Plate magnet with circumferentially oriented arc-shaped cross section, radially oriented arc-shaped cross section, or concentratedly oriented rectangular cross section, and its manufacturing method

Abstract

To provide a method for efficient manufacturing of a peripheral oriented arc-shaped profile sheet magnet with a high surface magnetic flux density and low variation of a quantity of the magnetic leakage flux in a direction perpendicular to an orientation direction at all locations on its surface.SOLUTION: A manufacturing method for a magnet comprises a filling process for filling powder for neodymium magnets the average particle diameter of which is within a specific range and that contains a lubricant at a specific value or less into a mold having two or more cavities including a cavity with an arc-shaped profile at a specific pack density to obtain a powder filled mold, an orientation process for loading the powder filled mold into 2 N poles (N is a natural number) orientation yoke and orientating the powder for neodymium magnets by applying a specific orientation magnetic field without applying a pressure to the filled powder for neodymium magnets, to obtain an oriented mold, and a sintering process for loading the oriented mold into a sintering furnace to sinter the powder together with the mold to obtain a sintered body, so that a peripheral oriented arc-shaped profile sheet magnet is obtained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plate magnet having a circumferentially oriented arc-shaped cross section, a radially oriented arc-shaped cross section, or a concentratedly oriented rectangular cross section, and a method for manufacturing the same. [Background technology]

[0002] Examples of plate-shaped magnets with controlled orientation include plate magnets with a circumferentially oriented arc-shaped cross section, a radially oriented arc-shaped cross section, and a concentratedly oriented rectangular cross section.

[0003] As a method for manufacturing a radially oriented plate magnet with an arcuate cross section, for example, Patent Document 1 discloses a method for manufacturing a radially oriented sintered Nd-Fe-B tile-shaped magnetic body, in which (Step 1) Nd-Fe-B alloy flakes are manufactured by a strip casting method, and the Nd-Fe-B alloy flakes are converted into Nd-Fe-B alloy powder through a hydrogenation process and a jet mill process, (Step 2) the Nd-Fe-B alloy powder is placed in a die for radial orientation, and powder filling, magnetization, and molding processes are carried out twice as follows: (Step 2-1) is the first powder filling, magnetization, and pre-pressing, in which a required weight W1 of sintered Nd-Fe-B alloy powder is weighed out and then subjected to a DC magnetization. (Step 2-1) is a process for producing a radially oriented sintered Nd-Fe-B tile-shaped magnetic body, the process comprising: (a) feeding the Nd-Fe-B alloy powder into the die installed in a DC magnetic field press, adjusting the magnetic field and compacting pressure to form a primary green body; (b) filling the Nd-Fe-B alloy powder with a required weight W2, and then feeding the powder into the die installed in the DC magnetic field press with the primary green body; adjusting the magnetic field and compacting pressure to form a secondary green body; and (c) sintering and aging the green body after the two compacting and orientation processes to produce the sintered Nd-Fe-B tile-shaped magnetic body with the required radial orientation. The process also describes that by supplying and compacting the alloy powder twice and controlling the amount of alloy powder supplied and the magnitude of the aligning magnetic field within reasonable ranges each time, it is possible to solve problems such as uneven orientation in the vertical direction of the magnetic body and cracking of the green body compared to conventional techniques. Furthermore, by using a magnetically permeable plate with increased uniformity and rationally designing its dimensions and angles, it is possible to align the direction of the magnetic lines of force in the tile-shaped mold with the design value even under conditions where the externally applied aligning magnetic field is increased, thereby improving the uniformity of the residual magnetic flux density and magnetic properties of the Nd-Fe-B tile-shaped magnetic material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-097224 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to propose a method for more efficiently manufacturing plate magnets with radially oriented arc-shaped cross sections, circumferentially oriented arc-shaped cross sections, or concentratedly oriented rectangular cross sections as described above. Furthermore, it is desirable that the plate magnets obtained by this manufacturing method have a high surface magnetic flux density and small variations in the amount of leakage magnetic flux in the direction perpendicular to the orientation direction at all points on the surface.

