JP2011216674A - Method of manufacturing rare-earth-based permanent magnet having vapor-deposited film of aluminum or alloy thereof on surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a rare-earth-based permanent magnet with a vapor-deposited film of aluminum or its alloy formed on a surface thereof with excellent adhesiveness.SOLUTION: When the vapor-deposited film of aluminum or its alloy is formed on the surface of the rare-earth-based permanent magnet by effecting evaporation while continuously supplying a wired vapor-deposition material of aluminum or its alloy to a melt evaporating part heated by a resistance heating system in a vapor deposition vessel, a vapor-depositing process is performed by controlling a temperature rise slope of a magnet from start to end of the vapor-depositing process to not more than 10 °C/min.

Description

  The present invention relates to a method for producing a rare earth permanent magnet having a deposited film of aluminum or an alloy thereof (for example, an alloy containing 1 to 10% by mass of magnesium as a metal other than aluminum) on the surface. More specifically, the present invention relates to a method for producing a rare earth-based permanent magnet in which a deposited film of aluminum or an alloy thereof is formed on the surface with excellent adhesion.

Rare-earth permanent magnets such as R-Fe-B permanent magnets typified by Nd-Fe-B permanent magnets are made of resource-rich and inexpensive materials and have high magnetic properties. Therefore, in particular, R—Fe—B permanent magnets are used in various fields today. However, since rare earth permanent magnets contain a highly reactive rare earth element: R, they are easily oxidatively corroded in the atmosphere. When used without any surface treatment, a slight amount of acid, alkali, moisture, etc. Corrosion proceeds from the surface due to the presence of rust, and rust is generated, resulting in deterioration and variation in magnetic properties. Furthermore, when a magnet in which rust is generated is incorporated in an apparatus such as a magnetic circuit, the rust may be scattered to contaminate peripheral components.
In view of the above points, for the purpose of imparting excellent corrosion resistance to a rare earth-based permanent magnet, a metal film such as an aluminum film is formed on the surface thereof by a vapor deposition method such as an evaporation method. Yes. In addition to being excellent in corrosion resistance, the aluminum coating has excellent adhesion reliability with the adhesive required when assembling the parts (the coating and adhesive are required to reach the breaking strength inherent in the adhesive). Is widely applied to rare earth permanent magnets that require strong adhesive strength, and rare earth permanent magnets having an aluminum coating on the surface are used in various motors. Yes.

  In order to exhibit strong adhesive strength with parts that incorporate all of the mass-produced rare earth-based permanent magnets, assuming a rare earth-based permanent magnet with an aluminum vapor-deposited coating on the surface, aluminum is applied to the magnet surface. Techniques such as preventing the formation of protrusions that cause poor adhesion with components incorporating magnets and ensuring excellent adhesion between the magnet and the aluminum coating when the coating is deposited. There is a need to address the challenges. For example, in Patent Document 1, the Vickers hardness of the aluminum coating formed on the surface of the magnet is maintained at 25 or more with respect to the technical problem that no protrusion is generated when the aluminum coating is deposited on the surface of the magnet. There has been proposed a method for suppressing softening of a film by performing a vapor deposition process. This method prevents the coating piece from being easily damaged by the softening of the coating, thereby preventing the coating piece from peeling off from the coating, and the coating piece that has been peeled off from the coating is formed on the surface of the magnet. In order to prevent the formation of protrusions due to adhesion, the temperature of the magnet is kept below 2/3 of 660 ° C., which is the melting point of aluminum, that is, 440 ° C. or less, and the aluminum film is deposited. The purpose can be achieved by forming. However, although the technical problem of ensuring excellent adhesion between the magnet and the aluminum coating is well recognized by those skilled in the art, an effective solution has not yet been established. is there.

Japanese Patent No. 2002-88468

  Accordingly, an object of the present invention is to provide a method for producing a rare earth permanent magnet in which a vapor deposited film of aluminum or an alloy thereof is formed on the surface with excellent adhesion.

