JP2006258616A - Method of evaluating orientation degree, rare-earth sintered magnet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating an orientation degree capable of accurately evaluating the orientation degree in a macroscopic region, and to achieve a rare-earth sintered magnet whose whole orientation degree is high and which is excellent in magnetization characteristic or the like. <P>SOLUTION: A molding obtained by compressively molding rare-earth alloy powder or its sintered compact is equally divided into odd number of pieces, and X-ray diffraction processes are applied on the divided pieces of the center section and the outermost section, and then orientation degrees of respective divided pieces are calculated by using a Lotgering method, thereby evaluating variations in the orientation degrees. When calculating them, vector compensation is applied on X-ray diffraction intensity of each diffraction peak. In the rare-earth sintered magnet, the difference of calculated orientation degree subjected to the vector compensation between the divided piece of the center section and the divided piece of the outermost section is 1.5% or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an orientation degree evaluation method for accurately evaluating the degree of orientation of a compact or sintered body (rare earth sintered magnet) obtained by compression molding rare earth alloy powder, and further, based on the evaluation method. The present invention relates to a rare earth sintered magnet and its manufacturing method.

  Rare earth sintered magnets, for example, Nd-Fe-B based sintered magnets have advantages such as excellent magnetic properties, Nd as a main component is abundant in resources, and is relatively inexpensive. In recent years, the demand has been increasing.

  As a method for producing a rare earth sintered magnet, a powder metallurgy method is known and widely used because it can be produced at low cost. In the powder metallurgy method, first, a raw material alloy ingot is roughly pulverized and finely pulverized to obtain a rare earth alloy powder having a particle size of about several μm. The rare earth alloy powder thus obtained is compression-molded with an orientation magnetic field applied to obtain a molded body in which the rare earth alloy powder is oriented in a predetermined direction. Thereafter, the compact is sintered in vacuum or in an inert gas atmosphere, and further subjected to an aging treatment.

  In the rare earth sintered magnet described above, it is known that the degree of orientation of the rare earth alloy powder has a great effect on the characteristics, and it is desired to make the degree of orientation as high as possible when manufacturing the rare earth sintered magnet. . From such a viewpoint, various techniques for improving the degree of orientation of the rare earth sintered magnet have been proposed (see, for example, Patent Document 1 and Patent Document 2).

For example, in Patent Document 1, in order to improve the degree of orientation, initial orientation (orientation at the time of molding) is important, and an additive that suppresses magnetic aggregation, such as mineral oil, is added, and 0.15 to 0.5 ton. It has been proposed to improve the degree of orientation of the magnet by molding at / cm ³ . When X-ray diffraction (using a Cu target) is performed, the X-ray diffraction intensity ratio between the (006) plane and the (105) plane in the R ₂ Fe ₁₄ B intermetallic compound: I (006) / I (105) is The orientation degree (Br / Ms) defined by the ratio of the residual magnetic flux density Br measured at 24 ° C. and the saturation magnetization Ms is 95% or more, and the maximum energy product (BH) max is 48. A rare earth sintered magnet of 7 MGOe or more is disclosed.

On the other hand, in Patent Document 2, it is proposed to improve the degree of orientation by defining the saturation magnetization of the surface portion constituting the cavity space and the packing density in the cavity. Specifically, in the molding process of manufacturing an anisotropic sintered magnet, at least the surface portion of the die member composed of a die, an upper punch, and a lower punch has a saturation magnetization 4πIs of 500 to 12,000 Gauss. And the saturation magnetization 4πIs value is Mp, the magnetization value of the molded permanent magnet powder is Mm, the density is Dm, the filling density into the cavity of the permanent magnet powder is Dc, and pressurization Satisfying the relationship of 0.7 × Mm × Dc / Dm <Mp <1.3 × Mm × Dr / Dm, where Dr is the molding density when rotation of the permanent magnet powder due to the orientation magnetic field does not occur due to the progress of As a metal material having magnetism, a permanent magnet is supplied into a cavity of a die composed of the die, upper punch, and lower punch, and a magnetic field is applied to orient the easy magnetization direction of the permanent magnet powder. And, it is disclosed that further compresses.
Japanese Patent No. 3209380 Japanese Patent No. 3526493

  However, in the techniques described in these patent documents, only a partial orientation degree is evaluated, and for example, no consideration is given to the orientation degree distribution of the entire rare earth sintered magnet. As a result, a rare earth sintered magnet having sufficient characteristics is not always realized when viewed as a whole of the rare earth sintered magnet.

