WO2016175332A1 - 希土類永久磁石および希土類永久磁石の製造方法 - Google Patents
希土類永久磁石および希土類永久磁石の製造方法 Download PDFInfo
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Definitions
- the present disclosure relates to a rare earth permanent magnet containing neodymium, iron, and boron.
- Patent Document 1 As a technique for improving the magnetic properties of rare earth permanent magnets containing neodymium (Nd), iron (Fe), and boron (B), there is a magnet in which Fe is substituted with cobalt (Co) (Patent Document 1).
- Patent Document 1 comprehensively measures the coercive force Hc, residual magnetic flux density Br, maximum energy product BH max, and the like of a permanent magnet in which Fe is replaced with another atom, and shows an improvement in the magnetic characteristics of the permanent magnet.
- R is a weight percent and R (R is at least one rare earth element including Y, and Nd in R is 50 atomic% or more): 25 to 35%, B: 0.8 to 1.5% If necessary, M (at least one selected from Ti, Cr, Ga, Mn, Co, Ni, Cu, Zn, Nb, Al): 8% or less, and the rare earth containing the remainder T (Fe or Fe and Co) A sintered magnet is disclosed.
- Another proposal for improving the magnetic properties of rare earth permanent magnets is a nano-structure with a two-phase composite structure in which the hard magnetic phase of nanoparticles composed of Nd, Fe, and B is the core and the soft magnetic phase of the specified nanoparticles is the shell.
- a composite magnet There is a composite magnet.
- the above-mentioned nanocomposite magnet has good exchange interaction between the hard / soft magnetic phase of the core / shell, particularly when the soft magnetic material is covered with a grain boundary consisting of ultrafine grains of 5 nm or less to form a shell. Saturation magnetization can be improved.
- Patent Document 3 discloses a nanocomposite magnet having Nd 2 Fe 14 B compound particles as a core and Fe particles as a shell. By using FeCo alloy nanoparticles with high saturation magnetization as the shell component, the saturation magnetization of the nanocomposite magnet is further improved.
- Patent Document 4 discloses a nanocomposite magnet in which a core of NdFeB hard magnetic phase is coated with a shell of FeCo soft magnetic phase.
- Patent Document 5 in magnetically composition of the hard phase is R x T 100-xy M y ( formula defined in atomic percent, R is selected rare earths, yttrium, scandium, or combinations thereof, T is selected from one or more transition metals; M is selected from Group IIIA elements, Group IVA elements, Group VA elements, or combinations thereof; x is in the corresponding rare earth transition metal compound; Greater than the stoichiometric amount of R; y is from 0 to about 25), and at least one magnetically soft phase comprises at least one soft magnetic material containing Fe, Co, or Ni.
- An anisotropic bulk nanocomposite rare earth permanent magnet is disclosed.
- Non-Patent Document 1 discloses a method for producing FeCo nanoparticles at a high temperature. However, the coercive force H cj of the Nd 2 Fe 14 B particles produced at a high temperature is not good.
- Non-Patent Document 2 to Non-Patent Document 5 it is known that rare earth permanent magnets in which B is replaced by C have a reduced Curie temperature, and a significant decrease in saturation magnetization and residual magnetic flux density Br.
- the C atom or the N atom forms a covalent bond with the atoms existing around them.
- Such rare earth permanent magnets have a low magnetic property, particularly a residual magnetic flux density Br, because unpaired electrons essential to the magnetic material are remarkably reduced.
- the problem of the present disclosure is to improve the magnetic characteristics of a rare earth permanent magnet having a main phase containing Nd, Fe, and B.
- One embodiment of the present disclosure includes one or more elements R selected from the group consisting of Nd and Pr, one or more elements L selected from the group consisting of Co, Be, Li, Al, and Si, and Tb and Sm.
- This disclosure can improve the magnetic properties of a rare earth permanent magnet having a main phase containing Nd, Fe, and B.
- One embodiment of the present disclosure includes one or more elements R selected from the group consisting of Nd and Pr, one or more elements L selected from the group consisting of Co, Be, Li, Al, and Si, and Tb and Sm.
- the residual magnetic flux density Br can be improved by replacing some of the predetermined B atoms with the atoms of the element L.
- the Fe atom occupying the 4c site not only the B atom occupying the 4f site, but also the Nd atom occupying the 4f site of the crystal belonging to P4 2 / mnm, the Fe atom occupying the 4c site, and 8j A part of atoms selected from the group consisting of Fe atoms occupying the site may be substituted with atoms of the element L. Even in such an embodiment, the residual magnetic flux density Br of the rare earth permanent magnet can be improved.
- whether or not some of the predetermined atoms are replaced with the atoms of the element L can be determined by Rietveld analysis. That is, the presence or absence of the substitution is determined based on the space group of crystals forming the main phase specified by the analysis and the occupancy of each element in each site existing in the space group.
- the present disclosure does not exclude determining whether or not the predetermined substitution is present in the crystal structure of the rare earth permanent magnet by a method different from the Rietveld analysis.
- the crystals forming the main phase of the present disclosure belong to P4 2 / mnm.
- the occupancy rate of the element L at the 4f site occupied by B atoms in the space group is defined as n.
- n> 0.000 it can be determined that some of the B atoms occupying the 4f site are replaced with atoms of the element L.
- the occupancy ratio of the B atom that occupies the 4f site together with the element L can be defined as 1.000-n.
- the upper limit of the value of the element occupancy n of the element L is not limited.
- n tends to be calculated within the range of 0.030 ⁇ n ⁇ 0.100.
