A polar anisotropic oriented magnet and its manufacturing method and application

Abstract

The present invention discloses a polar anisotropic oriented magnet and a manufacturing method and application thereof. A mold for preparing a polar anisotropic oriented arc-shaped magnet comprises: a female mold, comprising a first alloy region and a second alloy region, the magnetic permeability of the second alloy being stronger than that of the first alloy; and a chamber, the chamber being arc-shaped and located in the first alloy region. Using the mold, an arc-shaped magnet with the same orientation as half a pole or one pole of a polar anisotropic circular ring magnet can be manufactured, thereby obtaining an arc-shaped magnet with an ideal polar anisotropic orientation. The arc-shaped magnets can be spliced ​​into annular magnets, and the surface magnetic flux density of the annular magnets is distributed in a sinusoidal waveform. When such annular magnet is used as a rotor, a motor with low cogging torque can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of NdFeB sintered magnets, relates to a method for manufacturing NdFeB sintered magnets, and particularly relates to a polar anisotropic oriented magnet and a manufacturing method and application thereof. Background Art

[0002] Since its discovery, NdFeB permanent magnet materials have been widely used in communications, medical, automotive, electronics, aviation and other fields due to their excellent magnetic properties and high cost performance. NdFeB materials are divided into axially oriented magnets, radially oriented magnets, radially oriented magnets (or polar anisotropic magnets) and other forms according to different orientations. Compared with axially oriented and radially oriented magnets, the surface flux density of polar anisotropic magnets has a sinusoidal waveform, so it can reduce the size of the motor and reduce the motor cogging torque.

[0003] Patent document 1 (Japanese Patent Publication No. 6-024174) discloses a method for manufacturing anisotropic circular magnets. During the pressing process, a magnetic field with alternating N and S poles is applied to the magnetic ring to perform multi-level orientation of the magnet, such as Figure 1 As shown. After sintering, a polar anisotropic magnet is obtained. In this preparation method, during the sintering process, the arrangement of the grains will automatically change due to the magnetic field orientation, so that the crystal magnetic anisotropic axis of the grains is arranged along the curvature of the magnetic field lines, making the shrinkage rate of the annular embryo at the magnetic pole orientation position higher than that at the magnetic pole intersection position, causing the embryo outline to become a polygon instead of a circle, as shown in the figure. Figure 2 shown.

[0004] Patent document 2 (CN104465061B) discloses a method for solving the contour deformation of anisotropic circular ring embryos. By designing the annular cavity of the mold to have a wider space corresponding to the magnetic pole orientation position and a narrower space corresponding to the magnetic pole junction position, the embryo can be closer to a true circle after the subsequent sintering is completed. However, this method still causes product cracking due to the large difference in the radial and tangential shrinkage rates and thermal expansion coefficients of the product during the sintering process.

[0005] In order to solve the deformation and cracking problems of polar anisotropic ring magnets, it is usually necessary to first manufacture an arc-shaped magnet, and then stick the arc-shaped magnet on a yoke to form a ring to form a rotary machine. In order to achieve a sinusoidal effect on the surface magnetic flux density of the polar anisotropic ring magnet, the inlet and outlet of the internal magnetic lines of force of the arc-shaped magnet need to have different angles relative to the same reference plane. In addition, arc-shaped magnets cannot be produced using the mold and method in patent document 1. Because in the mold provided in patent document 1, it is very difficult to configure the magnetic field generating coil and adjust the strength, it is difficult to obtain a polar anisotropic arc-shaped magnet with an ideal orientation.

[0006] Patent document 3 (CN108352768A) discloses an arc-shaped magnet having a polar anisotropic orientation, but does not disclose a specific method for manufacturing the polar anisotropic arc-shaped magnet.

[0007] Patent document 4 (CN103299381A) discloses a method for manufacturing arc-shaped magnets with polar anisotropy orientation. By placing magnetic blocks at different positions in a parallel magnetic field and changing the direction of the magnetic field, the magnetic field lines inside the magnet can be changed. However, the method mentioned in the patent document is different from the ideal polar anisotropy orientation. When multiple arc-shaped magnets are spliced ​​into a ring, the surface magnetic flux density of the ring is low and the cogging torque cannot be significantly reduced.

[0008] Therefore, how to obtain arc-shaped magnets with ideal polar anisotropic magnet orientation to significantly reduce the motor cogging torque has become a technical problem that needs to be solved urgently. Summary of the invention

[0009] In order to improve the above technical problems, the present invention provides a mold for preparing a magnet with anisotropic orientation, the mold comprising:

[0010] A female mold including a first alloy region and a second alloy region, wherein the magnetic conductivity of the second alloy is stronger than that of the first alloy;

[0011] The chamber is arc-shaped and is located in the first alloy zone.

[0012] According to an embodiment of the present invention, the female mold is a rectangular body, the first alloy area is in an inverted Y shape in the rectangular body, and the second alloy is filled on both sides of the inverted Y-shaped edge line. Preferably, the filling is symmetrical filling.

[0013] According to an embodiment of the present invention, the inverted Y-shaped sideline includes two oblique sidelines and two horizontal sidelines. Preferably, the two oblique sidelines and the two horizontal sidelines are axially symmetrical with the horizontal line as the axis.

