JP5910437B2 - Cu-containing rare earth-iron-boron alloy powder and method for producing the same - Google Patents

Description

  The present invention relates to a Cu-containing rare earth-iron-boron-based alloy powder and a method for producing the same, and more specifically, Cu-containing rare-earth-iron-boron-based alloy powder used for permanent magnets and its cost by reduction diffusion. It is related with the method of manufacturing efficiently.

A permanent magnet having at least one rare earth element as a constituent component is a rare earth element-iron-boron ("R-Fe-B") permanent magnet. The structure of this R—Fe—B permanent magnet is composed of an R ₂ Fe ₁₄ B phase, an R rich phase, and a B rich phase, and the magnet characteristics differ depending on the composition ratio of each phase. For this reason, R-Fe-B permanent magnets having compositions corresponding to permanent magnets having various characteristics have been proposed.

An R—Fe—B alloy powder is used as a raw material for the R—Fe—B permanent magnet, and a method for producing the alloy powder includes a melting method and a reduction diffusion method.
In the melting method, a component metal or mother alloy is prepared in a target composition, dissolved, and the resulting alloy lump is pulverized. For example, Patent Document 1 discloses a molten alloy containing R (R is at least one rare earth element including Y), T (T is Fe, or Fe and Co), and B as main components. , A method of manufacturing by cooling from one direction or two opposite directions by a single roll method, a twin roll method or a rotating disk method is described.

Patent Document 2 discloses that a rare earth metal-iron binary alloy melt is cooled at a rate of 100 to 1000 ° C./second and a supercooling degree of 200 to 500 ° C. by a strip casting method using a single roll through a tundish. Describes a method for producing a rare earth metal-iron binary alloy ingot for permanent magnets, which is uniformly solidified under the cooling conditions described above.
Furthermore, in the examples of Patent Document 3, Nd, electrolytic iron, ferroboron, Bi, and ferrotungsten are used as starting materials, blended so as to have a desired composition, alloyed by an arc melting method, and then homogenized. Examples of producing permanent magnets for heat treatment, coarse pulverization and fine pulverization are described.
However, these methods require a pulverization step, and the rare earth metal is highly active against oxidation, so that oxidation proceeds in the pulverization process and the alloy quality is lowered.

On the other hand, the reduction diffusion method mixes rare earth oxide powder, metal powder such as iron, nickel, cobalt, iron-boron alloy powder or boron oxide powder, and an alkaline earth metal as a reducing agent, and heats the raw material. The oxide is reduced, the rare earth metal and the transition metal are alloyed by a diffusion reaction, and then wet-processed to obtain an alloy powder. The alloy powder having a uniform composition is obtained at a lower cost than the melting method. Can do.
The reduction diffusion method is less expensive than the melting method, the heat treatment temperature is low, the structure of the obtained alloy is dense, the composition can be easily adjusted, and the alloy lump surface treatment, pulverization process, etc. Has many advantages such as no need. For example, Patent Document 4 discloses a method for producing an alloy by this reduction diffusion method. A rare earth oxide or halide is reduced by Ca in the presence of Fe and B to obtain 3 wt% to 20 wt% Fe, 0.5 wt%. It is described that an Fe—B—R intermediate raw material alloy consisting of 10% by weight to 10% by weight B and the balance being substantially a rare earth metal is obtained.
The present applicant also comprises 28 to 35% by weight of a rare earth element, 1.0 to 1.5% by weight of boron, and the balance iron or iron alloy, and the iron alloy contains at least one of nickel and cobalt. When the alloy powder for magnets to be produced is produced by the reduction diffusion method, the alloy powder is mixed, then molded at a pressure of 100 to 1000 kg / cm ² , and then subjected to a reduction diffusion reaction at 1000 to 1200 ° C. (For example, patent document 5).