- the occupancy is expressed as a percentage, it is (n ⁇ 100)%.
- the s value is 1.3 or less, and is preferably closer to 1. Most preferably 1.
- the s value is a value obtained by dividing the R-weighted pattern (R wp ) of the reliability factor R by R-expected (R e ).
- One embodiment of the present disclosure includes one or more elements R selected from the group consisting of Nd and Pr, one or more elements L selected from the group consisting of Co, Be, Li, Al, and Si, and Tb and Sm. And a main phase containing one or more elements A selected from the group consisting of Gd, Ho, and Er, Fe, and B.
- the improvement of the residual magnetic flux density Br is particularly remarkable by containing Sm (samarium) and Gd (gadolinium).
- the coercive force H cj can be improved by containing Tb (terbium), Ho (holmium), and Er (erbium). Therefore, by substituting B with the predetermined element L and containing the element A, it is possible to improve both the residual magnetic flux density Br and the coercive force H cj .
- the crystal periodically has an R-Fe-B layer containing an element R selected from the group consisting of Nd and Pr, Fe, and B, an Fe layer, and a part of the B atoms.
- the R-Fe-B layer is substituted with the element L atom, and the R-Fe-B layer contains the element A atom.
- the space group P4 2 / mnm of the main phase crystal there are two 16k, two 8j, one 4g, two 4f, one 4e, and one 4c sites.
- 16k when there are a plurality of sites such as 16k, they may be described as the first 16k and the second 16k.
- the expressions such as “first”, “second”, and the like are attached to distinguish the sites, and do not characterize each site except in the case described in this specification.
- the R atom that occupies the first 4f site, the 4g site, the Fe atom that occupies the 4c site, and the B atom that occupies the second 4f site are R -Fe-B layer is formed.
- Fe atoms occupying two 16k sites, two 8j sites, and a 4e site form an Fe layer.
- FIG. 1 is an example of a crystal structure model of a main phase of a rare earth permanent magnet according to one embodiment of the present disclosure corresponding to the above aspect.
- 100 is a unit cell of the main phase
- 101 is an Fe layer
- 102 is an R—Fe—B layer.
- the Fe layers 101 and the R—Fe—B layers 102 are alternately present along the c-axis direction.
- the distance between two R-Fe-B layers 102 adjacent to each other with the Fe layer 101 interposed therebetween is 0.59 to 0.62 nm.
- This embodiment uses the crystal structure model shown in FIG. 1 as a basic skeleton.
- part of the B atoms constituting the basic skeleton is replaced with the element L (Co in FIG. 1).
- the atoms of the element L can be substituted with Fe atoms.
- the atom of the element L can be substituted with an Nd atom.
- the number of atoms constituting the unit cell of the main phase represents 90 to 98 at% of the number of atoms of the rare earth permanent magnet particles.
- impurities can be included in the main phase within a range in which the effect can be obtained.
- This embodiment can suppress a decrease in the magnetic moment of the element R by reducing the B content. Further, the reduction of the B content makes the basic skeleton unstable, and other elements easily enter the basic skeleton and voids in the basic skeleton. In rare earth permanent magnets containing C as another element, B is easily replaced with C when the basic skeleton becomes unstable.
- this embodiment does not contain C or contains a very small amount of C.
- B is replaced with the element L and not C.
- the portion substituted with C is less than the portion substituted with element L.
- this embodiment in order to obtain a crystal structure in which B is substituted with the element L, this embodiment suppresses the B content and controls the amount of C so that C does not enter the crystal structure of the main phase.
- the predetermined crystal structure of this embodiment can be obtained by eliminating as much as possible contact between the raw material alloy and paper, plastic, oil, or the like as the C source.
- B in the raw material alloy is 0.94% and C is 0.03%, which is obtained by sintering this raw material alloy.
- B may be 0.94% and C may be 0.074%.
- B is 0.86% and C is 0.009% in the raw material alloy
- B is 0.86% and C is 0.059% in the rare earth permanent magnet of this embodiment obtained by sintering this raw material alloy.
- ICP emission spectrometer ICP-Emission Spectroscopy
- the center in the grain that is, the main phase part was analyzed by a three-dimensional atom probe (3DAP).
- 3DAP three-dimensional atom probe
- the C content in the main phase was 0.02% or less of the detection limit value. Thereby, even if C is contained in this embodiment, it can be confirmed that most of C exists in the grain boundary phase, and the main phase contains only an amount of inevitable impurities.
- C was analyzed, but N and O can be the same as C.
- the element R is Nd, and a part of Nd may be substituted with Pr.
- the atomic ratio between Nd and Pr is 80:20 to 70:30. From the viewpoint of cost reduction, it is preferable that the ratio of Pr is large and the ratio of Nd is small. However, if the ratio of Nd is smaller than 70 in the above-mentioned atomic ratio, the possibility that the residual magnetic flux density Br will decrease increases.
- the element L can be substituted with Nd and Fe.
- a part of B is substituted with an element L selected from one or more groups selected from the group consisting of Co, Be, Li, Al, and Si.
- element L is preferably Co.
- elements whose wave functions are adapted to the lattice gap or those having an atomic radius smaller than the atomic radius of B can be replaced with B.
- the atomic ratio between B and element L (B: element L) is represented by (1-x): x, where x satisfies 0.01 ⁇ x ⁇ 0.25, and preferably 0.03 ⁇ x ⁇ 0.25.
