JP6578971B2 - Manufacturing method of iron-based alloy fine powder containing rare earth element, iron-based alloy fine powder containing rare earth element - Google Patents

Description

  The present invention relates to a method for producing an iron-based alloy fine powder containing a rare earth element having a stable and high coercive force and excellent weather resistance, and an iron-based alloy fine powder containing a rare earth element obtained by the production method. Relates to powder.

  Conventionally, ferrite magnets, alnico magnets, rare earth magnets, and the like have been used for various applications including motors. However, since these magnets are mainly manufactured by a sintering method, they are generally brittle and have a drawback that it is difficult to obtain a thin or complicated shape. In addition, since the shrinkage during sintering is as large as 15% to 20%, a product with high dimensional accuracy cannot be obtained, and there is a disadvantage that post-processing such as polishing is necessary to increase the accuracy. Yes.

  Bond magnets have been developed in recent years to solve the disadvantages of these sintering methods and to develop new applications. This bonded magnet is usually manufactured by filling a magnetic powder into a thermoplastic resin such as polyamide resin or polyphenylene sulfide resin as a binder.

  However, among these bonded magnets, in particular, in bonded magnets using iron-based alloy fine powders containing rare earth elements, such as rare earth-iron-nitrogen based magnetic powders, the occurrence of rust and magnetic properties in a high-temperature and high-humidity atmosphere. It is easy to cause the fall of. Therefore, for example, rusting is suppressed by forming a coating film such as a thermosetting resin on the surface of the molded body, or rusting is suppressed by coating the surface of the molded body with a phosphate-containing paint. (See Patent Document 1). However, since the magnetic powder constituting the compact is not coated, it is not satisfactory in terms of magnetic properties such as rusting and coercive force.

  In order to solve such problems, by adding phosphoric acid when pulverizing the iron-based alloy powder containing rare earth elements, the surface of each magnet powder and phosphoric acid is treated with phosphoric acid simultaneously with the pulverization. There has been proposed a method for producing rare earth-iron-nitrogen based magnet powder which is protected by a film formed by reaction and has improved weather resistance (see Patent Document 2). However, with this method, the magnetic properties of the magnet powder, particularly the coercive force and weather resistance, may vary between production lots. For this reason, a method for reducing variation by optimizing film formation and drying treatment with a phosphoric acid compound and controlling the composition of phosphorus, oxygen, and hydrogen that affect weather resistance within a predetermined range has been proposed (Patent Literature). 3).

  Under these circumstances, in recent years, bond magnets used for motorcycles, small motors for automobiles, and the like have been required to have stable magnetic characteristics due to the requirement of device reliability. However, the magnetic properties of conventional bonded magnets obtained from iron-based alloy fine powders containing rare earth elements are insufficient for use in these applications, and it is hoped to further reduce variations in coercive force and weather resistance. It is rare.

JP 2000-208321 A JP 2002-124406 A JP 2004-111515 A

  The present invention has been proposed in view of the above-described problems of the prior art, and includes a rare earth element that exhibits reduced high coercivity and excellent weather resistance with reduced variations in coercive force and weather resistance. A method for producing an iron-based alloy fine powder and an iron-based alloy fine powder containing the rare earth element are provided.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, it has been found that in the rare earth-iron-nitrogen alloy fine powder, hydrogen, which is an inevitable impurity, causes the variation in coercive force and weather resistance. And when pulverizing the alloy powder as a raw material in a solvent containing an organic solvent, phosphoric acid is added so that the newly fractured surface of the fine powder generated by pulverization is immediately treated, and the iron system containing a rare earth element to be heat-treated In the method for producing a fine alloy powder, the fine alloy powder having a phosphate film formed on the surface thereof is obtained by subjecting the fine alloy powder to a heat treatment at a predetermined temperature in an atmosphere containing oxygen at a specific oxygen partial pressure. The present inventors have found that the hydrogen content of the alloy fine powder is effectively reduced to stably exhibit high coercive force and excellent weather resistance, and the present invention has been completed. That is, the present invention provides the following.

  (1) In the first invention of the present invention, an iron-based alloy powder containing a rare earth element is pulverized in a solvent containing an organic solvent, a phosphoric acid compound is added during the pulverization, and the surface is coated with a phosphate film. A first step of obtaining a fine powder and a second step of subjecting the obtained fine powder to a heat treatment at a predetermined temperature. In the second step, the obtained iron-based alloy fine powder is obtained. Contains a rare earth element that is heat-treated at a temperature of 100 ° C. to 300 ° C. in an atmosphere containing oxygen having a partial pressure of 0.1 kPa to 5.0 kPa so that the hydrogen content is 0.2 mass% or less. It is a manufacturing method of iron-based alloy fine powder.

  (2) A second invention of the present invention is a method for producing an iron-based alloy fine powder containing a rare earth element, which is heat-treated in the first invention under the conditions of 0.5 hours or more and 20 hours or less.

  (3) According to a third aspect of the present invention, in the first or second aspect, in the first step, the phosphoric acid compound is added to the solvent before or during pulverization, and the iron containing a rare earth element is added. It is a manufacturing method of a system alloy fine powder.

  (4) A fourth invention of the present invention is an iron-based alloy fine powder containing a rare earth element coated with a phosphate film, wherein the hydrogen content (H) is 1/10 or less of the phosphorus content (P). And an iron-based alloy fine powder containing a rare earth element in which O / P, which is the ratio of oxygen content (O) to phosphorus content (P), is 5 or less.

(5) According to a fifth aspect of the present invention, in the fourth aspect, in the X-ray diffraction, the Th ₂ Zn ₁₇ type has a (113) diffraction line, the Th ₂ Ni ₁₇ type has a (112) diffraction line, and a TbCu ₇ type. Then, it is an iron-based alloy fine powder containing a rare earth element, in which the half-width B of the (002) diffraction line is smaller than the value of 0.25 / D50 obtained from the average particle diameter D50 (μm).

  According to the present invention, it is possible to efficiently produce an iron-based alloy fine powder containing a rare earth element, which shows a stable high coercive force and excellent weather resistance, with reduced variations in coercive force and weather resistance. .

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Ferrous alloy fine powder containing rare earth elements >>
The iron-based alloy fine powder containing a rare earth element according to the present embodiment is a pulverized product of a rare earth-transition metal-nitrogen based magnetic powder (hereinafter also referred to as “alloy powder”), and the surface thereof is a phosphate film. It is coated and has a specific elemental composition.

