JP5760400B2 - Method for producing R-Fe-B sintered magnet - Google Patents

Description

  The present invention relates to a method for producing an R—Fe—B based sintered magnet in which a part of a light rare earth element is substituted with a heavy rare earth element.

An R—Fe—B based sintered magnet having a R ₂ Fe ₁₄ B type compound phase as a main phase and containing a light rare earth element (RL: at least one selected from Nd and Pr) as a rare earth element R is a so-called As is well known, it is the most powerful magnet among magnets called permanent magnets. For this reason, R-Fe-B based sintered magnets are used in various applications such as voice coil motors (VCM) and motors for automobiles, home appliances, etc. The B-based sintered magnet has a characteristic that the coercive force decreases at a high temperature. Therefore, when the R—Fe—B based sintered magnet is exposed to a high temperature in an environment where it is used, it is necessary to take measures against a decrease in its coercive force.

As one of the above measures, the coercive force can be increased by replacing a part of RL constituting the R ₂ Fe ₁₄ B type compound phase with a heavy rare earth element (at least one selected from RH: Dy and Tb). Methods to improve are known. However, since RH is a scarce resource, it is required to reduce the amount used, and there is a problem that the residual magnetic flux density decreases when the replacement ratio of RL with RH increases. Therefore, as a method for improving the coercive force while suppressing the decrease in the residual magnetic flux density with a smaller amount of RH used, a method of diffusing and introducing RH from the outside to the R—Fe—B sintered magnet has been proposed. Yes. The research group of the present inventors has also conducted research on this method so far. For example, in Patent Document 1, an RH bulk body for diffusing and introducing an R—Fe—B based sintered magnet and RH from the outside into a processing chamber is disclosed. A method of performing heat treatment at 700 ° C. to 1000 ° C. in a vacuum or an inert gas (such as nitrogen gas or argon gas) atmosphere of 10 ⁻⁵ Pa to 500 Pa, for example, is proposed. According to this method, the RH supplied from the RH bulk body can be efficiently diffused and introduced from the surface of the magnet to the inside. However, as a result of subsequent studies by the present inventors' research group, not a few R-containing layers mainly composed of oxides and hydroxides of RL and RH are formed on the surface of the magnet into which RH is diffused and introduced. Turned out to be. The R-containing layer is present near the surface of the magnet that has been diffused and introduced from the outside due to diffusion and introduction of RL and RH that have been present near the surface of the magnet from outside. Formed by reaction of RH, etc. with oxygen and moisture remaining in the processing chamber during the heat treatment, oxygen and moisture contained in the atmosphere to which the magnet was exposed when the magnet was removed from the processing chamber after the heat treatment However, this R-containing layer is inferior in stability, causing a change in the weight of the magnet due to the progress of oxidative corrosion, a metal film, a resin film, etc. with excellent adhesion to the surface. It is difficult to form a corrosion-resistant film. Therefore, since the magnet manufactured by the method described in Patent Document 1 has room for improvement in these respects, the R-containing layer is removed by grinding the surface about several tens to 100 μm, and the surface is again formed. It is desirable to form and use a corrosion-resistant film.

International Publication No. 2007/102391

  Therefore, the present invention has an excellent corrosion resistance and can form a corrosion-resistant film such as a metal film or a resin film on the surface with excellent adhesion. A part of RL is substituted with RH. It aims at providing the manufacturing method of a B type sintered magnet.

  As a result of intensive studies in view of the above points, the present inventors have conducted a process of introducing RH from the outside by the method described in Patent Document 1 with respect to the R-Fe-B sintered magnet to be processed. After performing the heat treatment in a predetermined oxidizing atmosphere with a water vapor partial pressure of less than 10 hPa (1000 Pa), the surface of the magnet is modified to be stable and excellent in corrosion resistance, and RH is diffused and introduced. It was found that a corrosion-resistant film can be formed with excellent adhesion without removing the R-containing layer formed on the surface of the magnet.

The method for producing an R—Fe—B based sintered magnet obtained by replacing a part of the RL of the present invention based on the above knowledge with RH is as described in claim 1. -After performing Step A in which RH is diffused and introduced into the B-based sintered magnet from the outside, the oxygen partial pressure is 1 x 10 ³ Pa to 1 x 10 ⁵ Pa, the water vapor partial pressure is less than 1000 Pa, and The process B is characterized by performing heat treatment at 200 ° C. to 500 ° C. in an atmosphere having a ratio of oxygen partial pressure to water vapor partial pressure (oxygen partial pressure / water vapor partial pressure) of 450 to 20000.
The manufacturing method according to claim 2 is the manufacturing method according to claim 1, wherein the R—Fe—B based sintered magnet and the RH diffusion introducing material for diffusing and introducing the RH from the outside are relatively disposed in the processing chamber. The process A is performed by performing heat treatment at 500 ° C. to 1000 ° C. while moving both in a processing chamber continuously or intermittently.
The manufacturing method according to claim 3 is the manufacturing method according to claim 2, wherein an RH diffusion introducing material made of an alloy containing Fe in addition to RH is used.
The manufacturing method according to claim 4 is the manufacturing method according to claim 3, wherein the Fe content of the alloy is 30 mass% to 80 mass%.
The method according to claim 5, wherein, in the process according to any one of claims 1 to 4, the water vapor partial pressure of step B characterized by the following and to Rukoto 45 Pa.
A manufacturing method according to claim 6 is the manufacturing method according to any one of claims 1 to 5, wherein the R-Fe-B sintered magnet after step A is subjected to blasting and / or Step B is performed after the surface grinding process.
In addition, an R—Fe—B based sintered magnet in which a part of the RL of the present invention is substituted with RH is manufactured by the manufacturing method according to any one of claims 1 to 6 as described in claim 7. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, it has excellent corrosion resistance, and can form corrosion-resistant films, such as a metal film and a resin film, on the surface with excellent adhesiveness. R-Fe in which a part of RL is substituted by RH A method for producing a B-based sintered magnet can be provided.

It is a schematic diagram of an example of the suitable heat processing apparatus for performing the process A in this invention. It is a schematic diagram of an example of the suitable continuous processing furnace for performing the process B same as the above.

In the method for producing an R—Fe—B based sintered magnet in which a part of the RL of the present invention is replaced by RH, RH is diffused and introduced from the outside to the R—Fe—B based sintered magnet to be processed. After performing step A, the oxygen partial pressure is 1 × 10 ³ Pa to 1 × 10 ⁵ Pa, the water vapor partial pressure is less than 1000 Pa, and the ratio of the oxygen partial pressure to the water vapor partial pressure (oxygen partial pressure / water vapor Step B in which heat treatment is performed at 200 ° C. to 500 ° C. in an atmosphere having a partial pressure of 1 to 20000 is characterized. Hereinafter, each of the process A and the process B will be described.

