JP2009054704A - Manufacturing method of rare earth permanent magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high oilproof sintered permanent magnet, with ease at a low cost, which has corrosive resistance and hydrogen barrier property even in the atmosphere of high temperature and high pressure of coolant and lubricating oil, by forming a protective film in a thermal process after treating the surface of a processed R-T-B permanent magnet in an alkali solution containing alkanolamine. <P>SOLUTION: In the manufacturing method of the R-T-B rare earth permanent magnet, it is submerged in a coolant and/or lubricating oil for long hours. The R-T-B sintered magnet is cut and/or polished to finish the surface, and then it is submerged in the alkali solution containing alkanolamine for 1-100 hours. Then, it is thermally treated at 200-350°C for 0.5-24 hours in the atmosphere in which the oxygen partial pressure is 1.3×10<SP>3</SP>Pa (10 Torr) or higher. Since the surface of the R-T-B permanent magnet processed is treated in the alkali solution containing alkanolamine and then subjected to a thermal process to form a protective film, the high oilproof sintered permanent magnet having corrosive resistance and hydrogen barrier property even in such atmosphere of high temperature and high pressure of coolant and lubricated oil can be constituted simply at a low cost. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a rare-earth permanent magnet that is immersed in a refrigerant and / or lubricating oil for a long time, particularly a permanent magnet that is effective for use in a high-efficiency motor for air conditioning.

  Rare earth permanent magnets are used in many fields of electrical and electronic equipment because of their excellent magnetic properties and economy, and their production volume has been increasing rapidly in recent years. Among these, rare earth-based permanent magnets have a lower raw material cost and magnetic properties due to the fact that the main element Nd is more abundant than Sm compared to rare earth cobalt magnets (SmCo), and that a large amount of Co is not used. Since it far surpasses rare earth cobalt magnets, it is widely applied not only to small magnetic circuits where rare earth cobalt magnets have been used, but also to fields where hard ferrites or electromagnets were used. DC brushless motors that use rare earth magnets instead of conventional induction motors and synchronous rotating machines that use ferrite magnets to increase energy efficiency and reduce power consumption in compressor motors such as air conditioners and refrigerators The transition to is progressing.

  Among revolving motors, reluctance torque applied motors that use reluctance torque mainly or in an auxiliary manner are attracting attention, and their practical application is rapidly becoming the most efficient motor mainly in the home appliance field such as air-conditioning compressors and the automobile field. Progressing. In particular, air conditioning equipment accounts for about 25% of the electric power used in general households, and it is important to improve the efficiency of air conditioning motors.

  The reluctance torque applied motor includes a switched reluctance motor (SRM), a synchronous reluctance motor (SynRM), and a PM motor (IPMSM) having an embedded magnet structure. The reluctance torque, permanent magnet magnetic flux, and armature current The ratio of the generated magnet torque varies depending on the product. IPMSM, which is a hybrid of magnet torque and reluctance torque, embeds a permanent magnet in the rotor, increases the inductance, and appropriately controls the drive current to control the magnetic flux with less current in addition to using the reluctance torque. It becomes. Accordingly, the IPMSM has characteristics such as high efficiency in a wide range from low speed to high speed, constant output in a wide range, high speed low torque, small size and light weight. It is considered that a high-efficiency air-conditioning motor that takes advantage of these characteristics can achieve a reduction in annual electricity costs and high heating capacity.

  Since the RTB-based permanent magnet contains rare earth elements and iron as main components, it has a drawback that it easily oxidizes in a short time in humid air. When incorporated in a magnetic circuit, there have been problems such as a reduction in the output of the magnetic circuit due to these oxidative corrosions, and contamination of peripheral equipment due to the generated rust. For this reason, in general, rare earth magnets are used after surface treatment. As surface treatment methods for rare earth magnets, electroplating, electroless plating, Al ion plating, and various types of coating are used.

  A rare earth permanent magnet used in a compressor motor for an air conditioner used in a refrigerant, lubricating oil, or a mixed system thereof is required to have corrosion resistance under high temperature and high pressure in a mixed system of these refrigerant and refrigeration oil.

