JP5609783B2 - Method for producing rare earth-transition metal alloy powder - Google Patents

Description

  The present invention relates to a method for producing a rare earth-transition metal alloy powder capable of improving the squareness of the demagnetization curve of the rare earth-transition metal alloy powder obtained by the reduction diffusion method and enhancing the permanent magnet performance. .

Various electric appliances in recent years, for example, most home electric appliances such as mobile phones, digital cameras, and digital videos, are required to be smaller, lighter, and have higher performance, and the demand is increasing. In order to achieve such a reduction in size and weight, one of the important issues is to reduce the size and improve the characteristics of the permanent magnets used in the home appliances. Furthermore, in the above-mentioned home appliances, the cost competition is intensifying, and as a matter required for the permanent magnets to be used, further price (low price) is added to weight reduction and high performance. .
As a permanent magnet material, a ferrite magnet that has been conventionally used is the most advantageous in terms of price, but the maximum energy product (BH) _max is as low as 15 to 20 kJ · m ⁻³ (several MGOe), and the weight is reduced. The demand for higher performance has not been fully met. In terms of characteristics, rare earth magnets having a magnetic property several tens of times greater than that of low-character magnets such as ferrite magnets are known. The rare earth magnets are also gaining importance based on the above background, and in 1993, the magnets were the most used by removing the ferrite magnets. Among these, the Nd—Fe—B based sintered magnet has a maximum energy product (BH) _max exceeding 440 kJ · m ⁻³ (55 MGOe), and is most in demand among rare earth magnets.

However, Nd-Fe-B sintered magnets need to have finer crystal grains to be used for high-performance bonded magnets, and are roughly pulverized with a stamp mill and further pulverized with a vibration ball mill. It has been broken. In addition, a technique known as HDDR method (Hydrogenation-Decomposition-Desorption-Recombination) for refining crystal grains by utilizing hydrogen absorption / release reaction to rare earth-transition metal alloys is known. For example, as a rare earth-transition metal alloy, by applying the HDDR method to an Nd ₂ Fe ₁₄ B intermetallic compound produced by a melt casting method, a high-performance bonded magnet powder having a fine recrystallized structure is obtained. (For example, Non-Patent Document 1, Patent Documents 1 and 2).

To illustrate a specific powder production method, in Example 1 of Patent Document 1, first, the average crystal grain size of the Nd ₂ Fe ₁₄ B phase mainly composed of Nd ₁₅ Fe ₇₇ B ₈ melted and cast in a high-frequency melting furnace. Is roughly pulverized with a stamp mill, and a fine powder with an average of 3.7 μm is produced with a vibration ball mill to form a raw material alloy. This fine powder was put into a heat treatment furnace, heated to 850 ° C. while flowing 1 atm of hydrogen gas, and when the temperature reached 850 ° C., it was evacuated for 30 minutes while maintaining this temperature. A vacuum of 0 × 10 ⁻⁵ Torr is set, and the inside of the furnace is purged with argon gas, and then rapidly cooled and recovered. The powder having an average particle size of 5.6 μm thus obtained is said to have a very high coercive force of 11.5 kOe.

Further, in Example 1 of Patent Document 2, an alloy ingot having a composition of Nd _12.1 Fe _60.6 Co _20.0 B _5.7 Ba _1.6 melt-cast in a plasma arc furnace in an argon gas atmosphere 1100 Homogenized heat treatment at ° C for 20 hours, mechanically pulverized to 35 to 40 mm in an argon gas atmosphere, placed in a hydrogen gas atmosphere furnace pressurized to 1.3 kgf / cm ² and held at 250 ° C for 1 hour Hydrogen is occluded and then dehydrogenated to a vacuum atmosphere of 0.5 Torr to obtain a coarse particle aggregate is used as a raw material alloy. The alloy was heated to 800 ° C. in a hydrogen atmosphere, held at a pressure of 1.3 kgf / cm ² for 5 hours, and then at a vacuum atmosphere of 1.0 × 10 ⁻⁵ Torr over 1 hour at 800 ° C. Then, dehydrogenation treatment is performed, and thereafter, it is rapidly cooled to room temperature with 1.2 kgf / cm ² of argon gas over 10 minutes. The recovered powder aggregate is pulverized to have an average particle size of 74 to 105 μm, and has a maximum energy product of 34 MGOe.
In such a process, it is necessary to reduce the surface oxide layer of the raw material alloy as much as possible. When the powder surface is oxidized, the degree of decomposition and disproportionation of the metal structure varies due to the absorption of hydrogen, the crystal grain size of the recrystallized structure obtained after the hydrogen release reaction varies, and the squareness of the demagnetization curve is It is because it falls.

By the way, as a method for producing a rare earth-transition metal alloy, apart from the above-described process of melting and casting, at least a mixture of rare earth oxide powder and transition metal powder is selected from alkali metals, alkaline earth metals and hydrides thereof. There is known a reduction diffusion method in which one kind is added as a reducing agent for a rare earth oxide and heated to 850 to 1200 ° C. (for example, Patent Document 3).
A typical reducing agent is metallic Ca. Metal Ca melts at 834 ° C. to reduce the surrounding rare earth oxide, and the reduced rare earth metal diffuses from the surface of the transition metal powder to form an intermetallic compound. Although the formed intermetallic compound is influenced by the heat treatment conditions, the particles are approximately the size of a transition metal powder. At this time, calcium oxide is by-produced with the reduction of the rare earth oxide, and the reaction product is a porous sintered body composed of rare earth-transition metal alloy particles and calcium oxide particles. When this is put into water, the calcium oxide is disintegrated as calcium hydroxide and becomes a slurry of rare earth-transition metal alloy powder. When the slurry is stirred and allowed to stand, the alloy powder having a large specific gravity quickly settles and the calcium hydroxide floats in the supernatant. The target rare earth-transition metal alloy is produced as a powder by performing a wet treatment to remove the supernatant calcium hydroxide by repeated decantation and then drying. The melt casting method requires mechanical pulverization to pulverize the alloy, while the reduction diffusion method provides a powder with a uniform particle size, which is a low-cost and energy-saving process. It is.