1: About Step A Step A is a step of diffusing and introducing RH from the outside to the R—Fe—B based sintered magnet to be processed. Any method may be employed for this step as long as RH can be diffused and introduced from the outside into the R—Fe—B based sintered magnet. In addition to the method described above, a method of performing a heat treatment at 500 ° C. to 1000 ° C. after forming an RH film on the surface of the R—Fe—B based sintered magnet by a physical method such as vapor deposition or sputtering (for example, JP 2005-2005 A). No. 111973) or in a state where a powder made of RH fluoride or the like is present on the surface of an R—Fe—B based sintered magnet, and below the sintering temperature of the magnet in vacuum or in an inert gas. A method of performing heat treatment at a temperature (see, for example, International Publication No. 2006/043348) can be employed.

  Further, as step A, the R—Fe—B sintered magnet to be processed and the RH diffusion introducing material for introducing RH from outside are accommodated in the processing chamber so as to be relatively movable and close to or in contact with each other. And you may employ | adopt the method of heat-processing at 500 to 1000 degreeC, moving both in the processing chamber continuously or intermittently. According to this method, as in the method described in Patent Document 1, in addition to being able to efficiently diffuse and introduce RH from the outside into the R—Fe—B based sintered magnet, The surface modification of the magnet can be performed more effectively than when the step B is performed after the method described in Patent Document 1 is performed as the step A. Hereinafter, this method will be specifically described.

In this method, for example, a cylindrical container is used as a processing chamber, an R—Fe—B sintered magnet to be processed and an RH diffusion introducing material are accommodated therein, and the container is rotated around its central axis. And heating the container from the outside of the container. In this aspect, the R—Fe—B based sintered magnet and the RH diffusion introducing material are relatively movable in the processing chamber and are moved in proximity or in contact with each other, so that the RH diffusion introducing material is moved. In addition to being able to rapidly supply RH from the magnet by vaporization (sublimation) and diffusion of the supplied RH to the magnet, the state cannot be maintained for a long time even when both are in contact. Is preferable in that the welding of both can be prevented. FIG. 1 is a schematic view of an example of a suitable heat treatment apparatus for performing this method. In the example shown in FIG. 1, the R—Fe—B sintered magnet 1 and the RH diffusion introducing material 2 are accommodated in a cylindrical container 3 made of, for example, stainless steel, and the cylindrical container 3 is centered by a motor 7. The process is performed by rotating around the axis and heating with the heater 4 disposed on the outer periphery thereof. The rotation of the cylindrical container 3 is desirably performed at a peripheral speed of 0.01 m / second or more. This is because if the rotational speed is too slow, the time during which the R—Fe—B based sintered magnet 1 and the RH diffusion introducing material 2 are in contact with each other may become longer, and the two may be welded. On the other hand, it is desirable to rotate the cylindrical container 3 at a peripheral speed of 0.5 m / second or less. This is because if the rotational speed is too high, the R—Fe—B based sintered magnet 1 and the RH diffusion introducing material 2 may come into contact with each other violently, thereby causing the magnet to crack or chip. The R—Fe—B sintered magnet 1 and the RH diffusion introducing material 2 are taken in and out of the cylindrical container 3 through a lid 5 that can be opened and closed or removed. After the R—Fe—B sintered magnet 1 and the RH diffusion introducing material 2 are accommodated in the cylindrical container 3, the interior of the chamber is evacuated by the exhaust device 6, and in some cases, nitrogen gas is introduced into the chamber by a pipe not shown. It is desirable to perform the treatment in an atmosphere supplied with an inert gas such as argon gas. This is because if oxygen or moisture remains in the room, the R—Fe—B sintered magnet 1 and the RH diffusion introducing material 2 may be oxidized on the surface during processing. The indoor pressure is preferably 1 × 10 ⁻³ Pa to 1 × 10 ³ Pa.

  The RH diffusion introducing material for diffusing and introducing RH from the outside to the R—Fe—B based sintered magnet to be processed may be made of RH such as Dy or Tb. It may be made of an alloy containing other metal elements. In particular, an alloy containing Fe in addition to RH is preferable in that when it is used as an RH diffusion introducing material, an excellent surface modification effect on the magnet is brought about by the subsequent step B. Specific examples of such an alloy include alloys containing 30 mass% to 80 mass% Fe in addition to RH. The RH diffusion introducing material may have any shape such as a spherical shape, a wire shape, a plate shape, a block shape, and a powder shape. In the case of a sphere or powder, a diameter or particle size of 0.05 mm to 5 mm can be exemplified, and in the case of a wire, plate or block, the length is 1 mm to 5 cm. It can be illustrated. The amount of the RH diffusion introduction material accommodated in the processing chamber is R-Fe-B based sintered magnet from the viewpoint of efficient diffusion introduction of RH to the R-Fe-B based sintered magnet and cost. 0.1 to 100 times the weight (weight ratio) is desirable.

  In addition to the R—Fe—B sintered magnet and the RH diffusion introducing material, a stirring auxiliary material having a spherical shape, an elliptical shape, a cylindrical shape, or the like may be accommodated in the processing chamber. The agitation auxiliary material is interposed to assist in the delivery of RH from the RH diffusion introducing material to the R—Fe—B based sintered magnet. Play a role to prevent. The size is, for example, 1 mm to 3 cm in diameter and length. The material is not particularly limited as long as it does not have an adverse effect on the introduction of RH into the R—Fe—B based sintered magnet, but zirconia, silicon nitride, silicon carbide, Preferred examples include ceramics made of boron nitride, a mixture thereof, and the like. The amount of the stirring auxiliary material accommodated in the processing chamber is 0.1 with respect to the R—Fe—B based sintered magnet from the viewpoint of effectively obtaining the effect of using the stirring auxiliary material and the cost. ˜100 times is desirable (weight ratio).

  The temperature of the heat treatment is defined as 500 ° C. to 1000 ° C. If the temperature is lower than 500 ° C., there is a possibility that RH cannot be efficiently diffused and introduced into the R—Fe—B based sintered magnet. If it is higher than that, the R-Fe-B sintered magnet and the RH diffusion introducing material may be welded. In order to efficiently introduce RH into the R-Fe-B sintered magnet and improve the coercive force without reducing the residual magnetic flux density, the heat treatment temperature is desirably 700 ° C to 980 ° C. The heat treatment time is appropriately set depending on the amount of treatment of the R—Fe—B based sintered magnet, and is, for example, 10 minutes to 72 hours.

