JPH05171203A - Production of alloy powder of rare earth system for permanent magnet - Google Patents

Abstract

PURPOSE:To easily produce the alloy powder of rare earth system for a permanent magnet having excellent magnetic characteristics by subjecting alloy powder having a specific compsn. consisting of rare earth elements, iron family elements and Ti, etc., to a heating treatment in gaseous H2 from a hydrogen storage material. CONSTITUTION:The cast ingot of the alloy consisting of 7 to 9at.% R (R: rare earth elements contg. >=50% Pr or Nd), 67 to 90.5% T (T: Fe or <=50% thereof is substd. with Co, Ni), 3.5 to 17% M (M: Ti, V, Cr, Mo) is roughly pulverized. The roughly pulverized powder having 50 to 500mum average grain size and >=80% tetragonal structure ThMn12 type compd. is obtd. This powder is held for 30 minutes to 8 hours at 500 to 900 deg.C in gaseous H2 kept at 10 to 1000kPa and is then subjected to an H2 removal treatment at <=10Pa partial pressure. The hydrogen storage material is used as the main supply source for the above- mentioned gaseous H2 at this time. The resulted powder of 0.05 to 1mum is held for 30 minutes to 6 hours at 300 to 600 deg.C in the gaseous N2 of 50 to 5000kPa, by which 0.8 to 8% N is incorporated therein and the alloy powder of rare earth system for a permanent magnet is stably obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R (rare earth element) -T (iron group element) -MN magnet permanent magnet alloy having a high coercive force that can be used in various motors, actuators and the like. Regarding the improvement of the powder manufacturing method, the coarsely pulverized powder of this system is used as a H ₂ gas source in a high-purity H ₂ gas using a hydrogen storage material such as a metal hydride or a hydrogen storage alloy, and is kept heated in a predetermined atmosphere. The present invention relates to a method for producing an alloy powder for R-T-M-N based permanent magnet having a high coercive force by performing a de-H ₂ treatment to obtain ultrafine crystals of 1 μm or less and further nitriding treatment.

[0002]

2. Description of the Prior Art Alloy powders for rare earth permanent magnets, especially R-
As a method for producing a T-M-N based alloy powder for permanent magnets, the applicant has previously proposed a hydrogen treatment method in JP-A-3-149456. This hydrogen treatment method means that the RT raw material alloy ingot or powder is heated to a temperature of 500 to 1 in an H ₂ gas atmosphere or a mixed atmosphere of H ₂ gas and an inert gas.
After holding at 000 ° C. to occlude H ₂ in the alloy ingot or powder, the H ₂ gas pressure was 13 Pa (1 × 10
^-1 Torr) or less vacuum atmosphere or H ₂ gas partial pressure 13
It is characterized in that it is subjected to H ₂ removal treatment at a temperature of 500 to 1000 ° C. and then cooled until an inert gas atmosphere of Pa (1 × 10 ⁻¹ Torr) or less is obtained.

Further, a nitride rare earth permanent magnet powder is obtained by nitriding the R-T-M powder having ultrafine crystals obtained by the above method.

[0004]

However [0007] The magnetic properties of the alloy powder for a magnet produced by the above method, impurities in the H ₂ gas or inert gas used in the H ₂ treatment, in particular traces of oxygen, The water contaminates the surface layer of the ingot or the powder, and the surface contamination layer hinders the occlusion and release reaction between the H ₂ gas and the raw material ingot or the powder, so that the magnetic properties of the resulting powder are significantly deteriorated or fluctuate. There was a problem to do.

Further, when H ₂ is removed, there is a problem that the magnetic properties of the obtained powder are remarkably deteriorated or fluctuated due to contamination of the surface layer due to impurities in the inert gas or insufficient capacity of the vacuum exhaust system. .. Further, the surface contamination layer hinders the penetration of N atoms during the nitriding treatment, so that there is a problem that the penetration amount of N atoms is not stable.

In order to solve such a problem, a high-purity H ₂ gas is used as a gas to be used, and even when an inert gas is used, the high-purity inert gas is used, and then a purifying device and a cold trap are used. It is necessary to reduce the amount of impurities and lower the dew point by using, which industrially requires a high-purity refining device, which complicates the process and causes a large cost problem.

