WO2015022945A1 - R-t-b系焼結磁石 - Google Patents
R-t-b系焼結磁石 Download PDFInfo
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- WO2015022945A1 WO2015022945A1 PCT/JP2014/071228 JP2014071228W WO2015022945A1 WO 2015022945 A1 WO2015022945 A1 WO 2015022945A1 JP 2014071228 W JP2014071228 W JP 2014071228W WO 2015022945 A1 WO2015022945 A1 WO 2015022945A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
- C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
Definitions
- the present disclosure relates to an RTB based sintered magnet.
- RTB-based sintered magnet having R 2 T 14 B type compound as a main phase (R is composed of light rare earth element RL and heavy rare earth element RH, RL is Nd and / or Pr, RH is Dy and / or Tb and T are at least one of transition metal elements and must contain Fe), and are known as the most powerful magnets among permanent magnets, and are used for hybrid vehicles, electric vehicles, and home appliances. Used in 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.
- H cJ coercive force
- Dy has problems such as unstable supply and price fluctuations due to the fact that it originally has a small amount of resources and its production area is limited. Therefore, (as small as possible amount) without using much as possible heavy rare earth element such as Dy, while suppressing a decrease in B r, it is required to obtain a high H cJ.
- 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. It is described that an RTB-based rare earth sintered magnet having a high C can be obtained.
- 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. At this time, it is shown that Ga contributes to the generation of a nonmagnetic compound, Co contributes to the improvement of the temperature coefficient of the residual magnetic flux density, and Cu contributes to the suppression of the magnetic property degradation due to the Laves phase accompanying the addition of Co.
- 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, aims while suppressing the content of Dy, provides R-T-B based sintered magnet having a high B r and high H cJ And
- Aspect 1 of the present invention is represented by the following formula (1).
- R consists of a light rare earth element RL and a heavy rare earth element RH, RL is Nd and / or Pr, RH is Dy and / or Tb, the balance T is Fe, and 10 mass% or less of Fe is Co.
- RH is 5% by mass or less of the RTB-based sintered magnet, and satisfies the following formulas (2) to (6): 0.4 ⁇ x ⁇ 1.0 (2) 0.07 ⁇ y ⁇ 1.0 (3) 0.05 ⁇ z ⁇ 0.5 (4) 0 ⁇ q ⁇ 0.1 (5) 0.100 ⁇ y / (x + y) ⁇ 0.340 (6)
- 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 satisfy the following formulas (7) to (9): an RTB-based sintered magnet.
- Aspect 2 of the present invention is an RTB-based sintered magnet according to aspect 1, wherein the following formulas (10) and (11) are satisfied. 0.4 ⁇ x ⁇ 0.7 (10) 0.1 ⁇ y ⁇ 0.7 (11)
- Aspect 3 of the present invention is an RTB-based sintered magnet according to aspect 1 or 2, wherein the following formula (12) is satisfied. 0.4 ⁇ x ⁇ 0.6 (12)
- Aspect 4 of the present invention is an RTB-based sintered magnet characterized by satisfying the following formula (13) in any of the aspects 1 to 3. v ⁇ 28.5 (13)
- Aspect 5 of the present invention is an RTB-based sintered magnet characterized by satisfying the following formula (14) in any of the aspects 1 to 4. 0.90 ⁇ w ⁇ 0.93 (14)
- FIG. 2A and 2B are schematic views for explaining a method for measuring the thickness of the first grain boundary.
- a photograph of an image by SE that is emitted when a cross section of an RTB-based sintered magnet is irradiated with an electron beam having a high acceleration voltage is a photograph of an image by SE that is emitted when a cross section of an RTB-based sintered magnet is irradiated with an electron beam having a high acceleration voltage.
- R, B, Ga, Cu, Al, and optionally M optimize content, by further containing Ga and Cu in specific ratios, R-T-B based sintered magnet having a high B r and high H cJ was found that the resulting.
- the first grain boundary existing between the two main phases (hereinafter sometimes referred to as “two-grain grain boundary”) has R Is 70% by mass or more, and it is found that there is a phase in which Ga and Cu are concentrated more than the composition of the entire magnet (hereinafter sometimes referred to as R-Ga-Cu phase), and further analysis As a result, it was found that R was 65% by mass or less and a two-grain grain boundary in which a phase containing T and Ga (hereinafter, sometimes referred to as RT-Ga phase) does not exist was included.
- 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.
- Ga contained in the magnet composition, a RT-Ga phase is generated instead of the R 2 T 17 phase, and a decrease in H cJ can be suppressed.
- the decrease in H cJ due to the generation of the R—T—Ga phase is due to the absence of the R 2 T 17 phase that causes a rapid decrease in H cJ and the generated R—T—Ga phase being magnetic. It was assumed that this is because it does not have or is very weak in magnetism.
- the cases R-T-Ga phase also has a magnetic there, the grain boundary, when the R-T-Ga phase there are many particularly in the secondary particle grain boundaries responsible for H cJ, is preventing the H cJ increased I understood.
