JP2005136015A - Orientation method of permanent magnet powder and manufacturing method of permanent magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet having high magnetic characteristics being attained by a method for orienting permanent magnet powder in the direction of an orientation magnetic field. <P>SOLUTION: In the inventive orientation method of permanent magnet powder, a space having length L in the direction of orientation magnetic field is filled with permanent magnet powder at a filling density of 1.4-4.2 g/cm<SP>3</SP>. Subsequently, an inclining magnetic field is formed such that the magnetic field strength indicates a highest value at a position in the space other than the center in the direction of orientation magnetic field, and the magnetic field strength at the end part in the direction of orientation magnetic field remote from the position indicating the highest value becomes lower than the highest value by 1.0 T or more. A magnetic force acts on the permanent magnet powder filling the space and field orientation is carried out while increasing the filling density of permanent magnet powder relatively in the vicinity of the position where the magnetic field strength indicates a highest value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for orienting a permanent magnet powder, a method for producing a permanent magnet, and a permanent magnet obtained by using these methods.

  R-Fe-B permanent magnets (such as Patent Document 1), which are typical high-performance permanent magnets, have excellent magnetic properties and are used in various applications such as various motors and actuators. In addition, R-Fe-B permanent magnets having various compositions have been proposed so as to exhibit various magnet characteristics. However, there are strong demands for reducing the size, weight, and functionality of electric / electronic devices, and there is a demand for higher performance and cost reduction of R-Fe-B permanent magnets.

  Improvements in the performance of R-Fe-B permanent magnets include an improvement in residual magnetic flux density (Br), an improvement in coercive force (iHc), an improvement in temperature characteristics, and an improvement in corrosion resistance. Among them, the following means are known to be effective for improving the residual magnetic flux density.

(1) It is a ferromagnetic phase, and the abundance of the main phase R ₂ Fe ₁₄ B phase is increased.

  (2) Increase the density of the sintered body to the theoretical density.

  (3) Increasing the degree of orientation of the main phase crystal grains in the easy axis direction.

In order to achieve the above (1), the composition of the magnet is brought close to the stoichiometric composition of R ₂ Fe ₁₄ B, specifically, the amount of R (rare earth) is reduced and the amount of oxygen is reduced. Is preferred.

  In order to achieve the above (2), it is effective to finely disperse the R-rich phase in the alloy by adopting a strip casting method for producing the alloy, thereby improving the sinterability. is there.

  Furthermore, in order to achieve the above (3), it is effective to perform molding after sufficiently orienting the permanent magnet powder. In order to sufficiently orient the permanent magnet powder, a method of applying a high strength magnetic field by a pulse magnetic field or improving the lubricity of the permanent magnet powder is known. It is also known to form a uniform magnetic field distribution in the molding space in order to prevent variation in orientation.

As a method for sufficiently orienting the above permanent magnet powder, for example, an R—Fe—B alloy powder is filled in a mold to a packing density of 1.4 to 3.5 g / cm ³ , and a pulse of 10 kOe or more is instantaneously generated. There has been proposed a method in which a magnetic field is applied by reversing the direction of the magnetic field repeatedly, and orientation is performed thereby, followed by cold isostatic pressing (Patent Document 2).

  The method according to this proposal is characterized by applying a high pulse magnetic field while reversing the direction of the magnetic field repeatedly, and describes that a pulse magnetic field having a magnetic field strength of 35 kOe is repeatedly applied. Although there is no description about magnetic field distribution, it seems that the uniform magnetic field is applied with respect to the whole mold.

  Further, as a method for obtaining a uniform degree of orientation, when orienting magnetic powder in a predetermined direction in a magnetic field having a predetermined magnetic field strength, a weak magnetic field region or a no magnetic field having a magnetic field strength weaker than the orientation magnetic field region having a magnetic field strength. A method has been proposed in which magnetic powder is relatively moved from a region to an orientation magnetic field region (Patent Document 3).