  In the above specific example, the R—Fe—B based sintered magnet and the RH diffusion introducing material are accommodated in the processing chamber so as to be relatively movable and close to or in contact with each other. As a method of intermittently moving, a method of rotating the cylindrical container around its central axis is adopted, but a method of moving both continuously or intermittently in the processing chamber is limited to this method. However, any method may be used as long as both can be made passive in the processing chamber by giving continuous or intermittent movement in the processing chamber.

Further, after performing the process A, an additional heat treatment may be additionally performed on the R—Fe—B based sintered magnet into which RH is diffusely introduced. As a suitable aspect, the combination of the 1st heat processing in 700 to 1000 degreeC and the 2nd heat processing in 400 to 700 degreeC is mentioned. According to such an aspect, the first heat treatment serves to diffuse the RH diffused and introduced into the magnet in the process A toward the inside of the magnet more uniformly, and the second heat treatment serves as an aging treatment. Fulfill. In this case, all the heat treatments are controlled to the same atmosphere (for example, pressure: 1 × 10 ⁻³ Pa to 1 × 10 ³ Pa) as the atmosphere adopted in the step A, and the first heat treatment is, for example, 1 hour to 12 hours, The second heat treatment may be performed for 2 hours to 5 hours, for example. Such an additional heat treatment for the R—Fe—B based sintered magnet into which RH has been diffused and introduced in the process A may be performed subsequently in the processing chamber in which the process A is performed. The R—Fe—B based sintered magnet and the RH diffusion introducing material into which RH is introduced by diffusion are taken out from the processing chamber in which the RH is introduced, and the R—Fe—B based sintered magnet to which the RH is introduced from the RH diffusion introducing material After the separation, it may be carried out by accommodating it again in the processing chamber or by accommodating it in the processing chamber of another heat treatment furnace.

2: About Step B Step B is a step of performing surface modification of the R—Fe—B based sintered magnet into which RH is diffused and introduced in Step A. According to the process B, the surface of the R—Fe—B sintered magnet into which RH is introduced and diffused can be modified to have a stable and excellent corrosion resistance, and a corrosion resistant coating can be formed with excellent adhesion. It becomes like this. Therefore, even when the R-containing layer having poor stability is formed on the surface of the magnet by the process A, the R-containing layer is modified and stabilized by the process B, so that excellent corrosion resistance is imparted to the magnet. At the same time, a corrosion-resistant film can be formed with excellent adhesion on the surface.

In Step B, the oxygen partial pressure is 1 × 10 ³ Pa to 1 × 10 ⁵ Pa, the water vapor partial pressure is less than 1000 Pa, and the ratio of oxygen partial pressure to water vapor partial pressure (oxygen partial pressure / water vapor partial pressure) is In this process, heat treatment is performed at 200 to 500 ° C. in an atmosphere of 1 to 20000. To define the oxygen partial pressure ^{1 × 10 3 Pa~1 × 10 5} Pa is the oxygen partial pressure is less than 1 × ¹⁰ 3 Pa, that the amount of oxygen in the atmosphere is too low, surface modification of the magnet It takes too much time for quality, or the surface of the part of the magnet in contact with the holding member is not sufficiently modified, so that sufficient corrosion resistance or stability is not given to the part, or the part is This is because contact marks may remain. On the other hand, even if the oxygen partial pressure is made higher than 1 × 10 ⁵ Pa, the effect of surface modification of the magnet by increasing the oxygen partial pressure is not recognized so much, which may only lead to an increase in cost. Because. In order to perform the desired modification on the surface of the magnet more effectively and at low cost, the oxygen partial pressure is preferably 1 × 10 ³ Pa to 5 × 10 ⁴ Pa, and 1 × 10 ⁴ Pa to ³ × 10. ⁴ Pa is more desirable. The water vapor partial pressure is defined as less than 1000 Pa. If the water vapor partial pressure is 1000 Pa or more, the amount of water vapor in the atmosphere is excessive, and the surface of the magnet is modified to a stable one that exhibits excellent corrosion resistance. Because there is a fear that it cannot be done. In order to perform the desired modification on the surface of the magnet more effectively and at low cost, the water vapor partial pressure is desirably 700 Pa or less, and more desirably 45 Pa or less. The lower limit of the water vapor partial pressure is not particularly limited, but is usually 1 Pa. The ratio between the oxygen partial pressure and the water vapor partial pressure is defined as 1 to 20000. If the ratio is smaller than 1, the amount of water vapor with respect to the amount of oxygen in the atmosphere is too large, so that the surface of the magnet has excellent corrosion resistance. This is because there is a possibility that it cannot be reformed to a stable one. On the other hand, an atmosphere in which the ratio is greater than 20000 is a special environment and is not practical. In order to perform the desired modification on the surface of the magnet more effectively and at a low cost, the ratio is preferably 10 to 10,000, more preferably 300 to 5000, and further preferably 450 to 4000. The atmosphere in the processing chamber may be formed, for example, by individually introducing these oxidizing gases so as to have a predetermined partial pressure, or a dew point at which these oxidizing gases are included at a predetermined partial pressure. You may form by introduce | transducing the atmosphere which has. Further, an inert gas such as nitrogen gas or argon gas may coexist in the processing chamber. If the total pressure of the atmosphere is set to atmospheric pressure or a pressure in the vicinity thereof (specifically, for example, 9 × 10 ⁴ Pa to 1.2 × 10 ⁵ Pa), a predetermined atmosphere is not required without requiring special pressure adjusting means. Can be easily formed to improve the surface of the magnet.

  The temperature of the heat treatment in the step B is defined as 200 ° C. to 500 ° C. If the temperature is lower than 200 ° C., it may be difficult to perform a desired modification on the surface of the magnet. If it is too high, the magnetic properties of the magnet may be adversely affected. The temperature of the heat treatment is preferably 240 ° C to 450 ° C, more preferably 300 ° C to 420 ° C. The heat treatment time is preferably 1 minute to 3 hours, more preferably 15 minutes to 2.5 hours. If the time is too short, it may be difficult to perform the desired modification on the surface of the magnet, while if the time is too long, the magnetic properties of the magnet may be adversely affected.