  The present invention has been proposed in view of such a conventional situation, and firstly, regarding a molded body obtained by molding a rare earth alloy powder and a rare earth sintered magnet obtained by sintering the molded body, It is an object of the present invention to provide an orientation degree evaluation method capable of accurately evaluating the orientation degree in a proper region. Secondly, a rare earth sintered magnet having a high overall orientation degree and excellent magnetizing characteristics, for example, even in the case of a thin shape, can be selected by appropriately selecting based on the orientation degree evaluation method. The purpose is to provide. Third, the degree of orientation is not partially improved, but the overall degree of orientation can be increased, and a rare earth sintered magnet having a high degree of orientation can be obtained in a macro region, and more efficiently. Another object of the present invention is to provide a method for producing a rare earth sintered magnet capable of using raw materials.

  In order to achieve the above-mentioned object, the orientation degree evaluation method of the present invention is to equally divide a molded body in which a rare earth alloy powder is compression-molded or a sintered body thereof into odd-numbered parts, and to divide the central piece and the outermost part. After performing X-ray diffraction on the divided pieces, the degree of orientation of each divided piece is calculated by the Lotgering method to evaluate the variation in the degree of orientation.

  The rare earth sintered magnet of the present invention is a rare earth sintered magnet made of a sintered body of rare earth alloy powder, and among the divided pieces equally divided into an odd number, the divided piece in the central portion and the outermost divided piece The piece is characterized in that, after vector correction of the X-ray diffraction intensity of each diffraction peak, the difference in orientation degree calculated by the Lotgering method is 1.5% or less.

  Furthermore, the method for producing a rare earth sintered magnet according to the present invention includes compression molding of rare earth alloy powder to form a molded body having a predetermined shape, and sintering the molded body to form a rare earth sintered magnet. An orientation magnetic field is applied in a predetermined direction, and both end portions in the orientation magnetic field direction are cut off.

Evaluation of rare earth sintered magnets by X-ray diffraction is also performed, for example, in Patent Document 1. However, in the invention described in Patent Document 1, evaluation is performed by determining the X-ray diffraction intensity ratio between the (006) plane and the (105) plane in the R ₂ Fe ₁₄ B intermetallic compound, and any measurement is performed. In that respect, it is merely looking at the degree of orientation in a microscopic region.

  In the orientation degree evaluation method of the present invention, the degree of orientation is calculated by the rod-gering method for each of the odd-numbered divided pieces, the central piece and the outermost divided piece, and these are compared. Therefore, the distribution of the degree of orientation in the macro region of the compact or sintered body (rare earth sintered magnet), that is, the entire compact or sintered body is grasped, and its quality is judged.

  When calculating the degree of orientation by the Lotgering method, the accuracy is dramatically increased by performing vector correction on the X-ray diffraction intensity of each diffraction peak. In the calculation in the rod-gering method, only the orientation direction, that is, (001) reflection component is integrated, and the X-ray diffraction intensity in a direction different from this is determined to be the vertical direction, that is, (hk0) reflection component. Is done. Therefore, the degree of orientation calculated compared to the actual degree of orientation is a considerably small value. On the other hand, vector correction is performed on the X-ray diffraction intensity of each diffraction peak, and for the X-ray diffraction intensity different from (001) reflection, the (00l) reflection component and the (hk0) reflection component orthogonal thereto. If the separated (00l) reflection components are added to each other, accurate evaluation in accordance with the actual degree of orientation can be performed. This is defined in the invention according to claim 2 of the present invention. In the orientation degree evaluation method, vector correction is performed on the X-ray diffraction intensity of each diffraction peak, and each of the Lotgering methods is performed based on the correction value. The variation of the orientation degree is evaluated by calculating the orientation degree of the divided pieces.