  According to the above proposal, a bonded magnet compound (a mixture of a magnet and a resin) is disposed below a space provided in a cavity of a press device in which a magnetic field strength sequentially increases from the lower side to the upper side. Leave free space above the compound. By applying a static magnetic field in this state, the compound moves upward in the strong magnetic field region against the weight. At this time, since a free space is formed around the compound, the frictional force between the compounds decreases, and the rotational movement of the compound becomes easy. The moved compound is connected in a chain shape in the direction of the magnetic field and is uniformly oriented.

Conventionally, as typified by Patent Document 2 and Patent Document 3, various proposals have been made to increase the degree of orientation of the main phase crystal grains in the easy axis direction, and the more uniform the magnetic field distribution, the better the orientation magnetic field. The predominance was that the higher the better.
JP 59-46008 A JP-A-8-167516 JP 2001-93712 A

The theoretical value of the residual magnetic flux density (Br) in the R—Fe—B permanent magnet is assumed to be 1.6 T which is the saturation magnetization Is of the R ₂ Fe ₁₄ B intermetallic compound, and the maximum energy product ((BH) max. ) And 512 kJ / cm ³ . Since this is a value based on the R ₂ Fe ₁₄ B intermetallic compound (single crystal), it is substantially possible to obtain a residual magnetic flux density of 1.6 T in the form of sintered magnets and bonded magnets on the market. It is impossible, but it can be as close as possible.

  However, in the method according to Patent Document 2, the residual magnetic flux density (Br) is about 1.4T at the maximum, and in the method according to Patent Document 3, an example of a bonded magnet is described. The residual magnetic flux density Br obtained in the above is not specifically described, and the effect obtained when this method is also applied to a sintered magnet is unknown. In any case, in order to satisfy recent requirements, it is necessary to obtain a residual magnetic flux density (Br) higher than that.

  The present invention further increases the degree of orientation in the easy axis direction of the main phase grains by an orientation method that fundamentally changes the conventional idea that the higher the orientation magnetic field is, the better the magnetic field distribution is. -An object of the present invention is to provide a permanent magnet having high magnetic properties corresponding to a reduction in size, weight and functionality of electronic equipment.

A method for orienting a permanent magnet powder according to the present invention is a method for orienting a permanent magnet powder in the direction of an orientation magnetic field, and the density of the permanent magnet powder is filled in a space having a length L in the orientation magnetic field direction. The step of filling with 1.4 to 4.2 g / cm ³ , and the magnetic field strength shows the highest value at a position other than the center in the orientation magnetic field direction of the space, and among the both ends of the orientation magnetic field direction of the space Permanent magnets filled in the space by forming a gradient magnetic field in which the magnetic field strength at the end far from the position where the magnetic field strength shows the maximum value is 1.0T or more lower than the maximum value of the magnetic field strength. And a gradient magnetic field application step of performing magnetic field orientation while relatively increasing the packing density of the permanent magnet powder in the vicinity of the position where the magnetic force is applied to the powder, thereby showing the maximum value of the magnetic field strength.

  In a preferred embodiment, the gradient magnetic field applying step is a step of applying a pulse magnetic field.

  In a preferred embodiment, the gradient magnetic field applying step is performed a plurality of times.

  In a preferred embodiment, the polarity of the applied magnetic field is changed between the first gradient magnetic field application step and the second gradient magnetic field application step among the gradient magnetic field application steps performed a plurality of times.

  In a preferred embodiment, the gradient polarity indicated by the intensity distribution of the applied magnetic field is changed between the first gradient magnetic field application step and the second gradient magnetic field application step among the gradient magnetic field application steps performed a plurality of times. Let

  In a preferred embodiment, the first gradient magnetic field application step and the second gradient magnetic field application step are repeated.

  In a preferred embodiment, the method further includes a step of applying a magnetic field having a maximum magnetic field strength at the center in the orientation magnetic field direction of the space.

  In a preferred embodiment, the orientation magnetic field has a strength distribution including a portion where the magnetic field strength changes substantially linearly.

  In a preferred embodiment, the maximum value of the orientation magnetic field in the gradient magnetic field application step is set to 1.0 T or more.

  In a preferred embodiment, in the step of applying the gradient magnetic field, when a magnetic force is applied to the permanent magnet powder filled in the space, movement of the permanent magnet powder in the orientation magnetic field direction is restricted.