In Patent Document 6, R (R is at least one of Nd, Pr, Dy, Ho, and Tb, or La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, and Y. In the production of a rare earth magnet alloy powder consisting mainly of tetragonal crystals of 12 atomic% to 20 atomic%, B4 atomic% to 20 atomic%, Fe 65 atomic% to 81 atomic% (mainly consisting of at least one kind) A mixed powder in which at least one of the rare earth oxides and at least one of iron powder and pure boron powder, ferroboron powder, and boron oxide, or an alloy powder or mixed oxide of the above constituent elements are mixed in the above composition. And 1.5 to 3.5 times the stoichiometric amount of metal Ca and 1 wt% to 15 wt% of CaCl ₂ of the rare earth oxide with respect to the amount of oxygen contained in the raw material powder such as the rare earth oxide. Mixed and not Reductive diffusion is performed by heating to 900 ° C. to 1200 ° C. in an active gas atmosphere, and the resulting reaction product is put into ion-exchanged water cooled to 15 ° C. or less to form a slurry. A method for producing an alloy powder for rare earth magnets characterized by treatment with ion-exchanged water cooled to ℃ or lower is described.

R-Fe-B permanent magnets have a high saturation magnetization among rare earth magnets, and thus have expanded their use to consumer small electronic devices, computer peripherals, MRI, industrial motors and automobiles. In recent years, hybrid vehicles and electric vehicles have begun to spread. However, in these applications, it is essential to add Dy to the R—Fe—B alloy in order to improve heat resistance and improve magnetic properties (Patent Document 4, 6). However, this element has a problem that the abundance ratio on the earth is about 10% of Nd, the price is about three times as high as Nd, and the supply is uneasy.
As a method to solve this problem, in order to make the Nd-Fe-B alloy powder finer, the production of alloy powder by the hydrogenation-disproportionation-dehydrogenation-recombination (HDDR) method has been developed. In addition, it has been reported that HDDR magnetic powder having a crystal grain size of 0.3 to 0.5 μm may exhibit a high coercive force even in a composition not containing Dy by hot pressing for a short time (non-Dy). Patent Document 1). However, this HDDR processing alloy is so poor in productivity that it requires a soaking process after melting and casting the raw material, and requires a hydrogen storage / disintegration processing step.

  On the other hand, Patent Document 7 discloses an adhesion step in which a permeation material (CuNd alloy) capable of generating a liquid phase at a temperature lower than the eutectic point of the magnetic alloy is adhered to the surface of the magnetic alloy containing the rare earth element by sputtering, and the adhesion A rare earth in which the crystal grains are encapsulated with at least constituent elements of the permeation material, comprising a permeation step of permeating and diffusing the permeation material into the grain boundaries of the crystal grains of the magnetic alloy by heating at 350 to 625 ° C. A method for producing a rare earth magnet is described, characterized in that a magnet is obtained. According to this method, a magnet having an ideal tissue structure with high coercive force can be obtained. However, the process for producing it is composed of a production process of a magnetic alloy containing rare earth elements, an adhesion material adhesion process and an infiltration process, and there are many problems in productivity.

Japanese Patent No. 3932143 Japanese Patent No. 3455552 JP 2004-6767 A Japanese Patent Publication No. 4-35548 JP 10-280002 A Japanese Patent Publication No. 6-922 JP 2011-61038 A

Hitachi Metals Technical Report, Vol. 27, (2011), 34-41

  The present invention has been made by paying attention to the above-mentioned problems in the production of the conventional Dy-free rare earth magnet, that is, low productivity, and the problem is that Cu used for permanent magnets is used. It is an object of the present invention to provide a rare earth-iron-boron based alloy powder and a method for efficiently producing the same by a reduction diffusion method.

As a result of intensive studies on Nd—Fe—B magnets not containing Dy in order to solve the above-mentioned problems, the present inventors have found that rare earth oxide powder or rare earth oxide powder and rare earth metal powder, iron-containing powder, boron-containing powder At least a specific amount of copper-containing powder is added to the raw material powder consisting of powder, mixed with a reducing agent selected from alkali metals or alkaline earth metals, and subjected to a reduction diffusion reaction under specific conditions, whereby Cu is mixed with Nd in the main phase. The present inventors have found that it can be present at the grain boundary between Nd ₂ Fe ₁₄ B grains, and have completed the present invention.