According to the present invention, in a method for producing an RT-M-N-based alloy powder for permanent magnets by a hydrogen treatment method, it is possible to prevent the magnetic properties of the obtained powder from deteriorating or generating variations, and the subsequent steps An object of the present invention is to provide a method for producing an alloy powder for a rare earth-based permanent magnet, which allows a nitriding reaction to proceed rapidly and stably and is easily produced.

[0008]

SUMMARY OF THE INVENTION The present invention, as a result of prevention of reduction and variation of the occurrence of the magnetic properties of the resulting powder, for the purpose of stabilizing the amount of inserted N atoms, and various investigations on H ₂ gas, H ₂ By using a hydrogen storage material as the main source of gas and processing with H ₂ gas from the hydrogen storage material, the amount of impurities in the H ₂ gas can be reduced at low cost, and the control of the processing atmosphere can be performed with an inert gas. The present invention has been completed based on the finding that control can be performed without using a vacuum pump or the capability of a vacuum exhaust system.

That is, the present invention provides: R: 7-9 at% (R: at least one rare earth element and 50% or more of one or two Pr or Nd), T: 67-90.5 at% (T: Fe or a part of Fe is replaced by one or two kinds of Co and Ni of 50 at% or less of T), M: 3.5 to 17 at% (M: Ti, V, Cr and Mo) At least one of them) is roughly crushed into an alloy ingot,
After the coarsely pulverized powder having an average particle size of 50 to 500 μm and 80 vol% or more of which is a tetragonal crystal structure ThMn ₁₂ type compound, the coarsely pulverized powder is used as a raw material powder and 10 to 1000 k
In H ₂ gas of Pa, heat and hold at 500 to 900 ° C. for 30 minutes to 8 hours, and further 500 at H ₂ partial pressure of 10 Pa or less.
To 900 ° C. to perform the de-H ₂ by keeping 15 minutes to 8 hours, and then after the average grain size cooled to have to obtain an alloy powder for permanent magnets is 0.05 to 1 [mu] m, then the powder N ₂
300 to 6 in N ₂ gas at a pressure of 50 to 5000 kPa
A hydrogen storage material as a main supply source of H ₂ gas used in the above treatment in a method for producing an alloy powder for a permanent magnet, which is held at 00 ° C. for 30 minutes to 6 hours and then cooled to contain N atoms in an amount of 0.8 to 8 at%. Is used to produce an alloy powder for a rare earth-based permanent magnet.

According to the present invention, in the above structure, the temperature of the hydrogen storage material is controlled by heating with hot water or a heater to control the hydrogen pressure in the raw material processing chamber, and the production of alloy powder for rare earth permanent magnets. Is the way.

[0011] The present invention, in the above configuration, the temperature of the hydrogen storage material, by cooling with a refrigerant such as cold water or liquid nitrogen, to control the hydrogen partial pressure of the material processing chamber during de H ₂ treatment It is a characteristic method for producing an alloy powder for a rare earth-based permanent magnet.

Reasons for limiting the composition R used in the raw material alloy used in the present invention, that is, the rare earth elements are Y, La, Ce, Pr, Nd, Sm, Gd,
It includes Tb, Dy, Ho, Er, Tm, and Lu, and at least one of them contains at least one or two of Pr and Nd in an amount of 50 at% or more of R, and all of R is Pr. , Nd may be one or two. The reason why 50 at% or more of R is at least one of Pr and Nd is that sufficient magnetization cannot be obtained at less than 50 at%.

When R is less than 7 at%, the coercive force is lowered due to the precipitation of αFe phase, and when it exceeds 9 at%, a large amount of ThNi ₁₇ type compound is precipitated in addition to the desired tetragonal structure ThMn ₁₂ type compound. If there are too many second phases, the magnetization of the alloy will decrease. Therefore, the range of R is 7 to 9 at%.

T is an iron group element, and Fe, Co, Ni
Fe at least 50 at% of T
It is important to contain the above. That is, Fe in T
Is less than 50 at%, sufficient magnetization cannot be obtained, which is not preferable. Further, Co has the effect of raising the Curie point and the effect of slightly increasing the anisotropic magnetic field, so C
It is particularly preferable to add o at less than 50 at% of T.
When T is less than 67 at%, the second phase having a low coercive force precipitates to deteriorate the magnetic properties, and when it exceeds 90.5 at%, αFe
Since coercive force and squareness are deteriorated by the precipitation of phases, 67-
90.5 at%.

