JP2005268718A - Rare earth-iron-manganese-nitrogen based magnet powder and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide rare earth-iron-manganese-nitrogen based magnet powder that has a remarkably decreased Fe rich phase, and has an excellent square property, and to provide a method for manufacturing the powder at low cost by a reduction diffusion method. <P>SOLUTION: In the rare earth-iron-manganese-nitrogen based magnet powder containing Mn, N, and the remainder substantially containing Fe or Fe and Co, in which the N content is not less than 3.5% by weight. A phase having a Th<SB>2</SB>Zn<SB>17</SB>type crystalline structure and an amorphous phase are contained, and a coexisting Fe rich phase other than those is reduced in a degree of an intensity ratio (X) of diffraction lines of 10% or less, in powder X-ray diffraction expressed by an equation, X=I(Fe)/Im, wherein I(Fe) is intensity of a diffraction line appeared at 2θ of 44 to 45° (Cu-Kα), and Im indicates the maximum intensity in diffraction lines of the Th<SB>2</SB>Zn<SB>17</SB>type crystalline structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rare earth-iron-manganese-nitrogen based magnet powder and a method for producing the same, and more particularly, a rare earth-iron-manganese- having a significantly reduced Fe-rich phase, good coercive force and excellent squareness. The present invention relates to a nitrogen-based magnet powder and a method for producing it at a low cost by a reduction diffusion method.

  Ferrite magnets, alnico magnets, rare earth magnets, and the like are incorporated and used as motors in various products including automobiles, general household appliances, communication / audio equipment, medical equipment, and general industrial equipment. Although these magnets are mainly manufactured by a sintering method, they are fragile and difficult to be thinned, so it is difficult to form them into complex shapes, and shrinkage of 15 to 20% during sintering can not improve dimensional accuracy. Further, post-processing such as polishing is necessary, and there are significant restrictions in terms of application.

  In contrast, bond magnets can be easily manufactured by filling magnet powder with thermoplastic resin such as polyamide resin and polyphenylene sulfide resin, and thermosetting resin such as epoxy resin and phenol resin as a binder. Pioneering is unfolding.

  Among these resin binders, polyphenylene sulfide (PPS) has a high melting point exceeding 280 ° C. and also has excellent chemical resistance against organic acids, inorganic acids, strong alkalis, oils and fats, organic solvents, and the like. Therefore, bonded magnets using PPS as a binder are used for applications that require high heat resistance and chemical resistance.

Here, when the magnetic powder is a hard ferrite such as Ba ferrite or Sr ferrite, the magnetic properties are less than 20 kJ / m ³ in terms of the maximum energy product. Magnet powder is used.

Known rare earth-transition metal magnet powders include Sm—Co magnet powder, Nd—Fe—B magnet powder, and Sm—Fe—N magnet powder. Sm—Co Sm ₂ TM ₁₇ magnet PPS bonded magnets using powder (TM is Co, Fe, Cu, Zr, Hf, etc.) and Nd-Fe-B MQ magnet powder (isotropic powder made by Magnequench International) have been put into practical use. .

PPS bonded magnets using Sm—Fe—N-based Sm ₂ Fe ₁₇ N ₃ magnet powder have been proposed (for example, see Patent Document 1). However, since they are kneaded and molded at high temperatures, There is a problem that the squareness decreases.

  As resin binders having good heat resistance and chemical resistance other than PPS, aromatic polyamides and liquid crystal polymers are known, and magnets using a mixture of aromatic polyamide and aliphatic polyamide as a resin binder have been proposed. (For example, refer to Patent Document 2). As a result, a bonded magnet having an intrinsic coercive force of 8 kOe (640 kA / m) or more is obtained, but since the heat resistance of the magnet powder is insufficient, a raw material powder having an intrinsic coercive force of 16 kOe (1280 kA / m) level is used. I must.

In order to improve the heat resistance of the Sm ₂ Fe ₁₇ N ₃ magnet powder, which is a problem, the surface of the powder is treated with Zn (for example, see Patent Document 3), and the powder is treated with a phosphoric acid compound (for example, Patent Documents 4 and 5) have been proposed, but the effect has not been sufficient yet.

On the other hand, a magnetic material composed of rare earth elements, iron or iron and cobalt, manganese, and nitrogen has been proposed as an Sm-Fe-N magnet powder having excellent heat resistance (see, for example, Patent Document 6). This magnetic material is manufactured by introducing excess nitrogen more than the conventional Sm ₂ Fe ₁₇ N ₃ magnet powder into the alloy powder, and exhibits a pinning-type magnetization reversal mechanism. In addition, the metal structure has a cell-like structure in which a ferromagnetic phase having a rhombohedral or hexagonal crystal structure is surrounded by a broken or broken portion of a crystal lattice with a high N concentration. It discloses that the crystal particle diameter of the cell is 10 to 200 nm.

In this patent document 6, for example, magnet powder having a saturation magnetization of 134 emu / g (134 Am ² / kg) and an intrinsic coercive force of 4.1 kOe (328 kA / m), or a saturation magnetization of 102 emu / g (102 Am ² / kg) is inherent. A powder having a coercive force of 9.3 kOe (744 kA / m) is described. These powders maintained an excellent coercive force of 98% or more of the initial value even after being exposed to a temperature of 110 ° C. for 200 hours. According to the powder X-ray diffraction of the magnetic powder obtained here, Th _In addition to the diffraction line of the ₂ Zn ₁₇ type crystal structure, a relatively large diffraction line is observed in the vicinity of 2θ of 44 ° (Cu-Kα).

K.K. Maima et al. Studied the metal structure of a magnetic powder in which individual particles are composed of a crystal phase of Sm ₂ (Fe, Mn) ₁₇ N ₃ compound, and the structure (cell-like structure) of fine crystal grains of 10 to 30 nm. It is reported that the cell boundary is an amorphous phase (see Non-Patent Document 1). In the amorphous phase, the composition of nitrogen and manganese is considerably higher than that of the crystal phase.

  Furthermore, a magnetic powder having improved magnetic properties by incorporating at least one of Cu or Bi into a magnetic material composed of rare earth elements, iron or iron and cobalt, manganese, and nitrogen has been proposed, for example, It is said that a powder having a coercive force of 9.1 kOe (728 kA / m) with a saturation magnetization of 12.5 kG (1.25 T) can be obtained (see Patent Document 7).

  According to Patent Document 7, even if a magnet powder having good saturation magnetization and coercive force is obtained, the squareness of the demagnetization curve is poor, and it is difficult to obtain high magnetic characteristics with good reproducibility. It was. Furthermore, the rare earth-iron-manganese mother alloy powder before introducing nitrogen is manufactured by a melting method, and particularly when the rare earth element is Sm, the metal Sm as a raw material is expensive, so that the cost is also low. There was a problem.

  In addition, for rare earth-iron-manganese magnets, the particle size is adjusted for the rare earth-iron-manganese-nitrogen based magnet powder obtained by adjusting the particle size of the master alloy powder by sieving, etc., and then introducing nitrogen. For the first time, a high coercive force can be obtained, so that there is a problem in terms of cost as an industrial product in that the product yield is low.

Patent Document 6 describes that a reduction diffusion method (R / D method) is also possible as a method for preparing a mother alloy. Although the mother alloy by the reduction diffusion method has a feature that it can be manufactured at a lower cost than the melting method, a conventionally proposed method of nitriding rare earth-iron-mother alloy powder with nitrogen gas or ammonia (see Patent Documents 8 to 10). ), It was difficult to obtain a magnet powder having good performance, particularly high squareness, with good reproducibility and good yield even by the information disclosed in Patent Document 6.
Under such circumstances, the advent of a method capable of reproducibly producing a highly square magnet powder with good reproducibility, low cost and good yield has been eagerly desired.
Japanese Patent Laid-Open No. 03-160705 JP 2002-270419 A JP 09-190909 A JP 2000-05831 A JP 2002-008911 A JP 08-55712 A JP-A-11-135311 JP 05-148517 A JP 05-279714 A Japanese Patent Laid-Open No. 06-212342 K. Majima; Appl. Phys. 81 (1997) p. 4530-4532

  In view of such circumstances, the object of the present invention is to provide a rare earth-iron-manganese-nitrogen based magnet powder having a significantly reduced Fe-rich phase, good coercive force and excellent squareness, and a reduction diffusion method. It is to provide a method for manufacturing at low cost.

