JP3937126B2 - Die for sintered magnet and method for producing sintered magnet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a die used for manufacturing a sintered magnet and a method for manufacturing an anisotropic sintered magnet.
[0002]
[Prior art]
Ferrite magnets such as Ba ferrite and Sr ferrite, and rare earth magnets such as R—Co and R—Fe—B (R: rare earth metals including Sc and Y) are widely used as anisotropic sintered magnets. In recent years, however, the use of rare earth magnets as high performance magnets has been rapidly increasing. In these anisotropic sintered magnets, the direction of easy magnetization of each crystal grain carrying magnetism is aligned in a certain direction, and therefore, the direction of easy magnetization of crystal grains is in a different direction, etc. Compared to the isotropic magnet, the value of the residual magnetic flux density is large when magnetized in the easy magnetization direction, and therefore the maximum energy product can be increased. Moreover, since it is a sintered magnet, the amount of non-magnetic substance is small compared to a bonded magnet bonded with resin or the like, so that the value of residual magnetic flux density is increased, and the maximum energy product can be increased. Therefore, anisotropic sintered magnets are widely used because they can obtain the largest maximum energy product among magnets using the same material.
[0003]
Anisotropic sintered magnets pulverize the material until each pulverized powder becomes a single crystal and apply an external magnetic field to the pulverized powder in order to align the direction of easy magnetization of magnetic crystal grains in a certain direction. By doing so, the magnetization easy axis of the magnet powder is aligned in a direction parallel to the direction of the external magnetic field, and compression is performed by applying pressure. Thereafter, the molded magnet powder is sintered under a predetermined condition to produce an anisotropic sintered magnet. Depending on the material, heat treatment may be required after sintering. For example, R₂Co₁₇In the system magnet, after sintering, solution treatment is performed, and further aging treatment is performed. R-Fe-B magnets are manufactured by performing heat treatment at around 500 ° C. after sintering.
[0004]
The magnetic field press used in the molding process includes a die, an upper punch, a lower punch, and a magnetic field generating means. Magnet powder is supplied into a cavity composed of a die, an upper punch and a lower punch, and an orientation magnetic field is applied by a magnetic field generating means to align the easy magnetization direction of the magnet powder in one direction, and pressure is applied by an upper punch and a lower punch. To form magnet powder in the cavity. Molding is generally performed by applying a static magnetic field with an electromagnet, etc., and applying the static magnetic field, but the size of the magnetic field that can be obtained is limited by the static magnetic field with an electromagnet. When it is desired to perform this, a pulsed magnetic field by an air-core coil may be used as the magnetic field generating means. When a pulse magnetic field is used, magnet powder is supplied into the cavity, a pulse magnetic field is applied, and then molding is performed. However, when a pulse magnetic field is generated, problems such as generation of heat of the coil are significant, which is not preferable as a production method. In the direction of applying an orientation magnetic field to the magnet powder filled in the cavity, the vertical magnetic field forming in which the magnetic field is applied in a direction parallel to the direction of pressure application by the upper and lower punches, and the horizontal direction in which the magnetic field is applied in a direction perpendicular to the direction of pressure application. There is magnetic field shaping. Whether to select transverse magnetic field shaping or longitudinal magnetic field shaping is determined by the material to be produced, characteristics, shape, magnetization direction, etc., but sintered magnets produced by longitudinal magnetic field shaping are Since magnetic characteristics are deteriorated as compared with the case, transverse magnetic field shaping is often used.
[0005]
[Problems to be solved by the invention]
By the way, when a magnet is manufactured by applying a magnetic field to form and sinter, the magnetic characteristics may vary depending on each part of one sintered body. In particular, the surface of the sintered magnet is remarkably deteriorated in the residual magnetic flux density as compared with the central portion, which is considered to be due to a large disorder of orientation on the surface. As described above, when the orientation is disturbed near the surface and the residual magnetic flux density is deteriorated, the residual magnetic flux density is lowered as a whole of the sintered body. Such a phenomenon appears particularly remarkably when the size of the sintered body is small. Particularly in recent years, electronic and electrical equipment using anisotropic sintered magnets have become smaller, and the size of anisotropic sintered magnets has become smaller and thinner, resulting in deterioration of magnetic properties due to disorder of orientation. Is becoming impossible to ignore. Furthermore, when manufacturing a small magnet, it may be manufactured by cutting a large sintered body block, but the magnet cut out from near the surface often has a low residual magnetic flux density and cannot withstand use. This is causing a decrease in yield.