The alloy production by the reduction diffusion method is completed by removing the calcium component by wet-treating the reaction product obtained by the heat treatment as described above and drying it. In other words, the reduction diffusion method is a method for producing a powdered rare earth-transition metal alloy in which heat treatment and wet treatment are one set. Patent Documents 4 and 5 are examples of applying the HDDR method to the raw material alloy powder produced by the reduction diffusion method.
Patent Document 5 discloses at least one rare earth oxide powder having an average particle size of 1 μm to 10 μm, at least one B powder and / or B alloy powder having an average particle size of 1 μm to 150 μm, and Fe powder having an average particle size of 200 μm to 400 μm. Are mixed and mixed so as to have a magnet composition mainly composed of R12 at% to 20 at%, B4 at% to 20 at%, Fe65 at% to 81 at%, and then magnet powder is obtained by a Ca reduction diffusion method. The main component is a single particle having a specific crystal orientation of 200 μm to 400 μm with a R ₂ Fe ₁₄ B phase as the main phase, and the remainder is a specific crystal orientation with a particle size of 250 μm to 500 μm A method for producing a raw material powder for anisotropic bonded magnets for obtaining a powder composed of agglomerated single particles having a particle is described. As a result, the material for anisotropic bonded magnets has few agglomerated particles, does not need to be pulverized, is hardly oxidized, has good formability in the bonded magnetizing process, can be densified, and has high magnetic properties. A powder can be obtained.

In addition, the present applicant weighs and mixes rare earth oxide powder, transition metal powder, and other raw material powders, and further adds and mixes a reducing agent sufficient to reduce the rare earth oxide powder. After heating and reducing the rare earth oxide to a rare earth metal by firing at a temperature not lower than the temperature at which the reducing agent melts in an atmosphere in which oxygen is substantially absent and not melting the desired alloy, Is diffused into the transition metal powder to obtain a desired alloy, and the fired product obtained after cooling to room temperature is poured into water to dissolve the residual reducing agent and the generated redox agent, and stirring and decantation are repeated. In the method of producing the alloy powder containing the desired rare earth and transition metal by separating and recovering the precipitated alloy powder and drying, the fired product is hydrotreated after the firing. Rare earth and symptoms was proposed a manufacturing method by reduction diffusion method of the alloy powder containing a transition metal (Patent Document 6).
Thereby, the pulverization step is omitted by improving the disintegration property of the fired product in water, thereby improving the yield of the product and obtaining a high quality alloy product.
However, according to the study by the present inventor, the alloy powder produced by the method proposed in these known documents has a problem that it is difficult to increase the squareness Hk of the demagnetization curve.

Therefore, the present applicant has excellent oxidation resistance and high magnetic properties by nitriding a mother alloy powder obtained by a reduction diffusion method from a rare earth oxide powder and a transition metal powder containing iron and manganese as essential components. In order to produce a rare earth-iron-manganese-nitrogen based magnet powder, a rare earth-iron-manganese-nitrogen based magnet powder formed after nitriding has a crystal distortion (integral width) of the pulverized magnet powder of 0.09 deg. . It has been proposed that the powder is crushed to a degree sufficient to make it below, and subsequently classified so that the magnet powder having a particle size of less than 20 μm is made 17% by weight or less (Patent Document 7).
As a result, it has become possible to obtain rare earth-iron-manganese-nitrogen based magnet powders that exhibit excellent oxidation resistance and high magnetic properties, in particular, have a large demagnetization curve squareness and a high residual magnetic flux density. . However, the squareness is still 200 to 300 kA / m, which is not sufficient.

JP-A-01-132106 Japanese Patent Laid-Open No. 08-176617 Japanese Examined Patent Publication No. 03-062764 Japanese Patent Laid-Open No. 02-004901 Japanese Patent Laid-Open No. 07-130517 JP 09-241708 A JP 2006-60049 A

T. T. et al. Takeshita and R.K. Nakayama: Proc. 10th Int'l Workshop on RE Magnet and Ther Applications, Vol. I, p. 551, Kyoto, Japan (1989).

  In view of the background art described above, an object of the present invention is to improve the squareness of the demagnetization curve of the rare earth-transition metal alloy powder obtained by the reduction diffusion method, and improve the permanent magnet performance. The object is to provide a method for producing an alloy powder.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have made hydrogen gas before wet treatment of a reaction product containing a rare earth-transition metal alloy obtained after heat treatment of the reduction diffusion method. And then heat-treating under specific conditions (HDDR), further heat-treating under specific conditions in a vacuum or dilute hydrogen gas atmosphere, then wet-treating with water and then drying under specific conditions, It has been found that the squareness of the demagnetization curve of the transition metal alloy powder can be improved, and the present invention has been completed.