In addition, it is desirable to perform the process of raising the temperature of the magnet from room temperature to the temperature at which heat treatment is performed in an atmosphere having an oxygen partial pressure of 1 × 10 ² Pa to 1 × 10 ⁵ Pa and a water vapor partial pressure of 1 Pa to 100 Pa. By raising the temperature in such an atmosphere, moisture that is naturally adsorbed on the surface of the magnet is desorbed at an early stage, so that the moisture present on the surface of the magnet is It is possible to avoid adverse effects as much as possible. The temperature increase rate may be, for example, 100 ° C./hour to 2000 ° C./hour. In the present invention, “normal temperature” refers to the temperature (for example, room temperature) of the environment in which the R—Fe—B sintered magnet subjected to surface modification is placed at the start of temperature rise, and is illustrative. Means a temperature defined as 5 ° C. to 35 ° C. in JIS Z 8703 of the Japanese Industrial Standard.

Moreover, it is desirable that the step of lowering the temperature of the magnet after the heat treatment is also performed in an atmosphere having an oxygen partial pressure of 1 × 10 ² Pa to 1 × 10 ⁵ Pa and a water vapor partial pressure of 1 Pa to 100 Pa. By lowering the temperature in such an atmosphere, it is possible to prevent a phenomenon that the surface of the magnet is condensed during the process and the magnet is corroded to deteriorate the magnetic characteristics.

  The step of raising the temperature of the magnet from room temperature to the temperature at which heat treatment is performed, the step of heat-treating the magnet, and the step of lowering the temperature of the magnet after heat treatment are sequentially performed in the respective processing chamber environments in which the magnets are accommodated. It may be performed by changing to an environment for performing the process, or may be performed by dividing the processing chamber into regions controlled by the environment for performing each process and sequentially moving the magnets to the respective regions.

  FIG. 2 shows an example of a continuous processing furnace in which the above three steps are divided into regions controlled by the environment for performing each step, and a magnet is sequentially moved to each region. It is a schematic diagram. In the continuous processing furnace shown in FIG. 2, each processing is performed while moving the magnet from the left to the right in the drawing by moving means such as a belt conveyor. Arrows indicate the flow of the atmospheric gas in each region formed by an unillustrated air supply means and exhaust means. The inlet of the temperature rising region and the outlet of the temperature falling region are partitioned by, for example, an air curtain, and the boundary between the temperature rising region and the heat treatment region and the boundary between the heat treatment region and the temperature lowering region are partitioned by, for example, the flow of the atmospheric gas indicated by the arrows (these This may be done mechanically with a shutter). If such a continuous processing furnace is used, surface modification with stable quality can be continuously performed for a large number of magnets.

  In addition, although the process B may be performed after performing the process A, it may be performed after performing the blasting process or the surface grinding process on the R-Fe-B sintered magnet subjected to the process A. Good. As described above, even when the R-containing layer having poor stability is formed on the surface of the magnet by the step A, the R-containing layer is modified and stabilized by the step B, but the R-Fe subjected to the step A is stabilized. -B-type sintered magnets are subjected to blasting or surface grinding to remove part or all of such R-containing layers, and then perform step B to further enhance the surface modification effect of the magnet. Thus, superior corrosion resistance is imparted to the magnet. In particular, the effect is that, as step A, the R—Fe—B sintered magnet and the RH diffusion introducing material to be processed are accommodated in the processing chamber, and both are moved continuously or intermittently in the processing chamber. This is exhibited when a method of performing heat treatment at 500 ° C. to 1000 ° C. is employed. The conditions for blasting and surface grinding are not particularly limited, but for blasting, for example, a non-metallic projection material such as glass beads is applied for 1 second to 1 at a projection pressure of 0.1 MPa to 0.5 MPa. This can be done by projecting time. For surface grinding, for example, a surface grinder or double-head grinder equipped with a grindstone having a grain size of # 60 to # 400 is used, the rotation speed of the grindstone is 600 rpm to 2000 rpm, and the magnet feed speed to the grinder is increased. What is necessary is just to carry out as 0.01 m / min-5 m / min.

Examples of the R—Fe—B based sintered magnet to be treated in the present invention include those manufactured by the following manufacturing method.
An alloy containing 25 to 40 mass% of rare earth element R, 0.6 to 1.6 mass% of B (boron), and the balance Fe and inevitable impurities is prepared. Here, R may include RH. Further, a part of B may be substituted by C (carbon), and a part of Fe (50 mass% or less) may be substituted by another transition metal element (for example, Co or Ni). Good. This alloy is suitable for a variety of purposes, including Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and You may contain about 0.01-1.0 mass% of the at least 1 sort (s) of additional element M selected from the group which consists of Bi.
The above-mentioned alloy can be suitably produced by rapidly cooling a molten raw material alloy by, for example, a strip casting method. Hereinafter, preparation of a rapidly solidified alloy by a strip casting method will be described.
First, a raw material alloy having the above composition is melted by high frequency melting in an argon gas atmosphere to form a molten raw material alloy. Next, after holding this molten metal at about 1350 ° C., it is rapidly cooled by a single roll method to obtain, for example, a flake-shaped alloy ingot having a thickness of about 0.3 mm. The alloy slab thus produced is pulverized into, for example, 1 to 10 mm flakes before the next hydrogen pulverization treatment. In addition, the manufacturing method of the raw material alloy by a strip cast method is disclosed by US Patent 5,383,978 specification, for example.
[Coarse grinding process]
The alloy slab coarsely crushed into flakes is accommodated in the hydrogen furnace. Next, a hydrogen embrittlement treatment process (hereinafter sometimes referred to as “hydrogen pulverization treatment” or simply “hydrogen treatment”) is performed inside the hydrogen furnace. When the coarsely pulverized powder alloy powder after the hydrogen pulverization treatment is taken out from the hydrogen furnace, the takeout operation is preferably performed in an inert atmosphere so that the coarsely pulverized powder does not come into contact with the atmosphere. By doing so, it is possible to prevent the coarsely pulverized powder from oxidizing and generating heat, and to suppress the deterioration of the magnetic properties of the magnet.
By the hydrogen pulverization treatment, the rare earth alloy is pulverized to a size of about 0.1 mm to several mm, and the average particle size becomes 500 μm or less. After the hydrogen pulverization treatment, the embrittled raw material alloy is preferably crushed more finely and cooled. When the raw material is taken out in a relatively high temperature state, the cooling process time may be relatively long.
[Fine grinding process]
Next, the coarsely pulverized powder is finely pulverized using a jet mill pulverizer. A cyclone classifier is connected to the jet mill crusher used in the present embodiment. The jet mill pulverizer is supplied with the rare earth alloy (coarse pulverized powder) coarsely pulverized in the coarse pulverization step, and pulverizes in the pulverizer. The powder pulverized in the pulverizer is collected in a collection tank through a cyclone classifier. In this way, a fine powder of about 0.1 to 20 μm (typically an average particle size of 3 to 5 μm) can be obtained. The pulverizer used for such fine pulverization is not limited to a jet mill, and may be an attritor or a ball mill. In grinding, a lubricant such as zinc stearate may be used as a grinding aid.
[Press molding]
In the present embodiment, for example, 0.3% by mass of a lubricant is added to and mixed with the magnetic powder produced by the above method in a rocking mixer, and the surface of the alloy powder particles is coated with the lubricant. Next, the magnetic powder produced by the above-described method is molded in an orientation magnetic field using a known press machine. The intensity of the applied magnetic field is, for example, 0.8 to 1.4 MA / m. The molding pressure is set so that the green density of the molded body is, for example, about 4 to 4.5 g / cm ³ .
[Sintering process]
It carries out for 10 to 240 minutes with respect to said powder molded object at the temperature within the range of 1000-1200 degreeC, for example. Even if the step of holding at a temperature in the range of 650 to 1000 ° C. for 10 to 240 minutes and the step of further promoting the sintering at a temperature higher than the above holding temperature (for example, 1000 to 1200 ° C.) are sequentially performed. Good. After the sintering process, grinding for dimension adjustment may be performed.