[0014] According to an embodiment of the present invention, the first alloy zone includes region A, region B and region C, wherein region A is a rectangular zone surrounded by two intersection points of the hypotenuse and the sideline of the female mold, and two vertices close to the female mold; region B is a trapezoidal zone surrounded by two intersection points of the hypotenuse and the horizontal sideline, and two intersection points of the hypotenuse and the sideline of the female mold; region C is a rectangular zone surrounded by two intersection points of the hypotenuse and the horizontal sideline, and two intersection points of the horizontal sideline and the sideline of the female mold.

[0015] According to an embodiment of the present invention, the chamber is completely within the area B, thereby ensuring that sufficient magnetic lines of force pass through the arc-shaped chamber.

[0016] According to an embodiment of the present invention, the second alloy zone includes region D and region E, and both region D and region E are regions surrounded by the intersection of the hypotenuse and the female mold sideline, the intersection of the hypotenuse and the horizontal sideline, the intersection of the horizontal sideline intersecting the hypotenuse and the female mold sideline, and the female mold vertex closest to the horizontal sideline. That is, with the horizontal line as the axis, region D and region E are axially symmetrical.

[0017] According to an embodiment of the present invention, the first alloy is a non-magnetic alloy or an alloy with weak magnetic conductivity, preferably a non-magnetic alloy, which can better form the desired magnetic field line direction. For example, the non-magnetic alloy is preferably 304 stainless steel, 70MN carbon steel or G60 steel material.

[0018] According to an embodiment of the present invention, the second alloy is an alloy with strong magnetic conductivity; for example, it is 45# steel or chrome 12 steel material.

[0019] According to an embodiment of the present invention, the cross section of the chamber is a closed arc surface formed by an inner arc, an outer arc and two side walls. The inner arc refers to an arc close to the center of the circle, and the outer arc refers to an arc away from the center of the circle. Those skilled in the art can adjust the height, thickness, etc. of the chamber according to the requirements of product specifications.

[0020] According to an embodiment of the present invention, the chamber is completely located within the region B.

[0021] According to an embodiment of the present invention, the heights of the first alloy zone, the second alloy zone and the chamber are equal.

[0022] According to an embodiment of the present invention, the mold further comprises an N pole and an S pole, and the N pole and the S pole respectively comprise a pole head and a magnetic field coil wound on the pole head. Preferably, the N pole and the S pole are respectively arranged on both sides of the female mold, so that the female mold is placed in a parallel magnetic field formed by the magnetic field coil. Preferably, the side area of ​​the female mold accounts for more than 70% of the area of ​​the N pole or the S pole, for example, more than 75%, and for example, more than 80%.

[0023] According to an embodiment of the present invention, the parallel magnetic field passes through the chamber, and the entrance and exit of the magnetic lines of force inside the chamber are both at a certain angle relative to the closed arc surface. Preferably, the angle difference between the exit and entrance of the magnetic lines of force is less than 70°, for example, 5-60°, exemplified by 10°, 20°, 30°, 40°, 50°, 60°.

[0024] Preferably, the distance between the two straight sides of the highly magnetically permeable alloy and the non-magnetic / weakly magnetically permeable alloy is greater than half the length of the arc-shaped chamber in the magnetic field direction, where the length in the magnetic field direction refers to the projection length of the arc-shaped chamber in the magnetic field direction.

[0025] The present invention also provides a method for manufacturing a magnet with extremely anisotropic orientation, comprising the following steps:

[0026] 1) Prepare or fabricate magnetic powder of a Nd-Fe-B based sintered magnet;

[0027] 2) Load the magnetic powder into the above-mentioned mold, orient it in a parallel magnetic field and press it into a compact to obtain a green compact;

[0028] 3) Sinter and temper the green compact, and after cooling, obtain a magnet with extremely anisotropic orientation.

[0029] According to an embodiment of the present invention, in step 1), the magnetic powder comprises R-Fe-B-M alloy jet mill powder and a lubricant, and the mass ratio of the lubricant to the R-Fe-B-M alloy jet mill powder is 0.05-1:100, preferably 0.1-0.5:100, and exemplary values are 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100. Among them, the lubricant can be selected from lubricants known in the art.

[0030] According to an embodiment of the present invention, in the R-Fe-B-M alloy jet mill powder, R represents at least one element among rare earth elements, and M is at least one or several of Co, Ga, Cu, Al, Zr, and Ti.

[0031] Preferably, R is selected from at least one of Nd, Pr, Dy, Tb, La, Ce, Pr, Pm, Eu, Sc, Gd, Ho, Er, Tm, Yb, Lu, and Y, and preferably at least one of Nd, Pr, and Dy.

[0032] Preferably, the content of R is 26 wt% < R < 35 wt%, for example 28 wt% ≤ R ≤ 33 wt%, and exemplary values are 28 wt%, 30 wt%, 30.5 wt%, 31 wt%, 33 wt%.

[0033] Preferably, the content of B is 0.5-1.5 wt%, for example 0.8-1.3 wt%, and exemplary values are 0.9 wt%, 0.98 wt%, 1.0 wt%, 1.1 wt%, 1.3 wt%.

[0034] Preferably, the M includes Co, Ga and Cu, and optionally includes or excludes Al, Zr and Ti. For example, the content of Co is 0.5-3.0wt%, the content of Ga is 0.05-0.4wt%, the content of Cu is 0.05-0.5wt%, the content of Al is 0-1.5wt%, and the content of Zr or Ti is 0-0.3wt%. Exemplarily, M includes 1.0wt% Co, 0.10wt% Ga, 0.15wt% Cu, 0.5wt% Al, and 0.12wt% Zr.