In order to solve such conventional problems, the present inventors diligently studied to improve the performance of rare earth-iron-manganese-nitrogen based magnet powder, and reduced and diffused the magnet raw material powder to take out the reaction product after cooling. As a result of nitriding rare earth-iron-manganese master alloy powder obtained by wet treatment and observing the structure of the obtained rare earth-iron-manganese-nitrogen based magnet powder with a transmission electron microscope, Th ₂ Zn ₁₇ type In addition to the phase having a crystal structure and the amorphous phase, a Fe-rich phase that seems to correspond to the powder X-ray diffraction results is remarkably observed, and is the squareness of the demagnetization curve worsened by this Fe-rich phase? Moreover, even if good saturation magnetization and coercive force were obtained, it was determined that high magnetic properties could not be obtained with good reproducibility, and the reaction product after the reduction-diffusion reaction was continued at a specific temperature under an inert gas atmosphere. After cooling to below By performing nitriding heat treatment before wet processing, it has been found that a magnetic powder having substantially no Fe-rich phase, high coercive force, and good demagnetization curve squareness can be obtained. It came to complete.

That is, according to the first aspect of the present invention, the rare earth element, Mn, N, the balance being substantially composed of Fe or Fe and Co, and the N content is 3.5% by weight or more. -Iron-manganese-nitrogen based magnet powder, which contains a phase having a Th ₂ Zn ₁₇ type crystal structure and an amorphous phase, and the Fe-rich phase coexisting with the other is a powder represented by the following formula There is provided a rare earth-iron-manganese-nitrogen based magnet powder characterized in that the intensity ratio (X) of diffraction lines in X diffraction is reduced to 10% or less.
X = I (Fe) / Im
[Wherein, I (Fe) is the intensity of the diffraction line where 2θ appears at 44 to 45 ° (Cu-Kα), and Im represents the maximum intensity among the diffraction lines of the Th ₂ Zn ₁₇ type crystal structure. ]

  According to a second aspect of the present invention, there is provided a rare earth-iron-manganese-nitrogen based magnet powder characterized in that, in the first aspect, the intensity ratio (X) of diffraction lines is 5% or less. Is done.

  According to the third invention of the present invention, in the first invention, the abundance of each component element is 22 to 27% by weight of rare earth elements, 7% by weight or less of Mn, and 3.5 to 3.5% of N. A rare earth-iron-manganese-nitrogen based magnet powder characterized by being 6.0% by weight is provided.

  Furthermore, according to the fourth invention of the present invention, in the third invention, a rare earth-iron-manganese-nitrogen based magnet characterized in that the N content is 4.0-5.5 wt%. A powder is provided.

  On the other hand, according to the fifth invention of the present invention, in the first to fourth inventions, the magnet raw material powder and at least one reducing agent powder selected from alkali metals, alkaline earth metals or hydrides thereof are used. A step of mixing at a predetermined ratio, a step of heating the obtained mixture to 900 to 1200 ° C. in an inert gas atmosphere, and subsequently cooling the obtained reaction product to 300 ° C. or less in an inert gas atmosphere A step of changing the atmosphere gas, and then raising the temperature in a mixed air stream containing at least ammonia and hydrogen, and nitriding heat treatment of the reaction product at 350 to 500 ° C. A method for producing a rare earth-iron-manganese-nitrogen based magnet powder is provided, which includes a step of performing wet treatment by introducing the magnet powder into the magnet.

  According to a sixth aspect of the present invention, the rare earth-iron-manganese-nitrogen based magnet according to the fifth aspect is characterized in that the ammonia partial pressure in the mixed gas stream is 0.4 to 1.0. A method for producing a powder is provided.

  Furthermore, according to the seventh aspect of the present invention, there is provided a method for producing a rare earth-iron-manganese-nitrogen based magnet powder according to the fifth aspect, wherein the time required for the nitriding heat treatment is 200 to 600 minutes. Provided.

  The rare earth-iron-manganese-nitrogen based magnet powder of the present invention is confirmed to have a significantly reduced Fe-rich phase by powder X-ray diffraction, and has a sufficient coercive force because it contains a sufficient amount of nitrogen. In addition, the squareness of the demagnetization curve is good and the magnetic properties are excellent. This magnet powder is produced by cooling a rare earth-iron-manganese master alloy, which is a reaction product after reduction diffusion, to a specific temperature in an inert gas atmosphere, and then switching the atmosphere gas to raise the temperature. It is characterized by nitriding under conditions, and has the advantage that it can be manufactured easily and at low cost.

  Hereinafter, the rare earth-iron-manganese-nitrogen based magnet powder of the present invention and the production method thereof will be described in more detail.

1. Rare earth-iron-manganese-nitrogen based magnet powder The rare earth-iron-manganese-nitrogen based magnet powder of the present invention comprises a rare earth element, Mn, N and the balance substantially consisting of Fe or Fe and Co. A rare earth-iron-manganese-nitrogen based magnet powder having a content of 3.5% by weight or more and containing a phase having a Th ₂ Zn ₁₇ type crystal structure and an amorphous phase, wherein the Fe rich phase is greatly increased Reduced rare earth-iron-manganese-nitrogen based magnet powder.

  The composition of the rare earth-iron-manganese-nitrogen based magnet powder is not particularly limited, but is 22 to 27 wt% rare earth element, 7 wt% or less Mn, and 3.5 to 6.0 wt%. % N and the balance being substantially Fe or Fe and Co are preferred. Particularly preferred is 23 to 26% by weight of rare earth elements, 2 to 5% by weight or less of Mn, 4.0 to 5.0% by weight of N, and the balance being substantially Fe or Fe and Co. Magnet powder.

As the rare earth element, Sm should be 60% by weight or more, preferably 90% by weight or more of the whole rare earth, in order to obtain a high coercive force. If the rare earth element is less than 22% by weight, the undiffused iron (-cobalt) -manganese phase remains in the magnet powder, and magnetization, coercive force, and squareness are reduced. If the rare earth element exceeds 27% by weight, a nitride phase richer in the rare earth than the Th ₂ Zn ₁₇ type Sm ₂ (Fe, Mn) ₁₇ N ₃ compound crystal phase is formed, and the magnetization and squareness of the magnet powder are formed. Decreases.

  Mn is an essential element for developing the coercive force, but when it exceeds 7% by weight, the magnetization of the magnet powder decreases. A more preferable amount of Mn is 2 to 5% by weight.

If the amount of N is less than 3.5% by weight, it becomes a type of alloy that finely pulverizes and develops coercive force, resulting in insufficient squareness, so it must be 3.5% by weight or more. However, if it exceeds 6.0% by weight, the amorphous phase in the magnet powder increases and the amorphous phase becomes the main phase of the Sm ₂ (Fe, Mn) ₁₇ N ₃ compound crystal phase having a Th ₂ Zn ₁₇ type crystal structure. In the individual cell structure having an enclosing shape, the c-axis of the Sm ₂ (Fe, Mn) ₁₇ N ₃ compound crystal phase having a Th ₂ Zn ₁₇ type crystal structure is not aligned, so that the magnetization is lowered. A more preferable N amount is 4.0 to 5.0% by weight.

  The balance is Fe, but part of it can be replaced with Co. When 20% by weight or less of Fe is replaced with Co, the Curie temperature rises, and magnetization and the temperature coefficient of magnetization can be improved.

When the structure of the rare earth-iron-manganese-nitrogen based magnet powder of the present invention is observed with a transmission electron microscope, it consists only of a phase having a Th ₂ Zn ₁₇ type crystal structure and an amorphous phase, and the Fe rich phase is greatly reduced. Yes. That is, the Fe-rich phase corresponds to, for example, an elongated portion having a width of several tens to 200 nm, which is shown by an elliptical enclosure in FIG. 2, and 2θ by powder X-ray diffraction is 44 to 45 ° (Cu— Although it is confirmed by the appearance of a broad diffraction line at the position of Kα), the intensity of the diffraction line is extremely small in the magnet powder of the present invention. Since the Fe-rich phase having soft magnetism is extremely small, there is no possibility of deteriorating the magnetic properties of the magnet powder.