- the present inventors have found that HcJ is improved by generating an RT-Ga phase and generating an R-Ga-Cu phase at the grain boundary.
- the amount of R 2 T 17 phase generated can be reduced by setting the amounts of R and B within appropriate ranges.
- 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. Accordingly, it has been difficult to suppress the production amounts of the R 2 T 17 phase and the RT-Ga phase.
- the R amount corrected by the amounts of oxygen, nitrogen, and carbon specifically In the R amount (u), when the oxygen amount (mass%) in the RTB-based sintered magnet is ⁇ , the nitrogen amount (mass%) is ⁇ , and the carbon amount (mass%) is ⁇ , 6 ⁇ + 10 ⁇ + 8 ⁇ is obtained. It was found that by using the subtracted value (v), it is possible to control the amount of R 2 T 17 phase or RT-Ga phase produced within an appropriate range.
- the value (v) obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from the R amount (u), the B amount, the Ga amount, the Cu amount, and the Al amount are contained at a specific ratio, and further, Ga and Cu are made to have a specific ratio.
- high H cJ can be obtained and, at this time, it is possible to an amount that does not lower the amount of R and B amounts greatly existence ratio of the main phase was found to obtain a high B r.
- the entire RTB-based sintered magnet there are many R—Ga—Cu phases at the two-grain boundaries, and there are many two-grain boundaries where there is almost no RT-Ga phase. It is thought that it is an organization.
- 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 RT-Ga phase. .
- 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, thereby, a high B r and high H cJ is considered not obtained.
- the “thickness of the first grain boundary (two grain grain boundary)” in the present invention is the thickness of the first grain boundary existing between the two main phases, and more specifically, among the grain boundaries. It means the maximum value of the thickness when the region with the largest thickness is measured. “The thickness of the first grain boundary (two-grain grain boundary)” is evaluated by the following procedure, for example. 1) By scanning electron microscope (SEM) observation, five or more visual fields including a two-particle grain boundary having a length of 3 ⁇ m or more in the observation cross section are randomly selected.
- SEM scanning electron microscope
- FIG. 2A is a diagram schematically showing an example of the first grain boundary
- FIG. 2B is a diagram schematically showing an example of the first grain boundary
- the first grain boundary 20 may include a region 22 having a large thickness and a region 24 having a small thickness. In such a case, the maximum thickness of the region 22 having a large thickness is obtained. The value is the thickness of the first grain boundary 20.
- the second grain boundary 30 existing between the first grain boundary 20 and the three or more main phases 40 may be connected.
- the “thickness of the first grain boundary” refers to the vicinity of a boundary (for example, the first grain boundary 20 and the first grain boundary 20) that changes from the first grain boundary 20 to the second grain boundary 30 in the cross section of the magnet whose thickness is to be measured. It is assumed that the thickness of a region separated by about 0.5 ⁇ m from the boundaries 35 ⁇ / b> A and 35 ⁇ / b> B with the second grain boundary 30 is not measured. This is because the boundary is considered to be affected by the thickness of the second grain boundary 30.
- the measurement range of the thickness of the first grain boundary 20 has a length of 2 ⁇ m or more in a range excluding a region separated by about 0.5 ⁇ m from the boundaries 35A and 35B.
- the range indicated by the braces denoted by reference numeral 20 in FIG. 2B indicates the range in which the first grain boundary 20 extends, and the measurement range of the thickness of the first grain boundary 20 is not necessarily limited. It should be noted that it does not indicate (that is, a range excluding a region separated by about 0.5 ⁇ m from the boundaries 35A and 35B).
- the first grain boundary thickness by a 5nm or 30nm or less, it is possible to obtain a higher B r and H cJ.
- the thickness of the first grain boundary can be 5 nm or more and 30 nm or less.
- a more preferable range of the thickness of the first grain boundary is 10 nm or more and 30 nm or less.
- the thickness of the first grain boundary can be simplified by acquiring a secondary electron image of a sample cross section using, for example, a high acceleration voltage electron beam mounted on a STEM apparatus, as shown in an example described later. Can be evaluated.
- composition of RTB-based sintered magnet In an embodiment according to the present invention, the formula: uRwBxGayCuzAlqM (100-uwxyzzq) T (1) (R consists of a light rare earth element RL and a heavy rare earth element RH, RL is Nd and / or Pr, RH is Dy and / or Tb, the balance T is Fe, and 10 mass% or less of Fe is Co.
- M is Nb and / or Zr, and contains unavoidable impurities, u, w, x, y, z, q and 100-uwxyzzq indicate mass% )
- the RH is 5% by mass or less of the RTB-based sintered magnet, 0.4 ⁇ x ⁇ 1.0 (2) 0.07 ⁇ y ⁇ 1.0 (3) 0.05 ⁇ z ⁇ 0.5 (4) 0 ⁇ q ⁇ 0.1 (5) 0.100 ⁇ y / (x + y) ⁇ 0.340 (6)
- 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, w v ⁇ 32.0 (7) 0.84 ⁇ w ⁇ 0.93 (8) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w +
- the RTB-based sintered magnet 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 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
- RL is Nd and / or Pr
- RH is Dy and / or Tb.
