Neodymium-iron-boron magnetic ring forming device, neodymium-iron-boron magnetic ring and preparation method thereof

Abstract

The invention discloses a neodymium-iron-boron magnetic ring forming device, a neodymium-iron-boron magnetic ring and a preparation method of the neodymium-iron-boron magnetic ring. The neodymium iron boron magnetic ring forming device comprises an upper punch, a female die, a lower outer punch and a lower inner punch. The neodymium-iron-boron magnetic ring forming device can complete multiple procedures such as cold pressing, hot pressing, pre-deformation and thermal deformation extrusion at a time, the process complexity is reduced, repeated heating is avoided, and the performance of the thermal deformation neodymium-iron-boron magnetic ring is improved.

Description

Technical Field

[0001] The invention relates to a NdFeB magnetic ring forming device and also to a NdFeB magnetic ring and a preparation method thereof. Background Art

[0002] The preparation process of hot-deformed NdFeB radiation magnetic ring has the characteristics of near-net forming, and has obvious advantages in manufacturing small-size, large-diameter, thin-walled, high-performance annular magnets. In addition, the microstructure of the hot-deformed NdFeB radiation magnetic ring is composed of nanocrystalline grains, which has better high-temperature magnetic properties. At present, the preparation process of hot-deformed NdFeB radiation magnetic ring mainly includes three processes: cold pressing, hot pressing and hot deformation extrusion of rapid quenching NdFeB powder. Different processes in the prior art usually require separate equipment and matching molds, which makes the process complicated and increases production costs. In addition, in the existing production process, the cold-pressed NdFeB rapid quenching magnetic powder blank is heated for the first time and then hot-pressed to obtain an isotropic hot-pressed blank. After cooling, it is moved to the hot deformation extrusion device and needs to be reheated to a higher temperature to perform hot deformation extrusion on the isotropic hot-pressed blank. This results in the need for repeated heating and heating of the product during the preparation process, and the magnet grains that are in a high-temperature environment for a long time grow and the magnetic properties are reduced.

[0003] CN113996791A discloses a method for manufacturing a high-performance hot-pressed NdFeB magnetic ring, comprising the following steps: S1, cold pressing pre-pressing step: cold pressing the NdFeB magnetic powder to obtain a cold blank; S2, hot pressing step: evenly coating the surface of the cold blank with a solution formed by a composite lubricant A, drying it, placing it in a molding device for hot pressing treatment, and obtaining a hot pressed blank; S3, hot deformation step: evenly coating the surface of the hot pressed blank with a solution formed by a composite lubricant B, drying it, placing it in a molding device for hot deformation treatment, and obtaining a radiation magnetic ring. Although the process can improve the performance of the magnet to a certain extent by combining the composite lubricant with the preparation process, it still needs to be pressed on cold pressing and hot pressing / molding equipment respectively. Summary of the invention

[0004] In view of this, one object of the present invention is to provide a NdFeB magnetic ring forming device, which can complete multiple steps of cold pressing, hot pressing, pre-deformation and hot deformation extrusion at one time, reduce process complexity, avoid repeated heating, and improve the performance of hot-deformed NdFeB magnetic rings. Another object of the present invention is to provide a method for preparing NdFeB magnetic rings. Another object of the present invention is to provide a NdFeB magnetic ring.

[0005] The above purpose is achieved through the following technical solutions.

[0006] In one aspect, the present invention provides a NdFeB magnetic ring forming device, comprising an upper punch, a female die, a lower outer punch and a lower inner punch; wherein:

[0007] A cavity is provided in the female mold for accommodating NdFeB magnetic powder and at least a portion of the upper punch, at least a portion of the lower outer punch and at least a portion of the lower inner punch; the cavity of the female mold has an upper opening and a lower opening;

[0008] The upper punch comprises an upper punch head; the diameter of the upper punch head is adapted to the diameter of the cavity of the female die; the upper punch head is arranged to extend into the cavity of the female die from the upper end opening of the cavity, and to move up and down in the cavity of the female die;

[0009] The lower outer punch comprises a lower outer punch head; the outer diameter of the lower outer punch head is less than or equal to the diameter of the female die; the lower outer punch head is arranged to extend from the lower end opening of the cavity into the cavity of the female die, and move up and down in the cavity of the female die;

[0010] The lower inner punch includes a lower inner punch head; the diameter of the lower inner punch head is less than or equal to the inner diameter of the lower outer punch head; the lower inner punch is configured to extend from the lower end opening of the cavity into the cavity of the female mold and move up and down in the cavity of the female mold.