In particular, in the rare earth-iron-manganese-nitrogen based magnet powder of the present invention, the intensity ratio (X) of diffraction lines in powder X-ray diffraction represented by the following formula is 10% or less, preferably 5% or less.
X = I (Fe) / Im
[Wherein, I (Fe) is the intensity of the diffraction line where 2θ appears at 44 to 45 ° (Cu-Kα), and Im represents the maximum intensity among the diffraction lines of the Th ₂ Zn ₁₇ type crystal structure. ]
In the present invention, the diffraction line of the Th ₂ Zn _17- type crystal structure having the maximum intensity usually corresponds to the plane index of (303).

  The magnet powder having an intensity ratio (X) of diffraction lines of 10% or less has a high coercive force and a good demagnetization curve squareness. When the value of X exceeds 10%, it means that an Fe-rich phase is substantially present inside, and the magnetic properties of the magnet powder are deteriorated, which is not preferable.

2. Method for producing rare earth-iron-manganese-nitrogen based magnet powder The method for producing the rare earth-iron-manganese-nitrogen based magnet powder of the present invention includes (1) magnet raw material powder, alkali metal, alkaline earth metal or hydrogen thereof. At least one reducing agent powder selected from the chemicals is mixed at a predetermined ratio, and (2) the resulting mixture is heated to 900 to 1200 ° C. in an inert gas atmosphere to obtain an oxide powder of a magnet raw material (3) Subsequently, the obtained reaction product is cooled to 300 ° C. or lower in an inert gas atmosphere. (4) Next, the atmosphere gas is changed to at least ammonia. The temperature is raised in a mixed gas stream containing hydrogen, nitriding heat treatment is performed at 350 to 500 ° C., and (5) the obtained nitriding heat treatment product is put into water and wet-treated, thereby rare earth-iron-manganese-nitrogen. Manufactured magnet powder It is a method to do.

(1) Mixing of magnet raw material powder In the present invention, a rare earth oxide powder, iron powder, manganese powder and / or manganese is used as a magnet raw material powder in order to produce rare earth-iron-manganese master alloy powder by the reduction diffusion method. Use oxide powder.

  The rare earth oxide powder is not particularly limited, but at least one element selected from Sm, Ge, Tb, and Ce, or at least selected from Pr, Nd, Dy, Ho, Er, Tm, and Yb. Those containing one kind of element are preferred. Among these, those containing Sm are particularly preferable because the effects of the present invention can be remarkably exhibited. When Sm is contained, in order to obtain a high coercive force, it is preferable to obtain Sm of 60% by weight or more, preferably 90% by weight or more of the entire rare earth, in order to obtain a high coercive force.

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 weight of the iron powder can be added as iron oxide powder to adjust the calorific value of the reduction diffusion reaction. It is also possible to add all or part of the manganese amount in the form of iron-manganese alloy powder.
Furthermore, in the case of producing a rare earth-iron-cobalt-manganese-nitrogen based magnet powder having a composition in which 20% by weight or less of Fe is substituted with Co, cobalt powder and / or cobalt oxide powder and / or iron are used as a Co source. -Cobalt-manganese alloy powder is used.

  As the manganese and cobalt source, it is preferable to use an oxide powder in order to reduce the interparticle variation in the Mn composition in the obtained rare earth-iron (-cobalt) -manganese master alloy powder. Oxides are preferable from the viewpoint of safety against ignition.

  As the manganese oxide, for example, manganese oxide, manganese dioxide, or a mixture thereof having the above particle size can be used. Moreover, as cobalt oxide, what has the said particle size by the cobalt oxide, tetroxide trioxide, and these mixtures, for example can be used.

  Here, each magnetic raw material powder is composed of iron powder in which powder having a particle size of 10 to 70 μm accounts for 80% or more of the powder, manganese powder in which powder having a particle size of 0.1 to 10 μm accounts for 80% or more of the total, and / or Or it is preferable to set it as manganese oxide powder, rare earth oxide powder, cobalt powder, and / or cobalt oxide powder.

  When the iron powder has a particle size of less than 10 μm, the rare earth-iron (-cobalt) -manganese mother alloy powder particles become a polycrystal, and the obtained rare earth-iron (-cobalt) -manganese-nitrogen magnet powder The magnetization of is easy to decrease. On the other hand, when the number of particles exceeding 70 μm increases, the rare earth-iron (-cobalt) -manganese master alloy powder has more iron parts or iron-manganese parts in which rare earth elements are not diffused and the grain size of the mother alloy powder is increased. And the nitrogen distribution becomes non-uniform, and the squareness of the obtained rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder tends to deteriorate.

  On the other hand, manganese oxide powder, rare earth oxide powder, and cobalt oxide powder, which are other raw materials, are composed of less than 30% by weight even of the most rare earth oxide powders among them. Sometimes, it is desirable that a uniform distribution exists around the iron powder inside the reaction vessel. Therefore, it is preferable that the powder having a particle size of 0.1 to 10 μm occupies 80% or more of the whole. When the powder having a particle size of less than 0.1 μm increases, the powder rises during manufacture and becomes difficult to handle. Further, when the number of particles exceeding 10 μm increases, the Mn composition in the rare earth-iron (-cobalt) -manganese master alloy powder obtained by the reduction diffusion method tends to vary among particles, and the iron part where the rare earth element is not diffused. Or the iron (-cobalt) -manganese part increases.

  Here, for iron (-cobalt) -manganese alloy powder, powder having a particle size of 10 to 80 μm accounts for 80% or more of the whole, and for rare earth oxide powder, powder having a particle size of 0.1 to 10 μm. Occupy 80% or more of the total. When the particle size is less than 10 μm, rare earth-iron (-cobalt) -manganese master alloy particles become polycrystalline, and the magnetization of the obtained rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder decreases. . On the other hand, when the number of particles exceeding 80 μm increases, the iron part or iron (-cobalt) -manganese part in which the rare earth element is not diffused increases in the rare earth-iron (-cobalt) -manganese master alloy, and the master alloy The particle size of the powder becomes large and the nitrogen distribution becomes non-uniform, so that the squareness of the obtained rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder tends to deteriorate.

(2) Reduction diffusion In the present invention, the above-mentioned magnet raw material powder is then heat-treated at a predetermined temperature in an inert gas atmosphere, and a rare earth-iron-manganese system having a Th ₂ Zn ₁₇ type crystal structure by a reduction diffusion method. Produces mother alloy powder.

  For example, as described in JP-A-61-295308, the reduction diffusion method is performed by mixing a mixture of a rare earth oxide powder, another metal powder, and a reducing agent such as Ca in an inert gas atmosphere. In this method, the reaction product is wet-treated and the reducing agent components such as CaO and residual Ca are removed by wet treatment to directly obtain alloy powder.

In the present invention, magnet raw material powder made of iron, manganese, and cobalt as required, and a reducing agent are charged into a reaction vessel, and heat treatment is performed to reduce the rare earth oxide and other oxide raw materials, A metal element such as a reduced rare earth element is diffused into the iron powder to produce a rare earth-iron (-cobalt) -manganese master alloy powder having a Th ₂ Zn ₁₇ type crystal structure.

  Here, it is important that the raw material powders are uniformly mixed so as not to be separated due to a difference in powder characteristics. As a mixing method, for example, a ribbon blender, a tumbler, an S-shaped blender, a V-shaped blender, a Nauter mixer, a Henschel mixer, a super mixer, a high speed mixer, a ball mill, a vibration mill, an attritor, a jet mill and the like can be used.

  As the reducing agent, alkali metals, alkaline earth metals, hydrides thereof, and the like can be used. From the viewpoint of safety in handling and cost, granular metallic calcium sieved to a mesh size of 4.00 mm or less is preferable. The reducing agent is mixed with the raw material powder or separated so that calcium vapor can come into contact with the raw material powder, but if mixed and reduced and diffused, the reaction product becomes porous, and the subsequent nitriding treatment is performed. Can be done efficiently.