M is an essential element for forming a tetragonal ThMn ₁₂ type compound, and it is necessary to add at least one of Ti, V, Cr and Mo. Addition amount is 3.5
When it is less than at%, the R ₂ T ₁₇ phase and the αFe phase are precipitated and the desired tetragonal ThMn ₁₂ type compound cannot be obtained.
When it exceeds t%, the magnetization is remarkably reduced, so 3.5 to 1
7 at%.

[0016] N has the effect of penetrated between lattices of the tetragonal ThMn ₁₂ type compounds, to increase the Curie point of the tetragonal ThMn ₁₂ type compounds, to impart a large uniaxial magnetic anisotropy. If N is less than 0.8 at%, its effect is not remarkable, and if it exceeds 8 at%, the tetragonal ThMn ₁₂ type compound becomes unstable, and the parent phase is R ₂ T ₁₇ phase, αFe phase, or R nitride phase. 0.8 to 8 at because it is not preferable because it decomposes into
%.

In the present invention, if the content of the tetragonal ThMn ₁₂ type compound is less than 80 vol%, the second phase is formed and the coercive force is remarkably lowered. Therefore, the volume ratio of the tetragonal ThMn ₁₂ type compound is set to 80 vol% or more.

In order to obtain a coarsely pulverized powder having a tetragonal ThMn ₁₂ type compound in a volume ratio of 80% or more, the alloy ingot is annealed at a temperature of 900 to 1200 ° C. for 1 hour or more, or in the ingot making process. It is preferable to control the cooling rate of the mold.

Reasons for limiting manufacturing conditions The hydrogen treatment method is characterized in that a coarsely pulverized powder having a required particle size does not change its size in appearance and an aggregate having an extremely fine crystal structure can be obtained. That is, tetragonal ThMn ₁₂
When a type compound is reacted with H ₂ gas at high temperature, RH ₂
~ _3, alpha iron, such as a phase separated into FeM, further removed by removing H ₂ processes the H ₂ gas, recrystallized structure is obtained again tetragonal ThMn ₁₂ type compounds.

As the coarse pulverization method of the starting material, a so-called hydrogen pulverization method by H ₂ occlusion may be used in addition to the conventional mechanical pulverization method or gas atomization method. To simplify the process, the coarse pulverization method by the hydrogen pulverization is used. The crushing step and the hydrogen treatment method for obtaining ultrafine crystals may be continuously performed in the same apparatus.

In the present invention, the average particle size of the coarsely pulverized powder is limited to 50 to 500 μm. If the average particle size is less than 50 μm, there is a risk of magnetic deterioration due to oxidation of the powder, and 500 μm.
This is because if it exceeds, it becomes difficult to give a large magnetic anisotropy by the hydrogen treatment, and it becomes difficult to uniformly nitrid the inside of the raw material powder during the nitriding treatment.

[0022] In this invention, when heating with H ₂ gas, is less than the H ₂ gas pressure 10 kPa, without decomposition reaction proceeds sufficiently in the foregoing, also the processing facility becomes too large and exceeds 1000 kPa, industrial Since it is not preferable in terms of cost and safety, the pressure range is 10 to 1000k.
It was Pa. More preferably, it is 50 to 150 kPa.

The heat treatment temperature in H ₂ gas is 500 ° C.
If the temperature is less than 1, the decomposition reaction into RH _{2 ■ 3} , αFe, Fe ₂ B, etc. does not occur, and if it exceeds 900 ° C., the RH _{2 ■ 3} becomes unstable, and the product grows to form a tetragonal ThMn ₁₂ type compound. Since it becomes difficult to obtain the ultrafine crystal structure of No. 3, the temperature range is set to 500 to 900 ° C. Regarding the heat treatment holding time, it is necessary to hold the heat treatment for 30 minutes to 8 hours in order to sufficiently carry out the above decomposition reaction.

