WO2011043158A1 - 希土類磁石材およびその製造方法 - Google Patents
希土類磁石材およびその製造方法 Download PDFInfo
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- WO2011043158A1 WO2011043158A1 PCT/JP2010/065660 JP2010065660W WO2011043158A1 WO 2011043158 A1 WO2011043158 A1 WO 2011043158A1 JP 2010065660 W JP2010065660 W JP 2010065660W WO 2011043158 A1 WO2011043158 A1 WO 2011043158A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
- C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
Definitions
- the present invention relates to a rare earth magnet material from which various rare earth permanent magnets having excellent magnetic properties and corrosion resistance can be obtained, and a method for producing the same.
- Rare earth magnets particularly permanent magnets typified by Nd—Fe—B magnets exhibit very high magnetic properties. Use of this rare earth magnet makes it possible to reduce the size, increase the output, increase the density, and reduce the environmental load of electromagnetic devices and electric motors. Yes. However, for that purpose, the excellent magnetic properties of rare earth magnets are required to be stably demonstrated over a long period even in a severe environment. Therefore, research and development are being actively conducted to increase the corrosion resistance (reduction resistance) and coercive force while maintaining or improving the high residual magnetic flux density of rare earth magnets. Descriptions related to these are disclosed in the following documents, for example.
- an Nd—B—Fe-based rare earth sintered magnet is subjected to a fluorination treatment and a heat treatment at 400 to 500 ° C., and a surface layer of about 5 to 10 ⁇ m made of an NdF 3 compound and / or an NdOF compound.
- a fluorination treatment and a heat treatment at 400 to 500 ° C.
- a surface layer of about 5 to 10 ⁇ m made of an NdF 3 compound and / or an NdOF compound There is a description that the corrosion resistance of the rare earth sintered magnet can be improved by forming the compound layer. However, the improvement in the corrosion resistance is limited to the surface portion of the rare earth sintered magnet on which the NdF 3 compound and / or the NdOF compound is formed.
- DyF 3 dysprosium fluoride
- Dy dysprosium
- an object of the present invention is to provide a rare earth magnet material and a method for manufacturing the same, which can efficiently improve at least the coercive force due to diffusion of Dy or the like as compared with conventional rare earth magnets.
- the present inventor has found that when a diffusing element that can improve the coercive force of a rare earth magnet is diffused inside, oxygen present as an oxide or the like in the rare earth magnet. It has been found that (O) reacts with a diffusing element to inhibit diffusion of the diffusing element into the interior.
- neodymium oxyfluoride neodymium oxyfluoride formed by combining O present in the rare earth magnet with neodymium (Nd) and fluorine (F) is represented by another rare earth element (hereinafter “R”). It was also found to be much more stable than the oxides of). And when this neodymium oxyfluoride was formed in the inside, it newly discovered that a diffusing element fully diffused to the inside of a rare earth magnet. By developing these results, the present invention as described below has been completed.
- R1 a first rare earth element that is one or more of rare earth elements, boron (B), the balance being iron (Fe), and inevitable.
- a magnet powder which is a magnetic alloy powder composed of impurities and / or modifying elements
- a fluoride powder which is a fluoride powder
- at least one of the magnet powder or the fluoride powder is neodymium (Nd And a neodymium which is a reaction product of oxygen (O) or oxide present in the vicinity of the particles of the magnet powder and the fluoride
- a rare dysprosium (Dy) or terbium (Tb) or other diffusing element that is effective in improving the coercive force is diffused without waste to efficiently increase the coercive force.
- a rare earth magnet material can be obtained. If this rare earth magnet material is used, various rare earth magnets having a very high coercive force can be efficiently obtained.
- the reason and mechanism for obtaining such an excellent rare earth magnet material are not necessarily clear, but at present, it is considered as follows.
- the fluoride powder in the heating step of heating the mixed powder of fluoride powder and magnet powder, the fluoride powder reacts with oxides and the like existing in the vicinity of the magnet powder particles. Neodymium oxyfluoride is produced. This neodymium oxyfluoride is much more stable than other existing or new oxides. For this reason, the existing oxide existing in the vicinity of the particle surface of the magnet powder tends to be reduced to neodymium oxyfluoride and the newly generated oxide tends to be neodymium oxyfluoride.
- the fluoride powder captures O mixed in the preparation process, molding process and heating process as an oxygen getter and makes it difficult for oxides other than neodymium oxyfluoride to be generated near the grain boundaries of the magnet powder particles.
- O present in the vicinity of the grain boundary of the magnet powder particles is fixed as neodymium oxyfluoride.
- the fluoride powder is almost uniformly dispersed in the mixed powder, according to the present invention, a rare earth magnet material is obtained in which the above-mentioned action covers the whole including the inside.
- the diffusing element is remarkably suppressed from being trapped by O present at the grain boundaries of the magnet alloy particles, the diffusion efficiency, which is the degree of improvement in coercive force with respect to the diffusion amount of the diffusing element, can be remarkably increased. it can.
- neodymium oxyfluoride is very stable as described above, and maintains a state where O is reliably trapped. For this reason, at least in the vicinity where neodymium oxyfluoride exists, new reactions such as oxidation and hydroxylation of the magnet alloy particles are difficult to proceed, and the corrosion resistance of the rare earth magnet material can be improved. Moreover, in the case of the rare earth magnet material according to the present invention, neodymium oxyfluoride is distributed as a whole, so that the corrosion resistance is exhibited as a whole of the rare earth magnet material, and a demagnetization resistant rare earth magnet superior to the conventional one is obtained. Is possible.
- the present invention is to sinter a molded body made of a mixed powder of magnet powder (NdFeB-based powder) whose main component of R1 is Nd and neodymium fluoride powder, another mixed powder was used. It has also been clarified that a rare-earth magnet material with a higher density can be obtained. The reason and mechanism of this are not necessarily clear, but at present, it is considered as follows. That is, the sintering of the NdFeB-based powder proceeds by melting the Nd-rich phase existing in the grain boundary phase. At this time, generally, the adsorbed oxygen and oxide on the surface of the magnet alloy particles (or crystal grains) are sintered while being reduced by Nd existing in the grain boundary phase. For this reason, Nd that originally promotes sintering is consumed in the production of oxides and the like, and Nd that promotes sintering decreases accordingly, and the sinterability of the NdFeB-based powder can be reduced.