- RH is 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 elements, it can reduce the amount of RH even be asked a higher H cJ, typically 2.5 It can be made into the mass% or less.
- T is Fe, and 10% by mass or less, typically 2.5% by mass or less of Fe can be substituted with Co.
- B is boron.
- 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 and / Or Tb and RH is 5% by mass or less of the RTB-based sintered magnet. ”Completely excludes the case where R contains a rare earth element other than Nd, Pr, Dy and Tb. This means that rare earth elements other than Nd, Pr, Dy and Tb may be contained as long as they are in an impurity level.
- R, B, Ga combined with a range according to one aspect of the respectively present invention Cu, and, by the ratio, according to one embodiment of the present invention the Ga and Cu, obtain a high B r and high H cJ be able to. If it deviates from the above range, the main phase ratio is significantly reduced, or the generation of the RTB-Ga phase is excessively suppressed. It becomes difficult to generate a Ga—Cu phase, or conversely, there are fewer two-grain boundaries where no RT—Ga phase exists (a two-grain boundary where there are many RT-Ga phases becomes dominant) not obtain a high B r and high H cJ.
- Ga contributes to the formation of a thick two-grain grain boundary by dissolving the vicinity of the main phase surface by being present in the liquid phase introduced into the two-grain grain boundary. It is thought that. Furthermore, Ga is also necessary for the formation of the RT-Ga phase, which is considered to be involved in the formation of the R-Ga-Cu phase.
- Ga or Cu is not more than the specified value of the present invention, that is, when the Ga content (x) is less than 0.4 mass% or the Cu content (y) is less than 0.07 mass%, R—Ga at the grain boundary is The formation of the -Cu phase becomes insufficient, the effects of the respective elements cannot be sufficiently exhibited, and high HcJ cannot be obtained. Therefore, the Ga amount (x) is set to 0.4% by mass or more, or the Cu amount (y) is set to 0.07% by mass or more. A preferable amount of Cu (y) is 0.1% by mass or more.
- the Ga amount (x) is 0.7% by mass or less
- the Cu amount (y) is 0.7% by mass or less
- the Ga amount (x) is 0.6% by mass or less
- the Cu amount (y ) Is 0.4 mass% or less.
- y / (x + y) i.e., ⁇ Cu> / ⁇ Ga + Cu> (where ⁇ Cu> is the amount of Cu expressed in mass%, and ⁇ Ga + Cu> is the total amount of Ga and Cu expressed in mass%).
- ⁇ Cu> is the amount of Cu expressed in mass%
- ⁇ Ga + Cu> is the total amount of Ga and Cu expressed in mass%.
- the amount of Ga introduced into the two-grain grain boundary is reduced, and Ga existing in the second grain boundary existing between three or more main phases (hereinafter sometimes referred to as “multi-point grain boundary”).
- the amount of liquid phase containing increases. Accordingly, since the dissolution of the second near the grain boundary of the main phase becomes conspicuous by the liquid phase containing Ga, not only H cJ is not sufficiently improved, leading to reduction in B r.
- ⁇ Cu> / ⁇ Ga + Cu> exceeds 0.34, the Ga abundance ratio in the liquid phase is too small, and the main phase is not sufficiently dissolved by the liquid phase introduced into the two-particle grain boundary. Therefore , the two-grain grain boundary does not become thick and high HcJ cannot be obtained.
- the mass ratio of ⁇ Cu> / ⁇ Ga + Cu> is 0.1 or more and 0.3 or less.
- Al 0.05 mass% or more and 0.5 mass% or less
- HcJ HcJ
- Al is usually contained in an amount of 0.05% by mass or more as an inevitable impurity in the production process, but it may be contained in an amount of 0.5% by mass or less in total of the amount contained by the inevitable impurity and the amount intentionally added. Good.
- Nb and / or Zr may be contained in a total amount of 0.1% by mass or less.
- 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 total mass of the system magnet is 100% by mass) the oxygen content is the gas melting-infrared absorption method, the nitrogen content is the gas melting-heat conduction method, and the carbon content is the combustion-infrared absorption method , Can be measured using a gas analyzer.
- 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. This makes it possible to adjust the amount of R 2 T 17 phase or RT-Ga phase generated.
- 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 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, and M shown in Formula (1)
- the respective contents (mass%) u, w, x, y, z and q may be measured by using a high frequency inductively coupled plasma optical emission spectrometry (ICP emission spectroscopic analysis, ICP-OES).
- the content (mass%) of the balance T shown in the formula (1) is 100-uwxyzzq, and u, w, x, y, obtained by ICP emission spectroscopy You may obtain
- the formula (1) defines that the total amount of elements that can be measured by ICP emission spectroscopy 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.
