JP2006351688A - Producing method of samarium-iron-nitrogen-based magnet fine powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively obtain high performance magnet fine powder used for a bond magnet of magnet application equipment such as a motor by pulverizing magnet rough powder by jet mill pulverization. <P>SOLUTION: Thus producing method of the samarium-iron-nitrogen-based magnet fine powder contains, as chief ingredients, at least one kind of rare earth elements taking Sm as an essential element; a transition metal element obtained by substituting at least one kind or more of Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr, Hf, Nb, Ta, Mo, W, Ga or Al for iron or its part; and nitrogen. In the method, rough powder of the samarium-iron-nitrogen-based magnet fine powder undergoes jet mill pulverization in a jet mill pulverizing apparatus under conditions of a conveying speed of spraying gas and a pulverization time enough to provide fine powder with average particle diameter of 3 μm or less in a single time using inert gas containing 10 vol% or more of helium as conveying and spraying gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a samarium-iron-nitrogen magnet fine powder, and more specifically, a coarse magnet powder can be pulverized in a short time by jet mill pulverization, and is used in a bonded magnet for a magnet application device such as a motor. The present invention relates to a method for producing a samarium-iron-nitrogen based magnet fine powder that can efficiently obtain a fine magnet powder.

  High-performance bonded magnets using rare earth magnet powders are used in motors and other magnet application equipment. As magnet powders, rare earth magnet powders such as Sm-Co anisotropic magnet powders and Nd-Fe-B isotropic magnet powders have been mainly used so far. The magnets are gradually expanding, and magnets with various characteristics are required accordingly.

Against this background, development of new magnet powders has been actively conducted, and among them, rare earth (R) -iron (Fe) -nitrogen (N) based magnet materials, particularly samarium (Sm) -iron- Nitrogen-based magnet materials are attracting attention.
This Sm—Fe—N-based magnet material is obtained by nitriding Sm ₂ Fe ₁₇ having a Th ₂ Zn ₁₇ type structure, and a material having a composition near Sm ₂ Fe ₁₇ N ₃ has the most excellent magnetic properties. Basic physical properties of saturation magnetization (4πI _S ) of 1.57T (15.7 kG), anisotropic magnetic field (Ha) of 20.8 MA / m (260 kOe), and Curie point (Tc) of 470 ° C. have been clarified. .

The Sm-Fe-N-based alloy powder is prepared by, for example, blending an alkaline earth metal as a reducing agent in a melting alloy method using a raw material composed of a rare earth metal and a transition metal, or a raw material composed of a rare earth oxide and a transition metal, The Sm—Fe alloy powder can be first produced by a reduction diffusion method in which the rare earth oxide is reduced to a metal at high temperature and alloyed with a transition metal, and then the alloy powder can be produced by nitriding.
However, in the molten alloy method, a reduction diffusion method that can use inexpensive rare earth oxide powder as a raw material is desirable because the rare earth metal used as a raw material is expensive.

  In the reduction diffusion method, a mixture containing a rare earth oxide powder raw material, a transition metal powder raw material, and an alkaline earth metal that is a reducing agent for the rare earth oxide is first heated and fired in a non-oxidizing atmosphere, and then the rare earth-transition. Synthesize metal alloys. Thereafter, the obtained rare earth-transition metal alloy is wet-processed into powder, and then the rare earth-transition metal-nitrogen magnet is manufactured by nitriding the rare earth-transition metal alloy powder. (For example, refer to Patent Document 1). Furthermore, as an application of the reduction diffusion method, a method of manufacturing a sintered body obtained by reduction diffusion reaction by wet treatment after nitriding has been proposed (see, for example, Patent Document 2).

Since the coercive force mechanism of the Sm—Fe—N-based magnet material is a nucleation type, the coercive force must be increased. For this purpose, (1) buds that form the nuclei of reversal domain nuclei ( Two methods are conceivable: reducing the number of defects, etc.) or (2) reducing the magnet powder to the size of the single domain particle.
In order to eliminate defects by the method of (1), it is necessary to raise the temperature to near the sintering temperature, but this Sm—Fe—N magnet material decomposes into SmN and α-Fe at 650 ° C. or higher. The temperature cannot be raised above 650 ° C. For this reason, in order to increase the coercive force, fine iron powder or iron oxide powder is used as a starting material in order to reduce the particle size of the magnet powder to the desired particle size, but the manufacturing cost increases. However, the fine powder of the magnet is easily aggregated during synthesis, and as a result, the residual magnetic flux density and the squareness of the demagnetization curve are reduced. Therefore, the powdery Sm—Fe—N-based magnet powder obtained as described above is pulverized to a particle size in a specific range to be reduced to single domain particles (1 to 3 μm) (2 ) Is taken.