  It is also effective to mix an additive that promotes the decay of the reaction product in the subsequent wet processing step together with the magnet raw material powder and the reducing agent. As the disintegration accelerator, alkaline earth metal salts such as calcium chloride, calcium oxide, and the like can be used, and they are uniformly mixed simultaneously with the magnet raw material powder and the like.

  The heat treatment temperature is desirably in the range of 900 to 1200 ° C. When the temperature is lower than 900 ° C., the diffusion of manganese, rare earth elements and cobalt becomes non-uniform with respect to the iron powder, and the coercive force and squareness of the rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder are reduced. On the other hand, when the temperature exceeds 1200 ° C., the rare earth-iron (-cobalt) -manganese master alloy powder produced undergoes grain growth and sinters with each other. And the squareness decreases.

For example, when metallic calcium is used as the reducing agent, the product obtained by the reduction-diffusion reaction includes rare earth-iron (-cobalt) -manganese master alloy powder having a Th ₂ Zn ₁₇ type crystal structure and calcium oxide, It is a massive mixture composed of excess metal calcium in the reaction. Furthermore, when granular metal calcium is mixed with the raw material powder and subjected to a reduction diffusion reaction, a porous massive mixture is obtained.

  On the other hand, the melting method employed in Patent Document 6 and the like uses a rare earth metal as the rare earth material, which is more expensive than the rare earth oxide material used in the reduction diffusion method. In particular, the difference is remarkable when the rare earth element is Sm that provides excellent magnetic properties. Moreover, the unnecessary powder generated by the particle size adjustment reduces the product yield and further increases the powder cost. Further, the melting method requires a homogenization heat treatment step for eliminating the αFe phase in the obtained alloy, and further, a step of coarsely pulverizing the homogenized heat treatment alloy before introducing nitrogen, and a coarsely pulverized powder. This is not preferable because a step of adjusting the particle size is required.

(3) Cooling of reaction product In the present invention, the reaction product after the reduction-diffusion reaction is continuously kept at 300 ° C or lower, preferably 250 ° C or lower, without changing the atmospheric gas as an inert gas. Cooling.

If the temperature after cooling, that is, the temperature at which a nitriding gas (mixed gas stream) containing at least ammonia and hydrogen is introduced exceeds 300 ° C., the nitriding reaction with the reaction product proceeds rapidly, and the Fe rich phase May be increased, it is desirable that the temperature be 300 ° C. or lower. This is because, at temperatures exceeding 300 ° C., active reaction products are rapidly nitrided, so that the intermetallic compound having a Th ₂ Zn ₁₇ type crystal structure is decomposed into an Fe-rich phase and SmN. It is guessed.

  After cooling, the porous massive mixture (reaction product) is transferred to the next nitriding step without wet treatment. When the reaction product is exposed to the atmosphere at this time, the active rare earth-iron (-cobalt) -manganese master alloy powder in the reaction product is oxidized and deactivated, and the degree of nitriding is varied. It is desirable to bring it into the nitriding process so as not to be exposed to the atmosphere (oxygen).

(4) Nitriding treatment In the nitriding step, the temperature is raised after changing the atmosphere gas from an inert gas to a mixed gas containing at least ammonia and hydrogen, and the reaction product is heated to a specific temperature. The nitriding gas needs to contain at least ammonia and hydrogen, and argon, nitrogen, helium, etc. can be mixed to control the reaction.

  The ratio of ammonia to the total air flow pressure (ammonia partial pressure) is 0.4 to 1.0, preferably 0.5 to 0.8. In the present invention, if the ammonia partial pressure is less than 0.4, nitriding of the mother alloy powder does not proceed even for a long time, the amount of nitrogen cannot be increased to 3.5% by weight or more, and the amorphous phase is sufficient. Since it is not formed, the residual magnetic flux density and coercive force of the magnet powder are reduced.

  The mixed gas stream containing ammonia and hydrogen is heated to 350 to 500 ° C., preferably 400 to 480 ° C., and the mother alloy powder is subjected to nitriding heat treatment. When the temperature is less than 350 ° C., it takes a long time to introduce 3.5 wt% or more of nitrogen into the rare earth-iron (-cobalt) -manganese master alloy powder in the reaction product. Disappears. On the other hand, if it exceeds 500 ° C., the squareness of the demagnetization curve of the magnet powder is lowered, which is not preferable.

  The holding time of the nitriding heat treatment is 200 to 600 minutes, preferably 300 to 550 minutes, depending on the nitriding temperature. If it is less than 200 minutes, nitriding becomes insufficient, while if it exceeds 600 minutes, nitriding proceeds excessively, which is not preferable.

According to the above-mentioned Patent Document 6, “By controlling the ammonia partial pressure in the range of 0.1 to 0.7, the nitriding efficiency is high and the magnetic material in the entire nitrogen amount range of the present invention can be produced. "The heating temperature varies depending on the composition of the master alloy and the nitriding atmosphere, but is preferably selected in the range of 200 to 650 ° C."
However, in such conditions, even if good saturation magnetization and coercive force are obtained, there is a portion where the squareness of the demagnetization curve is deteriorated, and even if magnet powder is produced under certain conditions, it is high. Magnetic properties cannot be obtained with good reproducibility. It is judged that the presence of the Fe rich phase has an influence.

  In order to suppress the generation of a phase that is presumed to be such an Fe-rich phase and 2θ forms a diffraction line at 44 to 45 ° (Cu-Kα), in the present invention, the reaction product after the reduction-diffusion reaction is After cooling to a specific temperature or lower in an inert gas atmosphere, the ambient gas is switched to a nitriding gas containing ammonia and hydrogen to raise the temperature, and the partial pressure of ammonia and the heating temperature are specified for nitriding.

  By the way, in the production of rare earth-iron (-cobalt) -nitrogen based magnet powder, when the reduction diffusion reaction product is subjected to nitriding, Patent Document 8 (Japanese Patent Laid-Open No. 05-148517) discloses a reduction diffusion reaction. The product mixture is kept at a temperature of 300 to 600 ° C. in a nitrogen atmosphere, and in Patent Document 9 (Japanese Patent Laid-Open No. 05-279714), a nitriding treatment is performed in a nitrogen or ammonia atmosphere, and the obtained heat-treated product is wet-treated. Processing. However, the rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder of the present invention cannot be obtained by such heat treatment in a nitrogen or ammonia atmosphere.

Moreover, in the Example of patent document 10 (Unexamined-Japanese-Patent No. 06-212342) for the alloy which does not contain Mn, it cools to 250 degreeC after a reduction | restoration diffusion reaction, switches to hydrogen gas, heat-processes, and also nitrogen gas The temperature is raised to 500 ° C. and nitriding. However, since Mn, which is an essential element of the present invention, is not included, the magnetic properties are not sufficient, and the N amount is 3.3 ± 0.1 wt%, which is the lower limit of the N amount of the present invention (3.5 % By weight). In addition, when nitriding with normal-pressure nitrogen gas, only a sample having x at most 3.3% by weight in Sm ₂ Fe ₁₇ N _x can be obtained.

  In the present invention, following the nitriding heat treatment, it is desirable to further heat-treat the alloy powder in an inert gas such as hydrogen gas and / or nitrogen gas, argon gas, helium gas. Particularly preferred are hydrogen gas and / or nitrogen gas and / or argon gas. Thereby, the nitrogen distribution in the individual cells constituting the magnet powder can be made more uniform, and the squareness can be improved. The holding time of the heat treatment is 30 to 200 minutes, preferably 60 to 150 minutes.

(5) Wet treatment Finally, in the present invention, a by-product of the reducing agent component (calcium oxide, calcium nitride, etc.) contained in the reaction product after the nitriding treatment is wet-treated to form a rare earth-iron (- Separate and remove from cobalt) -manganese-nitrogen magnet powder.

  As described above, the wet treatment is performed on the magnet powder after nitriding. When the reaction product is wet-treated before nitriding, the surface of the mother alloy is oxidized during the wet treatment, thereby varying the degree of nitriding. Because.

  If the reaction product is left in the atmosphere for a long time after nitriding, carbonates of reducing agent components such as calcium carbonate are generated and difficult to remove, resulting in a decrease in magnetism of the magnet powder and a decrease in squareness due to poor orientation. Or Therefore, the reaction product left in the atmosphere is preferably wet-processed within 2 weeks after being taken out from the reactor.