(1) Alloy powder The alloy powder before being coated with the phosphate coating has a Th ₂ Zn ₁₇ type, Th ₂ Ni ₁₇ type, or TbCu ₇ type crystal structure. These are intermetallic compounds having rhombohedral and hexagonal crystal structures. Examples of the Th ₂ Zn ₁₇ type alloy powder include Sm ₂ Fe ₁₇ N ₃ alloy and Nd ₂ Fe ₁₇ N _3. Is mentioned. Examples of the Th ₂ Ni ₁₇ type alloy powder include Gd ₂ Fe ₁₇ N _{3 and the} like. Examples of the TbCu ₇ type alloy powder include (Sm, Zr) (Fe, Co) ₁₀ N _{x and the} like.

  Examples of the rare earth element (R) include Sm, Nd, Pr, Y, La, Ce, and Gd. These may be used alone or as a mixture. Among them, Sm is particularly effective. Further, as the transition metal element (T), iron (Fe) is an essential component, and a part thereof may be substituted with Co. Specifically, the Curie temperature and corrosion resistance of the fine powder can be improved by substituting 20% by mass or less of Fe with Co. In the following, it is expressed as “rare earth-iron-nitrogen based magnetic powder” in view of the fact that Fe is an essential component as a transition metal.

  Alloy powders include C, Al, Si, Ca, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Re, and Os. , Ir, Pt, or Au. These include elements other than transition metals, but the iron-based alloy fine powder according to the present embodiment handles all of them in accordance with the transition metal element (T). In the alloy powder, these components are added at a ratio of 3% by mass or less, preferably 0.05% by mass to 0.5% by mass, so that a bonded magnet produced by using a fine powder which is a pulverized product of the alloy powder. Can further improve the weather resistance and heat resistance.

  These alloy powders can be produced, for example, by subjecting a rare earth-iron alloy powder obtained by a reduction diffusion method, a liquid quenching method, or an HDDR (Hydrogen Deposition Decomposition Recombination) method to a nitriding heat treatment.

(2) Iron-based alloy fine powder containing rare earth elements The iron-based alloy fine powder containing rare earth elements according to the present embodiment (hereinafter also simply referred to as “iron-based alloy fine powder” or “alloy fine powder”) The rare earth-iron-nitrogen based magnetic powder is pulverized to form a phosphate film on its surface, and each component constituting the entire magnetic powder including the phosphate film has a specific composition. Yes.

(Average particle size)
The average particle size of the iron-based alloy fine powder is, for example, about 1 μm to 10 μm.

(Composition of iron alloy fine powder)
Components of the iron-based alloy fine powder containing rare earth elements include rare earth elements (R) which are components of alloy powder, transition metal elements (T) containing iron, nitrogen (N), and components of the phosphate film. And phosphorus (P) and oxygen (O). In this iron-based alloy fine powder, there is hydrogen (H) as an impurity inevitably mixed in the manufacturing process, and it contains hydrogen in addition to the elements described above. As described above, an additive element such as Co may be further included as a component of the alloy powder, and a transition metal element (T) such as Zn, Cu, or Mn may be further included as a component of the phosphate film.

  These components are, for example, in an iron-based alloy fine powder, R is 20% by mass to 25% by mass, N is 2.1% by mass to 5.7% by mass, and P is 0.10% by mass to 2.0%. It has an elemental composition of mass%, O being 0.3 mass% to 6.0 mass%, and the balance being T. And in the iron-based alloy fine powder containing rare earth elements according to the present embodiment, as described above, the H content as an inevitable impurity is reduced to 1/10 or less of the P content. It is a feature.

  Specifically, regarding the content of R, if it is less than 20% by mass, the residual magnetization and coercive force of the fine powder may be reduced, and if it exceeds 25% by mass, the residual magnetization and weather resistance may be reduced. is there. Further, if the N content is less than 2.1% by mass or exceeds 5.7% by mass, the residual magnetization and coercive force of the fine powder may be reduced. The content of P, which is a component of the phosphate film, depends on the shape and particle size distribution (that is, the specific surface area) of the fine powder, but if it is less than 0.1% by mass, the weather resistance of the fine powder And the heat resistance may be inferior, and if it exceeds 2.0% by mass, the residual magnetization may be lowered.

  Further, the content of O also depends on the specific surface area of the fine powder, but if it is less than 0.3% by mass, a phosphate film on the surface of the fine powder is not sufficiently formed. In addition to being inferior, there is a risk of ignition when handled in air due to its high surface activity. On the other hand, if it exceeds 6.0% by mass, the residual magnetization may be lowered.

  The balance is the transition metal element (T) which is the main component of the fine powder. As a component of the phosphate film, Zn, Cu, Mn and the like may further be included. Therefore, as the transition metal element (T), in addition to Fe, Co, Zn, Cu, and Mn One containing at least one selected from the above can be said to be suitable.

  And in the iron-based alloy fine powder containing rare earth elements according to the present embodiment, the content of hydrogen (H) inevitably mixed is 1/10 or less of the content of P, preferably 1/20. It is as follows. As the P content due to the phosphate film increases, the hydrogen content also increases. The present inventor has found that hydrogen, which is an inevitable impurity, causes a variation in coercive force and weather resistance in an iron-based alloy fine powder containing a rare earth element. That is, when the H content in the alloy fine powder exceeds 1/10 of the P content, the weather resistance is lowered and the coercive force is also lowered. In addition, the weather resistance and coercive force vary. In the iron-based alloy fine powder according to the present embodiment, the content of H, which is an inevitable impurity, is 1/10 or less of the P content, so that there is no variation in coercive force and weather resistance, and it is stably high. Shows coercive force and excellent weather resistance.

In this iron-based alloy fine powder, if the heat treatment for reducing H diffused in the vicinity of the surface of the intermetallic compound which is the main phase is excessively performed, the alloy fine powder is oxidized and the residual magnetic flux density Br or The coercive force μ ₀ Hc decreases. Therefore, O / P which is a ratio of O content to P content is set to 5 or less. When O / P exceeds 5, it means that oxygen resulting from oxidation of the alloy fine powder is contained in addition to oxygen derived from the phosphate film.