- v and w are related as follows. v ⁇ 32.0 (7) 0.84 ⁇ w ⁇ 0.93 (8) ⁇ 12.5w + 38.75 ⁇ v ⁇ ⁇ 62.5w + 86.125 (9) When v exceeds 32.0% by mass, the abundance ratio of the main phase is lowered, and high Br cannot be obtained. In order to obtain a higher B r is, v ⁇ 28.5 is preferred.
- FIG. 1 shows the scope of the present invention for v and w that satisfy the above equations (7) to (9).
- v is a value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ from the R amount (u), where the oxygen amount (% by mass) is ⁇ , the nitrogen amount (% by mass) is ⁇ , and the carbon amount (% by mass) is ⁇ .
- B value B value.
- 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—Cu phase means R: 70% by mass to 95% by mass, Ga: 5% by mass to 30% by mass, Cu: 1% by mass to 30% by mass, and Fe: 20% by mass or less. (Including 0), for example, R 3 (Ga, Cu) 1 compound.
- the RT-Ga phase may contain Cu, Al, or the like.
- the R—Ga—Cu phase may contain Al or Co.
- Al includes what is inevitably introduced from a crucible or the like when the raw material alloy is melted.
- the two-grain grain boundary has a dhcp structure (double hexagonal close-packed structure) containing Fe: 20% by mass or less (including 0) and a trace amount of Ga and Cu.
- An Nd phase may also exist, but this phase is also non-magnetic or extremely weak (small) and can exist as a thick two-grain grain boundary phase. Therefore, the coercivity can be reduced by weakening the magnetic coupling between the main phases. It is thought that it contributes to improvement.
- the manufacturing method of the RTB-based sintered magnet includes a process of obtaining alloy powder, a forming process, a sintering process, and a heat treatment process. Hereinafter, each step will be described.
- Step of obtaining alloy powder A metal or alloy of each element is prepared so as to have a predetermined composition, and a flaky alloy is manufactured using the strip casting method or the like.
- the obtained flaky alloy is hydrogen crushed so that the size of the coarsely pulverized powder is 1.0 mm or less, for example.
- 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 D 50 (volume-based median diameter obtained by a laser diffraction method by an air flow dispersion method) of 3-7 ⁇ m )
- 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.
- Forming step Using the obtained alloy powder, forming in a magnetic field is performed to obtain a formed body.
- a dry alloy method in which a dry alloy powder is inserted into a mold cavity and molded while applying a magnetic field, a slurry in which the alloy powder is dispersed is injected into the mold cavity, Any known forming method in a magnetic field may be used, including a wet forming method of forming while discharging the slurry dispersion medium.
- a sintered magnet is obtained by sintering a molded object.
- a known method can be used for sintering the molded body.
- the atmosphere gas is preferably an inert gas such as helium or argon.
- the obtained sintered magnet is subjected to heat treatment for the purpose of improving magnetic properties.
- the Nd 6 Fe 13 Ga phase is represented by the heat treatment performed after the sintering. It is considered that the RT-Ga phase is mainly formed in the multipoint grain boundary and the R-Ga-Cu phase is formed in the two-grain grain boundary.
- the heat treatment temperature is typically 440 ° C. or higher and 540 ° C. or lower. This temperature is lower than the Nd—Fe—Ga ternary eutectic temperature (580 ° C.).
- the RT—Ga phase is mainly converted into a multipoint grain boundary phase. And a liquid phase containing both Ga and Cu and relatively rich in Cu is generated, and the liquid phase is introduced into the two-grain grain boundary, whereby the R—Ga—Cu phase is formed. It is believed that high H cJ is obtained when formed. Furthermore, it has been found that in an RTB-based sintered magnet that has been heat-treated at 440 ° C. or higher and 540 ° C. or lower, the R—Ga—Cu phase may become amorphous.
- the obtained sintered magnet may be subjected to machining such as grinding in order to adjust the magnet dimensions.
- the heat treatment 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). was dry milled in a nitrogen stream, the particle size D 50 was obtained finely pulverized powder of 4 ⁇ m (the alloy powder).
- the oxygen concentration in the nitrogen gas at the time of pulverization was set to 50 ppm or less so that the finally obtained sintered magnet had an oxygen content of about 0.1 mass%.
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- 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 crossed was used for the shaping
- the obtained molded body was sintered in vacuum at 1020 ° C. for 4 hours and then rapidly cooled to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- the components of the obtained sintered magnet and the results of gas analysis are shown in Table 1.
- the contents of Nd, Pr, B, Ga, Cu, Al, Co, Nb, and Zr as components in Table 1 were measured using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). .
- the balance (the balance obtained by subtracting the contents of Nd, Pr, B, Ga, Cu, Al, Co, Nb, and Zr obtained by measurement from 100% by mass) was taken as the content of Fe.
- O oxygen
- N nitrogen amount
- C carbon amount
- the total amount of Nd and Pr is the R amount (u). The same applies to all the tables below.
- the obtained sintered magnet was heated, held at 800 ° C. for 2 hours and then cooled to room temperature, and then held at 500 ° C. for 2 hours and then cooled to room temperature.