[0006]
As a means for solving the above problems, it has been found that it is effective to use a metal material having magnetism for all or at least a part of the die members of the die, the upper punch, and the lower punch. (Unexamined-Japanese-Patent No. 9-45568, Unexamined-Japanese-Patent No. 9-35977).
[0007]
Japanese Patent Application Laid-Open No. 9-45568 prevents the appearance of magnetic poles on the surface of the molded body by using all or at least a part of the die, upper punch and lower punch mold members as magnetic metal materials. Thus, the distribution of the magnetic flux in the cavity space is made uniform, and the direction of the magnetic flux is made as parallel as possible.
[0008]
As a result, the orientation of the anisotropic sintered magnet, particularly the orientation near the surface of the sintered body block, is remarkably improved, thereby significantly increasing the residual magnetic flux density of the magnet, and from the large block. The magnet manufacturing yield by cutting was also greatly improved.
[0009]
However, especially when a magnetic metal material is used for the die, since the magnetization remains in the die, the magnetic field is formed once, and then the obtained compact is taken out of the die and the magnet is used for the next forming. When supplying powder into the cavity, problems such as magnet powder adhering to the die are likely to occur. When such a situation occurs, it becomes difficult to uniformly fill the magnet powder in the cavity, and unevenness in the filling density is likely to occur. Therefore, the density of the molded body after molding can also be uneven, and if the sintering is performed as it is, the smaller portion of the molded body has a larger shrinkage due to sintering compared to the portion with a higher molded body density. The shape of the sintered body became distorted, resulting in a decrease in yield. In order to prevent this, it was necessary to manufacture a permanent magnet larger than the designed magnet shape and process it to a predetermined shape, so that the processing cost was large and the material yield was reduced. There was a need for improvement. Further, if the magnetic powder adheres to the die, the efficiency of the molding operation may be significantly deteriorated.
[0010]
In order to solve this problem, Japanese Patent Laid-Open No. 9-35977 discloses that the saturation magnetization 4πIs of a metal material having magnetism used as a die material is 500 to 12,000 gauss, and the die at the time of supplying permanent magnet powder into the cavity is used. The above problem was solved by limiting the magnetization 4πI to 6000 Gauss or less.
[0011]
However, due to the high performance of electronic equipment, recently, there has been a demand for providing an anisotropic sintered magnet with less disorder of orientation.
[0012]
Accordingly, an object of the present invention is to provide a die and a method for producing a sintered magnet that can form an anisotropic sintered magnet having a large residual magnetic flux density and little orientation disorder.
[0013]
Means for Solving the Problem and Embodiment of the Invention
As a result of diligent efforts to solve the above problems, the present inventors have completed the present invention. The gist of the present invention is that a saturation magnetization of 4πIs is used as a die in the forming process of anisotropic sintered magnet production. An H-shaped die formed of a metal material having magnetism of 500 to 12,000 gauss and having a die shape viewed from above the cavity having a width in a direction perpendicular to the orientation magnetic field direction is smaller at the center than at both ends. The permanent magnet powder is supplied into the cavity of the die composed of the die, the upper punch and the lower punch, with the residual magnetization 4πI of the die at the time of supplying the permanent magnet powder being 6000 gauss or less, and the permanent magnet powder is easily magnetized. A method for producing an anisotropic sintered magnet, wherein a magnetic field for orienting a direction is applied and further compressed and molded, and in particular, the permanent magnet powder comprises R-Fe This is a method for producing an anisotropic sintered magnet which is a -B or R-Co rare earth permanent magnet powder.
[0014]
As described above, in the anisotropic magnet, the value of the residual magnetic flux density is increased by aligning the easy magnetization direction of the magnetic crystal grains constituting the magnet. This is related to the orientation of the anisotropic sintered magnet obtained in the above. During the molding process, the orientation magnetic field and the magnitude of the anisotropic magnetic field of the magnetic powder suppress the disorder of orientation due to the compression pressure, but the direction of the orientation magnetic field in the cavity space is neatly parallel. If not, the easy magnetization directions of the magnet powder are not aligned in parallel. For this reason, the magnetic field distribution in the cavity when the magnet powder of the anisotropic sintered magnet is oriented by the orientation magnetic field has a great influence on the alignment of the easy magnetization direction of the magnet powder.