Further, in the iron-based alloy fine powder containing rare earth elements according to the present embodiment, H diffused in the vicinity of the surface of the intermetallic compound which is the main phase is sufficiently reduced, so that the lattice constant reflecting the diffusion of H is obtained. Particularly, the portion where the lattice constant in the c-axis direction is increased is reduced, and in the X-ray diffraction of the iron-based alloy powder, the half-value width B is reduced in the diffraction line having an index corresponding to the c-plane. As the index, considering the presence or absence of adjacent diffraction lines and the diffraction intensity, (113) diffraction lines for Th ₂ Zn ₁₇ type, (112) diffraction lines for Th ₂ Ni ₁₇ type, and (002) for TbCu ₇ type. Use diffraction lines.

  The half-value width B (deg.) Of the diffraction line is affected by strain, defects, crystallite size, and the like introduced during pulverization. Therefore, when considered in relation to the average particle diameter D50 (μm) of the iron-based alloy fine powder, in the iron-based alloy fine powder according to the present embodiment, the half width B of the diffraction line in the X-ray diffraction is It is below the numerical value represented by 0.25 / D50. When the half-value width B exceeds 0.25 / D50, the weather resistance is lowered and the coercive force is also lowered, so that it is judged that removal of hydrogen diffused in the main phase intermetallic compound is not sufficient.

In calculating the half-value width B (deg.) Of a diffraction line in X-ray diffraction, the optical value of the X-ray diffractometer is used for the half-value width b (deg.) Obtained by removing the background from the measured profile. Using the half width b ₀ (deg.) Due to the system,
B = (b ² −b ₀ ² ) ^1/2
It is necessary to correct it. Here _{b 0} from X-ray diffraction profile of the Si powder is NIST640c standard sample (111), (220), (311), (400), the determined, from these values the half width of the (331) diffraction line This is a value obtained by applying 2θ corresponding to the diffraction line of the alloy fine powder to the approximate expression b (2θ) of the half width obtained by the least square method.

(Phosphate film)
As a component of the phosphate film coated on the surface of the alloy fine powder, for example, a rare earth phosphate such as iron phosphate or samarium phosphate, or a composite metal salt thereof is used. Among them, the main component is iron phosphate, and the iron / rare earth element ratio is preferably 8 or more, more preferably 9 or more, and further preferably 10 or more. Here, the ratio of iron / rare earth element is determined by measuring the area intensity of Fe and Sm spectra obtained by XPS (X-ray photoelectron spectroscopy) while Ar sputtering a magnetic powder sample (manufactured by VG Scientific, ESCALAB220i- XL) is multiplied by the sensitivity coefficient to obtain the Fe / Sm element ratio. If the iron / rare earth element ratio is preferably 8 or more, water can be blocked to some extent, and the bond strength with the resin binder can be increased, thereby improving the formability of the bond magnet. If the iron / rare earth element ratio is less than 8, these effects may not be sufficiently obtained.

  The thickness of the phosphate film is not particularly limited, but is preferably about 2 nm to 50 nm on average, and such a phosphate film is uniformly coated on the surface of the fine powder. When the thickness of the phosphate film is less than 2 nm, a poorly coated portion tends to occur on the surface of the fine powder, and the weather resistance may be insufficient. On the other hand, when the thickness of the phosphate film exceeds 50 nm, the magnetic properties may be deteriorated. Note that “the surface of the fine powder is uniformly coated” means that the phosphate coating covers the fine powder surface at a rate of preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. It means that

(Specific surface area)
The iron-based alloy fine powder containing rare earth elements according to the present embodiment is not particularly limited, but preferably has a volume-based specific surface area of 7 m ² / cm ³ or less. When the specific surface area exceeds 7 m ² / cm ³ , the weather resistance may be lowered.

≪2. Manufacturing method of iron-based alloy fine powder containing rare earth elements >>
Next, a method for producing the iron alloy fine powder containing the rare earth element described above will be described. In the method for producing an iron-based alloy fine powder containing rare earth elements according to the present embodiment, first, an alloy powder as a raw material is pulverized in the presence of a phosphoric acid compound, and a phosphate is formed on the surface of the alloy fine powder generated by the pulverization. And a second step of fixing the surface phosphate film by drying and heating the fine alloy powder obtained by pulverization.

  As rare earth-iron-nitrogen alloy fine powder (iron-based alloy fine powder containing rare earth elements) used for bonded magnets, there is no variation in coercive force and weather resistance, and it has a stable and high coercive force. In particular, those showing excellent weather resistance are required. According to the inventor's research, it has been found that the cause of variation in the coercive force and the weather resistance in the alloy fine powder is hydrogen (H) which is an inevitable impurity.

  In the method for producing an iron-based alloy fine powder, as a first step, phosphoric acid is added when pulverizing the alloy powder as a raw material, and a phosphate film is formed on the surface of the pulverized alloy fine powder. Thereby, the oxidation of the alloy fine powder after grinding can be prevented. However, it has been found that hydrogen generated by the reaction of phosphoric acid added during the pulverization with the alloy fine powder enters the alloy from the surface of the obtained alloy fine powder.

Since hydrogen has a small atomic radius, it easily diffuses near the surface of the alloy fine powder, and the main phase of the alloy fine powder is an R ₂ Fe ₁₇ N ₃ phase or an RFe ₇ N _x phase (R is a rare earth element). Increase the lattice constant. Changes in the lattice constant affect the magnitude of the magnetocrystalline anisotropy, and in many cases, increasing the lattice constant reduces the magnetic anisotropy, and that part becomes the bud of the reverse magnetic domain and reduces the coercive force. Inferred.

  Therefore, hydrogen diffused on the surface of the alloy fine powder and in the vicinity of the grain boundary may cause variations in coercive force and weather resistance, and removal of the hydrogen can provide stable coercive force and weather resistance. It is necessary to realize. For example, in the heat treatment disclosed in Patent Document 3 under a temperature condition of 100 ° C. to 300 ° C. in an inert gas or in a vacuum, the amount of hydrogen remaining in the alloy fine powder varies, and the heat treatment is stable. It was difficult to produce industrially.

  Therefore, in the manufacturing method according to the present embodiment, the alloy fine powder is used as the second step for the alloy fine powder obtained by forming the phosphate film on the surface in the first step. In an atmosphere containing oxygen having a partial pressure of 0.1 kPa or more and 5.0 kPa or less at the time of or after drying the slurry containing the alloy fine powder so that the hydrogen (H) content of The heat treatment is performed under a temperature condition of 100 ° C. or higher and 300 ° C. or lower.