  For example, Japanese Patent Application Laid-Open No. 11-150930 (Patent Document 1) proposes to use a magnet material that is not subjected to surface treatment for a rare earth magnet in an iron core of a rotor in a refrigerant compressor. However, the combination of the HFC refrigerant and the ether-based or ester-based refrigerating machine oil may reduce the magnetic characteristics of the incorporated magnet due to high-temperature and long-time operation.

  Therefore, in these applications, the application of the above-mentioned various surface treatments is considered. For example, the Al ion plating method is expensive and industrially problematic, and the coating reacts with a solvent or oil. In addition, the plating method cannot be used due to problems with stability at high temperatures, such as the plating film peeling off at the shrink fitting temperature of the rotor and shaft, and these surface treatments are large magnets Is difficult to industrialize, and many plating defects occur.

  Thus, rare earth permanent magnets used in high-efficiency motors have a problem that their magnetic properties deteriorate when they are immersed in a high-temperature / high-pressure refrigerant and / or lubricating oil for a long time and react or corrode with them. There is.

As the R-T-B-based permanent magnet having a high reliability against these special operating environment, JP at 2002-57052 (Patent Document 2), an oxygen partial pressure of the sintered magnet was obtained 10 ^{- 6-10} argon is ⁰ Torr, nitrogen, or at a low pressure vacuum atmosphere, method of heat treating 10 minutes to 10 hours have been proposed. However, an expensive atmosphere furnace is required for a uniform heat treatment atmosphere, and therefore, a cheaper and simpler method has been demanded.

Japanese Patent Laid-Open No. 11-150930 JP 2002-57052 A

  The present invention solves the above-mentioned problems, and provides a cheaper and simpler method for producing a rare earth permanent magnet having excellent stability, high corrosion resistance and hydrogen barrier properties even under the severe use conditions as described above. It is to provide.

In order to achieve the above object, the present invention
(1) In the method for producing a rare earth permanent magnet immersed in a refrigerant and / or lubricating oil for a long time, the main component is R (R is a combination of one or more rare earth elements), T (T is Fe, or Fe and Co), and B, R is 26.8 to 33.5 mass%, B is 0.78 to 1.25 mass%, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo , Zn, Pb, Sb, Al, Si, V, Cr, Ti, Cu, Ca, Mg, the total amount of one or more elements selected from 0.05 to 3.5 mass%, the balance being T Cast an alloy consisting of inevitable impurities and pulverize it in an oxygen, nitrogen, or vacuum oxygen-free atmosphere, and then perform fine pulverization, molding in a magnetic field, sintering, and aging in order to obtain a sintered magnet whose oxygen concentration is 0.3 to 0.8% by mass, and magnetic properties of Br are 12.0 kG or more and 14.8 k Thereafter, a sintered magnet having an iHc of 11 kOe or more and 35 kOe or less is cut and / or polished to finish the surface, and then immersed in an alkaline solution containing alkanolamines for 1 to 100 hours. A method for producing a rare earth permanent magnet, characterized by heat treatment at 200 to 350 ° C. for 0.5 to 24 hours in an atmosphere of 3 × 10 ³ Pa (10 Torr) or more,
(2) In the method for producing a rare earth permanent magnet immersed in a refrigerant and / or lubricating oil for a long time, the main component is R (R is a combination of one or more rare earth elements), T (T is Fe, or Fe and Co), and B, R is 26.8 to 33.5 mass%, B is 0.78 to 1.25 mass%, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo , Zn, Pb, Sb, Al, Si, V, Cr, Ti, Cu, Ca, Mg, the total amount of one or more elements selected from 0.05 to 3.5 mass%, the balance being T And an alloy composed of inevitable impurities is a mother alloy, R ′ (R ′ is one or a combination of two or more rare earth elements) is 28 to 70% by mass, B is 0 to 1.5% by mass, Ni, Ga , Zr, Nb, Hf, Ta, Mo, Al, Si, V, Cr, Ti, Cu The total amount of two or more elements is 0.05 to 10% by mass, the balance is T (the proportion of Co in T is 10% by mass or more and the proportion of Fe is 90% by mass or less) and inevitable impurities. An alloy is used as an auxiliary material, and a mother alloy obtained by hydrogenation and pulverization in an oxygen, argon, or vacuum oxygen-free atmosphere is mixed at a ratio of 85 to 99% by mass and the auxiliary material is mixed at a rate of 1 to 15% by mass, and then finely pulverized Molding, sintering, and aging are sequentially performed to obtain a sintered magnet having an oxygen concentration of 0.3 to 0.8 mass%, a magnetic property of 12.0 kG to 14.8 kG in Br, and iHc of 11 kOe to 35 kOe. The sintered magnet is cut and / or polished to finish the surface, and then immersed in an alkaline solution containing alkanolamines for 1 to 100 hours. Subsequently, the oxygen partial pressure is 1.3 × 10 ³ Pa (10 Torr) In the above atmosphere, 2 Provides a method for preparing a rare earth permanent magnet, characterized in that the heat treatment for 0.5 to 24 hours at 0 to 350 ° C.. In this case, the rare earth permanent magnet is suitable for a high efficiency motor in which the magnet is immersed in a refrigerant and / or lubricating oil.