  As a result of intensive studies in view of the above points, the present inventors have found that the degree of the temperature rise gradient of the magnet when the aluminum film is deposited on the surface of the rare earth permanent magnet is deposited on the surface of the magnet. It has been found that the aluminum coating can be deposited on the surface of the magnet with excellent adhesion by appropriately controlling the temperature rise gradient of the magnet. .

The method for producing a rare earth permanent magnet having a vapor deposition film of aluminum or an alloy thereof on the surface of the present invention based on the above knowledge is as follows. When vapor deposition of aluminum or its alloy is formed on the surface of rare earth permanent magnet by evaporating while continuously supplying wire-like aluminum or its alloy vapor deposition material to the evaporation section, the vapor deposition treatment starts and ends The deposition process is performed by controlling the temperature rise gradient of the magnet until 10 ° C./min.
The manufacturing method according to claim 2 is characterized in that, in the manufacturing method according to claim 1, the temperature rise gradient is controlled by controlling the radiant heat from the melt evaporation section.
Further, in the manufacturing method according to claim 3, in the manufacturing method according to claim 2, the radiant heat from the melting and evaporating part is controlled so that the molten aluminum or the alloy thereof melts in the red light emitting part on the upper surface as a melting evaporating part. It is characterized by using a boat that evaporates and controlling the ratio of the wet-spread area of molten aluminum or its alloy to the red-light emission area of the boat.
The manufacturing method according to claim 4 is characterized in that, in the manufacturing method according to claim 3, the wet spread area of the molten aluminum or its alloy is set to 60% or more of the red heat emission area of the boat.
The manufacturing method according to claim 5 is characterized in that, in the manufacturing method according to claim 3 or 4, the wet spread area of the molten aluminum or its alloy is 90% or less of the red heat emission area of the boat.
The manufacturing method according to claim 6 is characterized in that, in the manufacturing method according to any one of claims 1 to 5, the maximum reached temperature of the rare earth-based permanent magnet is suppressed to 250 ° C. or lower.
The manufacturing method according to claim 7 is characterized in that in the manufacturing method according to any one of claims 1 to 6, the vapor deposition treatment time is set to 10 minutes to 30 minutes.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rare earth-type permanent magnet in which the vapor deposition film of aluminum or its alloy is formed in the surface with the outstanding adhesiveness can be provided.

1 is a schematic front view (partially perspective view) in a vapor deposition tank of an embodiment of a vapor deposition film forming apparatus suitable for carrying out a method of manufacturing a rare earth permanent magnet having a vapor deposition film of aluminum or an alloy thereof on the surface of the present invention. ). It is the evaluation result of the adhesiveness between the magnet body test piece and the aluminum film vapor-deposited and formed on the surface in Experiment A of an Example. It is a measurement result of the arithmetic mean roughness of the aluminum vapor deposition coating formed by vapor deposition on the surface of the magnet body test piece. It is a measurement result of the maximum height roughness of the aluminum vapor deposition coating formed by vapor deposition on the surface of the magnet body test piece.

  The method for producing a rare earth-based permanent magnet having a vapor deposition film of aluminum or an alloy thereof on the surface of the present invention is a method in which wire-like aluminum or an alloy vapor deposition material is continuously applied to a molten evaporation portion heated by a resistance heating method in a vapor deposition tank. When forming a vapor deposition film of aluminum or an alloy thereof on the surface of the rare earth-based permanent magnet by evaporating while supplying, the temperature rise gradient of the magnet from the start to the end of the vapor deposition process is 10 ° C./min. The vapor deposition process is performed under the following control. According to the present invention, a vapor deposition film of aluminum or an alloy thereof can be formed on the surface of a rare earth permanent magnet with excellent adhesion.

