WO2015030231A1 - R-t-b系焼結磁石の製造方法 - Google Patents
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- 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
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- 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
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- 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
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- 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 disclosure relates to a method for manufacturing an RTB-based sintered magnet.
- RTB-based sintered magnet having an R 2 T 14 B type compound as a main phase (R is composed of a light rare earth element RL and a heavy rare earth element RH, where RL is Nd and / or Pr, RH is Dy, Tb, At least one of Gd and Ho, T is a transition metal element and must contain Fe) is known as the most powerful magnet among permanent magnets, and is used for hybrid cars, electric cars, and home appliances. Used in various motors.
- the RTB -based sintered magnet has a reduced coercive force H cJ (hereinafter sometimes simply referred to as “H cJ ”) at high temperatures, causing irreversible thermal demagnetization. Therefore, especially when used for a hybrid vehicle or an electric vehicle motor, it is required to maintain a high HcJ even at high temperatures. In order not to cause irreversible demagnetization at high temperatures, it is required to obtain higher HcJ at room temperature.
- H cJ coercive force
- Dy has problems such as unstable supply or price fluctuations due to the limited production area. Therefore, there is a demand for a technique for improving the HcJ of the RTB -based sintered magnet without using a heavy rare earth element such as Dy as much as possible (with the least amount of use).
- the amount of B is made lower than that of a normal RTB-based alloy, and at least one metal element M selected from Al, Ga, and Cu is contained, thereby allowing R 2 T 17
- the coercive force is suppressed while the content of Dy is suppressed by sufficiently securing the volume fraction of the transition metal rich phase (R 6 T 13 M) generated by using the R 2 T 17 phase as a raw material.
- R 6 T 13 M transition metal rich phase
- Patent Document 2 as well as defining the effective rare earth content and effective boron content, Co, a high coercivity H cJ alloy containing Cu and Ga as compared with the conventional alloys with the same remanence B r It is described that it has.
- heat treatment is performed on a sintered body after sintering at 400 ° C. to 550 ° C.
- R-T-B rare earth sintered magnet according to the Patent Documents 1 and 2 R, B, Ga, since the content of Cu is not optimal, not obtain a high B r and high H cJ.
- the present disclosure has been made to solve the above problems, while suppressing the content of Dy, provides a method for producing R-T-B based sintered magnet having a high B r and high H cJ For the purpose.
- Aspect 1 of the present invention is represented by the following formula (1): uRwBxGayCuzAlqM (100-uwxxyzq) T (1) (R is composed of light rare earth element RL and heavy rare earth element RH, RL is Nd and / or Pr, RH is at least one of Dy, Tb, Gd and Ho, T is a transition metal element and must contain Fe.
- RH is 5% by mass or less of the RTB-based sintered magnet, and satisfies the following formulas (2) to (5): 0.20 ⁇ x ⁇ 0.70 (2) 0.07 ⁇ y ⁇ 0.2 (3) 0.05 ⁇ z ⁇ 0.5 (4) 0 ⁇ q ⁇ 0.1 (5)
- the oxygen content (mass%) of the RTB-based sintered magnet is ⁇
- the nitrogen content (mass%) is ⁇
- carbon content (mass%) is ⁇
- v u ⁇ (6 ⁇ + 10 ⁇ + 8 ⁇ )
- Aspect 2 of the present invention is the method for producing an RTB-based sintered magnet according to aspect 1, wherein the temperature of the low-temperature heat treatment step is 480 ° C. or higher and 550 ° C. or lower.
- Aspect 3 of the present invention is a method for producing an RTB-based sintered magnet according to aspect 1 or 2, wherein the obtained RTB-based sintered magnet has an oxygen content of 0.15% by mass or less. is there.
- Aspect 5 of the present invention is the method for producing an RTB-based sintered magnet according to aspect 4, wherein the temperature of the low-temperature heat treatment step is 480 ° C. or higher and 550 ° C. or lower.
- Aspect 6 of the present invention is a method for producing an RTB-based sintered magnet according to aspect 4 or 5, wherein the obtained RTB-based sintered magnet has an oxygen content of 0.15% by mass or less. It is.
- FIG. 1 is an explanatory diagram showing ranges of v and w in one embodiment of the present invention.
- FIG. 2 is an explanatory diagram showing ranges of v and w in another aspect of the present invention.
- FIG. 3 is an explanatory diagram showing a relative relationship between the range shown in FIG. 1 and the range shown in FIG.
- FIG. 4 is an explanatory diagram in which the values of v and w of the example sample and the comparative example sample according to “ ⁇ Example 1>” are plotted in FIG. 1.
- the present inventors have optimized the composition as shown in the first aspect or the fourth aspect of the present invention, and the RTB-based sintering of the optimized composition. relative sintered magnet material, by performing a specific heat treatment, in which the R-T-B based sintered magnet having a high B r and high H cJ was found that the resulting.
- R-T-B based sintered magnet can be improved B r by increasing the existence ratio of R 2 T 14 B type compound as the main phase.
- R amount, T amounts although the B amount should brought close to the stoichiometric ratio of R 2 T 14 B type compound, R 2 T 14 B-type
- the amount of B for forming the compound is lower than the stoichiometric ratio, a soft magnetic R 2 T 17 phase is precipitated at the grain boundary, and H cJ is rapidly decreased.
- an RT-Ga phase is generated instead of the R 2 T 17 phase, and a decrease in H cJ can be prevented.
- the RTB-Ga phase also has some magnetism, and the first grain boundary (hereinafter referred to as “two-grain grain boundary”) existing between the two main phases in the RTB-based sintered magnet.
- the second grain boundaries existing between three or more main phases (hereinafter sometimes referred to as “triple grain boundaries”), especially HcJ
- the R-Ga phase and the R-Ga-Cu phase which are considered to be less magnetic than the RT-Ga phase at the grain boundary, are generated. It turns out that it may have been.
- the HcJ is improved by the presence of the R—Ga phase and the R—Ga—Cu phase at the two-grain boundary of the RTB -based sintered magnet.
- the R—Ga phase and the R—Ga—Cu phase in order to generate the R—Ga phase and the R—Ga—Cu phase, and in order to eliminate the R 2 T 17 phase, it is necessary to generate the R—T—Ga phase, but a high H cJ is obtained. Assumed that it was necessary to keep the production amount low. If the generation of the RT-Ga phase can be suppressed as much as possible while generating the R—Ga phase and the R—Ga—Cu phase, especially at the two-grain grain boundary, the H cJ can be further improved. Assumed.
- the precipitation amount of the R 2 T 17 phase can be reduced by setting the R amount and the B amount within an appropriate range.
- part of R is consumed in combination with oxygen, nitrogen and carbon in the manufacturing process of RTB-based sintered magnets, so it is actually used for the R 2 T 17 phase and RT-Ga phase.
- the amount of R changes in the manufacturing process.
- the R 2 T 17 phase and the RT It was found difficult to suppress the amount of -Ga phase produced. Therefore, as a result of repeated studies, as described in the first aspect or the fourth aspect, from the R amount (u), the oxygen amount (mass%) in the RTB-based sintered magnet is changed to ⁇ , and the nitrogen amount (mass%).
- the specific value formula (10) by containing the formulas (8) and (9) of the aspect 1 of the present invention or the formulas (12) and (9) of the aspect 4 of the present invention, It is considered that while the RT-Ga phase is generated, the generation amount can be suppressed low.
- the RTB-Ga phase is generated in the range of 440 ° C. or higher and lower than 730 ° C.
- the temperature is 440 ° C. or higher and 550 ° C. or lower, the amount of RT—Ga phase generated is suppressed, and when it exceeds 550 ° C., the RT—Ga phase is likely to be generated excessively.
- the RT-Ga phase is not generated below 440 ° C. and above 730 ° C.
- the RTB-based sintering having the specific composition is used. It is necessary to perform heat treatment for heating the magnet material to a temperature of 440 ° C. or higher and 550 ° C. or lower.
- the molded body in order to prevent oxidation of the molded body and to equalize the temperature at the time of sintering, the molded body may be stored in a metal container (sintered pack) and sintered. In many cases, it is difficult to control the cooling rate after sintering.
- the RT—Ga phase of the two-grain grain boundary generated after sintering by the high-temperature heat treatment process disappears, and cooling is performed at such a rate that the disappeared RT-Ga phase is not generated again.