  On the other hand, as described above, the degree of orientation is calculated by the rod-gering method for the split piece in the central portion and the outermost split piece, and the distribution of the orientation degree of the entire rare earth sintered magnet is grasped by comparing this. . Therefore, by selecting a rare earth sintered magnet based on the distribution of the degree of orientation, a rare earth sintered magnet with excellent magnetization can be realized. The rare earth sintered magnet of the present invention is selected based on such a viewpoint. In particular, as described above, the degree of orientation calculated by the Lotgering method based on the vector-corrected X-ray diffraction intensity is used. When the difference is 1.5% or less, for example, in a rare-earth sintered magnet having a thin shape, variation in residual magnetic flux density Br is suppressed to about 100 G or less. Moreover, since the variation in the degree of orientation is small, the magnetization is good, and thereby the high characteristics of the material (rare earth alloy powder) are fully utilized.

  For example, rare earth sintered magnets having excellent orientation degree distribution as described above, such as a difference in orientation degree of 1.5% or less between the central portion and the outer peripheral portion, can be obtained by simply using rare earth alloy powders in the orientation magnetic field. It is difficult to obtain even by molding in a magnetic field while applying. Therefore, in the production method of the present invention, as described above, both end portions in the orientation magnetic field direction are cut off in a molded body formed by applying an orientation magnetic field in a predetermined direction or a sintered body obtained by sintering the same.

  For example, Patent Document 2 discloses that a mold member is made of a magnetic metal material, thereby eliminating disturbance in the direction of magnetic flux inside the molded body and making the direction of magnetic flux parallel. However, even if the direction of the magnetic flux is made parallel as much as possible by the above method, there is always an interface of different materials in the part where the magnetic flux enters the molded body or the part where the magnetic flux comes out of the molded body. Is difficult to completely eliminate.

  In the present invention, since both end portions in the orientation magnetic field direction corresponding to the interface portion are cut off, a slight decrease in the degree of orientation is also eliminated, and calculation is performed by the Lotgering method based on the vector-corrected X-ray diffraction intensity. A rare earth sintered magnet having a very small difference in orientation and a good overall orientation is produced, such that the difference in orientation is 1.5% or less. Note that the cut molded body or sintered body can be reused if pulverized and mixed with the rare earth alloy powder, which is a raw material, so that the raw material is not consumed wastefully and efficient use of the raw material is realized. .

  According to the method for evaluating the degree of orientation of the present invention, a molded body obtained by molding a rare earth alloy powder and a rare earth sintered magnet obtained by sintering the molded body are in a macro region, for example, a thin molded body or a rare earth sintered magnet. It is possible to accurately evaluate the entire orientation degree distribution.

  On the other hand, the rare earth sintered magnet of the present invention is strictly selected based on the above-mentioned orientation degree evaluation method. For example, even in the case of a thin shape, the whole orientation degree is high, so that the rare earth sintered magnet has excellent magnetizing characteristics. It is possible to realize a rare earth sintered magnet that takes full advantage of the high properties of the alloy powder.

  Furthermore, according to the method of manufacturing a rare earth sintered magnet of the present invention, since the end portion where the disturbance of the orientation magnetic field due to the interface of the different materials occurs is removed, the degree of orientation is improved over the whole. A rare earth sintered magnet can be obtained. Moreover, about the cut-out molded object and sintered body, it is possible to utilize a raw material efficiently by reusing this.

  Hereinafter, an orientation degree evaluation method, a rare earth sintered magnet and a manufacturing method thereof to which the present invention is applied will be described in detail.

  The orientation degree evaluation method of the present invention is applied to a compact formed by compression molding rare earth alloy powder and a rare earth sintered magnet obtained by sintering the compact. For example, by applying to a molded body, useless sintering can be suppressed, and a molded body that does not satisfy the standard can be easily reused. Moreover, strict quality control becomes possible by applying to rare earth sintered magnets.

  The shape of the molded object or rare earth sintered magnet to be evaluated is arbitrary. For example, the shape of the long side is larger than the thickness of the molded object or rare earth sintered magnet, such as a thin shape or a long shape. Applying it has a great effect. This is because in the case of the thin shape or the long shape, the degree of orientation tends to be different between the central portion and the outermost portion. FIG. 1 schematically shows a thin rectangular plate-shaped molded body (sintered body). Specifically, when the thickness is c and the length of the long side is a, a When the shape is such that / c ≧ 10, it is preferably applied to the orientation degree evaluation method of the present invention.