  In the present invention, the temperature rise gradient of the magnet from the start to the end of the vapor deposition process means that a vapor deposition film of aluminum or an alloy thereof is formed on the surface of the magnet that is the object to be processed contained in the vapor deposition tank. To increase the temperature of the magnet with respect to the time (deposition processing time) from the start to the end of continuous supply of the vapor-deposited material of wire-like aluminum or its alloy to the melt evaporation part heated by the resistance heating method Means.

  The method for controlling the temperature rise gradient of the rare earth-based permanent magnet within the vapor deposition processing time may be performed by any method. For example, it may be performed by controlling the radiant heat from the melt evaporation part heated by the resistance heating method. It is desirable in terms of simplicity. Control of radiant heat from the melt evaporation part is a boat (metal evaporation heating element) in which wire-like aluminum or its alloy vapor deposition material is continuously supplied to the red-light emitting part on the upper surface, and the vapor deposition material is melted there, spreads and evaporates. ) As a melting and evaporating part, and the ratio of the wet spread area of the molten aluminum or its alloy to the red-light emission area of the boat can be controlled. Thus, when controlling the radiant heat from a fusion | melting evaporation part, it is desirable for the wet spreading area of the molten aluminum or its alloy to be 60% or more of the red-light emission area of a boat. If it is less than 60%, a large amount of radiant heat is released from the red-light-emitting portion where the melted vapor deposition material is not spread, so that it becomes difficult to control the temperature rise gradient of the magnet to 10 ° C./min or less. Alternatively, the deposited film of the alloy may not be formed on the surface of the rare earth permanent magnet with excellent adhesion. In addition, when controlling the radiant heat from the melt evaporation part by controlling the ratio of the wet spread area of molten aluminum or its alloy to the red light emission area of the boat, the upper limit of the wet spread area is the red heat emission area of the boat. 90% or less is desirable. If it exceeds 90%, the molten aluminum or its alloy comes into contact with the electrode disposed on the peripheral edge of the boat, and a splash phenomenon of the molten aluminum or its alloy may occur, or the electrode may be deteriorated or defective at an early stage. There is a fear.

Control of the ratio of the wet spread area of the molten aluminum or its alloy to the red heat emission area of the boat is, for example, the thickness of the aluminum wire or aluminum alloy wire used as the vapor deposition material (for example, a diameter of 1 to 2 mm is desirable) The wire supply rate (for example, 1 g / min to 10 g / min is desirable), the shape and material of the boat, the heating temperature (adjustment by applied current), and the like can be controlled. Boats for wetting and evaporating molten aluminum or its alloys onto the red-light emitting part of the upper surface may be known (see eg WO 2005/049881), for example titanium diboride. And ceramic sintered bodies containing zirconium diboride and boron nitride (titanium nitride and silicon carbide may be included as a conductive material, and aluminum nitride and silicon nitride are included as an insulating material). Also good). The shape is not particularly limited. For example, it is a rectangular parallelepiped of length: 100 mm to 200 mm × width: 20 mm to 40 mm × thickness: 7 mm to 12 mm, and a cavity may be provided on the upper surface, or it has melted Surface treatment for the purpose of improving the wet spreading property of aluminum or an alloy thereof may be performed. As a method of supporting and energizing, an end clamp method known per se (a mode in which the boat is supported and energized by the longitudinal end surface and the lower surface of the boat) and a side clamp method (a mode in which the current is supported and energized by the lateral end surface and the lower surface of the boat) For example, the red light emission area of a boat is usually 75% to 90% of the upper surface area in the former case, and 65% to 80% in the latter case. The number of boats installed in the vapor deposition tank is not particularly limited. The red heat emission area of the boat in the vapor deposition tank may be set to 0.50 × 10 ⁻² m ^{2 to} 0.95 × 10 ⁻² m ² per 1 m ^{3 of the} vapor deposition tank internal volume, for example.

