cooling rate during casting and the alloy composition, and it is homogeneous as necessary for the purpose of increasing the amount of R ₂ Fe ₁₄ B compound phase. The process is applied. The conditions are heat treatment in a temperature range of 700 to 1,200 ° C. in vacuum or Ar atmosphere for 1 hour or more. In addition to the casting method described above, a so-called liquid quenching method can be applied to the R-rich alloy serving as the liquid phase aid.

  Brown mill or hydrogen pulverization is used for the coarse pulverization process, and hydrogen pulverization is preferable in the case of an alloy produced by strip casting. The coarse powder is pulverized by a jet mill using high-pressure nitrogen. The fine powder is molded by a compression molding machine while being oriented in a magnetic field, and is put into a sintering furnace. Sintering is usually performed at 900 to 1,250 ° C, particularly 1,000 to 1,100 ° C in a vacuum or an inert gas atmosphere.

The composition of the sintered magnet body (sintered block) thus obtained has the composition formula R ¹ _x (Fe _{1 -y} Co _y ) _100-xza B _z M _a (R ¹ is a rare earth element containing Sc and Y) One or two or more selected from M, M is Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, It is one or more selected from Ag, Cd, Sn, Sb, Hf, Ta and W, and x, y, z and a are atomic ratios, respectively 10 ≦ x ≦ 15; 0 ≦ y ≦ 0 4; 3 ≦ z ≦ 15; 0 ≦ a ≦ 11).

  The obtained sintered body (sintered block) is ground into a practical shape. However, in order to minimize the influence of processing strain as much as possible, it is preferable to reduce the processing speed as long as productivity is not lowered. In this case, the grinding method can be carried out according to a conventional method, but the processing speed is preferably 0.1 to 20 mm / min, particularly preferably 0.5 to 10 mm / min.

In this case, as the grinding amount, the specific surface area S / V (surface area mm ² / volume mm ³ ) of the sintered block is 6 mm ⁻¹ or more, preferably 8 mm ⁻¹ or more. The upper limit is appropriately selected and is not particularly limited, but is usually 45 mm ⁻¹ or less, particularly 40 mm ⁻¹ or less.

  When water-based coolant is used for the grinding machine or when the grinding surface is exposed to high temperatures during processing, an oxide film tends to form on the surface to be ground, and this oxide film absorbs and releases hydrogen on the surface of the magnet body. May interfere. In such a case, an appropriate heat treatment in hydrogen can be performed by cleaning with one or more of alkali, acid, or organic solvent, or by performing shot blasting to remove the oxide film.

  The alkali includes potassium pyrophosphate, sodium pyrophosphate, potassium citrate, sodium citrate, potassium acetate, sodium acetate, potassium oxalate, sodium oxalate and the like. The acid includes hydrochloric acid, nitric acid, sulfuric acid, acetic acid, citric acid. As the organic solvent such as acid and tartaric acid, acetone, methanol, ethanol, isopropyl alcohol and the like can be used. In this case, the alkali or acid can be used as an aqueous solution having an appropriate concentration that does not erode the magnet body.

Next, the magnet body processed in a small size as described above is subjected to HDDR processing with the following pattern. That is, after grinding the anisotropic sintered magnet body so that the specific surface area becomes 6 mm ⁻¹ or more, the main phase R ¹ ₂ Fe is subjected to heat treatment in an atmosphere containing hydrogen gas at 600 to 1,100 ° C. causing disproportionation to ₁₄ B type compound, subsequently by heat treatment at 600～1,100 ° C. in an atmosphere having a reduced hydrogen gas partial pressure results in recombination reactions to R ¹ ₂ Fe ₁₄ B type compound By refining, the crystal grains of the R ¹ ₂ Fe ₁₄ B type compound phase are refined to 1 μm or less, and one or more of R ² , R ³ , R ⁴ contained in the powder are added to the magnet Is absorbed.