That is, as a result of intensive studies to solve the above problems, the present inventor has been used in various high-efficiency motors (motors that can comply with the revised Energy Conservation Law). In a rare earth magnet immersed in a lubricating oil for a long time, the surface-finished magnet is immersed in an alkaline solution containing alkanolamines for 1 to 100 hours. Subsequently, it was found that the corrosion resistance is improved by heat treatment for 0.5 to 24 hours in an atmosphere having an oxygen partial pressure of 1.3 × 10 ³ Pa (10 Torr) or more in a temperature range of 200 to 350 ° C. Is completed.

  According to the present invention, the surface of the RTB-based permanent magnet subjected to the processing treatment is treated with an alkali solution containing alkanolamine, and then a protective film is formed by heat treatment. A highly oil-resistant sintered permanent magnet having corrosion resistance and hydrogen barrier properties even in an atmosphere can be provided simply and inexpensively, and its utility value is extremely high in industry.

Hereinafter, the present invention will be described in more detail.
In the method for producing a rare earth permanent magnet of the present invention, first, the main component is R (R is one or a combination of two or more rare earth elements), T (T is Fe, or Fe and Co), and B. R is 26.8-33.5% by mass, B is 0.78-1.25% by mass, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, Pb, Sb, Al, Casting an alloy in which the total amount of one or more elements selected from Si, V, Cr, Ti, Cu, Ca, Mg is 0.05 to 3.5% by mass, the balance being T and inevitable impurities To do.

  Here, R used for the RTB-based permanent magnet is a rare earth element including Y and occupies 26.8 to 33.5% by mass of the composition, and as R, Y, La, Ce, One or two or more selected from Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Lu, Yb are used. Among these, Ce, La, Nd, Pr, Dy, Tb are used. It is preferable to include at least one of them. B is in the range of 0.78 to 1.25% by mass. The balance T is Fe, or Fe and Co. In particular, Fe is in the range of 50 to 90% by mass in the alloy. In this case, the temperature characteristics can be improved by replacing part of Fe with Co. However, if the amount of Co added is less than 0.1% by mass, a sufficient effect cannot be obtained. On the other hand, if it exceeds 15% by mass, the coercive force may decrease and the cost may increase. 1-15 mass% is preferable. Further, in order to improve magnetic characteristics or reduce costs, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, Pb, Sb, Al, Si, V, Cr, Ti, Cu At least one selected from Ca, Mg can be added. An alloy having such a composition can be obtained by melting it above the melting point of the alloy and by a casting method such as a die casting method, a roll quenching method, or an atomizing method.

  After the alloy having the above composition is pulverized in an oxygen-free atmosphere of argon, nitrogen or vacuum, it is preferably finely pulverized to an average particle size of 1 to 30 μm, and oriented compression molding in a magnetic field or compression molding in a non-magnetic field, sintering, solution treatment A permanent magnet having a desired practical shape can be obtained by bulking by aging, grinding and polishing.