  The R—Fe—B based sintered magnet in which a part of the RL produced by the production method of the present invention is replaced by RH has excellent corrosion resistance, so it can be used as it is incorporated in various motors and home appliances. Alternatively, a further corrosion resistance may be imparted by forming a corrosion-resistant film such as a metal film or a resin film exemplified by an Al film on the surface.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is limited to the following description and is not interpreted.

Example 1:
(R-Fe-B sintered magnet used)
Nd: 20.7, Pr: 5.7, Dy: 5.0, B: 1.00, Co: 0.9, Cu: 0.1, Al: 0.2, balance: Fe (unit: mass%) The alloy flakes having a composition of 0.2 to 0.3 mm in thickness were produced by a strip casting method.
Next, this alloy flake was filled in a container and accommodated in a hydrogen treatment apparatus. Then, the hydrogen treatment apparatus was filled with hydrogen gas at a pressure of 500 kPa, so that hydrogen was occluded in the alloy flakes at room temperature and then released. By performing such a hydrogen treatment, the alloy flakes were embrittled to produce an amorphous powder having a size of about 0.15 to 0.2 mm.
After adding 0.04 mass% zinc stearate as a grinding aid to the amorphous powder produced by the above hydrogen treatment and mixing, a grinding process using a jet mill device is performed to obtain a fine particle having an average particle size of about 3 μm. A powder was prepared.
The fine powder thus produced was molded by a press apparatus to produce a powder compact. Specifically, the powder particles were compressed in a magnetic field-oriented state in an applied magnetic field and pressed. Thereafter, the molded body is extracted from the press apparatus, and a sintered body block is obtained by performing a sintering process at 1050 ° C. for 4 hours in a vacuum furnace, and the obtained sintered body block is subjected to surface grinding to adjust the dimensions. An R—Fe—B sintered magnet having a thickness of 2 mm × length of 15 mm × width of 18 mm was obtained. The R—Fe—B sintered magnet thus obtained was subjected to ultrasonic water washing and then dried and used for experiments (hereinafter referred to as “sintered magnet”).

Step A was performed using the heat treatment apparatus shown in FIG. 1 (the cylindrical container is made of SUS having a diameter of 50 mm and a length of 70 mm, and the internal volume is 137375 mm ³ ). Specifically, in the container, 50 g of sintered magnet, 50 g of RH diffusion introducing material (spherical body having a diameter of 3 mm or less made of an alloy of 60 mass% Dy and 40 mass% Fe), a stirring auxiliary material (diameter 5 mm made of zirconia) Spheroids) are sequentially accommodated, the inside of the container is an argon gas atmosphere with a pressure of 100 Pa, the temperature in the container is 900 ° C., and the container is rotated around the central axis at a peripheral speed of 0.02 m / sec. The contents are made passive in the container, and heat treatment is performed for 6 hours while moving the contents continuously or intermittently so that the contents can be moved relatively close to or in contact, and Dy is diffused and introduced into the sintered magnet. Step A was performed (the method of Step A is abbreviated as “contact diffusion method”). The heat treatment environment is such that after the contents are stored in the container, the container is evacuated and heated up to 600 ° C. at 10 ° C./min in a vacuum, and then the pressure in the container becomes 100 Pa. After the argon gas was introduced into the container, rotation of the container was started and the temperature was increased at 10 ° C./min until the temperature in the container reached 900 ° C. After completion of the heat treatment, the inside of the container was naturally allowed to cool to room temperature, then the contents were taken out and the sintered magnet was separated from the RH diffusion introducing material and the stirring auxiliary material. Thereafter, the sintered magnet was housed in another heat treatment furnace, the pressure inside the furnace was set to 100 Pa, the first heat treatment at 900 ° C. was performed for 6 hours, and then the second heat treatment at 500 ° C. was performed for 3 hours.

  Step B was performed using the continuous processing furnace shown in FIG. 2 with respect to the sintered magnet which performed the process A, 1st heat processing, and 2nd heat processing. Specifically, surface modification is performed by performing a heat treatment at 400 ° C. for 30 minutes in an atmosphere having a dew point of −35 ° C. (oxygen partial pressure 20000 Pa, water vapor partial pressure 32 Pa, oxygen partial pressure / water vapor partial pressure = 625). A sintered magnet was obtained. Note that the temperature was raised from room temperature (25 ° C.) to the heat treatment temperature (400 ° C.) in an air atmosphere having a dew point of −35 ° C. at a rate of 500 ° C./hour. After completion of the heat treatment, it was naturally cooled to room temperature in an air atmosphere with a dew point of -35 ° C.

Example 2:
A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that the sintered magnet was blasted between the second heat treatment of Example 1 and Step B. The blasting of the sintered magnet is performed using a blasting device (SGF-4B) manufactured by Fuji Seisakusho, using glass beads (GB # 100) manufactured by Kyoei Abrasive Co., Ltd. as a projecting material, and a projecting pressure of 0.3 MPa. Then, each surface was projected for 15 seconds. The sintered magnet subjected to blasting was subjected to ultrasonic water washing and then dried and subjected to experiments.

