R-t-b permanent magnet

Abstract

Provided is an R-T-B permanent magnet that contains Al, Cu, Ga, and Zr. The R content is 30.00-33.00 mass%, the Co content is greater than 0.80 mass% but no greater than 3.00 mass%, the B content is 0.70-0.83 mass%, the Al content is greater than 0 mass% but less than 0.20 mass%, the Cu content is greater than 0.10 mass% but less than 1.50 mass%, the Ga content is 0.40-1.00 mass%, and the Zr content is greater than 0.10 mass% but no greater than 1.60 mass%.

Description

RTB series permanent magnet

[0001] The present invention relates to an RTB based permanent magnet.

[0002] Patent Document 1 describes an invention relating to an R—Fe—B sintered magnet that has a specific composition and microstructure and thereby has a high coercive force (HcJ) at high temperatures.

[0003] Patent Document 2 describes an invention relating to an R—(Fe, Co)—B based sintered magnet that has a high HcJ at room temperature and at high temperatures due to its specific composition and microstructure.

[0004] JP 2017-228771 A JP 2018-82040 A

[0005] An object of the present invention is to provide an R-T-B based permanent magnet that has a well-balanced improvement in remanence (Br) at room temperature and HcJ at high temperatures, and also has a high squareness ratio (Hk / HcJ) at room temperature.

[0006] In order to achieve the above object, the R-T-B system permanent magnet of the present invention is an R-T-B system permanent magnet containing Al, Cu, Ga, and Zr, wherein, taking the R-T-B system permanent magnet as 100% by mass, the R content is 30.00% by mass or more and 33.00% by mass or less, the Co content is more than 0.80% by mass and 3.00% by mass or less, the B content is 0.70% by mass or more and 0.83% by mass or less, the Al content is more than 0% by mass and less than 0.20% by mass, the Cu content is more than 0.10% by mass and less than 1.50% by mass, the Ga content is 0.40% by mass or more and 1.00% by mass or less, and the Zr content is more than 0.10% by mass and 1.60% by mass or less.

[0007] The C content may be 0.05 mass % or more and 0.30 mass % or less.

[0008] The content of the heavy rare earth element may be 0% by mass or more and 0.30% by mass or less.

[0009] The residual magnetic flux density of the R-T-B system permanent magnet at room temperature is Br L (mT), the coercive force of the RTB-based permanent magnet at 150°C is HcJ H(kA / m), HcJ H ≧600, Br L + (HcJ H / 3)≧1565, and the squareness ratio at room temperature may be 92.0% or more.

[0010] The present invention will be described below based on embodiments.

[0011] The R-T-B system permanent magnet contains Al, Cu, Ga, and Zr. Taking the R-T-B system permanent magnet as 100% by mass, the R content is 30.00% by mass or more and 33.00% by mass or less, the Co content is 0.80% by mass or more and 3.00% by mass or less, the B content is 0.70% by mass or more and 0.83% by mass or less, the Al content is more than 0% by mass and less than 0.20% by mass, the Cu content is more than 0.10% by mass and less than 1.50% by mass, the Ga content is 0.40% by mass or more and 1.00% by mass or less, and the Zr content is more than 0.10% by mass and 1.60% by mass or less.

[0012] When the RTB-based permanent magnet has the above composition, it is possible to improve Br at room temperature and HcJ at high temperatures in a balanced manner.

[0013] In R-T-B system permanent magnets, R represents a rare earth element, T represents an iron group element, and B represents boron. R-T-B system permanent magnets are permanent magnets that contain one or more rare earth elements, one or more iron group elements, and boron. Iron group elements are a general term for Fe, Co, and Ni. R-T-B system permanent magnets are R2T 14 The main phase grains have a B-type crystal structure.