[0035] Preferably, the R-Fe-BM alloy jet mill powder contains iron and inevitable impurities except for the elements R, B and M.

[0036] According to an embodiment of the present invention, in step (1), the average particle size of the R-Fe-BM alloy air flow milled powder is 1-6 μm, for example 2-4 μm, exemplified by 2 μm, 2.5 μm, 3 μm, 3.1 μm, 3.5 μm, 4 μm.

[0037] According to an embodiment of the present invention, in step (1), the preparation process of the R-Fe-BM alloy air flow milled powder includes: mixing R and M metals with ferroboron to obtain an alloy after melting, pouring, and rapid cooling; and crushing and air flow milling the alloy to obtain the R-Fe-BM alloy air flow milled powder.

[0038] For example, the melting may be performed by a melting method known in the art, preferably high frequency melting in an inert atmosphere (such as argon or nitrogen).

[0039] For example, the pouring and rapid cooling operations may be operations known in the art, and preferably the molten melt is poured onto a rapid cooling roller to obtain the alloy.

[0040] For example, the pulverization may be a pulverization method known in the art, preferably hydrogenation pulverization.

[0041] According to an embodiment of the present invention, in step (1), the magnetic powder is uniformly mixed by the R-Fe-BM alloy air flow mill and the lubricant in the above proportions, for example, the mixing time is 0.1-3h, preferably 0.5-2.5h, and exemplarily 0.5h, 1h, 1.5h, 2h, 2.5h, 3h.

[0042] According to an embodiment of the present invention, in step (2), the density of the compact is ≥3.5 g / cm 3 , for example, density ≥ 4g / cm 3 .

[0043] According to an embodiment of the present invention, in step (3), the sintering temperature is 1000-1130° C., such as 1030-1100° C., exemplarily 1030° C., 1050° C., 1060° C. Further, the sintering time is 4-8h, such as 5-7h, exemplarily 5h, 6h, 7h.

[0044] According to an embodiment of the present invention, in step (3), the tempering treatment includes at least one stage of tempering treatment, preferably two stages of tempering treatment.

[0045] For example, the temperature of the first tempering treatment is 800-950° C., such as 850-930° C., exemplified by 850° C., 880° C., 900° C., 920° C. Further, the time of the first tempering treatment is 1-5h, such as 2-4h, exemplified by 2h, 3h, 4h.

[0046] For example, the temperature of the second tempering treatment is 450-600° C., such as 480-550° C., exemplified by 480° C., 500° C., 520° C., 550° C., 580° C. Further, the time of the second tempering treatment is 3-8 hours, such as 4-7 hours, exemplified by 4 hours, 5 hours, 6 hours, 7 hours.

[0047] According to an embodiment of the present invention, in step (3), the cooling is natural cooling.

[0048] According to an embodiment of the present invention, the method may further optionally include step (4) of subjecting the anisotropically oriented magnet to a grain boundary diffusion treatment.

[0049] According to an embodiment of the present invention, in step (4), the grain boundary diffusion treatment can be performed by a coating method, a thermal spraying method, a vapor deposition method or a dipping method, etc., preferably a thermal spraying method.

[0050] According to an embodiment of the present invention, the method for manufacturing the polar anisotropic oriented magnet comprises the following steps:

[0051] 1) Preparing or preparing magnetic powder of NdFeB sintered magnet: adding 0.1-0.5% lubricant by weight to R-Fe-BM alloy jet mill powder and mixing for 0.1-3h;

[0052] Among them, in the R-Fe-B-M alloy, R represents at least one element in rare earth elements, the content of R is 26 wt% < R < 35 wt%, the content of B is 0.8 wt% to 1.3 wt%, M includes Co, Ga and Cu, and optionally includes or does not include Al, Zr, Ti; the content of Co is 0.5 - 3.0 wt%, the content of Ga is 0.05 - 0.4 wt%, the content of Cu is 0.05 - 0.5 wt%, the content of Al is 0 - 1.5 wt%, the content of Zr or Ti is 0 - 0.3 wt%, and the balance is iron and inevitable impurities;

[0053] 2) Load the magnetic powder into the above-mentioned mold, orient and compress it in a parallel magnetic field to obtain a green compact;

[0054] 3) Sinter and temper the green compact, and after cooling, obtain a magnet with extremely anisotropic orientation.

[0055] The present invention also provides a magnet with extremely anisotropic orientation, and there is an angular difference between the entrance and the exit of the magnetic force lines of the magnet. Preferably, the angular difference between the exit and the entrance of the magnetic force lines is less than 70°, for example, it is 5 - 60°, and exemplarily it is 10°, 20°, 30°, 40°, 50°, 60°.

[0056] According to the embodiment of the present invention, the shape of the magnet with extremely anisotropic orientation is arc-shaped, preferably the same as the shape of the above-mentioned chamber.

[0057] Preferably, the arc-shaped magnet with extremely anisotropic orientation is prepared by the above method.

[0058] The present invention also provides an annular magnet, which is composed of the magnets with extremely anisotropic orientation.

[0059] The present invention also provides a preparation method of the annular magnet, including the following steps: combining the magnets with extremely anisotropic orientation into an annular magnet.