[0011] According to the NdFeB magnetic ring forming device of the present invention, preferably, the lower outer punch includes a first body and a second body; the first body has a first body cavity; the first body is configured to extend from the lower end opening of the female mold cavity and move up and down in the female mold cavity; the second body has a second body cavity; the second body is inserted into the first body cavity and moves up and down in the first body cavity.

[0012] According to the NdFeB magnetic ring forming device of the present invention, preferably, the lower outer punch also includes a first connecting part and a second connecting part; the first connecting part is sleeved on the bottom periphery of the first body; the first connecting part is located below the bottom of the female mold; the second connecting part is sleeved on the bottom periphery of the second body; the second connecting part is located below the first connecting part.

[0013] According to the NdFeB magnetic ring forming device of the present invention, preferably, the lower inner punch also includes a third connecting portion; the lower inner punch head is configured as a solid structure, and the third connecting portion is vertically connected to the bottom of the lower inner punch head; the lower inner punch head is penetrated into the second body cavity, and moves up and down in the second body cavity; the third connecting portion is located below the second connecting portion.

[0014] According to the NdFeB magnetic ring forming device of the present invention, preferably, the outer diameter of the first body is the same as the diameter of the female mold cavity; the diameter of the first body cavity is the same as the outer diameter of the second body; the diameter of the second body cavity is the same as the diameter of the lower inner punch.

[0015] According to the NdFeB magnetic ring forming device of the present invention, preferably, the height of the second body is greater than the height of the first body, and the length of the second connecting part is less than the length of the first connecting part; the height of the lower inner punch is greater than the height of the second body, and the length of the third connecting part is less than the length of the second connecting part.

[0016] On the other hand, the present invention provides a method for preparing a NdFeB magnetic ring using the NdFeB magnetic ring forming device as described above, comprising the following steps:

[0017] (1) The first body, the second body and a part of the lower inner punch are placed in the cavity of the female mold, wherein the upper end surface of the first body is flush with the upper end surface of the second body, and a distance is formed between the upper end surface of the lower inner punch and the upper end surface of the first body, and the NdFeB blank is placed in the space formed by the two; then the upper punch is moved downward to a position flush with the upper end surface of the first body and the upper end surface of the second body, and the lower inner punch is moved upward to press the NdFeB blank. When the density of the NdFeB blank reaches 3.5-5.5 g / cm 3 Stop when the temperature reaches 0.50000, and obtain a cold pressed green body;

[0018] (2) placing the cold pressed blank at a temperature of 500-700°C, and moving the lower inner punch upward to continue pressing for 10-500s at a pressure of 50-350MPa, and the density of the NdFeB blank reaches at least 7.0g / cm 3 Above, forming a hot pressed green body;

[0019] (3) moving the second body downward to a position flush with the upper end surface of the lower inner punch, heating the temperature to 700-800° C., and moving the second body and the lower inner punch upward at the same time to press the hot pressed green body at a pressure of 100-300 MPa, and maintaining the pressure for 10-500 seconds to form a first pre-deformed green body in the inner cavity of the first body;

[0020] (4) continuing to heat the first pre-deformed body to 800-950° C., maintaining the temperature for 30-500 seconds, moving the first body downward to a position flush with the upper end surfaces of the second body and the lower inner punch, keeping the first body, the second body and the lower inner punch stationary, moving the upper punch downward to press the first pre-deformed body at a pressure of 50-500 MPa, maintaining the pressure for 10-500 seconds, and forming a magnetic ring precursor in the female mold;

[0021] (5) Keeping the second body and the lower inner punch stationary, continue to move the upper punch downward to slowly press the magnetic ring precursor, the pressure is 120 to 300 MPa, the pressing speed is 0.01 to 10 mm / s, and at the same time, the first body presses the lower edge of the magnetic ring, and the pressure applied to the first body is less than 50 MPa.