The H ₂ partial pressure during de H ₂ treatment of the invention 10P
below the temperature range exceeding a, i.e. either does not lead to decomposition conditions RH 2 _{■ 3-phase} at 900 ° C. or less, practical de H ₂ rate is obtained even in the equilibrium theory has reached the cracking conditions Therefore, the partial pressure of H ₂ at the time of removing H ₂ was set to 10 Pa or less.

When the temperature for the H ₂ removal treatment is less than 500 ° C., H ₂ is not released from RH _{2 3} and therefore the tetragonal ThMn ₁₂ type compound is not recrystallized. Also, 900 ℃
If it exceeds, a tetragonal ThMn ₁₂ type compound is formed, but recrystallized grains grow coarsely and a high coercive force cannot be obtained. Therefore, the temperature range of the H ₂ removal treatment is 500 to 900 ° C.
The heat treatment holding time is required to be 15 minutes to 8 hours in order to sufficiently carry out the recrystallization reaction.

It is difficult to obtain an average recrystallized grain size of the tetragonal ThMn ₁₂ type compound after the H ₂ removal treatment that is substantially less than 0.05 μm. There is no characteristic advantage. On the other hand, if the average recrystallized grain size exceeds 1 μm, the coercive force of the powder decreases, which is not preferable. Therefore, the average recrystallized grain size is 0.05 to 1 μm.
And

The reason for limiting the temperature during nitriding treatment to 300 to 600 ° C. is that nitriding does not proceed below 300 ° C.
If the temperature exceeds 0 ° C, the tetragonal ThMn ₁₂ type compound is decomposed and α
This is because the Fe phase and R nitride are generated, and the magnetic characteristics are significantly deteriorated. The holding time of the nitriding treatment was set to 30 minutes to 6 hours because a sufficient nitriding reaction would not proceed if it was less than 30 minutes and a decomposition reaction similar to the above would proceed if it exceeded 6 hours. If the N ₂ pressure during the nitriding reaction is less than 50 kPa, the nitriding reaction rate is too slow to be practical, and if it exceeds 5000 kPa, the processing equipment becomes too large, which is not preferable in terms of industrial production cost. Therefore, the N ₂ pressure during nitriding is 50
˜5000 kPa.

The hydrogen storage material used in the present invention includes not only so-called hydrogen storage alloys but also all elemental metals, alloys, intermetallic compounds and their hydrides, but it is particularly useful in practice to use Mg as an elemental metal. , Ca, Ti, V, Y,
Zr, La, Ce, Pr, Nd, and Sm are mentioned, and the compound is Mg ₂ Ni, Mg ₂ Cu, CaNi ₅ , TiFe,
TiMn, TiCo, LaNi ₅ , ZrMn ₂ , and hydrides of these metals and compounds can be used.

Further, N, O, Al, Si, V, Cr, Mn, Fe, C are added to these metals and compounds for the purpose of equilibrium hydrogen dissociation pressure and extension of life as a hydrogen storage material.
O, Ni, Cu, Zn, Zr, Nb, Mo, etc. may be alloyed by adding one kind or two or more kinds or substituting the constituent elements. Also, as an alternative to La, Ce, Pr,
It is possible to use Nd, Sm and mixtures thereof. In particular, using Mm, which is a mixture of La and Ce, is useful for cost reduction. Further, these metals, alloys, compounds and their hydrides can be mixed and used.

When Mg hydride is used, the equilibrium hydrogen dissociation pressure becomes about 100 kPa at 280 ° C., which is not only suitable for the condition of heat treatment in H ₂ gas in the hydrogen treatment method, but also cooled to 50 ° C. as it is. Then turn the equilibrium hydrogen dissociation pressure becomes 1Pa conforms to de H ₂ conditions. In addition, since Mg also has a large hydrogen storage amount, there is an advantage that the amount of hydrogen storage material used can be reduced with respect to the processing raw material.

The equilibrium hydrogen dissociation pressure of the MmNi ₅ type compound is about 200 kPa at 30 ° C., which is very useful for the heat treatment in the H ₂ atmosphere in the hydrogen treatment method. For compounds such as TiFe-based, TiMn ₂ -based, and ZrMn ₂ -based compounds, the equilibrium hydrogen dissociation pressure can be adjusted to some extent by properly selecting the alloy-based compound, and the same usage as the MmNi ₅ -based compound is possible.