  In a preferred embodiment, the permanent magnet powder is composed of an R—Fe—B magnet powder.

  In a preferred embodiment, the permanent magnet powder is a powder produced by pulverizing a slab obtained by a strip casting method.

  In a preferred embodiment, the space filled with the permanent magnet powder is defined by a flexible mold.

  In a preferred embodiment, the space is defined by a press device die and upper and lower punches.

  The method for producing a permanent magnet of the present invention includes a step of preparing a permanent magnet powder, a step of orienting the permanent magnet powder by any of the above-described permanent magnet powder orientation methods, and molding and sintering the permanent magnet powder. Including the step of.

  In a preferred embodiment, the molding is performed by cold isostatic pressing.

  In a preferred embodiment, the molding is performed by a uniaxial compression press.

  The permanent magnet of the present invention is a permanent magnet obtained by any one of the above-described methods for producing a permanent magnet, and has an orientation degree of 92% or more.

  The permanent magnet of the present invention is a permanent magnet obtained by any one of the above-described methods for producing a permanent magnet, and exhibits a residual magnetic flux density (T) value of 90% or more of the theoretical value.

  According to the method for aligning permanent magnet powder of the present invention, the degree of orientation in the easy axis direction of the main phase crystal grains having ferromagnetism can be increased to the limit.

For example, when the most preferable conditions are selected by applying the present invention to a method for manufacturing an R—Fe—B based sintered magnet, the value of the residual magnetic flux density (Br) is 1.533 T (approximately 96% of the theoretical value). It is possible to obtain a permanent magnet having extremely high magnetic properties, which has never existed before, with a maximum energy product ((BH) max) value of 460 kJ / m ³ . As a result, it is possible to sufficiently meet the recent demands for smaller and lighter electrical and electronic devices and higher functionality.

  Further, since the present invention is an extremely simple method, the cost of the permanent magnet is not increased. According to the present invention, an extremely high residual magnetic flux density Br can be obtained even if the magnetic field strength is relatively low. In other words, when the residual magnetic flux density Br of the same level as the conventional one is obtained, the strength of the orientation magnetic field may be set low. Therefore, since it becomes possible to orient with a magnetic field lower than before, the coil power supply in the press apparatus can be miniaturized and energy saving can be realized.

  Furthermore, the permanent magnet obtained by the present invention is extremely excellent in the squareness of the demagnetization curve.

  The present invention has the effect that the orientation degree of the easy axis of the main phase crystal grains having ferromagnetism can be increased to the limit. Therefore, as the permanent magnet powder applicable to the present invention, the main phase crystal having ferromagnetism is used. A permanent magnet powder having grains can be applied. For example, ferrite magnets, R—Co magnets, R—Fe—B magnets, and the like. Among these, an R—Fe—B based magnet, in particular, an R—Fe—B based sintered magnet can exhibit the effect of the present invention most.

  When using an R-Fe-B permanent magnet, a raw material alloy having a thickness of 0.1 to 1.0 mm obtained by strip casting is coarsely pulverized by a hydrogen pulverization method and then further finely pulverized by a jet mill pulverization or the like. It is preferable to use magnet powder. The coarse pulverization and fine pulverization of the raw material alloy are not limited to the above methods, and can be performed using other known methods. Moreover, it is preferable to add a known lubricant to the coarse powder obtained by coarse pulverization or the fine pulverized powder obtained by fine pulverization, since the degree of orientation of the permanent magnet powder can be further improved.

  Hereinafter, an example of the orientation method of the permanent magnet powder according to the present invention will be described. Here, an example in which powder of an R—Fe—B based sintered magnet is used as the permanent magnet powder will be described.

  First, a conventional alignment method will be described with reference to FIG. In the conventional orientation method, as shown in FIG. 6, for example, the magnetic field distribution in a space such as a rubber mold or a cavity of a press machine has a maximum magnetic field strength at the center of the length L in the orientation direction of the space. In addition to being located, it has a uniform magnetic field in the vicinity of the central portion, and the magnetic field strength decreases toward the end. In such a magnetic field distribution, molding is performed near the center (within a uniform magnetic field) where the highest value of the applied magnetic field strength is located.