In the wet treatment, first, the disintegrated product is put into water, and decantation-water injection-decantation is repeated to remove much of the produced Ca (OH) ₂ . Further, if necessary, in order to remove residual Ca (OH) ₂ , acid washing is performed using acetic acid and / or hydrochloric acid. The hydrogen ion concentration of the aqueous solution at this time is preferably in the range of pH 4-7.

  After completion of the above treatment, for example, it is washed with water, dehydrated with an organic solvent such as alcohol or acetone, and dried in an inert gas atmosphere or vacuum to obtain a rare earth-iron (-cobalt) -manganese-nitrogen based magnet powder. be able to.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

The microstructure of the obtained magnet powder was observed with a transmission electron microscope (manufactured by Hitachi, Ltd., HF-2200, and JEOL Ltd., JEM-3010). The crystal structure of the microstructure was determined from the electron diffraction pattern. In some cases, using an energy dispersive X-ray analysis (EDX) and an electron energy loss analyzer (EELS JEM-2100F / STEM), tissue structure observation and composition analysis were performed. Further, the macroscopic crystal structure of the magnet powder was confirmed by a powder X-ray diffractometer (Cu-Kα, Rotaflex RAD-rVB manufactured by Rigaku Corporation, SUN SP / IPX manufactured by Mac Science Co., Ltd.). The calculation of I (Fe) / Im was performed after removing the background. The case where the intensity ratio X of the diffraction line is 10% or less and the presence of the Fe-rich phase is negligible, and the case where the intensity ratio X exceeds 10% and the presence of the Fe-rich phase cannot be ignored. It was evaluated.
The magnetic properties of the obtained magnet powder were measured with a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd., VSM-3) having a maximum applied magnetic field of 1200 kA / m. In the measurement, a sample was prepared by applying an orientation magnetic field of 1600 kA / m according to the bond magnet test method guide book BMG-2005 of the Japan Bond Magnet Industry Association, and evaluation was performed after magnetization with a magnetic field of 4000 kA / m.
The X-ray density of the powder was calculated from the analytical composition and the lattice constant of the Th ₂ Zn ₁₇ type crystal structure, and the residual magnetic flux density Br was converted with this value.

(Example 1)
As the magnet raw material powder, 332 g of iron powder (Fe purity 99%), which is produced by the atomization method and occupies 94% of the powder having a particle size of 10 to 70 μm, and the powder having a particle size of 0.1 to 10 μm as a whole. Of manganese dioxide powder (MnO ₂ purity 91%) occupying 83% of the powder and 161 g of samarium oxide powder (Sm ₂ O ₃ purity 99.5%) occupying 96% of the powder having a particle size of 0.1 to 10 μm Were weighed, and 100 g of metal calcium particles (Ca purity 99%) having a particle size of 4 mesh (Tyler mesh) or less were mixed with a Henschel mixer.
This was inserted into a stainless steel reaction vessel, and the inside of the vessel was evacuated with a rotary pump and replaced with Ar gas. Then, while flowing Ar gas, the temperature was raised to 1190 ° C, held for 4 hours, and kept at 250 ° C in the furnace. It was cooled while circulating Ar gas. Next, the Ar gas is switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.5, the temperature is raised, held at 430 ° C. for 500 minutes, and then switched to nitrogen gas at the same temperature for 30 minutes and cooled did.
The taken porous mass reaction product was immediately poured into pure water, and collapsed to obtain a slurry. From this slurry, the Ca (OH) ₂ suspension was separated by decantation, and the operation of stirring pure water for 1 minute after water injection and then decanting was repeated 5 times to obtain an alloy powder slurry.
While stirring the obtained alloy powder slurry, dilute acetic acid was added dropwise, and the pH was maintained at pH 5.0 for 7 minutes. The alloy powder was filtered, washed with water several times with ethanol, and vacuum-dried at 40 ° C. to obtain Sm—Fe—Mn—N magnet powder.
The powder composition was Sm 23.8% by weight, Mn 3.7% by weight, N 5.4% by weight, O 0.15% by weight and the balance Fe.
When the microstructure was observed with a transmission electron microscope, a cellular structure composed of a main phase having a crystal grain size of several tens of nm to several hundreds of nm and a linear crystal grain boundary phase having a width of several nm to several tens of nm. It was found that the electron diffraction pattern is composed of spots and halos, each corresponding to a main phase having a Th ₂ Zn ₁₇ type crystal structure and a grain boundary phase which is an amorphous phase. .
Further, when the amount of Mn and the amount of Fe were analyzed by EELS, in the main phase, Mn was 2.1 atomic% and Fe was 71.0 atomic%, and Mn was 2.9 with respect to the total amount of Mn and Fe. % Composition was found to be substituted. On the other hand, it was found that the amorphous phase had a composition in which Mn was 6.0 atomic% and Fe was 59.8 atomic%, and Mn was substituted by 9.1% with respect to the total amount of Mn and Fe.
Further, as a result of analysis by a powder X-ray diffraction method, as shown in FIG. 1, an alloy powder having a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα), I (Fe) / Im was 8.0%.
When the magnetic properties of the obtained magnet powder were evaluated with a vibrating sample magnetometer having a maximum magnetic field of 1200 kA / m, Br = 0.77T, Hc = 1020 kA / m, and Hk = 222 kA / m. Here, according to the bond magnet test method guidebook BMG-2005 of the Japan Bond Magnet Industry Association, a sample was prepared by applying an orientation magnetic field of 1600 kA / m, and evaluation was performed after magnetization with a magnetic field of 4000 kA / m.
The X-ray density of the powder calculated from the analytical composition and the lattice constant of the Th ₂ Zn ₁₇ type crystal structure was 7.66 g / cm ³ , and the residual magnetic flux density Br was converted with this value. Hc is a coercive force. Hk represents the squareness of the demagnetization curve, and is the magnitude of the demagnetizing field when the magnetization J takes 90% of Br in the second quadrant. The results are shown in Table 1.

(Example 2)
After the reduction-diffusion reaction, when the reaction product was cooled to 35 ° C. lower than that in Example 1 while circulating Ar gas in the furnace, the Ar gas was switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.5. Then, the temperature was raised again and maintained at 430 ° C. for 480 minutes, then, at the same temperature, the gas was switched to hydrogen gas for 120 minutes, and further switched to nitrogen gas and maintained for 30 minutes before cooling. The taken porous mass reaction product was wet-treated in the same manner as in Example 1 to obtain Sm—Fe—Mn—N magnet powder.
The powder composition was Sm 23.7% by weight, Mn 3.7% by weight, N 5.1% by weight, O 0.14% by weight and the balance Fe.
When the microstructure was observed with a transmission electron microscope, the main phase and the amorphous phase having the same Th ₂ Zn ₁₇ type crystal structure as in Example 1 were observed. Further, as a result of analysis by a powder X-ray diffraction method, as shown in FIG. 1, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and has a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα). , I (Fe) / Im was 3.8%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.90T, Hc = 948 kA, and Hk = 275 kA / m. The results are shown in Table 1.