Further, this treatment will be described in detail. In the disproportionation reaction treatment, heating is usually started after the magnet body is put into the furnace. However, an inert gas atmosphere such as vacuum or argon is used between room temperature and 300 ° C. It is preferable that This is because if the atmosphere contains hydrogen in this temperature range, hydrogen atoms are taken in between the lattices of the R ¹ ₂ Fe ₁₄ B compound, the volume of the magnet body expands, and the magnet body may collapse. From 300 ° C. to the processing temperature (600 to 1,100 ° C., preferably 700 to 1,000 ° C.), depending on the composition of the magnet body and the rate of temperature increase, the temperature should be increased with a hydrogen partial pressure of 100 kPa or less. Is preferred. In addition, it is preferable that a temperature increase rate shall be 1-20 degrees C / min. The reasons for limiting the pressure are as follows. When the temperature is raised at a hydrogen partial pressure exceeding 100 kPa, the decomposition reaction of the R ¹ ₂ Fe ₁₄ B compound starts in the temperature raising process (depending on the magnet composition, but 600 to 700 ° C.). This is because it may grow and hinder the anisotropy when recombining with the R ¹ ₂ Fe ₁₄ B compound in the subsequent dehydrogenation treatment. After reaching the treatment temperature, depending on the magnet composition, the hydrogen partial pressure is increased to 100 kPa or more, preferably 10 minutes to 10 hours, more preferably 20 minutes to 8 hours, even more preferably 30 minutes to 5 hours. A disproportionation reaction is caused to occur in the R ¹ ₂ Fe ₁₄ B compound. By this disproportionation reaction, the R ¹ ₂ Fe ₁₄ B compound is decomposed into R ¹ H ₂ , Fe, and Fe ₂ B. The reason for limiting the time is that the disproportionation reaction does not proceed sufficiently, and in addition to the products R ¹ H ₂ , α-Fe, Fe ₂ B, unreacted R ¹ ₂ Fe ₁₄ B compound Therefore, if the heat treatment is performed for a long time, the magnetic properties are deteriorated due to unavoidable oxidation, so that the time is within 10 hours. More preferably, it is 30 minutes to 5 hours. Further, it is preferable to increase the hydrogen partial pressure stepwise during the isothermal treatment. If the hydrogen partial pressure is increased without stepping, the reaction will occur excessively and the decomposition structure becomes non-uniform, and the crystal grain size will be reduced when recombining with the R ¹ ₂ Fe ₁₄ B compound in the subsequent dehydrogenation treatment. This is because the coercive force and the squareness may be reduced due to non-uniformity.

  In addition, as above-mentioned, although hydrogen partial pressure is 100 kPa or more, Preferably it is 100-200 kPa, More preferably, it is 150-200 kPa. As for the method of gradually increasing the hydrogen partial pressure, for example, when the hydrogen partial pressure in the temperature rising process is 20 kPa and the final hydrogen partial pressure is 100 kPa, the first 30% of the holding time after reaching the holding temperature. The hydrogen partial pressure can be increased stepwise by the procedure of setting the hydrogen partial pressure to 50 kPa until time.

Next, a recombination reaction process is performed after the disproportionation reaction process. In this case, the treatment temperature is the same as that in the disproportionation reaction treatment. The treatment time is preferably 10 minutes to 10 hours, more preferably 20 minutes to 8 hours, and further preferably 30 minutes to 5 hours. In this case, the recombination reaction is performed in an atmosphere with a reduced hydrogen gas partial pressure, and depends on the alloy composition, but under a hydrogen partial pressure of 1 kPa to 10 ⁻⁵ Pa, particularly 10 Pa to 10 ⁻⁴ Pa. It is preferable to carry out the treatment.
After the recombination reaction treatment, the temperature can be lowered to room temperature at a rate of about -1 to -20 ° C / min.

In the present invention, the magnet body thus heat-treated in hydrogen is then used for one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride (R ² , R ³ and R ⁴ are composed of one or more selected from rare earth elements including Sc and Y), and a powder having an average particle size of 100 μm or less is present.

Incidentally, specific examples of R ^2, R ^3, R ⁴ is the same as R ^1, R ¹ and R ^2, R ^3, may be being the same or different and R ^4.
In this case, the oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, R ^2, R ³ or R ⁴ to 10 atomic% or more More preferably 20 atomic% or more, especially 40 to 100 atomic% of Dy and / or Tb, and the total concentration of Nd and Pr in R ² , R ³ or R ⁴ is the sum of Nd and Pr in R ¹ Lower than the concentration is preferred for the purposes of the present invention.

Further, the oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, a fluoride of 40 wt% or more of R ³ and / or R ⁴ oxyfluoride is contained, and the balance is one or more selected from R ² oxide, R ⁵ carbide, nitride, oxide, hydroxide, hydride (R ⁵ is Sc and Y 1 type or 2 types or more selected from rare earth elements containing) is preferable from the viewpoint of absorbing R with high efficiency.