That is, according to the first invention of the present invention, it is sufficient to reduce the oxide powder to a raw material powder composed of rare earth oxide powder or rare earth oxide powder and rare earth metal powder, and iron-containing powder and boron-containing powder. A method for producing a Cu-containing rare earth-iron-boron alloy powder by a reduction diffusion method by mixing an amount of a reducing agent, wherein the rare earth oxide powder and the rare earth metal powder contain at least Nd as a rare earth element. In addition, one or two or more elements not containing Dy are contained, and a copper-containing powder is further mixed as a raw material powder, and the composition range of the copper-containing powder is 0.003 to 1.5% by weight in terms of Cu The mixture is heated to a temperature of 900 ° C. to 1200 ° C. for 0.5 hours or more in an inert gas atmosphere, and the resulting reaction product mixture is wet-treated and then dried. The Seen, the rare earth - iron - boron alloy powder, Cu derived from the containing copper powder is not present in the main phase particles containing at least a portion of Nd, the grain boundary between the main phase with the rest of Nd It is provided by a method for producing a Cu-containing rare earth-iron-boron alloy powder characterized by being present.

According to a second aspect of the present invention, there is provided a method for producing a Cu-containing rare earth-iron-boron alloy powder characterized in that in the first aspect, an aluminum-containing powder is further added.

According to a third aspect of the present invention, in the second aspect, the composition range of the aluminum-containing powder is 0.003 to 1.5% by weight in terms of Al. Provided by a method for producing an iron-boron alloy powder.

According to a fourth aspect of the present invention, there is provided a Cu-containing rare earth-iron-boron based alloy according to any one of the first to third aspects, wherein the heat treatment is held for 1 to 5 hours. Provided by a method for producing a powder.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, at least one flux selected from alkali metal chlorides and alkaline earth metal chlorides is used together with the reducing agent. It is provided by a method for producing a Cu-containing rare earth-iron-boron alloy powder.

According to the sixth aspect of the present invention, a Cu-containing rare earth-iron-boron alloy powder containing Nd ₂ Fe ₁₄ B particles as a main phase and not containing Dy, wherein the Cu is a main phase Nd ₂ Fe _14. There is provided a Cu-containing rare earth-iron-boron alloy powder characterized in that it is not present in B particles but is present together with Nd at grain boundaries between main phases.
According to a seventh aspect of the present invention, there is provided a Cu-containing rare earth-iron-boron based alloy powder characterized in that, in the sixth aspect, the average particle size is 1-150 μm.
According to the eighth invention of the present invention, in the sixth or seventh invention, Cu is further dispersed in the main phase Nd ₂ Fe ₁₄ B particles. Cu-containing rare earth-iron- Provided by boron based alloy powder.

According to the present invention, the Cu-containing rare earth-iron-boron alloy powder is produced by a specific reduction diffusion method, so that productivity is extremely high. Further, since Dy is not used as a raw material, the cost is low. Moreover, the Cu-containing rare earth-iron-boron alloy powder can be expected to have high magnetic properties because Cu exists together with Nd at the grain boundaries between the main phase Nd ₂ Fe ₁₄ B particles.