  By performing such heat treatment, hydrogen contained in the alloy fine powder can be effectively removed, the H content is 1/10 or less of the P content, and the O content and the P content are An iron-based alloy fine powder having an O / P ratio of 5 or less can be obtained. As another index, the iron alloy fine powder has a half-width B of the diffraction line in the X-ray diffraction of the alloy fine powder smaller than the value of 0.25 / D50 calculated from the average particle diameter D50. . Such an iron-based alloy fine powder has little variation in coercive force and weather resistance, stably has a high coercive force, and stably exhibits excellent weather resistance. Hereinafter, each step will be specifically described.

(1) First Step In the first step, the alloy powder as a raw material is pulverized in an organic solvent to which a phosphoric acid compound is added, and the surface of the fine powder generated by the pulverization is coated with a phosphate film.

  Conventionally, the surface of the alloy powder is coated with a phosphate coating, but after the grinding of the alloy powder, a treatment agent such as phosphate is added, so the ground alloy powder is They are aggregated with each other by magnetic force, and at least part of the contact surface of the alloy powder is not covered with the phosphate film.

  Therefore, in the present embodiment, a phosphoric acid compound is added before or during pulverization of the magnetic powder, and the newly broken surface of the fine powder generated by pulverization is immediately treated with the phosphoric acid compound to form a phosphate film. I am doing so.

(Method of adding phosphoric acid compound)
The method for adding the phosphoric acid compound is not particularly limited. For example, when the alloy powder is pulverized by a pulverizer such as a medium stirring mill, a method of adding the phosphoric acid compound to an organic solvent used as a solvent for charging the alloy powder is exemplified. be able to. At this time, the addition amount of the phosphoric acid compound may be finally a desired phosphoric acid concentration, and may be added all at once before the start of pulverization, but gradually, the phosphoric acid concentration in the solvent becomes constant. It is more preferable to add to.

(Phosphoric acid compound)
The phosphoric acid compound is not particularly limited as long as it can form a phosphate film on the surface of the alloy fine powder. Examples thereof include phosphoric acid compounds such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, linear polyphosphoric acid, and cyclic metaphosphoric acid.

  In addition, as the phosphoric acid compound, ammonium phosphate, ammonium magnesium phosphate, etc., and zinc phosphate-based, scholzeite, phosphophyllite, hopite, etc. that form a film of hopite, phosphoferrite, etc. on the surface of the alloy fine powder Uses metal phosphate compounds such as zinc phosphates that form films, manganese phosphates that form films such as manganese huriolite, iron huriolites, iron phosphates that form films such as strenite and hematite can do.

  Among these phosphoric acid compounds, it is particularly preferable to use orthophosphoric acid. This is because orthophosphoric acid is highly reactive with rare earth metals and iron, and easily forms a phosphate film on the surface of the alloy fine powder.

  These phosphoric acid compounds may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, you may use combining the phosphoric acid type compound and metal phosphoric acid type compound which were mentioned above, In that case, it is preferable to use a phosphoric acid type compound as 1 to 3 times the density | concentration of a metal phosphoric acid type compound. Usually, these phosphoric acid compounds are mixed with chelating agents, neutralizing agents and the like and used as treatment agents.

(Addition amount of phosphoric acid compound)
The addition amount of the phosphoric acid compound is unclear because it is related to the particle size, specific surface area, etc. of the fine alloy powder after pulverization. For example, 0.05 mol / kg or more and 2.0 mol relative to the pulverized alloy powder / Kg is preferable, 0.1 mol / kg to 1.5 mol / kg is more preferable, and 0.15 mol / kg to 0.6 mol / kg is more preferable.

  When the addition amount of the phosphoric acid compound is less than 0.05 mol / kg, the surface treatment for the alloy fine powder is not sufficiently performed, so that the weather resistance may not be sufficiently improved. In addition, when handled in the atmosphere, there is a possibility that the magnetic properties will be extremely lowered due to oxidation and heat generation. On the other hand, when the addition amount of the phosphoric acid compound is 2.0 mol / kg or more, there is a possibility that the reaction with the alloy fine powder occurs vigorously and dissolves.

(Organic solvent)
The organic solvent is not particularly limited, and for example, alcohols such as ethanol and isopropyl alcohol, ketones, lower hydrocarbons, aromatics, or mixtures thereof are used. Among these, it is particularly preferable to use alcohols.

(Crushing and film formation)
In the present embodiment, the pulverization of the alloy powder in the organic solvent is performed by adding a phosphoric acid compound to the organic solvent before or during the pulverization. That is, the phosphoric acid compound is added when the raw alloy powder is pulverized. As a result, even if a new surface occurs in the aggregated particles of the alloy fine powder generated by grinding the alloy powder, the new surface and the phosphoric acid compound in the solvent react instantaneously to form a phosphate film on the particle surface. become. In addition, even when the alloy fine powder obtained by pulverization subsequently aggregates due to the magnetic force or shearing by the medium, a phosphate film is already formed on the contact surface, so that corrosion does not occur due to crushing. .

  By such pulverization treatment, an alloy powder having an average particle size of, for example, 10 μm or more also forms a thin phosphate film on the surface in a short time as pulverization proceeds.

  In the pulverization treatment of the alloy powder in the organic solvent, it is preferable to use a medium stirring mill such as a bead mill capable of wet pulverization.

Here, in the rare earth element-iron-nitrogen based alloy powder having a Th ₂ Zn ₁₇ type crystal structure, a phosphate of a constituent element based on the type of the phosphoric acid compound used can be generated on the surface of the alloy fine powder generated by pulverization. However, since rare earth elements are remarkably base as compared with iron, depending on the addition amount of the phosphoric acid compound and the grinding conditions, the rare earth elements may elute preferentially and form rare earth elements and phosphates.

  Even in this case, although there is no problem in the heat resistance of the obtained alloy fine powder, from the viewpoint of weather resistance, it is preferable that the content of iron phosphate in the phosphate film is large. Iron phosphate is superior in weather resistance compared to rare earth element phosphates, and under conditions where the rare earth element elutes preferentially, the Fe concentration on the surface of the alloy fine powder becomes high and the magnetic properties are low. It is possible to change.