Until now, when pulverizing rare earth-transition metal magnet mother alloy powder, usually, using a pulverizer such as a ball mill or a medium stirring mill, iron-based balls are mixed with a solvent and magnet powder, and 0.3 to 1. Grinding was performed at a rotational peripheral speed of about 0 m / s. In this case, a submicron fine powder was generated and the particle size distribution tended to widen. For this reason, aggregation has occurred in the rare earth-transition metal magnet powder, and the magnetic properties of the finally obtained rare earth-transition metal-nitrogen magnet powder have been reduced.
Therefore, it has been proposed to use a jet mill (jet mill) in order to finely pulverize the obtained powdery rare earth-transition metal-nitrogen-based magnet to a particle size in a specific range (for example, a patent). References 3 and 4).

  According to Patent Document 3, fine particles can be obtained by jet mill pulverization without giving a large stress to the crystal structure of the powder. However, if the particle size is reduced, the pulverization efficiency is deteriorated, and expensive inert gas is used, resulting in a large cost burden. become. Therefore, it is first pulverized by collision-type jet mill pulverization, for example, until the average particle size becomes 2.5 to 20 μm, and thereafter, it is switched to a wet pulverizer and finely pulverized until the average particle size becomes 1 to 3 μm. Yes. According to this manufacturing method, the amount of expensive gas used for jet mill pulverization can be reduced. However, since the wet pulverizer is used in combination, the pulverization process becomes complicated and the pulverization time becomes longer.

  Further, in Patent Document 4 using only a jet mill pulverizer, the coercive force can be improved when the magnetic powder is finely pulverized. It is preferable to do. If the oxygen concentration is lower than this, pulverized particles whose surfaces have become active adhere to each other or the wall surface and delay the progress of pulverization, and if the oxygen concentration is too high, rapid oxidation occurs on the active particle surfaces. The possibility of dust explosion is likely to occur and handling becomes difficult, and a rapid magnetic oxidation results in the formation of a soft magnetic layer on the particle surface, resulting in a decrease in magnetic properties. As a result, a stable thin oxide film is formed on the particle surface to form fine particles having low agglomeration, and when a bonded magnet is formed, a bonded magnet with less aggregation and excellent orientation is obtained. However, this method is not suitable as a pulverization method for obtaining higher-performance magnet characteristics because the magnet powder is oxidized during pulverization.

Furthermore, a fine pulverization method has been proposed in which R ₂ Fe ₁₇ N _X- based magnet powder is pulverized by controlling the temperature of high-pressure air to 30 ° C. or lower by airflow jet mill pulverization using air as a carrier blowing gas ( For example, see Patent Document 5). According to this, since the air can be used as a carrier blowing gas without using an expensive inert gas, the manufacturing cost can be reduced. However, in this method, since air is used as a carrier blowing gas, the oxidation of the magnet powder is unavoidable, and in many cases, the particle size does not become as fine as a single pulverization, and it is necessary to pulverize many times. However, it was difficult to obtain high magnetic properties because it led to cost increase and further oxidation of the magnet powder.

Because of this, it is possible to reduce the particle size to the desired particle size by one pulverization without the need for multiple pulverization, and to obtain high magnetic characteristics without increasing the manufacturing cost or oxidizing the magnet powder. The appearance of a method for producing a samarium-iron-nitrogen based magnet fine powder that can be produced has been desired.
Japanese Examined Patent Publication No. 3-62764 JP-A-5-148517 JP-A-5-304008 JP-A-6-45121 Japanese Patent Laid-Open No. 10-12424

  In view of the above-mentioned problems of the prior art, the object of the present invention is to pulverize the coarse magnet powder in a short time by jet mill grinding, and to efficiently use the high-performance magnet fine powder used for bond magnets in magnet application equipment such as motors. It is an object of the present invention to provide a method for producing a fine samarium-iron-nitrogen magnet powder that can be obtained.

  The inventors of the present invention have made extensive studies to achieve the above object, and used an inert gas containing helium gas as an essential component as a carrier blowing gas in a pulverization method of samarium-iron-nitrogen magnet powder. By carrying out jet milling, it is found that fine grinding can be performed in a short time, and that it is possible to obtain a fine powder having an average particle size of 3 μm or less by a single jet mill grinding, thereby completing the present invention. It came to.