  The temperature rise gradient of the magnet from the start to the end of the vapor deposition process is 8 ° C./min or more in order to efficiently and uniformly form a vapor deposited film of aluminum or its alloy on the surface of the magnet. It is desirable that

  It is desirable to suppress the maximum temperature of the rare earth permanent magnet during the vapor deposition process to 250 ° C. or lower. When the magnet reaches a high temperature exceeding 250 ° C. during the vapor deposition process, when it is cooled to room temperature after that, the thermal strain based on the difference in thermal expansion coefficient between the magnet and the vapor deposited film of aluminum or its alloy formed on the surface of the magnet. Due to this, there is a risk that the adhesion between the two may be reduced. In order to prevent the magnet from reaching a high temperature exceeding 250 ° C. during the vapor deposition process, it is desirable that the vapor deposition process time is short, and specifically, it is desirable to be within 30 minutes. In addition, since the shortening of the vapor deposition processing time depends on the performance of the vapor deposition film forming apparatus, etc., the vapor deposition processing time is currently required for at least 10 minutes.

  The vapor deposition material of wire-like aluminum or an alloy thereof preferably contains carbon monoxide, hydrogen, or the like, which is a reducing gas having reactivity with oxygen, as a deposition control gas. For example, a wire-like aluminum or hydrogen alloy vapor containing 0.5 ppm to 11 ppm of hydrogen is used as the vapor deposition control gas, and at least in the vicinity of the melt evaporation portion in the vapor deposition tank and the rare earth permanent magnet that is the object to be treated. By forming a vapor deposition film of aluminum or an alloy thereof on the surface of the magnet in a state where is supplied, oxidation of the molten vapor deposition material, the evaporated vapor deposition material, or the vapor deposition film formed on the surface of the magnet can be prevented.

  A method for producing a rare earth-based permanent magnet having a vapor deposition film of aluminum or an alloy thereof on the surface of the present invention is described in, for example, JP-A-2001-335921. A vapor deposition film forming apparatus having a cylindrical barrel formed of a mesh for accommodating an object to be vapor-deposited on its surface, and a support member that is rotatable about a horizontal rotation axis The cylindrical barrel is supported so as to revolve outwardly in the circumferential direction of the rotation axis, and by rotating the support member, between the cylindrical barrel that revolves around the rotation axis of the support member and the evaporation portion While making the distance variable, it is possible to form a vapor deposition film on the surface of the workpiece by evaporating the wire vapor deposition material while continuously supplying it to the melt evaporation section heated by the resistance heating method. It can be easily implemented by using a vapor deposited film forming apparatus that.

  FIG. 1 is a schematic front view (partially perspective view) inside a vapor deposition tank of one embodiment of the vapor deposition film forming apparatus described in JP-A-2001-335921. Two support members 7 that are rotatable around a rotation shaft 6 on a horizontal rotation axis are provided above the inside of the vapor deposition tank 1 connected to a vacuum exhaust system (not shown). A cylindrical barrel 5 formed of six stainless steel mesh wire nets is supported in an annular manner by a support shaft 8 so as to revolve on the outer side in the circumferential direction of the rotary shaft 6. A plurality of boats 2, which are melting and evaporating portions for evaporating the vapor deposition material, are arranged on a boat support base 4 standing on a support table 3 below the inside of the vapor deposition tank 1. Inside the support table 3, a wire 9 made of vapor deposition material is wound and held on a supply reel 10. The tip of the wire 9 of vapor deposition material is guided above the boat 2 by a heat-resistant protective tube 11 facing the inner surface of the boat 2. A cutout window 12 is provided in a part of the protective tube 11, and a feeding gear 13 provided corresponding to the cutout window 12 is in direct contact with the vapor deposition material wire 9, so that the vapor deposition material wire 9 is connected. By being drawn out, the vapor deposition material is constantly supplied into the boat 2, and the film formation rate of the vapor deposition film can be freely controlled by adjusting the feed rate of the wire 9 of the vapor deposition material. When the support member 7 is rotated around the rotation shaft 6 (see the arrow in FIG. 1), the cylindrical barrel 5 supported by the support shaft 8 on the outer side of the rotation shaft 6 of the support member 7 in the circumferential direction is In response to this, a revolving motion is performed around the rotating shaft 6. As a result, the distance between the individual cylindrical barrels and the evaporating part disposed below the support member varies, and the following effects are exhibited. That is, the cylindrical barrel located at the lower part of the support member 7 is close to the evaporation part. Therefore, a vapor deposition film is efficiently formed on the surface of the workpiece 30 accommodated in the cylindrical barrel. On the other hand, the object to be processed accommodated in the cylindrical barrel away from the evaporator is released from the heating state and cooled by the distance away from the evaporator. Therefore, softening of the vapor deposition film formed on the surface is suppressed during this time. Thus, if this vapor deposition film forming apparatus is used, it becomes possible to achieve efficient formation of a vapor deposition film and suppression of softening of the formed vapor deposition film simultaneously.