  For this reason, it is preferable to adjust so that the element ratio (Fe / rare earth element) of Fe and rare earth elements contained in the phosphate film is 8 or more based on the addition amount of the phosphoric acid compound, the mixing time, and the like. Moreover, it is preferable to adjust so that it may become 2-50 nm on average as thickness of the phosphate membrane | film | coat which protects the surface of alloy fine powder.

  In addition, the surface of the rare earth element-iron-nitrogen alloy powder used as a raw material is subjected to zinc treatment to chemically coat zinc, thereby reducing the soft magnetic phase and defects on the surface of the alloy fine powder. I can leave. Thereby, a phosphate film can be easily formed on the surface of the alloy fine powder, which is excellent not only in weather resistance but also in heat resistance, and is particularly suitable.

  In addition, the above-described phosphate coating is formed on the surface and, if necessary, one or more selected from various coupling agents such as silane, aluminate, titanate, abietic acid compounds, etc. You may make it coat | cover the film | membrane consisting of.

(2) Second Step In the second step, the slurry containing the alloy fine powder having the phosphate film formed on the surface obtained in the first step is subjected to a heat treatment at a predetermined temperature condition. Apply. By the heat treatment in the second step, the phosphate coating coated on the surface is stabilized, and an iron-based alloy fine powder containing a rare earth element used for a bond magnet or the like is obtained.

  At this time, in this embodiment mode, heat treatment is performed in a temperature range of 100 ° C. or higher and 300 ° C. or lower in an atmosphere containing oxygen controlled to have a partial pressure in a predetermined range. The heat treatment time is preferably 0.5 hours to 20 hours.

  Since this heat treatment is performed in an atmosphere containing oxygen as the heating atmosphere, a reaction occurs in which oxygen in the atmosphere becomes water by hydrogen contained in the alloy fine powder. That is, hydrogen contained in the alloy fine powder can be effectively removed by such heat treatment in an atmosphere containing oxygen.

  Such heat treatment can be performed at any stage of drying the slurry containing the alloy fine powder or after the liquid is evaporated (after drying), but the liquid is evaporated. The latter is preferable because the contact probability between the surface of the alloy fine powder and the atmosphere containing oxygen is increased, and hydrogen in the alloy fine powder can be removed more efficiently and more effectively.

  As described above, in this heat treatment, hydrogen contained in the alloy fine powder is removed by reacting hydrogen contained in the alloy fine powder with oxygen in the atmosphere. In this case, it is necessary that the oxygen that reacts with hydrogen be present at a ratio of at least a reaction equivalent (0.5 mol of oxygen to 1 mol of hydrogen) with respect to the amount of hydrogen removed from the alloy fine powder. However, since oxygen has a flame-supporting property, when introduced as a heat treatment atmosphere gas, while controlling the flow rate to an inert gas such as nitrogen, argon, helium, etc. to ensure safety and uniformity of treatment, It is preferable to add. Further, oxygen may be introduced while controlling under reduced pressure.

(Oxygen partial pressure)
Here, conventionally, the film formation treatment with phosphoric acid has been a treatment to prevent the surface oxidation of the alloy fine powder, so that the presence of oxygen in the atmosphere in the heat treatment is considered to be an adverse effect of the surface oxidation prevention. It was. However, contrary to expectations, the inventors have found that the hydrogen removal effect by a small amount of oxygen is greater than the adverse effect of surface oxidation caused by the presence of oxygen in the heat treatment atmosphere.

  In the manufacturing method according to the present embodiment, in the heat treatment in the second step, the oxygen partial pressure in the atmosphere containing oxygen is set to 0.1 kPa or more and 5 kPa or less.

  When the oxygen partial pressure in the atmosphere exceeds 5 kPa, the effect of simultaneous oxidation of the alloy fine powder becomes strong, and the coercive force and residual magnetic flux density of the alloy fine powder after heating are reduced. On the other hand, if the oxygen partial pressure in the atmosphere is less than 0.1 kPa, the effect of removing hydrogen contained in the alloy fine powder cannot be sufficiently obtained even if oxygen far exceeding the reaction equivalent is supplied.

(Heating temperature)
The temperature of the heat treatment (heating temperature) in an atmosphere containing oxygen is set to a range of 100 ° C. to 300 ° C. Moreover, Preferably, it is set as the range of 100 to 200 degreeC.

  When heat treatment is performed under a temperature condition of less than 100 ° C., the reaction between oxygen and hydrogen does not proceed sufficiently, the hydrogen content of the obtained alloy fine powder is not reduced, the coercive force is not improved, and the variation becomes large. . On the other hand, when the heat treatment is performed under a temperature condition exceeding 300 ° C., there is a problem that the coercive force of the obtained alloy fine powder is lowered because the alloy fine powder is strongly damaged by heat.

(Heat treatment time)
The time required for the heat treatment varies depending on the treatment device, treatment amount, oxygen supply amount, heating atmosphere, heating temperature, and the like, and is not particularly limited, but may be 0.5 hours or more, and may be 1 hour to 20 hours. In particular, it is preferable to adjust to be 2 hours to 10 hours.

  Of course, the total amount of oxygen supplied must be at least 1 equivalent to the amount required for reaction with the hydrogen to be removed from the alloy fines. When less than 1 equivalent, hydrogen remains in the alloy fine powder. Since 100% of the supplied oxygen generally does not contribute to the reaction, the supply amount of several equivalents to several tens equivalents depending on the oxygen concentration, the supply flow rate, the stirring state of the alloy fine powder in the processing apparatus, etc. It is also necessary to supply with. However, even when the supply equivalent of oxygen is large, if the treatment time is less than 0.5 hour, the reaction with hydrogen does not proceed sufficiently and the hydrogen content cannot be reduced. On the other hand, it is possible to reduce the oxygen supply amount per unit time and perform the treatment over a long time, but a treatment time exceeding 20 hours is not preferable in terms of economy.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(1) Component Sm—Fe—N alloy powder (manufactured by Sumitomo Metal Mining Co., Ltd.) having a Th ₂ Zn ₁₇ type crystal structure was used as an iron alloy powder containing rare earth elements used as a raw material. The average particle size of the Sm—Fe—N alloy powder is 20 μm, and the composition is such that Sm is 23.1% by mass to 24.5% by mass (analyzed by ICP emission spectrometry), and N is 3.2% by mass. ~ 3.7 mass% (inert gas melting-analyzed by thermal conductivity detection method), the balance being Fe, but Ca as an impurity is 0.006 mass% to 0.015 mass% (EPMA) in the main phase (Analyzed by quantitative analysis) and hydrogen is contained in an amount of 0.002 to 0.008 mass% (analyzed by inert gas melting-infrared absorption method).