  Next, with reference to FIG.1 and FIG.2, the orientation method of the permanent magnet powder of this invention is demonstrated.

  According to the orientation method of the present invention, the magnetic field strength of the space to be filled with powder is formed to have the distribution shown in FIG. More specifically, the magnetic field strength shows the maximum value at a position shifted from the center of the space having the length L in the alignment direction. In the example of FIG. 1, there is a position showing the maximum value of the magnetic field strength at a position close to the left end portion in the figure, and the magnetic field strength decreases as going to the right end portion. That is, the distribution of the magnetic field intensity in the space filled with the magnet powder is asymmetric and changes along the orientation direction. Such a magnetic field is referred to as a “gradient magnetic field”.

  In the present invention, the difference between the maximum value (a) of the magnetic field strength in the space and the magnetic field strength (b) at the end of the space far from the position where the magnetic field strength shows the maximum value (“ A pulsed magnetic field is applied so that “ab”) is 1.0 T or more.

  Note that the end portion (c) closer to the position showing the maximum value of the magnetic field strength has a lower magnetic field strength than the maximum value (a), but the end portion (b) far from the position showing the maximum value. However, it is desirable that the magnetic field strength is high. At this time, the left area including the position where the magnetic field strength shows the maximum value is the high magnetic field strength side with respect to the center of the figure, and the right area in the figure including the end far from the position where the maximum value is shown is low. On the magnetic field strength side.

  FIG. 2 is a most preferred magnetic field distribution example according to the present invention. It is characterized in that the applied magnetic field intensity decreases while being inclined substantially linearly from the left end to the right end.

  When the magnetic field strength is high in the vicinity where the highest value of the magnetic field strength is located, low in the vicinity of the end far from the highest value, and magnetic field orientation is performed in the gradient magnetic field, the packing density of the permanent magnet powder in the space is the magnetic field. It is a feature of the present invention that the maximum value of the magnetic field strength in the distribution is high in the vicinity (on the high magnetic field strength side) and low near the end farther from the maximum value (on the low magnetic field strength side).

  The change in the packing density will be described with reference to FIG. 1 as an example. As shown in FIG. 1, when orientation is performed in a gradient magnetic field having the highest magnetic field strength on the left side of the center of the space, each permanent magnet powder has a magnetic field strength. Although the force to move to the side where the highest value is located (high magnetic field strength side, left side in the figure) works, as a result, there is a space wall surface at the end, so permanent magnet powder on the wall surface of this space Are pushed together and the packing density is increased. On the other hand, the packing density on the end portion side (low magnetic field strength side, right side in the figure) far from the maximum value of the magnetic field strength is low. At this time, the average packing density in the entire volume in the space is the same as the packing density before application of the magnetic field.

  As described above, the filling density of the permanent magnet powder after application of the magnetic field is increased on the high magnetic field strength side in the magnetic field distribution, so that the permanent magnet powder is fixed while being oriented in the applied magnetic field direction. Therefore, after the application of the pulse magnetic field, the fixed state is maintained, and there is an advantage that it is not necessary to continue to apply an external magnetic field such as a static magnetic field.

According to the present invention, it is considered that the degree of orientation of the permanent magnet powder is improved by the movement of the permanent magnet powder and the change of the packing density in the space. For the movement of the permanent magnet powder and the change in the packing density of the permanent magnet powder in the space, the packing density of the permanent magnet powder to be filled in the space should be 1.4 to 4.2 g / cm ³ before applying the magnetic field. Caused by. If the packing density is less than 1.4 g / cm ³ , the movement of the permanent magnet powder occurs, but the packing density does not change, the orientation state is not maintained after applying the pulse magnetic field, and the orientation degree of the permanent magnet powder decreases. On the other hand, if the packing density exceeds 4.2 g / cm ³ , the movement of the permanent magnet powder is difficult to occur, and the degree of orientation of the permanent magnet powder is not preferable. A more preferable range is 3.0 to 4.0 g / cm ³ .