- NdFeB-based powder whose main
- NdFeB-based powder when neodymium fluoride powder is present in the NdFeB-based powder, as described above, the O atoms present in the NdFeB-based powder are trapped as neodymium oxyfluoride and are necessary for the production of the neodymium oxyfluoride. Nd is supplied from neodymium fluoride powder. For this reason, it is suppressed that Nd effective for sintering promotion is consumed wastefully for the production
- R1 and B which are one or more rare earth elements, and the magnetic alloy particles composed of Fe and unavoidable impurities and / or modifying elements in the balance are combined or in close contact with each other.
- a rare earth characterized by comprising a massive magnet body and dispersed particles made of neodymium oxyfluoride, which is a compound of Nd, O, and F, and dispersed throughout the entire surface including the inside of the magnet body It is also grasped as a magnet material.
- the “concentration part” may be formed on the outer periphery of the magnet alloy particles constituting the magnet powder, or may be formed on the outer periphery of the crystal grains constituting the magnet alloy particles.
- the improvement in coercive force due to grain boundary diffusion is considered to occur by repairing the reverse magnetic domain formed at the crystal grain interface, but the “interface” of the particles constituting the magnet powder constitutes the particles. This is because it is also a crystal grain “interface” and it is difficult to strictly distinguish the two. Therefore, the term “grain boundary” or “interface” in this specification means “grain boundary” or “interface” of particles constituting the magnet powder and “grain boundary” of crystal grains constituting the magnet alloy particles unless otherwise specified. ”And“ interface ”.
- the magnet alloy particles are NdFeB-based particles whose main component of R1 is Nd, it is possible to obtain a rare-earth sintered magnet having a higher density than before.
- the rare earth element (R) referred to in this specification includes scandium (Sc), yttrium (Y), and lanthanoid.
- Lanthanoids include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium ( Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).
- Pr, Nd, Sm, Gd, Tb, Dy and the like are preferable as R.
- the first rare earth element (R1), the second rare earth element (R2), or the third rare earth element (R3) referred to in this specification is a rare earth element arbitrarily selected from the above-described R, and if only one kind of rare earth element is used. It may be a rare earth element group consisting of two or more.
- the main R1 is preferably Nd, Dy, Tb and the like effective for improving the coercive force may be contained together with Nd as R1.
- R1, R2 and R3 may be the same rare earth element or different from each other. However, R3 which is a diffusing element is often different from R1 which is a main component constituting magnet powder (magnet alloy particles).
- the modifying element referred to in this specification includes cobalt (Co), lanthanum (La), gallium (Ga), and niobium, which are effective for improving magnetic properties such as coercive force, which improve the heat resistance of rare earth magnet materials.
- Nb aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), germanium (Ge), zirconium
- Zr molybdenum
- Mo indium
- In tin
- Sn hafnium
- Ta tantalum
- Pb lead
- the combination of the modifying elements is arbitrary.
- the content thereof is usually a very small amount, for example, preferably about 0.01 to 10% by mass.
- inevitable impurities are impurities originally contained in the magnet powder and fluoride powder, impurities mixed in at each step, etc., and are elements that are difficult to remove due to cost or technical reasons.
- inevitable impurities include oxygen (O), nitrogen (N), carbon (C), hydrogen (H), calcium (Ca), sodium (Na), potassium (K), and argon (Ar). is there.
- oxygen (O) nitrogen
- N nitrogen
- C carbon
- H hydrogen
- Ca calcium
- Na sodium
- K potassium
- Ar argon
- modification elements and inevitable impurities also apply to the raw materials that serve as the supply source of the diffusion elements in addition to the fluoride powder.
- the “rare earth magnet material” as used in the present invention includes a rare earth magnet material, a rare earth magnet member, and the like, and the form thereof is not limited. Specifically, the rare earth magnet material may be a bulk material before molding or processing, or a rare earth magnet close to or in the shape of the final product. The rare earth magnet material is not limited to a sintered magnet material. The rare earth magnet material does not need to be in a block shape, and may be in a thin film shape, for example.
- x to y in this specification includes the lower limit value x and the upper limit value y.
- various lower limit values or upper limit values described in the present specification can be arbitrarily combined to constitute a range such as “ab”.
- any numerical value included in the range described in the present specification can be used as an upper limit value or a lower limit value for setting the numerical value range.
- the EPMA image of each element of the rare earth sintered magnet obtained by mixing the NdF 3 powder from the surface side is a photograph showing in sequence.
- the EPMA image of each element of the rare earth sintered magnet obtained by mixing the DyF 3 powder from the surface side is a photograph showing in sequence.
- the EPMA image of each element of the rare earth sintered magnet obtained by mixing TbF 3 powder from the surface side is a photograph showing in sequence. It is the photograph which showed the EPMA image of each element of the rare earth sintered magnet which did not mix fluoride powder in order from the surface side. It is the photograph which expanded and showed the EPMA image of Dy of the rare earth sintered magnet which did not mix fluoride powder.
- the present invention will be described in more detail with reference to embodiments of the invention.
- the content demonstrated by this specification including the following embodiment is suitably applied not only to the manufacturing method based on this invention but to rare earth magnet materials.
- One or two or more configurations arbitrarily selected from the configurations shown below can be added to the configuration of the present invention described above.
- the configuration related to the manufacturing method can be a configuration related to the rare earth magnet material if understood as a product-by-process. Which embodiment is the best depends on the target, required performance, and the like.
- the preparation step is a step of mixing a magnet powder that is a magnetic alloy powder and a fluoride powder that is a fluoride powder, and preparing a mixed powder containing Nd in at least one of them.