  As the phosphoric acid compound, an 85% orthophosphoric acid aqueous solution (trade name: “phosphoric acid”, manufactured by Kanto Chemical Co., Inc.) was used.

(2) Test / Evaluation Method The composition of the obtained iron-based alloy fine powder containing rare earth elements was analyzed for phosphorus by ICP emission analysis, and for oxygen and hydrogen by inert gas melting-infrared absorption.

  Further, the 50% particle diameter measured with a laser diffraction particle size distribution analyzer (manufactured by Nippon Laser Co., Ltd., HELOS & RODOS) was used as the average particle diameter (D50) of the sample.

Further, regarding the X-ray diffraction of the alloy fine powder, an acceleration voltage of 40 kV and a current of 40 mA were used with a Cu target, and 2θ was 2 min. / Deg. Scanned with and measured. Further, the half-value width B of the diffraction line is obtained by substituting the half-value width b (deg.) Obtained by removing the background from the measured profile by the half-value width b ₀ (deg.) Resulting from the optical system of the X-ray diffraction apparatus.
B = (b ² −b ₀ ² ) ^1/2
And corrected. Incidentally, _{b 0} is the X-ray diffraction profile of the Si powder is NIST640c standard sample (111), (220), (311), (400), the determined, from these values the half width of the (331) diffraction line This is a value obtained by applying 2θ corresponding to the (113) diffraction line for the Th ₂ Zn ₁₇ type and (002) diffraction line for the TbCu ₇ type to the approximate expression b (2θ) of the half width obtained by the least square method. .

The residual magnetic flux density Br and coercive force μ ₀ Hc of a sample of an iron-based alloy fine powder containing rare earth elements were measured at room temperature using a vibrating sample magnetometer according to the Bond Magnet Test Method Guidebook BMG-2002 of the Japan Bond Magnet Industry Association. . Here, “μ ₀ ” is a vacuum magnetic permeability, and the density of the alloy fine powder was converted to 7.67 g / cm ³ .

[Examples 1 to 3, Conventional Example 1, Comparative Examples 1 to 4]
Using a bead mill, 0.5 kg of an iron-based alloy powder containing a rare earth element was pulverized in 1 kg of isopropyl alcohol until the average particle size became 2.1 μm to prepare an iron-based alloy fine powder containing a rare earth element. In addition, 11.5 g of 85% orthophosphoric acid aqueous solution was added to isopropyl alcohol before pulverization.

  After the pulverization, the slurry was filtered with Nutsche, the cake remaining on the filter cloth was put into a mixer, the temperature was raised while reducing the pressure with a vacuum pump, dried at 130 ° C. for 2 hours and cooled. The iron-based alloy fine powder thus obtained was used as the iron-based alloy fine powder of Conventional Example 1.

The residual magnetic flux density Br of the iron-based alloy fine powder of Conventional Example 1 was 1.35 T, and the coercive force μ ₀ Hc was 1.10 T. As a result of composition analysis, phosphorus was 0.51% by mass, oxygen was 1.7% by mass, and hydrogen was 0.064% by mass. Furthermore, the half width B of the (113) diffraction line by X-ray diffraction measurement is 0.125 deg. was.

Next, this alloy fine powder is again put in the mixer and heated under the conditions shown in Table 1 below while flowing air 30 cm ³ / min and N ₂ gas 2.0 L / min (oxygen partial pressure 0.3 kPa). The iron-based alloy fine powder containing the rare earth elements of Examples 1 to 3 and Comparative Examples 1 to 4 was obtained. In Comparative Example 4, heating was performed only with an N ₂ gas flow without mixing air.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown. “P”, “O”, and “H” indicate the contents of phosphorus, oxygen, and hydrogen, respectively (the same applies to the following).

[Examples 4 to 6, Comparative Example 5]
The fine powder of Conventional Example 1 was put in a mixer and subjected to heat treatment under the conditions shown in Table 1 below while flowing air 30 cm ³ / min and N ₂ gas 250 cm ³ / min (oxygen partial pressure 2 kPa). Iron-based alloy fine powders containing rare earth elements 4 to 6 and Comparative Example 5 were obtained.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 7]
In the same manner as in Conventional Example 1, iron-based alloy powder containing rare earth elements was pulverized and filtered. The cake remaining on the filter cloth was put into a mixer, heated while reducing pressure with a vacuum pump, and kept at 135 ° C. for 1 hour. Thereafter, air was introduced while adjusting the flow rate so that the internal pressure became 2 kPa (oxygen partial pressure 0.4 kPa) while continuing to reduce pressure without cooling, and further cooled for 2 hours.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 8]
In the same manner as in Conventional Example 1, iron-based alloy powder containing rare earth elements was pulverized and filtered. The cake remaining on the filter cloth was put into a mixer, heated while reducing pressure with a vacuum pump, and kept at 135 ° C. for 1 hour. Thereafter, the inside of the mixer is returned to atmospheric pressure with a mixed gas of N ₂ gas and air (oxygen partial pressure 2 kPa) without cooling, and the exhaust valve of the mixer is opened, and N ₂ gas 8 L / min, air 1 L / min The mixture was further cooled for 2 hours while being flown (oxygen partial pressure 2 kPa).

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Comparative Example 6]
The heat treatment was performed under the same conditions as in Example 8 except that the air flow rate was 3 L / min (oxygen partial pressure 5.5 kPa). During the heat treatment it was observed that the sample temperature rose to 147 ° C and then returned to 135 ° C.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 9, Conventional Example 2]
Using a bead mill, 0.5 kg of an iron-based alloy powder containing a rare earth element was pulverized in 1 kg of isopropyl alcohol until the average particle size became 2.1 μm to prepare an iron-based alloy fine powder containing a rare earth element. In addition, 34.6 g of 85% orthophosphoric acid aqueous solution was added to isopropyl alcohol before pulverization.