  In the method disclosed in Patent Document 2, the pulse magnetic field is repeatedly applied while being reversed in the mold. However, Patent Document 2 does not teach or suggest the use of a gradient magnetic field. For this reason, in the method of patent document 2, it is thought that the uniform magnetic field is applied with respect to the whole mold as usual. Therefore, according to the method of Patent Document 2, the movement of the permanent magnet powder and the change in the packing density of the permanent magnet powder in the space do not occur, and the effect of the present invention cannot be obtained.

  On the other hand, in the method disclosed in Patent Document 3, the magnetic powder is moved from the weak magnetic field region or the non-magnetic field region having a magnetic field strength weaker than the orientation magnetic field region (forming space) to the orientation magnetic field region. However, the magnetic powder is not filled so as to have a predetermined density in a specific space, and the magnetic powder moves in a space that widely includes a portion where the magnetic powder does not exist. For this reason, the movement of the magnetic powder is not restricted by the member that partitions the space, and the entire magnetic powder moves relatively freely in the space. Even after the movement, the magnetic powder is attracted and gathered by the static magnetic field generated by the coil. For this reason, there is no change in the packing density depending on the position of the magnetic powder. In the first place, since a wide space is formed in which the magnetic powder can freely move, it cannot be said that the magnetic powder is filled. I don't think the concept. Therefore, the change in the packing density of the permanent magnet powder in the space does not occur with the movement of the permanent magnet powder, and the effect of the present invention cannot be obtained.

  Moreover, in patent document 3, since the average powder density in space is very low, the orientation direction of a magnetic powder is not fixed after orientation. Therefore, it is necessary to continue applying the static magnetic field after the orientation and maintain the orientation until the molding is completed.

  Conventionally, there has been a concept that the higher the orientation magnetic field, the better, and the better the magnetic field distribution, but in the present invention, the idea and others are fundamentally changed.

In the present invention, the space filled with magnetic powder for orientation (the space in which the distribution of the magnetic field strength formed varies along the orientation direction) is a cavity formed by the die of the pressing device and the upper and lower punches. Or, it is preferably defined by the degree of malleability having flexibility such as rubber or resin. As described above, in the present invention, permanent magnet powder is packed in such a space at a packing density of 1.4 to 4.2 g / cm ³ , and thus the permanent magnet powder moves in a lump in the space. I can't. That is, since the individual particles constituting the permanent magnet powder can freely move and rotate on a micro scale, a distribution occurs in the packing density, but the inner wall of the space regulates the movement of the powder, The magnetic powder does not move as a mass in the space described in Patent Document 2.

  In the present invention, the applied magnetic field is a pulsed magnetic field. The maximum value in the intensity distribution of the applied magnetic field is preferably 1.0 T or more. If the maximum value of the magnetic field strength is less than 1.0 T, it is difficult to orient the permanent magnet powder, which is not preferable. The upper limit value of the maximum value of the magnetic field strength may be determined in consideration of the size of the coil power supply device, power consumption, and the like within the range of magnetizing devices that are generally used at present. However, by using the orientation method by the gradient magnetic field according to the present invention, a permanent magnet having magnetic characteristics equivalent to those of the conventional one can be obtained even when a relatively low magnetic field is applied without applying a high magnetic field strength as in the conventional orientation method. It becomes possible. In other words, by applying a high magnetic field strength as in the conventional case, it becomes possible to obtain a permanent magnet having magnetic properties that are significantly superior to those of the conventional case.

  If the orientation method according to the present invention is performed once in a gradient magnetic field, the effect of the present invention can be obtained, but the effect can be further improved by performing it twice or more (multiple times). When performing it several times, it is preferable to make the polarity of the applied magnetic field different between the first orientation and the second orientation or to make the strength different.

  The case where the polarity of the applied magnetic field is changed will be described with reference to FIG. 1. For example, the first time with the high magnetic field strength side (left side in the figure) as the N pole and the low magnetic field strength side (right side in the figure) as the S pole. In the second time, the high magnetic field strength side (left side in the figure) is the S pole and the low magnetic field strength side (right side in the figure) is the N pole. In this case, the movement of the permanent magnet powder hardly occurs, but the unoriented powder can be oriented, and the degree of orientation of the permanent magnet powder is improved.