- x satisfies 0.01 ⁇ x ⁇ 0.25, and preferably 0.03 ⁇ x ⁇ 0.25.
- Nd atoms to B atoms can be reduced by substituting B with a predetermined element.
- the decrease in the number of unpaired electrons in Nd is suppressed, and the magnetic moment of Nd atoms can be improved.
- the element L can be substituted with Nd and Fe.
- the Nd atoms constituting the main phase of the present embodiment have a magnetic moment greater than that of Nd atoms in the Nd 2 Fe 14 B crystal. Magnetic moment is greater than at least 2.70 ⁇ B, preferably 3.75 ⁇ 3.85 ⁇ B, more preferably 3.80 ⁇ 3.85 ⁇ B.
- the R—Fe—B layer 102 includes one or more elements A selected from the group consisting of Tb, Sm, Gd, Ho, and Er.
- the residual magnetic flux density Br can be improved.
- the coercive force H cj can be improved by adding Tb, Ho, or Er.
- both the coercive force H cj and the residual magnetic flux density Br can be improved.
- the element A can be substituted with Fe.
- the elements R, Fe, and B are not substituted with the unsubstituted element L and element A, and other elements contained in the raw material alloy are either of the Nd-Fe-B layers. Includes aspects present on the site. Examples of other elements include known elements that improve the magnetic properties of rare earth permanent magnets.
- an element that forms a grain boundary phase such as Cu, Nb, Zr, Ti, or Ga, or an element that forms a subphase such as O may enter any site of the crystal structure of the main phase.
- the magnetic properties derived from Fe atoms and Nd atoms provide better magnetic properties.
- the magnetic characteristics of this embodiment can be evaluated by the coercive force H cj and the residual magnetic flux density Br.
- the magnetic characteristics of the present embodiment are improved by about 40 to 50% by increasing the number of unpaired electrons, compared with a rare earth permanent magnet made of a conventional Nd 2 Fe 14 B crystal.
- the addition of element A provides a good residual magnetic flux density Br.
- the rare earth permanent magnet of the present embodiment includes a main phase and a grain boundary phase formed between the main phases, and the content of element R with respect to the total weight of the rare earth permanent magnet is 20 to 35% by weight, preferably 22 to 33%. % By weight.
- Nd and Pr are used as the element R, it is preferable that Nd is 15 to 40% by weight and Pr is 5 to 20% by weight.
- the B content is 0.80 to 0.99% by weight, preferably 0.82 to 0.98% by weight.
- the total content of one or more elements selected from the group consisting of Co, Be, Li, Al, Si, Cu, Nb, Zr, Ti and Ga is 0.8 to 2.0% by weight, preferably 0.8 to 1.5% by weight.
- the total content of element A selected from the group consisting of Tb, Sm, Gd, Ho and Er is 2.0 to 10.0% by weight, preferably 2.6 to 5.4% by weight.
- the balance is iron. Since each component has the above-described content, the present embodiment has the predetermined crystal structure described above. Thereby, good residual magnetic flux density Br and coercive force H cj can be obtained.
- this embodiment preferably includes a grain boundary phase between the main phases.
- the grain boundary phase formed between the main phases preferably contains one or more elements selected from the group consisting of Al, Cu, Nb, Zr, Ti, and Ga.
- FIG. 2 is a schematic diagram illustrating an example of a microstructure of one embodiment of the present disclosure.
- 200 is the main phase
- 300 is the grain boundary phase
- 400 is the subphase.
- the spin electrons of the grain boundary phase component pin the spin electrons of the main phase component, and the inversion of the spin of the main phase component is suppressed. That is, the grain boundary phase breaks the magnetic exchange coupling of the main phase. As a result, the coercive force H cj can be improved.
- the content of Al in the total weight of the rare earth permanent magnet is preferably 0.1 to 0.4% by weight, and more preferably 0.2 to 0.3% by weight.
- the Cu content is preferably 0.01 to 0.1% by weight, more preferably 0.02 to 0.09% by weight.
- Zr is added, the content of Zr is preferably 0.004 to 0.04% by weight, and more preferably 0.01 to 0.04% by weight.
- This embodiment combines a high residual magnetic flux density Br, a high coercive force H cj, and a large maximum energy product BH max . Further, the magnetic properties can be further improved by reducing the sintered particle size of the sintered particles including the main phase. When element A contains Ho or the like, it also has excellent heat resistance.
- the rare earth permanent magnet of this embodiment can be manufactured using sintered particles obtained by heat-treating a raw alloy powder of a rare earth permanent magnet.
- Such raw material alloys include element R, one or more elements selected from the group consisting of Co, Be, Li, Al, Si, Cu, Nb, Zr, Ti, and Ga, elements A, Fe,
- the powder particle size D 50 is 2 to 18 ⁇ m, preferably 2 to 13 ⁇ m, more preferably 2 to 9 ⁇ m. When it deviates from the above preferable range, it becomes difficult to obtain a rare earth permanent magnet having a preferable sintered particle diameter.
- the powder particle size means the particle size of the powdery or particulate raw material alloy before the heat treatment step.
- the powder particle size can be measured by a known method using a laser diffraction particle size distribution measuring apparatus.
- the sintered particle size means the particle size of the powdery or particulate raw material alloy after the heat treatment step.
- D 50 is the median diameter in the cumulative distribution of alloy fine particles on a volume basis.
- the sintered particle size D 50 of the rare earth permanent magnet of this embodiment is preferably 2.2 to 20 ⁇ m, more preferably 2.2 to 15 ⁇ m, and even more preferably 2.2 to 10 ⁇ m.