  After the pulverization, the slurry was filtered with Nutsche, the cake remaining on the filter cloth was put into a mixer, the temperature was raised while reducing the pressure with a vacuum pump, dried at 130 ° C. for 2 hours and cooled. The fine powder thus obtained was used as the fine powder of Conventional Example 2.

Next, the alloy fine powder of Conventional Example 2 is put in a mixer, and heat treatment is performed at 135 ° C. for 8 hours while flowing air 600 cm ³ / min and N ₂ gas 2.0 L / min (oxygen partial pressure 5 kPa). gave. During the heat treatment, condensation was observed near the mixer exhaust.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 10, Conventional Example 3]
Using a bead mill, 0.5 kg of an iron-based alloy powder containing a rare earth element was pulverized in 1 kg of isopropyl alcohol until the average particle size became 1.5 μm to prepare an iron-based alloy fine powder containing a rare earth element. In addition, 23.1 g of 85% orthophosphoric acid aqueous solution was added to isopropyl alcohol before pulverization.

  After the pulverization, the slurry was filtered with Nutsche, the cake remaining on the filter cloth was put into a mixer, the temperature was raised while reducing the pressure with a vacuum pump, dried at 130 ° C. for 2 hours and cooled. The fine powder thus obtained was used as the fine powder of Conventional Example 3.

Next, the alloy fine powder of Conventional Example 3 is put in a mixer, and heat treatment is performed at 135 ° C. for 2 hours while flowing air of 500 cm ³ / min and N ₂ gas of 4.0 L / min (oxygen partial pressure of 2 kPa). gave. During the heat treatment, condensation was observed near the mixer exhaust.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 11, Conventional Example 4]
Using a bead mill, 0.5 kg of an iron-based alloy powder containing a rare earth element was pulverized in 1 kg of isopropyl alcohol until the average particle size became 7.4 μm to prepare an iron-based alloy fine powder containing a rare earth element. In addition, 23.1 g of 85% orthophosphoric acid aqueous solution was added to isopropyl alcohol before pulverization.

  After completion of the pulverization, the slurry was filtered with Nutsche, the cake remaining on the filter cloth was put into a mixer, the temperature was raised while reducing the pressure with a vacuum pump, dried at 140 ° C. for 1 hour and cooled. The fine powder thus obtained was used as the fine powder of Conventional Example 4.

  Next, the alloy fine powder of Conventional Example 4 is put in a mixer, and the temperature is raised to 145 ° C. while reducing the pressure, and the internal pressure of the air is 1 kPa (oxygen partial pressure 0.2 kPa) while continuing the reduced pressure. The flow rate was adjusted and introduced, and further cooled for 2 hours.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

[Example 12, Conventional Example 5]
A bead mill using 0.5 kg of TbCu ₇ type crystal structure (Sm _0.75 Zr _0.25 ) (Fe _0.7 Co _0.3 ) ₁₀ N _x alloy powder produced by a liquid quenching method as a raw material Was then pulverized in 1 kg of isopropyl alcohol until the average particle size became 9.2 μm to prepare an iron-based alloy fine powder containing a rare earth element. In addition, 4.0 g of 85% orthophosphoric acid aqueous solution was added to isopropyl alcohol before pulverization.

  After completion of the pulverization, the slurry was filtered with Nutsche, the cake remaining on the filter cloth was put into a mixer, the temperature was raised while reducing the pressure with a vacuum pump, and the mixture was dried at 145 ° C. for 1 hour and cooled. The fine powder thus obtained was used as the iron-based alloy fine powder of Conventional Example 5.

  Next, the alloy fine powder of Conventional Example 5 is put in a mixer, heated to 150 ° C. while reducing the pressure, and the air is kept at 1 kPa (oxygen partial pressure 0.2 kPa) while continuing the reduced pressure. The flow rate was adjusted and introduced, and the mixture was further cooled for 1 hour.

Table 2 below shows compositional analysis values of residual magnetic flux density Br and coercive force μ ₀ Hc, phosphorus (P), oxygen (O), and hydrogen (H) of the iron-based alloy fine powder containing rare earth elements recovered after cooling. The average particle diameter D50 of the alloy fine powder, (113) half-value width B of the diffraction line, “HP / 10”, “O / P”, and “B-0.25 / D50” are shown.

  In addition, after embedding each alloy fine powder obtained in Examples 1-12, Conventional Examples 1-5, and Comparative Examples 1-6 in a resin and performing FIB processing to obtain a thin piece, the transmission electron microscope (TEM) was used. When the thickness of the phosphate coating was observed, it had a thickness of 4 nm to 10 nm in any case, and it was confirmed that it was coated without a defect.

Examples 1 to 3 are examples in which the oxygen partial pressure in the air was adjusted to 0.3 kPa, and compared with the conventional example 1 in which only drying under reduced pressure was performed and heat treatment only with N ₂ gas without introducing air. The coercive force μ ₀ Hc of the alloy fine powder obtained in Example 4 was 1.10T, but improved to 1.19T to 1.21T. Also, the H analysis value was less than 1/10 of the P analysis value, and the value of “H−P / 10” was negative. Furthermore, “O / P”, which is the ratio between the O analysis value and the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D25 obtained from D50, and the value of “B−0.25 / D50” was negative.

  On the other hand, in the case of Conventional Example 1 in which heat treatment is not performed or when air is used, the heating temperature is lower than 100 ° C. (Comparative Example 1) or the holding time is shorter than 0.5 hours (Comparative Example) 3) In the case of a nitrogen atmosphere containing no oxygen as the heating atmosphere (Comparative Example 4), the coercive force is not improved because hydrogen is not reduced, and “HP / 10”, “B— The value of “0.25 / D50” was found to be positive. Further, as shown in the result of Comparative Example 2, when the heating temperature exceeds 300 ° C., the H analysis value becomes low, and the values of “HP / 10” and “B-0.25 / D50” are negative. However, “O / P”, which is the ratio of the O analysis value to the P analysis value, was 12.2 and exceeded 5, and it was found that the fine alloy powder was oxidized and the coercive force was greatly deteriorated.