  The rare earth magnet has R as a main component (R is one or a combination of two or more rare earth elements including Y), T (T is Fe, or Fe and Co), and B. R is 26.8 to 33.5 mass%, B is 0.78 to 1.25 mass%, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, Pb, Sb, Al, An alloy composed of 0.05 to 3.5% by mass of one or more elements selected from Si, V, Cr, Ti, Cu, Ca, and Mg, with the balance being T and the inevitable impurities. R ′ (R ′ is one or a combination of two or more rare earth elements including Y similar to R) is 28 to 70% by mass, B is 0 to 1.5% by mass, Ni, Ga, One or more selected from Zr, Nb, Hf, Ta, Mo, Al, Si, V, Cr, Ti, Cu A total of 0.05 to 10% by mass of elements, the balance being T (the proportion of Co in T being 10% by mass or more and the proportion of Fe being 90% by mass or less) and an alloy consisting of inevitable impurities are used as auxiliary materials. After mixing the master alloy hydrogenated and pulverized in an oxygen-free atmosphere of argon, nitrogen or vacuum at a ratio of 85 to 99% by mass and auxiliary material at a rate of 1 to 15% by mass, pulverization, molding in a magnetic field, sintering It can also be obtained by sequentially performing aging, and further cutting and / or polishing to finish the surface (so-called two-alloy method).

  The sintered magnet (permanent magnet) obtained here has an oxygen concentration of 0.3 to 0.8% by mass, a magnetic property of 12.0 kG to 14.8 kG in Br, and iHc of 11 kOe to 35 kOe. is there.

In the present invention, the surface is processed and finished as described above, and then immersed in an alkaline solution containing alkanolamine, followed by heat treatment.
In this case, the surface of the R-T-B system permanent magnet has a property of being easily rusted in the atmosphere. In fact, for example, in the case of an Nd—Fe—B magnet, neodymium hydroxide is produced together with iron oxide which is a rust component if left in the atmosphere for a long time. When immersed in an alkaline solution containing alkanolamines and optionally a surfactant of 0.5 to 20% by mass after machining, neodymium hydroxide Nd (OH) is almost uniformly formed on the surface of the RTB rare earth permanent magnet. ₃ ) R hydroxide such as ₃ can be generated. The immersion time in the alkaline solution is 1-100 hours, preferably 8-72 hours, more preferably 12-24 hours, and it may be immersed at room temperature (for example, 20 ° C.) to 40 ° C.

  The solution in which the R-T-B permanent magnet is immersed after machining has an alkanolamine concentration of 0.1 or more selected from sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate and further dissolved. An aqueous solution of 01 to 2.0 mol / L, particularly 0.05 to 0.5 mol / L is preferable. The alkali concentration is preferably 1 to 10% by mass, particularly 2 to 8% by mass. Preferably, it is immersed in an alkaline solution (pH 8.5 or more, more preferably pH 8.5 to 11.5) containing an alkanolamine such as monoethanolamine or diethanolamine and a surfactant.

  As the alkanolamine used in the present invention, one or more of monoethanolamine, diethanolamine, triethanolamine, triisopropanolamine, methylethanolamine, monoisopropanolamine and the like can be selected. If necessary, an anionic surfactant Is preferably added.

  Examples of the anionic surfactant include linear alkyl benzenes such as sodium linear alkyl benzene sulfonate, alpha olefins such as sodium alpha olefin sulfonate, and fatty acids such as fatty acid sodium and fatty acid potassium.

  It may be washed after being immersed in an alkaline solution, and may be used in combination with not only ultrasonic cleaning using pure water but also solvent cleaning by immersion in an organic solution such as ethyl alcohol. Subsequently, the surface of the R-T-B system permanent magnet is sufficiently dried with a dryer or the like.

  In the present invention, the permanent magnet is then heat-treated, thereby improving the corrosion resistance. In this case, the heat treatment temperature is 200 to 350 ° C, preferably 250 to 330 ° C, more preferably 280 to 300 ° C. If the heat treatment temperature is too high, the magnetic properties are deteriorated, and if it is too low, the durability against the lubricating oil is deteriorated.