During the H ₂ removal treatment, in addition to the Mg-based material, Ca,
It is possible to control the hydrogen partial pressure during the H ₂ removal treatment by controlling the temperature of a rare earth metal, a metal such as Ti or Zr, or a metal hydride.

In addition, during heat treatment in an H ₂ atmosphere and during H ₂ removal
The hydrogen storage alloys used during the treatment may be different metals, alloys, or compounds, respectively, and it is also possible to use a vacuum pump for auxiliary exhaust during the H ₂ removal treatment. However, if the vacuum pump is used to evacuate auxiliaryly during the H ₂ removal treatment, the recycling rate of hydrogen gas decreases, so H ₂ gas is supplied and discharged using Mg-based metals, alloys, and compounds. Is most preferred.

The hydrogen storage amount of the main hydrogen storage materials is at room temperature and atmospheric pressure, and Mg used at 100 ° C. or higher is 850 l / k.
g, Mg ₂ Ni 400 l / kg, Zr 240 l / k
g, Ti 400 l / kg, La 230 l / kg, 1
LaNi ₅ used at 00 ° C or lower is 150 l / kg _, Ti
Fe is 200 l / kg and ZrMn ₂ is 190 l / kg. The amount of hydrogen storage material required for 1 kg of the raw material to be treated depends on the raw material composition and equipment conditions, but is at least 100
Mg used at the temperature of 0.1 ° C or higher is 0.1 kg, and Mg ₂ Ni is 0.1.
2kg, LaNi ₅ used at 100 ° C or less is 0.5k
g _, TiFe needs 0.4 kg, and ZrMn ₂ needs 0.4 kg.

It should be noted that the hydrogen storage material is pulverized by repeated H ₂ storage and release, and the hydrogen storage amount decreases.
So-called characteristic deterioration occurs, but in this respect, the plateau of the pressure-composition isotherm is technically maintained with a margin for both the upper limit and the lower limit without using the hydrogen storage capacity of the metal hydride or hydrogen storage alloy at the limit. If it is used only in a part, the number of times it can be used can be improved to a level at which there is no practical problem.

Disclosure of the Invention Based on the Drawings An example of an apparatus for carrying out the method for producing powder for RTMN-N-based permanent magnet according to the present invention will be described by explaining the operating procedure of the apparatus based on the drawings. Detailed description. The example of the apparatus shown in FIG. 1 has a configuration in which a hydrogen storage material such as Mg is operated at a temperature of 100 ° C. or higher.

A heater 20 is wound around the raw material processing chamber 1, a check valve 4 is connected via a pressure gauge 2 and a valve 3, an Ar gas pipe is connected via a valve 5, and a valve 6 is connected. Through the hydrogen storage material chamber 15, the oil diffusion pump 11 and the rotary pump 12 are connected via valves 8, 9, 10, 13 so that the raw material processing chamber 1 can be evacuated. .. Further, in the hydrogen storage material chamber 15, there is provided a cooling water pipe for sending the cooling water of the cooling water tank 19 by the circulation pump 16 and returning it to the tank after cooling.

The operation procedure of the apparatus is as follows. 1) Put the raw material in the raw material processing chamber 1. 2) The rotary pump 12, the oil diffusion pump 11, and the valves 8, 9, 10, 13 are operated to evacuate the inside of the raw material processing chamber 1 to a predetermined vacuum degree. 3) After closing the valve 8, the valve 6 is opened to communicate with the hydrogen storage material chamber 15. 4) Heater 22 provided in the hydrogen storage material chamber 15
The hydrogen storage material is heated and maintained at a predetermined temperature by. (H ₂ Release of Hydrogen Storage Material) 5) The raw material is heated and maintained at a predetermined temperature by the heater 20 in the raw material processing chamber 1. (H ₂ Occlusion Treatment of Raw Material) 6) The heater 22 is turned off, and the hydrogen storage material is cooled to a predetermined temperature with cooling water by operating the circulation pump 16, the cooling water tank 19, and the valve 21. (H ₂ storage of hydrogen storage material, dehydrogenation of raw material) 7) When the pressure in the raw material processing chamber 1 reaches a predetermined pressure or a predetermined time elapses, the valve 6 is closed and the valve 5 is opened to open the raw material processing chamber 1 Ar gas is introduced therein. When the inside of the raw material processing chamber 1 becomes atmospheric pressure or higher, the valve 3 is opened. Heater 2 at the same time
Cut to 0 and cool the raw material. 8) When the raw material is sufficiently cooled, the valve 5 is closed and the raw material is taken out. 9) If necessary, the valve 14 is operated to replenish the hydrogen storage material with the H ₂ gas consumption.