- the object to be heat treated is an RTB-based sintered magnet material after sintering, so there is no need to use a metal container to prevent oxidation, and the cooling rate can be controlled. It is. Then, the RTB-based sintered magnet material that has undergone the high-temperature heat treatment process in which the RTB-Ga phase has disappeared is subjected to the low-temperature heat treatment process, thereby generating the RTB-Ga phase at the grain boundary. It is considered that the R—Ga phase and the R—Ga—Cu phase can be generated while suppressing as much as possible.
- Patent Document 1 since the oxygen content, the nitrogen content, and the carbon content are not considered with respect to the R content, it is difficult to suppress the generation amount of the R 2 T 17 phase or the R—T—Ga phase. is there. In the first place, the technique described in Patent Document 1 improves HcJ by promoting the generation of the RT—Ga phase, and there is no technical idea of suppressing the amount of RT—Ga phase generated. Therefore, Patent Document 1 contains R, B, Ga, Cu, and Al at an optimal ratio capable of generating the R—Ga—Cu phase while suppressing the amount of R—T—Ga phase generated. Orazu, therefore, high B r and high H cJ is considered not obtained.
- Patent Document 2 the values of the oxygen content, the nitrogen content, and the carbon content are taken into consideration.
- the generation of the R 2 T 17 phase is suppressed and the Ga-containing phase (the R— Since it is described that HcJ is improved by generating (which is considered to correspond to a T—Ga phase), the technical idea of suppressing the amount of R—T—Ga phase generated as in Patent Document 1 is described. There is no. Further, both Patent Documents 1 and 2 do not have a technical idea of generating an R—Ga phase and an R—Ga—Cu phase while suppressing the generation of an RT—Ga phase as much as possible at a two-grain grain boundary.
- the RTB-based sintered magnet before the high-temperature heat treatment process is called “RTB-based sintered magnet material”, and the RTB after the high-temperature heat treatment process and before the low-temperature heat treatment process.
- Type sintered magnet is called “RTB type sintered magnet material after high temperature heat treatment process”
- RTB type sintered magnet after low temperature heat treatment process is called “RTB type sintered magnet material”
- a metal or alloy of each element is prepared so that the RTB-based sintered magnet material has the composition described in detail below.
- a flaky raw material alloy is produced using a strip casting method or the like.
- an alloy powder is prepared from the flaky raw material alloy, and the RTB-based sintered magnet material is prepared by molding and sintering the alloy powder. Production, molding, and sintering of the alloy powder are performed as follows as an example.
- the obtained flaky raw material alloy is pulverized with hydrogen to obtain coarsely pulverized powder of, for example, 1.0 mm or less.
- the coarsely pulverized powder is finely pulverized by a jet mill or the like, so that, for example, finely pulverized powder (alloy powder) having a particle size D50 (volume-based median diameter obtained by measurement by a laser diffraction method using an air flow dispersion method) of 3 to 7 ⁇ m )
- the alloy powder one kind of alloy powder (single alloy powder) may be used, or a so-called two alloy method may be used in which an alloy powder (mixed alloy powder) is obtained by mixing two or more kinds of alloy powder.
- the alloy powder may be prepared so as to have the composition of the present invention by using a known method.
- a known lubricant may be used as an auxiliary agent for the coarsely pulverized powder before jet mill pulverization, and the alloy powder during and after jet mill pulverization.
- molding is performed in a magnetic field using the obtained alloy powder to obtain a compact.
- Molding in a magnetic field is a dry molding method in which a dry alloy powder is inserted into a mold cavity and molded, and a slurry in which the alloy powder is dispersed is injected into the mold cavity, and the slurry dispersion medium is discharged.
- Any known forming method in a magnetic field may be used, including a wet forming method of forming while forming. Then, the RTB-based sintered magnet material is obtained by sintering the compact.
- a known method can be used to sinter the molded body.
- the atmosphere gas is preferably an inert gas such as helium or argon.
- composition of the RTB-based sintered magnet material is represented by the formula: uRwBxGayCuzAlqM (100-uwxyzzq) T (1)
- R is a light rare earth element RL
- RL is Nd and / or Pr
- RH is at least one of Dy
- Tb Gd and Ho
- T is a transition metal element and must contain Fe
- M is Nb and / or Zr, which contains unavoidable impurities, u, w, x, y, z, q and 100-uwxyzzq represent mass%).
- the RH is 5% by mass or less of the RTB-based sintered magnet, 0.20 ⁇ x ⁇ 0.70 (2) 0.07 ⁇ y ⁇ 0.2 (3) 0.05 ⁇ z ⁇ 0.5 (4) 0 ⁇ q ⁇ 0.1 (5),
- the oxygen content (mass%) of the RTB-based sintered magnet is ⁇
- the nitrogen content (mass%) is ⁇
- the carbon content (mass%) is ⁇
- v u ⁇ (6 ⁇ + 10 ⁇ + 8 ⁇ )
- v and w are 50w-18.5 ⁇ v ⁇ 50w-14 (6) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 (7) Satisfied,
- 0.20 ⁇ x ⁇ 0.40 v and w are 50w-18.5 ⁇ v ⁇ 50w-15.5 (8) ⁇ 12.5w + 39.125 ⁇ v ⁇ ⁇ 62.5w + 86.125 (9)
- R is composed of light rare earth element RL and heavy rare earth element RH, RL is Nd and / or Pr, RH is at least one of Dy, Tb, Gd and Ho, T is a transition metal element and must contain Fe.
- M is Nb and / or Zr, contains unavoidable impurities, and u, w, x, y, z, q and 100-uwxyzz represent mass%).
- the RH is 5% by mass or less of the RTB-based sintered magnet, 0.20 ⁇ x ⁇ 0.70 (2) 0.07 ⁇ y ⁇ 0.2 (3) 0.05 ⁇ z ⁇ 0.5 (4) 0 ⁇ q ⁇ 0.1 (5),
- the oxygen content (mass%) of the RTB-based sintered magnet is ⁇
- the nitrogen content (mass%) is ⁇
- the carbon content (mass%) is ⁇
- v u ⁇ (6 ⁇ + 10 ⁇ + 8 ⁇ )
- v and w are 50w-18.5 ⁇ v ⁇ 50w-16.25 (11) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 (7) Satisfied
- 0.20 ⁇ x ⁇ 0.40 v and w are 50w-18.5 ⁇ v ⁇ 50w-17.0 (12) ⁇ 12.5w + 39.125 ⁇ v ⁇ ⁇ 62.5w +
- the RTB-based sintered magnet material of the present invention may contain inevitable impurities.
- the effects of the present invention can be achieved even if inevitable impurities normally contained in didymium alloy (Nd—Pr), electrolytic iron, ferroboron, and the like are contained.
- Inevitable impurities may include, for example, trace amounts of La, Ce, Cr, Mn, Si, and the like.
- R is composed of a light rare earth element RL and a heavy rare earth element RH, where RL is Nd and / or Pr, RH is Dy, Tb, Gd and It is at least one of Ho, and RH is set to 5% by mass or less of the RTB-based sintered magnet. Because the present invention can obtain a high B r and high H cJ without using a heavy rare-earth element, it can be reduced the amount of RH even be asked a higher H cJ.
- T is a transition metal element and necessarily contains Fe.
- An example of the transition metal element other than Fe is Co.
- the amount of substitution of Co is preferably 2.5% by mass or less, and if the amount of substitution of Co exceeds 10% by mass, Br is lowered, which is not preferable. Further, a small amount of V, Cr, Mn, Mo, Hf, Ta, W, or the like may be contained. B is boron. It is widely known that when trying to obtain a specific rare earth element, other types of rare earth elements that are not intended as impurities are included as impurities during the refining process.
- R in the RTB-based sintered magnet according to one aspect of the present invention is composed of a light rare earth element RL and a heavy rare earth element RH, where RL is Nd and / or Pr, RH is Dy, It is at least one of Tb, Gd, and Ho, and RH is made to be 5% by mass or less of the RTB-based sintered magnet.
- R is Nd, Pr, Dy, Tb, Gd and It does not completely exclude the case where rare earth elements other than Ho are included, and it means that rare earth elements other than Nd, Pr, Dy, Tb, Gd and Ho may be contained as long as they are in an impurity level. ing.