- the two powders may be mixed using a ball mill, a V-type mixer, a Henschel mixer, a lycra machine, a Spartan-Luzer (high-speed stirrer), or the like until the whole becomes uniform in an antioxidant atmosphere.
- By mixing uniformly it is easy to obtain a rare earth magnet material in which the diffusing element diffuses uniformly.
- it is also effective to prepare by mixing fluoride powder and finely pulverizing both powders before manufacturing the magnet alloy powder.
- Magnet powder Magnet powder is a powder of a magnet alloy composed of R1 and B, which are one or more rare earth elements, and the balance being Fe and inevitable impurities and / or modifying elements.
- the magnet alloy is typically an R1-Fe—B alloy that can constitute R1 2 Fe 14 B as a main phase.
- the magnet alloy has a composition in which an R1 rich phase and the like effective for improving the coercive force and sinterability of the rare earth magnet material are formed rather than the theoretical composition based on R1 2 Fe 14 B. Therefore, it is preferable that the R1-Fe—B based magnet alloy is composed of 10 to 30 atomic% R1, 1 to 20 atomic% B, and the balance Fe when the total is 100 atomic%.
- the magnetic properties may be deteriorated due to the volume ratio of the main phase R1 2 Fe 14 B 1 phase (2-14-1 phase), or the sinterability may be lowered. obtain.
- the lower limit or upper limit of R1 or B can be arbitrarily selected and set within the above range. However, particularly when a rare earth sintered magnet is obtained, if R1 is 12 to 16 atomic% and B is 5 to 12 atomic%, it is easy to obtain a high density rare earth magnet having excellent magnetic properties. Further, Fe is basically the main balance, but it is preferable that Fe is 72 to 83 atomic%.
- the remaining Fe other than R1 and B may vary depending on the presence ratio of elements (modifying elements) and inevitable impurities effective in improving various characteristics of the rare earth magnet.
- Carbon (C) can also be used as an alternative to B, and in that case, it is preferable to prepare such that B + C: 5 to 12 atomic%.
- the magnet powder or rare earth magnet material when expressed as 100% by mass as a whole, has 27 to 35% by mass of Nd and 0.8 to 1. It is good to be comprised by the NdFeB type particle
- the manufacturing method and form of the magnet powder are not limited.
- the magnet powder may be mechanically pulverized or hydrogen pulverized cast magnet alloy having a desired composition. Magnet powder can be super-cooled, whether it is a thin plate-shaped slab that has been rapidly solidified by strip casting or the like, or that has been produced through a hydrogen treatment such as HDDR (hydrogenation-decomposition / dehydrogenation-recombination method). Ribbon grains formed by sputtering or the like may be used. Further, each particle (magnet alloy particle) of the magnet powder may not be composed of clear crystal grains, that is, may be amorphous.
- the particle diameter of the magnet powder is not limited, but the average particle diameter (particle diameter or median diameter when the cumulative mass is 50%) is preferably about 1 to 20 ⁇ m, more preferably about 3 to 10 ⁇ m. If the average particle size is too small, the cost is high, and if the average particle size is too large, the diffusibility of the diffusing element into the inside is excellent, but the density and magnetic properties of the rare earth magnet material are lowered, which is not preferable.
- the magnet powder need not be composed of a single type of powder or composition as described above, and may be a mixture of a plurality of types of powders having different forms such as alloy composition, particle shape, or particle size.
- Fluoride powder is sufficient if it is a fluoride that reacts with O present in the vicinity of the particles of the magnet powder to produce neodymium oxyfluoride. Therefore, regardless of the type of the fluoride, powders made of various fluorides can be used.
- neodymium oxyfluoride is represented by NdOxFy (x and y are real numbers)
- a particularly stable neodymium oxyfluoride is preferably NdOF.
- Nd in neodymium oxyfluoride is not necessarily contained in the fluoride. That is, it is sufficient if it is contained in at least one of fluoride powder and magnet powder. Of course, Nd may be contained in both the magnet powder and the fluoride powder.
- Fluoride constituting the fluoride powder according to the present invention for example, LiF, MgF 2, CaF 2 , ScF 3, VF 2, VF 3, CrF 2, CrF 3, MnF 2, MnF 3, FeF 2, FeF 3 , CoF 2, CoF 3, NiF 2, ZnF 2, AlF 3, GaF 3, SrF 2, YF 3, ZrF 3, NbF 5, AgF, InF 3, SnF 2, SnF 4, BaF 2, LaF 2, LaF 3 , CeF 2, CeF 3, PrF 2, PrF 3, NdF 2, NdF 3, SmF 2, SmF 3, EuF 2, EuF 3, GdF 3, TbF 3, TbF 4, DyF 2, DyF 3, HoF 2, HoF 3 , ErF 2 , ErF 3 , TmF 2 , TmF 3 , YbF 3 , YbF 2 , LuF 2 , LuF 3 , PbF 2 , B It consists of one or more of iF 3 , LaF 2 , La
- the metal element that combines with F in the fluoride generally remains in the rare earth magnet material.
- a metal element is preferably an element that does not degrade the magnetic properties of the rare earth magnet finally obtained as much as possible, and further an element that can further improve the magnetic properties.
- the fluoride powder of the present invention is a rare earth fluoride powder made of a compound of F and a second rare earth element (R2) that is one or more of rare earth elements such as La, Ce, Pr, Nd, Dy, or Tb. And preferred.
- R2 is Dy or Tb because the coercivity of the rare earth magnet material can be improved at the same time.
- the particle diameter of the fluoride powder is not limited, but the finer the particle, the better the dispersibility. Therefore, the average particle diameter (particle diameter or median diameter when the cumulative mass is 50%) as primary particles is preferably about 0.01 to 20 ⁇ m, more preferably about 0.1 to 10 ⁇ m. However, commercially available powders may be agglomerated. In this case, the average particle size (particle size or median size when the cumulative mass is 50%) as the secondary particles is preferably about 1 to 100 ⁇ m, more preferably about 1 to 10 ⁇ m. If the average particle size is too small, the cost is high, and if the average particle size is too large, the dispersibility in the mixed powder is lowered, leading to a decrease in the diffusibility of the diffusing element.