  Next, referring to FIG. 1, the case where the gradient direction of the applied magnetic field is changed will be described. The high magnetic field strength side (left side in the figure) is the N pole, and the low magnetic field strength side (right side in the figure) is the S pole. When the first orientation is performed, the second time is a low magnetic field strength on the left side in the figure and a high magnetic field strength on the right side in the figure. That is, the downward slope is replaced with the upward slope. In this case, the movement of the permanent magnet powder and the change of the packing density in the space occur, and the degree of orientation of the permanent magnet powder is further improved. At this time, the polarity may be switched as it is.

  Moreover, the case where the above-described polarity is changed can be repeated, the case where the inclination direction is changed can be repeatedly performed, or a combination thereof can be repeatedly performed. In this case, it is most preferable that the first and second orientations have different inclination directions and are repeated.

  In the present invention, the degree of orientation of the permanent magnet powder can be improved by the above-described configuration, but when proceeding to the next molding step while the packing density is changed, a density difference occurs in the molded body. Thus, although the magnetic characteristics are remarkably improved by improving the degree of orientation, there is a possibility of causing deformation of the sintered body and an increase in processing steps due to the deformation.

  Therefore, the magnetic field distribution in which the highest value of the intensity of the applied magnetic field is located at the center of the length L in the alignment direction of the space after performing the alignment by one or a plurality of gradient magnetic fields by the alignment method of the present invention, that is, By orienting at least once with a uniform magnetic field distribution that has been conventionally performed, the density difference of the compact can be eliminated, and deformation of the sintered compact can be suppressed. However, even in this case, as described above, filling is performed at a specific packing density before application of a magnetic field and orientation is performed in a gradient magnetic field. It goes without saying that the degree of orientation of the permanent magnet powder is improved as compared with that oriented by a pulsed magnetic field that is repeatedly reversed in a magnetic field (Patent Document 2).

  The powder oriented by the permanent magnet powder orientation method according to the present invention described above is formed by the following method.

  When the permanent magnet powder in the mold having flexibility is oriented, the molding is preferably performed by cold isostatic pressing. As described above, since the permanent magnet powder after orientation is fixed in a predetermined orientation direction in the mold, it is basically unnecessary to apply a magnetic field during molding. Of course, there is no problem even if a magnetic field is applied for molding.

  When the permanent magnet powder is oriented in the cavity formed by the die and the upper and lower punches in the press apparatus, the molding is performed by uniaxial compression press using the upper and lower punches. At this time, similarly to the above, it is not basically necessary to apply a magnetic field during molding, but a magnetic field may be applied.

  The molded body after molding is sintered and heat-treated by a known means to form a sintered magnet.

  Thereby, it is possible to obtain a permanent magnet in which the orientation degree of the easy axis of the main phase crystal grains is increased to the limit.

  The obtained permanent magnet has an orientation degree of the sintered body of 92% or more, and can exhibit a residual magnetic flux density (Br) of 90% or more of the theoretical value (1.6T). This distribution altitude and residual magnetic flux density exhibit extremely excellent characteristics that could not be obtained by conventional methods.

(Example 1)
Nd _28.5 B _1.00 Co _0.50 Cu _0.05 Al _{0.05 The} remainder Fe (mass%) was melted, and the molten alloy was rapidly cooled by a strip casting method to obtain an alloy slab. The alloy slab was 0.3 mm thick.

  The alloy slab was coarsely pulverized by hydrogen pulverization and dehydrogenation, and further finely pulverized to a mean particle size of 3 μm by jet mill pulverization.

Next, the obtained finely pulverized powder was filled in a rubber mold having a diameter of 25 mm and a height of 25 mm at a filling density of 3.5 g / cm ³ , and the rubber mold was sealed with a rubber lid.

  The rubber mold was oriented in the gradient orientation (1) region of the magnetic field distribution shown in FIG. As shown in FIG. 3, the magnetic field distribution is such that the maximum value (8.0 T) of the magnetic field strength is located outside the center of the length L in the alignment direction (left side in FIG. 3), and the maximum value and the alignment direction The strength difference from the end portion (4.5T) far from the maximum value was 3.5T. The orientation is one time (first orientation) in the magnetic field distribution of the tilt orientation (1) according to FIG. 3, and the magnetic field distribution in which the distribution of the tilt orientation (1) is completely reversed (the magnetic field strength at the measurement position of 31 mm is 8. This was performed by applying a pulsed magnetic field once (second orientation) at 0 T, the magnetic field intensity at a measurement position of 57.5 mm was 4.5 T, and the intensity difference was 3.5 T.