The example of the apparatus shown in FIG. 2 is LaNi _5, TiFe,
This is a configuration in which a hydrogen storage material such as ZrMn _{2 is} operated at a temperature of 100 ° C. or lower. Basically, the hydrogen storage material chamber 15 has the same configuration as the above-described device of FIG. 1, but a cooling water pipe for sending the cooling water of the previous cooling water tank 19 by the circulation pump 16 and returning it to the tank after cooling is used. In addition, a three-way cock 17 is provided to circulate the hot water from the hot water tank 18.

The operation procedure of the apparatus is as follows. 1) Put the raw material in the raw material processing chamber 1. 2) The rotary pump 12, the oil diffusion pump 11, and the valves 8, 9, 10, 13 are operated to evacuate the inside of the raw material processing chamber 1 to a predetermined vacuum degree. 3) After closing the valve 8, the valve 6 is opened to communicate with the hydrogen storage material chamber 15. 4) The hydrogen storage material is heated and maintained at a predetermined temperature by operating the circulation pump 16, the three-way cock 17, and the hot water tank 18.
(H ₂ release of hydrogen storage material) 5) Heater 20 provided in the hydrogen storage material chamber 15
The raw material is heated and maintained at a predetermined temperature by. (H ₂ Occlusion Treatment of Raw Material) 6) The hydrogen storage material is cooled to a predetermined temperature by operating the circulation pump 16, the cooling water 19, and the valve 21. (H ₂ storage of hydrogen storage material, dehydrogenation treatment of raw material) 7) When the pressure in the raw material processing chamber 1 reaches a predetermined pressure or a predetermined time elapses, the valve 6 is closed and the rotary pump 1
2. The oil diffusion pump 11 and the valves 8, 9, 10, 13 are operated to evacuate the inside of the raw material processing chamber 1 to a predetermined vacuum degree. 8) Close the valve 8 and open the valve 5 to open the raw material processing chamber 1
Ar gas is introduced therein. When the inside of the raw material processing chamber 1 becomes atmospheric pressure or higher, the valve 3 is opened. At the same time, the heater 20 is turned off to cool the raw material. 9) When the raw material is sufficiently cooled, the valve 5 is closed and the raw material is taken out. 10) If necessary, operate the valve 14 to replenish the hydrogen storage material with the amount of H ₂ gas consumed.

[0041]

According to the present invention, when a hydrogen storage material is used as a main supply source of H ₂ gas in a method of producing an RT-M-N based alloy powder for permanent magnets by a hydrogen treatment method, the hydrogen storage material is The purity of the released H ₂ gas is 99.99% or more, and since it is a dry H ₂ gas, the contamination of the surface layer of the raw material ingot or powder by impurities in the H ₂ gas is suppressed to an extremely small amount. The amount of oxygen in the obtained alloy powder can be reduced, and the nitriding treatment can be performed quickly and stably.

[0042] The hydrogen storage material has the property that the equilibrium dissociation pressure of the H ₂ gas by the temperature uniquely determined, atmospheric pressure during storage of the H ₂ gas, the atmosphere pressure during H ₂ gas emission Both have the great feature that they can be performed by controlling the temperature of the hydrogen storage material. More specifically, for example, when the hydrogen storage alloy is heated, the equilibrium hydrogen dissociation pressure increases, and as a result, gas is released from the hydrogen storage alloy, and this H ₂ gas reacts with the raw material. Conversely, when cooling the hydrogen storage alloy, the equilibrium hydrogen dissociation pressure is reduced, resulting hydrogen storage alloy absorbs H ₂ gas, it is possible to draw H ₂ gas from the raw material. Further, the H ₂ gas can be recycled between the metal hydride or the hydrogen storage alloy and the raw material powder, resulting in a great cost reduction effect during mass production _.