- the Ga content (x) is 0.20% by mass or more and 0.70% by mass or less. However, when Ga is 0.40 mass% or more and 0.70 mass% or less and when it is 0.20 mass% or more and less than 0.40 mass%, the ranges of v and w are different. This will be described in detail below.
- v and w are in the relationship of the following formulas (6) and (7). 50w-18.5 ⁇ v ⁇ 50w-14 (6) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 (7)
- FIG. 1 shows the scope of the present invention for v and w that satisfies the above equations (6) and (7).
- v is a value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from the R amount (u), where the oxygen amount (mass%) is ⁇ , the nitrogen amount (mass%) is ⁇ , and the carbon amount (mass%) is ⁇ . It is a quantity value.
- Equation (6) that is, 50w-18.5 ⁇ v ⁇ 50w-14, is a straight line including points A and B (a straight line connecting points A and B) and a straight line including points C and D (points) in FIG. (A straight line connecting C and point D), and formula (7), that is, ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125, points D, F, B, and G
- This is a range between the straight line including the straight line including the point C, the point E, the point A, and the point G.
- Regions 1 and 2 regions surrounded by point A, point B, point D, and point C) that satisfy both of these are the ranges according to one aspect of the present invention.
- the amount of Fe is insufficient. If the amount of Fe is insufficient, R and B are left over. As a result, it is considered that the R 1 Fe 4 B 4 phase is easily generated without generating the RT-Ga phase. As a result, the amount of R-Ga phase and R-Ga-Cu phase produced is reduced, and high HcJ cannot be obtained. Further, the region 30 (the region above the straight line including the points C and D) deviated from the range of the regions 1 and 2 has too much v and too little w. Although the phase and the R—Ga—Cu phase are produced, the abundance ratio of the main phase becomes low, and high Br cannot be obtained.
- the region 40 (the region excluding the regions 1 and 2 from the region surrounded by the points C, D, and G) deviated from the regions 1 and 2 has a small amount of R and a large amount of B. Although the abundance ratio is high, almost no R—T—Ga phase is generated, and the amount of R—Ga phase and R—Ga—Cu phase produced is small, so that high H cJ cannot be obtained.
- x is in the range of the following formula (10) according to v and w. ⁇ (62.5w + v ⁇ 81.625) /15+0.5 ⁇ x ⁇ (62.5w + v ⁇ 81.625) /15+0.8 (10)
- x is in the range of the following formula (10) according to v and w.
- ⁇ (62.5w + v ⁇ 81.625) /15+0.5 ⁇ x ⁇ (62.5w + v ⁇ 81.625) /15+0.8 (10)
- v and w are further set to the relationship of the following formulas (8) and (9).
- 50w-18.5 ⁇ v ⁇ 50w-15.5 (8) ⁇ 12.5w + 39.125 ⁇ v ⁇ ⁇ 62.5w + 86.125 (9)
- FIG. 2 shows the scope of the present invention for v and w satisfying the equations (8) and (9).
- Expression (8) that is, 50w-18.5 ⁇ v ⁇ 50w ⁇ 15.5 is a range between the straight line including the point A and the point L and the straight line including the point J and the point K in FIG.
- FIG. 3 shows the case of FIG. 1 (when the Ga content is 0.40 mass% or more and 0.70 mass% or less) and FIG. 2 (when the Ga content is 0.20 mass% or more and less than 0.40 mass%). (A relative relationship between the range shown in FIG. 1 and the range shown in FIG. 2).
- v and w are in the relationship of the following formulas (11) and (7). 50w-18.5 ⁇ v ⁇ 50w-16.25 (11) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 (7)
- FIG. 1 shows the scope of the present invention of v and w satisfying the above formulas (11) and (7).
- Expression (11), that is, 50w-18.5 ⁇ v ⁇ 50w-16.25 is a range sandwiched between a straight line including point A and point B and a straight line including point E and point F
- expression (7) That is, ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 is sandwiched between a straight line including point D and point F, point B and point G, and a straight line including point C and point E, point A and point G. It is a range.
- region 2 area
- v and w are in the relationship of the following formulas (12) and (9). 50w-18.5 ⁇ v ⁇ 50w-17.0 (12) ⁇ 12.5w + 39.125 ⁇ v ⁇ ⁇ 62.5w + 86.125 (9)
- FIG. 2 shows a range that satisfies the above equations (12) and (9).
- Expression (12) that is, 50w-18.5 ⁇ v ⁇ 50w ⁇ 17.0 is a range sandwiched between a straight line including point A and point L and a straight line including point H and point I
- expression (9) That is, ⁇ 12.5w + 39.125 ⁇ v ⁇ ⁇ 62.5w + 86.125 is a range sandwiched between a straight line including the point K and the point I and the point L and a straight line including the point J, the point H and the point A.
- region 4 area
- FIG. 3 shows a relative range of FIG. 1 (Ga is 0.40 mass% or more and 0.70 mass% or less) and FIG. 2 (Ga is 0.20 mass% or more and less than 0.40 mass%). Indicates the positional relationship.
- x is ⁇ (62.5w + v ⁇ 81.625) /15+0.5 ⁇ x ⁇ ( 62.5w + v ⁇ 81.625) /15+0.8, the amount of RT-Ga phase can be secured while v can be lowered and w can be increased. The ratio is not lowered, and a higher Br can be obtained.
- Cu is contained in an amount of 0.07% by mass to 0.2% by mass. If the Cu content is less than 0.07% by mass, the R—Ga phase and the R—Ga—Cu phase are difficult to be generated at the two-grain grain boundaries, and high H cJ may not be obtained. Moreover, when it exceeds 0.2 mass%, since there is too much content of Cu, there exists a possibility that it becomes impossible to sinter.
- the Cu content is more preferably 0.08% by mass or more and 0.15% by mass or less.
- Al 0.05 mass% or more and 0.5 mass% or less
- HcJ HcJ
- Al may be contained in an amount of 0.05% by mass or more as an unavoidable impurity in the production process, but the total amount of the unavoidable impurity and the amount intentionally added is 0.05% by mass or more. .5% by mass or less.
- an RTB-based sintered magnet contains Nb and / or Zr to suppress abnormal grain growth during sintering.
- Nb and / or Zr may be contained in a total amount of 0.1% by mass or less. By the content of Nb and / or Zr is present unwanted Nb and Zr exceeds 0.1 mass% in total, there is a possibility that the volume ratio of the main phase is lowered B r drops.
- the oxygen content (mass%), the nitrogen content (mass%), and the carbon content (mass%) are the content in the RTB-based sintered magnet (that is, RTB). Content when the mass of the entire sintered system magnet is 100% by mass).
- the present invention uses a value (v) obtained by subtracting the amount consumed by combining with oxygen, nitrogen and carbon from the amount of R (u) by the method described below. By using v, it is possible to adjust the production amount of the R 2 T 17 phase and the RT-Ga phase.
- the v is determined by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from the R amount (u), where ⁇ is the oxygen amount (% by mass), ⁇ is the nitrogen amount (% by mass), and ⁇ is the carbon amount (% by mass).
- 6 ⁇ is defined because R having a mass approximately six times that of oxygen is consumed as an oxide, assuming that an oxide of R 2 O 3 is mainly produced as an impurity.
- 10 ⁇ is defined by the fact that R having a mass approximately 10 times that of nitrogen is consumed as nitride, assuming that RN nitride is mainly produced.
- 8 ⁇ is defined because R, which is approximately eight times the mass of carbon, is consumed as carbides, assuming that R 2 C 3 carbides are mainly produced.
- the amount of oxygen (mass%), the amount of nitrogen (mass%), and the amount of carbon (mass%) are determined by considering the raw alloy used, the production conditions, etc.
- the amount of oxygen, the amount of nitrogen, and the amount of carbon of the magnet can be predicted.
- the oxygen amount is a gas melting-infrared absorption method
- the nitrogen amount is a gas melting-heat conduction method
- the carbon amount is a combustion-infrared absorption method
- the oxygen content, nitrogen content, and carbon content are obtained by measurement using the above-described gas analyzer, whereas those of R, B, Ga, Cu, Al, M, and T shown in Formula (1) are used.
- those of R, B, Ga, Cu, Al, M, and T shown in Formula (1) are used.