It is a photograph which shows the reflected electron image of the cross section SEM of Cu containing rare earth-iron- boron system alloy powder (alloy powder a) obtained by the present invention. It is a photograph which shows Nd distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder a) obtained by this invention. It is a photograph which shows Fe distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder a) obtained by this invention. It is a photograph which shows Cu distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder a) obtained by this invention. It is a photograph which shows the reflected electron image of the cross section SEM of Cu containing rare earth-iron- boron system alloy powder (alloy powder 1) obtained by the present invention. It is a photograph which shows Nd distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder l) obtained by this invention. It is a photograph which shows Fe distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder l) obtained by this invention. It is a photograph which shows Cu distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron type alloy powder (alloy powder l) obtained by this invention. It is a photograph which shows Al distribution of the cross-sectional SEM of Cu containing rare earth-iron- boron system alloy powder (alloy powder l) obtained by the present invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
In the present invention, a rare earth oxide powder or rare earth oxide powder and rare earth metal powder, and a raw material powder comprising iron-containing powder and boron-containing powder are mixed with a reducing agent in an amount sufficient to reduce the oxide powder. A method for producing a Cu-containing rare earth-iron-boron alloy powder by a diffusion method, wherein a specific amount of a copper-containing powder or a copper-containing powder and an aluminum-containing powder is further mixed as a raw material powder, and the mixture is inert gas atmosphere It heat-processes at the temperature of 900 to 1200 degreeC below, and after drying the obtained reaction product mixture, it is characterized by the above-mentioned.

1. Raw material powder Examples of rare earth elements used in the present invention include rare earth metal oxides such as Gd, Tb, Ho, Er, Tm, Yb, La, Ce, Pr, Nd, Sm, Eu, Lu, Pm, Y, and Sc. Powder or rare earth metal powder is used alone or in combination of two or more. Of these, Nd is essential. The purity is preferably 99.9% or more. The amount used is such that the composition range of the rare earth element is 20 to 30% by weight.

  The iron-containing raw material is preferably iron oxide powder or iron powder, and the boron-containing raw material is preferably alloy powder such as boron oxide powder or ferroboron powder. The purity is preferably 99% or more. The amount used is such that the composition range is Fe 65-77 wt% and B 0.5-2 wt%.

The copper-containing raw material is preferably copper oxide powder or copper powder. The purity is preferably 99% or more. Copper is alloyed with Nd and is used in an amount sufficient to exist at the grain boundaries of the particles formed by the main phases of Nd—Fe—B. The amount of Cu used is such that the composition range is 0.003 to 1.5% by weight. If it is less than 0.003% by weight, the magnetic isolation of the main phase Nd ₂ Fe ₁₄ B particles is insufficient, and if it exceeds 1.5% by weight, excess copper exists as Cu, and in any case, the magnetic properties are deteriorated. To do. The amount of Cu used is preferably in the composition range of 0.005 to 1.0% by weight, and more preferably 0.007 to 1.0% by weight.
In the present invention, the raw material powder can further contain an aluminum-containing raw material such as an aluminum oxide powder or an aluminum powder. The purity is preferably 99% or more. The amount of Al used is such that the composition range is 0.003 to 1.5% by weight. When 0.003% by weight or more is used, the magnetic isolation of the main phase Nd ₂ Fe ₁₄ B particles can be further increased. However, if it exceeds 1.5% by weight, excess aluminum may become an inhibitory element, and the magnetic properties may deteriorate.

  The particle size of the raw material powder is not particularly limited, but is desirably 50 μm or less. If it exceeds 50 μm, the mixing property is deteriorated, and it may be difficult to obtain an alloy powder having a uniform composition. The preferred range is 10 to 30 μm. The means for pulverizing and mixing each raw material powder is not particularly limited. For mixing, for example, a known mixer such as a V blender or an S blender can be used.

2. Reducing agent, flux In the present invention, the reducing agent is at least one selected from alkali metals, alkaline earth metals, and hydrides thereof, such as Li, Na, K, Ca, Mg, and the hydrides thereof. Are used alone or in combination of two or more. These reducing agents are used in the form of granules or powders, for example. Moreover, these reducing agents are used in a ratio that is 1.1 to 2.0 times the reaction equivalent amount (the stoichiometric amount necessary for reducing Nd ₂ O ₃ ). If the amount is too large, the residual amount increases after wet processing, so 1.1 to 1.5 times the amount is preferable.