  The film thickness of the vapor-deposited film of aluminum or its alloy formed on the surface of the magnet by the method for producing a rare earth-based permanent magnet having the vapor-deposited film of aluminum or its alloy on the surface of the present invention is desirably 3 μm to 30 μm. If it is less than 3 μm, there is a possibility that an excellent effect of imparting corrosion resistance to the magnet may not be obtained. On the other hand, if it exceeds 30 μm, the effect of imparting corrosion resistance to the magnet does not change and may result in only an increase in production cost.

  Smoothing the coating surface by peening the vapor deposition coating of aluminum or its alloy formed on the surface of the magnet by the method of manufacturing a rare earth permanent magnet having the deposition coating of aluminum or its alloy on the surface of the present invention. The characteristics may be improved by sealing the gap. In the peening treatment, for example, glass beads or steel balls having an average particle diameter of 80 μm to 200 μm (preferably 100 μm to 150 μm) and a Mohs hardness of 3 to 8 are used as the projection material, and a projection of 0.01 MPa to 0.5 MPa. What is necessary is just to perform about 1 minute-1 hour with respect to a film with a pressure. If the peening treatment is insufficient, the coating surface may not be smoothed and the gaps may not be sufficiently sealed, whereas if the coating is excessive, the coating may be peeled off from the magnet surface. Cost. The apparatus used for the peening process is not particularly limited as long as it can project the projection material from the projection nozzle onto the magnet. For example, a blasting apparatus described in JP-A-2001-34175 Can be preferably used. The distance between the projection nozzle and the magnet is desirably 80 mm to 150 mm.

  Another corrosion-resistant film is laminated on the surface of the vapor-deposited film of aluminum or its alloy formed on the surface of the magnet by the method of manufacturing a rare earth permanent magnet having the vapor-deposited film of aluminum or its alloy on the surface of the present invention. Also good. By adopting such a configuration, it is possible to enhance or supplement the characteristics of the deposited film of aluminum or an alloy thereof, or to impart further functionality.

In the present invention, when the rare earth based permanent magnet is an R—Fe—B based permanent magnet, the rare earth element (R) may include at least one of Nd, Pr, Dy, Ho, Tb, and Sm. Furthermore, at least one of La, Ce, Gd, Er, Eu, Tm, Yb, Lu, and Y may be included. Usually, one type of R is sufficient, but in practice, a mixture of two or more types (such as misch metal and didymium) can also be used for reasons of convenience. If the content of R is less than 10 atomic%, the α-Fe phase precipitates, so that high magnetic properties, particularly high coercive force (H _cj ) cannot be obtained. Since the magnetic phase increases and the residual magnetic flux density (B _r ) decreases and a permanent magnet having excellent characteristics cannot be obtained, the R content is desirably 10 atomic% to 30 atomic% of the composition.