Example 3:
A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that surface grinding was performed on the sintered magnet between the second heat treatment of Example 1 and Step B. The surface grinding for the sintered magnet was performed by grinding each surface by 0.2 mm using a surface grinder manufactured by Daisho Seiki Co., Ltd. (grinding wheel count: # 100, grinding wheel rotation speed: 1500 rpm, feeding speed of magnet to grinding machine: 0.6 m / min). The sintered magnet subjected to surface grinding was subjected to ultrasonic water washing and then dried to be used for experiments.

Example 4:
Instead of the atmosphere with a dew point of −35 ° C. used in Step B of Example 1, an atmosphere with a dew point of 0 ° C. (oxygen partial pressure 20000 Pa, water vapor partial pressure 600 Pa, oxygen partial pressure / water vapor partial pressure = 33.3) was used. A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that heat treatment was performed.

Example 5:
A surface-modified sintered magnet was obtained in the same manner as in Example 4 except that the sintered magnet was blasted between the second heat treatment of Example 4 and Step B. The blasting of the sintered magnet is performed using a blasting device (SGF-4B) manufactured by Fuji Seisakusho, using glass beads (GB # 100) manufactured by Kyoei Abrasive Co., Ltd. as a projecting material, and a projecting pressure of 0.3 MPa. Then, each surface was projected for 15 seconds. The sintered magnet subjected to blasting was subjected to ultrasonic water washing and then dried and subjected to experiments.

Example 6:
A surface-modified sintered magnet was obtained in the same manner as in Example 4 except that surface grinding was performed on the sintered magnet between the second heat treatment of Example 4 and Step B. The surface grinding for the sintered magnet was performed by grinding each surface by 0.2 mm using a surface grinder manufactured by Daisho Seiki Co., Ltd. (grinding wheel count: # 100, grinding wheel rotation speed: 1500 rpm, feeding speed of magnet to grinding machine: 0.6 m / min). The sintered magnet subjected to surface grinding was subjected to ultrasonic water washing and then dried to be used for experiments.

Example 7:
Instead of the RH diffusion introducing material used in Step A of Example 1, a spherical body made of an alloy of 55 mass% Dy and 45 mass% Fe having a diameter of 3 mm or less was used as the RH diffusion introducing material, and the pressure in the container was reduced to 0. The surface-modified sintered magnet was obtained in the same manner as in Example 1 except that the temperature in the container was 870 ° C. and heat treatment was performed.

Example 8:
Instead of the RH diffusion introducing material used in Step A of Example 1, a spherical body having a diameter of 3 mm or less made of an alloy of 40 mass% Dy and 60 mass% Fe was used as the RH diffusion introducing material, and no stirring auxiliary material was used. The surface-modified sintered magnet was obtained in the same manner as in Example 1 except that the pressure in the container was 2 Pa, the temperature in the container was 950 ° C., and heat treatment was performed for 3 hours.

Example 9:
Instead of the RH diffusion introducing material used in step A of Example 1, a spherical body having a diameter of 3 mm or less made of 99.9 mass% Dy was used as the RH diffusion introducing material, the pressure in the container was 500 Pa, A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that the temperature was 800 ° C. and heat treatment was performed for 6 hours.

Example 10:
Instead of the RH diffusion introducing material used in Step A of Example 2, a spherical body having a diameter of 3 mm or less made of 99.9 mass% Dy was used as the RH diffusion introducing material, the pressure in the container was set to 0.05 Pa, and the container A surface-modified sintered magnet was obtained in the same manner as in Example 2 except that the inner temperature was 800 ° C. and heat treatment was performed for 6 hours.

Example 11:
(R-Fe-B sintered magnet used)
Nd: 20.7, Pr: 5.7, Dy: 5.0, B: 1.00, Co: 0.9, Cu: 0.1, Al: 0.2, balance: Fe (unit: mass%) The alloy flakes having a composition of 0.2 to 0.3 mm in thickness were produced by a strip casting method.
Next, this alloy flake was filled in a container and accommodated in a hydrogen treatment apparatus. Then, the hydrogen treatment apparatus was filled with hydrogen gas at a pressure of 500 kPa, so that hydrogen was occluded in the alloy flakes at room temperature and then released. By performing such a hydrogen treatment, the alloy flakes were embrittled to produce an amorphous powder having a size of about 0.15 to 0.2 mm.
After adding 0.04 mass% zinc stearate as a grinding aid to the amorphous powder produced by the above hydrogen treatment and mixing, a grinding process using a jet mill device is performed to obtain a fine particle having an average particle size of about 3 μm. A powder was prepared.
The fine powder thus produced was molded by a press apparatus to produce a powder compact. Specifically, the powder particles were compressed in a magnetic field-oriented state in an applied magnetic field and pressed. Thereafter, the molded body is extracted from the press device, and subjected to a sintering process at 1050 ° C. for 4 hours in a vacuum furnace to obtain a sintered body having a thickness of 2 mm × length 15 mm × width 18 mm, and the size of the sintered body thus obtained is adjusted. The R-Fe-B sintered magnet was used for the experiment without performing surface grinding for the purpose (hereinafter referred to as "sintered magnet").

  The same treatment as in Example 1 was performed to obtain a surface-modified sintered magnet.

Example 12:
Step A was performed according to the method described in Patent Document 1. Specifically, in a Mo processing vessel, from 99.9 mass% Dy as an RH bulk body for each of the front and back surfaces of a sintered magnet (same as the sintered magnet used in Example 1). A plate-like block having a thickness of 5 mm × length of 30 mm × width of 30 mm is arranged facing each other with an interval of 5 mm to 9 mm, the pressure in the container is 0.01 Pa, the temperature in the container is 900 ° C., and heat treatment is performed for 6 hours. By performing, the process A for carrying out the diffusion introduction of Dy with respect to the sintered magnet was performed (the method of this process A is abbreviated as "spaced diffusion method"). After the heat treatment was completed, the inside of the container was naturally allowed to cool to room temperature, and after removing the RH bulk body from the inside of the container, the first heat treatment and the second heat treatment were performed in the same manner as in Example 1.

  The same process B as Example 1 was performed with respect to the sintered magnet which performed the process A, 1st heat processing, and 2nd heat processing, and the surface-modified sintered magnet was obtained.

Example 13:
A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that the sintered magnet was blasted between the second heat treatment of Example 12 and Step B. The blasting of the sintered magnet is performed using a blasting device (SGF-4B) manufactured by Fuji Seisakusho, using glass beads (GB # 100) manufactured by Kyoei Abrasive Co., Ltd. as a projecting material, and a projecting pressure of 0.3 MPa. Then, each surface was projected for 15 seconds. The sintered magnet subjected to blasting was subjected to ultrasonic water washing and then dried and subjected to experiments.