[0014] Regarding the rare earth elements, the content of R, i.e., the content of the rare earth elements, is 30.00 mass% or more and 33.00 mass% or less. The content of the rare earth elements may be 30.00 mass% or more and 32.00 mass% or less. When the content of the rare earth elements is 30.00 mass% or more and 32.00 mass% or less, the Br at room temperature is more likely to be improved compared to when the content of the rare earth elements exceeds 32.00 mass%. When the content of R is too small, the HcJ at high temperatures is likely to be low. When the content of R is too large, abnormal grain growth is likely to occur, and the Br at room temperature is likely to be low. The R-T-B system permanent magnet may contain, as the rare earth element, essentially only one or more elements selected from Nd, Pr, Dy, and Tb, or may contain essentially only one or more elements selected from Nd and Pr. Note that, "an R-T-B system permanent magnet containing substantially only one or more rare earth elements selected from Nd, Pr, Dy, and Tb" means that the total content of rare earth elements other than Nd, Pr, Dy, and Tb is 0.01 mass% or less. "an R-T-B system permanent magnet containing substantially only one or more rare earth elements selected from Nd and Pr" means that the total content of rare earth elements other than Nd and Pr is 0.01 mass% or less.

[0015] Regarding rare earth elements, in order to reduce raw material costs, the content of heavy rare earth elements may be 0% by mass or more and 0.80% by mass or less, 0% by mass or more and 0.50% by mass or less, or 0% by mass or more and 0.30% by mass or less.

[0016] Among the rare earth elements, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu are considered to be heavy rare earth elements.

[0017] Regarding iron-group elements, R-T-B based permanent magnets essentially contain Co. The Co content is greater than 0.80 mass% and not greater than 3.00 mass%. It may be 0.85 mass% or greater and not greater than 3.00 mass%. If the Co content is too small, the HcJ at high temperatures decreases, and the Hk / HcJ also decreases. If the Co content is too large, the HcJ at high temperatures decreases.

[0018] There is no particular limitation on the content of iron group elements other than Co. The content of Fe will be described later. Ni may not be substantially contained. Specifically, the Ni content may be less than 0.01 mass%.

[0019] The B content is 0.70% by mass or more and 0.83% by mass or less. If the B content is too small, sintering tends to be insufficient. As a result, Br at room temperature and HcJ at high temperatures tend to be low. Furthermore, Hk / HcJ also tends to decrease. If the B content is too large, HcJ at high temperatures tends to be low.

[0020] The Al content is greater than 0 mass% and less than 0.20 mass%. It may be 0.02 mass% or more and 0.15 mass% or less, or 0.02 mass% or more and 0.07 mass% or less. If no Al is contained, HcJ at high temperatures will be low. If the Al content is too high, Br at room temperature will be low.

[0021] The Ga content is 0.40% by mass or more and 1.00% by mass or less. The Ga content may be 0.40% by mass or more and 0.80% by mass or less. When the Ga content is 0.40% by mass or more and 0.80% by mass or less, Br at room temperature is more easily improved compared to when the Ga content exceeds 0.80% by mass. When the Ga content is too small, HcJ at high temperatures is likely to be low. When the Ga content is too large, Br at room temperature is likely to be low.

[0022] The Zr content is greater than 0.10 mass% and less than or equal to 1.60 mass%. It may be 0.15 mass% or more and 1.50 mass% or less, 0.35 mass% or more and 1.30 mass% or less, or 0.35 mass% or more and 0.95 mass% or less. When a high HcJ at high temperatures is important, it may be 0.50 mass% or more and 1.50 mass% or less. If the Zr content is too low, the magnetic particles contained in the R-T-B system permanent magnet tend to grow. As a result, the HcJ at high temperatures tends to decrease. If the Zr content is too high, sintering tends to be insufficient. As a result, both the Br at room temperature and the HcJ at high temperatures tend to decrease.

[0023] The Cu content is greater than 0.10 mass% and less than 1.50 mass%. It may be 0.15 mass% or more and 1.00 mass% or less, or 0.15 mass% or more and 0.30 mass% or less. If the Cu content is too small or too large, both Br at room temperature and HcJ at high temperatures tend to decrease. By setting the Cu content to 0.15 mass% or more and 1.00 mass% or less, it becomes easier to improve Br at room temperature and HcJ at high temperatures in a balanced manner.

[0024] The Cu content may be 0.15% by mass or more and 0.30% by mass or less. When the Cu content is 0.15% by mass or more and 0.30% by mass or less, the HcJ at high temperatures is more easily improved than when the Cu content exceeds 0.30% by mass.

[0025] The RTB system permanent magnet may contain O, N and / or C as required, or may not contain O, N and / or C.

[0026] When O is contained, the O content may be 0% by mass or more and 0.20% by mass or less.