- u, w, x, y, z, q and 100-uwxxyzq, u, w, x, y, z and q are Measurement may be performed using inductively coupled plasma emission spectroscopy (ICP emission spectroscopy). Further, 100-uwxyzzq may be obtained by calculation using measured values of u, w, x, y, z, and q obtained by ICP emission spectroscopy.
- ICP emission spectroscopy inductively coupled plasma emission spectroscopy
- Formula (1) defines that the total amount of elements that can be measured by ICP emission spectrometry is 100% by mass.
- the amount of oxygen, the amount of nitrogen and the amount of carbon cannot be measured by ICP emission spectroscopy. Therefore, in the embodiment according to the present invention, u, w, x, y, z, q and 100-uwxyzz defined by the formula (1), oxygen amount ⁇ , nitrogen The sum of the amount ⁇ and the carbon amount ⁇ is allowed to exceed 100% by mass.
- the amount of oxygen in the RTB-based sintered magnet is preferably 0.15% by mass or less.
- v is a value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from the R amount, assuming that the oxygen amount (mass%) is ⁇ , the nitrogen amount (mass%) is ⁇ , and the carbon amount (mass%) is ⁇ . It is necessary to increase the amount of R in the raw material alloy stage. In particular, among regions 1 and 2 in FIG. 1 to be described later, region 1 has a relatively higher v than region 2, so that when the amount of oxygen ⁇ is large, the amount of R at the stage of the raw material alloy may become very large. There is. As a result, the abundance ratio of the main phase is lowered and Br may be lowered. In particular, in the region 1 of the present invention shown in FIG. 1, the oxygen amount is preferably 0.15% by mass or less.
- the R—T—Ga phase includes R: 15% by mass to 65% by mass, T: 20% by mass to 80% by mass, Ga: 2% by mass to 20% by mass. Including, for example, R 6 Fe 13 Ga 1 compound.
- the R—Ga phase includes R: 70 mass% or more and 95 mass% or less, Ga: 5 mass% or more and 30 mass% or less, Fe: 20 mass% or less (including 0), for example, R 3 Ga 1 compound may be mentioned.
- the R—Ga—Cu phase is one in which part of Ga in the R—Ga phase is substituted with Cu, and examples thereof include R 3 (Ga, Cu) 1 compounds.
- the RT-Ga phase may contain Cu, Al, Si, or the like, and the R-Ga-Cu phase may contain Al, Fe, or Co.
- Al includes what is inevitably introduced from a crucible or the like when the raw material alloy is melted.
- the obtained RTB-based sintered magnet material is heated to a temperature of 730 ° C. or more and 1020 ° C. or less, and then cooled to a temperature of 300 ° C. or less at a cooling rate of 20 ° C./min or more (more specifically, 20 ° C. Cooling to 300 ° C./min or more).
- this heat treatment is referred to as a high temperature heat treatment step.
- the RT—Ga phase generated during sintering can be eliminated. If the temperature of the high-temperature heat treatment step is less than 730 ° C., the temperature is too low and the RT-Ga phase may not disappear.
- the heating time is preferably 5 minutes or more and 500 minutes or less.
- the cooling rate after heating to 730 ° C. or more and 1020 ° C. or less to 300 ° C. or less (more specifically, from 20 ° C./min to 300 ° C.) is less than 20 ° C./min, an excessive RT-Ga phase May be generated.
- the cooling rate is 20 ° C./min or more before the temperature reaches 300 ° C., an excessive RT-Ga phase may be generated.
- the cooling rate may be about 40 ° C./min, and may change to a cooling rate such as 35 ° C./min or 30 ° C./min as the temperature approaches 300 ° C.
- an average cooling rate from the heating temperature to 300 ° C. (that is, a temperature between the heating temperature and 300 ° C.)
- the difference may be evaluated by a value obtained by lowering the temperature from the heating temperature and dividing by the time required to reach 300 ° C.
- a sufficient amount of R—Ga—Cu phase can be obtained by suppressing the formation of the RTB—Ga phase as described above. It has gained.
- the temperature of the low-temperature heat treatment step is preferably 480 ° C. or higher and 550 ° C. or lower.
- the heating time is preferably 5 minutes or more and 500 minutes or less.
- the cooling rate after heating at 440 ° C. or more and 550 ° C. or less is not particularly limited.
- the obtained RTB system sintered magnet may be subjected to machining such as grinding in order to adjust the magnet dimensions.
- the high temperature heat treatment step and the low temperature heat treatment step may be performed before or after machining.
- the surface treatment may be a known surface treatment, and for example, a surface treatment such as Al deposition, electric Ni plating or resin coating can be performed.
- the resulting coarsely pulverized powder was mixed with an airflow pulverizer (jet mill device). Then, dry pulverization was performed in a nitrogen stream to obtain finely pulverized powder (alloy powder) having a particle diameter D50 of 4 ⁇ m. Note that the oxygen concentration in the nitrogen gas during pulverization was adjusted by mixing the atmosphere with nitrogen gas during pulverization. When the atmosphere is not mixed, the oxygen concentration in the nitrogen gas during pulverization is 50 ppm or less.
- the particle diameter D50 is a volume-based median diameter obtained by a laser diffraction method using an airflow dispersion method.
- Table 1 a gas analyzer using the gas melting-infrared absorption method for O (oxygen amount), gas melting-heat conduction method for N (nitrogen amount), and combustion-infrared absorption method for C (carbon amount) is used. Measured.
- the molded powder was molded in a magnetic field to obtain a molded body.
- molding apparatus lateral magnetic field shaping
- molding apparatus in which the magnetic field application direction and the pressurization direction orthogonally cross was used for the shaping
- the obtained molded body was sintered in vacuum at 1020 ° C. for 4 hours to obtain an RTB-based sintered magnet material.
- the density of the RTB-based sintered magnet material was 7.5 Mg / m 3 or more.
- the contents of Nd, Pr, Dy, Tb, B, Co, Al, Cu, Ga, Nb and Zr were analyzed by ICP emission spectroscopy. Table 1 shows the results measured by the above.
- the balance (the balance obtained by subtracting the contents of Nd, Pr, Dy, Tb, B, Co, Al, Cu, Ga, Nb, and Zr obtained by measurement from 100% by mass) was defined as the Fe content. .
- Table 1 shows the gas analysis results (O, N, and C).
- the obtained RTB-based sintered magnet material was subjected to a high temperature heat treatment step.
- the RTB-based sintered magnet material was heated to 900 ° C. and held for 3 hours, and then the RTB-based sintered magnet material was cooled to room temperature.
- the cooling is performed by introducing an argon gas into the furnace so that the average cooling rate from the held temperature (900 ° C.) to 300 ° C. is 25 ° C./min, and the average cooling rate from 300 ° C. to room temperature.
- the cooling rate variation (difference between the maximum value and the minimum value of the cooling rate) at the average cooling rate (25 ° C./min and 3 ° C./min) was within 3 ° C./min for all the samples.
- a low temperature heat treatment step was performed on the RTB-based sintered magnet material after the high temperature heat treatment step.
- the RTB-based sintered magnet material was heated to 500 ° C. and held for 2 hours, and then cooled to room temperature at a cooling rate of 20 ° C./min.
- the heating temperature and cooling rate in the high temperature heat treatment step and the low temperature heat treatment step were measured by attaching a thermocouple to the RTB system sintered magnet material.
- u is a value obtained by summing the amounts (mass%) of Nd, Pr, Dy, and Tb in Table 1
- v is the oxygen content (mass%) in Table 1 and the nitrogen content (mass%). Is the value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from u, where ⁇ is ⁇ and the carbon content (% by mass) is ⁇ .
- the B amount (% by mass) in Table 1 was directly transferred.
- the area in Table 2 indicates where the ratio of v and w is in FIG. 1. In the case of 1 area in FIG. 1, 1 and 2 area in FIG. In the case of 2. Furthermore, when it exists in the area
- FIG. 4 is an explanatory diagram in which the values of v and w of the example sample and the comparative example sample (that is, the sample described in Table 2) according to “ ⁇ Example 1>” are plotted in FIG. It can be easily understood from FIG. 4 that the example sample is in the range of the region 1 or 2 and the comparative example sample is out of the region 1 and 2.
- v and w are contained in the following ratio.
- the range of v and w when contained in the proportion corresponds to the region 1 and 2 or 2 in FIG.