[0015]
In general, when a uniform magnetic field is applied to a magnetic material, magnetic poles appear at both ends of the magnetic material, and the magnetic flux inside the magnetic material has a high magnetic flux density at the center of the magnetic material and the direction of the magnetic flux is uniform. In the peripheral part inside the body, the magnetic flux density is smaller than that in the central part, and the direction of the magnetic flux is not uniform. Particularly in the portion where the magnetic pole appears, such a decrease and non-uniformity of the magnetic flux density and a disturbance in the magnetic flux direction are remarkable. This is shown in FIG. In FIG. 5, 51 indicates a magnetic material, and 52 indicates a magnetic flux. Such a phenomenon also appears in the molded body when molding is performed in a static magnetic field, magnetic poles are generated on the surface of the molded body, and the magnetic field distribution inside the molded body is considered as shown in FIG. As described above, magnetic poles are generated on the surface of the molded body, and the magnetic field distribution inside the molded body is disturbed.
[0016]
According to Japanese Patent Laid-Open No. 9-35977, a die is made of a metallic material having a saturation magnetization of 4πIs of 500 to 12,000 gauss, and magnetic powder is supplied into the cavity space to form a magnetic field. It can be regarded as a magnetic material. Therefore, when an orientation magnetic field is applied, the magnetic pole appears on the surface of the die opposite to the surface in contact with the molded body of the magnetic metal material, and does not appear on the surface of the molded body. Therefore, the decrease and non-uniformity of the magnetic flux density in the vicinity of the magnetic pole and the disturbance in the magnetic flux direction are concentrated on the part of the metal material having the magnetism of the die, and the influence of the magnetic pole is mitigated in the part of the molded body. The direction is thought to be parallel.
[0017]
If the saturation magnetization of the die and the saturation magnetization of the magnet powder in the cavity are the same and the orientation magnetic field is a uniform parallel magnetic field, uniform and parallel orientation can be obtained in the cavity as described above. However, even if the saturation magnetization of the die can be matched with the saturation magnetization of the magnet powder in the cavity, it is necessary to enlarge the electromagnet in order to obtain a uniform orientation magnetic field, leading to an increase in the cost of the device and an increase in power consumption. .
[0018]
As a result of diligent efforts to obtain a uniform orientation magnetic field without increasing the size of the electromagnet, the width of the die shape viewed from above the cavity is perpendicular to the direction of the orientation magnetic field in the center than at both ends. Has been found to be smaller. And it discovered that the said objective could be achieved by shaping | molding by using this die | dye, and making the magnetization 4πI of the die | dye at the time of supply of the permanent magnet powder in a cavity into 6000 gauss or less, and came to make this invention. Is.
[0019]
  Therefore, the present inventionIn the molding process of manufacturing an anisotropic sintered magnet, a magnetic field for orienting the easy magnetization direction is applied to the permanent magnet powder, and the permanent magnet powder is further compressed by the upper punch and the lower punch to be molded. A magnet die,
The saturation magnetization 4πIs is formed from a metal material having magnetism of 500 to 12000 Gauss,Permanent magnet powder is suppliedCavity partFormed along the axial directionHollowsquareBlock shapeTo short axis quadrangular prismOf the die body formed onApplied from the lateral direction of the die bodyOrientation magnetic fieldApplication ofdirectionWith respect to the direction in which the orientation magnetic field is appliedRight angleIn the direction ofBothOutsideIn the center of each sideAlong the axial directionIn the forming step of manufacturing a sintered magnet die characterized by forming a notch and an anisotropic sintered magnet, the die is used,AndWhen the permanent magnet powder is supplied into the cavity of the die composed of the die, the upper punch and the lower punch, the magnetization 4πI of the die at the time of supplying the permanent magnet powder into the cavity is set to 6000 Gauss or less, and the permanent magnet powder is easily magnetized. Magnetic field to orient the directionIn the orientation magnetic field application directionApply and furtherPermanent magnet powder with upper punch and lower punchProvided is a method for producing an anisotropic sintered magnet, which is molded by compression.
[0020]
Hereinafter, the present invention will be described in more detail.
The die for forming a sintered magnet according to the present invention is formed of a metal material having magnetism, and has a substantially hollow H-shaped cross section as shown in FIG. In FIG. 1, reference numeral 11 denotes a block shape or a column shape (in the figure, a square block shape or a short-axis square column shape) in which a hollow portion (in the figure, a hollow portion having a square cross section) that becomes the cavity portion 12 is formed. ) Dice body. In this case, the die 10 is applied with a magnetic field 13 in the lateral direction in the figure, and the notches 14 and 14 are respectively formed along the axial direction at the center of both sides perpendicular to the direction of the orientation magnetic field 13. Accordingly, the width between the center portions is smaller than the width between the end portions in the direction perpendicular to the orientation magnetic field direction.