Example 14:
As step A, a Dy film having a thickness of about 5 μm is formed on the surface of a sintered magnet (same as the sintered magnet used in Example 1) using a target composed of 99.9 mass% Dy by an electron beam heating vapor deposition method. Then, heat treatment was performed at 900 ° C. for 2 hours in a vacuum heat treatment furnace, and Dy was diffused and introduced into the sintered magnet. After the heat treatment was completed, an additional heat treatment was subsequently performed under the same conditions as the second heat treatment of Example 1.

  The same process B as Example 1 was performed with respect to the sintered magnet which performed the additional heat processing with the process A, and the surface-modified sintered magnet was obtained.

Example 15:
Instead of the air having a dew point of −35 ° C. used in Step B of Example 1, an air having a dew point of −10 ° C. (oxygen partial pressure 20000 Pa, water vapor partial pressure 290 Pa, oxygen partial pressure / water vapor partial pressure = 69.0) is used. A surface-modified sintered magnet was obtained in the same manner as in Example 1 except that heat treatment was performed at 300 ° C. for 2 hours.

Example 16:
In place of the atmosphere having a dew point of −35 ° C. used in Step B of Example 2, an atmosphere having a dew point of −51 ° C. (oxygen partial pressure 20000 Pa, water vapor partial pressure 5.8 Pa, oxygen partial pressure / water vapor partial pressure = 3448.3) A surface-modified sintered magnet was obtained in the same manner as in Example 2 except that heat treatment was performed at 340 ° C. for 1.5 hours.

Example 17:
Instead of the atmosphere with a dew point of −35 ° C. used in Step B of Example 3, an atmosphere with a dew point of −28 ° C. (oxygen partial pressure 20000 Pa, water vapor partial pressure 60 Pa, oxygen partial pressure / water vapor partial pressure = 333.3) was used. A surface-modified sintered magnet was obtained in the same manner as in Example 3 except that heat treatment was performed at 420 ° C. for 20 minutes.

Example 18:
The surface-modified sintered magnet obtained in Example 1 is accommodated in a quantity of 1.5 kg in each cylindrical barrel of the vapor deposition coating film forming apparatus described in JP-A-2001-335921 . After evacuating to 10 ⁻¹ Pa, argon gas was supplied so that the total pressure in the vacuum chamber was 1.0 Pa. Thereafter, glow discharge was performed for 15 minutes under the condition of a bias voltage of 0.5 kV while rotating the rotating shaft of the barrel at 6.0 rpm to clean the surface of the magnet specimen. Subsequently, under the conditions of an argon gas pressure of 1.0 Pa and a bias voltage of 1.0 kV, an Al wire having a hydrogen content of 5 ppm as a vapor deposition material (compliant with JIS A1070) is continuously supplied at a wire feed rate of 3.3 g / min. Then, this was heated and evaporated (Haas temperature: 1400 ° C.), vapor deposition was performed for 30 minutes, and an Al film was deposited on the surface of the sintered magnet. The sintered magnet having the Al coating obtained on the surface as described above is put into a blasting apparatus, and together with a pressurized gas composed of nitrogen gas, spherical glass beads having an average particle size of 120 μm and a Mohs hardness of 6 as a projection material The powder was sprayed for 10 minutes at a spraying pressure of 0.2 MPa, and shot peening was performed on the Al coating to obtain a sintered magnet having an Al coating with a thickness of about 6 μm on the surface.

Comparative Example 1:
The sintered magnet obtained by carrying out similarly to Example 1 except not performing the process B of Example 1. FIG.

Comparative Example 2:
The sintered magnet obtained by carrying out similarly to Example 2 except not performing the process B of Example 2. FIG.

Comparative Example 3:
The sintered magnet obtained by carrying out similarly to Example 3 except not performing the process B of Example 3. FIG.

Comparative Example 4:
The sintered magnet obtained by carrying out similarly to Example 12 except not performing the process B of Example 12. FIG.

Comparative Example 5:
The sintered magnet obtained by carrying out similarly to Example 13 except not performing the process B of Example 13. FIG.

Comparative Example 6:
A sintered magnet having a chemical conversion treatment film on the surface obtained in the same manner as in Example 3 except that chemical conversion treatment is performed instead of step B in Example 3. The chemical conversion treatment was performed by adding a sintered magnet to a treatment solution (pH 3.0) having a phosphoric acid concentration of 0.07 mol / L prepared by adding an 85 mass% phosphoric acid aqueous solution to pure water at a bath temperature of 60 ° C. After dipping for 1 minute, the treatment liquid was pulled up, washed with water, and dried at 160 ° C. for 35 minutes.

Comparative Example 7:
(R-Fe-B sintered magnet used)
Nd: 20.7, Pr: 5.7, Dy: 5.0, B: 1.00, Co: 0.9, Cu: 0.1, Al: 0.2, balance: Fe (unit: mass%) The alloy flakes having a composition of 0.2 to 0.3 mm in thickness were produced by a strip casting method.
Next, this alloy flake was filled in a container and accommodated in a hydrogen treatment apparatus. Then, the hydrogen treatment apparatus was filled with hydrogen gas at a pressure of 500 kPa, so that hydrogen was occluded in the alloy flakes at room temperature and then released. By performing such a hydrogen treatment, the alloy flakes were embrittled to produce an amorphous powder having a size of about 0.15 to 0.2 mm.
After adding 0.04 mass% zinc stearate as a grinding aid to the amorphous powder produced by the above hydrogen treatment and mixing, a grinding process using a jet mill device is performed to obtain a fine particle having an average particle size of about 3 μm. A powder was prepared.
The fine powder thus produced was molded by a press apparatus to produce a powder compact. Specifically, the powder particles were compressed in a magnetic field-oriented state in an applied magnetic field and pressed. Thereafter, the formed body is extracted from the press device, and a sintered body block is obtained by performing a sintering process at 1050 ° C. for 4 hours in a vacuum furnace. The obtained sintered body block is subjected to a pressure of 100 Pa at 500 ° C. After aging treatment for 3 hours, surface grinding was performed to adjust the dimensions, thereby obtaining an R—Fe—B rare earth sintered magnet having a thickness of 2 mm × length 15 mm × width 18 mm. The R—Fe—B sintered magnet thus obtained was subjected to ultrasonic water washing and then dried and used for experiments (hereinafter referred to as “sintered magnet”).

  The sintered magnet was subjected to the same treatment as in Step B of Example 1 to obtain a surface-modified sintered magnet.