[0006] An object of the present invention is to solve the above-mentioned problems. In other words, the object of the present invention is to provide a plate magnet with a circumferentially oriented arc-shaped cross section, a radially oriented arc-shaped cross section, or a concentratedly oriented rectangular cross section, which has a high surface magnetic flux density and little variation in the amount of leakage magnetic flux in the direction perpendicular to the orientation direction at all points on the surface, as well as a method for efficiently manufacturing them. [Means for solving the problem]

[0007] The present inventors have conducted extensive research and have completed the present invention. The present invention includes the following (1) to (4). (1) A neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant is mixed at a concentration of 3.4 to 4.0 g / cm 3 a filling step (1) of filling a mold having two or more cavities, including those having an arc-shaped cross section, with the powder at a packing density of 1000 to obtain a powder-filled mold; an orientation step (1) in which the powder-filled mold is loaded into a 2N-pole (N is a natural number) orienting yoke so that the arc of the cross section of the cavity is aligned with the orientation direction, and an orienting magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, thereby orienting the neodymium magnet powder and obtaining an oriented mold; a sintering step in which the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside and sintered together with the mold to obtain a sintered body; A magnet manufacturing method comprising the steps of: obtaining a circumferentially oriented plate magnet with an arc-shaped cross section; (2) A neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant is mixed at a concentration of 3.4 to 4.0 g / cm 3 a filling step (2) of filling a mold having two or more cavities, including those having an arc-shaped cross section, with the powder at a packing density of 1000 to obtain a powder-filled mold; an orientation step (2) in which the powder-filled mold is loaded into a 2N-pole (N is a natural number) orienting yoke so that the arc of the cross section of the cavity is perpendicular to the orientation direction, and an orienting magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, thereby orienting the neodymium magnet powder and obtaining an oriented mold; a sintering step in which the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside and sintered together with the mold to obtain a sintered body; A method for manufacturing a magnet, comprising the steps of: obtaining a radially oriented plate magnet with an arc-shaped cross section; (3) A neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant is mixed at a concentration of 3.4 to 4.0 g / cm 3 a filling step (3) of filling a mold having two or more cavities, including those having a rectangular cross section, with the powder at a packing density of 1000 to obtain a powder-filled mold; an orientation step (3) in which the powder-filled mold is loaded into a 2N-pole (N is a natural number) orientation yoke so that one side of the rectangular cross section of the cavity intersects with the orientation direction, and an orientation magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, thereby orienting the neodymium magnet powder and obtaining an oriented mold; a sintering step in which the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside and sintered together with the mold to obtain a sintered body; A magnet manufacturing method comprising the steps of: obtaining a concentrated orientation rectangular cross-section plate magnet; (4) A plate magnet with a circumferentially oriented, radially oriented, or rectangular cross section, in which the variation in the amount of leakage magnetic flux in the direction perpendicular to the orientation direction at all points on the surface is within ±5% of the average value. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide plate magnets with a circumferentially oriented arc-shaped cross section, a radially oriented arc-shaped cross section, or a concentratedly oriented rectangular cross section, which have a high surface magnetic flux density and little variation in the amount of leakage magnetic flux in the direction perpendicular to the orientation direction at all points on the surface, as well as methods for efficiently manufacturing them. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view showing a preferred example of a mold used in the manufacturing method of the present invention. [Figure 2] FIG. 2 is a schematic top view of the mold shown in FIG. [Figure 3] FIG. 1 is a schematic perspective view showing another preferred example of a mold used in the manufacturing method of the present invention. [Figure 4] FIG. 4 is a schematic top view of the mold shown in FIG. 3. [Figure 5] FIG. 1 is a diagram (schematic top view) showing the state in which a powder-filled mold is loaded into an orienting yoke. [Figure 6] FIG. 10 is another view (schematic top view) of the powder-filled mold being loaded into the orienting yoke, seen from above. [Figure 7] 10 is yet another view (schematic top view) of the powder-filled mold being loaded into the orienting yoke, seen from above. FIG. [Figure 8]FIG. 1 is a schematic perspective view showing a circumferentially oriented magnet of the present invention. [Figure 9] FIG. 1 is a schematic perspective view showing a radially oriented magnet of the present invention. [Figure 10] FIG. 1 is a schematic perspective view showing a concentrated orientation magnet of the present invention. [Figure 11] FIG. 10 is a diagram used to explain a method for measuring the variation in the amount of leakage magnetic flux in a direction perpendicular to the orientation direction at all points on the surface. [Figure 12] Photographs of the front, back, and both end faces of a circumferentially oriented, arc-shaped cross-section plate magnet obtained in the example. [Figure 13] 1 is a photograph of the end face of a radially oriented plate magnet with an arc-shaped cross section obtained in an example. [Figure 14] Photographs of the front, back, and both end faces of a concentrated orientation rectangular cross-section plate magnet obtained in the example. [Figure 15] This figure shows the results of measuring the orientation direction at each measurement point on the magnet surface for each of the circumferentially oriented, arc-shaped cross-section plate magnet, radially oriented, arc-shaped cross-section plate magnet, and concentratedly oriented, rectangular cross-section plate magnet obtained in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] The manufacturing method of the present invention will be described. The present invention provides a neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant, at a concentration of 3.4 to 4.0 g / cm. 3a filling step (1) of filling a mold having two or more cavities, including those with arc-shaped cross sections, with a packing density of 1000 rpm to obtain a powder-filled mold; an orientation step (2) of loading the powder-filled mold into a 2N-pole (N is a natural number) orienting yoke so that the arcs of the cross sections of the cavities are aligned along the orientation direction, and orienting the filled neodymium magnet powder by applying an orienting magnetic field of 1.0 to 5.0 T without applying pressure to the neodymium magnet powder to obtain an oriented mold; and a sintering step of removing a compact of the oriented neodymium magnet powder from the oriented mold and loading it into a sintering furnace for sintering, or loading the oriented mold with the oriented neodymium magnet powder compact inside into a sintering furnace and sintering the mold together to obtain a sintered body, thereby obtaining a circumferentially oriented arc-shaped cross-section plate magnet. This method of manufacturing a circumferentially oriented, cross-sectionally arcuate plate magnet is hereinafter also referred to as "the method of manufacturing a circumferentially oriented magnet of the present invention."