[0021]
The effect of using such an H-shaped die will be described with reference to FIGS.
FIG. 3 shows the orientation magnetic field created by the electromagnet for forming a transverse magnetic field. FIG. 3 shows a magnetic field distribution without a die. 3, 31 denotes an electromagnet pole piece (iron core), 32 denotes a magnetic field line, 33 denotes an isomagnetic flux density line (contour line), and 34 denotes a center line of the pole piece. In the figure, the magnetic field generating portion of the electromagnet is enlarged. In practice, a coil is wound around each of the two pole pieces, and a direct current flows. There is an iron yoke on the outside of the pole piece to form a magnetic circuit. The magnetic field lines coming out of the pole piece are parallel to the center line on the center line of the pole piece, but flow so as to spread at the end. To expand the magnetic field region parallel to the center line, the diameter of the pole piece can be increased, but this leads to an increase in the cost of the apparatus and an increase in power consumption. In the figure, the “H” mark indicates that the magnetic flux density is high, and the “L” mark indicates that the magnetic flux density is low. The magnetic field rises on the pole piece side, and the magnetic flux emitted from the pole piece flows so as to spread in space, so the magnetic field is lowered at the center plane between the pole pieces, and the orientation magnetic field decreases as the distance from the center line of the pole piece also increases in the center plane. .
[0022]
FIG. 4 shows a state of an orientation magnetic field when a magnetic die proposed in Japanese Patent Laid-Open No. 9-35977 is placed in an electromagnet for forming a transverse magnetic field and magnet powder is filled in the cavity portion. The saturation magnetization of the die is matched to the saturation magnetization of the magnet powder. 4, 41 denotes an electromagnet pole piece (iron core), 42 denotes magnetic lines of force, 43 denotes isomagnetic flux density lines (contour lines), 44 denotes a magnetic die, and 45 denotes magnet powder filled in the cavity 46. By using a magnetic die, the magnetic field in the magnet powder is not disturbed as shown in FIG. 5, and a substantially parallel orientation magnetic field is applied. However, the magnetic field lines coming out of the pole pieces flow parallel to the center line on the center line of the pole pieces but spread out at the ends, so the magnetic field increases on the pole piece side, and at the center plane between the pole pieces. The tendency for the magnetic field to decrease remains unchanged. For this reason, a difference arises in the magnetic flux density inside the magnet powder, and the magnetic force that the magnet powder tries to move to the pole piece side having a high magnetic flux density works and moves. The movement of the magnet powder causes a difference in the density of the magnet powder, and the saturation magnetization density changes depending on the location. The distribution of saturation magnetization density causes the orientation magnetic field to be disturbed, and a sintered magnet with less orientation disorder cannot be obtained.
[0023]
Therefore, according to the dice of the present invention shown in FIG. 2, the magnetic flux emitted from the end of the pole piece is magnetized by cutting away the part away from the center line of the pole piece at the center plane between the pole pieces where the magnetic flux density is low. It passes through the die and flows to the center line side of the die because the die is easier to flow than air at the notch. For this reason, the magnetic flux density in the center plane between the pole pieces in the cavity is increased, the magnetic flux density distribution in the magnet powder is eliminated, and the magnetic films can be oriented according to the parallel orientation magnetic field. In FIG. 2, 21 is a pole piece, 22 is a line of magnetic force, 23 is a line of equal magnetic flux density, 24 is a die, 25 is magnet powder, and 26 is a cavity part.
[0024]
Therefore, by applying the present invention, the magnetic flux density in the cavity space at the time of molding is uniform and the direction is neatly aligned with the direction in which the magnetic field is applied, so each particle of the magnet powder in the cavity is easily magnetized. Are directed along the magnetic flux having the same direction, and the resulting molded body has a high degree of orientation. As a result, a magnet having a high residual magnetic flux density can be obtained. In addition, when a magnet is manufactured by cutting a large sintered block, the characteristics of the magnet cut out from near the surface are not seen, and the yield is remarkably improved.
[0025]
Here, in FIG. 1, the dimensions of the die body 11 are appropriately selected and are not particularly limited. However, the length Td in the orientation magnetic field direction is 50 to 300 mm, and the width Wd in the direction perpendicular to the orientation magnetic field direction is 50. The dimension of the cavity 12 can be 5 to 250 mm in the length Tm in the orientation magnetic field direction and 5 to 200 mm in the width Wm in the direction perpendicular to the orientation magnetic field direction.