Examples 4 to 6 are examples in which the oxygen partial pressure was adjusted to 2 kPa and heat treated, and by introducing oxygen, the coercive force μ ₀ Hc was improved to 1.16 T to 1.23 T, and the H analysis value was P It was less than 1/10 of the analytical value. Furthermore, “O / P”, which is the ratio between the O analysis value and the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

On the other hand, as shown in the result of Comparative Example 5, when the heating time exceeds 20 hours, the coercive force μ ₀ Hc is 1.20 T, which is improved from the conventional example, and the H analysis value is also reduced. Although the values of “P / 10” and “B-0.25 / D50” were negative, the ratio of the O analysis value to the P analysis value “O / P” was 6.6, exceeding 5, The residual magnetic flux density Br decreased with the lapse of time, and the coercive force μ ₀ Hc was almost saturated after 8 to 16 hours of heat treatment.

Example 7 is an example of heat treatment under reduced pressure while flowing air so that the oxygen partial pressure becomes 0.4 kPa, and the coercive force μ ₀ Hc of the alloy fine powder obtained in Conventional Example 1 without air flow is 1. Compared to .10T, the air flow with reduced pressure also improved to 1.26T. The H analysis value was also less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio of the O analysis value to the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

Example 8 is an example of heat treatment while flowing N ₂ gas and air at an oxygen partial pressure of 2 kPa. As in Example 7, the coercive force μ ₀ Hc of the alloy fine powder obtained in Conventional Example 1 is Compared to 1.10T, it improved to 1.25T. The H analysis value was also less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio of the O analysis value to the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

On the other hand, in Comparative Example 6 in which the oxygen partial pressure exceeds 5 kPa, a large heat generation that seems to be oxidation was observed, and the coercive force μ ₀ Hc decreased to 1.01 T. In addition, the H analysis value decreased, and the values of “HP / 10” and “B-0.25 / D50” were negative, but the ratio of the O analysis value to the P analysis value was “O / P”. Was 7.6 and exceeded 5, indicating that the oxidation was supported.

Example 9 is an example in which the oxygen partial pressure was adjusted to 5 kPa and heat-treated, and its coercive force μ ₀ Hc was significantly improved to 1.20 T compared to Conventional Example 2 only under reduced pressure drying, and the H analysis value Was less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio of the O analysis value to the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

Example 10 is an example in which the average particle diameter D50 of the fine powder was 1.5 μm and the oxygen partial pressure in the air was adjusted to 2 kPa, and the alloy fine powder obtained in Conventional Example 3 only under reduced pressure drying was used. The coercive force μ ₀ Hc was 1.37T, but was improved to 1.52T. The H analysis value was also less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio between the O analysis value and the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

Example 11 is an example in which the average particle diameter D50 of the fine powder was 7.4 μm and heat treatment was performed under reduced pressure while flowing air so that the oxygen partial pressure was 0.2 kPa. The coercive force μ ₀ Hc of the obtained alloy fine powder was 0.28T, but improved to 0.32T. The H analysis value was also less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio between the O analysis value and the P analysis value, was 5 or less. In addition, the half width B of the (113) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

Example 12 is an (Sm _0.75 Zr _0.25 ) (Fe _0.7 Co _0.3 ) ₁₀ N _x alloy powder as an iron-based alloy fine powder containing a rare earth element having a TbCu ₇ type crystal structure. In this example, the average particle diameter D50 is 9.2 μm, and heat treatment is performed under reduced pressure while flowing air so that the oxygen partial pressure becomes 0.2 kPa. The coercive force μ ₀ Hc of the alloy fine powder was 1.03T, but improved to 1.15T. The H analysis value was also less than 1/10 of the P analysis value. Furthermore, “O / P”, which is the ratio between the O analysis value and the P analysis value, was 5 or less. In addition, the half width B of the (002) diffraction line in X-ray diffraction was less than 0.25 / D50 determined from D50, and the value of “B−0.25 / D50” was negative.

Here, iron-based alloy fine powders containing rare earth elements were prepared 10 times each under the conditions of Conventional Example 1 and Example 8. Table 3 below shows the average value and standard deviation σ of the coercive force μ ₀ Hc (0) immediately after the production of the obtained alloy fine powder. Further, 80 ° C. These alloy fine powder in the air, to evaluate the coercive force _μ 0 Hc (300) after leaving for 300 hours in an environment of 90% RH, as an index of weather resistance, mu ₀ Hc (300) And the ratio “Hc (300) / Hc (0)” of μ ₀ Hc (0) was obtained. Table 3 below also shows the average value of the ratio and the standard deviation σ.

As shown in Table 3, in the alloy fine powder produced under the conditions of Conventional Example 1, the variation σ between the coercive force μ ₀ Hc (0) immediately after production and the weather resistance index Hc (300) / Hc (0) is Whereas they were 0.034T and 0.014 (1.4%), respectively, in the alloy fine powder produced under the conditions of Example 8, the respective variations σ were 0.012T and 0.005 (0 .5%). Moreover, it turns out that the average value of each is excellent in the alloy fine powder manufactured on the conditions of Example 8. FIG.

Claims (3)

A first step of pulverizing an iron-based alloy powder containing a rare earth element in a solvent containing an organic solvent, adding a phosphoric acid compound during the pulverization, and obtaining a fine powder having a surface coated with a phosphate film;
A second step of subjecting the obtained fine powder to a heat treatment at a predetermined temperature,
In the second step,
Temperature conditions of 100 ° C. or more and 300 ° C. or less in an atmosphere containing oxygen having a partial pressure of 0.1 kPa or more and 5.0 kPa or less so that the hydrogen content of the obtained iron-based alloy fine powder is 0.2% by mass or less. The method for producing a ferrous alloy fine powder containing a rare earth element , wherein the heat treatment is performed at 0.5 to 20 hours . In the first step,
During grinding before or grinding method for producing a powder ferrous alloy powder containing a rare earth element according to claim 1, adding the phosphoric acid compound in the solvent. An iron-based alloy fine powder containing a rare earth element coated with a phosphate film,
The hydrogen content (H) is 1/10 or less of the phosphorus content (P),
The ratio Der O / P is 5 or less which is the oxygen content and (O) phosphorus content (P) is,
In the X-ray diffraction, the half-width B (deg.) Of the (113) diffraction line for the Th ₂ Zn ₁₇ type, the (112) diffraction line for the Th ₂ Ni ₁₇ type, and the (002) diffraction line for the TbCu ₇ type is the average grain size. An iron-based alloy fine powder containing a rare earth element smaller than a value of 0.25 / D50 obtained from a diameter D50 (μm) .