- vertical 7 mm, transverse 7 mm, to prepare a sample having a thickness of 7 mm it was magnetized with a pulse magnetic field of 3.2 MA / m, by B-H tracer in each sample B r And H cJ were measured. The measurement results are shown in Table 2.
- V in Table 2 is a value obtained by subtracting 6 ⁇ + 10 ⁇ + 8 ⁇ obtained from ⁇ , ⁇ , and ⁇ in Table 1 from u. For u and w, the amounts of R and B in Table 1 are directly transferred. The same applies to Table 4, Table 6, Table 8, and Table 10 below.
- 1-2, 1-3, 1-12, 1-17, 1-20 to 1-22, 1-28) have higher B r (1.376 T or more), and v is 28.
- Samples of 5 or less (No. 1-2, 1-3, 1-20 to 22, 1-28) have higher B r (1.393 T or more).
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- the finely pulverized powder was molded and sintered in the same manner as in Experimental Example 1 to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- Components of the obtained sintered magnet and gas analysis (O (oxygen amount), N (nitrogen amount), C (carbon amount)) were performed in the same manner as in Experimental Example 1. The results are shown in Table 3.
- the resultant sintered magnet was heat-treated in the same manner as in Experimental Example 1 were measured B r and H cJ in the same manner as in Experimental Example 1. Table 4 shows the measurement results.
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- the finely pulverized powder was molded and sintered in the same manner as in Experimental Example 1 to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- Components of the obtained sintered magnet and gas analysis (O (oxygen amount), N (nitrogen amount), C (carbon amount)) were performed in the same manner as in Experimental Example 1. The results are shown in Table 5.
- the resultant sintered magnet was heat-treated in the same manner as in Experimental Example 1 were measured B r and H cJ in the same manner as in Experimental Example 1. Table 6 shows the measurement results.
- the resulting coarsely pulverized powder was mixed with an airflow pulverizer (jet mill device). was dry milled in a nitrogen stream, the particle size D 50 was obtained finely pulverized powder of 4 ⁇ m (the alloy powder).
- the oxygen amount of the finally obtained sintered magnet was set to about 0.4% by mass.
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- the finely pulverized powder was molded and sintered in the same manner as in Experimental Example 1 to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- Components of the obtained sintered magnet and gas analysis (O (oxygen amount), N (nitrogen amount), C (carbon amount)) were performed in the same manner as in Experimental Example 1. The results are shown in Table 7.
- the resultant sintered magnet was heat-treated in the same manner as in Experimental Example 1 were measured B r and H cJ in the same manner as in Experimental Example 1. Table 8 shows the measurement results.
- Example 5 Nd metal, Pr metal, Dy metal, Tb metal, ferroboron alloy, electrolytic Co, Al metal, Cu metal, Ga metal, and electrolytic iron (all metals have a purity of 99% or more) so as to have a predetermined composition
- a coarsely pulverized powder was prepared in the same manner as in Experimental Example 4. After adding and mixing 0.04% by mass of zinc stearate as a lubricant with respect to 100% by mass of the coarsely pulverized powder, the resulting coarsely pulverized powder was mixed with nitrogen using an airflow pulverizer (jet mill device). dry milled in an air stream, the particle size D 50 was obtained finely pulverized powder of 4 ⁇ m (the alloy powder).
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- the finely pulverized powder was molded and sintered in the same manner as in Experimental Example 1 to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- Components of the obtained sintered magnet and gas analysis (O (oxygen amount), N (nitrogen amount), C (carbon amount)) were performed in the same manner as in Experimental Example 1. The results are shown in Table 9.
- the resultant sintered magnet was heat-treated in the same manner as in Experimental Example 1 were measured B r and H cJ in the same manner as in Experimental Example 1. Table 10 shows the measurement results.
- Example Sample No. of the present invention produced in Experimental Example 1 1-20 and Comparative Sample No. 1-1 was cut by machining and the cross section was polished, followed by observation with a scanning electron microscope (SEM), and the first grain boundary existing between two main phases having a length in the observation cross section of 3 ⁇ m or more (two Grain boundary) is randomly assigned to sample no. 1-20, No. 1 1-1, 5 fields of view were selected, and a slice was processed using a focused ion beam (FIB) to prepare a sample for a transmission electron microscope (TEM).
- SEM scanning electron microscope
- the obtained sample was observed with a TEM, and the thickness of the grain boundary was measured. After confirming that the length of the two-grain boundary in the sample is 3 ⁇ m or more, exclude the region about 0.5 ⁇ m away from the vicinity of the boundary with the second grain boundary existing between three or more main phases.
- the thickness of the grain boundary in the region (the length was 2 ⁇ m or more) was evaluated, and the maximum value was defined as the thickness of the grain boundary phase.
- the measurement was performed with a high TEM magnification in order to accurately measure the thickness. The same analysis was performed on all five sampled first grain boundary phases, and the average value was obtained.
- the two-grain grain boundary is evaluating the area
- Comparative Sample No. 1-1 was 1 nm to 3 nm.