(Conventional example 1)
In the same manner as in Example 1, the raw materials were mixed, heated to 1190 ° C while flowing Ar gas and held for 4 hours, and then the reaction product was naturally cooled to 35 ° C to form a porous massive reaction product. Was removed from the reaction vessel.
Next, when this reaction product was immediately put into pure water, it collapsed and a slurry was obtained. From this slurry, the Ca (OH) ₂ suspension was separated by decantation, the operation of stirring pure water for 1 minute after pouring, and then decanting was repeated 5 times. While stirring the obtained alloy powder slurry, dilute acetic acid was added dropwise, and the pH was maintained at pH 5.0 for 7 minutes. The alloy powder was filtered, washed with water several times with ethanol, and vacuum-dried at 40 ° C. to obtain Sm—Fe—Mn mother alloy powder.
The mother alloy powder was heated in an ammonia-hydrogen mixed gas atmosphere having an ammonia partial pressure of 0.5, held at 430 ° C. for 500 minutes, and then switched to nitrogen gas at the same temperature and held for 30 minutes. Sm—Fe—Mn—N magnet powder was obtained by heat treatment and cooling to room temperature.
The powder composition was Sm 24.4 wt%, Mn 3.7 wt%, N 4.7 wt%, O 0.17 wt%, and the balance Fe. When the microstructure was observed with a transmission electron microscope, a phase having a Th ₂ Zn ₁₇ type crystal structure and an amorphous phase similar to those in Example 1 were observed, and the width as shown in FIG. The elongate part was recognized. When this portion was subjected to energy dispersive X-ray analysis (EDX), it was confirmed to be a Fe-rich phase. As a result of further analysis by the powder X-ray diffraction method, as shown in FIG. 3, in addition to the diffraction line of the Th ₂ Zn ₁₇ type crystal structure, 2θ becomes 44.7 ° (Cu-Kα) and the Fe rich phase of FIG. Clear diffraction lines that seem to correspond were confirmed. At this time, I (Fe) / Im was 11.5%.
The magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1. As a result, Br = 0.98T, Hc = 681 kA / m, and Hk = 167 kA / m. The results are shown in Table 1.

"Evaluation"
Comparing Example 1 with Conventional Example 1, the magnet powder of Example 1 nitrided before wet processing has a small diffraction line intensity of 2θ of 44 to 45 ° (Cu-Kα), and a high coercive force and squareness. On the other hand, it can be seen that, in Conventional Example 1 that was nitrided after wet processing, an Fe-rich phase was formed, and the magnetic properties deteriorated.

(Conventional example 2)
In the same manner as in Conventional Example 1, the mother alloy was naturally cooled to 35 ° C. to obtain Sm—Fe—Mn mother alloy powder. The conditions were changed from those in Conventional Example 1, and the mother alloy powder was heated in an ammonia-hydrogen mixed gas atmosphere having an ammonia partial pressure of 0.5, held at 430 ° C. for 550 minutes, and then hydrogen gas at the same temperature. And then kept for 120 minutes, further switched to nitrogen gas, kept for 30 minutes, and then cooled to obtain Sm—Fe—Mn—N magnet powder.
The powder composition was Sm 24.3 wt%, Mn 3.6 wt%, N 5.1 wt%, O 0.17 wt% and the balance Fe. When the microstructure was observed with a transmission electron microscope, a phase having a Th ₂ Zn ₁₇ type crystal structure, an amorphous phase, and an Fe-rich phase were observed as in Conventional Example 1. Further, as a result of analysis by a powder X-ray diffraction method, as shown in FIG. 3, a diffraction line of Th ₂ Zn ₁₇ type crystal structure and a diffraction line of 2θ of 44.7 ° (Cu-Kα) were confirmed. At this time, I (Fe) / Im was 16.0%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.81T, Hc = 952 kA / m, and Hk = 143 kA / m. The results are shown in Table 1.

"Evaluation"
Comparing Example 2 with Conventional Example 2, even if the nitriding treatment conditions are adjusted so that the amount of nitrogen is equal and the coercive force is uniform, the diffraction line intensity of 2θ is 44 to 45 ° (Cu-Kα) is very high. The smaller magnet powder of Example 2 has higher residual magnetic flux density and squareness than Conventional Example 2.

(Example 3)
Compared to Examples 1 and 2, the amount of raw material powder was changed to 363 g of iron powder, 33 g of manganese dioxide powder, 174 g of samarium oxide powder, and 104 g of metal calcium particles, and held at 920 ° C. for 6 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 280 ° C., then switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.4, and nitrided at a temperature of 490 ° C. for 450 minutes. Then, it switched to nitrogen gas at the same temperature, hold | maintained for 30 minutes, and cooled.
The Sm-Fe-Mn-N magnet powder thus obtained had a chemical analysis composition of Sm 22.9% by weight, Mn 3.8% by weight, N 4.0% by weight, O 0.09% by weight, and the balance Fe. It was.
As a result of analysis by the powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα), and I (Fe) / Im is 1 It was 8%.
The magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1. As a result, Br = 0.95T, Hc = 583 kA, and Hk = 279 kA / m. The results are shown in Table 1.

Example 4
Compared with Examples 1 and 2, the amount of raw material powder was changed to iron powder 269 g, manganese dioxide powder 24 g, samarium oxide powder 131 g, and metal calcium particles 78 g, and held at 1100 ° C. for 4 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 100 ° C., then switched to ammonia gas (ammonia partial pressure 1.0), and nitrided at a temperature of 360 ° C. for 600 minutes. After that, it was switched to hydrogen gas at the same temperature and held for 120 minutes, and further switched to nitrogen gas and held for 30 minutes before cooling.
The Sm—Fe—Mn—N magnet powder thus obtained has a chemical analysis composition of Sm 26.1 wt%, Mn 3.4 wt%, N 5.3 wt%, O 0.14 wt%, and the balance Fe. It was. As a result of analysis by a powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu—Kα), and I (Fe) / Im is 7 It was 0%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, it was Br = 0.72T, Hc = 966 kA, and Hk = 216 kA / m. The results are shown in Table 1.

(Example 5)
Compared to Examples 1 and 2, the amount of raw material powder was changed to 171 g of iron powder, 30 g of manganese dioxide powder, 87 g of samarium oxide powder, and 69 g of metal calcium particles, and held at 1150 ° C. for 4 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 200 ° C., then switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.8, and nitrided at a temperature of 400 ° C. for 550 minutes. Then, it switched to nitrogen gas at the same temperature, hold | maintained for 30 minutes, and then cooled.
The Sm—Fe—Mn—N magnet powder thus obtained has a chemical analysis composition of Sm 23.0 wt%, Mn 6.4 wt%, N 5.9 wt%, O 0.08 wt%, and the balance Fe. It was. As a result of analysis by the powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu—Kα), and I (Fe) / Im is 8 It was 2%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.68T, Hc = 780 kA, and Hk = 191 kA / m. The results are shown in Table 1.

(Example 6)
Compared with Examples 1 and 2, the amount of raw material powder was changed to 332 g of iron powder, 30 g of manganese dioxide powder, 161 g of samarium oxide powder, and 100 g of metal calcium particles, and held at 1150 ° C. for 4 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 40 ° C., then switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.4, and nitrided at a temperature of 430 ° C. for 500 minutes. Then, it switched to nitrogen gas at the same temperature, hold | maintained for 30 minutes, and then cooled.
The Sm—Fe—Mn—N magnet powder thus obtained had a chemical analysis composition of Sm 25.0 wt%, Mn 3.8 wt%, N 3.8 wt%, O 0.27 wt%, and the balance Fe. It was. As a result of analysis by the powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα), and I (Fe) / Im is 6 It was 1%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.95T, Hc = 385 kA, and Hk = 237 kA / m. The results are shown in Table 1.

(Example 7)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 2 except that no heat treatment with hydrogen gas and nitrogen gas was performed after the nitriding heat treatment.
The obtained magnet powder had a chemical analysis composition of Sm 23.7 wt%, Mn 3.7 wt%, N 5.3 wt%, O 0.13 wt%, and the balance Fe.
As a result of analysis by the powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα), and I (Fe) / Im is 4 It was 7%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.88T, Hc = 968 kA, and Hk = 251 kA / m. The results are shown in Table 1.

(Example 8)
Compared to Examples 1 and 2, the raw material powder was blended in an amount of 242 g of iron powder, 24 g of manganese dioxide powder, 131 g of samarium oxide powder, and cobalt oxide powder (CoO, which accounted for 82% of the powder having a particle size of 0.1 to 10 μm). The purity was changed to 27 g and metal calcium particles 74 g, and kept at 1190 ° C. for 4 hours while flowing Ar gas, followed by a reduction diffusion reaction, cooled to 250 ° C., and then with an ammonia partial pressure of 0.5 Switching to the ammonia-hydrogen mixed gas, nitriding was performed at a temperature of 430 ° C. for 600 minutes. Then, it switched to hydrogen gas at the same temperature, hold | maintained for 120 minutes, and also switched to nitrogen gas, and hold | maintained for 30 minutes, Then, it cooled.
The obtained Sm-Fe-Co-Mn-N magnet powder has a chemical analysis composition of Sm 24.0 wt%, Co 6.8 wt%, Mn 3.6 wt%, N4.6 wt%, O 0.09 wt% The balance was Fe.
As a result of analysis by the powder X-ray diffraction method, the alloy powder has a Th ₂ Zn ₁₇ type crystal structure and a very weak diffraction line at 2θ of 44 to 45 ° (Cu-Kα), and I (Fe) / Im is 3 It was 5%.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.91T, Hc = 792 kA, and Hk = 288 kA / m. The results are shown in Table 1.