[0060] The present invention also provides the application of the magnet with extremely anisotropic orientation and / or the annular magnet in reducing the cogging torque of a motor. For example, it is used as a rotor of a motor.

[0061] The present invention also provides a motor rotor, which contains the magnet with extremely anisotropic orientation and / or the annular magnet.

[0062] The present invention also provides a motor, which contains the above-mentioned motor rotor.

[0063] The beneficial effects of the present invention:

[0064] The present invention provides a mold for preparing anisotropic circular arc magnets, which utilizes the shape of the female mold and the cavity and the difference in the magnetic permeability of the alloy so that the inlet and outlet of the magnetic lines of force of the magnet in the cavity present different angles relative to the cross section of the cavity. Using this mold, an arc magnet with the same orientation as half a pole or one pole of anisotropic circular annular magnet can be manufactured, and an arc magnet with ideal anisotropic orientation can be obtained. The arc magnets can be spliced ​​into annular magnets, and the surface magnetic flux density of the annular magnets is distributed in a sinusoidal waveform. When this annular magnet is used as a rotor, a motor with low cogging torque can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Patent document 1 discloses a method for manufacturing a polar anisotropic ring magnet by a pressing process.

[0066] Figure 2 This is a polar anisotropic ring magnet with an orientation number of eight poles disclosed in Patent Document 1.

[0067] Figure 3 This is a three-dimensional diagram of the arc-shaped magnet in Example 3.

[0068] Figure 4 This is a cross-sectional view of the orientation direction of the arc-shaped magnet in Example 3.

[0069] Figure 5 This is a top view of the mold structure of Example 1.

[0070] Figure 6 This is a cross-sectional view of the mold of Example 1 along a plane parallel to the central axis of the two poles.

[0071] Figure 7 This is a top view of the mold structure of Example 2.

[0072] Figure 8 Schematic diagram of the cross-sectional shape of the chamber of Example 1.

[0073] Fig. 9 Schematic diagram of the magnetic field when a parallel magnetic field is applied to the mold shown in Example 1.

[0074] Fig.10 Schematic diagram of the magnetic field when a parallel magnetic field is applied to the mold shown in Example 2.

[0075] Fig.11 Schematic diagram of the positional relationship between the inclined edge where the first alloy zone and the second alloy zone contact each other and the cavity in the mold shown in Example 1.

[0076] Fig.12 This is another schematic diagram of the positional relationship between the beveled edge where the first alloy zone and the second alloy zone contact each other and the cavity in the mold.

[0077] Fig.13 This is a schematic diagram of the mold structure used in Comparative Example 1.

[0078] Fig.14 Graph showing surface magnetic flux density of sintered magnets of Example 4, Example 5 and Comparative Example 1 after assembly.

[0079] Fig.15 A schematic diagram showing the calculation of the entrance and exit angles of the magnetic lines of force in Example 1.

[0080] Fig.16 Schematic diagram showing a circular magnet with polar anisotropy.

[0081] Reference numerals:

[0082] 10-arc-shaped magnet, 11-first side wall, 12-second side wall, 13-outer arc, 14-inner arc, 20-female mold, 21-first magnetic field coil, 22-second magnetic field coil, 23-pole head, 24-first alloy zone, 25-second alloy zone, 26-chamber. DETAILED DESCRIPTION

[0083] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0084] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0085] Example 1

[0086] like Figure 5 As shown, the mold for preparing anisotropically oriented arc-shaped magnets includes:

[0087] The female mold 20 includes a first alloy region 24 and a second alloy region 25, wherein the magnetic conductivity of the second alloy is stronger than that of the first alloy; the female mold 20 is a rectangular body, wherein the first alloy region 24 is in an inverted Y shape in the rectangular body, and the second alloy is symmetrically filled on both sides of the inverted Y-shaped edge line. The inverted Y-shaped edge line includes two oblique edge lines and two horizontal edge lines, and the two oblique edge lines and the two horizontal edge lines are axially symmetrical with the horizontal line as the axis.

[0088] The chamber 26 is arc-shaped and is located in the first alloy zone 24 .

[0089] The first alloy zone 24 includes region A, region B and region C, wherein region A is a rectangular region surrounded by two intersection points of the hypotenuse and the side line of the female mold, and two vertices close to the female mold; region B is a trapezoidal region surrounded by two intersection points of the hypotenuse and the horizontal side line, and two intersection points of the hypotenuse and the side line of the female mold; region C is a rectangular region surrounded by two intersection points of the hypotenuse and the horizontal side line, and two intersection points of the horizontal side line and the side line of the female mold.

[0090] The chamber 26 is completely within the region B, thereby ensuring that sufficient magnetic lines of force pass through the arc-shaped chamber. Fig.11 The figure shows the positional relationship between the hypotenuse of the first alloy region 24 and the second alloy region 25 and the chamber 26. It can be seen from the figure that the length of the hypotenuse of the first alloy region 24 and the second alloy region 25 in the direction perpendicular to the parallel magnetic field exceeds the chamber 26. This ensures that the magnetic field lines inside the arc-shaped magnet meet the requirements of polar anisotropy.

[0091] The second alloy region 25 includes region D and region E, and both region D and region E are surrounded by the intersection of the hypotenuse and the female mold sideline, the intersection of the hypotenuse and the horizontal sideline, the intersection of the horizontal sideline intersecting the hypotenuse and the female mold sideline, and the female mold vertex closest to the horizontal sideline. That is, with the horizontal line as the axis, region D and region E are axially symmetrical.