[0027] When N is contained, the N content may be 0 mass % or more and 0.10 mass % or less.

[0028] When C is contained, the C content may be 0.05% by mass or more and 0.30% by mass or less, or 0.13% by mass or more and 0.26% by mass or less. When the C content is within the above range, it becomes easier to further improve the Br at room temperature and the HcJ at high temperatures in a balanced manner, and it also becomes easier to improve Hk / HcJ.

[0029] When we say that an R-T-B system permanent magnet is 100% by mass, we mean that the total content of all elements is 100% by mass. The Fe content in the R-T-B system permanent magnet may be essentially the remainder of the R-T-B system permanent magnet. Specifically, the total content of elements other than the above-mentioned elements, i.e., elements other than rare earth elements, Fe, Co, Ni, B, Al, Ga, Zr, Cu, O, N, and C, may be 0.50% by mass or less.

[0030] <Method for manufacturing an R-T-B system permanent magnet> An example of a method for manufacturing an R-T-B system permanent magnet according to this embodiment will now be described. The method for manufacturing an R-T-B system permanent magnet (RTB system sintered magnet) according to this embodiment comprises the following steps. Note that each of the steps (g) to (i) below may be omitted.

[0031] (a) an alloy preparation step for producing a raw material alloy; (b) a crushing step for crushing the raw material alloy; (c) a compacting step for compacting the obtained alloy powder; (d) a sintering step for sintering the compact to obtain an R-T-B system permanent magnet; (e) an aging treatment step for aging the R-T-B system permanent magnet; (f) a cooling step for cooling the R-T-B system permanent magnet; (g) a processing step for processing the R-T-B system permanent magnet; (h) a grain boundary diffusion step for diffusing a heavy rare earth element into the grain boundaries of the R-T-B system permanent magnet; and (i) a surface treatment step for surface treating the R-T-B system permanent magnet.

[0032] [Alloy Preparation Step] First, a raw alloy is prepared (alloy preparation step). Hereinafter, strip casting will be described as an example of an alloy preparation method, but the alloy preparation method is not limited to strip casting.

[0033] First, raw material metals corresponding to the composition of the raw material alloy are prepared, and the prepared raw material metals are melted in a vacuum or in an inert gas atmosphere such as Ar gas. The melted raw material metals are then cast to produce the raw material alloy. Note that although the one-alloy method is described in this embodiment, a two-alloy method in which two alloys, a first alloy and a second alloy, are mixed to produce the raw material alloy may also be used.

[0034] There are no particular limitations on the type of raw material metal. For example, rare earth metals or rare earth alloys, pure iron, pure cobalt, ferroboron, and alloys or compounds thereof can be used. There are no particular limitations on the casting method for casting the raw material metal. Examples include ingot casting, strip casting, book molding, and centrifugal casting. If the obtained raw material alloy has solidification segregation, it may be subjected to homogenization treatment (solution treatment) as necessary.

[0035] [Pulverization Step] After the raw alloy is prepared, it is pulverized (pulverization step). The pulverization step may be performed in two stages: a coarse pulverization step in which the raw alloy is pulverized to particle sizes of several hundred μm to several mm, and a fine pulverization step in which the raw alloy is pulverized to particle sizes of several μm, or may be performed in a single stage consisting of the fine pulverization step alone.

[0036] (Coarse pulverization step) The raw alloy is coarsely pulverized until the particle size is on the order of several hundred μm to several mm (coarse pulverization step). This produces a coarsely pulverized powder of the raw alloy. Coarse pulverization may be performed, for example, by hydrogen absorption pulverization. Hydrogen absorption pulverization can be performed by causing the raw alloy to absorb hydrogen and then releasing the hydrogen based on the difference in the amount of hydrogen absorbed between different phases, thereby causing self-destructive pulverization. Releasing hydrogen based on the difference in the amount of hydrogen absorbed between different phases is called dehydrogenation. There are no particular restrictions on the dehydrogenation conditions, but dehydrogenation can be performed, for example, at 300 to 650°C, in an argon flow or in a vacuum.

[0037] The method of coarse pulverization is not limited to the hydrogen absorption pulverization described above. For example, coarse pulverization may be performed in an inert gas atmosphere using a coarse pulverizer such as a stamp mill, a jaw crusher, or a Braun mill.