In the method of the present invention, together with the reducing agent described above, for example, alkali metal chloride or alkaline earth metal chloride can be used as a flux as required. These can suppress the fusion and coarsening of the alloy powder in the reaction product obtained by the reduction diffusion reaction, and can improve the disintegration property in the wet process. Specifically, chlorides such as Li, Na, K, and Mg are preferable, and anhydrous ones that do not contain hydrates are particularly preferable. Most preferred is anhydrous calcium chloride which exhibits little volatility when heated and is advantageous in terms of cost. When the Nd source is an oxide, the use amount of these alkali metal chlorides or alkaline earth metal chlorides is preferably 1% by weight or more with respect to Nd ₂ O ₃ , and particularly a fine alloy powder is produced. In that case, it is desirable that the content be in the range of 3 to 20% by weight.

3. Reduction Diffusion Reaction Hereinafter, the reduction diffusion reaction in the present invention will be specifically described by taking as an example the case of producing an alloy powder using Nd ₂ O ₃ powder, Fe powder, FeB alloy powder, CuO powder and metallic calcium.
According to the method of the present invention, the mixture of the raw material components is heated and maintained in an inert gas atmosphere such as Ar gas at a temperature equal to or higher than a temperature at which the reducing agent melts and a temperature at which the alloy does not melt. .

  The heat treatment can be performed using a known heating furnace. Although it does not specifically limit as inert gas atmosphere, For example, Ar gas atmosphere is suitable. The heat treatment temperature is set to 900 ° C. or higher at which the reducing agent, for example, metallic calcium is completely dissolved and 1200 ° C. or lower at which the NdFeB alloy is not dissolved. If it is less than 900 degreeC, a reducing agent may not melt | dissolve completely, and if it exceeds 1200 degreeC, since a NdFeB alloy will melt | dissolve, it is not preferable. Preferred is 1000 to 1200 ° C. The heat treatment time varies depending on the composition of the mixture, the amount of treatment, etc., and thus cannot be defined unconditionally, but it must be maintained for 0.5 hour or longer. It is preferable to hold for about 1 to 12 hours, more preferably 1 to 8 hours, and particularly preferably 1 to 5 hours.

With this heat treatment, Nd ₂ O ₃ is reduced to Nd, and this Nd diffuses into Fe and FeB to form an NdFeB-based alloy. Further, when copper oxide powder is used as the copper-containing powder, it is reduced to Cu, and when aluminum oxide powder is used as the aluminum-containing powder, it is reduced to Al.
Patent Document 6 describes that the presence of Cu is acceptable as an inevitable impurity in industrial production. Although there is no description about the specific location of Cu here, if Cu is taken into the main phase of the NdFeB-based alloy, the magnetic properties will deteriorate. In the present invention, it is confirmed that Cu is not taken into the main phase of the NdFeB alloy and exists at the grain boundary.

4). Wet treatment After the reduction diffusion reaction is completed, the obtained reaction product is subjected to a wet treatment. In this wet treatment, the reaction product is collapsed by introducing the reaction product into water.

  A case where metallic calcium is used as the reducing agent and anhydrous calcium chloride is used as the flux will be described as an example. The reaction product contains generated alloy particles and unreacted metallic calcium, calcium chloride, and by-produced calcium oxide. Therefore, when the reaction product is put into water, the reaction product collapses into a slurry by the generation of hydrogen due to the reaction between calcium and water and the action of readily soluble calcium chloride. Since the upper part of the slurry is a suspension mainly composed of calcium hydroxide, most of the slurry can be removed by repeating the decantation.

After this wet treatment, cleaning with dilute acid (acid cleaning) is performed as necessary to remove trace amounts of remaining hydroxide and oxide formed on the surface of the alloy powder, and then if necessary After substituting with an organic solvent such as alcohol, vacuum drying is performed to obtain an alloy powder. Examples of the dilute acid include acetic acid and the like. However, if the concentration is high or the usage time is long, not only calcium oxide but also Nd is dissolved. In the final cleaning, it is desirable to repeat decantation until the conductivity of the supernatant liquid is less than 0.1 mS / cm with pure water.
Finally, it is dried to remove water from the alloy powder. The drying means may be natural drying or vacuum drying. Although it may be room temperature, it can be heated to 30 to 100 ° C. if necessary. Moreover, it can process with grinding | pulverization apparatuses, such as a medium stirring mill, as needed.