[0011] The present invention also provides a neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant, at a concentration of 3.4 to 4.0 g / cm. 3 a filling step (2) of filling a mold having two or more cavities, including those with arc-shaped cross sections, with a packing density of 1000 rpm to obtain a powder-filled mold; an orientation step (2) of loading the powder-filled mold into a 2N-pole (N is a natural number) orienting yoke so that the arcs of the cross sections of the cavities are perpendicular to the orientation direction, and orienting the filled neodymium magnet powder by applying an orienting magnetic field of 1.0 to 5.0 T without applying pressure to the filled neodymium magnet powder to obtain an oriented mold; and a sintering step of removing a compact of the oriented neodymium magnet powder from the oriented mold and loading it into a sintering furnace for sintering, or loading the oriented mold with the oriented neodymium magnet powder compact inside into a sintering furnace and sintering the mold together to obtain a sintered body, thereby obtaining a radially oriented plate magnet with an arc-shaped cross section. This method of manufacturing a radially oriented plate magnet with an arc-shaped cross section is hereinafter also referred to as "the method of manufacturing a radially oriented magnet of the present invention."

[0012] The present invention also provides a neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant, at a concentration of 3.4 to 4.0 g / cm. 3 a filling step (3) of filling a mold having two or more cavities, including those having a rectangular cross section, with a packing density of 1.0 T to obtain a powder-filled mold; an orientation step (3) of loading the powder-filled mold into a 2N-pole (N is a natural number) orienting yoke so that one side of the rectangular cross section of the cavity intersects the orientation direction, and orienting the filled neodymium magnet powder by applying an orienting magnetic field of 1.0 to 5.0 T without applying pressure to the filled neodymium magnet powder, thereby obtaining an oriented mold; and a sintering step of removing a compact of the oriented neodymium magnet powder from the oriented mold and loading it into a sintering furnace for sintering, or loading the oriented mold with the oriented neodymium magnet powder compact inside into a sintering furnace and sintering the mold together to obtain a sintered body, thereby obtaining a concentrated oriented rectangular cross-section plate magnet. This method of manufacturing a concentrated orientation magnet with a rectangular cross section is hereinafter also referred to as "the method of manufacturing a concentrated orientation magnet of the present invention."

[0013] In the following, when simply referring to "the manufacturing method of the present invention," this means any of the manufacturing method of the circumferentially oriented magnet of the present invention, the manufacturing method of the radially oriented magnet of the present invention, and the manufacturing method of the concentratedly oriented magnet of the present invention.

[0014] Furthermore, the present invention provides a plate magnet with a circumferentially oriented, radially oriented, or concentratedly oriented rectangular cross section, in which the variation in the amount of leakage magnetic flux in a direction perpendicular to the orientation direction at all points on the surface is within plus or minus 5% of the average value. Such a circumferentially oriented plate magnet having an arc-shaped cross section will be referred to below as the "circumferentially oriented magnet of the present invention." Furthermore, such a radially oriented plate magnet having an arc-shaped cross section will hereinafter be referred to as the "radially oriented magnet of the present invention." Furthermore, such a concentrated orientation plate magnet having a rectangular cross section will be referred to below as the "concentrated orientation magnet of the present invention."