  That is, according to the first invention of the present invention, from rare earth oxide powder, transition metal powder and / or oxide powder thereof, granular or powdery alkali metal, alkaline earth metal and hydrides thereof. A reaction product mixture containing a rare earth-transition metal alloy is obtained by mixing at least one selected reducing agent and holding the mixture in an inert atmosphere at a temperature of 850 to 1200 ° C. for 1 to 10 hours. Step 1, after cooling the reaction product mixture to 300 ° C. or lower, hydrogen gas is introduced, and maintained at 700 to 900 ° C. for 1 to 20 hours in an atmosphere having a hydrogen gas partial pressure of 20 to 40 kPa. A third step of heat-treating the reaction product mixture obtained in the second step in a vacuum or an atmosphere of hydrogen gas partial pressure of less than 10 kPa at 500 to 900 ° C. for 10 minutes to 20 hours, A fourth step of washing the heat-treated product with water to remove the by-product containing the reducing agent and recovering the rare earth-transition metal alloy, and removing the washed rare earth-transition metal alloy at 150 to 400 ° C. And a fifth step of drying in an oxidizing atmosphere. A method for producing a rare earth-transition metal alloy powder is provided.

According to the second invention of the present invention, in the first invention, the average particle size of the transition metal powder and / or its oxide powder used in the first step is 50 μm or less. A method for producing a rare earth-transition metal alloy powder is provided.

Since the rare earth-transition metal alloy powder obtained by the present invention employs the reduction diffusion method, raw material costs can be reduced, and the reaction product is subjected to hydrogen treatment and drying treatment after wet treatment under specific conditions. Thus, the squareness which has been a problem in the prior art can be improved. In addition, according to this method, the amount of water used in hydrogen or wet processing can be reduced, so that the feature of energy saving can be utilized, and its industrial value is extremely large.

Hereinafter, the method for producing the rare earth-transition metal alloy powder of the present invention will be described in detail.

1. Method for Producing Rare Earth-Transition Metal Alloy Powder The method for producing the rare earth-transition metal alloy powder of the present invention includes (1) rare earth oxide powder, transition metal powder and / or oxide powder thereof, and granular or powdery form. And at least one reducing agent selected from alkali metals, alkaline earth metals and hydrides thereof, and the mixture is maintained in an inert atmosphere at 850 to 1200 ° C. for 1 to 10 hours to form a rare earth. -A first step of obtaining a reaction product mixture containing a transition metal alloy, (2) after cooling the reaction product mixture to 300 ° C or lower, introducing hydrogen gas, and in an atmosphere of hydrogen gas partial pressure of 20 to 40 kPa 2nd process hold | maintained for 1 to 20 hours at the temperature of 700-900 degreeC, (3) 500-900 degree in the atmosphere of less than 10 kPa of the reaction product mixture obtained by vacuum or hydrogen gas A third step of heat-treating for 10 minutes to 20 hours at C; (4) a fourth step of washing the obtained heat-treated product with water to remove a by-product containing a reducing agent and recovering a rare earth-transition metal alloy; And (5) a fifth step of drying the washed rare earth-transition metal alloy in a non-oxidizing atmosphere at 150 to 400 ° C.

(1) First step (production of reaction product mixture)
In the present invention, a rare earth oxide powder, a transition metal powder, and a reducing agent for reducing the rare earth oxide are mixed, and then the mixture is heated and fired in an inert atmosphere to obtain a rare earth-transition metal alloy. A reduction diffusion method is used to obtain a reaction product mixture.

(Rare earth oxide)
The rare earth oxide is an oxide of a rare earth element, that is, an element of at least one element selected from the group of, for example, Y, La, Ce, Pr, Nd, and Sm.
Among the rare earth elements, Nd and Sm, particularly Nd are preferable, and a material having a high coercive force can be obtained when Nd contains 50 atomic% or more of the rare earth elements.
The rare earth oxide powder is preferably added in an amount of about 5 to 30% by mass more than the target composition. This is because when the amount of rare earth elements is small, more of the rare earth elements are dissolved during wet processing to remove the reducing agent, so the amount of rare earth elements is below the target composition and the rare earth is insufficient and a soft magnetic phase appears. This is because the coercive force is lowered. On the other hand, if the rare earth component is more than the above range, the nonmagnetic phase increases and the magnetization decreases, which is not preferable.

(Transition metal powder)
The transition metal powder can be mixed with iron-containing powders such as iron oxide powder, cobalt powder, and nickel powder, with iron metal powder being essential. As the iron powder, for example, reduced iron powder, gas atomized powder, water atomized powder, electrolytic iron powder, and the like can be used, and classification is performed so as to obtain an optimum particle size as necessary.
Here, up to 30% by mass of the transition metal powder can be added as iron oxide powder to adjust the calorific value of the reduction diffusion reaction.
In addition, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn are used to improve physical properties such as magnetic properties, temperature properties, and corrosion resistance of the finally obtained rare earth-transition metal alloy powder. , Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Re, Pt, Au, B, C, Al, Si, P, and S may be added. it can. In this case, these additive elements are mixed with the raw material powder composed of rare earth oxide powder and transition metal powder in the form of its simple substance powder, oxide powder, alloy powder with other constituent elements, composite oxide powder, etc. The

(Reducing agent)
As the reducing agent, an alkali metal or alkaline earth metal having a function of reducing a rare earth oxide and a hydride thereof are used. For example, Li and / or Ca, or at least one selected from these elements and Na, K, Mg, Sr or Ba can be used. Easy to handle is granular metallic calcium. The particle size is preferably about 1 to 5 mm.
These reducing agents are desirably used with carefully controlled amounts and powder properties, powder properties of rare earth oxides, mixed state of various raw material powders, and temperature and time of the reduction diffusion reaction. Among the reducing agents, metal Li or Ca is preferable, and Ca is particularly preferable from the viewpoints of handling safety and cost.