The atmosphere of the heat treatment is an oxygen atmosphere having an oxygen partial pressure of 1.3 × 10 ³ Pa (10 Torr) or more, more preferably 2.1 × 10 ⁴ Pa or more, and the heat treatment time is 0.5 to 24 hours, More preferably, it is 0.5-6 hours, More preferably, it is 1-2 hours. An oxygen partial pressure of less than 1.3 × 10 ³ Pa is not preferable because uniform discoloration does not occur. The upper limit of the oxygen partial pressure is preferably 2.1 × 10 ⁶ Pa or less, particularly 2 × 10 ⁵ Pa or less.

A heat treatment is performed on the surface of the R-T-B rare earth permanent magnet, in which an R hydroxide such as Nd (OH) ₃ is generated, whereby a uniform composite oxide layer is formed. It turns dark blue. On the other hand, if the R-T-B rare earth permanent magnet is machined to a desired size and then immediately heat treated, the magnet surface does not become a uniform dark blue color but exhibits a brown to brown color.

  Generally, the atmosphere in the heat treatment is called “oxidizing atmosphere” if oxygen is present, and conversely, “reducing atmosphere” if oxygen is small. In the present invention, a hydroxide of R such as neodymium hydroxide is generated on the surface layer of the R-T-B system permanent magnet, and the formation of a composite oxide by heat treatment of this produces a higher oxygen partial pressure. This is equivalent to performing heat treatment in an oxidizing atmosphere.

Therefore, in order to form a uniform lower oxide film on the surface after heat treatment when the R-T-B system rare earth permanent magnet is not immersed in an alkaline solution containing alkanolamines at pH 8.5 or higher, particularly pH 9 or higher. Therefore, it is necessary to increase the oxygen partial pressure to, for example, 6.5 × 10 ⁴ Pa or more. However, when immersed in an alkaline solution containing alkanolamines, preferably pH 8.5 or higher, particularly pH 9 or higher, the treatment can be performed at a lower oxygen partial pressure of 1.3 × 10 ³ Pa or more, which is more convenient. Moreover, its significance is very great from the viewpoint of safety during heat treatment.

  In addition, you may cool the RTB type | system | group permanent magnet heat-processed by desired atmosphere and temperature at the cooling rate of 10-2000 degrees C / min. In some cases, it is possible to perform heat treatment in multiple stages. If necessary, a heat-treated RTB-based permanent magnet may be subjected to a so-called rapid quenching treatment with cold water or a cooling medium. As the cooling medium used for the quenching and quenching treatment, not only cold water but also a weak acid solution in which phosphoric acid, citric acid, oxalic acid and the like are dissolved, or a weak alkali solution in which potassium carbonate and the like are dissolved can be used.

  By performing the heat treatment in this manner, the surface of the R-T-B permanent magnet has a lower oxide (such as rare earth and iron, rare earth and iron, rare earth hydroxide and hydrate which are difficult to be formed in a normal atmospheric atmosphere). A thin layer made of mixed complex oxide can be formed, and a high-efficiency rare earth permanent magnet for motors with good corrosion resistance can be obtained.According to XPS (X-ray photoelectron spectroscopy) analysis, the surface treatment film thickness is 60 This surface-treated film not only prevents oxidation as typified by high-temperature and high-humidity environmental tests, but it is also a very thin film with excellent hydrogen barrier properties. This is a surface treatment method for a thin film.

  The magnets obtained by the present invention are particularly refrigerants such as HFC (for example, R410A, R134a, R125, R407c, R404A, etc.), HCFC (R22, R32, etc.) and natural refrigerant (carbon dioxide (R-744)). And high corrosion resistance to lubricating oils (refrigeration oils: mineral oils, ester oils, ether oils, polyethylene glycols, etc.) and maintained at high temperatures of 100 to 150 ° C. and high pressures of 2.0 to 6.0 MPa for 500 hours or more. However, the magnetic characteristics are not deteriorated. Therefore, it is characterized in that it is not affected at all by the type of refrigerant used, the type of refrigerating machine oil, the chemical structure and the like.