- Example samples (example samples other than sample Nos. 48, 49, 53, 54, and 57) of 0.1 all have high magnetic properties such that B r ⁇ 1.340T and H cJ ⁇ 1360 kA / m. have.
- Sample No. 08 is the range of Ga of the present invention when Ga is 0.20 mass% or more and less than 0.40 mass% ( ⁇ (62.5w + v ⁇ 81.625) /15+0.5 ⁇ x (Ga) ⁇ ⁇ (62 .5w + v ⁇ 81.625) /15+0.8), it is impossible to generate the minimum RT-Ga phase necessary for obtaining high magnetic properties, and the H cJ is greatly reduced. It is thought that there is.
- H cJ can be increased.
- B r decreases approximately 0.024T when containing 1 mass% of Dy and Tb.
- HcJ increases by about 160 kA / m when 1% by mass of Dy is contained, and increases by about 240 kA / m when 1% by mass of Tb is contained. Therefore, the present invention has magnetic properties of B r ⁇ 1.340T and H cJ ⁇ 1360 kA / m when the raw material alloy does not contain Dy and Tb as described above.
- B r (T) ⁇ 1.340 ⁇ 0.024 Dy (mass%) ⁇ 0.024 Tb (mass%) and H cJ (kA / m) ⁇ 1360 + 160 Dy (mass%) + 240 Tb (mass%) ) Magnetic properties.
- Sample No. 54 and the content of Ga is Sample No. Sample No. 5 which is a comparative example having the same composition except that it is 0.1 mass% lower than 54. As is clear from 55, even if v and w are within the scope of the present invention, H cJ is greatly reduced when Ga is outside the scope of the present invention. Sample No.
- Ga 55 is a range of Ga of the present invention when Ga is 0.20% by mass or more and less than 0.40% by mass ( ⁇ (62.5w + v ⁇ 81.625) /15+0.5 ⁇ x (Ga) ⁇ ⁇ (62 .5w + v ⁇ 81.625) /15+0.8), it is impossible to generate the minimum RT-Ga phase necessary for obtaining high magnetic properties, and the H cJ is greatly reduced. It is thought that there is.
- the 1 2 (1 region in FIG. 1) region than towards the (second region in FIG. 1) is higher B r (material alloy regions in the present invention Dy
- B r material alloy regions in the present invention
- Dy In the case where Tb is not contained, B r ⁇ 1.354T, and in the case where Dy and Tb are contained, B r ⁇ 1.354T ⁇ 0.024 [Dy] ⁇ 0.024 [Tb]) can be obtained.
- [Dy] [Tb] indicates the content (% by mass) of Dy and Tb, respectively.
- sample No. A raw material alloy was obtained by blending so as to have the same composition as that of No. 34, melting the raw materials, and casting in the same manner as in Experimental Example 1.
- the obtained raw material alloy was subjected to hydrogen treatment and dry pulverization in the same manner as in Experimental Example 1 to obtain finely pulverized powder. Further, molding and sintering were performed in the same manner as in Experimental Example 1 to obtain an RTB-based sintered magnet material.
- the density of the RTB-based sintered magnet material was 7.5 Mg / m 3 or more.
- the components of the obtained RTB-based sintered magnet material and the gas analysis results are shown in Sample No. of Experimental Example 1. 34.
- the obtained RTB-based sintered magnet material is subjected to a high-temperature heat treatment process under the conditions shown in Table 3. Further, the RTB-based sintered magnet material after the high-temperature heat treatment process is subjected to Table 3. A low temperature heat treatment step was performed under the conditions shown.
- the temperature (° C.) of the high-temperature heat treatment step and the low-temperature heat treatment step is the heating temperature of the RTB-based sintered magnet material
- the holding time (Hr) is the holding time of the heating temperature.
- the cooling rate (° C./min) indicates an average cooling rate from the temperature at which the RTB-based sintered magnet material is held to 300 ° C. after the holding time has elapsed.
- the cooling rate of the high temperature heat treatment process and the low temperature heat treatment process from 300 ° C. to room temperature is 3 ° C./min for all samples.
- the cooling rate variation (difference between the maximum value and the minimum value of the cooling rate) at the average cooling rate (from the held temperature to 300 ° C. and from 300 ° C. to room temperature) is within 3 ° C./min for all samples. there were.
- the heating temperature and cooling rate in the high temperature heat treatment step and the low temperature heat treatment step were measured by attaching a thermocouple to the RTB-based sintered magnet material. Furthermore, sample No. “-” In 96 and 97 indicates that the high-temperature heat treatment step was not performed.
- Sample No. Nos. 98 and 99 were not cooled at the cooling rate of the RTB-based sintered magnet material after heating to 300 ° C. at 20 ° C./min or higher in the high-temperature heat treatment step. Unlike 73 and 74, it does not have high magnetic properties of B r ⁇ 1.340T and H cJ ⁇ 1395 kA / m.
- the particle diameter D50 is a volume-based median diameter obtained by a laser diffraction method using an airflow dispersion method. Further, O (oxygen amount), N (nitrogen amount), and C (carbon amount) in Table 5 were measured in the same manner as in Example 1.
- U in Table 6 is a value obtained by summing the amounts (mass%) of Nd, Pr, Dy, and Tb in Table 5, and v is ⁇ and nitrogen (mass%) in Table 5. Is the value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from u, where ⁇ is ⁇ and the carbon content (% by mass) is ⁇ .
- the amount of B in Table 5 was directly transferred.
- the region in Table 6 shows where v and w are in FIG. 2, where 3 is in the region 3 in FIG. 2 and 4 is in the region in FIG. It was described as 4. Furthermore, when it exists in the area
- sample No. A raw material alloy was obtained by blending so as to have the same composition as that of No. 105, melting the raw materials, and casting in the same manner as in Experimental Example 1.
- the obtained raw material alloy was subjected to hydrogen treatment and dry pulverization in the same manner as in Experimental Example 1 to obtain finely pulverized powder. Further, molding and sintering were performed in the same manner as in Experimental Example 1 to obtain an RTB-based sintered magnet material.
- the density of the RTB-based sintered magnet material was 7.5 Mg / m 3 or more.
- the components of the obtained RTB-based sintered magnet material and the gas analysis results are shown in Sample No. 105.
- the obtained RTB-based sintered magnet material is subjected to a high-temperature heat treatment process under the conditions shown in Table 7. Further, the RTB-based sintered magnet material after the high-temperature heat treatment process is subjected to Table 7. A low temperature heat treatment step was performed under the conditions shown.
- the temperature (° C.) of the high temperature heat treatment step and the low temperature heat treatment step is the heating temperature of the RTB-based sintered magnet material
- the holding time (Hr) is the holding time of the heating temperature.
- the cooling rate (° C./min) indicates an average cooling rate from the temperature at which the RTB-based sintered magnet material is held to 300 ° C. after the holding time has elapsed.
- the cooling rate of the high temperature heat treatment process and the low temperature heat treatment process from 300 ° C. to room temperature is 3 ° C./min for all samples.
- the cooling rate variation (difference between the maximum value and the minimum value of the cooling rate) at the average cooling rate (from the held temperature to 300 ° C. and from 300 ° C. to room temperature) is within 3 ° C./min for all samples. there were.
- the heating temperature and cooling rate in the high temperature heat treatment step and the low temperature heat treatment step were measured by attaching a thermocouple to the RTB-based sintered magnet material. Furthermore, the sample Nos. “ ⁇ ” In 165 and 166 indicates that the high-temperature heat treatment process was not performed.
- the RTB-based sintered magnet according to the present invention can be suitably used for many applications such as motors for hybrid vehicles and electric vehicles.