- Example Sample No. 1-20 R is 65% by mass or less, and there is no RT-Ga phase containing T and Ga. At least a part of the grain boundary is Nd: 52% by mass, Pr: 26% by mass %, Ga: 5% by mass, Cu: 4% by mass, Fe: 7% by mass, Co: 3% by mass, which is an R—Ga—Cu phase characteristic of the magnet of the present invention. It was confirmed. Further, as a result of electron beam diffraction in this region, it was found to be amorphous. On the other hand, Comparative Sample No. In 1-1, no R—Ga—Cu phase was confirmed.
- Example 4 in which Nd metal, Pr metal, ferroboron alloy, electrolytic Co, Al metal, Cu metal, Ga metal, and electrolytic iron were used (all metals had a purity of 99% or more) and were mixed to have a predetermined composition.
- a coarsely pulverized powder was prepared in the same manner as described above. After adding and mixing 0.04% by mass of zinc stearate as a lubricant with respect to 100% by mass of the coarsely pulverized powder, the resulting coarsely pulverized powder was mixed with nitrogen using an airflow pulverizer (jet mill device). dry milled in an air stream, the particle size D 50 was obtained finely pulverized powder of 4.5 ⁇ m (the alloy powder).
- the particle diameter D 50 is a value obtained by laser diffraction method using air flow dispersion method (volume-based median diameter).
- the finely pulverized powder was molded and sintered in the same manner as in Experimental Example 1 to obtain a sintered magnet.
- the density of the sintered magnet was 7.5 Mg / m 3 or more.
- Components of the obtained sintered magnet and gas analysis (O (oxygen amount), N (nitrogen amount), C (carbon amount)) were performed in the same manner as in Experimental Example 1. The results are shown in Table 11.
- the obtained sintered magnet was heated, held at 800 ° C. for 2 hours, cooled to room temperature, and then held at 480 ° C. for 1 hour and then cooled to room temperature.
- vertical 7 mm, transverse 7 mm, to prepare a sample having a thickness of 7 mm it was magnetized with a pulse magnetic field of 3.2mA / m, B-H tracer with a sample B r and HcJ was measured. Table 12 shows the measurement results.
- Example 7 Example No. 6-1
- SEM scanning electron microscope
- the microsampling process by the focused ion beam (FIB) was performed so that it might be obtained.
- STEM scanning transmission electron microscope
- an electron beam with an acceleration voltage of 200 kV (high acceleration voltage) is irradiated onto the sample surface using a secondary electron detector attached to the microscope.
- Images of secondary electrons (SE) emitted (contrast is obtained by the difference in phase) were taken.
- An example of an SE image obtained with an electron beam having a high acceleration voltage is shown in FIG.
- a thick two-grain boundary can be clearly confirmed at a magnification of about 10,000 times.
- the grain boundary phase of 10 nm or more was dominant.
- the sintered magnet sample was broken in an ultra-high vacuum to evaluate spin polarization (magnetization) due to 3d electrons (mainly derived from Fe) of the two-grain grain boundary phase exposed on the surface, Thereafter, the two-grain boundary phase was removed by sputtering, and the main phase was similarly evaluated.
- spin polarization magnetization
- 3d electrons mainly derived from Fe
- the sintered magnet (No. 6-1) of Experimental Example 7 has a lower magnetization and a thick two-grain grain boundary phase than a general Nd—Fe—B based sintered magnet.
- the fact that the magnetic coupling between the main phases is greatly weakened is considered to have led to a higher coercive force.