[0043]

【Example】

Example 1 No. 1 shown in Table 1 obtained by melting by a high frequency induction melting method. The ingots having the compositions of 1 to 8 were annealed at 1100 ° C. for 24 hours in a vacuum of 10 Pa or less so that the volume ratio of the tetragonal ThMn ₁₂ type compound in the ingot was 90% or more. This ingot was roughly crushed in an Ar gas atmosphere (O ₂ amount of 0.5% or less) with a stamp mill to an average particle size of 100 μm, and 500 g of this roughly crushed powder was put into the raw material processing chamber of the apparatus shown in FIG. It was evacuated to 1 Pa or less. Then, while introducing hydrogen from the hydrogen storage alloy container, the raw material temperature was 750 ° C., 500 g of MgH ₂ was used as a hydrogen storage material, and this was heated to 300 ° C. with an electric heater and held for 2 hours. At this time, the H ₂ pressure in the raw material processing chamber was 400 kPa and was constant during the heating and holding. Subsequently, while maintaining the raw material at 750 ° C., the hydrogen storage material, that is, MgH ₂ was cooled to 40 ° C. using cooling water at 20 ° C. and kept for 1 hour. At this time, the pressure in the raw material processing chamber finally dropped to 0.5 Pa. After that, the hydrogen absorbing alloy container was cut off from the raw material processing chamber by a valve operation, and the purity of 99.9 was set in the raw material processing chamber.
Introduce 99% or more Ar gas and cool the raw material,
The raw material was taken out when the raw material temperature reached 50 ° C. or lower. Then, the N ₂ partial pressure is 400 in N ₂ gas with 500 kPa.
After nitriding treatment at 2 ° C. for 2 hours and cooling, an RTN-M-N magnet powder having the characteristics (No. 1 to 8) shown in Table 1 was obtained. It should be noted that substantial H ₂
The gas consumption was 1 liter or less at room temperature and atmospheric pressure.

Example 2 A coarsely pulverized powder having an average particle size of 100 μm in which the volume ratio of the tetragonal ThMn ₁₂ type compound was 90% or more was produced by the same composition and the same production method as in Example 1. This coarsely crushed powder 500g is shown in FIG.
Into the raw material processing chamber of the device shown in Fig. 1, after evacuating to 1 Pa or less, while introducing hydrogen from the hydrogen storage material container,
The raw material temperature was 750 ° C., 500 g of LaNi ₅ H ₆ was used as a hydrogen storage material, and this was heated to 50 ° C. with warm water and kept for 2 hours. At this time, the H ₂ pressure in the raw material processing chamber is 400 k.
It was Pa and was constant during heating and holding. Continue to add 7
While maintaining the temperature at 50 ° C., the hydrogen storage material was cooled to 15 ° C. by using cooling water at 4 ° C., and then the valve was operated to disconnect the hydrogen storage material container from the raw material processing chamber to remove the raw material at 750 ° C.
With the temperature kept at 1, the inside of the raw material processing chamber was evacuated for 1 hour using a rotary pump and an oil diffusion pump. The ultimate vacuum at this time was 0.07 Pa. After that, Ar gas having a purity of 99.999% or more was introduced into the raw material processing chamber, the raw material was cooled, and the raw material was taken out when the raw material temperature became 50 ° C. or lower. Then N ₂ partial pressure 400 ° C. in N ₂ gas 500 kPa, R-T with 2 hours and cooled after the nitriding treatment is performed is shown in Table 1 (No.11~18) properties
-MN magnetic powder was obtained. Note that the substantial amount of H ₂ gas consumed per one treatment is approximately 5 at room temperature and atmospheric pressure.
It was 0l.