It is preferable that the amount of the reducing agent added is slightly more than the reaction equivalent so that the rare earth oxide can be reduced. If the reducing agent is not made more than the equivalent amount, the reducing agent is oxidized by residual oxygen and moisture in the container, and the rare earth oxide cannot be sufficiently reduced, resulting in a decrease in the magnet powder characteristics.
The mixing method may be either a dry method or a wet method, but use of a wet ball mill or the like is desirable in terms of uniformity. In wet mixing, care must be taken so that separation due to a difference in specific gravity does not occur during subsequent handling such as drying. In the case of wet mixing, the alkali metal, alkaline earth metal, and hydride thereof as a reducing agent are finally mixed in a dry manner.
When the above mixture is transferred to a reaction vessel for reducing diffusion, the rare earth oxide and the like are fine particles with an average particle diameter of several μm and the powder is likely to be scattered, and it is preferable to attach a cover or the like to prevent the scattering. . By this operation, it is possible to suppress the composition deviation in the alloy powder. After that, it is preferable that the reaction vessel charged with the above mixture is put into a reduction diffusion furnace to make a non-oxidizing atmosphere substantially free of oxygen.

In the first step, a rare earth oxide powder and a transition metal powder or a mixed raw material containing the oxide powder is mixed with metal Ca as a reducing agent and heat-treated.
The mixture is heated in an inert atmosphere such as argon gas. At this time, it is desirable to depressurize the inside of the furnace for replacement. The heating temperature is set to 850 to 1200 ° C., taking into consideration the particle size of the raw material, and the time for which the rare earth metal produced by reduction is sufficiently diffused into the transition metal raw material powder is maintained. When the heating temperature is less than 850 ° C., rare earth element non-diffusion parts are likely to be formed in the rare earth-transition metal alloy particles produced by non-uniform reduction reaction and diffusion reaction. When the temperature exceeds 1200 ° C., the rare earth-transition metal alloy particles in the reaction product are sintered with each other, and even if wet-treated in the fourth step, the disintegration is poor and powdering is difficult. The heating time is 1 to 10 hours, preferably 4 to 8 hours.

  The particle size of the rare earth-transition metal alloy particles formed by the heat treatment of the reduction diffusion method is greatly affected by the particle size of the transition metal powder as a raw material, although it depends on the heat treatment conditions. In the present invention, the average particle size of the transition metal powder raw material is 100 μm or less, desirably 50 μm or less, and more desirably 30 μm or less. When the average particle size exceeds 100 μm, it takes time for the rare earth metal reduced by Ca to diffuse to the center of the transition metal particles, and an undiffused portion is generated, which deteriorates the magnetic properties of the alloy powder. When the average particle size is 50 μm or less, further 30 μm or less, the squareness of the finally obtained alloy powder is further improved. This is because, in the heat treatment containing hydrogen in the second step, the smaller the rare earth-transition metal alloy particles, the harder the cracks are caused when the alloy particles absorb hydrogen and the lattice constant of the compound increases. Presumed to be. For the other raw material powders, it is desirable to make the average particle size 10 μm or less in order to improve the uniformity of the raw materials after mixing, especially 5 μm or less, and more desirably 1 μm or less, for the raw material powder that is a trace additive element. It is desirable to mix.

(2) Second step (HDDR processing)
When the heat treatment in the first step is completed, the reaction product is cooled to 300 ° C. or lower in the furnace, and an atmosphere gas containing hydrogen is introduced.

  The surface of the rare earth-transition metal alloy particles in the reaction product obtained in the first step is extremely active, and the reaction product should not be exposed to the atmosphere as much as possible in order to maintain its activity. desirable. The cooling temperature is preferably 200 ° C. or lower, and more preferably 100 ° C. or lower. When the temperature exceeds 300 ° C, the introduction of the atmospheric gas containing hydrogen causes the rare earth-transition metal alloy particles in the reaction product to react rapidly with hydrogen while generating heat, and the squareness of the finally obtained alloy powder is reduced. descend. When an atmospheric gas containing hydrogen is introduced at 100 ° C. or lower, the alloy particles gradually absorb hydrogen, and the lattice constant of the intermetallic compound increases. As the lattice constant increases, cracks occur in the rare earth-transition metal alloy particles, but when the average particle size of the transition metal powder raw material is selected to be 50 μm or less, further 30 μm or less in the first step The strain due to the increase in lattice constant is relieved and cracks are difficult to enter.

  After hydrogen absorption is stabilized, the temperature is raised to 700 to 900 ° C. and held as the second step. As a result, the rare earth-transition metal alloy is decomposed into a rare earth hydride phase and a transition metal rich phase. In the case of an Nd2Fe14B alloy, it decomposes into a neodymium hydride phase, an α iron phase, and a ferroboron phase. When the temperature is lower than 700 ° C, the decomposition does not proceed. When the temperature exceeds 900 ° C, the size of the decomposed tissue varies. Either of these reduces the squareness of the final alloy powder. The atmosphere gas at the time of temperature rising and holding is desirably a mixed gas with an inert gas such as argon or helium gas, and this mixed gas is circulated in the furnace so that the hydrogen partial pressure is 20 to 40 kPa. The hydrogen partial pressure is preferably 30 to 40 kPa. If it is less than 20 kPa, decomposition does not proceed, and if it exceeds 40 kPa, the size of the decomposed tissue varies. The holding time is appropriately selected depending on the progress of tissue degradation, but is selected between 1 hour and 20 hours. The holding time is preferably 1 to 15 hours, and more preferably 1 to 10 hours.