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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および/またはTbであり、残部であるTはFeでありFeの10質量%以下をCoで置換でき、MはNbおよび/またはZrであり、u、w、x、y、z、qおよび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)~(6)を満足し、
0.4≦x≦1.0 (2)
0.07≦y≦1.0 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)
0.100≦y/(x+y)≦0.340 (6)
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、v、wが、下記式(7)~(9)を満足することを特徴とする、R-T-B系焼結磁石である。
v≦32.0 (7)
0.84≦w≦0.93 (8)
-12.5w+38.75≦v≦-62.5w+86.125 (9)
0.4≦x≦0.7 (10)
0.1≦y≦0.7 (11)
0.4≦x≦0.6 (12)
v≦28.5 (13)
0.90≦w≦0.93 (14)
1)走査電子顕微鏡(SEM)観察で、観察断面における長さが3μm以上ある二粒子粒界を含む視野をランダムに5視野以上選択する。
2)それぞれの視野に対して、収束イオンビーム(FIB)を用いたマイクロサンプリング法により、前記二粒子粒界相を含むように試料を加工した後、さらに、厚さ方向が80nm以下となるまで薄片加工する。
3)得られた薄片試料を透過電子顕微鏡(TEM)観察し、個々の二粒子粒界における最大値を求める。当然ながら、選択した前記二粒子粒界のうち厚みが最も大きい領域を決定した後、当該領域の厚みの最大値を測定する時は、精度良く測定するためにTEMの倍率を高めてもよい。
4)1)~3)の手順で観察したすべての二粒子粒界の最大値の平均値を求める。
図2(a)は、第一の粒界の例を模式的に示す図であり、図2(b)は、図2(a)の点線で囲んだ部分を拡大した図である。
図2(b)に示すように、第一の粒界20は厚みが大きい領域22と小さい領域24が混在している場合があるが、このような場合、厚みが大きい領域22の厚みの最大値を第一の粒界20の厚みとする。また、図2(b)に示すように、第一の粒界20と三つ以上の主相40間に存在する第二の粒界30はつながっている場合がある。この場合、「第一の粒界の厚み」とは、厚みを測定する磁石の断面において第一の粒界20から第二の粒界30にかわる境目近傍(例えば、第一の粒界20と第二の粒界30との境目35A、35Bから、0.5μm程度離れた領域)の厚みは測定しないこととする。前記境目は、第二の粒界30の厚みの影響をうけている可能性があると考えられるためである。第一の粒界20の厚みの測定範囲は、境目35A、35Bから0.5μm程度離れた領域を除いた範囲で2μm以上の長さがあることとする。ここで、図2(b)において符号20を付した中括弧が示す範囲は、第一の粒界20が延在する範囲を示すものであり、必ずしも第一の粒界20の厚みの測定範囲(すなわち、境目35A、35Bから0.5μm程度離れた領域を除いた範囲)を示すものではないことに留意されたい。
本発明に係る態様では
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および/またはTbであり、残部であるTはFeでありFeの10質量%以下をCoで置換できる、MはNbおよび/またはZrである、および不可避的不純物を含み、u、w、x、y、z、qおよび100-u-w-x-y-z-qは質量%を示す)
によって表され、
前記RHはR-T-B系焼結磁石の5質量%以下であり、
0.4≦x≦1.0 (2)
0.07≦y≦1.0 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)
0.100≦y/(x+y)≦0.340 (6)
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、v、wが、
v≦32.0 (7)
0.84≦w≦0.93 (8)
-12.5w+38.75≦v≦-62.5w+86.125 (9)
を満足することを特徴とする、R-T-B系焼結磁石である。
なお、特定の希土類元素を得ようとすると精錬等の過程で、不純物として意図しない他の種類の希土類元素が不純物として含まれてしまうことが広く知られている。従って、上述の「本発明の1つの態様に係るR-T-B系焼結磁石における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および/またはTbであり、RHはR-T-B系焼結磁石の5質量%以下である。」は、Rが、Nd、Pr、DyおよびTb以外の希土類元素を含む場合を完全に排除するものではなく、Nd、Pr、DyおよびTb以外の希土類元素についても不純物レベルの量であれば含有してもよいことを意味している。
従って、式(1)は、ICP発光分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。
v≦32.0 (7)
0.84≦w≦0.93 (8)
-12.5w+38.75≦v≦-62.5w+86.125 (9)
vが32.0質量%を超えると、主相の存在比率が低くなり高いBrが得られない。より高いBrを得るためには、v≦28.5が好ましい。wが0.84質量%未満であると、主相の体積比率が低下して高いBrが得られず、wが0.93質量%を超えると、R-T-Ga相の生成量が少なすぎるため、R-Ga-Cu相の生成量も少なくなり、高いHcJを得ることができない。より高いBrを得るためには、0.90≦w≦0.93が好ましい。そして、vとwは-12.5w+38.75≦v≦-62.5w+86.125の関係を満足する。
図1に上記式(7)~(9)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。本発明の1つの態様に係る範囲である式(9)、すなわち、-12.5w+38.75≦v≦-62.5w+86.125は直線1と直線2に挟まれた範囲である。vとwを本発明の範囲にするにすることにより、高いBrと高いHcJを得ることができる。本発明の範囲からはずれた領域10(直線2から図中下の領域)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-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、本発明の範囲から外れた領域20(直線1から図中上の領域)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相が十分生成されずにR1Fe4B4が生成され易くなると考えられる。これによりR-Ga-Cu相の生成量も少なくなり、高いHcJが得られない。
R-T-B系焼結磁石の製造方法の一例を説明する。R-T-B系焼結磁石の製造方法は、合金粉末を得る工程、成形工程、焼結工程、熱処理工程を有する。以下、各工程について説明する。
所定の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、これらをストリップキャスティング法等を用いてフレーク状の合金を製造する。得られたフレーク状の合金を水素粉砕し、粗粉砕粉のサイズを例えば1.0mm以下とする。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で得られた体積基準メジアン径)が3~7μmの微粉砕粉(合金粉末)を得る。なお、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。
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、磁界を印加しながら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。