Comparative Example 8 types (No. 21 to 28) in the same process as in Example 1
A coarsely pulverized powder having the composition of was obtained. After putting 500 g of this coarsely pulverized powder into the raw material processing chamber and evacuating it to 1 Pa or less, H ₂ gas having a purity of 99.9% or more without purification treatment was introduced into the raw material processing chamber to bring it to the atmospheric pressure. While flowing 5 liters of H ₂ gas of the same purity, the temperature was raised to 750 ° C. and maintained for 2 hours. After that, the H ₂ gas was stopped while maintaining the same temperature, and vacuum pumping was performed for 1 hour using a rotary pump and an oil diffusion pump. The ultimate vacuum at that time was 0.09 Pa.
After that, Ar having a purity of 99.999% or more is placed in the raw material processing chamber.
The gas is introduced and the raw material is cooled, and the raw material temperature is 50 ° C.
The raw materials were taken out when the following conditions were reached. Then N ₂ partial pressure 400 ° C. in N ₂ gas 500 kPa, and cooled after performing a nitriding treatment of 2 hours is shown in Table 1 (No.21~
28) An R-T-M-N magnet powder having characteristics was obtained.
The substantial amount of H ₂ gas consumed per one treatment was about 950 l at room temperature and atmospheric pressure.

After mixing 2 wt% of epoxy resin with the magnetic powder prepared in Examples 1 to 3 and Comparative Example, 0.8
A bond magnet was produced by compression-molding in a magnetic field of MA / m at a pressure of 3.0 ton / cm ² and further curing the resin under the condition of a temperature of 150 ° C. for 1 hour. Table 2 shows the magnetic properties of the obtained bonded magnet.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

The R-T-M-N type permanent magnet powder according to the present invention is a heat treatment of the R-T-M type coarsely pulverized powder in high purity H ₂ gas released from the hydrogen storage material. In addition, a de-H ₂ treatment of heating and holding in a predetermined atmosphere is performed, and the average crystal grain size is 0.05 to 1 μm with the coarsely pulverized powder having the required average grain size.
It is possible to obtain a powder consisting of recrystallized grains of the above, which is less contaminated by oxygen and the like, and as is clear from the examples, the nitriding process progresses rapidly and uniformly due to the little contamination, and the magnetic properties are excellent. The alloy powder for a permanent magnet can be easily obtained, and the amount of H ₂ gas used for the reaction can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an apparatus for carrying out a method for producing a powder for permanent magnets according to the present invention.

FIG. 2 is a block diagram showing another configuration example of an apparatus for carrying out the method for producing powder for permanent magnet according to the present invention.

[Explanation of symbols]

1 Raw material processing chamber 2 Pressure gauge 3,5,6,7,8,9,10,13,14,21 Valve 4 Check valve 11 Oil diffusion pump 12 Rotary pump 15 Hydrogen storage material 16 Circulation pump 17 3-way cock 18 Temperature Water tank 19 Cooling water tank 20,22 Heater

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 1/053 1/06 // C23C 8/26 7516-4K

Claims (1)

[Claims] 1. R: 7-9 at% (R: at least one rare earth element and 50% or more of one or two of Pr or Nd), T: 67-90.5 at% (T: F
e or part of Fe is C of 50 at% or less of T
o, substituted with 1 type or 2 types of Ni), M: 3.5 to 1
An alloy ingot composed of 7 at% (M: at least one of Ti, V, Cr and Mo) is roughly crushed to obtain an average particle size of 50.
.About.500 .mu.m, more than 80 vol% of which is tetragonal structure Th
After the coarsely pulverized powder made of the Mn ₁₂ type compound is used, the coarsely pulverized powder is used as a raw material powder and the H of 10 to 1000 kPa is used.
Heated and held at 500 to 900 ° C for 30 minutes to 8 hours in ₂ gases, and 500 to 900 at H ₂ partial pressure of 10 Pa or less.
After carrying out a H ₂ removal treatment of holding at 15 ° C. for 15 minutes to 8 hours and then cooling to obtain an alloy powder for permanent magnets having an average crystal grain size of 0.05 to 1 μm, the powder is then subjected to N ₂ pressure. Fifty
Hold at 300 to 600 ° C. for 30 minutes to 6 hours in N ₂ gas of up to 5000 kPa and then cool to remove N atoms from 0.8 to 8
In the method for producing an alloy powder for permanent magnets containing at%, a hydrogen storage material is used as a main supply source of H ₂ gas used in the above treatment, a method for producing an alloy powder for a rare earth-based permanent magnet.