  By the way, Patent Document 6 discloses a technique for producing an Sm—Co-based or Nd—Fe—B-based alloy powder by treating a fired product of the reduction diffusion method with hydrogen, washing it into water, and drying it. Is disclosed. However, the purpose of the hydrogen treatment in Patent Document 6 is to improve the yield by washing, and the temperature range of the hydrogen treatment is also set to 100 to 600 ° C. Since it is described that the target alloy compound is decomposed or a by-product is formed when the temperature exceeds 600 ° C., it is suggested that the temperature of 700 to 900 ° C. of the present invention is inappropriate. This is due to technical thought.

(3) Third manufacturing process (heat treatment)
The rare earth-transition metal alloy particles having the decomposed metal structure obtained in the second step are heat-treated at 500 to 900 ° C. in an atmosphere of vacuum or hydrogen gas partial pressure of less than 10 kPa. Thereby, the decomposed | disassembled structure | tissue recombines and the original intermetallic compound phase is formed, The crystal grain diameter will be less than 500 nm.

Here, when the hydrogen gas partial pressure is 10 kPa or more or the temperature is less than 500 ° C., the recombined metal structure is not sufficiently formed, and the squareness of the alloy powder is not improved. On the other hand, if it exceeds 900 ° C, the crystal grain size of the recombination structure becomes coarse, and the coercive force and the squareness are not improved. Therefore, it is preferable to perform heat treatment at a hydrogen gas partial pressure of 100 Pa or less and 600 to 900 ° C., and more preferably a heat treatment at a hydrogen gas partial pressure of 80 Pa or less and 700 to 900 ° C.
The heat treatment holding time is appropriately selected depending on the recombination structure formation state, but is selected between 10 minutes and 20 hours. The holding time is preferably 30 minutes to 10 hours, and more preferably 30 minutes to 5 hours. Then, it cools to room temperature, maintaining the atmosphere, and throws into a 4th process.

(4) Fourth manufacturing process (wet process)
In the fourth step, the cooled reaction product is poured into water, the Ca component used as a reducing agent is removed while repeating decantation, and rare earth-transition metal alloy particles are recovered. The reaction product after cooling in the third step has collapsed from several millimeters to several tens of millimeters, and when it is put into water, it quickly becomes a slurry. Stirring, standing, and removal of the supernatant are repeated to remove the Ca component. Further, a dilute aqueous solution such as hydrochloric acid or acetic acid may be added to remove the Ca component. The washed alloy powder is recovered by filtration, water is replaced with alcohol, and the alloy powder is dried in the next fifth step.

(5) Fifth manufacturing process (drying process)
In the fifth step, the recovered alloy powder is dried in a non-oxidizing atmosphere at 150 to 400 ° C. In this step, it is necessary to remove moisture and hydrogen diffused in the surface layer of the alloy powder in the fourth step to make it 0.20% by weight or less.

  Here, if the drying temperature is less than 150 ° C., the removal of hydrogen is incomplete and cannot be reduced to 0.20% by weight or less. If the drying temperature exceeds 400 ° C., the alloy powder is oxidized even in a non-oxidizing atmosphere. Sex is reduced. The drying time is set so that the amount of impurity hydrogen in the alloy powder is 0.20% by weight or less as the time required for moisture and hydrogen removal depending on the processing amount of the powder, whether it is stationary drying or stirring drying. Is done. When cracks are formed on the surface of the alloy powder by the second step, the moisture and hydrogen that have entered the cracks are sufficiently removed, and the amount of impurity hydrogen in the alloy powder is 0.20% by weight or less. It is necessary to adjust the temperature and time. If the amount of impurity hydrogen remaining in the alloy powder exceeds 0.20% by weight, the squareness deteriorates. The drying temperature is preferably 200 to 300 ° C., and more preferably pre-dried under a vacuum of 50 to 100 ° C. before drying in a non-oxidizing atmosphere.

2. Rare earth-transition metal alloy powder The rare earth-transition metal alloy powder according to the present invention is obtained by the above-described manufacturing method, and has an intermetallic compound alloy containing a rare earth element and a transition metal element as a main phase. If it is, it will not be restrict | limited in particular. For example, tetragonal Nd ₂ Fe ₁₄ B alloy, Sm ₂ Co ₁₇ alloy with Th ₂ Zn ₁₇ type structure, Sm ₂ Fe ₁₇ N ₃ alloy, SmCo ₅ type alloy with CaCu ₅ type structure Applicable to various alloys such as alloys.
These alloys can contain known additive elements such as Ga and Nb in order to improve physical properties such as magnetic properties, temperature properties, and corrosion resistance. The additive element is mixed with the raw material powder composed of the rare earth oxide powder and the transition metal powder in the form of its simple powder, oxide powder, alloy powder with other constituent elements, composite oxide powder, and the like.

  Its composition is 25-35 wt% rare earth elements, 3 wt% or less Ga and Nb, 5 wt% or less B, and the balance is substantially Fe or 20 wt% or less of Fe is Co. It is preferable that the hydrogen content of Fe and Co substituted with is 0.20% by weight or less.