[0015] Hereinafter, when simply referring to "the magnet of the present invention," this means any of the circumferentially oriented magnet of the present invention, the radially oriented magnet of the present invention, and the concentratedly oriented magnet of the present invention.

[0016] The circumferentially oriented magnet of the present invention is preferably manufactured by the method for manufacturing a circumferentially oriented magnet of the present invention. Furthermore, the radially oriented magnet of the present invention is preferably manufactured by the method of manufacturing a radially oriented magnet of the present invention. Furthermore, the concentrated orientation magnet of the present invention is preferably manufactured by the method for manufacturing a concentrated orientation magnet of the present invention.

[0017] <Production Method of the Present Invention> The manufacturing method of the present invention will be described. The manufacturing method of the present invention includes a filling step, an orientation step, and a sintering step.

[0018] <Filling process> The filling steps (filling step (1) and filling step (2)) in the method for producing a circumferentially oriented magnet of the present invention and the method for producing a radially oriented magnet of the present invention are common to each other. In contrast, the filling step (filling step (3)) in the method for producing concentrated orientation magnets of the present invention has a different cavity shape, but is otherwise common.

[0019] In the filling step of the manufacturing method of the present invention, neodymium magnet powder is prepared.

[0020] Neodymium magnet powder is a powder whose main components are neodymium, a transition element (T), and boron (B). Here, "main component" means that the total content is 90% by mass or more, and more preferably, this total content is 95% by mass or more. The transition element (T) preferably contains Fe, Co, Ni, etc. In particular, Nd-Fe-B based neodymium magnet powder is preferred.

[0021] The average particle size of the neodymium magnet powder is 1.0 to 5.0 μm, and preferably 2.5 to 3.5 μm. Neodymium magnet powder consists of an Nd-rich phase, which is the grain boundary phase component, and an NdFe 14 It is preferable that the main phase is composed of single crystal particles of the B phase. If the main phase is single crystal, the particles have one easy axis of magnetization, so the particles tend to be oriented in the direction of the generated magnetic flux, resulting in a higher magnetic flux density of the magnet. If the average particle size is 1.0 to 5.0 μm, it is considered that almost all of the particles are single crystal particles. Here, the average particle size is the median (D) of the particle size distribution measured using a laser-type powder particle size distribution analyzer (for example, HELOS & LODOS, manufactured by Japan Laser Co., Ltd.). 50 ) means

[0022] There are no particular restrictions on the method for preparing neodymium magnet powder, but one example is a method in which a molten master alloy is sprayed onto a rotating roll and quenched to obtain a ribbon with a fine crystalline structure, and then this ribbon is crushed to an average particle size of 1.0 to 5.0 μm to obtain neodymium magnet powder.

[0023] Such neodymium magnet powders contain a lubricant in a content of 1.0 mass% or less. The lubricant content in neodymium magnet powders is preferably 0.01 mass% or more, and more preferably 0.05 to 1.0 mass%.

[0024] As the lubricant, methyl caprylate, methyl laurate, zinc stearate, etc. can be used.

[0025] The above-mentioned lubricant is added to the neodymium magnet powder, and after thorough mixing, the mixture is filled into the cavity of the mold.

[0026] The mold will now be described. Figure 1 is a schematic oblique view showing a suitable example of a mold 1 used in the filling step (1) of the method for manufacturing a circumferentially oriented magnet of the present invention and the filling step (2) of the method for manufacturing a radially oriented magnet of the present invention, and Figure 2 is a schematic top view of the mold 1 shown in Figure 1. 3 is a schematic perspective view showing a suitable example of a mold 1' used in the filling step (3) included in the method for producing concentrated oriented magnets of the present invention, and FIG. 4 is a schematic top view of the mold 1' shown in FIG.

[0027] Although the molds 1 and 1' shown as preferred examples here are cylindrical as shown in Figures 1 and 3, the shape of the mold is not limited to a cylindrical shape. For example, it may be a cylindrical shape with a polygonal cross section, such as a prismatic shape.

[0028] Furthermore, the molds 1, 1' are preferably made of a non-magnetic material, such as graphite carbon.

[0029] The molds 1, 1' shown in FIGS. 1 to 4 have two or more cavities 10, 10'. The cavities 10, 10' are spaces formed by the inner surfaces 5, 5' of the molds 1, 1'.