5. Cu containing _Nd 2 _{Fe 14} B alloy powder obtained by the method for producing a Cu-containing _Nd 2 _{Fe 14} B alloy powder present invention, Cu is not present in the main phase _Nd 2 _{Fe 14} in B particles, between the main phase with Nd It exists at the grain boundary and has a structure with high coercive force.

1 to 4, it can be seen from the photographs of FIGS. 2 and 4 that Cu has entered the grain boundary of the main phase Nd ₂ Fe ₁₄ B particles together with Nd. Thus, it has not been confirmed so far in Cu-containing Nd ₂ Fe ₁₄ B alloy powders by the reduction diffusion method that Cu exists at the grain boundaries and does not dissolve in the main phase Nd ₂ Fe ₁₄ B particles. The thickness (width) of the grain boundary is determined by the amount of Nd. However, if the proportion of the Nd-rich phase is too large, the magnetic properties are deteriorated, which is not preferable.
Further, preferably includes Cu-containing _Nd 2 _{Fe 14} B alloy powder further Al, referring to FIGS. 5-9, the photograph of FIG. 9, Al is scattered throughout the main phase _Nd 2 _{Fe 14} B particles I understand that.
This Cu-containing Nd ₂ Fe ₁₄ B alloy powder has an average particle diameter of 1 to 150 μm and can be used as a raw material for alloy powders by the HDDR method.

  Examples of the present invention will be specifically described below together with comparative examples. However, the present invention is not limited to the following examples.

(Example 1)
Iron powder with a purity of 99% by weight, in which 4.34 g of neodymium oxide powder having an average particle size of 5.1 μm and purity of 99.9% by weight, 0.068 g of copper oxide powder and 94% of the powder having a particle size of 10 to 70 μm account for 94% of the total. 7.07 g and 0.78 g of ferroboron powder having a B content of 19.1% by weight, which is 99.8% of the total of −330 mesh, were mixed in an automatic crusher for 10 minutes. Tyler mesh) 1.81 g of the following metallic metal calcium having a purity of 99% by weight was added and mixed. The amount of the copper oxide powder was 0.5% by weight in terms of Cu with respect to the target alloy powder.
The obtained mixture was put in an iron crucible and reduced in pressure with a rotary pump for 5 minutes. Then, Ar gas was supplied to restore the pressure to atmospheric pressure, and the temperature was raised to 1050 ° C. in an Ar gas stream over about 3 hours. The temperature was maintained for 5 hours and then cooled to room temperature.
The reaction product was taken out from the reaction vessel, poured into pure water, stirred for 30 minutes and disintegrated in water. In order to remove residual metallic calcium, CaO and Ca (OH) ₂ contained in the reaction product, washing by decantation was repeated until the pH reached 7-8. Next, after washing with 2N acetic acid for 15 minutes, washing with decantation was repeated with pure water until the conductivity of the supernatant reached 0.1 mS / cm. Thereafter, the supernatant was removed and replaced with AP-2 (modified alcohol), followed by vacuum drying to obtain alloy powder a.
The obtained alloy powder a had an average particle size of 11.7 μm, and as a result of powder X-ray analysis, the main phase was Nd ₂ Fe ₁₄ B. Further, as a result of analyzing the cross-sectional structure by a reflected electron image, as shown in FIGS. 1 to 4, Cu is present at the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and Nd ₂ Fe ₁₄ B It was confirmed that no solid solution was found in the particles.