  The degree of orientation is measured by dividing the sample (the compact or the rare earth sintered magnet) into an odd number and dividing the central portion and the outermost portion. The number to be divided may be determined according to the size of the sample, and is at least three. In the case of a rectangular flat plate shape as shown in FIG. 1, each of the divided pieces 1 to 9 is divided into three parts in the vertical and horizontal directions, and the divided piece 5 in the central portion and the outermost divided pieces (1, 3, 7). , 9 or more). The dividing method is not limited to this, and it is also possible to set the vertical and horizontal divisions to 3 or more, for example, 5 divisions and 25 divisions in total, 7 divisions and 49 divisions, respectively. In any case, the measurement may be performed on one of the split piece at the central portion and the split piece at the outermost portion (outer peripheral corner), and these may be compared. In addition, about the outermost division | segmentation piece, what is necessary is just to measure at least 1 and does not prevent further measurement. For example, the measurement may be performed on four corner pieces for comparison with the middle piece. Further, for example, in the case of a long shaped body or a rare earth sintered magnet, it is not always necessary to divide each longitudinally and laterally, for example, equally divided in the long side direction, about the divided piece of the central portion and the divided piece of the end portion Measurement may be performed.

  In order to measure the degree of orientation, first, the surface of each divided piece is mirror-polished, then X-ray diffraction is performed, and the degree of orientation is calculated by the Lotgering method based on the obtained diffraction peak. In the Lotgering method, based on the X-ray diffraction intensity I (00l) of the (00l) reflection component and the X-ray diffraction intensity I (hk0) of the (hk0) reflection component, the degree of orientation fc is calculated by the following equation (1). be able to.

  When the degree of orientation is calculated by the Lotgering method, only the orientation direction, that is, (001) reflection component is integrated, and a diffraction peak that deviates even slightly from this is perpendicular to this, that is, (hk0) reflection component. It is judged and excluded from the molecular side in the formula 1. Therefore, the degree of orientation calculated compared to the actual degree of orientation is a considerably small value. In order to avoid this and calculate the degree of orientation according to the actual condition, it is preferable to perform vector correction on the diffraction peak.

  Vector correction makes it possible to calculate the degree of orientation in line with actuality. For a diffraction peak different from (00l) reflection, the (00l) reflection component is orthogonal to the (hk0) reflection component. The separated components in the (00l) direction are added to the numerator side in Equation 1. When the plane orientation of a crystal plane is different from the (00l) plane, the diffraction peak corresponding to the plane orientation is multiplied by cos θ based on the tilt angle θ to calculate the (00l) reflection component. In Equation 1, this value is integrated on the molecular side as a component of (00l) reflection, and the degree of orientation fc is obtained.

  For example, in the X-ray diffraction chart shown in FIG. 2, a diffraction peak indicated by an arrow is a diffraction peak on the (105) plane. Although this diffraction peak is relatively large and has an orientation close to the (001) plane, it is calculated as a vertical component in the normal Lotgering method. On the other hand, in the case of vector correction, the inclination angle formed by the (00l) plane and the (105) plane is obtained from Table 1 (15.5 degrees), and the diffraction intensity is calculated when calculating the orientation degree by the Lotgering method. Is multiplied by cos 15.5 ° and added to the molecule.

Table 1 shows the inclination angle θ between the (00l) plane and other observed planes. In the case of an NdFeB-based rare earth sintered magnet, the inclination angle θ is determined by the lattice constant and crystal structure of Nd ₂ Fe ₁₄ B [eg, Herbst, J et al. Phys. Rev. B: Condens. Matter, 29 4176 (1984 )] Can be obtained by calculating the angle formed between the surfaces.

  The vector correction is performed on the X-ray diffraction intensity of each diffraction peak based on the tilt angle θ described in Table 1, and the degree of orientation is calculated by the Lotgering method based on the corrected result. Accurate evaluation according to the degree of orientation is performed.