  That is, according to the first aspect of the present invention, at least one rare earth element containing Sm as an essential element and iron or a part thereof are Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr. In the method for producing a fine powder of samarium-iron-nitrogen magnet containing as a main component a transition metal element substituted with at least one of Hf, Nb, Ta, Mo, W, Ga, or Al, and nitrogen, Fine powder having an average particle size of 3 μm or less at a time using an inert gas containing 10% by volume or more of helium as a carrier blowing gas in a jet mill pulverizing device in the samarium-iron-nitrogen magnet coarse powder. There is provided a method for producing samarium-iron-nitrogen based magnet fine powder, characterized by jet milling under conditions of a conveying speed of a blowing gas and a pulverization time sufficient to satisfy the above conditions.

  According to a second aspect of the present invention, there is provided the method for producing a samarium-iron-nitrogen magnet fine powder according to the first aspect, wherein the coarse powder has a particle size of 106 μm or less. The

  According to a third aspect of the present invention, there is provided the method for producing a samarium-iron-nitrogen based magnet fine powder according to the first aspect, wherein the inert gas contains nitrogen and / or argon. The

  According to a fourth aspect of the present invention, there is provided the method for producing a samarium-iron-nitrogen based magnet fine powder according to the first aspect, wherein the inert gas contains helium gas in an amount of 50% by volume or more. Is done.

  Furthermore, according to a fifth invention of the present invention, in any one of the first to fourth inventions, the samarium-iron-nitrogen based magnet fine powder contains 23.2 to 23.6% by weight of a rare earth element, and A method for producing a samarium-iron-nitrogen magnet fine powder characterized by containing 3.0 to 3.5% by weight of nitrogen is provided.

  According to the present invention, since an inert gas containing helium gas as an essential component is used as a carrier blowing gas, the samarium-iron-nitrogen based magnet coarse powder is obtained with an average particle size of 3 μm by one jet mill pulverization. The following fine powder can be obtained, and fine pulverization can be efficiently performed in a short time, and multiple times of jet mill pulverization can be avoided. Since the progress of oxidation of the samarium-iron-nitrogen magnet fine powder during jet mill pulverization can be suppressed, it is possible to provide a magnet powder having higher performance magnet characteristics.

  Hereinafter, the manufacturing method of the samarium-iron-nitrogen based magnet fine powder of the present invention will be described in detail for each item using the drawings.

  The present invention relates to at least one rare earth element containing Sm as an essential element, and iron or a part thereof as Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr, Hf, Nb, Ta, Mo, In the method for producing a samarium-iron-nitrogen magnet fine powder containing nitrogen as a main component and a transition metal element substituted with at least one of W, Ga, or Al, the samarium-iron-nitrogen magnet The coarse powder is sprayed in a jet mill pulverizer, using an inert gas containing 10% by volume or more of helium as the transport spray gas, and sprayed to a degree sufficient to produce a fine powder with an average particle size of 3 μm or less at a time. It is characterized by jet mill pulverization under conditions of gas conveyance speed and pulverization time.

1. Samarium-Iron-Nitrogen Magnet Coarse Powder In the present invention, the samarium-iron-nitrogen magnet coarse powder to be pulverized may have an alloy composition generally used for magnets, and Sm is an essential element. At least one rare earth element, nitrogen, and the balance iron or a part thereof, Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr, Hf, Nb, Ta, Mo, W, Ga, or It is an alloy composition comprising a transition metal element substituted with at least one kind of Al.

  In the coarse magnet powder, rare earth elements, Sm is an essential element, a part of which can be replaced with other rare earth elements. In the case of substitution, substitution with at least one element of Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu is preferable. However, the substitution amount is preferably 50 atomic% or less in order to avoid deterioration of magnetic properties. The content of rare earth elements is desirably 23.2 to 23.6% by weight.

  The magnet coarse powder contains nitrogen as an essential component. The nitrogen content is desirably 3.0 to 3.5% by weight. When the amount of nitrogen is less than 3.0% by weight, the coercive force and the squareness are lowered, and when it exceeds 3.5% by weight, the magnetization is lowered. Furthermore, the balance is Fe, and a part thereof is at least one of Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr, Hf, Nb, Ta, Mo, W, Ga, or Al. It can be substituted with a transition metal element. However, the substitution amount is preferably 50 atomic% or less in order to avoid deterioration of magnetic properties.

In addition, the method for producing the Sm—Fe—N alloy powder is not particularly limited. For example, the Sm—Fe alloy powder is produced by a melting alloy method or a reduction diffusion method, and then the Sm—Fe alloy powder is nitrided. Can be manufactured. Further, the sintered body obtained by the reduction diffusion reaction can be wet-treated after nitriding to produce a magnet alloy powder.
Among these methods, it is preferable to manufacture by a reduction diffusion method because inexpensive rare earth oxide powder can be used as a raw material. In the reduction diffusion method, first, a mixture containing a rare earth oxide powder raw material, a transition metal powder raw material, and an alkaline earth metal that is a reducing agent for the rare earth oxide is heated and fired in a non-oxidizing atmosphere to samarium-iron. Synthesize the alloy.