  Next, after the oriented rubber mold was formed by cold isostatic pressing, the rubber mold was removed, the internal molded body was taken out, this molded body was sintered at a temperature of 1373K for 2 hours, and further at 823K for 1 hour. Heat treatment was performed to produce a sintered magnet.

(Example 2)
A sintered magnet was produced under the same conditions as in Example 1 except that the orientation was performed once in the gradient orientation (1) region of the magnetic field distribution shown in FIG.

(Example 3)
Orientation once in the gradient orientation (2) region of the magnetic field distribution shown in FIG. 3 (the magnetic field strength at the measurement position 40 mm is 7.5 T, the magnetic field strength at the measurement position 67 mm is 2.5 T, and the strength difference is 5.0 T). Firing (first orientation), followed by firing under the same conditions as in Example 1, except that a pulsed magnetic field is applied once (second orientation) with a magnetic field distribution in which the distribution of the tilt orientation (2) is completely reversed. A magnetized magnet was produced.

Example 4
A sintered magnet was produced under the same conditions as in Example 1 except that the orientation was performed once in the gradient orientation (2) region of the magnetic field distribution shown in FIG.

(Comparative Example 1)
A sintered magnet was produced under the same conditions as in Example 1 except that orientation was performed once in the central orientation region of the magnetic field distribution shown in FIG.

(Comparative Example 2)
A sintered magnet was produced under the same conditions as in Example 1 except that the orientation was performed once in the central orientation region of the magnetic field distribution shown in FIG.

  FIG. 4 shows Example 1 (♦ mark of inclination (1)), Example 2 (■ mark of inclination (1)), Example 3 (♦ mark of inclination (2)), Example 4 (Inclination (2)) The solid magnetic flux density Br (T) of Comparative Example 1 (center mark) and Comparative Example 2 (center mark) are shown.

  As is clear from FIG. 4, the magnet of Example 1 according to the present invention in which the magnetic field strengths of the first and second orientations are different in a gradient magnetic field is oriented with different polarities in a uniform magnetic field. It can be seen that Br is greatly improved as compared with the magnet according to Comparative Example 1. In addition, the magnet of Example 2 according to the present invention in which the orientation was once performed in the gradient magnetic field also showed an improvement in Br as compared with the conventional comparative example 2 in which the orientation was once in the uniform magnetic field. It can be seen that it has Br equivalent to 1.

  Furthermore, it should be noted that the magnets of Example 3 and Example 4 in which the maximum value of the magnetic field intensity is oriented with a magnetic field distribution lower than the gradient (1) have a higher Br than the magnets of Example 1 and Example 2. That's what it means. This result fundamentally changes the conventional idea that “the more uniform the magnetic field distribution is,” and is a major feature of the present invention.

  From these results, even if the magnetic field strength is relatively low, extremely high Br can be obtained by orienting in a gradient magnetic field. In other words, if the same level of Br as in the conventional case is obtained, the magnetic field strength may be lower. That is, since it becomes possible to orientate with a magnetic field lower than before, it is possible to realize a reduction in the size of the coil power source, energy saving, and the like as compared with the conventional case.

  FIG. 5 shows the squareness of the demagnetization curve. It can be seen that the magnets of Example 1 and Example 2 according to the present invention are extremely excellent in squareness as compared with the conventional comparative example. Moreover, similarly to the tendency of Br, the magnets of Examples 3 and 4 are superior to the magnets of Examples 1 and 2 in terms of squareness.

  This is presumably because the movement of the permanent magnet powder and the change of the packing density in the space occur simultaneously due to the orientation in the gradient magnetic field.

  The present invention is widely applied to permanent magnets for which high performance is strongly demanded.