[0038] Furthermore, to obtain an R-T-B system permanent magnet with high magnetic properties, it is preferable to use an atmosphere with a low oxygen concentration during each process, from the coarse pulverization process to the sintering process described below. The oxygen concentration is adjusted by controlling the atmosphere in each manufacturing process. If the oxygen concentration is high during each manufacturing process, the rare earth elements in the alloy powder obtained by pulverizing the raw alloy will oxidize, resulting in the formation of rare earth element oxides. The rare earth element oxides are not reduced during sintering and instead precipitate at grain boundaries in the form of rare earth element oxides. Grain boundaries are the areas between two or more main phase particles. As a result, the Br of the resulting R-T-B system permanent magnet will be reduced. Therefore, for example, it is preferable to perform each process (fine pulverization process, compaction process) in an atmosphere with an oxygen concentration of 100 ppm or less.

[0039] (Fine Pulverization Process) After coarsely pulverizing the raw alloy, the obtained coarsely pulverized powder of the raw alloy is finely pulverized until the average particle size is approximately several μm (fine pulverization process). This produces finely pulverized powder of the raw alloy. The coarsely pulverized powder can be further finely pulverized to produce finely pulverized powder. There are no particular restrictions on the D50 of the particles contained in the finely pulverized powder. For example, the D50 may be 2.0 μm or more and 4.5 μm or less, or 2.5 μm or more and 3.5 μm or less. The smaller the D50, the more likely the HcJ of the R-T-B system permanent magnet according to this embodiment is to be improved. However, abnormal grain growth is more likely to occur during the sintering process, and the upper limit of the sintering temperature range is lowered. The larger the D50, the less likely abnormal grain growth is to occur during the sintering process, and the upper limit of the sintering temperature range is higher. However, the HcJ of the R-T-B system permanent magnet according to this embodiment is more likely to be reduced.

[0040] Fine pulverization is performed by further pulverizing the coarsely pulverized powder using a fine pulverizer such as a jet mill, ball mill, vibration mill, or wet attritor, while appropriately adjusting conditions such as pulverization time. Jet mills are described below. A jet mill is a fine pulverizer that generates a high-speed gas flow by releasing a high-pressure inert gas (e.g., He gas, N2 gas, or Ar gas) from a narrow nozzle, and this high-speed gas flow accelerates the coarsely pulverized powder of the raw alloy, causing collisions between the coarsely pulverized powder of the raw alloy and with the target or the wall of the container, resulting in pulverization.

[0041] A grinding aid may be added when the coarsely pulverized powder of the raw alloy is finely pulverized. There are no particular limitations on the type of grinding aid. For example, an organic lubricant or a solid lubricant may be used. Examples of organic lubricants include oleic acid amide, lauric acid amide, and zinc stearate. Examples of solid lubricants include graphite. By adding a grinding aid, it is possible to obtain a finely pulverized powder that is more likely to become oriented when a magnetic field is applied during the compaction process. Either an organic lubricant or a solid lubricant may be used alone, or both may be used in combination. This is because the degree of orientation may decrease, especially when a solid lubricant is used alone.

[0042] [Forming Step] The finely pulverized powder is formed into the desired shape (forming step). In the forming step, the finely pulverized powder is filled into a mold placed in an electromagnet and pressurized to form a compact. By forming the powder while applying a magnetic field, the crystal axes of the finely pulverized powder can be oriented in a specific direction during forming. Since the resulting compact is oriented in a specific direction, an R-T-B system permanent magnet with stronger anisotropy can be obtained. A forming aid may also be added. There are no particular restrictions on the type of forming aid. The same lubricant as the grinding aid may also be used. The grinding aid may also serve as a forming aid.

[0043] The pressure during pressurization may be, for example, 30 MPa or more and 300 MPa or less. The applied magnetic field may be, for example, 1000 kA / m or more and 1600 kA / m or less. The applied magnetic field is not limited to a static magnetic field, but may also be a pulsed magnetic field. Furthermore, a static magnetic field and a pulsed magnetic field may also be used in combination.

[0044] As a molding method, in addition to the dry molding in which the finely pulverized powder is molded as is as described above, wet molding in which a slurry in which the finely pulverized powder is dispersed in a solvent such as oil is molded can also be applied.