As the reducing agent, Li or Ca, or an alkali metal or alkaline earth metal element composed of at least one selected from these elements and Na, K, Rb, Cs, Mg, Sr, or Ba can be used. When the alkali metal or alkaline earth metal element is contained 0.001% by weight or more in the crystalline phase of the samarium-iron alloy powder and uniformly distributed, there is an effect that the nitriding treatment can be shortened. However, if it exceeds 0.1% by weight, the magnetic properties, particularly the magnetization, of the samarium-iron-nitrogen based magnet alloy is undesirably lowered.
The raw material mixture is heated and fired in a non-oxidizing atmosphere in which an inert gas such as argon gas is circulated to a temperature at which the reducing agent does not evaporate. The heat treatment is performed in a temperature range of about 900 to 1250 ° C. and heated for 5 to 15 hours. When the heating temperature is less than 900 ° C., the diffusion of rare earth elements with respect to the iron powder becomes non-uniform, and the coercive force and squareness of the samarium-iron-nitrogen based magnet powder produced using this are reduced. If the temperature exceeds 1250 ° C., the produced samarium-iron-based metal master alloy undergoes grain growth and sinters with each other, so that uniform nitriding becomes difficult and the squareness of the magnet powder decreases. For the purpose of growing the main phase of the samarium-iron mother alloy produced by the above method, heat treatment may be performed in vacuum or in an inert gas before nitriding.

Thereafter, the obtained samarium-iron-based alloy is wet-processed to form a powder, and then the powder-like alloy is nitrided to produce a desired samarium-iron-nitrogen-based magnet coarse powder. The wet treatment is a combination of water washing, decantation, and pickling. First, the alloy is left in the atmosphere for about 0.5 to 3 hours, and then poured into, for example, about 1 liter of water per 1 kg of the alloy. Stir for ~ 3.5 hours to break down the alloy of the reduction reaction product. Thereafter, the obtained slurry is transferred to a water washing tank through a coarse sieve. At this time, the pH of the slurry is about 11 to 12, there is no lump remaining without collapsing, and the loss remaining on the sieve is very small.
Thereafter, the decantation is repeated until the pH of the slurry becomes 10 or less. The decantation condition is that water injection, stirring for 1 minute, standing separation for 1 minute, and draining should be standard conditions. The time from the start to the end of decantation is one washing time. The total amount of washing time until the pH reaches 10 is about 60 to 120 minutes. Thereafter, a mineral acid such as acetic acid is added so that the pH of the slurry is 5 to 6, pickled, solid-liquid separated, and dried to obtain a samarium-iron alloy powder. Note that the wet treatment may be performed after the nitriding treatment.

In order to efficiently perform nitriding, it is preferable to use samarium-iron mother alloy as powder. And the particle size range of this mother alloy powder is adjusted to 150 μm or less, more desirably 63 to 150 μm. The samarium-iron mother alloy may be pulverized in any form or method, but is required to be pulverized in an inert atmosphere in order to prevent oxidation of the mother alloy powder.
In the nitriding treatment of the samarium-iron mother alloy, nitrogen may be introduced into the samarium-iron mother alloy powder with ammonia gas, nitrogen gas or the like, and hydrogen gas may be used in combination with the gas in order to improve nitriding efficiency. At this time, it is effective to heat in the range of 300 to 600 ° C.
In addition, in the nitriding treatment, there are cases where the removal of the adsorbed gas on the surface of the alloy particles, the pulverization by the hydrogen gas treatment, and the heat treatment for uniformly diffusing nitrogen into the rare earth alloy powder are sometimes used.

  Here, as described above, the samarium-iron-nitrogen-based magnet has a coercive force generation mechanism of a new creation type. It is necessary to make the particle size of the magnet powder uniform, and it is finely pulverized by the following jet mill pulverization until the particle size is in a specific range. In order to efficiently carry out jet mill pulverization, it is preferable to use Sm—Fe—N magnet alloy powder having a magnetic powder particle size of 106 μm or less. And it is more preferable to adjust to a particle size of 20-63 micrometers.

2. Jet mill pulverization In order to finely pulverize samarium-iron-nitrogen based magnet coarse powder according to the present invention, an inert gas containing 10% by volume or more of helium is used as a carrier spray gas in the jet mill pulverizer. Used and jet mill pulverized under the conditions of the conveying speed of the blowing gas and the pulverization time sufficient to form a fine powder having an average particle size of 3 μm or less at a time.