- the fluoride powder may be used in the form of a slurry. Further, the fluoride powder may be nanoparticles prepared and prepared by chemical synthesis, and the average particle diameter is preferably 1 to 200 nm, more preferably 1 to 50 nm. The fluoride powder made of nanoparticles is used as a paste, for example.
- the blending amount of the fluoride powder is prepared in accordance with the amount of O atoms included in the mixed powder (or molded product) subjected to the heating step. That is, it is good to mix
- Nd 2 O 3 formed on the surface or inside of the magnet alloy particles is changed to NdOF using NdF 3 powder, Nd 2 O 3 + NdF 3 ⁇ 3NdOF, so NdF 3 powder is Nd 2 O 3 and sufficient if formulated to be about the same number of moles.
- the blending ratio of the fluoride powder to the magnet powder is 0.1 to 10 atom%, further 0.1 to 0.1% when the whole mixed powder is 100 atom%. It is preferably 5 atomic%, in other words 0.05 to 5% by mass.
- Heating step reacts O present in the vicinity of the magnet powder particles with fluoride to produce neodymium oxyfluoride, and the neodymium oxyfluoride includes not only the surface portion but also the entire interior. This is a step of obtaining a massive rare earth magnet material distributed in the area.
- the heating mode, heating temperature, and the like are arbitrarily adjusted within a range in which the above neodymium oxyfluoride is generated in the mixed powder mixed almost uniformly and O present at the grain boundaries is captured.
- the heating temperature cannot be specified unconditionally because it depends on the composition of the magnet powder or fluoride powder, but if rare earth fluoride powder is used, it is 300 to 1200 ° C., more preferably 800 to 1100 ° C. Good. If the heating temperature is too low, neodymium oxyfluoride is hardly formed, and if it is too high, it is not preferable in terms of heating efficiency and magnetic properties.
- the heating step may be a sintering step for obtaining a sintered body obtained by sintering a compact formed with a mixed powder, and the sintering temperature at this time is 700 to 1150 ° C. Is preferably 900 to 1100 ° C. If the sintering temperature is too low, the sintering efficiency is lowered. If the sintering temperature is too high, problems such as melting occur, and the heating efficiency and magnetic properties are not preferable.
- the diffusion process is a process of diffusing a diffusing element into the rare earth magnet material after the heating process (or sintering process).
- This diffusing element is preferably composed of a third rare earth element (R3) which is one or more of the rare earth elements.
- R3 is one or more of the rare earth elements.
- Dy, Tb, and the like that improve the coercive force of the rare earth magnet material are preferable.
- the diffusion includes grain boundary diffusion that diffuses to the grain boundaries of the magnet powder particles or crystal grains, and internal diffusion (body diffusion) that diffuses by dissolving them in the solid solution. Grain boundary diffusion is preferable in order to efficiently improve magnetic properties such as coercive force while reducing the amount of rare diffusion elements used.
- the grain boundary diffusion is performed very efficiently. That is, the diffusion efficiency calculated by ⁇ (coercivity after diffusion of diffusion element) ⁇ (coercivity before diffusion of diffusion element) ⁇ / (diffusion amount of diffusion element) is very high.
- the diffusion efficiency is 20 to 60 (kOe / mass%) or 1590 to 4770 (kAm ⁇ 1 / mass%).
- the method of the diffusion process is not limited.
- a vapor deposition method in which sputtering is performed using a diffusion material such as metal Dy as a target, and a rare earth magnet material and a diffusion material disposed in the vicinity thereof are heated in a heating furnace to directly place the rare earth magnet material in the vapor of the diffusion element.
- the diffusion step is performed by an exposure steam method, a coating method in which fluoride powder is applied to the surface of the rare earth magnet material and heating, a method in which fluoride slurry is applied and heated, as disclosed in Patent Document 2, and the like.
- NdOF neodymium oxyfluoride
- Nd 2 O 3 , NdO x An oxide (Nd 2 O 3 , NdO x ) or the like made of an Nd-rich phase or mixed O may exist at the grain boundary of the rare earth magnet material composed of the NdFeB-based powder.
- (R2) F3 powder particles are present in the vicinity of the grain boundary, NdOF is generated by the following reaction, and R2 is liberated.
- (R2) F 3 powder was liberated when no other than NdF 3 powder R2 (Dy, Tb, etc.), R1 (Nd) 2 Fe 14 coercivity of a rare earth magnet material by solid solution in the main phase of the B It contributes to the improvement.
- Dy which is a kind of diffusing element
- Dy diffuses into a rare earth magnet material made of NdFeB-based powder.
- Dy is an oxide (Nd 2 O 3 , NdO x ) or the like present at the grain boundary as follows: react. 2Dy + Nd 2 O 3 ⁇ Dy 2 O 3 + 2Nd (Scheme 3)
- the diffusion element (Dy) introduced into the corner also changes to an oxide in the course of diffusion and is captured at the grain boundary triple point, etc., and does not contribute to the suppression of domain wall movement and reverse domain formation at the interface.
- the coercive force cannot be effectively improved. That is, the diffusing element is wasted, and in particular, the coercive force inside the rare earth magnet material cannot be improved. This state is schematically shown in FIG. 1A.
- Dy smoothly diffuses from the grain boundary phase of the magnet alloy particles or crystal grains so as to wrap around the main phase interface, and the starting point that causes a decrease in coercive force is remarkably reduced. In this way, a rare earth magnet material having a significantly improved coercive force can be obtained efficiently.
- the fluoride powder according to the present invention is made of a fluoride of a diffusing element (for example, DyF 3 , TbF 3, etc.), as shown in the above reaction formula 1, in the heating step, the diffusing element (for example, Dy, Tb) Etc.) can be liberated.