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Abstract
Description
uRwBxGayCuzAlqM(100-u-w-x-y-z-q)T(1)
(Rは軽希土類元素RLと重希土類元素RHからなり、RLはNdおよび/またはPr、RHはDy、Tb、GdおよびHoのうち少なくとも一種であり、Tは遷移金属元素でありFeを必ず含み、MはNbおよび/またはZrであり、u、w、x、y、z、q及び100-u-w-x-y-z-qは質量%を示す。)
前記RHはR-T-B系焼結磁石の5質量%以下であり、下記式(2)~(5)を満足し、
0.20≦x≦0.70 (2)
0.07≦y≦0.2 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)
R-T-B系焼結磁石の酸素量(質量%)をα、窒素量(質量%)をβ、炭素量(質量%)をγとしたとき、v=u-(6α+10β+8γ)であって、
0.40≦x≦0.70のとき、v、wが、下記式(6)および(7)を満足し、
50w-18.5≦v≦50w-14 (6)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
0.20≦x<0.40のとき、v、wが、下記式(8)および(9)を満足し、xが、下記式(10)を満足するR-T-B系焼結磁石素材を準備する工程と、
50w-18.5≦v≦50w-15.5 (8)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10)
前記R-T-B系焼結磁石素材を730℃以上1020℃以下の温度に加熱後、20℃/分以上で300℃まで冷却する高温熱処理工程と、
前記高温熱処理工程後のR-T-B系焼結磁石素材を440℃以上550℃以下の温度に加熱する低温熱処理工程と、
を含むR-T-B系焼結磁石の製造方法である。
0.40≦x≦0.70のとき、v、wが、下記式(11)および(7)を満足し、
50w-18.5≦v≦50w-16.25 (11)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
0.20≦x<0.40のとき、v、wが、下記式(12)および(9)を満足し、xが下記式(10)を満足することを特徴とする態様1に記載のR-T-B系焼結磁石の製造方法である。
50w-18.5≦v≦50w-17.0 (12)
-12.5w+39.125≦v≦-62.5w+86.125であり (9)
-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10)
そこで、さらに検討の結果、焼結後のR-T-B系焼結磁石素材を730℃以上1020℃以下の温度に加熱後、20℃/分以上で300℃以下まで(より詳細には、20℃/分以上で300℃まで)冷却する高温熱処理工程と、高温熱処理工程後のR-T-B系焼結磁石素材を440℃以上550℃以下の温度に加熱する低温熱処理工程とを行うことによって、より高いBrとより高いHcJが得られることがわかった。これは、高温熱処理工程によって焼結後に生成した二粒子粒界のR-T-Ga相を消失させ、消失させたR-T-Ga相を再び生成させないような速度で冷却する。高温熱処理工程では、熱処理対象物が焼結後のR-T-B系焼結磁石素材であるため、酸化防止のために金属製の容器を用いる必要がなく、冷却速度を制御することが可能である。そして、R-T-Ga相を消失させた高温熱処理工程後のR-T-B系焼結磁石素材に低温熱処理工程を行うことによって、二粒子粒界においてR-T-Ga相の生成を極力抑えつつ、R-Ga相およびR-Ga-Cu相を生成させることができると考えられる。
R-T-B系焼結磁石素材を準備する工程は、まず、R-T-B系焼結磁石素材が以下に詳述する組成となるようにそれぞれの元素の金属または合金を準備し、これらからストリップキャスティング法等を用いてフレーク状の原料合金を作製する。次に、前記フレーク状の原料合金から合金粉末を作製し、前記合金粉末を成形、焼結することによりR-T-B系焼結磁石素材を準備する。合金粉末の作製、成形、焼結は、一例として以下のように行う。得られたフレーク状の原料合金を水素粉砕し、例えば1.0mm以下の粗粉砕粉を得る。次に、粗粉砕粉をジェットミル等により微粉砕することで、例えば粒径D50(気流分散法によるレーザー回折法による測定で得られる体積基準メジアン径)が3~7μmの微粉砕粉(合金粉末)を得る。合金粉末は、1種類の合金粉末(単合金粉末)を用いてもよいし、2種類以上の合金粉末を混合することにより合金粉末(混合合金粉末)を得る、いわゆる2合金法を用いてもよく、公知の方法などを用いて本発明の組成となるように合金粉末を作製すればよい。ジェットミル粉砕前の粗粉砕粉、ジェットミル粉砕中およびジェットミル粉砕後の合金粉末に助剤として既知の潤滑剤を使用してもよい。次に得られた合金粉末を用いて磁界中成形を行い、成形体を得る。磁界中成形は、金型のキャビティー内に乾燥した合金粉末を挿入し成形する乾式成形法、金型のキャビティー内に該合金粉末を分散させたスラリーを注入し、スラリーの分散媒を排出しながら成形する湿式成形法を含む既知の任意の磁界中成形方法を用いてよい。そして、成形体を焼結することによりR-T-B系焼結磁石素材を得る。成形体の焼結は既知の方法などを用いることができる。なお、焼結時の雰囲気による酸化を防止するために、焼結は真空雰囲気中または雰囲気ガス中で行うことが好ましい。雰囲気ガスは、ヘリウム、アルゴンなどの不活性ガスを用いることが好ましい。
式:uRwBxGayCuzAlqM(100-u-w-x-y-z-q)T (1)(Rは軽希土類元素RLと重希土類元素RHからなり、RLはNdおよび/またはPr、RHはDy、Tb、GdおよびHoのうち少なくとも一種であり、Tは遷移金属元素でありFeを必ず含み、MはNbおよび/またはZrであり、不可避的不純物を含み、u、w、x、y、z、q及び100-u-w-x-y-z-qは質量%を示す。)によって表わされ、
前記RHはR-T-B系焼結磁石の5質量%以下であり、
0.20≦x≦0.70 (2)
0.07≦y≦0.2 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)であり、
R-T-B系焼結磁石の酸素量(質量%)をα、窒素量(質量%)をβ、炭素量(質量%)をγとしたとき、v=u-(6α+10β+8γ)であって、
0.40≦x≦0.70のとき、v、wが、
50w-18.5≦v≦50w-14 (6)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
を満足し、
0.20≦x<0.40のとき、v、wが、
50w-18.5≦v≦50w-15.5 (8)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
であり、かつ、
xが、-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8(10)
を満足する。
あるいは、
式 :uRwBxGayCuzAlqM(100-u-w-x-y-z-q)T (1)
(Rは軽希土類元素RLと重希土類元素RHからなり、RLはNdおよび/またはPr、RHはDy、Tb、GdおよびHoのうち少なくとも一種であり、Tは遷移金属元素でありFeを必ず含み、MはNbおよび/またはZrであり、不可避的不純物を含み、u、w、x、y、z、q及び100-u-w-x-y-z-qは質量%を示す。)によって表わされ、
前記RHはR-T-B系焼結磁石の5質量%以下であり、
0.20≦x≦0.70 (2)
0.07≦y≦0.2 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)であり、
R-T-B系焼結磁石の酸素量(質量%)をα、窒素量(質量%)をβ、炭素量(質量%)をγとしたとき、v=u-(6α+10β+8γ)であって、
0.40≦x≦0.70のとき、v、wが、
50w-18.5≦v≦50w-16.25 (11)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
を満足し、
0.20≦x<0.40のとき、v、wが、
50w-18.5≦v≦50w-17.0 (12)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
であり、かつ、
xが、-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10)
を満足する。
本発明のR-T-B系焼結磁石素材は不可避的不純物を含んでもよい。例えば、ジジム合金(Nd-Pr)、電解鉄、フェロボロンなどに通常含有される不可避的不純物を含有していても本発明の効果を奏することができる。不可避的不純物として例えば、La、Ce、Cr、Mn、Siなどを微量に含むことがある。
50w-18.5≦v≦50w-14 (6)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