[0092] The first alloy is a non-magnetic alloy, which can better form the required magnetic field line direction, such as 304 stainless steel, 70MN carbon steel or G60 steel.

[0093] The second alloy is an alloy with strong magnetic conductivity, such as 45# steel or chrome 12 steel.

[0094] Figure 6 It is a cross-sectional view of the mold along a plane parallel to the central axis of the two poles. The cavity 26 is at the same height as the first alloy zone 24 and the second alloy zone 25.

[0095] like Figure 8 As shown, the cross section of the chamber 26 is a closed arc surface formed by the inner arc 14, the outer arc 13, the first side wall 11 and the second side wall 12. The inner arc 14 refers to the arc close to the center of the circle, and the outer arc 13 refers to the arc away from the center of the circle. The shape of the chamber 26 is similar to a part of the shape of the annular magnet. Taking into account the shrinkage and deformation of the magnet after sintering, the outer arc 13, the inner arc 14 and the first side wall 11 and the second side wall 12 of the chamber 26 are appropriately adjusted within the scope of the present invention, and the size of the finished product is 0.7-0.9 of the size of the mold cavity, so that the arc-shaped magnets after sintering are closer to the ideal annular magnet after splicing.

[0096] The mold further includes an N pole and an S pole, each of which includes a pole head 23, a first magnetic field coil 21 wound on the N pole pole head, and a second magnetic field coil 22 wound on the S pole pole head. The N pole and the S pole are respectively arranged on both sides of the female mold 20, so that the female mold 20 is placed in a parallel magnetic field formed by the magnetic field coils. The side area of ​​the female mold 20 accounts for more than 70% of the area of ​​the N pole or the S pole.

[0097] Fig. 9 For Figure 5 The schematic diagram of the magnetic field when a parallel magnetic field is applied to the mold shown. The first magnetic field coil 21 and the second magnetic field coil 22 generate a magnetic field, and the magnetic field passes through the strong magnetic alloy, the straight edge of the strong magnetic alloy and the non-magnetic alloy, and the straight edge of the non-magnetic alloy and the pole head in a straight line. When the magnetic field passes through the oblique edge of the strong magnetic alloy and the non-magnetic alloy, it passes at a certain angle. Therefore, through the design of the mold 20, the magnetic lines of force inside the arc-shaped magnet pass at a certain arc, and such a magnet has the same orientation as the polar anisotropic circular magnet.

[0098] The parallel magnetic field passes through the chamber, and the entrance and exit of the magnetic lines of force inside the chamber are both at a certain angle relative to the closed arc surface. Fig.15 In the figure, the angle between the entrance of the magnetic lines of force inside the chamber and the closed arc surface is recorded as α, the angle between the exit of the magnetic lines of force and the closed arc surface is recorded as β, and the angle difference between the exit of the magnetic lines of force and its entrance is γ=|α-β|<70°.

[0099] The distance between the two straight sides of the highly permeable magnetic alloy and the non-permeable / weakly permeable magnetic alloy is greater than half the length of the arc-shaped chamber in the magnetic field direction, and the length in the magnetic field direction refers to the projection length of the arc-shaped chamber in the magnetic field direction.

[0100] Example 2

[0101] Figure 7 Another schematic diagram of the mold structure for preparing anisotropically oriented arc-shaped magnets. Figure 5 The main difference is that the opening of the inverted Y-shaped mold faces the opposite direction, and the position of the arc-shaped cavity in the mold also changes accordingly. By adjusting the position of the arc-shaped cavity, the bending direction of the magnetic field lines inside the magnet can be changed. Fig.10 For Figure 7 Schematic diagram of the magnetic field conditions when a parallel magnetic field is applied to the mold shown.

[0102] Fig. 9 The shown is Figure 7The schematic diagram of another example of the magnetic field inside the magnet when a parallel magnetic field is applied to the mold shown. The first magnetic field coil 21 and the second magnetic field coil 22 generate a magnetic field, and the magnetic field passes through the strong magnetic alloy, the straight edge of the strong magnetic alloy and the non-magnetic alloy, and the straight edge of the non-magnetic alloy and the pole head in a straight line. When the magnetic field passes through the oblique edges of the strong magnetic alloy and the non-magnetic alloy, it passes at an arc of a certain angle. By adjusting the position of the strong magnetic alloy and the non-magnetic alloy in the chamber 26 and the mold 20, the bending direction of the magnetic lines of force in the arc-shaped magnet can be changed. Fig. 9 Compared with the two magnets, only the bending direction of the magnetic lines of force in the magnets is different. After the two magnets are assembled into a ring-shaped magnet, N and S aggregation can occur, and finally the surface magnetic flux density distribution forms a sinusoidal waveform.

[0103] Example 3

[0104] Figure 3 and Figure 4 To adopt Figure 7 The three-dimensional and cross-sectional views of the arc-shaped magnet 10 prepared by the mold shown in the figure. 11' and 12' are the two end faces of the magnet, and 13' and 14' are the two arc faces of the magnet. From the orientation of the magnet, it can be seen that relative to the end face 12', the entrance and exit of the magnetic field lines inside the magnet present different angles relative to the end face 12'. By assembling two arc-shaped magnets 10 oriented in this way, Fig.16 The structure shown is the same as one pole of the anisotropic circular magnet (as shown by the oblique line in the figure). It should be noted that as long as the magnets can form N poles or S poles gathered together, the surface magnetic flux density distribution can be formed into a sinusoidal waveform, and there is no need to pay attention to the bending direction of the magnetic lines of force inside the magnet. In addition, the bending direction of the magnetic lines of force inside the magnet can be changed by adjusting the position and shape of the cavity in the mold. Assembling all the arc-shaped magnets 10 into a ring can form an anisotropic circular magnet.