Oxide of R ² in the present invention, fluoride of R ^3, and oxyfluoride of R ^4, preferably each _{^{R 2 2 O 3, R 3}} F 3, R 4 is a OF, other than this R ² O _n , R ³ F _n , R ⁴ O _m F _n (m and n are arbitrary positive numbers), and those in which a part of R ^{2 to} R ⁴ is substituted or stabilized by a metal element, etc. This means an oxide containing R ² and oxygen, a fluoride containing R ³ and fluorine, and an oxyfluoride containing R ⁴ , oxygen and fluorine.

The oxide powder is present on the magnet surface is R ^2, fluoride of R ^3, oxyfluoride of R ^4, or to mixtures thereof, a hydroxide of R ² to R ⁴ In addition, carbide In addition, at least one of nitrides, or a mixture or composite thereof may be included. Furthermore, in order to promote the dispersibility of the powder and chemical / physical adsorption, fine powders such as boron, boron nitride, silicon, and carbon, and organic compounds such as stearic acid can also be included. In order to achieve the effect of the present invention with high efficiency, the oxide of R ² , the fluoride of R ³ , the oxyfluoride of R ⁴ , or a mixture thereof is 40% by mass or more, preferably 60% by mass with respect to the whole powder. % Or more, more preferably 80% by mass or more, and may be 100% by mass.

In the present invention, one or more selected from R ² , R ³ , and R ⁴ are absorbed in the magnet body by the treatment described later, but the higher the occupation ratio by the powder in the magnet surface space, the higher the absorption. Since the amount of R ² , R ^3, or R ⁴ increases, the occupancy ratio is 10% by volume or more, preferably 40 volumes, in an average value in the space surrounding the magnet body with a distance of 1 mm or less from the surface of the magnet body. % Or more. The upper limit is not particularly limited, but is usually 95% by volume or less, particularly 90% by volume or less.

As a method for the presence of powder, for example oxide of R ^2, fluoride of R ^3, by dispersing fine powder containing one or more kinds selected from an acid fluoride of R ⁴ in water or an organic solvent, Examples include a method in which a magnet body is immersed in this slurry and then dried by hot air or vacuum, or is naturally dried. In addition, application by spraying is also possible. In any specific method, it can be said that it can be processed very easily and in large quantities. The content of the fine powder in the slurry can be 1 to 90% by mass, particularly 5 to 70% by mass.

The particle diameter of the fine powder affects the reactivity when the R ² , R ³ or R ⁴ component of the powder is absorbed by the magnet, and the smaller the particle, the greater the contact area involved in the reaction. Therefore, in order to achieve the effect of the present invention, the average particle size of the existing powder is 100 μm or less, preferably 10 μm or less. The lower limit is not particularly limited, but is preferably 1 nm or more, particularly 10 nm or more. The average particle diameter can be obtained as a mass average value D ₅₀ (that is, a particle diameter or a median diameter when the cumulative mass is 50%) using a particle size distribution measuring device using a laser diffraction method, for example. it can.

As described above, in the state where one or more powders selected from the oxide of R ² , the fluoride of R ^{3 and} the oxyfluoride of R ⁴ are present on the surface of the magnet body, Heat treatment is performed at a temperature equal to or lower than the sintering temperature in a vacuum or an inert gas atmosphere such as Ar or He (hereinafter, this treatment is referred to as absorption treatment). In this case, the heat treatment temperature (absorption treatment temperature) is equal to or lower than the temperature of the heat treatment for releasing hydrogen in the aforementioned reduced-pressure hydrogen. The reasons for limiting the treatment temperature are as follows.

When processing at a temperature higher than the heat treatment for releasing hydrogen (referred to as T _DR ° C), (1) crystal grains grow and high magnetic properties cannot be obtained, and (2) the processing dimensions cannot be maintained due to thermal deformation. 3) Since the diffused R (R ^{2 to} R ⁴ ) diffuses not only to the crystal grain interface of the magnet but also to the inside, and the residual magnetic flux density is lowered, the processing temperature is T _DR ° C or less. The temperature is preferably (T _DR -10) ° C. or lower. In addition, although the minimum of processing temperature is selected suitably, it is preferable that it is 260 degreeC or more, especially 310 degreeC or more.