図1に上記式(6)および(7)を満足するvとwの本発明の範囲を示す。図1中のvはR量(u)から酸素量(質量%)をα、窒素量(質量%)をβ、炭素量(質量%)をγとして6α+10β+8γを差し引いた値であり、wはB量の値である。式(6)、すなわち50w-18.5≦v≦50w-14は図1の点Aと点Bを含む直線(点Aと点Bを結ぶ直線)と点Cと点Dを含む直線(点Cと点Dを結ぶ直線)に挟まれた範囲であり、式(7)、すなわち-12.5w+38.75≦v≦-62.5w+86.125は点Dと点F、点B、点Gを含む直線と点Cと点E、点A、点Gを含む直線に挟まれた範囲である。そしてこの両方を満たす領域1と2(点A、点B、点Dおよび点Cで囲まれる領域)が本発明の1つの態様に係る範囲である。vとwを領域1と2の範囲内にすることにより、高いBrと高いHcJを得ることができる。領域1と2の範囲からはずれた領域10(図中、点Dと点F、点B、点Gを含む直線から下の領域)は、wに対してvが少なすぎるためR-T-Ga相の生成量が少なくなり、R2T17相を無くすことができなかったり、R-Ga相およびR-Ga-Cu相の生成量が少なくなると考えられる。これにより、高いHcJが得られない。逆に、領域1と2の範囲から外れた領域20(図中、点Cと点E、点A、点Gを含む直線から上の領域)は、wに対してvが多すぎるため、相対的にFe量が不足する。Fe量が不足するとRおよびBが余ることになり、その結果R-T-Ga相が生成されずにR1Fe4B4相が生成され易くなると考えられる。これによりR-Ga相およびR-Ga-Cu相の生成量も少なくなり、高いHcJが得られない。さらに、領域1と2の範囲からはずれた領域30(点Cと点Dを含む直線から上の領域)は、vが多すぎ且つwが少なすぎるため、R-T-Ga相やR-Ga相およびR-Ga-Cu相は生成されるが、主相の存在比率が低くなり、高いBrが得られない。さらに領域1と2の範囲からはずれた領域40(点C、点Dおよび点Gで囲まれる領域から領域1と2を除いた領域)は、Rが少なく且つBが多すぎるため、主相の存在比率は高いが、R-T-Ga相がほとんど生成されず、R-Ga相およびR-Ga-Cu相の生成量も少なくなるため高いHcJが得られない。
-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10)
xをvとwに応じた上記式(10)の範囲にすることにより、高い磁気特性を得るために最低限必要なR-T-Ga相を生成させることができる。xが上記範囲未満であると、R-T-Ga相の生成量が少なすぎるためHcJが低下する恐れがある。逆に、xが上記範囲を超えると不要なGaが存在することになり、主相の存在比率が低下してBrが低下する恐れがある。
50w-18.5≦v≦50w-15.5 (8)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
図2に式(8)および(9)を満足するvとwの本発明の範囲を示す。式(8)、すなわち50w-18.5≦v≦50w-15.5は図2の点Aと点Lを含む直線と点Jと点Kを含む直線に挟まれた範囲であり、式(9)、すなわち-12.5w+39.125≦v≦-62.5w+86.125は点K、点Iおよび点Lを含む直線と、点J、点Hおよび点Aを含む直線に挟まれた範囲である。そしてこの両方を満たす領域3と4(点A、点L、点Kおよび点Jで囲まれる領域)が本発明の1つの態様に係る範囲である。参考までに、図3に図1(Ga量が0.40質量%以上0.70質量%以下の場合)と図2(Ga量が0.20質量%以上0.40質量%未満の場合)の位置関係(図1に示す範囲と図2に示す範囲の相対的な関係)を示す。x(Ga量)が0.20質量%以上0.40質量%未満であっても、上記範囲(点A、点L、点Kおよび点Jで囲まれる領域3と4)であれば、v、wに応じた適切なxを設定することで高いBrと高いHcJを得ることができる。
50w-18.5≦v≦50w-16.25 (11)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
図1に上記式(11)および(7)を満足するvとwの本発明の範囲を示す。式(11)、すなわち50w-18.5≦v≦50w-16.25は点Aと点Bを含む直線と点Eと点Fを含む直線に挟まれた範囲であり、式(7)、すなわち-12.5w+38.75≦v≦-62.5w+86.125は点Dと点F、点B、点Gを含む直線と点Cと点E、点A、点Gを含む直線に挟まれた範囲である。そしてこの両方を満たす領域2(点A、点B、点Fおよび点Eで囲まれる領域)が本発明の1つの態様に係る範囲である。上記範囲とすることにより、R-T-Ga相の生成量を確保しつつ、vを低く、wを高くすることができるため、主相の存在比率が低くならず、より高いBrを得ることができる。
50w-18.5≦v≦50w-17.0 (12)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
図2に上記式(12)および(9)を満足する範囲を示す。式(12)、すなわち50w-18.5≦v≦50w-17.0は点Aと点Lを含む直線と点Hと点Iを含む直線に挟まれた範囲であり、式(9)、すなわち-12.5w+39.125≦v≦-62.5w+86.125は点Kと点I、点Lを含む直線と点Jと点H、点Aを含む直線に挟まれた範囲である。そしてこの両方を満たす領域4(点A、点L、点Iおよび点Hで囲まれる領域)が本発明の1つの態様に係る範囲である。態様4の(式8)、(式5)に相当する範囲である。参考までに、図3に図1(Gaが0.40質量%以上0.70質量%以下)と図2(Gaが0.20質量%以上0.40質量%未満)の範囲の相対的な位置関係を示す。上記範囲(点A、点L、点Iおよび点Hで囲まれる領域4)にして、かつ、上述したようにxを-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8の範囲とすることにより、R-T-Ga相の生成量を確保しつつ、vを低く、wを高くすることができるため、主相の存在比率が低くならず、より高いBrを得ることができる。
従って、式(1)は、ICP発光分析法により測定可能な元素の合計量が100質量%となるように規定している。一方、酸素量、窒素量および炭素量はICP発光分光分析法では測定不可能である。
このため、本発明に係る態様においては、式(1)で規定するu、w、x、y、z、q及び100-u-w-x-y-z-qと、酸素量α、窒素量βおよび炭素量γとを合計すると100質量%を超えることが許容される。
得られたR-T-B系焼結磁石素材に対して、730℃以上1020℃以下の温度に加熱後、20℃/分以上の冷却速度で300℃以下まで(より詳細には、20℃/分以上で300℃まで)冷却を行う。本発明においては、この熱処理を高温熱処理工程という。高温熱処理工程を行うことにより、焼結時に生成されたR-T-Ga相を消失させることができる。高温熱処理工程の温度が730℃未満であると、温度が低すぎるため、R-T-Ga相が消失しない恐れがあり、1020℃を超えると、粒成長が起こりHcJが低下する恐れがある。加熱時間は、5分以上500分以下が好ましい。730℃以上1020℃以下に加熱後300℃以下まで(より詳細には、20℃/分以上で300℃まで)の冷却速度が20℃/分未満であると、過剰なR-T-Ga相が生成されてしまう恐れがある。同様に300℃に達する前に20℃/分以上の冷却速度未満であると過剰なR-T-Ga相が生成されてしまう恐れがある。また、730℃以上1020℃以下に加熱後300℃以下まで(より詳細には、20℃/分以上で300℃まで)の冷却速度は20℃/分以上であればよく、冷却速度が変動しても構わない。例えば、冷却開始直後は、40℃/分程度の冷却速度で、300℃に近づくにしたがって35℃/分や30℃/分などの冷却速度に変化してもよい。
また、上述のように本発明に係るR-T-B系焼結磁石では、上述のようにR-T-Ga相の形成を抑制することで、十分な量のR-Ga-Cu相を得ている。高いHcJを得るためには、R-T-Ga相を生成することは必要であるものの、その生成を極力抑えて、R-Ga-Cu相を生成させることが重要と考えられる。従って、本発明に係るR-T-B系焼結磁石では、十分なR-Ga-Cu相が得られる程度にR-T-Ga相の生成を抑制すればよく、ある程度の量のR-T-Ga相が存在していてもよい。
高温熱処理工程後のR-T-B系焼結磁石素材に対し、440℃以上550℃以下の温度に加熱する。本発明においては、この熱処理を低温熱処理工程という。これにより、R-T-Ga相が生成される。低温熱処理工程の温度が、440℃未満の場合はR-T-Ga相が生成されない恐れがあり、550℃を超える場合はR-T-Ga相の生成量が過剰となる恐れがあるため、二粒子粒界においてR-Ga相およびR-Ga-Cu相の生成量が不充分となる恐れがある。低温熱処理工程の温度は、好ましくは480℃以上550℃以下である。加熱時間は、5分以上500分以下が好ましい。また、440℃以上550℃以下に加熱後の冷却速度は特に問わない。