[0026]
Furthermore, the dimension of the notch 14 is such that the maximum length a in the orientation magnetic field direction is 1/5 to 2/3, particularly 2/5 to 3/5 of the length Td of the die body in the orientation magnetic field direction. It is preferable that the maximum width b in the direction perpendicular to the orientation magnetic field direction is 1/10 to 1/3, particularly 1/5 to 3/10, of the width Wd perpendicular to the orientation magnetic field direction of the die body. Is preferred.
[0027]
The die shape of the present invention is not limited to that shown in FIG. For example, in FIG. 1, the cutout portion 14 is formed in a quadrangular cross section, but as shown in FIGS. 6A and 6B, the cutout portion 14 is semicircular and semielliptical. Or a semi-polygonal shape, etc., and various modifications can be made within the scope of the present invention. Further, as shown in FIG. 7A, two cavities may be provided in the die body.
[0028]
In the present invention, as described above, the die is formed of a metal material having magnetism. In this case, it is necessary to form the die from a metal material having a saturation magnetization 4πIs of 500 to 12,000 gauss. Even within this range, it is particularly preferable to use a magnetic metal material having a saturation magnetization in the range of 1500 to 8000 gauss because the effects of the present invention remarkably appear. When a metal material having a saturation magnetization of 4πIs less than 500 gauss is used, or when it is made of a non-magnetic material, a magnetic pole is generated on the surface of the molded body, so that the magnetic flux around the molded body Since the direction is disturbed, the orientation of the produced molded body is also disturbed, and the resultant sintered magnet is also poorly oriented, resulting in a magnet having a small residual magnetic flux density. Further, when the saturation magnetization 4πIs is larger than 12000 Gauss, a magnetic pole opposite to that obtained when a metal material having a saturation magnetization 4πIs of less than 500 Gauss is generated on the surface of the molded body. Will be disturbed.
[0029]
As the metal material having magnetism of the present invention, cemented carbide and alloy carbon steel are desirable. Cemented carbide is WC, TiC, MoC, NbC, TaC, Cr₃C₂Is an alloy obtained by sintering and bonding a carbide powder of a metal belonging to group IVa, Va, VIa such as Co, Ni, Mo, Fe, Cu, Pb, Sn, or an alloy thereof. The magnetism varies depending on the amount of carbon and the amount of iron, cobalt, nickel, etc., the type of additive, the amount added, and the like. Any cemented carbide may be applied to the present invention as long as it has predetermined magnetic properties.
[0030]
The alloy carbon steel is an alloy mainly composed of Fe-C, and in particular, die steel, carbon tool steel, alloy tool steel, high speed steel, and the like are preferably used. Any of these alloy carbon steels can be used as long as they have predetermined magnetic properties.
[0031]
In the present invention, it is further necessary that the magnetization 4πI of the die when supplying the permanent magnet powder into the cavity is 6000 gauss or less. Even within this range, it is preferable that the magnetization 4πI of the die is 2000 gauss or less when the permanent magnet powder is supplied into the cavity, since the effects of the present invention are remarkably exhibited. If it is 500 gauss or less, more preferable results can be obtained.
[0032]
That is, since the magnetization 4πI remaining in the die when the magnet powder is supplied into the cavity space is 6000 Gauss or less, the magnet powder adheres to the die when the magnet powder is supplied into the cavity. Trouble does not occur, so the magnet powder can be uniformly filled into the cavity. Therefore, not only the working efficiency at the time of molding is improved, but also the packing density in the cavity is uniform, so the density of the molded body is also uniform, and therefore there is no variation in shrinkage during sintering. An irregularly shaped sintered body is not produced, and the sintered body shape can be made as designed. For this reason, the manufacturing yield is improved, the machining allowance can be reduced, and the material yield is also improved. If the die magnetization 4πI when supplying permanent magnet powder into the cavity is greater than 6000 gauss, problems such as magnet powder adhering to the die are likely to occur when supplying magnet powder into the cavity. This is not suitable because the above-mentioned problems occur.
[0033]
In order to make the die magnetization 4πI at the time of supplying permanent magnet powder into the cavity 6000 Gauss or less, the die material is a metal material having a saturation magnetization 4πIs of 500 to 12000 Gauss and a residual magnetization 4πIr of 6000 Gauss or less. Or demagnetizing the die before supplying the magnetic powder into the cavity. When demagnetizing before supplying magnet powder, either DC demagnetization or AC demagnetization is applicable.