  The in-plane distribution of the orientation degree of the sample (molded body or rare earth sintered magnet) can be grasped by measuring the orientation degree of each divided piece as described above and comparing them. Therefore, by strictly selecting compacts and rare earth sintered magnets based on the in-plane distribution of the degree of orientation, it is possible to reliably realize compacts and rare earth sintered magnets with excellent characteristics and little variation in characteristics. It is considered possible. Therefore, in the following, application of the orientation degree evaluation method to a rare earth sintered magnet will be described.

  First, the rare earth sintered magnet will be described. The rare earth sintered magnet referred to in the present invention is mainly composed of a rare earth element, a transition metal element, and boron. What is necessary is just to select a magnet composition arbitrarily according to the objective. For example, R-T-B (R is a concept including one or more rare earth elements, where the rare earth element includes Y. T is one or two of transition metal elements essentially including Fe or Fe and Co. More than seeds. B is boron.) When a rare earth sintered magnet having excellent magnetic properties is obtained, a rare earth element R is 20 to 20 in the magnet composition after sintering. It is preferable that the composition be 40 mass%, boron B is 0.5 to 4.5 mass%, and the balance is the transition metal element T. Here, R is a rare earth element, that is, one or more selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. Especially, since Nd is abundant in resources and relatively inexpensive, the main component is preferably Nd. Further, the inclusion of Dy and Tb is effective in improving the coercive force Hcj because it increases the anisotropic magnetic field.

  Further, an additive element M can be added to form an R-T-B-M rare earth sintered magnet. In this case, examples of the additive element M include Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, and Ga. A seed | species or 2 or more types can be selected and added. The addition amount of these additive elements M is preferably 3% by mass or less in consideration of magnetic characteristics such as residual magnetic flux density. If the amount of additive element M added is too large, the magnetic properties may be deteriorated.

  Of course, it is needless to say that the present invention is not limited to these compositions, and can be applied to all known compositions as rare earth sintered magnets.

  Next, the manufacturing method of the above-mentioned rare earth sintered magnet will be described. To manufacture the rare earth sintered magnet, a powder metallurgy method is adopted. The manufacturing process by the powder metallurgy method basically includes an alloying step, a coarse pulverization step, a fine pulverization step, a magnetic field forming step, a sintering / aging step, a processing step, and a surface treatment step. In order to prevent oxidation, most of the steps after sintering are performed in a vacuum or in an inert gas atmosphere (in a nitrogen atmosphere, an Ar atmosphere, etc.).

  In the alloying process, a metal or alloy as a raw material is blended according to the magnet composition, melted in a vacuum or an inert gas, for example, Ar atmosphere, and cast into an alloy. As a casting method, a strip casting method (continuous casting method) in which molten high-temperature liquid metal is supplied onto a rotating roll and an alloy thin plate is continuously cast is preferable from the viewpoint of productivity and the like. It is not limited to that. As the raw material metal (alloy), pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof can be used.

  A single alloy having an almost final magnet composition may be used as the alloy, or a plurality of types of alloys having different compositions may be mixed so that the final magnet composition is obtained. Mixing may be performed in any process of alloy, raw material coarse powder, and raw material fine powder, but mixing with an alloy is desirable from the viewpoint of mixing properties.

  In the coarse pulverization step, the previously cast raw alloy thin plate, ingot, or the like is pulverized until the particle size is about several hundred μm. As the pulverizing means, a stamp mill, a jaw crusher, a brown mill, or the like can be used. In order to improve the coarse pulverization property, it is effective to perform coarse pulverization after occlusion of hydrogen.

  The coarse pulverization step can be constituted by a plurality of steps in which a plurality of pulverization means are combined. For example, the coarse pulverization step can be made into two steps, a hydrogen pulverization step and a mechanical coarse pulverization step. The hydrogen pulverization step is a step in which hydrogen is occluded in the cast raw material alloy and pulverized in a self-destructive manner utilizing the fact that the hydrogen occlusion amount varies depending on the phase. Thereby, it can grind | pulverize to the magnitude | size about particle size several mm. The mechanical coarse pulverization step is a step of pulverizing using a mechanical method such as a brown mill as described above. The raw alloy powder pulverized to a size of about several millimeters by the hydrogen pulverization step is used. Then, pulverize until the particle size is about several hundred μm. When performing the hydrogen pulverization step, the mechanical coarse pulverization step may be omitted.