[0030] The number of cavities 10, 10' in the molds 1, 1' shown in Figures 1 to 4 may be two or more, but it is preferable that this number be the same as the number of poles in the orientation yoke used in the orientation process described below. In other words, since the number of poles in the orientation yoke is 2N (N is a natural number), it is preferable that the number of cavities 10, 10' in the molds 1, 1' is also 2N (N is a natural number). For example, if the number of poles in the orientation yoke used in the orientation process is four, it is preferable that the number of cavities 10, 10' in one mold 1, 1' is four. This is because productivity is further improved.

[0031] 1 and 2 has four cavities 10. All of the cavities 10 have a cross section in the shape of a circular arc. Here, the mold used in the filling step (1) of the manufacturing method for a circumferentially oriented magnet of the present invention and the filling step (2) of the manufacturing method for a radially oriented magnet of the present invention has two or more cavities, at least one of which may have an arc-shaped cross section. For example, one of the multiple cavities may have an arc-shaped cross section, and the others may not have arc-shaped cross sections. However, it is preferable that all of the two or more cavities have an arc-shaped cross section as shown in Figures 1 and 2, as this further increases productivity.

[0032] The degree of arc (curvature, etc.) of cavity 10 and its position in mold 1 (radial position in FIG. 2, etc.) depend on the shape of the aligning magnetic field applied in the aligning step described below. In other words, in the manufacturing method of the circumferentially oriented magnet of the present invention, in order to obtain a circumferentially oriented plate magnet with an arc-shaped cross section, in the filling step (1), the degree and position of the arc in the cavity 10 are shaped (curvature, etc.) so that the arc of the cross section of the cavity 10 is aligned with the orientation direction in the orientation step described below (so that the arc is parallel to the orientation direction). Note that "parallel" here does not mean perfect parallelism. The intention is to form the cavity so that the arc is approximately parallel to the orientation direction, and manufacturing errors, etc. are allowed. The same meaning is used below for "parallel." Furthermore, in the manufacturing method of the radially oriented magnet of the present invention, in order to obtain a radially oriented plate magnet with an arc-shaped cross section, in the filling step (2), the degree and position of the arc in the cavity 10 are shaped (curvature, etc.) so that the arc of the cross section of the cavity 10 is perpendicular to the orientation direction in the orientation step described below. Note that perpendicular here does not mean completely perpendicular. The intention is to form the cavity so that the arc is approximately perpendicular to the orientation direction, and manufacturing errors, etc. are allowed. The same meaning is used below for "perpendicular."

[0033] 3 and 4 has four cavities 10'. All of the cavities 10' have a rectangular cross section. Here, the mold used in the filling step (3) of the method for producing concentratedly oriented magnets of the present invention has two or more cavities, at least one of which may have a rectangular cross section. For example, one of the multiple cavities may have a rectangular cross section, and the others may have non-rectangular cross sections. However, it is preferable that all of the two or more cavities have a rectangular cross section, as shown in Figures 3 and 4, because this further increases productivity.

[0034] The size of the cavity 10' (lengths of long and short sides, etc.) and its position in the mold 1 (radial position in FIG. 4, etc.) depend on the direction of the orientation magnetic field applied in the orientation step described below. That is, in the manufacturing method of the concentrated orientation magnet of the present invention, in order to obtain a concentrated orientation rectangular cross-section plate magnet, in the filling step (3), the lengths and positions of the long and short sides of cavity 10' are set so that the long side of the cross section of cavity 10' intersects with the orientation direction in the orientation step described below. Note that the degree of intersection, i.e., the angle between the long side and the orientation direction, varies depending on the aspect of the concentrated orientation magnet to be obtained (for example, the focus of the orientation direction, etc.).

[0035] In the filling step, neodymium magnet powder is filled into the cavities 10, 10' of the molds 1, 1' described above.

[0036] Here, the filling density when filling the cavity with neodymium magnet powder is 3.4 to 4.0 g / cm 3 The packing density is 3.5 to 3.9 g / cm 3 It is preferable to set the following.

[0037] In the filling step of the manufacturing method of the present invention, the neodymium magnet powder is filled into the cavity of the mold as described above to achieve the above-mentioned filling density. The mold thus obtained, filled with the neodymium magnet powder, is referred to as a powder-filled mold.

[0038] <Orientation process> In the orienting step in the manufacturing method of the present invention, the powder-filled mold is loaded into a 2N-pole (N is a natural number) orienting yoke, and an orienting magnetic field is applied.

[0039] For example, when the molds 1, 1' shown in Figs. 1 to 4 are used, it is preferable to use the four-pole orientation yoke shown in Figs. The orientation yoke shown in Figures 5 to 7 is arranged so that two pairs of opposing coils 22 (four coils in total) are perpendicular to each other, as shown in the figures. In this case, a magnetic field can be generated with the polarity and dotted lines shown in Figures 5 to 7. Then, a powder-filled mold is placed in the center surrounded by these four coils 22.