  Air conditioning motors, that is, compressor (compressor) motors, are constantly heated to a high temperature (up to about 100 ° C). ) And is exposed to a high-pressure environment.

  When ester oil (main component polyol ester) is used as a refrigerating machine oil for an air conditioning motor, the ester oil itself has high hygroscopicity, and moisture is mixed into the oil unless it is sufficiently managed. Due to this mixed water, when it is exposed to a high temperature, hydrolysis proceeds gradually, and as a result, metal soap may be generated, and in the worst case, the capillary may be blocked. Actually, several hundred ppm of moisture is mixed in the refrigerating machine oil inside the air conditioning motor. Therefore, if 2,000 ppm of water is intentionally mixed in the refrigerating machine oil and reliability in a high-temperature / high-pressure environment simulating the environment where the air-conditioning motor is used is ensured, it is practically RTB. The system permanent magnet is considered to have no problem. It is also possible to evaluate the long-term reliability of an actual machine in a short time.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1]
An ingot having a composition of 32Nd-1.2B-59.8Fe-7Co by mass ratio was produced by high-frequency melting in an Ar atmosphere. This ingot was coarsely pulverized with a jaw crusher and further finely pulverized with a jet mill using nitrogen gas to obtain a fine powder having an average particle size of 3.5 μm. Next, this fine powder was filled into a mold to which a 10 kOe magnetic field was applied and molded at a pressure of 1.0 t / cm ² . Next, sintering was performed in vacuum at 1,100 ° C. for 2 hours, and further aging treatment was performed at 550 ° C. for 1 hour to obtain a permanent magnet. From the obtained permanent magnet, a magnet piece of length 6.0 mm × width 6.0 mm × thickness 2.0 mm, oxygen concentration 0.61 mass%, Br = 12.0 kG, iHc = 21.02 kOe was cut out and barrel-polished. After the treatment, the substrate was immersed in a 30% aqueous triethanolamine solution at room temperature for 24 hours, and then ultrasonically washed with pure water. Thereafter, the RTB permanent magnet was heat-treated for 2 hours in an apparatus heated to 300 ° C. (oxygen partial pressure 2.1 × 10 ⁴ Pa), and this was used as a test piece. The amount of oxygen was measured by an inert gas melting infrared method (in a helium stream, heated to about 2,450 ° C. in a C crucible, and infrared absorption of CO gas was converted to a concentration).

  After weighing 20 g of commercially available ester refrigerating machine oil (RB-68P manufactured by Japan Energy Co., Ltd.) in a cap bolt type pressure vessel [capacity 200 ml (pressure glass industry TPR type N2 type)] as a pressure vessel, Karl Fischer method Pure water was injected with a microsyringe so that the predetermined amount of water in oil was obtained from the amount of water in oil determined in step 1. Subsequently, the R-T-B permanent magnet of the test piece was put and the container was fastened. The entire cap bolt type pressure vessel was cooled with dry ice and ethanol cryogen, and chlorofluorocarbon R410A as a refrigerant was injected as a liquid. The amount of the chlorofluorocarbon injected from the increase in the mass of the entire pressure vessel was measured, and the chlorofluorocarbon gas R410A was set to a mass of 20 g, that is, the mass ratio of the refrigerant to the refrigerating machine oil was set to 1. In general, these methods are a method of evaluating corrosion resistance of a compressor called a tube test. The moisture content in the oil was adjusted to 200 ppm, 1,000 ppm, and 2,000 ppm, and the whole pressure vessel was placed in a thermostat controlled at 150 ± 0.5 ° C. and heated for a predetermined time (500 hours). Thereafter, the pressure vessel was opened, the R-T-B magnet was taken out, and the change in its magnetic characteristics was examined. The results are shown in FIG. Magnetic properties were measured by VSM.