成形体を焼結することにより焼結磁石を得る。成形体の焼結は既知の方法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。
得られた焼結磁石に対し、磁気特性を向上させることを目的とした熱処理を行う。態様1に示すR量、B量、Ga量、Cu量およびGaとCuの特定の比にした本発明の組成では、焼結後に施される熱処理で、Nd6Fe13Ga相に代表されるR-T-Ga相が主に多重点粒界中に形成されるとともに、R-Ga-Cu相が二粒子粒界に形成されると考えられる。熱処理温度は典型的には440℃以上540℃以下である。この温度は、Nd-Fe-Ga三元共晶温度(580℃)よりも低い温度であり、このような温度で熱処理を行うことにより、R-T-Ga相が主に多重点粒界相中に形成されるとともに、Ga、Cuの両方を含み、かつ比較的Cuに富んだ液相が生成され、前記液相が二粒子粒界に導入されることにより、R-Ga-Cu相が形成されて高いHcJが得られると考えられる。さらに、440℃以上540℃以下の熱処理を行ったR-T-B系焼結磁石では、R-Ga-Cu相が非晶質になる場合があることがわかった。このような非晶質の粒界相の存在は主相最外部の磁気異方性低下の原因となる結晶性の悪化を抑制し、結果、保磁力の向上に寄与すると考えられる。
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、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に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、本検討では、粉砕時の窒素ガス中の酸素濃度は50ppm以下とすることにより、最終的に得られる焼結磁石の酸素量が0.1質量%前後となるようにした。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値(体積基準メジアン径)である。
さらに、本発明の条件を満足している組成の焼結磁石(実施例)のうち、w(B量)が、0.90以上(0.90≦w≦0.93)のサンプル(No.1-2、1-3、1-12、1-17、1-20~1-22、1-28)は、より高いBr(1.376T以上)が得られており、vが28.5以下のサンプル(No.1-2、1-3、1-20~22、1-28)は、さらに高いBr(1.393T以上)が得られている。
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)、所定の組成となるように配合し、実験例1と同様の方法で粗粉砕粉を作製した。得られた粗粉粉砕に対し、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。このとき粉砕時の窒素ガス中の酸素濃度を制御することにより、最終的に得られる焼結磁石の酸素量が0.25質量%前後となるようにした。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値(体積基準メジアン径)である。
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)、所定の組成となるように配合し、実験例1と同様の方法で粗粉砕粉を作製した。得られた粗粉粉砕に対し、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。このとき粉砕時の窒素ガス中の酸素濃度を制御することにより、最終的に得られる焼結磁石の酸素量が0.4質量%前後となるようにした。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値(体積基準メジアン径)である。
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、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に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。このとき粉砕時の窒素ガス中の酸素濃度を制御することにより、最終的に得られる焼結磁石の酸素量が0.4質量%前後となるようにした。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値(体積基準メジアン径)である。
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、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4と同様の方法で粗粉砕粉を作成した。得られた粗粉粉砕に対し、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。このとき粉砕時の窒素ガス中の酸素濃度を制御することにより、最終的に得られる焼結磁石の酸素量が0.4質量%前後となるようにした。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値(体積基準メジアン径)である。
実験例1で作製した本発明の実施例サンプルNo.1-20および比較例サンプルNo.1-1を機械加工により切断し、断面を研磨した後、走査電子顕微鏡(SEM)観察を行い、観察断面における長さが3μm以上ある、二つの主相間に存在する第一の粒界(二粒子粒界)をランダムにサンプルNo.1-20、No.1-1それぞれ、5視野選択して、収束イオンビーム(FIB)を用いて薄片加工し、透過型電子顕微鏡(TEM)用のサンプルを作製した。
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)、所定の組成となるように配合し実験例4と同様の方法で粗粉砕粉を作成した。得られた粗粉粉砕に対し、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4.5μmの微粉砕粉(合金粉末)を得た。このとき粉砕時の窒素ガス中の酸素濃度を制御することにより、最終的に得られる焼結磁石の酸素量が0.08質量%前後となるようにした。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値(体積基準メジアン径)である。
22:厚みが大きい領域
24:厚みが小さい領域
30:第二の粒界
35A、35B:境目
40:主相
Claims (5)
- 下記式(1)によって表され、
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および/またはTbであり、残部であるTはFeでありFeの10質量%以下をCoで置換でき、MはNbおよび/またはZrであり、u、w、x、y、z、qおよび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)~(6)を満足し、
0.4≦x≦1.0 (2)
0.07≦y≦1.0 (3)
0.05≦z≦0.5 (4)
0≦q≦0.1 (5)
0.100≦y/(x+y)≦0.340 (6)
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、
v、wが、下記式(7)~(9)を満足することを特徴とする、R-T-B系焼結磁石。
v≦32.0 (7)
0.84≦w≦0.93 (8)
-12.5w+38.75≦v≦-62.5w+86.125 (9) - 下記式(10)および(11)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。
0.4≦x≦0.7 (10)
0.1≦y≦0.7 (11) - 下記式(12)を満足することを特徴とする、請求項1または2に記載のR-T-B系焼結磁石。
0.4≦x≦0.6 (12) - 下記式(13)を満足することを特徴とする、請求項1から3のいずれか1項に記載のR-T-B系焼結磁石。
v≦28.5 (13) - 下記式(14)を満足することを特徴とする、請求項1から4のいずれか1項に記載のR-T-B系焼結磁石。
0.90≦w≦0.93 (14)
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