(Example 2)
In Example 1, an alloy powder b according to Example 2 was obtained in the same manner as in Example 1 except that the reaction temperature during reduction diffusion was 1025 ° C. and the holding time was 4 hours.
As a result of powder X-ray analysis, the main phase of the obtained alloy powder b was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 3)
In Example 1, an alloy powder c according to Example 3 was obtained in the same manner as in Example 1 except that the holding time during reduction diffusion was 3 hours.
As a result of the powder X-ray analysis, the main phase of the obtained alloy powder c was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

Example 4
In Example 1, an alloy powder d according to Example 4 was obtained in the same manner as in Example 1 except that 0.054 g of copper was used instead of copper oxide and 1.78 g of granular metal calcium was used. The amount of the copper powder is 0.5% by weight in terms of Cu with respect to the target alloy powder.
As a result of the powder X-ray analysis, the main phase of the obtained alloy powder d was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 5)
In Example 1, an alloy powder e according to Example 5 was obtained in the same manner as in Example 1, except that 0.077 g of copper oxide powder was used. The amount of the copper oxide powder is 0.6% by weight in terms of Cu with respect to the target alloy powder.
As a result of powder X-ray analysis, the obtained alloy powder e was Nd ₂ Fe ₁₄ B as a main phase. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 6)
In Example 1, an alloy powder f according to Example 6 was obtained in the same manner as in Example 1 except that 4.21 g of neodymium oxide powder and 1.76 g of granular metal calcium were used.
As a result of powder X-ray analysis, the obtained alloy powder f had a main phase of Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 7)
In Example 1, an alloy powder g according to Example 7 was obtained in the same manner as in Example 1 except that 0.13 g of calcium chloride was further added.
As a result of powder X-ray analysis, the main phase of the obtained alloy powder g was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 8)
In Example 1, an alloy powder h according to Example 8 was obtained in the same manner as in Example 1 except that 0.20 g of calcium chloride was further added.
As a result of powder X-ray analysis, the main phase of the obtained alloy powder h was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

Example 9
In Example 1, an alloy powder i according to Example 9 was obtained in the same manner as in Example 1 except that the amount of the copper oxide powder was added so as to be 0.007% by weight in terms of Cu.
As a result of powder X-ray analysis, the obtained alloy powder i had a main phase of Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 10)
In Example 1, an alloy powder j according to Example 10 was obtained in the same manner as in Example 1 except that the amount of the copper oxide powder was added so as to be 0.05% by weight in terms of Cu.
As a result of powder X-ray analysis, the obtained alloy powder j had a main phase of Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Example 11)
In Example 1, an alloy powder k according to Example 11 was obtained in the same manner as in Example 1 except that the amount of the copper oxide powder was added so as to be 1.0% by weight in terms of Cu.
As a result of the powder X-ray analysis, the main phase of the obtained alloy powder k was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

Example 12
In Example 1, except that 0.103 g of aluminum oxide powder (0.6% by weight in terms of Al with respect to the target alloy powder) was added, the alloy powder l according to Example 12 was the same as Example 1. Got.
As a result of powder X-ray analysis, the obtained alloy powder l was Nd ₂ Fe ₁₄ B as a main phase. Further, as a result of analyzing the cross-sectional structure by a reflected electron image, as shown in FIG. 8, Cu is present at the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and the inside of the Nd ₂ Fe ₁₄ B particles It was confirmed that it was not dissolved. On the other hand, as shown in FIG. 9, it was confirmed that Al was scattered throughout the particles.

(Example 13)
In Example 12, an alloy powder m according to Example 13 was obtained in the same manner as in Example 1 except that 0.22 g of anhydrous calcium chloride was further added.
As a result of powder X-ray analysis, the main phase of the obtained alloy powder m was Nd ₂ Fe ₁₄ B. Moreover, as a result of analyzing the cross-sectional structure by the reflected electron image, Cu exists in the grain boundary between the main phase Nd ₂ Fe ₁₄ B particles together with Nd, and is dissolved in the Nd ₂ Fe ₁₄ B particles. Not confirmed.

(Comparative Example 1)
In Example 1, an alloy powder n according to Comparative Example 1 was obtained in the same manner as in Example 1 except that the reaction temperature during reduction diffusion was 850 ° C.
As a result of powder X-ray analysis, the obtained alloy powder n was found to have peaks derived from Fe and Nd ₂ O ₃ in addition to Nd ₂ Fe ₁₄ B. Did not do.