[Comparative Example 1]
Except for not performing heat treatment, the same R—Fe—B permanent magnet as in Example 1 was used as a test piece, and the water content in oil was adjusted to 200 ppm, 1,000 ppm, and 2,000 ppm, and 150 ± Place the entire pressure vessel in a thermostatic device controlled at 0.5 ° C and heat for 500 hours, then open the pressure vessel, take out the R-T-B magnet, and perform a similar tube test to examine the change in its magnetic properties. went. The results are shown in FIG.

[Example 2]
In the present invention, an attempt was made to further improve the characteristics by utilizing the two-alloy method. As starting materials, Nd, Dy, electrolytic iron, Co, ferroboron, Al, and Cu were used, and the mother alloy and auxiliary material were weighed as shown in Table 1.

Next, 92% by mass of the master alloy and 8% by mass of the auxiliary material were weighed, 0.05% by mass of zinc stearate as a lubricant was mixed with a V mixer, and further treated with a jet mill in a nitrogen stream, and the average A fine powder having a particle size of about 4 μm was obtained. Thereafter, these fine powders are filled in a mold of a molding apparatus, oriented in a magnetic field of 12 kOe, and the compact is subjected to 1,020 ° C. to 10 ° C. at a pressure of 0.5 ton / cm ^{2 in} a direction perpendicular to the magnetic field. Each sintered to 1,100 ° C for 2 hours in a vacuum atmosphere of 10 ^-4 Torr or less, further cooled, and then aged at 500 ° C for 1 hour in a vacuum atmosphere of 10 ^-2 Tott or less Obtained material. Note that the carbon and oxygen contents in the RTB-based permanent magnet material were 0.063 mass% and 0.457 mass%, respectively. At this time, Br was 12.8 kG and iHc was 22.8 kOe.

  About Example 2, in the same manner as in Example 1, the moisture content in the ester oil was adjusted to 2,000 ppm, and the entire pressure vessel was placed in a thermostatic device controlled at 150 ± 0.5 ° C. Then, after heating for a predetermined time (500 hours), the pressure vessel was opened, the R-T-B permanent magnet was taken out, and the change in its magnetic characteristics was examined. The result is shown in FIG.

  FIG. 4 shows changes in the magnetic properties after heating at 150 ° C. for 500 hours at a water content of 2,000 ppm in oil of Example 1 and Comparative Example 1. As is apparent from FIG. 4, the characteristics of the R-T-B permanent magnet greatly deteriorate depending on the amount of water in the refrigerating machine oil if heat treatment is not performed. In Example 1, no deterioration of the magnetic properties is observed regardless of the amount of water in the oil. No deterioration of the magnetic properties is observed with respect to a water content of 2,000 ppm far exceeding the water content of the refrigerating machine oil in an actual air conditioning motor.

[Comparative Example 2]
In Comparative Example 2, an evaluation sample was prepared as follows. A sintered magnet was produced by the same method as in Example 1 and processed into a desired magnet shape. It was immersed in the above-mentioned triethanolamine aqueous solution at room temperature for 24 hours, and then ultrasonically washed with pure water. This was subjected to heat treatment (300 ° C. × 2 hours) at an oxygen partial pressure of 0.8 × 10 ³ Pa. Adjust the moisture content in the oil to 2,000 ppm, put the whole pressure vessel in a thermostatic device controlled at 150 ± 0.5 ° C, heat for a predetermined time (500 hours), open the pressure vessel, -T-B magnet was taken out and a similar tube test was conducted to examine the change in its magnetic properties. The results are shown in FIG.