- the sintered particle size D 50 exceeds 20 ⁇ m, the coercive force is remarkably lowered.
- the sintered particle size obtained by heat-treating the above raw material alloy is 110 to 300% of the powder particle size, more specifically 110 to 180%. Therefore, as a result of adjusting the raw material alloy using a known means such as a ball mill, a jet mill or the like until the powder particle size is within a predetermined value range, and molding, magnetizing, degreasing, heat treatment, etc. Sintered particles having a sintered particle size can be obtained.
- the rare earth permanent magnet of this embodiment preferably has a sintered density of 6.0 to 8.0 g / cm 3 .
- the higher the sintered density the larger the residual magnetic flux density Br. Therefore, the higher the sintered density is, the more preferable is 6.0 g / cm 3 or more.
- the sintered density of this embodiment is determined by the powder particle size of the raw material alloy, the processing temperature in the heat treatment step described later, the sintering temperature, and the aging temperature.
- the sintering density is 6.0 to 8.0 g / cm 3 , more preferably 7.0 to 7.9 g / cm 3 , and further preferably 7.2 to 7.7 g / cm 3 depending on the raw material alloy that can be prepared and the conditions of the heat treatment process.
- cm 3 When the sintered density is smaller than 6.0 g / cm 3 , the voids increase in the sintered body, and the residual magnetic flux density Br and further the coercive force H cj are reduced, and the rare earth permanent having the predetermined magnetic characteristics of this embodiment It does not become a magnet.
- the method for producing the rare earth permanent magnet of the present embodiment is not particularly limited as long as the effects of the present embodiment can be obtained.
- a production method including a micronization step, a magnetization step, a degreasing step, and a heat treatment step may be mentioned.
- the rare earth permanent magnet of this embodiment can be produced by cooling the product obtained in each of the above steps to room temperature in the cooling step.
- micronization process In the micronization process, one or more elements R selected from the group consisting of Nd and Pr, and one or more elements selected from the group consisting of Co, Be, Li, Al, Si, Cu, Nb, Zr, Ti, and Ga are selected. And an element A selected from the group consisting of Tb, Sm, Gd, Ho, and Er, Fe, and B are dissolved in the stoichiometric ratio described above to obtain a raw material alloy.
- the stoichiometric ratio blended in the raw material alloy is almost the same as the composition of the final product, which is the main phase compound of this embodiment. Therefore, what is necessary is just to mix
- the raw material alloy is preferably not an amorphous alloy.
- the obtained raw material alloy is roughly pulverized using a ball mill, a jet mill or the like.
- the powder particle size D 50 is preferably 2 to 25 ⁇ m, and other preferred powder particle size D 50 is 2 to 18 ⁇ m.
- the powder particle size D 50 is more preferably 2 to 15 ⁇ m or 2 to 13 ⁇ m.
- the coarsely pulverized raw material alloy particles are dispersed in an organic solvent, and a reducing agent is added.
- a reducing agent is added.
- the total content of Tb, Sm, Gd, Ho and Er in the case of manufacturing using a raw material alloy having a powder particle size D 50 of 2 to 18 ⁇ m is defined as 100%, and Tb, Sm, Gd and Ho Even when the content of Er is reduced by 20 to 30%, the magnetic properties are the same as in the case of 100%.
- the obtained raw material alloy fine particles are compression molded under an orientation magnetic field. Further, in the heat treatment step, the obtained molded body is sintered under vacuum, and then the sintered product is rapidly cooled to room temperature. Subsequently, it is aged in an inert gas atmosphere and cooled to room temperature.
- a main phase and a grain boundary phase are formed by predetermined temperature management and time management.
- the heat treatment conditions are determined based on the melting points of the contained components. That is, all the components are dissolved by raising the treatment temperature to the main phase formation temperature and holding it. Thereafter, in the process of lowering the temperature from the main phase formation temperature to the grain boundary phase formation temperature, the main phase component becomes a solid phase, and the grain boundary phase component starts to precipitate on the solid phase surface.
- a grain boundary phase can be formed by holding at the grain boundary phase formation temperature.
- one or more elements R selected from the group consisting of Nd and Pr, and one or more elements selected from the group consisting of Co, Be, Li, Al, Si, Cu, Nb, Zr, Ti, and Ga are selected.
- this embodiment is an element R selected from one or more groups consisting of Nd and Pr, and a group consisting of Co, Be, Li, Al, Si, Cu, Nb, Zr, Ti, and Ga.
- a raw material alloy containing at least one element selected from the group consisting of Tb, Sm, Gd, Ho, and Er, A, Fe, and B is maintained at the first processing temperature.
- An R-Fe-B layer containing the elements R, Fe, and B, and an Fe layer periodically, and a part of B includes Co, Be, Li, Al, and Si.
- a method for producing a rare earth permanent magnet in which the R-Fe-B layer forms a main phase containing the element A, which is substituted with one or more elements L selected from the group consisting of:
- the method for producing a rare earth permanent magnet of the present embodiment includes a heat treatment step of lowering the treatment temperature to the second treatment temperature after the holding time of the first treatment temperature and holding at the second treatment temperature, and between the main phases. It is also preferable to form a grain boundary phase. That is, the heat treatment process of this embodiment includes a sintering process and may include an aging process.
- the raw material alloy particles are heated to the first treatment temperature and held at the temperature until all the components are dissolved.
- This stage in the heat treatment process is the sintering process of this embodiment, and the first treatment temperature may be rephrased as the sintering temperature.