[0022] According to the preparation method of the present invention, preferably, step (1) also includes: coating the upper punch, the first body, the side and bottom surfaces of the second body and the inner cavity of the female mold with a release agent, wherein the release agent is formed by uniformly mixing molybdenum disulfide powder and graphite powder in a mass ratio of 1:1 to 3.

[0023] The preparation method according to the present invention preferably further comprises the following steps:

[0024] The upper punch is quickly returned to escape from the cavity of the female mold, the second body and the lower inner punch are moved downward to a position flush with the upper end surface of the first body, and the first body, the second body and the lower inner punch are simultaneously moved upward to be flush with the upper edge of the female mold, completing the demolding of the sample to obtain a thermally deformed NdFeB magnetic ring.

[0025] On the other hand, the present invention provides a thermally deformed NdFeB magnetic ring, which is prepared by the above method.

[0026] The NdFeB magnetic ring forming device of the present invention can complete multiple processes such as cold pressing, hot pressing, pre-deformation and hot deformation extrusion at one time, reduce process complexity, avoid repeated heating, and at the same time achieve pre-pressing deformation and improve the performance of hot-deformed NdFeB magnetic rings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a NdFeB magnetic ring forming device of the present invention.

[0028] Figure 2 It is a schematic diagram of the cold pressing process and the hot pressing process of the NdFeB magnetic ring forming device of the present invention.

[0029] Figure 3 It is a schematic diagram of the one-time pre-deformation of the NdFeB magnetic ring forming device of the present invention.

[0030] Figure 4 It is a schematic diagram of secondary pre-deformation of the NdFeB magnetic ring forming device of the present invention.

[0031] Figure 5 It is a schematic diagram of the extrusion process of the NdFeB magnetic ring forming device of the present invention.

[0032] The reference numerals are as follows:

[0033] 1-upper punch, 11-upper punch head; 2-female die; 3-lower outer punch, 311-first body, 312-first connecting part, 321-second body, 322-second connecting part; 4-lower inner punch, 41-lower inner punch head, 42-third connecting part;

[0034] 100-hot pressed green body; 200-first pre-deformed green body; 300-magnetic ring precursor; 400-hot deformed NdFeB magnetic ring. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] <NdFeB magnetic ring forming device>

[0037] The NdFeB magnetic ring forming device of the present invention comprises an upper punch, a female die, a lower outer punch and a lower inner punch.

[0038] Female mold

[0039] The female mold of the present invention is used to provide a place for forming a NdFeB magnetic ring. A cavity is arranged in the female mold, which can accommodate NdFeB magnetic powder and at least a part of the upper punch, at least a part of the lower outer punch and at least a part of the lower inner punch; the cavity of the female mold has an upper end opening and a lower end opening.

[0040] Upward

[0041] The upper punch is arranged on the upper part of the female die, and is arranged as a solid structure. The cross section of the upper punch is an overall "T"-shaped structure. The upper punch is provided with a punch head, and the diameter of the upper punch head is the same as the diameter of the cavity of the female die; the upper punch head is arranged to extend into the cavity of the female die from the upper end opening of the cavity, and move up and down in the cavity of the female die. The upper punch is used to press the NdFeB blank from above when pressing the material; after the pressing is completed, it exits from the upper end opening of the female die cavity.

[0042] Downward thrust

[0043] The lower outer punch comprises a lower outer punch head which can move up and down in the female die and is used to press the NdFeB blank from below when pressing the material; and withdraw from the upper opening of the female die cavity after the pressing is completed.

[0044] The lower outer punch may include a first body and a second body; the first body has a first body cavity; the first body is configured to extend from the lower end opening of the female mold cavity and move up and down in the female mold cavity; the second body has a second body cavity; the second body is inserted into the first body cavity and moves up and down in the first body cavity.