In Example 1, when performing a tube test, a commercially available ester refrigerating machine oil whose water content was adjusted to 200 ppm, 1,000 ppm, and 2,000 ppm was used, and a test was conducted at 150 ° C. for 500 hours using R410A as a refrigerant. It is a graph which shows the magnetic characteristic of the RTB system permanent magnet after performing. In Comparative Example 1, when the tube test was performed, R in the case where the water content of the commercially available ester refrigerating machine oil was adjusted to 200 ppm, 1,000 ppm, and 2,000 ppm and the test was performed at 150 ° C. for 500 hours. It is a graph which shows the magnetic characteristic of -TB system permanent magnet. In Example 2, when the tube test was performed, a commercially available ester refrigerating machine oil whose water content was adjusted to 2,000 ppm was used, and the RTB-based permanent when tested at 150 ° C. for 500 hours. It is a graph which shows the magnetic characteristic of a magnet. It is a graph which shows the magnetic characteristic change after 150 degreeC * 500-hour tube test implementation in Example 1 and Comparative Example 1 in water | moisture content in oil of 2,000 ppm. In Comparative Example 2, when the tube test is performed, a commercially available ester refrigerating machine oil whose water content is adjusted to 2,000 ppm is used, and the R-T-B system permanent when the test is performed at 150 ° C. for 500 hours. It is a graph which shows the magnetic characteristic of a magnet.

Claims (3)

In a method for producing a rare earth permanent magnet immersed in a refrigerant and / or lubricating oil for a long time, the main component is R (R is one or a combination of two or more rare earth elements), T (T is Fe, or Fe and Co) ) And B, R is 26.8-33.5% by mass, B is 0.78-1.25% by mass, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, The total amount of one or more elements selected from Pb, Sb, Al, Si, V, Cr, Ti, Cu, Ca, and Mg is 0.05 to 3.5% by mass, and the balance is T and inevitable. After casting an alloy made of impurities and pulverizing it in an oxygen-free atmosphere of argon, nitrogen or vacuum, it is finely pulverized, molded in a magnetic field, sintered and aged sequentially to form a sintered magnet, and its oxygen concentration is 0.3 ~ 0.8% by mass, and magnetic properties of Br are 12.0 kG or more and 14.8 kG or less After iHc was finishing the cutting and / or polishing the surface of the magnet is less than 35kOe above 11KOe, immersed 1-100 hours in an alkaline solution containing alkanolamines, subsequently oxygen partial pressure 1.3 × 10 ³ A method for producing a rare earth permanent magnet, comprising performing heat treatment at 200 to 350 ° C. for 0.5 to 24 hours in an atmosphere of Pa (10 Torr) or more. In a method for producing a rare earth permanent magnet immersed in a refrigerant and / or lubricating oil for a long time, the main component is R (R is one or a combination of two or more rare earth elements), T (T is Fe, or Fe and Co) ) And B, R is 26.8-33.5% by mass, B is 0.78-1.25% by mass, Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, The total amount of one or more elements selected from Pb, Sb, Al, Si, V, Cr, Ti, Cu, Ca, and Mg is 0.05 to 3.5% by mass, and the balance is T and inevitable. An alloy made of impurities is a mother alloy, R ′ (R ′ is one or a combination of two or more rare earth elements) is 28 to 70 mass%, B is 0 to 1.5 mass%, Ni, Ga, Zr, One or more selected from Nb, Hf, Ta, Mo, Al, Si, V, Cr, Ti, Cu A total of 0.05 to 10% by mass of the elements, and the balance is T (the proportion of Co is 10% by mass or more and the proportion of Fe is 90% by mass or less in T) and an inevitable impurity alloy. After mixing the master alloy hydrogenated and pulverized in an oxygen, argon or vacuum oxygen-free atmosphere at a ratio of 85 to 99 mass% and auxiliary material at a ratio of 1 to 15 mass%, finely pulverized, molded in a magnetic field, sintered A sintered magnet is formed by sequentially aging, a magnet having an oxygen concentration of 0.3 to 0.8% by mass, a magnetic property of Br of 12.0 kG to 14.8 kG, and iHc of 11 kOe to 35 kOe. After cutting and / or polishing to finish the surface, the surface is immersed in an alkali solution containing alkanolamines for 1 to 100 hours, and subsequently in an atmosphere having an oxygen partial pressure of 1.3 × 10 ³ Pa (10 Torr) or more, 200 ~ 350 ° C A method for preparing a rare earth permanent magnet, characterized in that the heat treatment for 0.5 to 24 hours Te.   The manufacturing method according to claim 1 or 2, wherein the rare earth permanent magnet is for a high efficiency motor in which the magnet is immersed in a refrigerant and / or lubricating oil.

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