  There are roughly two types of jet mill grinding. One is a collision type where powder is placed on a high-speed carrier gas and collided with a target and pulverized. The other is powder placed on a high-speed carrier gas and rotated to blow the high-speed gas from the wall of the passage. It is an air current type that collides each other and crushes them. In the collision type, a large shocking force is applied to the powder at the time of pulverization, and defects and distortions are generated inside the powder, which may deteriorate the magnetic characteristics. Therefore, in this invention, it is preferable to grind | pulverize magnet coarse powder with an airflow type jet mill.

  In the practice of the present invention, the type and structure of the preferred airflow jet mill grinder are not particularly limited as long as the object can be achieved. In general, the powder supplied to the sample inlet is accelerated at supersonic speed by the gas discharged from the pusher nozzle, enters the inside of the mill while turning, and is discharged from the grinding nozzle provided on the wall of the mill. Examples of the type of apparatus in which the powders collide with each other by the gas to be crushed or are rubbed against the wall of the mill and collide with each other. The finely pulverized powder is discharged together with the gas from the outlet, separated from the gas by a bag filter and enters the recovery device, and the insufficiently pulverized powder is pulverized by swirling through the mill.

  In order to pulverize the magnetic powder using such a jet mill pulverizer and reduce the particle size, it is effective to increase the velocity of the solid-gas mixed flow or gas flow ejected from the nozzle. Therefore, in general, the nozzle is formed as a Venturi nozzle, so-called a reduction expansion pipe, so that a supersonic flow is generated in the expansion portion. In a region where no shock wave is generated, the flow velocity at each cross section in the expansion / contraction tube increases toward the downstream, and the Mach number becomes larger than 1. When the gas flow is air or nitrogen gas, the Mach number 1 at 20 ° C. is 343 m / sec for air and 349 m / sec for nitrogen, so these gases drastically reduce the particle size after pulverization. I can't do it. On the other hand, in the case of helium gas, it becomes 1007 m / sec, and the gas flow rate increases to about 3 to 4 times that in the case of air or nitrogen gas. In the case of argon gas which is an inert gas, it is almost the same as nitrogen gas.

  Therefore, in this invention, the inert gas which contains helium 10 volume% or more is used as conveyance blowing gas. Helium can be mixed with nitrogen and / or argon. In particular, an inert gas containing 50% by volume or more of helium is preferable. If the helium content is less than 10% by volume with respect to the entire transport gas, the pulverization effect does not appear and efficient fine pulverization cannot be performed. If helium is increased, the pulverization efficiency is increased, but since it is expensive, it may be desirable that the content of helium is less than 80% by volume. The amount of oxygen in the carrier blowing gas is preferably small from the viewpoint of preventing the magnet from being oxidized, and is preferably less than 0.1% by volume with respect to the whole carrier blowing gas.

  Although hydrogen gas can be used as the carrier blowing gas, in the case of hydrogen gas, the gas flow rate at which the Mach number is 1 at 20 ° C. is larger than that of helium (1304 m / sec), so that higher pulverization efficiency is expected. However, there is a problem that it is difficult to handle because there is a risk of hydrogen explosion.

  Here, the outline of the jet mill grinding equipment used in the present invention is shown in FIG. A gas cylinder 1 for storing helium as a carrier blowing gas, a nitrogen gas or argon gas cylinder 2 installed if necessary, a reserve tank 3 for storing a mixed gas if necessary, an air flow type jet mill 4 for pulverizing raw material magnetic powder, and as required A cooling pipe 5 that cools the pulverized portion of the jet mill, a hopper 6 that stores the raw material powder, a feeder 7 that feeds the raw material powder to the jet mill, a bag filter 8 that separates the pulverized powder and gas, and a pulverized powder It consists of a collection device 9 and the like. The bag filter 8 may be provided with a gas recovery device such as a PSA (pressure swing adsorption) device or a membrane separation device to remove atmospheric components flowing in together with the raw material powder. Specific examples of such an apparatus include Labojet (trade name) and PJM-100 (trade name) manufactured by Nippon Pneumatic Industry Co., Ltd.

Since the pulverized portion of the apparatus generates heat, it is desirable to dispose the cooling pipe 5 outside the mill pulverized portion and cool it with cold water or liquid nitrogen. Further, since the carrier blowing gas is introduced from the high-pressure gas pipe to the jet mill apparatus, it is desirable to provide a cooling tank in the high-pressure pipe portion and cool the pipe itself to cool the gas. The gas temperature can be measured by attaching a thermocouple to the high-pressure pipe on the pulverizing nozzle side of the jet mill.
In order to perform jet mill pulverization according to the present invention, first, only helium gas (or a mixed gas of helium and nitrogen or argon) is fed for about 3 to 5 minutes to lower the temperature of the pulverization part of the pulverizer, so that the temperature is stable. It is preferable to start charging the sample powder after conversion.