[0045] The lower outer punch may also include a first connecting portion and a second connecting portion; the first connecting portion is sleeved on the bottom periphery of the first body; the first connecting portion is located below the bottom of the female mold; the second connecting portion is sleeved on the bottom periphery of the second body; the second connecting portion is located below the first connecting portion. The first connecting portion and the second connecting portion may connect the first body and the second body to corresponding structures.

[0046] In the present invention, the outer diameter of the first body is the same as the diameter of the female mold cavity; the diameter of the first body cavity is the same as the outer diameter of the second body.

[0047] In the present invention, the height of the second body is greater than the height of the first body, and the length of the second connecting portion is less than the length of the first connecting portion.

[0048] Downward punch

[0049] The lower inner punch may include a lower inner punch head and a third connecting portion, both of which are arranged as solid structures and vertically connected, and the cross section of the lower inner punch generally forms a "T"-shaped structure. The lower inner punch head is arranged as a solid structure, and the third connecting portion is vertically connected to the bottom of the lower inner punch head; the lower inner punch head is arranged in the second body cavity and moves up and down in the second body cavity; the third connecting portion is located below the second connecting portion.

[0050] In the present invention, the diameter of the lower inner punch is the same as the diameter of the second body cavity.

[0051] In the present invention, the height of the lower inner punch is greater than the height of the second body, and the length of the third connecting portion is less than the length of the second connecting portion.

[0052] The diameter of the upper punch (female die cavity) may be 30 to 60 mm, preferably 33 to 55 mm, and more preferably 35 to 52 mm. In some embodiments, the diameter of the upper punch (female die cavity) is 38 mm; in other embodiments, the diameter of the upper punch die (female die cavity) is 50.8 mm.

[0053] The diameter of the first body cavity (the outer diameter of the second body) can be 25 to 50 mm, preferably 28 to 48 mm, and more preferably 30 to 45 mm. In some embodiments, the diameter of the first body cavity (the outer diameter of the second body) is 30.2 mm; in other embodiments, the diameter of the first body cavity (the outer diameter of the second body) is 44.8 mm.

[0054] The diameter of the lower inner punch head (the diameter of the second body cavity) can be 15 to 35 mm, preferably 16 to 32 mm, and more preferably 17 to 28 mm. In some embodiments, the diameter of the lower inner punch head (the diameter of the second body cavity) is 17 mm; in other embodiments, the diameter of the lower inner punch head (the diameter of the second body cavity) is 27.8 mm.

[0055] <Preparation method of NdFeB magnetic ring>

[0056] The NdFeB magnetic ring of the present invention is prepared by the above-mentioned molding device, including the following steps: cold pressing step, hot pressing step, first pre-deformation step, second pre-deformation step, extrusion step. In some embodiments, it also includes a pre-treatment step and a demoulding step. In this way, the above steps can be completed simultaneously on one device, which is described in detail below.

[0057] Preprocessing steps

[0058] In the present invention, the entire cavity of the hot press is sealed and evacuated, and then filled with argon gas to repeatedly clean the interior of the equipment cavity, so that the oxygen content of the gas inside the equipment is less than 50 ppm, preferably less than 30 ppm.

[0059] In the present invention, a release agent can be applied to the upper punch, the first body, the side and bottom surfaces of the second body, and the inner cavity of the female mold, and the release agent is a mixture of molybdenum disulfide powder and graphite powder. The mass ratio of molybdenum disulfide powder to graphite powder can be 1:1-3, preferably 1:1-2, and more preferably 1:1.

[0060] Cold Pressing Steps

[0061] Cold pressing refers to pressing without heating the blank.

[0062] The first body, the second body and a part of the lower inner punch are placed in the cavity of the female mold, wherein the upper end surface of the first body is flush with the upper end surface of the second body, and a distance is formed between the upper end surface of the lower inner punch and the upper end surface of the first body, and the NdFeB blank is placed in the space formed by the two; then the upper punch is moved downward to a position flush with the upper end surface of the first body and the upper end surface of the second body, and the lower inner punch is moved upward to press the NdFeB blank. When the density of the NdFeB blank reaches 3.5-5.5g / cm 3 Stop when the cold pressed green body is obtained.