- the first treatment temperature is set in consideration of the melting points of the elements R, Fe, B, element L, element M, and element A contained in the raw material alloy particles.
- the first treatment temperature 1000 to 1200 ° C is preferable, and 1010 to 1090 ° C is more preferable.
- the first treatment temperature can be set to 1030 to 1080 ° C.
- the first treatment temperature can be set to 1030 to 1060 ° C.
- the heat treatment process shifts to an aging process.
- the main phase component containing at least the elements R, Fe, B, element L, and element A forms a solid phase, and the grains Field phase components begin to precipitate on the solid surface.
- any one or more elements selected from the group consisting of Al, Cu, Nb, Zr, and Ti form a solid phase together with other main phase components, and the other part of the solid phase It precipitates on the surface and forms a grain boundary phase.
- a grain boundary phase and a main phase containing elements common to grain boundary phase components can be formed.
- the second treatment temperature is set based on the grain boundary phase formation temperature.
- temperature control is performed in one or more stages. Therefore, when performing n-stage temperature management, the second treatment temperature is maintained by changing the temperature stepwise from the first aging temperature to the n-th aging temperature.
- the rare earth permanent magnet of this form can be manufactured.
- the rare earth permanent magnet includes one or more elements R selected from the group consisting of Nd and Pr, one or more elements L selected from the group consisting of Co, Be, Li, Al, and Si, and Tb and Sm.
- One or more selected atoms may be replaced with an atom of the element L.
- the rare earth permanent magnet obtained by each of the above steps periodically has an R-Fe-B layer and an Fe layer containing the elements R, Fe, and B, and a part of B is replaced by the element L.
- the sintered particle size of the rare earth permanent magnet crystals obtained by the heat treatment step may be 110 to 300% of the powder particle size of the raw material alloy fine particles before the heat treatment step, and may be 110 to 180%. Therefore, the sintered particle size D 50 is preferably 2.2 to 20 ⁇ m, more preferably 2.2 to 15 ⁇ m, and even more preferably 2.2 to 10 ⁇ m.
- the rare earth permanent magnet of this embodiment obtained by the above steps has a sintered density of 6.0 to 8.0 g / cm 3 , more preferably 7.2 to 7.9 g / cm 3 .
- Example 1 A raw material alloy containing each element with the composition shown in FIG. 3 was roughly pulverized by a ball mill to obtain alloy particles. Thereafter, the alloy particles were dispersed in a solvent. Additives were introduced into the dispersion and stirred to carry out a reduction reaction, whereby alloy particles were made fine.
- the finely divided raw material alloys were filled in molding cavities, respectively, and compression molding, magnetization and degreasing were performed by applying a molding pressure of 2 t / cm 2 and a magnetic field of 19 kOe.
- the obtained molded body was subjected to a heat treatment step under a heat treatment condition shown in FIG. 4 under a vacuum condition of 2 ⁇ 10 1 Torr. After completion of the heat treatment step, it was cooled to room temperature and taken out from the cavity to obtain rare earth permanent magnets of Example 1 and Example 2.
- Example 1 and Example 2 are magnets in which the main phase is formed but the grain boundary phase is not completely formed.
- Comparative Example 1 An alloy of Comparative Example 1 was obtained from a raw material alloy having the composition shown in FIG. Table 1 shows the analysis value of the midpoint of the alloy of Comparative Example 1 by ICP emission spectroscopic analysis.
- the alloy was dispersed in a solvent, an additive was introduced into the dispersion solution, and the mixture was stirred and subjected to a reduction reaction to make the alloy fine particles.
- D 50 of the particle size of the obtained alloy fine powder was 3 to 11 ⁇ m.
- the particle size of the powder was measured using a product equivalent to SALD-2300, a laser diffraction particle size distribution analyzer manufactured by Shimadzu Corporation.
- Comparative Example 1 is a magnet in which a main phase and a grain boundary phase are formed.
- Example 1 Measure the magnetic properties of the rare earth permanent magnets of Example 1, Example 2 and Comparative Example 1 using a TPM-2-08S pulse excitation type magnet measuring device equivalent with a sample temperature variable device manufactured by Toei Kogyo Co., Ltd. did.
- the measurement results are shown in FIG. 4 and FIG. In FIG. 5, the unit [kG] of the residual magnetic flux density Br shown in FIG. 4 is converted to [T].
- the unit [kOe] of the coercive force H cj was converted to [MA / m].
- Example 2 In order to precisely analyze the crystal structure of Example 2, an X-ray diffraction experiment and Rietveld analysis were performed. In the analysis, the existence of Nd 2 Fe 14 B phase and NdO which is one of the subphase components, which are prominent in the crystal, was assumed. Other components such as Sm and Tb contained in Example 2 were not considered in this analysis. The analysis apparatus and analysis conditions used for the analysis are described below. The analysis software was RIETAN-FP.
- Analyzer Rigaku Corporation horizontal X-ray diffractometer SmartLab Analysis conditions: Target: Cu Monochromatic: Symmetric Johansson Ge crystal is used on the incident side (CuK ⁇ 1) Target output: 45kV-200mA Detector: One-dimensional detector (HyPix3000) (Normal measurement): ⁇ / 2 ⁇ scan Slit incidence system: Divergence 1/2 ° Slit light receiving system: 20mm Scanning speed: 1 ° / min Sampling width: 0.01 ° Measurement angle (2 ⁇ ): 10 ° ⁇ 110 °
- FIG. 6 (a) shows the obtained lattice constant of Example 2 in FIG. 6 (a).