The content of Fe is to decrease _{B r} is less than 65 atomic%, since exceeding the high _{H cj} 80 atomic% can not be obtained, is preferable content of 65 atomic% to 80 atomic%. Further, by substituting a part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet. However, if the Co substitution amount exceeds 20 atomic%, the magnetic characteristics will be improved. Is undesirable as it degrades. If Co substitution amount of 5 atomic% to 15 atomic%, B _r is to increase as compared with the case where no replacement, desirable to obtain a high magnetic flux density.

If the B content is less than 2 atomic%, the rhombohedral structure becomes the main phase, and high H _cj cannot be obtained. If it exceeds 28 atomic%, the B-rich non-magnetic phase increases and _Br decreases. Since a permanent magnet having excellent characteristics cannot be obtained, the content is preferably 2 atomic% to 28 atomic%. Moreover, in order to improve the manufacturability and reduce the price of the magnet, at least one of P of 2.0 mass% or less and S of 2.0 mass% or less, and 2.0 mass% or less in total amount. You may contain. Furthermore, the corrosion resistance of the magnet can be improved by substituting a part of B with 30% by mass or less of C.

  Furthermore, at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf, and Ga is added. It is effective in improving the squareness of the demagnetization curve, improving manufacturability, and reducing the price. The rare earth-based permanent magnet may contain impurities inevitable for industrial production in addition to R, Fe, and B.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is limited to the following description and is not interpreted. In the following examples, for example, as described in US Pat. No. 4,770,723, US Pat. No. 4,792,368, US Pat. No. 5,383,978, a rapidly solidified alloy produced by strip casting is roughly pulverized. Sintered magnet (hereinafter referred to as a magnet) having dimensions of 60 mm in length, 30 mm in width, and 3 mm in thickness of Nd ₁₄ Fe ₇₉ B ₆ Co ₁ composition (atomic%) obtained by forming, sintering, heat treatment, and surface processing after pulverization This was performed using a test piece.

(Experiment A)
An aluminum film was deposited on the surface of the magnet test piece using the deposited film forming apparatus (volume in the deposition tank: about 2.37 m ³ ) shown in FIG. In addition, 24 cylindrical barrels (12 cylindrical barrels are further arranged at the rear of the drawing) arranged in the vapor deposition tank have a diameter of 110 mm × length of 600 mm, and a stainless steel mesh wire mesh (opening ratio: About 80%, the shape of the opening: a square having a side of 10 mm and a line width of 2 mm was used.
The magnetic specimen was subjected to sand blasting to remove the oxidized layer on the surface generated by the surface processing in the previous step. The magnet specimen from which the oxide layer has been removed is accommodated in each cylindrical barrel for 1.5 kg, and further, ceramic balls having an average particle diameter of 10 mm (manufactured by Shinto Kogyo Co., Ltd.) are accommodated as stirring media. After evacuating the vacuum processing chamber until the total pressure becomes 4 × 10 ⁻² Pa, Ar gas is introduced so that the total pressure becomes 5 Pa, and then the rotating shaft of the barrel is rotated at 4.5 rpm. The surface of the magnet test piece was cleaned by glow discharge for 15 minutes under the condition of a bias voltage of −1.0 kV.
Subsequently, with a total pressure of 0.6 Pa in the vapor deposition tank and an argon introduction flow rate of 600 mL / min, the diameter was 1.6 mm while rotating the rotating shaft of the barrel at 4.5 rpm under the condition of a bias voltage of −1.0 kV. Commercially available boats heated by resistance heating method with aluminum wire (conforming to JIS A1070) with a hydrogen content of about 5 ppm at a feeding speed of 6.6 g / min (6 installed in the vapor deposition tank, support and energization is the end) Continuously supplied to the red-light emitting part on the upper surface of the clamp system), this is melted, spread and wetted, ionized by evaporating and ionizing, deposition time (starting continuous supply of aluminum wire The time from the start to the end) was set to 15 minutes, and an aluminum film was deposited on the surface of the magnet specimen. At this time, the heating temperature was adjusted by adjusting the current applied to the boat, and the ratio of the wetted and spread area of the molten aluminum to the red heat emission area of the boat was adjusted to six states. Table 1 shows details of the shape of the boat used as the melt evaporation portion and the red-light emitting portion (both are ceramic sintered bodies of 45% by mass of titanium diboride, 40% by mass of boron nitride, and 15% by mass of aluminum nitride). six boat red heat emission area total evaporation tank volume 1 m ³ per 0.61 × ¹⁰ of ^{-2 m 2 ~0.82 × 10 -2 m} 2). Table 2 shows the results of vapor deposition performed under six conditions based on the difference in the ratio of the wetted and spread area of the molten aluminum to the red heat emission area of the boat. The ratio of the wetted and spread area of molten aluminum to the red heat emission area of the boat was confirmed based on a photograph of the upper surface of the boat taken from the observation window in the vapor deposition tank. The temperature of the magnet specimen at the time of vapor deposition is fixed to one of the small-diameter barrels using a temperature data logger (THERMOMETER SE-309: manufactured by CENTER TECHNOLOGY) with a thermocouple clipped to the magnet specimen. It was determined from the temperature history of the magnet specimen fixed to the small diameter barrel. The film thickness of the aluminum coating deposited on the surface of the magnet specimen was measured by cross-sectional observation. Table 2 shows the average film thickness of 10 samples. Further, the surface of the aluminum coating of 10 samples was visually observed to examine the presence or absence of an adherend due to the splash phenomenon of molten aluminum. Table 2 shows the number of samples in which the adherend was observed on the surface of the coating among the 10 samples.