[0034]
In the present invention, not only the die but also the upper punch and the lower punch are made of a metal material having a saturation magnetization of 4πIs of 500 to 12,000 gauss, which suppresses the generation of magnetic poles on the surface of the molded body. This is preferable because the effect appears more remarkably. At this time, the entire upper punch and lower punch may be made of a magnetic metal material, but only the tip portion in contact with the molded body may be made of a magnetic metal material.
[0035]
The method for manufacturing an anisotropic sintered magnet of the present invention uses the above-mentioned die, sets the magnetization 4πI of the die when supplying the permanent magnet powder into the cavity to 6000 Gauss or less, and supplies the permanent magnet powder into the cavity. A magnetic field for orienting the direction of easy magnetization of the permanent magnet powder is applied, and the permanent magnet powder in the cavity is compressed by an upper punch and a lower punch to be molded. In this case, the magnetic field application method, compression molding method, and conditions thereof can be performed according to conventional methods.
[0036]
Here, as an anisotropic sintered magnet which is an object of the present invention, ferrite magnets such as Ba ferrite and Sr ferrite, rare earth magnets such as R—Co and R—Fe—B (R: Sc, In particular, when the present invention is applied to the production of a rare earth magnet, the effects of the present invention are remarkably exhibited, and a preferable result can be obtained. These magnets are manufactured as follows.
[0037]
R-Co rare earth magnets are RCo₅System, R₂Co₁₇There are systems, but most of them are put to practical use.₂Co₁₇It is a system. R₂Co₁₇The rare earth magnet usually comprises 20 to 28% R, 5 to 30% Fe, 3 to 10% Cu, 1 to 5% Zr, and the balance Co in weight percentage, and the following manufacturing method Manufactured by. First, raw metal is weighed, melted and cast, and the resulting alloy is finely pulverized to an average particle size of 1 to 20 μm.₂Co₁₇A rare earth permanent magnet powder is obtained. R₂Co₁₇The rare earth permanent magnet powder is molded in a magnetic field according to the present invention, then sintered at 1100 to 1250 ° C. for 0.5 to 5 hours, and then 0.5 to 0.5 ° C. lower than the sintering temperature. Solutionized for ~ 5 hours and finally aging treated. The aging treatment is usually held at 700 to 950 ° C. for a predetermined time as the first stage aging, and then continuous cooling or multistage aging is performed.
[0038]
R-Fe-B rare earth magnets usually consist of 5 to 40% R, 50 to 90% Fe, and 0.2 to 8% B in weight percentage. In order to improve magnetic characteristics, additive elements such as C, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Sn, Hf, Ta, and W Is often added. The amount of these additives is usually 30% by weight or less for Co and 8% by weight or less for other elements. If more additives are added, the magnetic properties are deteriorated. The manufacturing method of the R—Fe—B rare earth magnet is as follows. The raw metal is weighed, melted and cast, and the resulting alloy is finely pulverized to an average particle size of 1 to 20 μm to obtain an R—Fe—B rare earth permanent magnet powder. The R—Fe—B rare earth permanent magnet powder is molded in a magnetic field according to the present invention and sintered at 1000 to 1200 ° C. for 0.5 to 5 hours. Finally, an aging treatment is performed at 400 to 1000 ° C. to obtain an R—Fe—B rare earth magnet.
[0039]
  According to the present invention, in the forming step of the anisotropic sintered magnet, the die is formed of a metal material having a saturation magnetization 4πIs of 500 to 12000 gauss and the die shape viewed from above the cavity is oriented. For sintered magnets whose width in the direction perpendicular to the magnetic field direction is preferably 1/5 to 2/3 of the width in the direction of the orientation magnetic field and the groove is cut in the vertical direction and the center is smaller than both ends Using a die, a permanent magnet powder is supplied into a mold cavity consisting of this, an upper punch, and a lower punch, and a magnetic field for orienting the magnetization direction is applied to the powder, and then compressed and molded. Thus, the magnetic poles can be prevented from appearing on the surface of the molded body, and the distribution of the magnetic flux can be made uniform and the directions of the magnetic flux can be aligned in parallel. Furthermore, the permanent magnet powder is uniformly filled into the cavity.Butit can. In this case, the molding can be performed in a magnetic field by a known method in a magnetic field. Therefore, an anisotropic sintered magnet with improved residual magnetic flux density can be manufactured with high yield.