- FIG. 6 (b) shows the referenced ICSD and literature values. From the analysis results shown in FIG. 6, it has been identified that the main phase crystal of this embodiment belongs to P4 2 / mnm.
- the model pattern is a pattern obtained by combining the calculation results of the X-ray diffraction pattern of the NdO crystal and an arbitrary Nd 2 Fe 14 B crystal.
- Arbitrary Nd 2 Fe 14 B crystal means that by changing an arbitrary crystal parameter of a known Nd 2 Fe 14 B crystal, an atom occupying any one site existing in the space group is changed to element L (Example 2).
- the fitting index was the s value, and the analysis was advanced so that the s value was close to 1.
- FIG. 7 (a) is an X-ray diffraction pattern of Example 2.
- FIG. FIG. 7B is an example of a model pattern of Nd 2 Fe 14 B.
- FIG. 7 (c) shows an example of a NdO model pattern.
- FIG. 8 shows the fitting results of FIG. 7 (a), FIG. 7 (b), and FIG. 7 (c).
- FIG. 9 shows the result of analysis by a well-fitted one of the plurality of model patterns, and shows the s value and the atomic occupancy in each model pattern.
- “ ⁇ ” means that the atom occupying the site is replaced by the element L atom (Co atom in FIG. 9), and “ ⁇ ” occupies the site. This means that the atoms to be replaced were not replaced by the atoms of the element L (Co atoms in FIG. 9).
- each Co atom site is 0.055 at the 4f site occupied by the B atom, 0.029 at the 4f site occupied by the Nd atom, and the 4c site occupied by the Fe atom. In this case, it is 1.000 and is 0.124 at the 8j site occupied by Fe atoms. That is, the Co atom occupancy at each of the above sites exceeds zero.
- the crystal of Example 2 is an Nd 2 Fe 14 B crystal belonging to P4 2 / mnm, and the first 4f site occupied by B, the second 4f site occupied by Nd, and Fe are respectively Co atoms exist in the occupied 4c site and the first 8j site. That is, a part of the B atom of the first 4f site, a part of the Nd of the second 4f site, a part of the Fe atom of the 4c site, and a part of the Fe atom of the first 8j site, It was confirmed that it was substituted with a Co atom.
- the Co atom occupancy is 0 or less at the 4g site occupied by Nd, the first and second 16k sites occupied by Fe, the second 8j site occupied by Fe, and the 4e site occupied by Fe. It was confirmed that the atoms present at the site were not substituted with Co atoms.
- Examples 3 to 5 and Comparative Example 2 A raw material alloy containing each element with the composition shown in FIG. 10 was coarsely pulverized by a ball mill to obtain alloy particles. Thereafter, the alloy particles were dispersed in a solvent. Additives were introduced into the dispersion and stirred to carry out a reduction reaction, whereby alloy particles were made fine.
- the finely divided raw material alloys were filled in molding cavities, respectively, and compression molding, magnetization and degreasing were performed by applying a molding pressure of 2 t / cm 2 and a magnetic field of 19 kOe.
- the obtained molded body was subjected to a heat treatment step under a heat treatment condition shown in FIG. 17 under a vacuum condition of 2 ⁇ 10 1 Torr. After completion of the heat treatment step, the product was cooled to room temperature and taken out from the cavity to obtain rare earth permanent magnets of Examples 3 to 5.
- Examples 3 to 5 are magnets in which the main phase is formed but the grain boundary phase is not completely formed.
- FIG. 11 and FIG. 12 show the 3D atomic image obtained by 3DAP and its composition ratio.
- FIG. 11 shows the analysis result of the needle-like object of Example 5.
- FIG. 12 shows the analysis result of the needle-like object of Example 3. As shown in FIGS. 11 and 12, it can be seen that in this embodiment, the carbon content in the main phase is remarkably low.
- FIG. 13 is an analysis result of the 3D atomic image including the grain boundary phase of Example 5 and the grain boundary phase profile.
- an Nd 2 Fe 14 B phase was observed, and Tb and Ho as the element A and Co and Al as the element L were recognized.
- the grain boundary phase was Nd rich phase. Further, Cu was precipitated at the interface between the main phase and the grain boundary phase.
- FIG. 14 shows the analysis results of Example 3.
- Each diagram in FIG. 14 is a diagram in which only specific elements are displayed, and which element is displayed is displayed at the bottom of each diagram.
- a white circle ( ⁇ ) indicates Nd.
- Elements that are displayed in combination with Nd are indicated by legends that are not white circles ( ⁇ ).
- Nd is indicated by a white circle ( ⁇ )
- B is indicated by a black circle ( ⁇ ) having the same diameter as the legend of Nd.
- Example 5 is the same analysis result.
- Example 5 the distribution of Nd, Ho, B, and Tb in the atomic layer in the c-axis direction of the crystal including the main phase of Example 3 and Example 5 was measured using Spatial Distribution function, respectively.
- Spatial Distribution function For measurements, see Brian P. Geiser, Thomas F. Kelly, David J. Larson, Jason Schneir and Jay P. Roberts, “Spatial Distribution Maps for Atom Probe Tomography”, Microscopy and Microanalysis, 437 (447) I went there.
- the measurement result of Example 5 is shown in FIG. 15, and the measurement result of Example 3 is shown in FIG.
- Nd, Ho, B, and Tb all have a peak at a multiple of 0.6 nm.
- the substitution of element B for element B occurs in this embodiment.