[0040] Figure 5 is a diagram (schematic top view) showing the state in which a powder-filled mold using the mold 1 shown in Figures 1 and 2 is loaded into the orientation yoke 20 so that the arc of the cross section of the cavity 10 is aligned (parallel) with the orientation direction shown by the dotted line in the orientation process (1) of the manufacturing method of the circumferentially oriented magnet of the present invention. In this state, when an aligning magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, the easy axis of magnetization of the neodymium magnet powder in cavity 10 is oriented in a direction along the arc of the cross section of cavity 10.

[0041] Figure 6 is a diagram (schematic top view) showing the state in which a powder-filled mold using the mold 1 shown in Figures 1 and 2 is loaded into an orientation yoke 20 so that the arc of the cross section of its cavity 10 is perpendicular to the orientation direction shown by the dotted line in the orientation step (2) of the manufacturing method for a radially oriented magnet of the present invention. In this state, when an aligning magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, the easy axis of magnetization of the neodymium magnet powder in cavity 10 is oriented in a direction perpendicular to the arc of the cross section of cavity 10.

[0042] Figure 7 is a diagram (schematic top view) showing the state in which a powder-filled mold using the mold 1' shown in Figures 3 and 4 is loaded into the orientation yoke 20 so that one side (long side) of the rectangular cross section of the cavity 10' intersects with the orientation direction shown by the dotted line in the orientation process (3) in the manufacturing method of the concentrated orientation magnet of the present invention. In this state, when an aligning magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, the easy axis of magnetization of the neodymium magnet powder in cavity 10' is oriented in a direction intersecting one side (long side) of the rectangular cross section of cavity 10 (the alignment direction shown by the dotted line).

[0043] In the orienting step, the orienting magnetic field applied to the neodymium magnet powder is 1.0 to 5.0T, but this orienting magnetic field is preferably 1.5 to 3.0T, and more preferably about 2.0 to 2.5T.

[0044] In the orientation step, the liquid crystal is oriented in the orientation direction as described above, but it is preferable that a magnetic field be applied in a direction perpendicular to the orientation direction before the orientation step, and then an aligning magnetic field be applied in the orientation direction as described above to align the liquid crystal. In other words, the orientation step is preferably a step in which the powder-filled mold is loaded into an orientation device, and without applying pressure to the filled neodymium magnet powder, a magnetic field is applied in a direction perpendicular to the orientation direction, and then an orientation magnetic field of 1.0 to 5.0 T is applied in the orientation direction to orient the neodymium magnet powder and obtain an oriented mold. In this case, the inventors have found that a polar anisotropic magnet with fewer cracks can be obtained by the manufacturing method of the present invention.

[0045] Here, the direction perpendicular to the orientation direction usually coincides with the depth direction in the cavity of the mold.

[0046] The magnetic field applied in the direction perpendicular to the orientation direction may be of the same magnitude as the magnetic field applied in the orientation direction (orientation magnetic field) described above. That is, the magnetic field applied in the direction perpendicular to the orientation direction may be 1.0 to 5.0 T, preferably 1.5 to 3.0 T, and more preferably about 2.0 to 2.5 T.

[0047] This orientation process makes it possible to obtain a mold whose cavity is filled with the oriented neodymium magnet powder. Such a mold is called an oriented mold.

[0048] <Sintering process> In the sintering step in the manufacturing method of the present invention, the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold obtained by the orientation step is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside, and the mold is sintered together.

[0049] The sintering method is not particularly limited. For example, a compact of oriented neodymium magnet powder can be removed from the oriented mold by a conventional knockout method or the like, and then loaded into a sintering furnace for sintering. Sintering can also be performed by conventional press sintering in a magnetic field. Furthermore, for example, the oriented mold can be loaded into a conventional sintering furnace for sintering. The sintering is preferably carried out in a vacuum.

[0050] The sintering temperature must be optimally selected depending on the magnet's components. The sintering temperature is preferably set to 900 to 1100°C.

[0051] The sintering time is preferably 1 to 20 hours, more preferably 2 to 15 hours, and even more preferably about 4 to 10 hours.

[0052] A sintered body can be obtained by removing the oriented neodymium magnet powder compact from the oriented mold and loading it into a sintering furnace for sintering, or by loading the oriented mold with the oriented neodymium magnet powder compact still inside it into a sintering furnace and sintering the mold together.