  After the coarse pulverization step is completed, a pulverization aid is usually added to the coarsely pulverized raw material alloy powder. As the grinding aid, for example, a fatty acid compound or the like can be used. In particular, by using a fatty acid amide as the grinding aid, a rare earth sintered magnet having good magnetic properties can be obtained. The addition amount of the grinding aid is preferably 0.03 to 0.4% by mass. When the grinding aid is added within this range, the amount of residual carbon after sintering can be reduced, which is effective in improving the magnetic properties of the rare earth sintered magnet.

  After the coarse pulverization step, a fine pulverization step is performed. This fine pulverization step is performed using, for example, a jet mill. The conditions for fine pulverization may be appropriately set according to the airflow pulverizer to be used, and the raw material alloy powder is finely pulverized until the average particle size becomes about 1 to 10 μm, for example, 3 to 6 μm. A jet mill opens a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, accelerates powder particles by this high-speed gas flow, and collides powder particles with each other. Or it is a method of generating a collision with a target or a container wall and crushing. Jet mills are generally classified into jet mills that use fluidized beds, jet mills that use vortex flow, jet mills that use impingement plates, and the like.

  After the pulverization step, the raw material alloy fine powder (rare earth alloy powder) is formed in the magnetic field in the magnetic field forming step. Specifically, the raw material alloy fine powder obtained in the fine pulverization step is filled in a mold in which an electromagnet is arranged, and is molded in a magnetic field in a state where crystal axes are oriented by applying a magnetic field. Forming in the magnetic field may be either longitudinal magnetic field shaping or transverse magnetic field shaping. The forming in the magnetic field may be performed at a pressure of about 30 to 300 MPa in a magnetic field of 800 to 1500 kA / m, for example.

  Next, in the sintering / aging process, sintering and aging treatment are performed. That is, after forming the raw material alloy fine powder in a magnetic field, the compact is sintered in a vacuum or an inert gas atmosphere. The sintering temperature needs to be adjusted according to various conditions such as composition, pulverization method, difference in particle size and particle size distribution, etc. For example, sintering may be performed at 1000 to 1150 ° C. for about 5 hours, and rapid cooling after sintering. Is preferred. After sintering, the obtained sintered body is preferably subjected to aging treatment. This aging treatment is an important step in controlling the coercive force Hcj of the obtained rare earth sintered magnet. For example, the aging treatment is performed in an inert gas atmosphere or in a vacuum. As the aging treatment, a two-stage aging treatment is preferable, and in the first aging treatment step, the temperature is maintained at a temperature of about 800 ° C. for 1 to 3 hours. Next, a first quenching step is provided for quenching to room temperature to 200 ° C. In the second stage aging treatment step, the temperature is maintained at about 550 ° C. for 1 to 3 hours. Next, a second quenching step for quenching to room temperature is provided. Since the coercive force Hcj is greatly increased by heat treatment at around 600 ° C., when aging treatment is performed in a single stage, it is advisable to perform aging treatment at around 600 ° C.

  After the sintering / aging step, a processing step and a surface treatment step are performed. The processing step is a step of mechanically forming into a desired shape. A surface treatment process is a process performed in order to suppress the oxidation of the obtained rare earth sintered magnet, for example, forms a plating film and a resin film on the surface of a rare earth sintered magnet.

  The above is the manufacturing process of the rare earth sintered magnet. In the present invention, after the molding step or after the sintering / aging step, both end portions in the orientation magnetic field direction of the obtained molded body and sintered body are cut off. Only the portion where the in-plane distribution of the degree of orientation is small is used as a product. Both end portions in the orientation magnetic field direction have a large in-plane distribution of the degree of orientation, and by cutting this portion, the difference in the degree of orientation of the compact or sintered body can be made extremely small. It should be noted that when the both end portions are excised, it is usually sufficient to excise an area of about 2 mm from the end portion. However, by measuring the orientation degree, a difference in orientation degree between the central portion and the outer peripheral portion is predetermined. You may make it excise until it becomes confirmed that it becomes below a value.