- the diffusing element for example, Dy, Tb
- Etc. the diffusing element
- This liberated diffusing element can be dissolved in the magnet alloy particles prior to the diffusing step.
- the diffusion element introduced separately in the subsequent diffusion step is no longer easily dissolved in the magnet alloy particles, and the grain boundary diffusion is more likely to proceed preferentially. That is, the coercive force of the rare earth magnet material can be increased more efficiently while suppressing the amount of diffusion element used.
- the rare earth magnet material of the present invention may be a raw material as described above, or a final product or a rare earth magnet close thereto. The use and form of this rare earth magnet do not matter.
- the rare earth magnet material of the present invention is used in, for example, various electromagnetic devices such as a rotor or stator of an electric motor, a magnetic recording medium such as a magnetic disk, a linear actuator, a linear motor, a servo motor, a speaker, and a generator.
- Test Example 1 Relationship between coercive force and amount of diffusing elements >> (1) The relationship between the coercive force of the rare earth sintered magnet (rare earth magnet material) and the diffusion amount of the diffusing element (R3) was examined in advance.
- This magnet powder was molded into a 20 ⁇ 15 ⁇ 10 mm rectangular parallelepiped shape in a magnetic field (molding step).
- the applied magnetic field is 2T.
- the molded body thus obtained was heated at 1050 ° C. ⁇ 4 Hr in a vacuum atmosphere of ⁇ 10 ⁇ 3 Pa to obtain a sintered body (sintering step). After the surface of this sintered body was polished, Dy diffusion treatment was performed on the polished surface (diffusion process).
- This diffusion treatment is performed by heating a sintered body and a Dy simple substance (metal Dy) arranged approximately 10 mm apart in a container (heating furnace) in a vacuum atmosphere of 10 ⁇ 4 Pa at 750 to 850 ° C. for 16 to 128 hours. went. The amount of Dy diffused was adjusted by adjusting the heating temperature or heating time. Further, the sintered body after the diffusion treatment was heated at 480 ° C. for 1 hour in a vacuum atmosphere of 10 ⁇ 2 Pa (homogenization treatment, aging treatment).
- Various fluoride powders were mixed into magnet powder (Fe-31.5% Nd-1% B-1% Co-0.2% Cu) having the same composition as in Test Example 1 (preparation step).
- the prepared fluoride powders are all rare earth fluoride powders, and are NdF 3 powder, DyF 3 powder, and TbF 3 powder.
- the compounding quantity of fluoride powder was 1.5 mass% with respect to the whole mixed powder (100 mass%).
- the measurement results thus obtained are also shown in Table 1.
- the diffusion efficiency in Table 1 is calculated by ⁇ (coercivity after Dy diffusion) ⁇ (coercivity before Dy diffusion) ⁇ / (Dy diffusion amount).
- the results of Table 1 are shown in a dispersion diagram of FIGS. 3A and 3B (both are referred to as “FIG. 3” as appropriate).
- ⁇ indicates the case where the fluoride powder is mixed with the magnet powder
- X indicates the case where the fluoride powder is not mixed.
- Test Example 3 Effect of Fluoride Powder on Diffusion Form >> (1) Each sample was prepared by changing the blending amount of the fluoride powder shown in Test Example 2 from 0.9% by mass to 3% by mass, and the EPMA image was observed. The results are shown in FIGS. Further, FIG. 7 shows an EPMA image of a sample in which the fluoride powder is not blended with the magnet powder, and FIG. 8 shows an enlarged image of Dy at 300 ⁇ m from the surface in the EPMA image.
- the EPMA images of Nd and O are approximated as shown in FIG. 7, and the neodymium oxide (Nd 2 O 3 or the like) has a grain boundary (particularly 3 It can be seen that they are agglomerated in the vicinity of the emphasis.
- such agglomeration of neodymium oxide is not observed when the fluoride powder is mixed with the magnet powder. That is, regardless of the type of fluoride powder, neodymium oxide (Nd 2 O 3 or the like) or the like becomes neodymium oxyfluoride (NdOF) and is stably distributed in the rare earth sintered magnet. 6
- Test Example 4 Influence on sinterability of fluoride powder >> (1) Magnet powder (Fe-31.5% Nd-1% B) manufactured in the same manner as in Test Example 1 except that only the alloy composition was changed was prepared. Also, as the fluoride powder, LaF 3 powder, CeF 3 powder, PrF 3 powder, NdF 3 powder, DyF 3 powder and TbF 3 powder, all of which are rare earth fluoride powders, were prepared. The mixed powder was prepared by mixing any of the fluoride powders with the magnet powder with the total mixed powder being 100% by mass (preparation step).
- the density of the various sintered bodies obtained was measured by the Archimedes method. The results are shown in Table 2. The density of the sintered body in which the LaF 3 powder, the DyF 3 powder, and the TbF 3 powder were mixed was lower than the density of the sintered body in which the fluoride powder was not mixed. The density of the sintered body in which CeF 3 powder and PrF 3 powder were mixed was not significantly different from the density of the sintered body in which fluoride powder was not mixed.
- the density of the sintered body in which the NdF 3 powder was mixed increased as compared with any other sintered body. Therefore, it is clear that the use of NdF 3 powder as the fluoride powder not only promotes the internal diffusion of Dy as described above, but also improves the sinterability of the rare earth sintered magnet to increase the density. became.