[0053] For example, using the mold 1 shown in Figures 1 and 2, as described above, neodymium magnet powder is filled into it, and then it is loaded into an orientation yoke as shown in Figure 5, oriented, and then sintered.After that, by applying a magnetic field along the orientation direction of the crystal grains, a circumferentially oriented cross-section arc-shaped plate magnet 30 (circumferentially oriented magnet of the present invention) shown in Figure 8 can be obtained, which is magnetized in the circumferential orientation direction. Furthermore, for example, by using the mold 1 shown in Figures 1 and 2, and filling it with neodymium magnet powder as described above, then loading it into an orientation yoke as shown in Figure 6, orienting it, and then sintering it, and then applying a magnetic field along the orientation direction of the crystal grains, it is possible to obtain a radially oriented plate magnet 32 ​​(radially oriented magnet of the present invention) with an arc-shaped cross section as shown in Figure 9, which is magnetized in the radial orientation direction. Furthermore, for example, by using the mold 1' shown in Figures 3 and 4, and filling it with neodymium magnet powder as described above, then loading it into an orientation yoke as shown in Figure 7, orienting it, and then sintering it, and then applying a magnetic field along the orientation direction of the crystal grains, it is possible to obtain a concentrated orientation cross-section rectangular plate magnet 34 (concentrated orientation magnet of the present invention) shown in Figure 10, which is magnetized in an orientation direction that concentrates at one point.

[0054] Furthermore, by carrying out a process of diffusing heavy rare earth elements from the surface of the sintered body into the interior of the sintered body, the coercive force of the sintered body and, ultimately, the heat resistance of the magnet can be increased. While any process can be used as the specific grain boundary diffusion process, for example, the method described in Japanese Patent No. 6180507 can be used to efficiently introduce heavy rare earth elements into the interior of the magnet, thereby improving the magnetic properties.

[0055] <Magnet of the present invention> Next, the magnet of the present invention will be described. The magnet of the present invention can be obtained by the manufacturing method of the present invention as described above. The magnet of the present invention has a magnetization direction that coincides with the magnetic path, allowing the magnetization potential of the magnet to leak magnetic flux to the outside with high efficiency. In other words, the surface magnetic flux density on the intended surface can be increased.

[0056] The magnet of the present invention preferably has a variation in the amount of leakage magnetic flux in a direction perpendicular to the orientation direction at all points on the surface of no more than ±5% of the average amount of leakage magnetic flux in that direction. Here, the direction perpendicular to the orientation direction at all points on the surface coincides with the depth direction of the cavity 10 .

[0057] The method for measuring this variation will be explained with reference to FIG. 11 shows the circumferentially oriented plate magnet 30 (circumferentially oriented magnet of the present invention) shown in FIG. 8, but the same applies to the radially oriented magnet of the present invention and the concentratedly oriented magnet of the present invention. As shown in Figure 11, the circumferentially oriented magnet 30 of the present invention is divided into 10 equal sections parallel to the direction perpendicular to the orientation direction at all points on the surface (the depth direction of the cavity 10). Then, a cross section perpendicular to that direction is imagined at each section, and the surface magnetic flux density in the direction normal to the cross-sectional outline is measured at that section. The absolute value of the obtained measurements is taken, and the maximum value is taken as the magnitude of the surface magnetic flux density at that section. It is preferable that the maximum value of the surface magnetic flux density is 450 mT or more. The magnetic flux density leaking in the normal direction to the contour is measured using a magnetic measuring device (for example, UHS-1DS manufactured by Nippon Denji Sokki Co., Ltd.) Specifically, the magnetic field sensor probe of the magnetic measuring device is set at a distance of about 0.5 mm from the surface of the magnet of the present invention, and the probe is moved around the outer periphery of the magnet to measure the surface magnetic flux. By performing this operation, the magnetic flux density at all 10 locations is determined, and the simple average value is calculated. Then, the ratio (percentage) of the magnetic flux density values ​​at all locations to the simple average value is calculated. Each ratio calculated here is preferably within ±5% (i.e., 95 to 105%), and more preferably within ±3% (i.e., 97 to 103%). [Example]

[0058] A neodymium magnet powder having the following composition and an average particle size of 3.2 μm was prepared. ·Nd:26.5% by mass ·Pr:4.7% by mass ·Co:0.9% by mass ·B: 1.0% by mass ·Cu:0.1% by mass ·Al: 0.2% by mass ·Zr:0.1 mass% ·Ga:0.1% by mass ·Fe: remainder