  The excised both end portions can be reused by adding to the above-described coarse pulverization step or the like. For example, when excised at the stage of the molded body, there is almost no problem even if it is reused as it is. Even when the sintered body is cut and then cut off, there is almost no problem as long as it is before the surface treatment step, and if it is crushed and added to the raw material in a small amount, there will be no problem in terms of characteristics. By reusing the excised ends, the raw material is not wasted and the raw material cost can be reduced.

  The rare earth sintered magnet produced by cutting off both end portions as described above, for example, even when it has a thin shape (the ratio a / c of the long side a to the thickness c is 10 or more), the degree of orientation in the plane The distribution of is small. Specifically, the degree of orientation calculated by the Lotgering method based on the vector-corrected X-ray diffraction intensity in the middle part and the outermost part among the oddly divided pieces. Is less than 1.5%.

  If the degree of orientation difference is 1.5% as described above, the magnetization of the entire magnet will be good, and the high performance of the material (rare earth alloy powder) can be fully utilized. A sintered magnet can be realized. The rare earth sintered magnet exhibits excellent characteristics when used in, for example, a motor or the like, and can realize high performance of the motor.

  Next, specific examples of the present invention will be described based on experimental results.

The composition of the example raw material alloy was Nd 19.5 mass%, Pr 5.4 mass%, Dy 5.1 mass%, Co 2.0 mass%, Al 0.01 mass%, Cu 0.13 mass%, B 1.0 mass%, The balance was Fe. A raw material metal or alloy was blended so as to have the above composition, and a raw material alloy thin plate was melted and cast by a strip casting method.

  Next, the obtained raw material alloy coarse powder was subjected to a pulverization step. That is, after the obtained raw material alloy thin plate was hydrogen pulverized, mechanical coarse pulverization was performed with a brown mill to obtain raw material alloy coarse powder. To this raw material alloy coarse powder, 0.10% by mass of zinc stearate as an organic substance serving as a grinding aid is added, and an average particle diameter (D50) = 4.6 μm is obtained in a high-pressure nitrogen gas atmosphere using a jet mill. Were pulverized into rare earth alloy powders.

  The obtained rare earth alloy powder was molded into a shape of 59.7 mm × 33.9 mm × 63.8 mm. In molding, a mold made of a magnetic material was used, and molding was performed while applying a predetermined orientation magnetic field. After sintering and aging the obtained molded body, it was cut using an inner slicer, and a 47.0 mm × 24.0 mm × 2.0 mm thin sintered body (rare earth sintered magnet) 17 sheets were obtained. At the time of the cutting, both end portions in the orientation magnetic field direction of the sintered body were cut by 1 mm. The cut sintered body was returned to the pulverization step and reused by adding to the raw material alloy coarse powder.

The mold used in the comparative example was a non-magnetic mold, and after sintering and aging, the inner peripheral slicer was used without cutting off both ends of the sintered body. A rare earth sintered magnet was obtained. In the case of this comparative example, since both end portions of the sintered body were not cut, 18 thin sintered bodies (rare earth sintered magnets) of 47.0 mm × 24.0 mm × 2.0 mm were obtained.

Evaluation of degree of orientation The rare earth sintered magnets obtained in the examples and comparative examples were subjected to X-ray diffraction measurement to calculate the degree of orientation. As an object to be measured, in the examples and comparative examples, the sintered body at the outermost part was selected from the sintered bodies cut with the inner circumferential slacer, and the degree of orientation was evaluated. Further, as shown in FIG. 1, the rare earth sintered magnet was divided into 3 parts in length and breadth, a total of 9 parts, and the degree of orientation was calculated for the divided piece 5 at the central portion and the divided piece 1 at the outer peripheral corner.

  In the X-ray diffraction measurement, the surface of each divided piece in the magnetic field orientation direction was mirror-polished with abrasive paper, and then etched with a 3% nitric acid ethanol solution for 3 minutes. X-ray diffraction measurement was performed by a θ-2θ method using a Cu tube and an output of 1.8 kW. The orientation degree was calculated from the obtained measurement value by the Lotgering method, the X-ray diffraction intensity of each diffraction peak was vector-corrected, and the orientation degree was calculated by the Lotgering method based on the correction value.

  Table 2 shows the calculation results for the rare earth sintered magnet of the example, and Table 3 shows the calculation results for the rare earth sintered magnet of the comparative example. For the measurement position in the table, point 1 is the calculation result for the segment piece 1 at the outer peripheral corner, and point 5 is the calculation result for the segment piece 5 at the central portion.