[0105] Fig.12 The figure shows another schematic diagram of the positional relationship between the hypotenuse of the first alloy zone and the second alloy zone in the mold and the cavity. It can be seen from the figure that the length of the hypotenuse of the strong magnetic conductive alloy 25 and the non-magnetic conductive alloy 24 in the direction perpendicular to the parallel magnetic field does not exceed the arc-shaped cavity 26. The magnetic lines of force inside the arc-shaped magnet produced in this way do not meet the requirements of a complete polar anisotropic magnet and cannot meet the requirements of the present invention.

[0106] Example 4

[0107] The alloy is made by high-frequency melting NdPr, Dy, Co, Al, Fe, Cu, Ga, Zr and ferroboron with a purity of at least 99% by weight in an argon atmosphere, and pouring the melt onto a quenching roller. The mass percentage of the alloy is 30% NdPr, 0.5% Dy, 1.0% Co, 0.5% Al, 0.15% Cu, 0.10% Ga, 0.12% Zr, 0.98% B, and the remainder is iron and unavoidable impurities. The alloy is hydrogenated and crushed into coarse powder, and then the coarse powder is jet-milled to obtain magnetic powder with an average particle size of 3.1 μm. A lubricant accounting for 0.2 wt% of the magnetic powder is added to the above-mentioned jet-milled magnetic powder and mixed for 2 hours. Figure 5 The blank is pressed and formed under the orientation magnetic field and mold shown in the figure to obtain the blank. The first alloy material of the mold is 304 stainless steel, and the second alloy material is 45# steel. Then the blank is placed in a vacuum sintering furnace and sintered at 1060℃ for 6h. After the insulation is completed, it is cooled and a primary tempering treatment is performed at 900℃ for 3h. A secondary tempering treatment is performed at 520℃ for 5h. After cooling out of the furnace, a sintered NdFeB magnet is obtained. The magnet after sintering heat treatment is processed into a magnet with an outer arc radius of 88mm, an inner arc radius of 75mm and a center angle of 7.5°, thereby obtaining an arc-shaped polar anisotropic sintered magnet.

[0108] Example 5

[0109] The same formula and powder making process as in Example 4 were used to obtain magnetic powder, and then Figure 7 The magnetic powder is pressed into shape under the oriented magnetic field and mold shown to obtain a blank. The first alloy material of the mold is G60 steel, and the second alloy material is chromium 12 steel. Then the blank is placed in a vacuum sintering furnace and sintered at 1060°C for 6 hours. After the insulation is completed, it is cooled and a primary tempering treatment is performed at 900°C for 3 hours. A secondary tempering treatment is performed at 520°C for 5 hours. After cooling out of the furnace, a sintered NdFeB magnet is obtained. The magnet after sintering heat treatment is processed into a magnet with an outer arc radius of 88mm, an inner arc radius of 75mm and a center angle of 7.5°, thereby obtaining an arc-shaped polar anisotropic sintered magnet.

[0110] Comparative Example 1

[0111] The same formula and powder making process as in Example 4 were used to obtain magnetic powder, and then Fig.13 The orientation magnetic field and the mold are shown. Fig.13 The figure shows a schematic diagram of the orientation of magnetic powder in a curved cavity directly in a conventional mold and parallel magnetic field. The entire mold 20 has: a pair of symmetrical magnetic field coils 21, 22, and a pole head 23, forming a parallel magnetic field M. The non-magnetic conductive alloy area 24' and the strong magnetic conductive alloy area 25' are parallel to form a female mold. In the female mold, there is an arc-shaped cavity 26' composed of an outer arc, an inner arc and two side walls.

[0112] The material of the non-magnetic alloy area 24' of the mold is 70MN carbon steel, and the material of the strong magnetic alloy area 25' is 45# steel. Then sinter at 1060℃ for 6h. After the insulation is completed, it is cooled and tempered at 900℃ for 3h. The secondary tempering is carried out at 520℃ for 5h. After cooling and taking out of the furnace, a sintered NdFeB magnet is obtained. The magnet after sintering heat treatment is processed into a magnet with an outer arc radius of 88mm, an inner arc radius of 75mm and a center angle of 7.5°, thereby obtaining an arc-shaped sintered magnet.

[0113] The arc-shaped magnets of Example 4, Example 5 and Comparative Example 1 were assembled into a ring, and the surface magnetic flux density of the magnets was tested after magnetization. The test results are as follows: Fig.14 As shown. Fig.14 It can be seen that the surface magnetic flux density waveforms of Examples 4 and 5 present a sine wave, which is consistent with the waveform of the rational polar anisotropic ring magnet. The surface magnetic flux density waveform of Comparative Example 1 presents a trapezoidal shape. Therefore, a rotor with low cogging torque can be obtained by using the magnets of Examples 4 and 5.