Comparative Example 8:
The sintered magnet (same as the sintered magnet used in Example 1) was subjected to the same treatment as the second heat treatment and surface grinding in Example 3, and then subjected to chemical conversion treatment on the surface obtained. A sintered magnet having a chemical conversion coating. The chemical conversion treatment was performed in the same manner as in Comparative Example 6.

Comparative Example 9:
The sintered magnet which performed only the process similar to the surface grinding process of Example 3 with respect to the sintered magnet (the same thing as the sintered magnet used in Example 1).

Comparative Example 10:
A sintered magnet having an Al coating on the surface obtained in the same manner as in Example 18 except that the Al coating is formed without performing Step B of Example 1.

(Corrosion resistance evaluation test)
The surface-modified sintered magnet obtained in Example 1 to Example 17 was subjected to a constant temperature and humidity test at 80 ° C. × 90% RH for 100 hours, and the weight fluctuation of the magnet before the test was measured. The corrosion resistance of the magnet was evaluated by the degree of weight increase due to oxidative corrosion of the surface of the magnet. The results are shown in Table 1. Further, the same constant temperature and humidity test was performed on the various sintered magnets obtained in Comparative Examples 1 to 9, and the corrosion resistance of the magnets was evaluated. The results are shown in Table 2.

  From Table 1 and Table 2, the following became clear. Since the magnets of Examples 1 to 3 are subjected to Step B after performing Step A, the magnets after the constant temperature and humidity test are compared with the magnets of Comparative Examples 1 to 3 that are not performing Step B. The degree of increase in weight was extremely slight, and it was found that the magnet had corrosion resistance with no practical problems even if it was used as it was. As a result, the surface of the magnet was modified by performing Step B, and the progress of oxidative corrosion of the R-containing layer having poor stability formed on the surface of the magnet accompanying Step A was suppressed. It was thought that. Since the same results were obtained in the comparisons between the magnets of Examples 12 and 13 and the magnets of Comparative Examples 4 and 5, the surface modification effect of the magnet by Step B can be obtained regardless of the type of Step A. all right. From the comparison of the magnet of Example 1, the magnet of Example 2, and the magnet of Example 3, the surface modification effect of the magnet by the process B is enhanced by performing blasting or surface grinding before performing the process B. I understood. The magnet of Comparative Example 6 in which surface grinding and chemical conversion were performed after Step A, the magnet of Comparative Example 7 in which surface grinding and Step B were performed without performing Step A, and surface grinding without performing Step A The magnet of Comparative Example 8 that has undergone processing and chemical conversion treatment, and the magnet of Comparative Example 9 that has undergone only surface grinding without performing Step A or Step B are compared in terms of the degree of weight increase of the magnet after the constant temperature and humidity test. Compared with the degree of increase in the weight of the magnet after the constant temperature and humidity test in the magnets of Examples 3, 6, and 17 in which the surface grinding process and the process B were performed after performing the process A, the degree is It was a big one. From the comparison of the magnet of Example 1, the magnet of Example 12, and the magnet of Example 14, the surface modification effect of the magnet by Step B is the case where the separation diffusion method described in Patent Document 1 is adopted as Step A. It can be obtained even if the method of diffusion introduction of RH is adopted by heat treatment after forming the RH film on the surface of the magnet by known EB vapor deposition, but the degree is the case when the contact diffusion method is adopted as step A Was found to be excellent. From the comparison of the magnets of Examples 1, 4, 7, and 8 and the magnet of Example 9, when the contact diffusion method is adopted as Step A, the RH diffusion introducing material does not include the one containing Fe in addition to RH. It was found that the surface modification effect by the process B was superior to that of the process B. From the comparison of the magnets of Examples 1 to 3 and the magnets of Examples 4 to 6, it was found that the water vapor partial pressure forming the atmosphere in which the process B is performed should be lower.

(Adhesion evaluation test)
A cross-cut test based on JIS-K5600-5-6 was performed on each sintered magnet having an Al coating on the surface obtained in Example 18 and Comparative Example 10, and the adhesion of the Al coating was evaluated. As a result, no film peeling was observed for the Al coating of Example 18, but film peeling was observed at 31 of 36 squares for the Al coating of Comparative Example 10. From the above results, it was found that the Al film can be formed with excellent adhesion on the surface of the magnet due to the surface modification effect of the magnet in Step B of Example 1.

(Dy diffusion introduction effect on R-Fe-B sintered magnet)
The surface-modified sintered magnets obtained in Examples 1 to 17 showed an improvement in coercive force of about 250 kA / m to 350 kA / m as compared with the sintered magnets before processing. . However, a decrease in residual magnetic flux density, which is a practical problem, was not recognized.

  The present invention has an excellent corrosion resistance and can form a corrosion-resistant film such as a metal film or a resin film on the surface with excellent adhesion, and a part of RL is substituted by RH. The present invention has industrial applicability in that it can provide a method for producing a sintered magnet.

DESCRIPTION OF SYMBOLS 1 R-Fe-B system sintered magnet 2 RH diffusion introduction material 3 Cylindrical container 4 Heater 5 Lid 6 Exhaust device 7 Motor

Claims (7)

A method for producing an R—Fe—B based sintered magnet in which a part of a light rare earth element (RL) is replaced by a heavy rare earth element (RH), which is an R—Fe—B based sintered magnet to be processed Then, after performing Step A in which RH is diffused and introduced from the outside, the oxygen partial pressure is 1 × 10 ³ Pa to 1 × 10 ⁵ Pa, the water vapor partial pressure is less than 1000 Pa, and the oxygen partial pressure and the water vapor content A production method comprising performing Step B of performing heat treatment at 200 ° C. to 500 ° C. in an atmosphere having a pressure ratio (oxygen partial pressure / water vapor partial pressure) of 450 to 20000.   An R—Fe—B sintered magnet and an RH diffusion introducing material for introducing diffusion of RH from the outside are accommodated in the processing chamber so as to be relatively movable and close to or in contact with each other. The method according to claim 1, wherein the step A is performed by performing a heat treatment at 500 ° C. to 1000 ° C. while intermittently moving.   3. The method according to claim 2, wherein an RH diffusion introducing material made of an alloy containing Fe in addition to RH is used.   The manufacturing method according to claim 3, wherein the Fe content of the alloy is 30 mass% to 80 mass%. The process according to any one of claims 1 to 4 the partial pressure of water vapor step B characterized by the following and to Rukoto 45 Pa.   6. The process B is performed after the blasting and / or surface grinding is performed on the R-Fe-B sintered magnet after the process A is performed. The manufacturing method as described.   An R—Fe—B based sintered magnet obtained by the manufacturing method according to claim 1, wherein a part of RL is replaced by RH.