  As is apparent from Table 2, the rare earth sintered magnets of the examples have a very small difference in orientation degree regardless of whether or not vector correction is performed. Especially when the vector correction is performed, the difference in orientation degree is 1.5% or less. It has become. On the other hand, in the case of the rare earth sintered magnet of the comparative example, the difference in orientation degree is 1.5% or less without vector correction, but the difference in orientation degree is 1.5% with vector correction. % Is over. From this, in the rare earth sintered magnet of the comparative example, a decrease in the effective orientation degree is observed, and this is presumed to lead to a decrease in the magnet performance. Actually, when the amount of flux was measured by changing the magnetizing magnetic field, it was confirmed that the rise of the flux was quick in the rare earth sintered magnet of the example. Therefore, it can be seen that the evaluation based on the actual performance can be performed by performing vector correction when calculating the degree of orientation.

  FIG. 3 shows the relationship between the degree of orientation and the residual magnetic flux density. (A) shows the case without vector correction, and (b) shows the case with vector correction. By performing vector correction, there is a good correlation between the degree of orientation and the residual magnetic flux density Br.

It is a schematic diagram which shows the example of a division | segmentation of a thin-shaped sample. It is a figure which shows an example of the X-ray-diffraction chart of a NdFeB type rare earth sintered magnet. It is a characteristic view which shows the relationship between an orientation degree and a residual magnetic flux density, (a) is a case without vector correction, (b) is a case with vector correction.

Claims (13)

After the molded body in which the rare earth alloy powder is compression-molded or its sintered body is equally divided into an odd number, and after performing X-ray diffraction on the central part and the outermost part,
An orientation degree evaluation method characterized in that the degree of orientation of each divided piece is calculated by the Lotgering method to evaluate the variation in orientation degree.   2. The variation in orientation degree is evaluated by performing vector correction on the X-ray diffraction intensity of each diffraction peak and calculating the degree of orientation of each divided piece by the Lotgering method based on the correction value. Orientation degree evaluation method.   The orientation degree evaluation method according to claim 1 or 2, wherein the molded body or the sintered body has a thin shape in which a ratio a / c of a long side a to a thickness c is 10 or more.   The orientation according to claim 3, wherein the molded body or the sintered body is divided into 9 parts in a total of 9 parts in length and breadth, and the degree of orientation is compared with respect to at least one of a central piece and a corner piece. Degree evaluation method. A rare earth sintered magnet comprising a sintered body of rare earth alloy powder,
Among the odd-numbered pieces, the difference in orientation calculated by the Lotgering method after vector correction of the X-ray diffraction intensity of each diffraction peak in the central piece and the outermost piece. Rare earth sintered magnet, characterized in that is 1.5% or less.   6. The rare earth sintered magnet according to claim 5, wherein the ratio a / c between the long side a and the thickness c is 10 or more.   7. The vertical and horizontal divisions, a total of 9 divisions, and the difference in the degree of orientation is 1.5% or less for at least one of the central division piece and the division piece at the outer peripheral corner. Rare earth sintered magnet.   The rare earth alloy powder is R (R is one or more of rare earth elements), T (T is one or more transition metal elements essential for Fe, Fe, or Co). ) And B. The rare earth sintered magnet according to claim 5, wherein the rare earth sintered magnet is included. When a rare earth alloy powder is compression-molded into a molded body having a predetermined shape, and the molded body is sintered into a rare-earth sintered magnet,
A method for producing a rare earth sintered magnet, wherein an orientation magnetic field is applied in a predetermined direction during the molding, and both end portions in the orientation magnetic field direction are excised.   The method for producing a rare earth sintered magnet according to claim 9, wherein the both end portions are cut out by 2 mm or more from the end portions.   The method for producing a rare earth sintered magnet according to claim 9 or 10, wherein the both end portions are excised at the stage of a molded body.   The method of manufacturing a rare earth sintered magnet according to claim 9 or 10, wherein the both end portions are cut after being formed into a sintered body.   The method for producing a rare earth sintered magnet according to any one of claims 9 to 12, wherein the cut off both end portions are crushed and reused.

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