[0040]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0041]
[Comparative Example 1]
Nd in atomic%_13.8Dy₁Fe_73.7Co₄B_6.5Al₁An alloy ingot was prepared by melting and casting each raw metal having a purity of 99.9 wt% or more in an argon atmosphere using an induction heating high-frequency melting furnace. This alloy ingot is subjected to a homogenization heat treatment at 1100 ° C. for 24 hours in an argon atmosphere, then coarsely pulverized using a jaw crusher and a brown mill in an argon atmosphere, and then finely pulverized using a jet mill using nitrogen gas. The R-Fe-B magnet powder having an average particle diameter of 5 μm was prepared.
[0042]
Molding was performed using this magnet powder. The die used for forming was a cemented carbide (alloy sintered and bonded using Co and Ni with WC carbide powder as the main component) having a saturation magnetization of 4πIs = 3600 gauss and a residual magnetization of 4πIr = 500 gauss. The dimensions of the die viewed from above the cavity are Wd = 210 mm, Td = 200 mm, and are conventional with no notches. Magnet powder is supplied into the cavity, a magnetic field of 15 kOe is applied by an electromagnet, and 1 ton / cm in the direction perpendicular to the magnetic field application direction while the magnetic field is applied.²The molding was performed under the pressure of The height of the produced molded body is 30 mm. The cross-sectional shape in the direction perpendicular to the compression direction of the cavity is Wm = 50 mm and Tm = 130 mm. Wd, Td, Wm, and Tm are the parts described with reference to FIG.
[0043]
This molded body was sintered in vacuum at 1060 ° C. for 90 minutes, and then further subjected to aging heat treatment at 540 ° C. The magnetic properties of the obtained R—Fe—B based sintered magnet were measured using a B—H tracer. The residual magnetic flux density of the magnet at this time was Br = 12.7 kG. Further, when the dimensions We and Wc of the portions perpendicular to the orientation direction on the surface of the sintered body were measured, a drum-shaped sintered body as shown in FIG. 8A was obtained (in FIG. 8, 61 is an orientation magnetic field, 62 is Sintered magnet is shown), We = 42.5 mm, Wc = 41.5 mm. Since the magnet powder moved to the pole piece side in the cavity, the density of the compact at the magnet end increased, and the dimension at the end increased by 1 mm when sintered.
[0044]
In addition, when the cross-sectional shape in the direction perpendicular to the compression direction of the cavity is smaller than Wm = 20 mm and Tm = 30 mm as compared with the above example, We = 17 mm and Wc = 16.9 mm, and the end and center of the sintered body There was almost no difference. That is, it can be seen that the larger the ratio Tm / Td between the dimension Tm of the compact and the die dimension Td, the greater the problem of variation in the size of the sintered compact.
[0045]
[Example 1]
A magnet alloy powder similar to that in Comparative Example 1 was molded using a die made of the same material as in Comparative Example 1. In this case, the dimensions of the die viewed from above the cavity are Wd = 210 mm, Td = 200 mm, the notch a = 100 mm, b = 50 mm, and the cavity cross-sectional shape is Wm = 50 mm, Tm = 130 mm as shown in FIG. It is the die shape of the invention. Others were molded under the same conditions as in Comparative Example 1, sintered and aged under the same conditions to produce magnets, and their magnetic properties were measured using a BH tracer. Br = 12.75 kG there were. Further, when the dimensions We and Wc of the portion perpendicular to the orientation direction of the sintered body surface were also measured, there was almost no difference at We = 42.1 mm and Wc = 41.9 mm. Compared with Comparative Example 1, The residual magnetization density Br of the magnet slightly increased, and the dimensional accuracy was remarkably improved.
[0046]
[Comparative Example 2]
A magnet alloy powder similar to that in Comparative Example 1 was molded using a die made of the same material as in Comparative Example 1. In this case, the dimensions of the die as viewed from above the cavity are Wd = 210 mm, Td = 200 mm, and the cavity has a sectional shape of Wm = 30 mm and two Tm = 130 mm. The die shape of Comparative Example 2 shown in FIG. It is. Others were molded under the same conditions as in Comparative Example 1, sintered and aged under the same conditions to produce magnets, and their magnetic properties were measured using a BH tracer. Br = 12.7 kG there were. Further, when the dimensions of the sintered body surface were measured, as shown in FIG. 8B, the sintered body was warped, We = 25.5 mm, Wc = 24.7 mm, X1 = 0.7 mm, X2 = 0. 0.4 mm and X = 24.3 mm. Since the magnet powder moved to the pole piece side in the cavity, the density of the compact at the magnet end increased, and the end became larger when sintered. In the case of two pieces, the sintered body is also warped, and the dimension X excluding the warped portion is smaller than the minimum dimension of the sintered body (in this case, Wc), so that a predetermined dimension can be obtained after processing. Shows that it is necessary to make a larger block in anticipation of warping.