[0045] The shape of the compact obtained by compacting the finely pulverized powder is not particularly limited, and can be, for example, a rectangular parallelepiped, a plate, a column, a ring, or any other shape that corresponds to the desired shape of the R-T-B system permanent magnet.

[0046] [Sintering Process] The compact obtained by molding in a magnetic field and forming into the desired shape is sintered in a vacuum or inert gas atmosphere to obtain an R-T-B system permanent magnet (sintering process). The holding temperature and holding time during sintering need to be adjusted depending on various conditions, such as the composition (mainly the B content), the pulverization method, and differences in particle size and particle size distribution. The holding temperature may be, for example, 1000°C to 1100°C, or 1020°C to 1060°C. There is no particular limit to the holding time, but it may be, for example, 2 hours to 50 hours, or 8 hours to 40 hours. The shorter the holding time, the more efficient the production. There is no particular limit to the atmosphere during holding. For example, an inert gas atmosphere may be used, or a vacuum atmosphere of less than 100 Pa, or a vacuum atmosphere of less than 10 Pa may be used. There is no particular limit to the heating rate up to the holding temperature. Sintering causes liquid-phase sintering of the finely pulverized powder, resulting in the R-T-B system permanent magnet according to this embodiment. There is no particular limitation on the cooling rate after sintering the compact to obtain a sintered body, but the sintered body may be rapidly cooled to improve production efficiency. The sintered body may be rapidly cooled at a rate of 30°C / min or more.

[0047] [Aging Treatment Step] After sintering the compact, the R-T-B system permanent magnet is subjected to an aging treatment (aging treatment step). After sintering, the R-T-B system permanent magnet is subjected to an aging treatment by, for example, holding the resulting R-T-B system permanent magnet at a temperature lower than that during sintering. Below, we will explain a case where the aging treatment is divided into two stages, a first aging treatment and a second aging treatment, but it is also possible to perform only one of the aging treatments, or to perform three or more stages of aging treatment.

[0048] There are no particular limitations on the holding temperature and holding time for each aging treatment. For example, the first aging treatment may be performed at a holding temperature of 800°C to 900°C for 30 minutes to 4 hours. The temperature rise rate to the holding temperature may be 5°C / min to 50°C / min. The atmosphere during the first aging treatment may be an inert gas atmosphere (e.g., He gas, Ar gas) at atmospheric pressure or higher. The second aging treatment may be performed under the same conditions as the first aging treatment, except that the holding temperature may be 450°C to 550°C. The aging treatment can improve the magnetic properties of the R-T-B system permanent magnet. The aging treatment process may also be performed after the processing process described below.

[0049] [Cooling Step] After the R-T-B system permanent magnet has been subjected to aging treatment (first aging treatment or second aging treatment), the R-T-B system permanent magnet is rapidly cooled in an inert gas atmosphere (cooling step). This allows the R-T-B system permanent magnet according to this embodiment to be obtained. The cooling rate is not particularly limited; it may be 30°C / min or more.

[0050] [Processing Step] The obtained R-T-B based permanent magnet may be processed into a desired shape as needed (processing step). Processing methods include, for example, shaping such as cutting and grinding, and chamfering such as barrel polishing.

[0051] [Grain Boundary Diffusion Step] A heavy rare earth element may be further diffused into the grain boundaries of the processed R-T-B system permanent magnet (grain boundary diffusion step). There are no particular limitations on the method of grain boundary diffusion. For example, it may be carried out by attaching a compound containing a heavy rare earth element to the surface of the R-T-B system permanent magnet by coating or vapor deposition, and then performing a heat treatment. It may also be carried out by heat treating the R-T-B system permanent magnet in an atmosphere containing vapor of the heavy rare earth element. Grain boundary diffusion can further improve the HcJ of the R-T-B system permanent magnet.

[0052] [Surface Treatment Step] The R-T-B based permanent magnet obtained by the above steps may be subjected to a surface treatment such as plating, resin coating, oxidation treatment, or chemical conversion treatment (surface treatment step), which can further improve corrosion resistance.