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Abstract
Description
(1)すなわち、本発明の希土類磁石材の製造方法は、希土類元素の一種以上である第1希土類元素(以下「R1」と表す。)とホウ素(B)と残部が鉄(Fe)および不可避不純物および/または改質元素とからなる磁石合金の粉末である磁石粉末とフッ化物の粉末であるフッ化物粉末とを混合してなり、該磁石粉末または該フッ化物粉末の少なくとも一方がネオジム(Nd)を含む混合粉末を調製する調製工程と、該混合粉末の成形体を加熱して、前記磁石粉末の粒子近傍に存在する酸素(O)または酸化物と前記フッ化物との反応物であるネオジム酸フッ化物を表面部のみならず内部を含む全体に分布させた塊状の希土類磁石材を得る加熱工程と、を備えることを特徴とする。
本発明の希土類磁石材の製造方法によれば、フッ化物粉末と磁石粉末との混合粉末を加熱する加熱工程で、そのフッ化物粉末が磁石粉末の粒子近傍に存在する酸化物等と反応してネオジム酸フッ化物が生成される。このネオジム酸フッ化物は、既存または新成の他の酸化物よりも遙かに安定である。このため、磁石粉末の粒子表面近傍に存在する既存の酸化物は還元等されてネオジム酸フッ化物に変化し易くなり、また新たに生成される酸化物はネオジム酸フッ化物となり易い。こうしてフッ化物粉末は、調製工程、成形工程や加熱工程で混入するOを酸素ゲッターとして捕捉し、磁石粉末粒子の粒界近傍にネオジム酸フッ化物以外の酸化物が生成され難くする。言い換えるなら、磁石粉末粒子の粒界近傍に存在するOはネオジム酸フッ化物として固定される。しかもフッ化物粉末は混合粉末中にほぼ均一に分散しているので、本発明によれば、上記作用が内部を含む全体に及ぶ希土類磁石材が得られることになる。
すなわち、NdFeB系粉末の焼結は、粒界相に存在するNdリッチ相が溶融して進行する。この際、一般的に、磁石合金粒子(または結晶粒)の表面にある吸着酸素や酸化物は、その粒界相に存在するNdによって還元されつつ焼結が進行する。このため、本来は焼結を促進させるNdが、酸化物などの生成に消費され、その分、焼結を促進させるNdが減少し、NdFeB系粉末の焼結性が低下し得る。
本発明は上述した製造方法としてのみならず、その製造方法により得られた希土類磁石材としても把握される。
(1)より具体的にいえば、本発明は、希土類元素の一種以上であるR1とBと残部がFeおよび不可避不純物および/または改質元素とからなる磁石合金粒子が結合または密接してなる塊状の磁石体と、NdとOとFとの化合物であるネオジム酸フッ化物からなり該磁石体の表面部のみならず内部を含む全体に散在する分散粒子と、を有することを特徴とする希土類磁石材としても把握される。
(1)本明細書でいう希土類元素(R)には、スカンジウム(Sc)、イットリウム(Y)、ランタノイドを含む。ランタノイドは、ランタン(La)、セリウム(Ce)、プラセオジム(Pr)、ネオジム(Nd)、サマリウム(Sm)、ユウロピウム(Eu)、ガドリニウム(Gd)、テルビウム(Tb)、ジスプロシウム(Dy)、ホルミウム(Ho)、エルビウム(Er)、ツリウム(Tm)、イッテルビウム(Yb)およびルテチウム(Lu)などがある。なかでも、RとしてPr、Nd、Sm、Gd、Tb、Dyなどが好ましい。
(1)調製工程
調製工程は、磁石合金の粉末である磁石粉末とフッ化物の粉末であるフッ化物粉末とを混合し、それらの少なくとも一方にNdが含まれる混合粉末を調製する工程である。両粉末の混合はボールミル、V型混合機、ヘンシェルミキサー、ライカイ機、スパルタンリューザ(高速攪拌装置)などを用いて、酸化防止雰囲気中で全体が均一になるまで混合するとよい。均一に混合することにより、拡散元素が均一に拡散する希土類磁石材が得られ易い。
また、磁石合金粉末の製作前にフッ化物粉末を混合し、両粉末を同時に微粉砕して調製することも有効である。
磁石粉末は、希土類元素の一種以上であるR1とBと残部がFeおよび不可避不純物および/または改質元素とからなる磁石合金の粉末である。磁石合金は、主相となるR12Fe14Bを構成し得るR1-Fe-B系合金が代表的である。もっとも磁石合金は、R12Fe14Bに基づく理論組成よりも、希土類磁石材の保磁力や焼結性の向上に有効なR1リッチ相などが形成される組成とすると好ましい。そこでR1-Fe-B系の磁石合金は、全体を100原子%としたときに10~30原子%のR1と、1~20原子%のBと、残部であるFeとからなると好ましい。いずれの元素も過少または過多では、主相であるR12Fe14B1相(2-14-1相)の体積率に影響して磁気特性が悪化したり、焼結性が低下したりし得る。R1またはBの下限値または上限値は、上記範囲内で任意に選択し設定し得る。もっとも、特に希土類焼結磁石を得る場合、R1は12~16原子%、Bは5~12原子%であると磁気特性に優れる高密度な希土類磁石が得られ易い。さらに、Feは基本的に主たる残部であるが、あえていえばFeは72~83原子%であると好ましい。ただし、R1やB以外の残部であるFeは、希土類磁石の種々の特性の改善に有効な元素(改質元素)や不可避不純物の存在割合によって変化し得る。なお、Bの代替として炭素(C)を用いることもでき、その場合はB+C:5~12原子%となるように調製すると好ましい。
磁石粉末は、その製造方法や形態を問わない。磁石粉末は、所望組成の鋳造磁石合金を機械粉砕したものでも水素粉砕したものでもよい。また磁石粉末は、ストリップキャスト等により急冷凝固させた薄板状の鋳片でも、HDDR(水素化-分解・脱水素-再結合法)のような水素処理を経て製造されたものでも、超急冷されたリボン粒でも、スパッタ等により成膜したものでもよい。さらに磁石粉末の各粒子(磁石合金粒子)は、明確な結晶粒によって構成されたものでなくても、すなわち、アモルファス状でもよい。