(Comparative Example 1)
After the reductive diffusion reaction, Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the Ar gas was switched to the ammonia-hydrogen mixed gas when it was cooled to 350 ° C.
The obtained magnet powder had a chemical analysis composition of Sm 23.8% by weight, Mn 3.7% by weight, N 5.8% by weight, O 0.20% by weight and the balance Fe. As in Example 1, the magnetic characteristics were evaluated. As a result, Br = 0.72T, Hc = 1050 kA, and Hk = 158 kA / m, and the residual magnetic flux density and the squareness were reduced as compared with Example 1. As a result of analysis by the powder X-ray diffraction method, a diffraction line having a Th ₂ Zn ₁₇ type crystal structure and a clear diffraction line having 2θ of 44.7 ° (Cu-Kα) were confirmed. At this time, I (Fe) / Im was 13.4%. The results are shown in Table 1.

(Comparative Example 2)
After the reductive diffusion reaction, Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the Ar gas was switched to an ammonia-hydrogen mixed gas when it was cooled to 430 ° C.
The obtained magnet powder had a chemical analysis composition of Sm 23.6 wt%, Mn 3.7 wt%, N 6.3 wt%, O 0.22 wt%, and the balance Fe. When the magnetic characteristics were evaluated in the same manner as in Example 1, the residual magnetic flux density and the squareness were reduced as compared with Example 1, with Br = 0.60T, Hc = 1130 kA, and Hk = 121 kA / m. As a result of analysis by the powder X-ray diffraction method, a diffraction line having a Th ₂ Zn ₁₇ type crystal structure and a clear diffraction line having 2θ of 44.7 ° (Cu-Kα) were confirmed. At this time, I (Fe) / Im was 17.3%. The results are shown in Table 1.

(Comparative Example 3)
Compared with Examples 1 and 2, manganese dioxide powder was not blended as a raw material powder, but the blending amount was changed to 317 g of iron powder, 126 g of samarium oxide powder, 91 g of metal calcium particles, and kept at 1150 ° C. for 4 hours while flowing Ar gas. After the reduction diffusion reaction, the mixture was cooled to 40 ° C., then switched to ammonia gas (ammonia partial pressure 1.0), and nitrided at a temperature of 450 ° C. for 400 minutes. After that, it was switched to nitrogen gas at the same temperature and kept for 30 minutes, and then cooled.
The obtained Sm—Fe—N magnet powder had a chemical analysis composition of Sm 24.1 wt%, N 4.6 wt%, O 0.18 wt%, and the balance Fe. In powder X-ray diffraction, only the diffraction line of the Th ₂ Zn ₁₇ type crystal structure was observed, but no diffraction line with 2θ of 44.7 ° (Cu—Kα) was observed, but the magnetic properties were evaluated in the same manner as in Example 1. As a result, it was found that when Br = 0.39T, Hc = 183 kA, Hk = 44 kA / m, and not containing Mn, the residual magnetic flux density, the coercive force and the squareness were significantly reduced as compared with Example 1. The results are shown in Table 1.

(Comparative Example 4)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the nitriding heat treatment was switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.35.
The obtained magnet powder had a chemical analysis composition of Sm 23.9% by weight, Mn 3.8% by weight, N 3.4% by weight, O 0.13% by weight, and the balance Fe. As in Example 1, when the magnetic properties were evaluated, Br = 0.47T, Hc = 310 kA, Hk = 39 kA / m, and since the N content was smaller than that in Example 1, the residual magnetic flux density, The coercive force and squareness were greatly reduced. Although the microstructure was observed with a transmission electron microscope, it was a single phase having a Th ₂ Zn ₁₇ type crystal structure and no amorphous phase was observed. The results are shown in Table 1.

(Comparative Example 5)
Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the nitriding gas was ammonia gas (ammonia partial pressure 1.0), heated at 330 ° C. and held for 1440 minutes.
The obtained magnet powder had a chemical analysis composition of Sm 23.9 wt%, Mn 3.7 wt%, N 2.9 wt%, O 0.09 wt%, and the balance Fe. As in Example 1, the magnetic characteristics were evaluated. As a result, Br = 0.44T, Hc = 338 kA, and Hk = 32 kA / m, and the residual magnetic flux density, coercive force, and squareness were significantly reduced compared to Example 1. did.
It can be seen that if the temperature for the nitriding heat treatment is less than 350 ° C., sufficient nitrogen does not enter even if the nitriding time is set to be twice or more, and the magnetic properties are lowered. Although the microstructure was observed with a transmission electron microscope, it was a single phase having a Th ₂ Zn ₁₇ type crystal structure and no amorphous phase was observed. The results are shown in Table 1.

(Comparative Example 6)
The Sm—Fe—Mn—N magnet powder was prepared in the same manner as in Example 2 except that the nitriding gas was an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.4, heated to 420 ° C. and held for 180 minutes. Manufactured.
The obtained magnet powder had a chemical analysis composition of Sm 23.7% by weight, Mn 3.8% by weight, N 3.3% by weight, O0.11% by weight, and the balance Fe. In powder X-ray diffraction, only the diffraction line of the Th ₂ Zn ₁₇ type crystal structure was observed, but no diffraction line with 2θ of 44.7 ° (Cu—Kα) was observed, but the magnetic properties were evaluated in the same manner as in Example 1. As a result, Br = 0.42T, Hc = 274 kA, Hk = 72 kA / m, and when the nitrogen content was less than 3.5% by weight, the N content was lower than that in Example 2, so that the residual magnetic flux density, It was found that the magnetic force and the squareness were greatly reduced. Although the microstructure was observed with a transmission electron microscope, it was a single phase having a Th ₂ Zn ₁₇ type crystal structure and no amorphous phase was observed. The results are shown in Table 1.

(Comparative Example 7)
After the reductive diffusion reaction, an Sm—Fe—Mn—N magnet powder was obtained in the same manner as in Example 1 except that the gas switched after cooling to 250 ° C. was changed to nitrogen gas.
The powder composition was Sm 24.2% by weight, Mn 3.8% by weight, N 2.9% by weight, O 0.19% by weight and the balance Fe. The magnetic characteristics were evaluated in the same manner as in Example 1. As a result, Br = 0.38T, Hc = 151 kA / m, and Hk = 27 kA / m. It was found that the magnetic properties were greatly deteriorated due to insufficient nitriding. Although the microstructure was observed with a transmission electron microscope, it was a single phase having a Th ₂ Zn ₁₇ type crystal structure and no amorphous phase was observed. The results are shown in Table 1.

(Comparative Example 8)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the nitriding gas was an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.4 and heated to 520 ° C. and held for 400 minutes.
The obtained magnet powder had a chemical analysis composition of Sm 23.6 wt%, Mn 3.6 wt%, N 5.8 wt%, O 0.11 wt%, and the balance Fe. As in Example 1, the magnetic properties were evaluated. As a result, Br = 0.75T, Hc = 1083 kA, and Hk = 137 kA / m, and the squareness was lower than that in Example 1. As a result of analysis by the powder X-ray diffraction method, a diffraction line having a Th ₂ Zn ₁₇ type crystal structure and a clear diffraction line having 2θ of 44.7 ° (Cu-Kα) were confirmed. At this time, I (Fe) / Im was 15.2%.
It can be seen that when the temperature for nitriding heat treatment exceeds 500 ° C., diffraction lines having 2θ of 44.7 ° (Cu—Kα) are generated, and the squareness is lowered. The results are shown in Table 1.