[0053] The R-T-B system permanent magnet obtained in the above manner has good magnetic properties. That is, the Br at room temperature and the HcJ at high temperatures are improved in a well-balanced manner, and an R-T-B system permanent magnet with a high Hk / HcJ is obtained. Specifically, the Br at room temperature (23°C) of the R-T-B system permanent magnet is L (mT), HcJ of R-T-B system permanent magnet at high temperature (150°C) H (kA / m), HcJ H ≧600, Br L + (HcJ H / 3)≧1565 and an RTB based permanent magnet having an Hk / HcJ of 92.0% or more can be obtained.

[0054] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. For example, in the method for producing an R-T-B system permanent magnet, hot compaction and hot working may be performed instead of sintering.

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0056] (Experimental Example 1) (Alloy Preparation Step) In the alloy preparation step, raw material alloys were prepared that would ultimately yield R-T-B based permanent magnets having the compositions shown in Tables 1 to 4. TRE refers to the content of R. The contents of elements other than Fe that are not listed in Tables 1 to 4 were all less than 0.01 mass %. That is, in each of the examples and comparative examples shown in Tables 1 to 4, Fe constitutes the substantial remainder.

[0057] First, raw metals containing predetermined elements were prepared, such as simple elements listed in Tables 1 to 4, alloys containing the elements listed in Tables 1 to 4, and / or compounds containing the elements listed in Tables 1 to 4.

[0058] Next, these raw material metals were weighed and strip-cast to prepare raw material alloys that would ultimately yield magnets with the compositions shown in Tables 1 to 4. The carbon content of the raw material alloys was controlled by changing the proportion of pig iron and .

[0059] (Pulverization Step) In the pulverization step, the raw alloy obtained in the preparation step was pulverized to obtain alloy powder. Pulverization was performed in two stages: coarse pulverization and fine pulverization. Coarse pulverization was performed by hydrogen absorption pulverization. After hydrogen was absorbed into the raw alloy, dehydrogenation was performed in an argon flow or in a vacuum at 300 to 600°C. By the coarse pulverization, alloy powder with a particle size of several hundred μm to several mm was obtained.

[0060] Fine pulverization was carried out using a jet mill after adding oleic acid amide as a grinding aid to 100 parts by mass of the alloy powder obtained by coarse pulverization and mixing. The amount of oleic acid amide added was controlled so as to ultimately obtain magnets having the compositions shown in Tables 1 to 4. Nitrogen gas was used in the jet mill. Fine pulverization was carried out until the D50 of the alloy powder reached approximately 3.0 μm.

[0061] (Compacting step) In the compacting step, the alloy powder obtained in the pulverizing step was compacted in a magnetic field to obtain a compact. The alloy powder was filled into a mold placed in an electromagnet, and then compacted by applying pressure while applying a magnetic field from the electromagnet. The magnitude of the applied magnetic field was 1200 kA / m. The pressure during compacting was 40 MPa.

[0062] (Sintering step) In the sintering step, the obtained molded body was sintered to obtain a sintered body. The holding temperature and holding time during sintering were changed appropriately depending on the B content. The holding temperature and holding time during sintering are shown in Tables 1 to 4. The heating rate when raising the temperature to the holding temperature was 8.0°C / min, and the cooling rate when cooling from the holding temperature to room temperature was 50°C / min. The sintering atmosphere was a vacuum atmosphere or an inert gas atmosphere.

[0063] (Aging Step) In the aging step, the obtained sintered body was subjected to aging treatment to obtain an RTB based permanent magnet. The aging treatment was carried out in two stages: first aging treatment and second aging treatment.

[0064] In the first aging treatment, the heating rate when heating to the holding temperature was 8.0°C / min, the holding temperature was 900°C, the holding time was 1.0 hour, and the cooling rate when cooling from the holding temperature to room temperature was 50°C / min. The atmosphere during the first aging treatment was an Ar atmosphere.

[0065] In the second aging treatment, the heating rate when heating to the holding temperature was 8.0°C / min, the holding temperature was 500°C, the holding time was 1.5 hours, and the cooling rate when cooling from the holding temperature to room temperature was 50°C / min. The atmosphere during the second aging treatment was an Ar atmosphere.

[0066] The composition of the R-T-B system permanent magnets finally obtained in each example and comparative example was confirmed to be the composition shown in Tables 1 to 4 by composition analysis using X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry (ICP method), and gas analysis. In particular, the C content was measured by oxygen flow combustion-infrared absorption spectrometry. The B content was also measured by ICP method.