[0114] according to Fig.15 As shown, a 3*3 small piece was processed for the inlet and outlet of Example 4 and Comparative Example 1, and the magnetic flux in the X and Y directions was tested to calculate the angle of the magnetic force line relative to the side 12. The test results are shown in Table 1:

[0115] Table 1: Comparison of magnetic lines of force between Example 4 and Comparative Example 1

[0116] Entrance angle α(°) Outlet angle β(°) Example 4 27 75 Comparative Example 1 0 0

[0117] From Example 4, it can be seen that the entrance and exit angles of the magnetic lines of force are different, indicating that the magnetic lines of force of the magnet produced by the method of the present invention are deflected inside the magnet. The waveform of the magnetic flux density on the surface of such a magnet will present a sine wave, which can reduce the cogging torque of the rotor.

[0118] Example 6

[0119] The alloy is made by high-frequency melting NdPr, Dy, Co, Al, Fe, Cu, Ga, Zr and ferroboron with a purity of at least 99% by weight in an argon atmosphere, and pouring the melt onto a quenching roller. The mass percentage of the alloy is 29.5% NdPr, 0.5% Dy, 1.5% Co, 0.1% Al, 0.17% Cu, 0.10% Ga, 0.18% Ti, 0.98% B, and the remainder is iron and unavoidable impurities. The alloy is hydrogenated and crushed into coarse powder, and then the coarse powder is jet-milled to obtain magnetic powder with an average particle size of 2.9μm. A lubricant accounting for 0.2wt% of the mass of the magnetic powder is added to the above-mentioned jet-milled magnetic powder and mixed for 2h. Figure 7The green body is then pressed and formed under the orientation magnetic field and mold shown in the figure to obtain a green body. Then the green body is placed in a vacuum sintering furnace and sintered at 1050°C for 6 hours. After the insulation is completed, it is cooled and subjected to a primary tempering treatment at 900°C for 3 hours. A secondary tempering treatment is performed at 500°C for 5 hours. After cooling out of the furnace, a sintered NdFeB magnet is obtained. The magnet after sintering heat treatment is processed into a magnet with an outer arc radius of 80mm, an inner arc radius of 72mm and a center angle of 5°, thereby obtaining an arc-shaped polar anisotropic sintered magnet. This product is recorded as A1.

[0120] After degreasing and pickling, the polar anisotropic sintered magnet was treated with Tb grain boundary diffusion, and the diffusion amount of Tb was 0.5wt%. In this embodiment, the grain boundary diffusion was treated by thermal spraying, so that the magnet surface was sprayed with Tb with a thickness of 20μm. The treated sample was recorded as A2. The results of measuring the magnetic performance indicators of magnets A1 and A2 are shown in Table 2.

[0121] Table 2: Magnetic properties test of samples A1 and A2

[0122]

[0123] After diffusion treatment of polar anisotropic magnets, the remanence of the magnets decreased by about 0.025 T. The coercive force increased by 648 kA / m.

[0124] The non-diffused anisotropic magnet performance of sample A1 is 50M, and the product Hcj is too low to meet the motor's temperature resistance (180°C temperature resistance requirement). After using diffusion technology, the Hcj of sample A2 reaches 1798kA / m, which can meet the motor's use requirements.

[0125] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A mold for preparing a magnet with anisotropic orientation, characterized in that: The mold comprises: A female mold including a first alloy region and a second alloy region, wherein the magnetic conductivity of the second alloy is stronger than that of the first alloy; The female mold is a rectangular body, the first alloy area is in an inverted Y shape in the rectangular body, and the second alloy is filled on both sides of the inverted Y-shaped edge line; the inverted Y-shaped edge line includes two oblique lines and two horizontal lines, and the two oblique lines and the two horizontal lines are axially symmetrical with the horizontal line as the axis; The first alloy region includes region A, region B and region C, wherein region A is a rectangular region surrounded by two intersections of the hypotenuse and the sideline of the female mold, and two vertices close to the female mold; region B is a trapezoidal region surrounded by two intersections of the hypotenuse and the horizontal sideline, and two intersections of the hypotenuse and the sideline of the female mold; region C is a rectangular region surrounded by two intersections of the hypotenuse and the horizontal sideline, and two intersections of the horizontal sideline and the sideline of the female mold; The second alloy zone includes region D and region E, and both region D and region E are regions surrounded by the intersection of the hypotenuse and the sideline of the female mold, the intersection of the hypotenuse and the horizontal sideline, the intersection of the horizontal sideline intersecting the hypotenuse and the sideline of the female mold, and the vertex of the female mold closest to the horizontal sideline; with the horizontal line as the axis, region D and region E are axially symmetrical; The chamber is arc-shaped and is located in the first alloy zone; the cross section of the chamber is a closed arc surface formed by an inner arc, an outer arc and two side walls; wherein the inner arc refers to an arc close to the center of the circle, and the outer arc refers to an arc far away from the center of the circle.

2. The mold according to claim 1, characterized in that: The first alloy is a non-magnetic alloy or an alloy with weak magnetic conductivity.

3. The mold according to claim 1, characterized in that: The second alloy is an alloy with strong magnetic conductivity.

4. The mold according to claim 1, characterized in that: The chamber is completely located within the region B.

5. The mold according to claim 1, characterized in that: The first alloy zone, the second alloy zone and the chamber have the same height.

6. The mold according to claim 1, characterized in that: The mold further includes an N pole and an S pole, and the N pole and the S pole respectively include a pole head and a magnetic field coil wound around the pole head.