(Reference Example 1)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the reduction diffusion reaction was carried out at 880 ° C. for 6 hours.
The obtained magnet powder had a chemical analysis composition of Sm 23.5 wt%, Mn 3.9 wt%, N 4.5 wt%, O 0.07 wt%, and the balance Fe. When the magnetic characteristics were evaluated in the same manner as in Example 1, the residual magnetic flux density, the coercive force, and the squareness were reduced as compared with Example 1 at Br = 0.54T, Hc = 512 kA, and Hk = 43 kA / m. When the powder was embedded in the resin and the cross section was observed with a scanning electron microscope, a portion where Sm was not sufficiently diffused was observed near the center of the powder. The results are shown in Table 1.

(Reference Example 2)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 1 except that the reduction diffusion reaction was carried out at 1230 ° C. for 3 hours.
The obtained magnet powder had a chemical analysis composition of Sm 23.7 wt%, Mn 3.7 wt%, N 5.7 wt%, O 0.19 wt%, and the balance Fe. As in Example 1, the magnetic characteristics were evaluated. As a result, Br = 0.69T, Hc = 922 kA, Hk = 181 kA / m, and the residual magnetic flux density and the squareness were reduced as compared with Example 1. When the powder was observed with a scanning electron microscope, many powders that were sintered and aggregated were observed. The results are shown in Table 1.

(Reference Example 3)
Compared to Examples 1 and 2, the amount of the raw material powder was changed to 897 g of iron powder, 81 g of manganese dioxide powder, 426 g of samarium oxide powder, and 264 g of metal calcium particles, and held at 1150 ° C. for 4 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 40 ° C., then switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.5, and nitrided at a temperature of 450 ° C. for 500 minutes. After that, it was switched to nitrogen gas at the same temperature and kept for 30 minutes, and then cooled.
The Sm-Fe-Mn-N magnet powder thus obtained has a chemical analysis composition of Sm 21.7% by weight, Mn 3.7% by weight, N 4.8% by weight, O 0.07% by weight and the balance Fe. It was.
When the magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1, Br = 0.61T, Hc = 293 kA, Hk = 74 kA / m, and the residual magnetic flux density, coercive force and The squareness was greatly reduced. When the powder was embedded in the resin and the cross section was observed with a scanning electron microscope, a portion where Sm was not sufficiently diffused was observed near the center of the powder. The results are shown in Table 1.

(Reference Example 4)
Sm-Fe-Mn was performed in the same manner as in Comparative Example 8 except that the amount of the raw material powder was changed to 897 g of iron powder, 81 g of manganese dioxide powder, 534 g of samarium oxide powder, and 313 g of metallic calcium particles. -N magnet powder was obtained.
The chemical analysis composition of the magnet powder was Sm 27.5 wt%, Mn 3.2 wt%, N 5.4 wt%, O 0.18 wt%, and the balance Fe.
The magnetic properties of the obtained magnet powder were evaluated in the same manner as in Example 1. As a result, Br = 0.55T, Hc = 891 kA, Hk = 171 kA / m, and the residual magnetic flux density and squareness were higher than in Example 1. Declined. The results are shown in Table 1.

(Reference Example 5)
Compared to Examples 1 and 2, the amount of raw material powder was changed to iron powder 269 g, manganese dioxide powder 48 g, samarium oxide powder 126 g, and metal calcium particles 95 g, and held at 1150 ° C. for 4 hours while flowing Ar gas, and reduced diffusion. After the reaction, the mixture was cooled to 40 ° C., then switched to an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.6, and nitrided at a temperature of 400 ° C. for 420 minutes. Then, it switched to nitrogen gas at the same temperature, hold | maintained for 30 minutes, and then cooled.
The obtained Sm—Fe—Mn—N magnet powder had a chemical analysis composition of Sm 24.3 wt%, Mn 7.3% wt, N 5.8 wt%, O 0.23 wt%, and the balance Fe. In powder X-ray diffraction, only the diffraction line of the Th ₂ Zn ₁₇ type crystal structure was observed, but no diffraction line with 2θ of 44.7 ° (Cu—Kα) was observed, but the magnetic properties were evaluated in the same manner as in Example 1. As a result, Br = 0.51T, Hc = 943 kA, Hk = 201 kA / m, and the residual magnetic flux density was lower than that in Example 1. The results are shown in Table 1.

(Reference Example 6)
An Sm—Fe—Mn—N magnet powder was produced in the same manner as in Example 2 except that the nitriding gas was an ammonia-hydrogen mixed gas having an ammonia partial pressure of 0.8, heated to 450 ° C. and held for 500 minutes.
The obtained magnet powder had a chemical analysis composition of Sm 23.5 wt%, Mn 3.6 wt%, N 6.2 wt%, O 0.09 wt%, and the balance Fe. In powder X-ray diffraction, only the diffraction line of the Th ₂ Zn ₁₇ type crystal structure was observed, but no diffraction line with 2θ of 44.7 ° (Cu—Kα) was observed, but the magnetic properties were evaluated in the same manner as in Example 1. As a result, when Br = 0.78T, Hc = 803 kA, Hk = 120 kA / m, and the nitrogen content exceeds 6.0% by weight, the residual magnetic flux density, coercive force and squareness are greatly reduced as compared with Example 2. I found out that The results are shown in Table 1.

  Unlike the conventional magnet powder, the rare earth-iron-manganese-nitrogen based magnet powder of the present invention has a significantly reduced Fe-rich phase and contains sufficient nitrogen, and thus has a higher coercive force than the conventional powder. And has squareness. Therefore, it can be used as a powder for bonded magnets that require good heat resistance, and its industrial value is extremely high.

It is an X-ray diffraction pattern of Sm-Fe-Mn-N magnet powder obtained by the present invention (Example 1 and Example 2). It is the transmission electron micrograph (2-a) and EDX profile (2-b) of the Sm-Fe-Mn-N magnet powder manufactured by the conventional method (conventional example 1). It is an X-ray diffraction pattern of the Sm-Fe-Mn-N magnet powder manufactured by the conventional method (conventional example 1 and conventional example 2).

Claims (7)

A rare earth-iron-manganese-nitrogen based magnet powder comprising a rare earth element, Mn, N, and the balance being substantially Fe or Fe and Co, wherein the N content is 3.5% by weight or more,
The Fe-rich phase containing a phase having a Th ₂ Zn ₁₇ type crystal structure and an amorphous phase and coexisting with the other has an intensity ratio (X) of diffraction lines in powder X diffraction represented by the following formula of 10 % Rare earth-iron-manganese-nitrogen based magnet powder characterized by being reduced to less than or equal to%.
X = I (Fe) / Im
[Wherein, I (Fe) is the intensity of the diffraction line where 2θ appears at 44 to 45 ° (Cu-Kα), and Im represents the maximum intensity among the diffraction lines of the Th ₂ Zn ₁₇ type crystal structure. ]   The rare earth-iron-manganese-nitrogen based magnet powder according to claim 1, wherein the intensity ratio (X) of diffraction lines is 5% or less.   2. The rare earth element according to claim 1, wherein the content of each component element is 22 to 27% by weight of rare earth elements, 7% by weight or less of Mn, and 3.5 to 6.0% by weight of N. Iron-manganese-nitrogen magnet powder.   4. The rare earth-iron-manganese-nitrogen based magnet powder according to claim 3, wherein the N content is 4.0 to 5.5% by weight.   A step of mixing the magnet raw material powder and at least one reducing agent powder selected from alkali metals, alkaline earth metals or their hydrides at a predetermined ratio, and the resulting mixture in an inert gas atmosphere is 900 to A step of heating to 1200 ° C., a step of cooling the obtained reaction product to 300 ° C. or less in an inert gas atmosphere, and then changing the atmosphere gas to contain a mixed gas stream containing at least ammonia and hydrogen The method includes the steps of nitriding heat treatment of the reaction product at 350 to 500 ° C., and wet-treating the obtained nitriding heat treatment into water. A method for producing a rare earth-iron-manganese-nitrogen based magnet powder according to any one of the above.   6. The method for producing a rare earth-iron-manganese-nitrogen based magnet powder according to claim 5, wherein the ammonia partial pressure in the mixed gas stream is 0.4 to 1.0.   6. The method for producing a rare earth-iron-manganese-nitrogen based magnet powder according to claim 5, wherein the time required for the nitriding heat treatment is 200 to 600 minutes.

Images