The pressure of the carrier blowing gas is not particularly limited, but if it is lower than 0.3 MPa, a desired particle size cannot be obtained. The higher the gas pressure, the smaller the particle size of the powder obtained. However, if the pressure exceeds 0.6 MPa, the pulverization efficiency increases to some extent, but the gas is wasted, which is not preferable. Therefore, it is preferable to carry out at about 0.3-0.6 MPa. Moreover, the supply amount of the carrier blowing gas is not particularly limited, but may be, for example, 0.1 to 1 m ³ / min.
On the other hand, the conveying speed of the carrier blowing gas (amount of input powder) varies depending on the type and size of the apparatus and cannot be determined in general, but the magnet coarse powder is a fine powder having an average particle size of 3 μm or less in one pulverization. It must be enough. Therefore, it can be set to, for example, 300 to 600 g / hr. If the amount of the input powder is less than 300 g / hr, the pulverization efficiency becomes insufficient, and if it is more than 600 g / hr, the desired particle size may not be obtained at one time.

During pulverization, it is desirable to perform pulverization while controlling so that the temperature does not rise too much. When a predetermined amount of powder has been charged, the blowing of helium gas or a mixed gas of helium and nitrogen or argon can be stopped for 1 to 3 minutes. Thereafter, when the charged powder is pulverized for a predetermined time, the finely pulverized powder is recovered.
The pulverization time varies depending on the type and size of the apparatus and cannot be determined unconditionally, but can be 3 to 10 minutes, for example. If the pulverization time is shorter than 3 minutes, the pulverization is insufficient and the average particle size may exceed 3 μm, and if longer than 10 minutes, the fine powder of less than 1 μm may increase excessively.
Since the gas recovered by the gas recovery device is an expensive inert gas, it is preferable to reuse it as a carrier blowing gas.

  In the case of conventional jet mill pulverization, it may not be as fine as the target particle size in a single pulverization.In that case, pulverization was performed multiple times to achieve the target particle size. Thus, a practical samarium-iron-nitrogen magnet fine powder having a desired magnetic particle size and high magnetic properties can be obtained by one fine pulverization.

3. Samarium-iron-nitrogen-based magnet fine powder The samarium-iron-nitrogen-based magnet fine powder obtained by the above method is finely pulverized to an average particle size of 3 μm or less, preferably 2.5 μm or less. The fine magnet powder preferably contains 23.2 to 23.6% by weight of rare earth elements and 3.0 to 3.5% by weight of nitrogen. Further, it has excellent magnetic properties such that the energy product (BH) max is 280 kJ / m ³ or more. If the average particle size of the fine powder exceeds 3 μm, the magnetic properties deteriorate, which is not preferable.

The surface of the fine powder is excellent in heat resistance and by performing metal coating such as Zn, composite metal phosphate coating containing iron phosphate and rare earth metal phosphate, silicate coating, coupling agent treatment, etc. It is possible to provide corrosion resistance. Among these, when forming a composite metal phosphate film, a pulverized fine powder is not exposed to the atmosphere if a phosphoric acid treatment solution of a predetermined concentration is placed in the collection container 9 of FIG. It can be made to fall and collect in a processing solution, and thereby a much better phosphate coating can be obtained.
And if either a thermoplastic resin or a thermosetting resin is mix | blended with this samarium-iron-nitrogen based magnet powder as a binder, the resin composition for bonded magnets can be manufactured. Furthermore, a samarium-iron-nitrogen based bonded magnet having excellent magnetic properties can be obtained by molding this resin composition for bonded magnet.

  Next, although this invention is further demonstrated using an Example and a comparative example, this invention is not limited at all by these Examples. The magnet powder obtained after pulverization was measured by the following method.

(1) Particle size distribution measurement The particle size of the magnet powder obtained by pulverization was evaluated by measuring the particle size distribution based on the volume-based particle size using a laser diffraction / scattering particle size distribution analyzer (HELOS Particle Size Analysis).
(2) Magnetic properties The magnetic properties of the magnet powder obtained by pulverization were measured with a sample vibration type magnetometer (VSM).