Rare earth according to the present invention - transition metal alloy powder has the composition described above, an average particle diameter of 5 to 50 [mu] m, has improved the loop squareness of the demagnetization curve. This is because, in the heat treatment containing hydrogen in the second step, the smaller the rare earth-transition metal alloy particles, the harder the cracks are caused when the alloy particles absorb hydrogen and the lattice constant of the compound increases. Presumed to be. In addition, the alloy powder is sufficiently dried in a non-oxidizing atmosphere of 150 to 400 ° C. in the fifth step, and it is assumed that moisture and hydrogen diffused in the alloy powder surface layer in the fourth step are removed. Is done.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited at all by these Examples. The obtained alloy powder was measured by the following method.

<Measurement of average particle size>
The average particle diameter of the alloy powder was measured using a laser diffraction particle size distribution meter (manufactured by Sympatec).
<Evaluation of magnetic properties>
Magnetic properties of the alloy powder was measured at the maximum mark pressure field 1200 kA / m vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd., VSM-3). In this measurement, a sample was prepared by applying an orientation magnetic field of 1600 kA / m according to the Bond Magnet Testing Method Guide Book BMG-2005 of Japan Bond Magnet Industry Association, and evaluation was performed after magnetizing with a magnetic field of 4000 kA / m.

[Example 1]
As a first step, 400 g of neodymium oxide powder having an average particle size of 8 μm (Nd ₂ O ₃ purity 99.5%), niobium oxide powder having an average particle size of 5 μm (Nb ₂ O ₅ purity 99.9%), 4.7 g, average particle size 5.0 g of 22 μm gallium oxide powder (Ga ₂ O ₃ purity 99.9%) was pulverized and mixed for 18 hours with a rotating ball mill using water as a solvent. The collected mixture was dried until the water content became 1% by weight or less, and 720 g of electrolytic iron powder having a particle size of 325 mesh or less, 62 g of ferroboron (B content 19.8%) having a particle size of 200 mesh or less, and metal Ca particles ( 175 g of Ca purity 99%) was added and mixed with a V blender. This mixture was inserted into a steel reaction vessel and placed in an electric furnace. After the pressure in the furnace was reduced to 5 kPa and replaced with argon gas, the temperature was raised to 1050 ° C. while circulating argon gas at 1 L / min, and 1050 Hold at 4 ° C. for 4 hours.
Then, after cooling to 28 degreeC and depressurizing the inside of a container to 10 kPa, hydrogen gas was introduce | transduced to 101 kPa, and it hold | maintained for 3 hours, maintaining the pressure. Next, as a second step, the temperature of the mixed gas of hydrogen gas and argon gas was raised to 800 ° C. and kept for 3 hours while flowing a mixed gas of hydrogen gas and argon gas so that the hydrogen partial pressure was 36 kPa.
Thereafter, as a third step, the inside of the container was replaced with argon gas while maintaining 800 ° C., and then the pressure was reduced to 50 Pa and held for 30 minutes, and then cooled to room temperature.
The reaction product mixture recovered from the reaction vessel after cooling had a state in which the sintered ingot formed in the first step collapsed to several tens of mm or less. Next, as a fourth step, this was poured into 10 L of water and almost completely disintegrated within 1 hour. While repeating the decantation, the calcium hydroxide suspension was separated from the resulting slurry, and further water injection reduced the slurry pH to 10. Further, dilute acetic acid was added dropwise to maintain the pH at 6.5 for 10 minutes, followed by filtration, dehydration and substitution with ethanol, and the alloy powder was recovered. Further, as a fifth step, the recovered alloy powder was put into a mixer dryer and maintained in a vacuum of 10 Pa at 80 ° C. for 1 hour, then the temperature was raised to 250 ° C. and maintained for 2 hours, and then cooled.
The average particle diameter of the recovered alloy powder is 28 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.21 wt%, Ca 0.01 wt%, H 0.06 wt. %, The balance was Fe. The magnetic properties of the alloy powder were a residual magnetic flux density Br of 1.27 T, a coercive force Hc of 1030 kA / m, and a squareness of Hk 430 kA / m.

[Comparative Example 1]
In Example 1, after the first step, the reaction product mixture cooled to 28 ° C. was recovered from the container and poured into 10 L of water. As in Example 1, decantation was repeated to separate the calcium hydroxide suspension, and diluted acetic acid was added dropwise to the slurry that had reached pH 10, and maintained for 10 minutes while maintaining pH 6.0, filtered, After dehydration substitution with ethanol, the mixture was put into a mixer dryer and kept at 80 ° C. in a vacuum of 10 Pa for 1 hour. The average particle diameter of the obtained alloy powder is 34 μm, and the composition is Nd 29.7 wt%, B 1.08 wt%, Ga 0.33 wt%, Nb 0.28 wt%, O 0.20 wt%, Ca 0.03 wt%, and the balance is Fe. was.
This alloy powder was put in the reaction vessel again, and the inside of the vessel was decompressed to 10 kPa. Then, hydrogen gas was introduced to 101 kPa, and the pressure was maintained for 3 hours. Next, the temperature of the mixed gas of hydrogen gas and argon gas was raised to 800 ° C. while maintaining the hydrogen partial pressure to be 36 kPa and held for 3 hours. Next, after the inside of the container was replaced with argon gas while maintaining 800 ° C., the pressure was reduced to 5 kPa and held for 30 minutes, and the pressure was further reduced to 10 Pa and then cooled to room temperature. The magnetic properties of the powder recovered after cooling were Br1.23T, Hc920 kA / m, Hk250 kA / m, and the amount of impurity hydrogen was 0.02 wt%.

[Example 2]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the first step was set to 900 ° C. The average particle diameter of the recovered alloy powder is 24 μm, and the composition is Nd 29.3 wt%, B 1.05 wt%, Ga 0.31 wt%, Nb 0.30 wt%, O 0.18 wt%, Ca 0.01 wt%, H 0.05 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.25T, coercive force Hc 1080 kA / m, and squareness Hk 400 kA / m.