- Comparative Example 2 was obtained from a raw material alloy having the composition shown in FIG. Table 2 shows the analysis values of the alloy of Comparative Example 2 by ICP emission spectroscopic analysis.
- the alloy was dispersed in a solvent, and an additive was introduced into the dispersion solution and stirred to perform a reduction reaction, whereby the alloy was made into fine particles.
- D 50 of the particle size of the obtained alloy fine powder was 3 to 11 ⁇ m.
- the particle size was measured with a laser diffraction particle size distribution measuring device SALD-2300 or equivalent manufactured by Shimadzu Corporation.
- the finely divided raw material alloy was filled into a molding cavity, and compression molding and magnetization were performed by applying a magnetic field of 19 kOe with a molding pressure of 2 t / cm 2 .
- the obtained molded body was subjected to a heat treatment step in a 2 ⁇ 10 1 Torr Ar gas atmosphere under the heat treatment conditions shown in FIG. After completion of the heat treatment step, the product was cooled to room temperature and taken out from the cavity to obtain a rare earth permanent magnet of Comparative Example 2.
- Comparative Example 2 is a magnet in which a main phase and a grain boundary phase are formed.
- Example 3 Measure the magnetic properties of the rare earth permanent magnets of Example 3 to Example 5 and Comparative Example 2 using a TPM-2-08S pulse excitation type magnet measuring device equivalent with a sample temperature variable device manufactured by Toei Kogyo Co., Ltd. did.
- the measurement results are shown in FIG. 17 and FIG. In FIG. 18, the unit [kG] of the residual magnetic flux density Br shown in FIG. 17 is converted to [T].
- the unit [kOe] of the coercive force H cj was converted to [MA / m].
- the residual magnetic flux density Br can be improved by suppressing the B content and replacing it with Co. Since the residual magnetic flux density Br is proportional to the saturation magnetization, the saturation magnetization of the present embodiment was measured, and the improvement effect of the residual magnetic flux density Br of the present embodiment was confirmed from the measurement result.
- the magnetic field-magnetization curves of Reference Example 1 and Reference Example 2 were measured using a Lake® Shore® Cryotronics® 7400® Series® VSM. As shown in Table 3, the saturation magnetization of Reference Example 1 was 40.1557 (emu / g). The saturation magnetization of Reference Example 2 was 41.0184 (emu / g). That is, it is shown that the reference example 2 having a larger Co substitution amount than the reference example 1 has a larger saturation magnetization and a larger residual magnetic flux density Br.
- both the residual magnetic flux density Br and the coercive force Hcj can be improved by substituting B with the element L and providing the main phase containing the element A in the R—Fe—B layer.
- the improvement of the magnetic characteristics is as illustrated in FIGS.
- the rare earth permanent magnet of this embodiment has a high magnetic moment and has good magnetic properties. Rare earth permanent magnets contribute to miniaturization, weight reduction, and cost reduction of electric motors, offshore wind power generators, industrial motors and the like.
- the magnetic properties of a rare earth permanent magnet having a main phase containing Nd, Fe, and B can be improved.
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Abstract
Description