(Comparative Example 2)
In Example 1, an alloy powder o according to Comparative Example 2 was obtained in the same manner as in Example 1 except that the holding time during reduction diffusion was 10 minutes.
As a result of the powder X-ray analysis, the obtained alloy powder o showed peaks derived from Fe and Nd ₂ O ₃ in addition to Nd ₂ Fe ₁₄ B. Did not do.

The results of Examples 1 to 13 and Comparative Examples 1 and 2 are collectively shown in Table 1.
As is apparent from Table 1, in the Cu-containing rare earth-iron-boron alloy powders (Examples 1 to 13) produced by the method for producing a Cu-containing rare earth-iron-boron alloy powder according to the present invention, Cu And Nd were present at the grain boundaries between the main phase Nd ₂ Fe ₁₄ B particles, and Al was confirmed to be scattered throughout the particles.
On the other hand, in Comparative Examples 1 and 2 in which the production conditions deviate from the present invention, as a result of powder X-ray analysis, peaks derived from raw material Fe and Nd ₂ O ₃ are recognized and it is clear that the reduction diffusion is insufficient.

  The Cu-containing R—Fe—B permanent magnet obtained by the present invention has high saturation magnetization among rare earth magnets, so it is used for consumer electronic devices, computer peripherals, MRI, and industrial motors and automobile motors. it can. In particular, since Cu is contained in the grain boundaries of the alloy particles, the magnetic properties can be improved.

Claims (8)

A rare earth oxide powder or rare earth oxide powder and rare earth metal powder, and a raw material powder comprising iron-containing powder and boron-containing powder are mixed with a reducing agent in an amount sufficient to reduce the oxide powder, and Cu is reduced by a reduction diffusion method. A method for producing a rare earth-iron-boron alloy powder containing:
The rare earth oxide powder and the rare earth metal powder contain at least Nd as a rare earth element, do not contain Dy, and contain one or more elements.
As a raw material powder, copper-containing powder is further mixed, and the copper-containing powder is mixed so that the composition range is 0.003 to 1.5% by weight in terms of Cu,
Heat-treating the mixture under an inert gas atmosphere at a temperature of 900 ° C. to 1200 ° C. for 0.5 hours or more, and wet-treating the resulting reaction product mixture, followed by drying,
In the rare earth-iron-boron alloy powder, Cu derived from the copper-containing powder does not exist in the main phase particles containing at least a part of Nd, and exists in the grain boundary between the main phases together with the rest of Nd. about,
A process for producing a Cu-containing rare earth-iron-boron alloy powder characterized by   The method for producing a Cu-containing rare earth-iron-boron alloy powder according to claim 1, wherein an aluminum-containing powder is further added as the raw material powder.   The Cu-containing rare earth-iron-boron alloy powder according to claim 2, wherein the aluminum-containing powder is mixed so that the composition range is 0.003 to 1.5 wt% in terms of Al. Production method.   The method for producing a Cu-containing rare earth-iron-boron alloy powder according to any one of claims 1 to 3, wherein the heat treatment is held for 1 to 5 hours.   The Cu-containing rare earth-iron-boron according to any one of claims 1 to 4, wherein at least one flux selected from alkali metal chlorides and alkaline earth metal chlorides is used together with the reducing agent. Method for producing an alloy powder. A Cu-containing rare earth-iron-boron alloy powder containing Nd ₂ Fe ₁₄ B particles as a main phase and not containing Dy,
Cu-containing rare earth-iron-boron based alloy powder characterized in that Cu is not present in the main phase Nd ₂ Fe ₁₄ B particles but is present at the grain boundary between the main phases together with Nd.   The Cu-containing rare earth-iron-boron alloy powder according to claim 6, having an average particle size of 1 to 150 µm. The Cu-containing rare earth-iron-boron alloy powder according to claim 6 or 7, further comprising Al dispersed throughout the main phase Nd ₂ Fe ₁₄ B particles.