Example 1
Metal powders having a composition of Sm ₂ —Fe ₁₇ (numbers are atomic ratios) prepared by the reduction diffusion method were classified to obtain metal powders of 106 μm or less. The obtained rare earth-iron metal powder is put into a furnace, and a mixed gas having a mixing ratio of ammonia gas and hydrogen gas of 1: 2 is flown at a rate of 1.2 ml / min per 1 g of the rare earth-iron metal powder over 120 minutes. The temperature was raised from room temperature to 465 ° C. After raising the temperature, the gas was continued to flow for 300 minutes while maintaining 465 ° C. to obtain a samarium-iron-nitrogen magnet coarse powder. Thereafter, while maintaining the temperature at 465 ° C., hydrogen annealing was performed by flowing hydrogen gas at a rate of 1 ml / min per 1 g of rare earth-iron metal powder for 30 minutes to remove excess nitrogen contained in the alloy. Further, nitrogen annealing was performed for 1 hour by flowing nitrogen gas at a rate of 1 ml / min per 1 g of rare earth-iron metal powder while maintaining at 465 ° C. Similarly, the nitrogen gas was allowed to flow during cooling to room temperature. Thereby, a samarium-iron-nitrogen magnet coarse powder having a particle size distribution of 20 to 63 μm was obtained.
Next, while flowing helium gas at a pressure of 0.4 MPa at a supply rate of 0.4 m ³ / min, this magnet coarse powder was supplied to a jet mill at a rate of 300 g per hour and pulverized for 6 minutes. With this apparatus, the outside temperature of the pulverizing part of the mill and the high-pressure gas temperature were measured, and jet mill pulverization was performed. Samarium-iron-nitrogen magnet fine powder having an average particle diameter of 1.57 μm (Sm 23.2 wt%, N 3.26 wt%) %). The particle size frequency distribution of this fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Example 2)
While the crude samarium-iron-nitrogen magnet powder obtained by the same method as in Example 1 was flowed through the jet mill apparatus with helium gas at a pressure of 0.6 MPa at a supply rate of 0.4 m ³ / min, 600 g per hour Feed in proportions and grind for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Example 3)
While the crude samarium-iron-nitrogen magnet powder obtained in the same manner as in Example 1 was supplied with a helium gas at a pressure of 0.4 MPa in a jet mill apparatus at a supply rate of 0.4 m ³ / min, 600 g per hour Feed in proportions and grind for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

Example 4
The samarium-iron-nitrogen magnet coarse powder obtained by the same method as in Example 1 was supplied at a rate of 300 g per hour while flowing a helium gas having a pressure of 0.3 MPa through the jet mill apparatus at a supply rate of 0.4 m ³ / min. Feed in proportions and grind for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Example 5)
The crude samarium-iron-nitrogen magnet powder obtained in the same manner as in Example 1 was supplied at a pressure of 0.3 MPa with a supply amount of 0.2 m ³ / min of helium gas at a pressure of 0.3 MPa to the jet mill device. While flowing a mixed gas of nitrogen gas at a supply rate of 0.2 m ³ / min, the gas was supplied at a rate of 300 g per hour and pulverized for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Example 6)
The crude samarium-iron-nitrogen magnet powder obtained by the same method as in Example 1 was supplied with helium gas at a pressure of 0.3 MPa to the jet mill device at a supply rate of 0.04 m ³ / min and a pressure of 0.3 MPa. Nitrogen gas was supplied at a rate of 300 g per hour while flowing a gas mixed at a supply rate of 0.36 m ³ / min, and pulverized for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Example 7)
The crude samarium-iron-nitrogen magnet powder obtained by the same method as in Example 1 was supplied with helium gas at a pressure of 0.3 MPa to the jet mill device at a supply rate of 0.04 m ³ / min and a pressure of 0.3 MPa. While flowing a mixed gas of argon gas at a supply rate of 0.36 m ³ / min, the gas was supplied at a rate of 300 g per hour and pulverized for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Comparative Example 1)
The raw material, the samarium-iron-nitrogen magnet coarse powder, was prepared in the same manner as in Example 1, but a vibrating ball mill was used for grinding instead of the jet mill. 15 g of samarium-iron-nitrogen magnet coarse powder was added to 288 g of stainless steel balls having a diameter of 4 mm, and pulverized in ethanol for 120 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Comparative Example 2)
The raw material, the preparation of samarium-iron-nitrogen magnet coarse powder, and the pulverization method were the same as in Example 1, except that the carrier blowing gas used during pulverization was changed to nitrogen. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Comparative Example 3)
The raw material, the preparation of samarium-iron-nitrogen magnet coarse powder, and the pulverization method were the same as in Example 1, except that the carrier blowing gas used during pulverization was changed to argon. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Comparative Example 4)
The raw material, the preparation of the samarium-iron-nitrogen magnet coarse powder, and the pulverization method were the same as in Example 7. However, the content of helium gas in the carrier blowing gas used during pulverization was reduced, and the pressure was 0.3 MPa. Of helium gas was pulverized while flowing a mixed gas of 0.02 m ³ / min and argon gas (pressure 0.3 MPa) at a rate of 0.38 m ³ / min. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