本形態の希土類永久磁石の製造方法は、本形態の作用効果を得られる限り、特に制限されない。好ましい本形態の製造方法としては、微粒子化工程、着磁工程、脱脂工程、熱処理工程とを含む製造方法が挙げられる。上記の各工程により得られた生成物を冷却工程で室温になるまで冷却させて、本形態の希土類永久磁石を製造できる。
微粒子化工程では、NdとPrとからなる群から一種以上選択される元素Rと、CoとBeとLiとAlとSiとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素と、TbとSmとGdとHoとErとからなる群から一種以上選択される元素Aと、Feと、Bとを上記に説明する化学量論比で溶解させ、原料合金を得る。
着磁工程においては、得られた原料合金微粒子を配向磁場下で圧縮成型する。さらに熱処理工程で、得られた成形体を真空下で焼結後、焼結物を室温まで急冷する。続いて不活性ガス雰囲気中で時効処理し、室温まで冷却する。
熱処理工程においては、所定の温度管理と時間管理とにより主相や粒界相が形成される。熱処理条件は、含有成分の融点に基づいて決定される。すなわち処理温度を主相形成温度まで昇温させて保持することで全ての含有成分を溶解させる。その後、主相形成温度から粒界相形成温度まで温度を低下させる過程で主相成分が固相となり、粒界相成分が固相表面に析出し始める。粒界相形成温度で保持することにより粒界相を形成できる。
図3に示す組成で各元素を含有する原料合金をボールミルで粗粉砕し、合金粒子を得た。その後合金粒子を溶媒に分散させた。分散溶液に、添加剤を導入して撹拌して還元反応を行い、合金粒子を微粒子化した。
図3に示す組成で各元素を含有する原料合金から、急冷凝固装置により、比較例1の合金を得た。表1は、比較例1の合金のICP発光分光分析による中点の分析値である。
分析条件:
ターゲット:Cu
単色化:入射側に対称Johansson 型Ge 結晶を使用(CuKα1)
ターゲット出力:45kV-200mA
検出器:1次元検出器(HyPix3000)
(通常測定):θ/2θ走査
スリット入射系:発散1/2°
スリット受光系:20mm
走査速度:1°/min
サンプリング幅:0.01°
測定角度(2θ):10°~110°
図10に示す組成で各元素を含有する原料合金をボールミルで粗粉砕し、合金粒子を得た。その後合金粒子を溶媒に分散させた。分散溶液に、添加剤を導入して撹拌して還元反応を行い、合金粒子を微粒子化した。
実施例3と実施例5との希土類永久磁石の主相の結晶構造を観察するため、サンプル用に3DAP解析に用いる針状物を、下記の方法により加工した。まず実施例のサンプルは、集束イオンビーム加工観察装置(Forcused Ion Beam、FIB)にセットされた後、磁化容易方向を含む面を観察するための溝が加工された。溝を加工することで現れたサンプルの磁化容易方向を含む面に、電子線を照射した。照射により試料から放射される反射電子線をSEMで観察することで、主相(粒内)を特定した。特定された主相を、3DAPにより解析するため針状に加工した。
装置名 : LEAP3000XSi (AMETEK社製)
測定条件: レーザパルスモード(レーザ波長=532nm)
レーザパワー=0.5nJ、試料温度=50K
図10に示す組成で各元素を含有する原料合金から、急冷凝固装置により、比較例2を得た。表2は、比較例2の合金のICP発光分光分析による分析値である。
本形態は、Bの含有量を抑制しCoで置換させることで残留磁束密度Brを向上できる。残留磁束密度Brは飽和磁化と比例するため、本形態の飽和磁化を測定し、その測定結果から本形態の残留磁束密度Brの向上効果を確認した。
101 Fe層
102 R-Fe-B層
200 主相
300 粒界相
400 副相
Claims (12)
- NdとPrとからなる群から一種以上選択される元素Rと、CoとBeとLiとAlとSiとからなる群から一種以上選択される元素Lと、TbとSmとGdとHoとErとからなる群から一種以上選択される元素Aと、Feと、Bとを含有する主相を備え、前記主相を形成する結晶がP42/mnmに属し、前記結晶の4fサイトを占有するB原子の一部が前記元素Lの原子と置換されてなる希土類永久磁石。
- P42/mnmに属する前記結晶の4fサイトを占有するNd原子と、4cサイトを占有するFe原子と、8jサイトを占有するFe原子とからなる群から一種以上選択される原子の一部が、前記元素Lの原子と置換されてなる請求項1に記載される希土類永久磁石。
- NdとPrとからなる群から一種以上選択される元素Rと、CoとBeとLiとAlとSiとからなる群から一種以上選択される元素Lと、TbとSmとGdとHoとErとからなる群から一種以上選択される元素Aと、Feと、Bとを含有する主相を備える希土類永久磁石。
- 前記主相を形成する結晶が、NdとPrとからなる群から一種以上選択される前記元素RとFeとBとを含むR-Fe-B層と、Fe層とを周期的に有し、B原子の一部が、前記元素Lの原子で置換され、前記R-Fe-B層が前記元素Aの原子を含む、請求項3に記載される希土類永久磁石。
- 前記主相と主相間に形成される粒界相とを備える前記希土類永久磁石であって、前記希土類永久磁石の総重量に対する前記元素Rの含有量が20~35重量%であり、Bの含有量が0.80~0.99重量%であり、CoとBeとLiとAlとSiとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素の含有量の合計が、0.8~2.0重量%であり、TbとSmとGdとHoとErとからなる群から一種以上選択される前記元素Aの含有量の合計が2.0~10.0重量%である、請求項1ないし請求項4のいずれか一項に記載される希土類永久磁石。
- 主相間に形成される粒界相が、AlとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素を含有する請求項1ないし請求項4のいずれか一項に記載される希土類永久磁石。
- 粉末粒径のD50が2~18μmである合金粒子を用いて製造された、請求項1ないし請求項4のいずれか一項に記載される希土類永久磁石。
- 焼結密度が、6~8g/cm3である、請求項1ないし請求項4のいずれか一項に記載される希土類永久磁石。
- 請求項1ないし請求項4のいずれか一項に記載される前記希土類永久磁石の原料合金であって、前記元素Rと、CoとBeとLiとAlとSiとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素と、前記元素Aと、Feと、Bとを含み、粉末粒径のD50が2~18μmである合金粒子。
- NdとPrとからなる群から一種以上選択される元素Rと、CoとBeとLiとAlとSiとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素と、TbとSmとGdとHoとErとからなる群から一種以上選択される元素Aと、Feと、Bとを含有する原料合金を、第一の処理温度で保持する熱処理工程を含み、
前記元素Rと、CoとBeとLiとAlとSiとからなる群から一種以上選択される元素Lと、前記元素Aと、Feと、Bとを含有する主相を備え、主相を形成する結晶がP42/mnmに属し、前記結晶の4fサイトを占有するB原子の一部が前記元素Lの原子と置換されてなる希土類永久磁石の製造方法。 - NdとPrとからなる群から一種以上選択される元素Rと、CoとBeとLiとAlとSiとCuとNbとZrとTiとGaとからなる群から一種以上選択される元素と、TbとSmとGdとHoとErとからなる群から一種以上選択される元素Aと、Feと、Bとを含有する原料合金を、第一の処理温度で保持する熱処理工程を含み、
前記元素RとFeとBとを含むR-Fe-B層と、Fe層とを周期的に有し、B原子の一部が、CoとBeとLiとAlとSiとからなる群から一種以上選択される元素Lの原子で置換され、R-Fe-B層が前記元素Aの原子を含む主相を形成する、希土類永久磁石の製造方法。 - 前記第一の処理温度の保持時間経過後、処理温度を第二の処理温度まで低下させ、前記第二の処理温度で保持する熱処理工程を含み、前記主相間に粒界相を形成する請求項10または請求項11に記載される希土類永久磁石の製造方法。
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