  Absorption treatment time is 1 minute to 10 hours. If it is less than 1 minute, the absorption treatment is not completed, and if it exceeds 10 hours, the structure of the sintered magnet is altered, and inevitable oxidation and evaporation of components adversely affect the magnetic properties. More preferably, it is 5 minutes to 8 hours, particularly 10 minutes to 6 hours.

By the absorption treatment as described above, R contained in the powder existing on the surface of the magnet at the grain boundary portion of the magnet diffuses and concentrates, and this R is the surface layer of the main phase R ¹ ₂ Fe ₁₄ B type compound particles. Part, mainly a region having a depth of about 1 μm or less. Further, a part of the fluorine contained in the powder is absorbed in the magnet together with R, so that the supply from the powder of R and the diffusion at the crystal grain boundary of the magnet are remarkably enhanced. The rare earth element contained in the oxide of R, the fluoride of R, and the oxyfluoride of R is one or more selected from the rare earth elements including Sc and Y. Since elements having a particularly large effect of increasing anisotropy are Dy and Tb, the ratio of Dy and / or Tb as the rare earth element contained in the powder is 10 atomic% or more, particularly 20 atomic% or more. Is preferred. More preferably, it is 50 atomic% or more, and may be 100 atomic%. As a result of this absorption treatment, the coercive force of the R—Fe—B sintered magnet whose crystal grains are refined by heat treatment in hydrogen is efficiently increased.

  In the above absorption treatment, the magnets put in the container are covered with powder and the magnets are separated from each other, so that the magnets are not welded after the absorption treatment despite the heat treatment at a high temperature. Furthermore, since the powder does not adhere to the magnet after the heat treatment, it can be processed by putting a large amount of magnets in the container, and the production method according to the present invention is excellent in productivity.

  The magnet body subjected to the absorption treatment can be washed with water or an organic solvent as necessary to remove the powder present on the surface of the magnet body.

  Before performing the above disproportionation reaction treatment, the processed magnet processed into a predetermined shape is washed with at least one of alkali, acid or organic solvent, or the surface layer of the processed magnet is removed by shot blasting. can do.

  Further, the processed magnet subjected to the absorption treatment can be cleaned with any one or more of alkali, acid or organic solvent, and further subjected to grinding processing, or after the absorption processing, after the above washing, after grinding processing Either can be plated or painted.

  In addition, what was demonstrated previously can be used as an alkali, an acid, and an organic solvent, The said washing | cleaning process, a shot blasting process, a grinding process, plating, and a coating process can be performed according to a conventional method.

  According to the present invention, it is possible to provide a small-sized or thin permanent magnet having no characteristic deterioration and high heat resistance.

  Hereinafter, although the specific aspect of this invention is explained in full detail with an Example and a comparative example, the content of this invention is not limited to this. In the following examples, the occupation ratio (existence ratio) of the magnet surface space by dysprosium fluoride or the like was calculated from the dimensional change, mass increase and the true density of the powder substance after the powder treatment. Furthermore, with respect to the average crystal grain size of the sintered magnet body, a sample obtained by mirror-polishing a surface parallel to the orientation direction on a small piece cut out from the sintered body block and then corroding it at room temperature for 3 minutes using a villera liquid The optical microscope image was obtained by image analysis. In image analysis, the area of 500 to 2,500 crystal grains was measured, and after calculating the diameter of an equivalent circle, the average value was calculated when plotted on a histogram with the vertical axis representing the area fraction. . Further, the average crystal grain size of the magnet body according to the present invention after HDDR treatment was obtained by observing the fracture surface of the magnet with a scanning electron microscope and analyzing the secondary electron image. In the image analysis at this time, the linear intercept method was used.

[Example 1 and Comparative Example 1]
Nd, Fe, Co, Al metal having a purity of 99% by mass or more and ferroboron are weighed in predetermined amounts and melted at high frequency in an Ar atmosphere, and the molten alloy is poured into a single copper roll in an Ar atmosphere by a strip casting method. A shaped alloy was obtained. The composition of the obtained alloy is 12.5 atomic% Nd-1.0 atomic% Co-1.0 atomic% Al-5.9 atomic% B-balance Fe, which is referred to as Alloy A. The alloy A was occluded with hydrogen and then heated to 500 ° C. while being evacuated to partially release hydrogen, so that a coarse powder of 30 mesh or less was obtained by so-called hydrogen pulverization.