  Next, a shot peening treatment using a glass bead (manufactured by Kyoei Abrasive Co., Ltd.) having a Mohs hardness of 6 and an average particle size of 120 μm is performed on the magnet test piece having an aluminum film deposited on the surface by the above method. The projection pressure was 0.2 MPa, the projection time was 10 minutes, and the distance between the projection nozzle and the magnet test piece was 150 mm. With respect to the magnet body test piece having the aluminum film on which the shot peening treatment has been performed on the surface, the magnet body test piece and aluminum deposited on the surface thereof using a thin film adhesion strength measuring device (Sebastian V type: manufactured by QUAD GROUP). The adhesion between the film and the film was evaluated by the vertical tensile strength (Condition 6 was evaluated using a sample in which no adherend due to the splash phenomenon of molten aluminum was present). The results are shown in FIG. 2 (number of measurement samples: 3).

  As is apparent from Table 2 and FIG. 2, by gradually increasing the ratio of the wetted and spread area of the molten aluminum to the red light emission area of the boat, the temperature rise gradient of the magnet specimen within the vapor deposition processing time gradually decreases, The adhesion between the magnet body test piece and the aluminum coating gradually increased. In condition 3 to condition 6, by setting the wet spreading area to 60% or more of the red-light emission area of the boat, the temperature increase gradient of the magnet specimen is 10 ° C./min or less (the temperature per film thickness of the deposited film formed). The increase rate was 20 ° C./μm or less), and the average value of the vertical tensile strength exceeded 70 MPa set as the acceptance criterion (♦ in FIG. 2). Also, under these conditions, the variation in the vertical tensile strength of the three samples was small (the upper end of the vertical bar in FIG. 2 is the numerical value of the sample showing the maximum value among the three samples, and the lower end is the minimum) Sample number showing the value). However, in condition 6, there was a problem in practical use because a sample in which an adherend due to a splash phenomenon of molten aluminum was observed on the surface of the aluminum coating was generated. On the other hand, in conditions 1 and 2, the average value of the vertical tensile strength was less than 70 MPa, and the variation in the vertical tensile strength of the three samples was very large. This is because a large amount of radiant heat is released from the portion where the molten aluminum in the red-light emitting portion of the boat is not wet and spread, and the temperature rise gradient of the magnet specimen exceeds 10 ° C./min. Since the specimen has reached a temperature exceeding 250 ° C, when cooled to room temperature after that, due to thermal strain based on the difference in thermal expansion coefficient between the magnet specimen and the aluminum coating, It was assumed that this was due to a decrease in adhesion.