It is explanatory drawing which shows the orientation method of the permanent magnet of this invention. It is explanatory drawing which shows the orientation method of the permanent magnet of this invention. It is explanatory drawing which shows magnetic field distribution. It is a graph which shows the relationship between the orientation method and Br. It is a graph which shows the relationship between the orientation method and the squareness of a demagnetization curve. It is explanatory drawing which shows the orientation method of the conventional permanent magnet.

Claims (19)

A method for orienting a permanent magnet powder that orients the permanent magnet powder in the orientation magnetic field direction,
Filling the interior of a space having a length L in the direction of the orientation magnetic field with permanent magnet powder at a packing density of 1.4 to 4.2 g / cm ³ ;
The magnetic field strength at the position other than the center in the orientation magnetic field direction of the space has the highest value, and the magnetic field at the end far from the position at which the magnetic field strength has the highest value among both ends of the orientation magnetic field direction of the space. By forming a gradient magnetic field whose strength is 1.0 T or more lower than the maximum value of the magnetic field strength, a magnetic force is exerted on the permanent magnet powder filled in the space, thereby showing the maximum value of the magnetic field strength. A gradient magnetic field application step of performing magnetic field orientation while relatively increasing the packing density of the permanent magnet powder in the vicinity of the position;
Method for orienting permanent magnet powder containing   The method for orienting a permanent magnet powder according to claim 1, wherein the gradient magnetic field applying step is a step of applying a pulse magnetic field.   The method for orienting permanent magnet powder according to claim 2, wherein the gradient magnetic field applying step is performed a plurality of times. The permanent magnet powder according to claim 3, wherein the polarity of the applied magnetic field is changed between the first gradient magnetic field application step and the second gradient magnetic field application step among the gradient magnetic field application steps performed a plurality of times. Orientation method. The gradient polarity indicated by the intensity distribution of the applied magnetic field is changed between the first gradient magnetic field application step and the second gradient magnetic field application step among the gradient magnetic field application steps performed a plurality of times. An orientation method of the permanent magnet powder as described.   The method for orienting permanent magnet powder according to claim 4 or 5, wherein the first gradient magnetic field application step and the second gradient magnetic field application step are repeated.   The method for orienting permanent magnet powder according to any one of claims 1 to 6, further comprising a step of applying a magnetic field having a maximum magnetic field strength at the center in the orientation magnetic field direction of the space.   The method for orienting a permanent magnet powder according to any one of claims 1 to 7, wherein the orientation magnetic field has a strength distribution including a portion where the magnetic field strength changes substantially linearly.   The permanent magnet powder orientation method according to any one of claims 1 to 8, wherein the maximum value of the orientation magnetic field in the gradient magnetic field application step is set to 1.0 T or more.   The permanent magnet according to any one of claims 1 to 9, wherein, in the step of applying a gradient magnetic field, when a magnetic force is applied to the permanent magnet powder filled in the space, movement of the permanent magnet powder in an orientation magnetic field direction is restricted. Powder orientation method.   The said permanent magnet powder is the orientation method of the permanent magnet powder in any one of Claim 1 to 10 comprised from the powder of the R-Fe-B type magnet.   The method for orienting a permanent magnet powder according to claim 1, wherein the permanent magnet powder is a powder produced by pulverizing a slab obtained by a strip casting method.   The method for orienting permanent magnet powder according to claim 1, wherein the space filled with the permanent magnet powder is defined by a flexible mold.   The method for orienting a permanent magnet powder according to any one of claims 1 to 12, wherein the space is defined by a die and a vertical punch of a press device. Preparing a permanent magnet powder;
Orienting the permanent magnet powder by the method of orienting permanent magnet powder according to any one of claims 1 to 14,
Forming and sintering the permanent magnet powder;
The manufacturing method of the permanent magnet which further contains.   The method of manufacturing a permanent magnet according to claim 15, wherein the forming is performed by cold isostatic pressing.   The method of manufacturing a permanent magnet according to claim 15, wherein the forming is performed by a uniaxial compression press. A permanent magnet obtained by the method for producing a permanent magnet according to any one of claims 15 to 17,
A permanent magnet having an orientation degree of 92% or more. A permanent magnet obtained by the method for producing a permanent magnet according to any one of claims 15 to 17,
A permanent magnet having a residual magnetic flux density (T) value of 90% or more of the theoretical value.

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