  Further, Nd, Dy, Fe, Co, Al, Cu metal having a purity of 99% by mass or more and ferroboron were weighed in predetermined amounts, melted by high frequency in an Ar atmosphere, and then cast. The composition of the obtained alloy is 20 atomic% Nd-10 atomic% Dy-24 atomic% Fe-6 atomic% B-1 atomic% Al-2 atomic% Cu-balance Co. This is referred to as Alloy B. Alloy B was coarsely pulverized to 30 mesh or less using a brown mill in a nitrogen atmosphere.

Subsequently, 90% by mass of the alloy A powder and 10% by mass of the alloy B powder were weighed and mixed for 30 minutes in a nitrogen-substituted V blender. This mixed powder was finely pulverized by a jet mill using high-pressure nitrogen gas to a mass median particle size of 4 μm. The obtained mixed fine powder was molded at a pressure of about 1 ton / cm ² while being oriented in a magnetic field of 15 kOe under a nitrogen atmosphere. Next, this molded body was put in a sintering furnace in an Ar atmosphere, and sintered at 1,060 ° C. for 2 hours to produce a sintered body block having dimensions of 10 mm × 20 mm × thickness 15 mm. The average crystal grain size of the sintered body was 5.2 μm. The sintered body block was ground on a rectangular parallelepiped having a predetermined size so that the specific surface area S / V was 22 mm ⁻¹ by an inner peripheral cutting machine.

The ground sintered body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
The sintered body is subjected to HDDR treatment (disproportionation reaction treatment and recombination treatment) under the conditions schematically shown in FIG. 1, washed with ethyl alcohol to which ultrasonic waves are applied, and dried to obtain the magnet body of the present invention. Got. This is referred to as a magnet body P1.

Next, dysprosium fluoride having an average powder particle size of 5 μm was mixed with ethanol at a mass fraction of 50%, and the sintered body was immersed for 1 minute while applying ultrasonic waves thereto. The raised sintered body was immediately dried with hot air. At this time, dysprosium fluoride surrounded a space having an average distance of 15 μm from the surface of the magnet, and the occupation ratio was 45% by volume. This was subjected to an absorption treatment in an Ar atmosphere at 840 ° C. for 1 hour, ultrasonically washed with ethanol as a solvent, and then dried to obtain a magnet body. This is referred to as a magnet body M1. The average crystal grain size of the magnet body M1 was 0.45 μm.
Table 1 shows the magnetic properties of the magnet bodies M1 and P1. It can be seen that the present invention has increased the coercivity H _cJ by 350 kAm ⁻¹ .

[Example 2 and Comparative Example 2]
A sintered body block having a size of 10 mm × 20 mm × thickness 15 mm was produced by the same composition and production method as in Example 1. The sintered body block was ground on a rectangular parallelepiped having a predetermined size so that the specific surface area S / V was 24 mm ⁻¹ by an inner peripheral cutting machine.

The ground sintered body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
This sintered body was subjected to HDDR treatment under the conditions schematically shown in FIG. 1, washed with ethyl alcohol to which ultrasonic waves were applied, and dried to obtain the magnet body of the present invention. This is referred to as a magnet body P2.

Next, dysprosium oxide with an average powder particle size of 1 μm, dysprosium fluoride with 5 μm, and ethanol are mixed so that the mass fraction is 25%, 25%, and 50%, and ultrasonic waves are applied thereto. Then, the sintered body was immersed for 1 minute. The raised sintered body was immediately dried with hot air. At this time, dysprosium oxide and dysprosium fluoride surrounded a space having an average distance of 15 μm from the surface of the magnet, and the occupation ratio was 50% by volume. This was subjected to an absorption treatment in an Ar atmosphere at 840 ° C. for 1 hour, ultrasonically washed with ethanol as a solvent, and then dried to obtain a magnet body. This is referred to as a magnet body M2. The average crystal grain size of the magnet body M2 was 0.52 μm.
Table 1 shows the magnetic properties of the magnet bodies M2 and P2. It can be seen that the present invention has increased the coercivity H _cJ by 300 kAm ⁻¹ .