磁石粉末は、上述した組成や形態が一種類の粉末からなる必要はなく、合金組成、粒形または粒径などの形態が異なる複数種の粉末が混合されたものでもよい。
フッ化物粉末は、磁石粉末の粒子近傍に存在するOと反応してネオジム酸フッ化物を生成するフッ化物であれば足る。従って、そのフッ化物の種類は問わず、様々なフッ化物からなる粉末を用いることができる。なお、ネオジム酸フッ化物はNdOxFy(x、yは実数)で表されるが、特に安定なネオジム酸フッ化物はNdOFであると好ましい。ネオジム酸フッ化物中のNdは、フッ化物中に必ずしも含まれている必要はない。つまり、フッ化物粉末か磁石粉末のいずれか一方に少なくとも含まれていれば足る。勿論、磁石粉末とフッ化物粉末の両方にNdが含まれていてもよい。
さらにフッ化物粉末は、化学合成で作製・調製したナノ粒子でもよく、その平均粒径は1~200nmさらには1~50nmであると好ましい。ナノ粒子からなるフッ化物粉末は、例えば、ペーストにして用いられる。
加熱工程は、磁石粉末の粒子近傍に存在するOとフッ化物とを反応させてネオジム酸フッ化物を生成させ、そのネオジム酸フッ化物が、表面部のみならず内部を含む全体に分布した塊状の希土類磁石材を得る工程である。
希土類焼結磁石を製造する場合なら、加熱工程は混合粉末を成形した成形体を焼結させた焼結体を得る焼結工程とすればよく、このときの焼結温度は700~1150℃さらには900~1100℃であると好ましい。焼結温度が過小では焼結効率が低下し、焼結温度が過大では、溶融などの障害を生じ、また加熱効率や磁気特性の点でも好ましくない。
拡散工程は、上記の加熱工程(または焼結工程)後の希土類磁石材内へ拡散元素を拡散させる工程である。この拡散元素は、希土類元素の一種以上である第3希土類元素(R3)からなると好ましい。具体的には、希土類磁石材の保磁力を向上させるDyやTbなどが好ましい。
拡散工程の方法は問わない。例えば、金属Dyなどの拡散素材をターゲットにしてスパッタリング等を行う蒸着法、希土類磁石材とその近傍に配置した拡散素材とを加熱炉内で加熱して拡散元素の蒸気中に希土類磁石材を直接曝す蒸気法、特許文献2などにあるように希土類磁石材の表面にフッ化物粉末を塗布して加熱する塗布法やフッ化物スラリーを塗布加熱する方法などにより、拡散工程がなされる。
(1)ネオジム酸フッ化物の生成メカニズム
上述したことを踏まえて、ネオジム酸フッ化物(NdOF)が形成されるメカニズムを、NdFeB系粉末(磁石粉末)と(R2)F3粉末(フッ化物粉末)との混合粉末を用いて希土類磁石材を製造する場合を例にとり説明する。
(R2)F3 +Nd2O3+Nd → 3NdOF+R2 (反応式1)
NdF3 +Nd2O3 → 3NdOF (反応式2)
ここで磁石粉末を焼結させる場合を考えると、通常であれば、粒界に存在する吸着酸素や酸化物などが粒界相にあるNdによって還元されつつ、焼結が進行する。従ってOの混在する分、粒界相に存在するNdが消費されて、焼結性に機能するNdが減少し得る。
この結果、フッ化物粉末にNdF3粉末を用いた場合、焼結性が大幅に改善されることになり、比較的低い焼結温度でも十分に高密度な希土類焼結磁石が得られるようになる。
拡散元素の一種であるDyがNdFeB系粉末からなる希土類磁石材へ拡散する場合を例にとり、拡散メカニズムを説明する。
先ず、フッ化物粉末を含まない磁石粉末からなる従来の希土類磁石材へ拡散処理を行うと、例えば、Dyは粒界に存在する酸化物(Nd2O3、NdOx)等と次のような反応する。
2Dy+Nd2O3 → Dy2O3+2Nd (反応式3)
本発明の希土類磁石材は、前述したように素材であっても最終製品またはそれに近い希土類磁石であってもよい。この希土類磁石の用途や形態は問わない。本発明の希土類磁石材は、例えば、電動機のロータまたはステータなどの各種電磁機器、磁気ディスクなどの磁気記録媒体、リニアアクチュエータ、リニアモータ、サーボモータ、スピーカー、発電機等に用いられる。
《試験例1:保磁力と拡散元素量の関係》
(1)希土類焼結磁石(希土類磁石材)の保磁力と拡散元素(R3)の拡散量との関係を事前に調べた。このために用いた試料は次のようして製作した。
先ず、Fe-31.5%Nd-1%B-1%Co-0.2%Cu(単位は質量%)の磁石合金を鋳造した。この磁石合金を水素粉砕した後、さらにジェットミルで粉砕することにより、平均粒径D50(メジアン径)=6μmの磁石粉末を得た。ジェットミルによる粉砕は窒素雰囲気で行った。
さらにこの拡散処理後の焼結体に対して、10-2Paの真空雰囲気で480℃x1時間の加熱を行った(均質化処理、時効処理)。
(1)磁石粉末中へフッ化物粉末を混合した混合粉末を用意した。この混合粉末の成形体を焼結させた希土類焼結磁石(希土類磁石材)へ拡散処理を施したときの保磁力を調べた。具体的にはつぎのような試料を作成して評価した。
また、比較試料として、フッ化物粉末を混合せずに製作した希土類焼結磁石を用意した。その内の一つの試料については、先ず拡散処理前の保磁力を測定した(試料No.A41)。別の試料については、上述した拡散処理後の保磁力およびDy拡散量を測定した(試料No.A21~A26)。
さらに、フッ化物粉末を混合せずに製作した希土類焼結磁石の研磨面にDyF3粉末またはTbF3粉末を塗布して、DyまたはTbを拡散させたときの保磁力およびDy拡散量を測定した(試料No.A31~A34および試料No.A35~A37)。この塗布法による拡散処理(塗布拡散)は、10μmのDyF3粉末またはTbF3粉末をアルコールに分散させたスラリーを希土類焼結磁石へ塗布し、この希土類焼結磁石を10-4Paの真空中で加熱することにより行った。その際の塗布割合は、希土類焼結磁石100質量部に対して0.2質量部とした。また、その加熱温度および加熱時間は表1に示した。