[Example 3]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the first step was 1150 ° C. The average particle size of the recovered alloy powder is 33 μm, and the composition is Nd 29.7 wt%, B 1.07 wt%, Ga 0.28 wt%, Nb 0.30 wt%, O 0.22 wt%, Ca 0.02 wt%, H 0.04 wt. %, The balance was Fe. The magnetic properties of the powder were a residual magnetic flux density Br of 1.30 T, a coercive force Hc of 980 kA / m, and a squareness of Hk 440 kA / m.

[Comparative Example 2]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the first step was set to 800 ° C., but the reduction of the rare earth oxide did not proceed and there was much undiffused iron. It was a powder.

[Comparative Example 3]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the first step was 1250 ° C. Sintering of the particles in the reaction product mixture progressed, the disintegration in the fourth step was poor, the average particle size of the recovered alloy powder was 80 μm, and the composition was Nd 29.3 wt%, B 1.05 wt%, Ga 0.31 wt%, Nb 0.30 wt%, O 2.2 wt%, Ca 3.0 wt%, H 0.23 wt%, and the balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.02T, coercive force Hc520 kA / m, and squareness Hk40 kA / m.

[Example 4]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the second step was 750 ° C. The average particle size of the recovered alloy powder is 30 μm, and the composition is Nd 29.5 wt%, B 1.06 wt%, Ga 0.30 wt%, Nb 0.28 wt%, O 0.21 wt%, Ca 0.01 wt%, H 0.09 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.25T, coercive force Hc990 kA / m, and squareness Hk390 kA / m.

[Example 5]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the second step was 850 ° C. The recovered alloy powder has an average particle size of 25 μm and a composition of Nd 29.1 wt%, B 1.06 wt%, Ga 0.28 wt%, Nb 0.28 wt%, O 0.20 wt%, Ca 0.01 wt%, H 0.11 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br 1.27T, coercive force Hc 1010 kA / m, and squareness Hk 420 kA / m.

[Comparative Example 4]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the second step was 650 ° C. The average particle size of the recovered alloy powder is 35 μm, and the composition is Nd 29.8 wt%, B 1.06 wt%, Ga 0.30 wt%, Nb 0.29 wt%, O 0.18 wt%, Ca 0.01 wt%, H 0.65 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.21T, coercive force Hc690 kA / m, and squareness Hk130 kA / m.

[Comparative Example 5]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the heat treatment temperature in the second step was 950 ° C. The average particle size of the recovered alloy powder is 29 μm, and the composition is Nd 29.8 wt%, B 1.06 wt%, Ga 0.30 wt%, Nb 0.29 wt%, O 0.18 wt%, Ca 0.01 wt%, H 0.05 % By weight, the balance being Fe. The magnetic properties of the powder were residual magnetic flux density Br1.18T, coercive force Hc730 kA / m, and squareness Hk160 kA / m.

[Example 6]
After the completion of the second step, the heat treatment temperature in the third step was lowered to 550 ° C., and the inside of the container was replaced with argon gas. Thereafter, the pressure was reduced to 5 kPa, maintained for 30 minutes, and cooled to room temperature. Except for this, a rare earth-transition metal alloy powder was produced in the same manner as in Example 1. The average particle diameter of the recovered alloy powder is 27 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.21 wt%, Ca 0.01 wt%, H 0.18 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.24T, coercive force Hc920 kA / m, and squareness Hk380 kA / m.

[Example 7]
After completion of the second step, the heat treatment temperature in the third step was raised to 850 ° C., and the inside of the container was replaced with argon gas. Thereafter, the pressure was reduced to 5 kPa, maintained for 30 minutes, and cooled to room temperature. Except for this, a rare earth-transition metal alloy powder was produced in the same manner as in Example 1. The average particle diameter of the recovered alloy powder is 28 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.31 wt%, Nb 0.28 wt%, O 0.20 wt%, Ca 0.01 wt%, H 0.04 wt. %, The balance was Fe. The magnetic properties of the powder were a residual magnetic flux density Br of 1.28 T, a coercive force Hc of 1000 kA / m, and a squareness of Hk of 400 kA / m.

[Comparative Example 6]
After the completion of the second step, the heat treatment temperature in the third step was lowered to 450 ° C., and the inside of the container was replaced with argon gas. Thereafter, the pressure was reduced to 5 kPa, maintained for 30 minutes, and cooled to room temperature. Except for this, a rare earth-transition metal alloy powder was produced in the same manner as in Example 1. The average particle diameter of the recovered alloy powder is 25 μm, and the composition is Nd 28.2 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.63 wt%, Ca 0.06 wt%, H 0.23 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br0.81T, coercive force Hc90 kA / m, and squareness Hk10 kA / m.

[Comparative Example 7]
After completion of the second step, the heat treatment temperature in the third step was raised to 950 ° C., and the inside of the container was replaced with argon gas. Thereafter, the pressure was reduced to 5 kPa, maintained for 30 minutes, and cooled to room temperature. Except for this, a rare earth-transition metal alloy powder was produced in the same manner as in Example 1. The average particle size of the recovered alloy powder is 29 μm, and the composition is Nd 29.5 wt%, B 1.07 wt%, Ga 0.33 wt%, Nb 0.28 wt%, O 0.22 wt%, Ca 0.01 wt%, H 0.03 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.14T, coercive force Hc620 kA / m, and squareness Hk210 kA / m.