  The arithmetic average roughness (Ra) and the maximum height roughness (Rz) of the aluminum coating deposited on the surface of the magnet specimen before the shot peening treatment were measured using a surface roughness measuring instrument (Surfcom 1400A: Tokyo Seimitsu). (In accordance with JIS B0601: 2001, a sample having no deposit due to a splash phenomenon of molten aluminum is used for condition 6). The results are shown in FIGS. 3 and 4 (number of measurement samples: 3). As apparent from FIG. 3 and FIG. 4, by gradually increasing the ratio of the molten aluminum wetting and spreading area to the boat's red-light emitting area, the temperature rise gradient of the magnet specimen within the deposition process time gradually decreases, The average value of surface roughness (◇ ◆ in Fig. 3 and Fig. 4) also varies (the upper end of the vertical bar in Figs. 3 and 4 is the numerical value of the sample showing the maximum value among the three samples, and the lower end is the minimum value) The numerical value of the sample shown was also gradually reduced. In condition 1 and condition 2, the variation in the surface roughness is particularly large at the edge. The temperature rise gradient of the magnet body test piece exceeded 10 ° C./min, and it was deposited on the surface of the magnet body test piece. It was speculated that the columnar crystal structure of the aluminum coating rapidly grew coarsely, resulting in disturbance of the coating structure.

(Experiment B)
An experiment similar to Experiment A was carried out except that an aluminum alloy wire containing 6% by mass of magnesium and having a hydrogen content of 1 ppm was used. It was.

  INDUSTRIAL APPLICABILITY The present invention has industrial applicability in that it can provide a method for producing a rare earth permanent magnet in which a deposited film of aluminum or an alloy thereof is formed on the surface with excellent adhesion.

1 Deposition tank 2 Boat (melting evaporation part)
DESCRIPTION OF SYMBOLS 3 Support table 4 Boat support stand 5 Cylindrical barrel 6 Rotating shaft 7 Support member 8 Support shaft 9 Wire of vapor deposition material 10 Feeding reel 11 Heat-resistant protective tube 12 Notch window 13 Feeding gear 30 Workpiece (rare earth permanent magnet) )

Claims (7)

  By evaporating while evaporating the wire evaporation material of wire-like aluminum or its alloy continuously into the melt evaporation part heated by the resistance heating method in the vapor deposition tank, the vapor deposition film of aluminum or its alloy is formed on the surface of the rare earth-based permanent magnet. A vapor deposition film of aluminum or an alloy thereof is formed on the surface, wherein the vapor deposition process is performed by controlling the temperature rise gradient of the magnet between the start and the end of the vapor deposition process to 10 ° C./min or less. A method for producing a rare earth permanent magnet having   2. The method according to claim 1, wherein the temperature rise gradient is controlled by controlling the radiant heat from the melt evaporation section.   Controlling the radiant heat from the melting and evaporating part, using a boat that melts and evaporates the molten aluminum or its alloy on the red-light emitting part on the upper surface as the melting and evaporating part, and wets the molten aluminum or its alloy to the red-light emitting area of the boat The manufacturing method according to claim 2, wherein the method is performed by controlling a ratio of the spread area.   4. The method according to claim 3, wherein the wetted and spread area of the molten aluminum or its alloy is 60% or more of the red heat emission area of the boat.   The manufacturing method according to claim 3 or 4, wherein the wetted and spread area of the molten aluminum or its alloy is 90% or less of the red heat emission area of the boat.   The manufacturing method according to claim 1, wherein the maximum temperature of the rare earth permanent magnet is suppressed to 250 ° C. or less. The method according to any one of claims 1 to 6, wherein the vapor deposition time is 10 minutes to 30 minutes.