一方、磁石粉末中にフッ化物粉末を混合しない場合、Dy・Tbの拡散量が増加しても、保磁力はあまり向上していない。この傾向は、蒸気法によりDyを拡散させた場合でも(試料No.A21~A26)、DyF3粉末やTbF3粉末の塗布によりDyやTbを拡散させた場合でも(試料No.A31~A37)、同じであった。これは、磁石粉末中へフッ化物粉末を混合しない場合、DyやTbの拡散が希土類焼結磁石の表面部分に限られるためと考えられる。これらのことは、表1および図3Bに示した拡散効率からも明らかである。
(1)試験例2で示したフッ化物粉末の配合量を0.9質量%から3質量%へ変更した各試料を製作し、そのEPMA像を観察した。この結果を図4~図6に示す。また、フッ化物粉末を磁石粉末へ配合しない試料のEPMA像を図7に、さらにそのEPMA像の内で表面から300μmにおけるDyに関する拡大像を図8に示した。
これらに対して、フッ化物粉末を磁石粉末へ混合しなかった場合、Dyは希土類焼結磁石の表面近傍に集中的に分布し、内部まで拡散していないことが図7からわかる。この原因は、希土類焼結磁石の表面近傍に存在する磁石合金粒子の粒界(特に3重点近傍)にDyが凝集しているためと図8から考えられる。また、図7のEPMA像中のFの分布からも分かるように、Fは希土類焼結磁石の表面部分にしか検出されず、内部では検出されなかった。従って、フッ化物粉末を磁石粉末へ混合しなかった希土類焼結磁石の場合、NdOFが内部に存在することはない。
(1)試験例1に対して合金組成のみ変更して他は同様に製造した磁石粉末(Fe-31.5%Nd-1%B)を用意した。またフッ化物粉末には、いずれも希土類フッ化物粉末であるLaF3粉末、CeF3粉末、PrF3粉末、NdF3粉末、DyF3粉末およびTbF3粉末を用意した。混合粉末全体を100質量%として、このいずれかのフッ化物粉末を前記磁石粉末へ混合して混合粉末を調製した(調製工程)。
なお比較試料として、フッ化物粉末を混合しない磁石粉末を用いて同様な焼結体を製作した(試料No.B7)。
LaF3粉末、DyF3粉末およびTbF3粉末を混合した焼結体の密度は、フッ化物粉末を混合しなかった焼結体の密度より低下した。CeF3粉末およびPrF3粉末を混合した焼結体の密度は、フッ化物粉末を混合しなかった焼結体の密度と大差なかった。
Claims (15)
- 希土類元素の一種以上である第1希土類元素(以下「R1」と表す。)とホウ素(B)と残部が鉄(Fe)および不可避不純物および/または改質元素とからなる磁石合金の粉末である磁石粉末とフッ化物の粉末であるフッ化物粉末とを混合してなり、該磁石粉末または該フッ化物粉末の少なくとも一方がネオジム(Nd)を含む混合粉末を調製する調製工程と、
該混合粉末を加熱して、前記磁石粉末の粒子近傍に存在する酸素(O)または酸化物と前記フッ化物との反応物であるネオジム酸フッ化物を表面部のみならず内部を含む全体に分布させた塊状の希土類磁石材を得る加熱工程と、
を備えることを特徴とする希土類磁石材の製造方法。 - 前記R1はNdである請求項1に記載の希土類磁石材の製造方法。
- 前記フッ化物粉末は、希土類元素の一種以上である第2希土類元素(以下「R2」と表す。)とフッ素(F)とからなる希土類フッ化物の粉末である請求項1に記載の希土類磁石材の製造方法。
- 前記R2はNdである請求項3に記載の希土類磁石材の製造方法。
- さらに、前記希土類磁石材内へ希土類元素の一種以上である第3希土類元素(以下「R3」と表す。)からなる拡散元素を拡散させる拡散工程を備える請求項1に記載の希土類磁石材の製造方法。
- 前記拡散元素は、ジスプロシウム(Dy)またはテルビウム(Tb)である請求項5に
記載の希土類磁石材の製造方法。 - 前記調製工程は、前記混合粉末に対する前記フッ化物粉末の配合量を前記希土類磁石材中に含有され得る酸素原子の混入量に応じて調製する工程である請求項1に記載の希土類磁石材の製造方法。
- 前記加熱工程は、前記混合粉末を成形した成形体を焼結させた焼結体を得る焼結工程である請求項1に記載の希土類磁石材の製造方法。
- 前記磁石粉末は、全体を100質量%(以下「%」と表す。)としたときに27~35%のNdと0.8~1.5%のBを含むNdFeB系合金からなるNdFeB系粉末であり、
前記フッ化物粉末は、ネオジムフッ化物からなるネオジムフッ化物粉末である請求項1に記載の希土類磁石材の製造方法。 - 請求項1に記載の製造方法により得られたことを特徴とする希土類磁石材。
- 焼結体からなる請求項10に記載の希土類磁石材。
- 希土類元素の一種以上であるR1とBと残部がFeおよび不可避不純物および/または改質元素とからなる磁石合金粒子が結合または密接してなる塊状の磁石体と、
NdとOとFとの化合物であるネオジム酸フッ化物からなり該磁石体の表面部のみならず内部を含む全体に散在する分散粒子と、
を有することを特徴とする希土類磁石材。 - さらに、前記R1とは異なる希土類元素の一種以上であるR3が前記磁石合金粒子の外郭の少なくとも一部に濃化してなる濃化部を有する請求項12に記載の希土類磁石材。
- 前記R3はDyまたはTbである請求項13に記載の希土類磁石材。
- 前記磁石合金粒子は、全体を100%としたときに27~35%のNdと0.8~1.5%のBを含むNdFeB系粒子であり、
前記磁石体は、前記磁石合金粒子が焼結した焼結体である請求項12に記載の希土類磁石材。
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