[Example 3 and Comparative Example 3]
Strip casting method in which Nd, Co, Al, Fe, Cu metal having a purity of 99% by mass or more and ferroboron are weighed in predetermined amounts and melted at a high frequency in an Ar atmosphere, and the molten alloy is poured into a single copper roll in the Ar atmosphere. Thus, a thin plate-like alloy was obtained. The composition of the resulting alloy is 14.5 atomic% Nd, 1.0 atomic% Co, 0.5 atomic% Al, 0.2 atomic% Cu, 5.9 atomic% B, Fe is the balance Met. This was occluded with hydrogen and then heated to 500 ° C. while evacuating to release hydrogen partially, so that a coarse powder of 30 mesh or less was obtained by so-called hydrogen pulverization.

This coarse powder was finely pulverized to a mass median particle size of 4 μm by a jet mill using high-pressure nitrogen gas. The obtained mixed fine powder was molded at a pressure of about 1 ton / cm ² while being oriented in a magnetic field of 15 kOe under a nitrogen atmosphere. Next, this molded body was put in a sintering furnace in an Ar atmosphere, and sintered at 1,060 ° C. for 2 hours to produce a sintered body block having dimensions of 10 mm × 20 mm × thickness 15 mm. The average crystal grain size of the sintered body was 4.7 μm. The sintered body block was ground on a rectangular parallelepiped having a predetermined size so that the specific surface area S / V was 36 mm ⁻¹ by an inner peripheral cutting machine.

The ground sintered body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
The sintered body was subjected to HDDR treatment under the conditions schematically shown in FIG. 1, washed with ethyl alcohol to which ultrasonic waves were applied, and dried to obtain a magnet body. This is referred to as a magnet body P3.

Next, terbium fluoride having an average powder particle size of 5 μm was mixed with ethanol at a mass fraction of 50%, and the sintered body P3 was immersed for 1 minute while applying ultrasonic waves thereto. The raised sintered body was immediately dried with hot air. At this time, terbium fluoride surrounded a space having an average distance of 10 μm from the surface of the magnet, and the occupation ratio was 45% by volume. This was subjected to an absorption treatment in an Ar atmosphere at 840 ° C. for 1 hour, ultrasonically washed with ethanol as a solvent, and then dried to obtain a magnet body. This is referred to as a magnet body M3. The average crystal grain size of the magnet body M3 was 0.43 μm.
Table 1 shows the magnetic properties of the magnet bodies M3 and P3. It can be seen that the present invention increased the coercivity H _cJ by 650 kAm ⁻¹ .

[Example 4]
The magnet body M3 in Example 3 was washed with an alkaline solution and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning. This magnet body of the present invention is referred to as a magnet body M4.
Table 1 shows the magnetic properties of the magnet body M4. It can be seen that even if a cleaning step is added after the heat treatment, high magnetic properties are exhibited.

[Examples 5 and 6]
A sintered body block having a size of 10 mm × 20 mm × thickness 15 mm was produced by the same composition and production method as in Example 3. The sintered body block was ground on a rectangular parallelepiped having a predetermined size so that the specific surface area S / V was 6 mm ⁻¹ by an outer peripheral blade cutter.

The ground sintered body was washed with an alkaline solution, and then washed with an acid and dried. A cleaning process with pure water is included before and after each cleaning.
The sintered body was subjected to HDDR treatment under the conditions schematically shown in FIG. 1, washed with ethyl alcohol to which ultrasonic waves were applied, and dried to obtain a magnet body.

  Next, terbium fluoride having an average powder particle size of 5 μm was mixed with ethanol at a mass fraction of 50%, and the sintered body was immersed for 1 minute while applying ultrasonic waves thereto. The raised sintered body was immediately dried with hot air. At this time, terbium fluoride surrounded a space having an average distance of 10 μm from the surface of the magnet, and the occupation ratio was 45% by volume.

This was subjected to an absorption treatment in an Ar atmosphere at 840 ° C. for 1 hour, ultrasonically cleaned using ethanol as a solvent, and then dried. The magnet body was ground on a rectangular parallelepiped having a predetermined size so that the specific surface area S / V was 36 mm ⁻¹ by an inner peripheral cutting machine. This magnet body of the present invention is referred to as a magnet body M5. The average crystal grain size of the magnet body M5 was 0.47 μm.
The magnet body was further subjected to electroless copper / nickel plating to obtain a magnet body M6 of the present invention.
Table 1 shows the magnetic properties of the magnet bodies M5 and M6. Magnets that have been processed and plated after HDDR processing should have the same magnetic characteristics as M3 that has been ground and heat-treated until the specific surface area S / V reaches 36 mm ^-1 . I understand.