[0047]
[Example 2]
A magnet alloy powder similar to that in Comparative Example 1 was molded using a die made of the same material as in Comparative Example 2. In this case, the dimensions of the die viewed from above the cavity are Wd = 210 mm, Td = 200 mm, notches a = 100 mm, b = 50 mm, and the cavity has a cross-sectional shape of Wm = 30 mm and Tm = 130 mm in FIG. A die shape of the present invention shown in A). Others were molded under the same conditions as in Comparative Example 1, sintered and aged under the same conditions to produce magnets, and their magnetic properties were measured using a BH tracer. Br = 12.75 kG there were. Further, when the dimensions We, Wc, and X of the sintered body were measured, a sintered body having no warpage even in a two-piece mold with We = 25.2 mm, Wc = 25.1 mm, and X = 25.1 mm. Obtained. Compared with Comparative Example 2, the residual magnetization density Br of the magnet slightly increased, and the dimensional accuracy was significantly improved.
[0048]
【The invention's effect】
According to the present invention, an anisotropic sintered magnet having a large residual magnetic flux density can be manufactured with a high yield by using a large block, particularly a large block having a volume of 30 cubic centimeters or more.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of a die shape according to the present invention.
FIG. 2 is an explanatory diagram showing a magnetic field strength distribution when a die of the present invention is placed in an electromagnet.
FIG. 3 is an explanatory diagram showing a magnetic field strength distribution created by an electromagnet.
FIG. 4 is an explanatory diagram showing a magnetic field strength distribution when a conventional die is placed in an electromagnet.
FIG. 5 is an explanatory diagram showing a magnetic flux distribution when a uniform magnetic field is applied to a magnetic body.
FIGS. 6A and 6B are plan views showing dice shapes of the present invention having different notch shapes, respectively. FIGS.
7A is a plan view showing a two-piece die shape of Example 2, and FIG. 7B is Comparative Example 2. FIG.
8A is a plan view showing the shape of a sintered magnet of Comparative Example 1, and FIG. 8B is a shape of a sintered magnet of Comparative Example 2;
[Explanation of symbols]
10 dice
11 Dice body
12 Cavity
13 Orientation magnetic field
14 Notch
21 Pole Peace
22 Magnetic field lines
23 Isomagnetic flux density line
24 Magnetic Dies of the Present Invention
25 Magnet powder
26 Cavity
31 pole piece
32 Magnetic field lines
33 Isomagnetic flux density line
34 Pole Piece Centerline
41 pole piece
42 Magnetic field lines
43 equal magnetic flux density lines
44 Conventional magnetic die
45 Magnet powder
46 Cavity
51 Magnetic material
52 Magnetic flux
61 Orientation magnetic field
62 Sintered magnet

Claims (4)

In the molding process of manufacturing an anisotropic sintered magnet, a magnetic field for orienting the easy magnetization direction is applied to the permanent magnet powder, and the permanent magnet powder is further compressed by the upper punch and the lower punch to be molded. A magnet die,
A die formed of a hollow rectangular block shape or a short-axis square column shape in which a cavity portion to which a permanent magnet powder is supplied is formed along the axial direction and is formed of a metal material having a saturation magnetization of 4πIs of 500 to 12000 Gauss. the body, in a direction at right angles the direction of the orientation magnetic field applying direction to the application direction of the orientation magnetic field applied from the side of the die body, notch along the axial direction in the central portion of the both outer sides A die for a sintered magnet, characterized by forming a part. The length along the direction in which the aligning magnetic field of the notch is applied, according to claim 1 which is 1 / 5-2 / 3 of the length along the direction in which the aligning magnetic field of said die body is applied The die for sintered magnets as described.   The die for a sintered magnet according to claim 1 or 2, wherein the die has a substantially hollow H-shaped cross section. In the forming step of manufacturing an anisotropic sintered magnet, the sintered magnet die according to any one of claims 1 to 3 is used, and the magnetization 4πI of the die when supplying permanent magnet powder into the cavity is 6000. The permanent magnet powder is supplied into the cavity of the die consisting of the die, the upper punch, and the lower punch, and a magnetic field for orienting the easy magnetization direction of the permanent magnet powder is applied in the orientation magnetic field application direction. Furthermore, a method for producing an anisotropic sintered magnet, wherein the molding is performed by further compressing permanent magnet powder with an upper punch and a lower punch .

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