7. The mold according to claim 6, characterized in that: The N pole and the S pole are respectively arranged on both sides of the female mold, so that the female mold is placed in a parallel magnetic field formed by the magnetic field coil.

8. The mold according to claim 7, characterized in that: The side surface area of ​​the female mold accounts for more than 70% of the area of ​​the N pole or the S pole.

9. The mold according to claim 7, characterized in that: The parallel magnetic field passes through the chamber, and the entrance and exit of the magnetic lines of force inside the chamber are both at a certain angle relative to the closed arc surface, and the angle difference between the exit and entrance of the magnetic lines of force is less than 70°.

10. The mold according to claim 2, characterized in that: The distance between the two straight sides of the highly permeable magnetic alloy and the non-permeable / weakly permeable magnetic alloy is greater than half the length of the arc-shaped chamber in the magnetic field direction, where the length in the magnetic field direction refers to the projection length of the arc-shaped chamber in the magnetic field direction.

11. A method for producing a magnet with anisotropic orientation, characterized in that: The steps include: 1) Preparing or preparing magnetic powder of NdFeB sintered magnet; 2) loading the magnetic powder into the mold according to any one of claims 1 to 10, orienting and pressing in a parallel magnetic field to obtain a green compact; 3) The green compact is sintered and tempered, and after cooling, a magnet with anisotropic orientation is obtained.

12. The manufacturing method according to claim 11, characterized in that: In step 1), the magnetic powder includes R-Fe-BM alloy air flow milled powder and lubricant, and the mass ratio of the lubricant to the R-Fe-BM alloy air flow milled powder is 0.05-1:

100.

13. The manufacturing method according to claim 12, characterized in that: The mass ratio of the lubricant to the R-Fe-B-M alloy airflow milled powder is 0.1-0.5:

100.

14. The manufacturing method according to claim 12, characterized in that: In the R-Fe-B-M alloy airflow milled powder, R represents at least one element among rare earth elements, and M is at least one or several of Co, Ga, Cu, Al, Zr, and Ti.

15. The manufacturing method according to claim 12, characterized in that: R is selected from at least one of Nd, Pr, Dy, Tb, La, Ce, Pr, Pm, Eu, Sc, Gd, Ho, Er, Tm, Yb, Lu, and Y.

16. The manufacturing method according to claim 15, characterized in that: R is at least one of Nd, Pr, and Dy.

17. The manufacturing method according to any one of claims 12 to 16, characterized in that: The content of R is 26wt% < R < 35wt%, and the content of B is 0.5-1.5wt%.

18. The manufacturing method according to claim 12, characterized in that: M includes Co, Ga, and Cu, and optionally includes or does not include Al, Zr, and Ti.

19. The manufacturing method according to claim 18, characterized in that: The content of Co is 0.5-3.0wt%, the content of Ga is 0.05-0.4wt%, the content of Cu is 0.05-0.5wt%, the content of Al is 0-1.5wt%, and the content of Zr or Ti is 0-0.3wt%.

20. The manufacturing method according to claim 12, characterized in that: In the R-Fe-B-M alloy airflow milled powder, except for the elements R, B, and M, the rest are iron and inevitable impurities.

21. The manufacturing method according to claim 12, characterized in that: In step 1), the average particle size of the R-Fe-B-M alloy airflow milled powder is 1-6μm.

22. The manufacturing method according to claim 12, characterized in that: In step 1), the preparation process of the R-Fe-B-M alloy airflow milled powder includes: mixing and melting R and M metals with ferroboron, casting, and then rapidly cooling to obtain an alloy; pulverizing and airflow grinding the alloy to obtain the R-Fe-B-M alloy airflow milled powder.

23. The manufacturing method according to claim 11, characterized in that: In step 3), the sintering temperature is 1000-1130°C, and the sintering time is 4-8h.

24. The manufacturing method according to claim 11, characterized in that: In step 3), the tempering treatment includes at least one-stage tempering treatment.

25. The manufacturing method according to claim 11, characterized in that: In step 3), the tempering treatment is a two-stage tempering treatment.

26. The manufacturing method according to claim 11, characterized in that: The method may also optionally include step 4) of performing grain boundary diffusion treatment on the extremely anisotropic oriented magnet.

27. A magnet with anisotropic orientation, characterized in that: There is an angular difference between the inlet and the outlet of the magnetic force lines of the magnet, and the angular difference is 10-60°; The extremely anisotropic oriented magnet is prepared by the mold according to any one of claims 1-10 or by the manufacturing method according to any one of claims 11-26.

28. The polar anisotropically oriented magnet according to claim 27, characterized in that: The shape of the extremely anisotropic oriented magnet is the same as the shape of the cavity in any one of claims 1-10.

29. A ring-shaped magnet, characterized in that: The annular magnet is composed of the extremely anisotropic oriented magnets according to any one of claims 27-28.

30. Application of the extremely anisotropic oriented magnet according to any one of claims 27-28 and / or the annular magnet according to claim 29 in reducing the cogging torque of a motor.

31. The use according to claim 30, characterized in that The extremely anisotropic oriented magnet or the annular magnet is used as the rotor of a motor.

32. A motor rotor containing the extremely anisotropic oriented magnet according to any one of claims 27-28 and / or the annular magnet according to claim 29.

33. A motor, the motor containing the motor rotor according to claim 32.

Images