It is the schematic diagram which showed the heat processing pattern in Example 1,2,3.

Claims (10)

It is obtained by molding and sintering a fine powder of a mother alloy containing R ¹ , Fe, and B with a compression molding machine while orienting it in a magnetic field, and has a composition formula R ¹ _x (Fe _1-y Co _y ) _{100 -xza} B _z M _a (R ¹ is one or more selected from rare earth elements including Sc and Y, and M is Al, Cu, Zn, In, Si, P, S, Ti, V, Cr , Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, and W, and x, y, z, and a are An anisotropic sintered magnet body represented by an atomic ratio of 10 ≦ x ≦ 15; 0 ≦ y ≦ 0.4; 3 ≦ z ≦ 15; 0 ≦ a ≦ 11) has a specific surface area of 6 mm. after grinding to be ^-1 or more, R ¹ ₂ Fe ₁₄ B-type main phase by heat treatment at 600～1,100 ° C. in an atmosphere containing hydrogen gas Cause disproportionation reaction compound, subsequently by heat treatment at 600～1,100 ° C. in an atmosphere having a reduced hydrogen gas partial pressure, causing a recombination reaction to the R ¹ ₂ Fe ₁₄ B type compound The crystal grains of the R ¹ ₂ Fe ₁₄ B type compound phase are refined to 1 μm or less, and then one or more selected from R ² oxide, R ³ fluoride, and R ⁴ oxyfluoride (R ² , R ³ , R ⁴ are one or more selected from rare earth elements including Sc and Y) and a powder having an average particle diameter of 100 μm or less is present on the surface of the processed magnet R ² , R contained in the powder by subjecting the magnet and the powder to a heat treatment in a vacuum or an inert gas at a temperature equal to or lower than the heat treatment temperature in the atmosphere in which the partial pressure of hydrogen gas is reduced ³ , one or more of R ^{4 in} the magnet A method for producing a rare earth permanent magnet material, wherein the rare earth permanent magnet material is absorbed.   2. The method for producing a rare earth permanent magnet material according to claim 1, wherein the abundance of the powder is 10% by volume or more in an average occupancy ratio in a space surrounding the processed magnet body having a distance of 1 mm or less from the surface of the processed magnet. . Oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, R ^2, R ³ or R ⁴ to 10 atomic% or more Dy and The rare earth permanent magnet according to claim 1 or 2, wherein Tb is contained and the total concentration of Nd and Pr in R ² , R ³ or R ⁴ is lower than the total concentration of Nd and Pr in R ¹ . Material manufacturing method. Oxide of R ^2, fluoride of R ^3, the powder containing one or more kinds selected from an acid fluoride of R ^4, the 40 mass% or more of R ³ fluoride and / or R ⁴ One or two or more selected from the oxides of R ² , carbides of R ⁵ , nitrides, oxides, hydroxides, hydrides (R ⁵ is Sc and Y). 4. The method for producing a rare earth permanent magnet material according to claim 1, comprising one or more selected from rare earth elements. 5. 5. The rare earth permanent magnet material according to claim 4, wherein fluorine contained in the powder containing one or more selected from R ³ fluoride and R ⁴ oxyfluoride is absorbed by the processed magnet. Manufacturing method.   The permanent magnet material according to any one of claims 1 to 5, wherein the ground work magnet is washed with at least one of an alkali, an acid, and an organic solvent before the disproportionation reaction treatment. Manufacturing method.   The method for producing a permanent magnet material according to any one of claims 1 to 6, wherein the surface deteriorated layer of the ground machined magnet is removed by shot blasting before the disproportionation reaction treatment.   The method for producing a permanent magnet material according to any one of claims 1 to 7, wherein the processed magnet subjected to the absorption treatment with the powder is washed with at least one of an alkali, an acid, and an organic solvent.   The method for producing a permanent magnet material according to any one of claims 1 to 8, wherein the machined magnet subjected to the absorption treatment with the powder is further ground.   2. The machined magnet is subjected to an absorption treatment with the powder, and then plated or painted after washing with any one or more of the alkali, acid or organic solvent after the absorption treatment, or after grinding. The method for producing a permanent magnet material according to claim 9.

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