[0067] (Evaluation) The magnetic properties of the RTB-based permanent magnets made from the raw material alloys of each example and comparative example were measured using a BH tracer. L and HcJ H was measured, and Hk / HcJ was measured. L + (HcJ H The results are shown in Tables 1 to 4.

[0068] In the RTB-based permanent magnet of this embodiment, HcJ H ≧600, Br L + (HcJ H / 3)≧1565 and Hk / HcJ of 92.0% or more was evaluated as good.

[0069]

[0070]

[0071]

[0072]

[0073] Table 1 shows examples and comparative examples in which the B content and Al content were mainly changed. In each example in which the B content was 0.70 mass % or more and 0.83 mass % or less and the Al content was more than 0 and less than 0.20 mass %, the HcJ H ≧600, Br L + (HcJ H / 3)≧1565, and Hk / HcJ was 92.0% or more. In contrast, in Comparative Example 3, in which the B content was too small, sintering did not proceed sufficiently. L + (HcJ H In each of the comparative examples in which the B content was too large, the HcJ H In each of the comparative examples in which the Al content was too large, the HcJ H ≧600 or Br L + (HcJ H / 3)≧1565 was not satisfied.

[0074] Table 2 shows examples and comparative examples in which the Co content was mainly changed in Example 9. Furthermore, for reference, comparative examples in which the Co content was mainly changed when the Al content was too high, and comparative examples in which the Co content was mainly changed when the B content was too high are also shown. Each example in which the Co content was more than 0.80 mass% and 3.00 mass% or less had a low HcJ. H ≧600, Br L + (HcJ H In contrast, in the comparative example in which the B content was 0.70 mass % or more and 0.83 mass % or less but the Co content was too small, Br L + (HcJ H / 3)≧1565, and Hk / HcJ was significantly reduced. L + (HcJ H / 3) ≧ 1565. H ≧600 was not met.

[0075] Table 3 shows examples and comparative examples in which the R content (TRE), Cu content, Ga content, or Zr content was mainly changed. Each example in which the contents of all elements were within the specified range had a HcJ of 1. H ≧600, Br L + (HcJ H / 3)≧1565, and the Hk / HcJ was 92.0% or more. In contrast, the comparative examples in which the R content (TRE), Cu content, Ga content, or Zr content was outside the specified range all had an HcJ H ≧600 or Br L + (HcJ H / 3)≧1565 was not satisfied.

[0076] Table 4 shows examples 9 and 12 in which the ratio of Nd to Pr was kept constant and part of Nd and part of Pr was replaced with Dy or Tb. Even when part of Nd and part of Pr were replaced with Dy or Tb, each example in which the contents of all elements were within the specified range had a low HcJ. H ≧600, Br L + (HcJ H / 3)≧1565, and Hk / HcJ was 92.0% or more.

Claims

1. An R-T-B system permanent magnet containing Al, Cu, Ga and Zr, The R-T-B system permanent magnet is taken as 100 mass %, The content of R is 30.00 mass% or more and 33.00 mass% or less, The Co content is 0.85 mass% or more and 3.00 mass% or less, The B content is 0.70 mass% or more and 0.83 mass% or less, The Al content is greater than 0 mass% and less than 0.20 mass%; The Cu content is greater than 0.10 mass% and less than 1.50 mass%; The Ga content is 0.40 mass% or more and 1.00 mass% or less, An RTB system permanent magnet having a Zr content of more than 0.10 mass % and not more than 1.60 mass %.

2. 2. The R-T-B system permanent magnet according to claim 1, wherein the C content is from 0.05% by mass to 0.30% by mass.

3. 3. The R-T-B system permanent magnet according to claim 1, wherein the content of heavy rare earth elements is from 0% by mass to 0.30% by mass.

4. The residual magnetic flux density of the R-T-B system permanent magnet at room temperature is Br L (mT), the coercive force of the R-T-B permanent magnet at 150° C. is HcJ H As (kA / m), HcJ H ≧600, Br L + (HcJ H / 3)≧1565, 3. The RTB system permanent magnet according to claim 1, which has a squareness ratio of 92.0% or more at room temperature.