Ndメタル、Prメタル、Dyメタル、Tbメタル、フェロボロン合金、電解Co、Alメタル、Cuメタル、Gaメタル、フェロニオブ合金、フェロジルコニウム合金および電解鉄を用いて(メタルはいずれも純度99%以上)、所定の組成となるように配合し、それらの原料を溶解してストリップキャスト法により鋳造し、厚み0.2~0.4mmのフレーク状の原料合金を得た。得られたフレーク状の原料合金を水素加圧雰囲気で水素脆化させた後、550℃まで真空中で加熱、冷却する脱水素処理を施し、粗粉砕粉を得た。次に、得られた粗粉砕粉に、潤滑剤としてステアリン酸亜鉛を粗粉砕粉100質量%に対して0.04質量%添加、混合した後、気流式粉砕機(ジェットミル装置)を用いて、窒素気流中で乾式粉砕し、粒径D50が4μmの微粉砕粉(合金粉末)を得た。なお、粉砕時に窒素ガスに大気を混合することにより粉砕時の窒素ガス中の酸素濃度を調節した。大気を混合しない場合の粉砕時の窒素ガス中の酸素濃度は50ppm以下であり、大気を混合することで窒素ガス中の酸素濃度を最大5000ppmまで増加させ、様々な酸素量の微粉砕粉を作製した。なお、粒径D50は、気流分散法によるレーザー回折法で得られた体積基準メジアン径である。また、表1におけるO(酸素量)はガス融解-赤外線吸収法、N(窒素量)はガス融解-熱伝導法、C(炭素量)は燃焼-赤外線吸収法、によるガス分析装置を使用して測定した。
図4は、図1に「<実施例1>」に係る実施例試料と比較例試料(すなわち、表2に記載の試料)それぞれのv、wの値をプロットした説明図である。図4から実施例試料が領域1または2の範囲内にあり、比較例試料が領域1および2の範囲外にあることが容易に理解できる。
50w-18.5≦v≦50w-14 (6)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
好ましくは、
50w-18.5≦v≦50w-16.25 (11)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
当該割合で含有させた場合の前記vとwの範囲が図1中の1と2または2の領域に相当する。
そのため、本発明は、上述したように原料合金にDy、Tbを含有しない場合はBr≧1.340T、かつ、HcJ≧1360kA/mの磁気特性を有しているので、Dy、Tbの含有量に応じてBr(T)≧1.340-0.024Dy(質量%)-0.024Tb(質量%)、かつ、HcJ(kA/m)≧1360+160Dy(質量%)+240Tb(質量%)の磁気特性を有することになる。
Ndメタル、Prメタル、フェロボロン合金、電解Co、Alメタル、Cuメタル、Gaメタルおよび電解鉄を用いて(メタルはいずれも純度99%以上)、実験例1の試料No.34と同じ組成となるように配合し、それらの原料を溶解し実験例1と同じ方法で鋳造して原料合金を得た。得られた原料合金を実験例1と同じ方法で水素処理、乾式粉砕を行い、微粉砕粉を得た。さらに、実験例1と同じ方法で、成形、焼結し、R-T-B系焼結磁石素材を得た。R-T-B系焼結磁石素材の密度は7.5Mg/m3以上であった。また、得られたR-T-B系焼結磁石素材の成分、ガス分析結果は、実験例1の試料No.34と同等であった。
高温熱処理工程において、加熱後のR-T-B系焼結磁石素材の冷却速度を300℃まで26℃/分で行い、300℃から室温まで3℃/分で冷却することから、400℃まで26℃/分で行い、400℃から室温まで3℃/分で冷却することに変更した以外は、実験例2の試料No.73と同じ方法でR-T-B系焼結磁石を作製した。得られたR-T-B系焼結磁石に機械加工を施し、縦7mm、横7mm、厚み7mmの試料を作製し、B-Hトレーサによって各試料のBr及びHcJを測定した。測定結果を表4の試料No.98に示す。同様に、高温熱処理工程において、加熱後のR-T-B系焼結磁石素材の冷却速度を300℃まで26℃/分で行い、300℃から3℃/分で冷却することから、400℃まで26℃/分で行い、400℃から3℃/分で冷却することに変更した以外は、実験例2の試料No.74と同じ方法でR-T-B系焼結磁石を作製した。得られたR-T-B系焼結磁石に機械加工を施し、縦7mm、横7mm、厚み7mmの試料を作製し、B-Hトレーサによって各試料のBr及びHcJを測定した。測定結果を表4の試料No.99に示す。
Ndメタル、Prメタル、Dyメタル、Tbメタル、フェロボロン合金、電解Co、Alメタル、Cuメタル、Gaメタル、フェロニオブ合金、フェロジルコニウム合金および電解鉄を用いて(メタルはいずれも純度99%以上)、所定の組成となるように配合し、実験例1と同様の方法により粒径D50が4μmの微粉砕粉(合金粉末)を得た。なお、粉砕時に窒素ガスに大気を混合することにより粉砕時の窒素ガス中の酸素濃度を調節した。大気を混合しない場合の粉砕時の窒素ガス中の酸素濃度は50ppm以下であり、大気を混合することで窒素ガス中の酸素濃度を最大1500ppmまで増加させ、様々な酸素量の微粉砕粉を作製した。なお、粒径D50は、気流分散法によるレーザー回折法で得られた体積基準メジアン径である。また、表5におけるO(酸素量)、N(窒素量)、C(炭素量)は実施例1と同様の方法で測定した。
Ndメタル、Prメタル、フェロボロン合金、電解Co、Alメタル、Cuメタル、Gaメタルおよび電解鉄を用いて(メタルはいずれも純度99%以上)、実験例4の試料No.105と同じ組成となるように配合し、それらの原料を溶解し実験例1と同じ方法で鋳造して原料合金を得た。得られた原料合金を実験例1と同じ方法で水素処理、乾式粉砕を行い微粉砕粉を得た。さらに、実験例1と同じ方法で、成形、焼結し、R-T-B系焼結磁石素材を得た。R-T-B系焼結磁石素材の密度は7.5Mg/m3以上であった。また、得られたR-T-B系焼結磁石素材の成分、ガス分析結果は、実験例4の試料No.105と同等であった。
Claims (6)
- 下記式(1)によって表わされ、
uRwBxGayCuzAlqM(100-u-w-x-y-z-q)T(1)
(Rは軽希土類元素RLと重希土類元素RHからなり、RLはNdおよび/またはPr、RHはDy、Tb、GdおよびHoのうち少なくとも一種であり、Tは遷移金属元素でありFeを必ず含み、MはNbおよび/またはZrであり、u、w、x、y、z、q及び100-u-w-x-y-z-qは質量%を示す。)
前記RHはR-T-B系焼結磁石の5質量%以下であり、下記式(2)~(5)を満足し、
0.20≦x≦0.70 (2)
0.07≦y≦0.2 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)
R-T-B系焼結磁石の酸素量(質量%)をα、窒素量(質量%)をβ、炭素量(質量%)をγとしたとき、v=u-(6α+10β+8γ)であって、
0.40≦x≦0.70のとき、v、wが、下記式(6)および(7)を満足し、
50w-18.5≦v≦50w-14 (6)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
0.20≦x<0.40のとき、v、wが、下記式(8)および(9)を満足し、xが、下記式(10)を満足するR-T-B系焼結磁石素材を準備する工程と、
50w-18.5≦v≦50w-15.5 (8)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10)
前記R-T-B系焼結磁石素材を730℃以上1020℃以下の温度に加熱後、20℃/分以上で300℃まで冷却する高温熱処理工程と、
前記高温熱処理工程後のR-T-B系焼結磁石素材を440℃以上550℃以下の温度に加熱する低温熱処理工程と、
を含むR-T-B系焼結磁石の製造方法。 - 前記低温熱処理工程は、480℃以上550℃以下の温度に加熱する請求項1に記載のR-T-B系焼結磁石の製造方法。
- 得られたR-T-B系焼結磁石の酸素量が0.15質量%以下である、請求項1または2に記載のR-T-B系焼結磁石の製造方法。
- 0.40≦x≦0.70のとき、v、wが、下記式(11)および(7)を満足し、
50w-18.5≦v≦50w-16.25 (11)
-12.5w+38.75≦v≦-62.5w+86.125 (7)
0.20≦x<0.40のとき、v、wが、下記式(12)および(9)を満足し、xが下記式(10)を満足することを特徴とする請求項1に記載のR-T-B系焼結磁石の製造方法。
50w-18.5≦v≦50w-17.0 (12)
-12.5w+39.125≦v≦-62.5w+86.125 (9)
-(62.5w+v-81.625)/15+0.5≦x≦-(62.5w+v-81.625)/15+0.8 (10) - 前記低温熱処理工程は、480℃以上550℃以下の温度に加熱する請求項4に記載のR-T-B系焼結磁石の製造方法。
- 得られたR-T-B系焼結磁石の酸素量が0.15質量%以下である、請求項4または5に記載のR-T-B系焼結磁石の製造方法。
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