[0059] Then, methyl caprylate was added as a lubricant to the mixture at a concentration of 0.07% by mass and thoroughly mixed. After that, the neodymium magnet powder with the lubricant added was mixed at a concentration of 3.6 g / cm 3 The powder was filled into the cavity of the carbon mold shown in FIGS. 1 to 4 at a filling density of 1000 to obtain a powder-filled mold. Next, the powder-filled mold was loaded into an orientation device, and an orientation magnetic field of 2.0 T was applied to the filled neodymium magnet powder without applying pressure, as shown in Figures 5 to 7, to obtain an oriented mold. The oriented mold was then placed in a sintering furnace and sintered in a vacuum at 1000°C for 4 hours to obtain a sintered body. The sintered body was then subjected to aging treatment at 800°C for 30 minutes and then at 520°C for 1 hour. Then, a magnetic field was applied along the orientation direction to obtain the circumferentially oriented, arc-shaped cross-section plate magnet shown in Figure 8, the radially oriented, arc-shaped cross-section plate magnet shown in Figure 9, and the concentratedly oriented, rectangular cross-section plate magnet shown in Figure 10. Photographs of the front, back, and both end faces of the circumferentially oriented, arc-shaped cross-section plate magnet obtained here and shown in Figure 8 are shown in Figure 12. Photographs of the end faces of the radially oriented, arc-shaped cross-section plate magnet obtained here and shown in Figure 9 are shown in Figure 13. Photographs of the front, back, and both end faces of the concentratedly oriented, rectangular cross-section plate magnet obtained here and shown in Figure 10 are shown in Figure 14.

[0060] The surface magnetic flux densities of the resulting circumferentially oriented, arcuate cross-section plate magnet, radially oriented, and concentratedly oriented rectangular cross-section plate magnet were measured, and the maximum surface magnetic flux density was 450 mT or more.

[0061] Next, the orientation direction at each measurement point on the magnet surface was measured by XRD (X-ray diffraction) for each of the circumferentially oriented, radially oriented, and concentratedly oriented rectangular plate magnets. The results are shown in Figure 15. As shown in Figure 15, it was confirmed that the magnets were oriented in roughly the intended direction at all measurement points for all magnets. [Explanation of symbols]

[0062] 1, 1´ mold 5, 5´ Inner surface of mold 10, 10´ cavity 20 Orientation Yoke 22 coils 30 Circumferentially oriented cross-section arc-shaped plate magnet (circumferentially oriented magnet of the present invention) 32 Radially oriented arc-shaped cross-section plate magnet (radially oriented magnet of the present invention) 34 Concentrated Orientation Cross-Section Rectangular Plate Magnet (Concentrated Orientation Magnet of the Present Invention)

Claims

1. Neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant is mixed at 3.4 to 4.0 g / cm 3 a filling step (1) of filling a mold having two or more cavities, including those having a circular arc-shaped cross section, with the powder at a packing density of 1000 to obtain a powder-filled mold; an orientation step (1) in which the powder-filled mold is loaded into a 2N-pole (N is a natural number) orientation yoke so that the arc of the cross section of the cavity is aligned with the orientation direction, and an orientation magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, thereby orienting the neodymium magnet powder and obtaining an oriented mold; a sintering step in which the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside and sintered together with the mold to obtain a sintered body; A magnet manufacturing method comprising the steps of: obtaining a circumferentially oriented plate magnet with an arc-shaped cross section;

2. Neodymium magnet powder having an average particle size of 1.0 to 5.0 μm and containing 1.0 mass % or less of a lubricant is mixed at 3.4 to 4.0 g / cm 3 a filling step (3) of filling a mold having two or more cavities, including those having a rectangular cross section, with the powder at a packing density of 1000 to obtain a powder-filled mold; an orientation step (3) in which the powder-filled mold is loaded into a 2N-pole (N is a natural number) orientation yoke so that one side of the rectangular cross section of the cavity intersects with the orientation direction, and an orientation magnetic field of 1.0 to 5.0 T is applied to the filled neodymium magnet powder without applying pressure, thereby orienting the neodymium magnet powder and obtaining an oriented mold; a sintering step in which the oriented neodymium magnet powder compact is removed from the oriented mold and loaded into a sintering furnace for sintering, or the oriented mold is loaded into a sintering furnace with the oriented neodymium magnet powder compact still inside and sintered together with the mold to obtain a sintered body; A magnet manufacturing method comprising the steps of: obtaining a concentrated orientation rectangular cross-section plate magnet;

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