[Example 8]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1, except that the heat treatment atmosphere in the third step was not reduced while argon gas was circulated. The average particle diameter of the recovered alloy powder is 29 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.24 wt%, Ca 0.01 wt%, H 0.11 wt. %, The balance was Fe. The magnetic properties of the powder were a residual magnetic flux density Br of 1.26 T, a coercive force of Hc of 1040 kA / m, and a squareness of Hk of 400 kA / m.

[Comparative Example 8]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that argon gas and hydrogen gas were circulated in the third step so that the hydrogen gas partial pressure was 20 kPa. The average particle diameter of the recovered alloy powder is 29 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.24 wt%, Ca 0.01 wt%, H 0.25 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.06T, coercive force Hc 760 kA / m, and squareness Hk 180 kA / m.

[Example 9]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the drying temperature in the fifth step was 170 ° C. The average particle diameter of the recovered alloy powder is 28 μm, and the composition is Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.23 wt%, Ca 0.01 wt%, H 0.13 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.30T, coercive force Hc1010 kA / m, and squareness Hk410 kA / m.

[Example 10]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the drying temperature in the fifth step was 350 ° C. The recovered alloy powder has an average particle size of 28 μm and a composition of Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.24 wt%, Ca 0.01 wt%, H 0.05 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br 1.29 T, coercive force Hc 1020 kA / m, and squareness Hk 420 kA / m.

[Comparative Example 9]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the drying temperature in the fifth step was 100 ° C. The average particle size of the recovered alloy powder was 28 μm, and the composition was Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.20 wt%, Ca 0.01 wt%, H 0.30 wt. %, The balance was Fe. The magnetic properties of the powder were a residual magnetic flux density Br of 1.30 T, a coercive force Hc of 710 kA / m, and a squareness of Hk of 210 kA / m.

[Comparative Example 10]
A rare earth-transition metal alloy powder was produced in the same manner as in Example 1 except that the drying temperature in the fifth step was 450 ° C. The recovered alloy powder has an average particle size of 28 μm and a composition of Nd 29.5 wt%, B 1.08 wt%, Ga 0.32 wt%, Nb 0.28 wt%, O 0.29 wt%, Ca 0.01 wt%, H 0.03 wt. %, The balance was Fe. The magnetic properties of the powder were residual magnetic flux density Br1.11T, coercive force Hc920 kA / m, and squareness Hk250 kA / m.

"Evaluation"
By comparing Example 1 and Comparative Example 1, it can be seen that the squareness Hk is remarkably improved by inserting the second and third steps between the heat treatment and the wet treatment of the reduction diffusion method.
By comparing Comparative Examples 2 and 3 with Examples 1 to 3, the target rare earth-transition metal alloy particles cannot be obtained when the heat treatment temperature in the first step is less than 850 ° C., and 1200 ° C. If it exceeds, it turns out that the squareness Hk falls. By comparing Comparative Examples 4 and 5 with Examples 1, 4 and 5, it can be seen that the squareness Hk is lowered when the heat treatment temperature in the second step is less than 700 ° C or more than 900 ° C. . Comparing Comparative Examples 6 and 7 with Examples 1, 6, and 7 shows that the squareness Hk is lowered when the heat treatment temperature in the third step is less than 500 ° C or more than 900 ° C. Comparing Comparative Example 8 with Examples 1 and 8, it can be seen that when the hydrogen gas partial pressure in the heat treatment atmosphere in the third step exceeds 10 kPa, the Hk of the alloy powder decreases. Further, comparing Comparative Examples 9 and 10 with Examples 1, 9, and 10, when the drying temperature is less than 150 ° C. in the fifth step, the amount of hydrogen exceeds 0.20 wt%, In addition, when the temperature exceeds 400 ° C., the amount of oxygen is 0.29 wt%, which is higher than that of the example, and it can be understood that the squareness Hk is lowered due to oxidation.

  INDUSTRIAL APPLICABILITY The present invention can be used in the manufacture of permanent magnets that are required to be reduced in size, weight, and performance in various electrical devices such as cellular phones, digital cameras, digital video and other home appliances. .

Claims (2)

  Mixing rare earth oxide powder, transition metal powder and / or oxide powder thereof, and at least one reducing agent selected from granular or powdery alkali metals, alkaline earth metals and hydrides thereof, A first step of obtaining a reaction product mixture containing a rare earth-transition metal alloy by maintaining the mixture at a temperature of 850 to 1200 ° C. for 1 to 10 hours in an inert atmosphere, and the reaction product mixture is reduced to 300 ° C. or lower. After cooling, the hydrogen gas is introduced, and the reaction product obtained in the second step and the second step in which the hydrogen gas is maintained at a temperature of 700 to 900 ° C. for 1 to 20 hours in an atmosphere of a hydrogen gas partial pressure of 20 to 40 kPa. Third step of heat-treating the mixture at 500 to 900 ° C. for 10 minutes to 20 hours in an atmosphere of vacuum or hydrogen gas partial pressure of less than 10 kPa, washing the heat-treated product obtained with water and containing a reducing agent And a fourth step of recovering the rare earth-transition metal alloy by removing organisms and a fifth step of drying the washed rare earth-transition metal alloy in a non-oxidizing atmosphere at 150 to 400 ° C. A method for producing a rare earth-transition metal alloy powder characterized by the above.   2. The method for producing a rare earth-transition metal alloy powder according to claim 1, wherein an average particle size of the transition metal powder and / or oxide powder thereof used in the first step is 50 μm or less.