(Comparative Example 5)
The raw material, the preparation of samarium-iron-nitrogen magnet coarse powder, and the pulverization method were the same as in Example 1. However, the carrier blowing gas used during pulverization was helium gas with a pressure of 0.1 MPa, and the supply amount was 0.4 m ³ / It was supplied at a rate of 100 g per hour while flowing gas at a minute, and pulverized for 6 minutes. The particle size frequency distribution of the obtained fine powder is shown in FIG. Further, the magnetic properties of the obtained powder were measured with a sample vibration type magnetometer (VSM). These measurement results are shown in Table 1.

"Evaluation"
As in Examples 1 to 4, when samarium-iron-nitrogen magnet coarse powder was supplied to a jet mill and pulverized using helium gas, all were fine powders having an average particle size of 2 μm or less with a short pulverization time of 6 minutes. It can be seen that pulverization can be performed very efficiently. In addition, as in Examples 5 to 7, when helium gas is the main component and nitrogen gas and argon gas are mixed with this, the same results as in Examples 1 to 4 are obtained, and high grinding efficiency is achieved. I understand that I can do it. Moreover, it turns out that the pulverized powder of the obtained samarium-iron-nitrogen magnet has no deterioration in magnetic properties and has a high magnetic energy product of 280 kJ / m ³ (35 MGOe) or more.

On the other hand, in the case of Comparative Example 1 pulverized with a vibration type ball mill, by pulverizing over 120 minutes, a particle size distribution and an average particle size almost the same as those of the Example can be obtained. It can be seen that the coercive force is significantly reduced and the magnetic energy product is also reduced.
In Comparative Examples 2 and 3 where the jet mill pulverization conditions were the same as in the Examples, and pulverization was performed with nitrogen gas and argon gas alone without using helium gas, the particle size distribution was broad and the average particle size was large. It turns out that it is not pulverized efficiently. It is shown that high magnetic properties cannot be obtained with this particle size distribution. Further, in Comparative Example 4, since helium gas is used, the pulverization effect is recognized as compared with Comparative Examples 1 to 3. However, since the amount of helium is small, the pulverization efficiency is not sufficiently improved as compared with the Example. I understand. In Comparative Example 5, since helium gas is used, as in Comparative Example 4, the pulverization effect is recognized as compared with Comparative Examples 1 to 3, but the helium gas pressure is low and the amount of coarse powder supplied is small. It can be seen that the grinding efficiency is not sufficiently improved.

1 shows a schematic flow sheet of a jet mill grinding equipment used in the present invention. The particle size distribution of the magnet powder obtained by pulverization according to each example and comparative example is shown.

Explanation of symbols

1. 1. Helium gas cylinder 2. Nitrogen gas cylinder Reserve tank4. 4. Airflow type jet mill 5. Cooling pipe Hopper 7. Feeder 8. 8. Bug filter Collector

Claims (5)

At least one rare earth element containing Sm as an essential element, and iron or a part thereof, such as Co, Ti, V, Cr, Mn, Ni, Cu, Zn, Zr, Hf, Nb, Ta, Mo, W, Ga, Alternatively, in a method for producing a samarium-iron-nitrogen based magnet fine powder containing a transition metal element substituted with at least one of Al and nitrogen as main components,
Fine powder having an average particle size of 3 μm or less at a time using an inert gas containing 10% by volume or more of helium as a carrier blowing gas in a jet mill pulverizing device in the samarium-iron-nitrogen magnet coarse powder. A method for producing a samarium-iron-nitrogen magnet fine powder, characterized by jet mill pulverization under conditions of a blowing gas conveyance speed and a pulverization time sufficient to satisfy the above conditions.   The method for producing fine samarium-iron-nitrogen magnet powder according to claim 1, wherein the coarse powder has a particle size of 106 µm or less.   The method for producing a samarium-iron-nitrogen magnet fine powder according to claim 1, wherein the inert gas contains nitrogen and / or argon.   The method for producing fine samarium-iron-nitrogen based magnet powder according to claim 1, wherein the inert gas contains helium in an amount of 50% by volume or more.   The samarium-iron-nitrogen based magnet fine powder contains 23.2 to 23.6% by weight of rare earth elements and 3.0 to 3.5% by weight of nitrogen. The manufacturing method of the samarium-iron-nitrogen type magnet fine powder in any one.

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