[0063] In this step, the upper end surfaces of the upper punch, the first body and the second body are flush, and the upper end surface of the lower inner punch is located below the three, so that the blank falls into the cavity of the second body, that is, it is only pressed in the cavity of the second body.

[0064] The blank may contain praseodymium, neodymium, iron, cobalt, gallium and boron. Among them, the content of praseodymium and neodymium is preferably 25-32wt%, more preferably 29-31wt%; the content of iron is preferably 60-65wt%, more preferably 63-65wt%; the content of cobalt is preferably 2-6wt%, more preferably 3.5-5.5wt%; the content of gallium is preferably 0.3-0.6wt%, more preferably 0.4-0.55wt%; the content of boron can be less than 1wt%, preferably 0.8-0.96wt%, more preferably 0.9-0.95wt%.

[0065] The density of the cold pressed green body can be 3.5-5.5 g / cm 3 , preferably 3.5 to 4.5 g / cm 3 , more preferably 3.8 to 4.2 g / cm 3 .

[0066] Hot pressing steps

[0067] The cold pressed blank is placed at a temperature of 500-700°C, and the lower inner punch is moved upward to continue pressing for 10-500s at a pressure of 50-350MPa, and the density of the NdFeB blank reaches at least 7.0g / cm 3 As described above, a hot pressed green body is formed.

[0068] The hot pressing temperature may be 500 to 700°C, preferably 550 to 650°C, and more preferably 600 to 650°C.

[0069] The hot pressing pressure may be 50 to 350 MPa, preferably 100 to 350 MPa, and more preferably 200 to 350 MPa.

[0070] The heat pressing time may be 10 to 500 seconds, preferably 20 to 50 seconds, and more preferably 25 to 35 seconds.

[0071] The density of the hot pressed green body can be greater than 7.0 g / cm 3 , preferably greater than 7.3 g / cm 3 , more preferably greater than 7.5 g / cm 3 .

[0072] First pre-deformation step

[0073] Move the second body downward to a position flush with the upper end surface of the lower inner punch, heat the temperature to 700-800°C, move the second body and the lower inner punch upward at the same time to press the hot-pressed blank at a pressure of 100-300 MPa, maintain the pressure for 10-500 seconds, and form a first pre-deformed blank in the inner cavity of the first body.

[0074] In this step, the upper punch and the first body are kept stationary, and the second body is moved downward to a position flush with the upper end surface of the lower inner punch, so that the hot pressed green body is pressed in the cavity of the first body.

[0075] The temperature of the first pre-deformation may be 700 to 800°C, preferably 720 to 780°C, and more preferably 720 to 750°C.

[0076] The first pre-deformation pressure may be 100 to 300 MPa, preferably 120 to 280 MPa, and more preferably 150 to 250 MPa.

[0077] The holding time may be 10 to 500 seconds, preferably 20 to 40 seconds, and more preferably 25 to 35 seconds.

[0078] Second pre-deformation step

[0079] The first pre-deformed body is further heated to 800-950°C and kept warm for 30-500s, the first body is moved downward to be flush with the upper end surfaces of the second body and the lower inner punch, the first body, the second body and the lower inner punch are kept stationary, the upper punch is moved downward to press the first pre-deformed body at a pressure of 50-500MPa, and the pressure is maintained for 10-500s to form a magnetic ring precursor in the female mold.

[0080] In this step, the first body is moved downward to a position flush with the second body and the upper end surface of the lower inner punch, so that the first pre-deformed blank is pressed in the cavity of the female mold.

[0081] The temperature of the second pre-deformation may be 800 to 950°C, preferably 800 to 900°C, and more preferably 820 to 850°C.

[0082] The insulation temperature may be 30 to 500 seconds, preferably 30 to 100 seconds, and more preferably 50 to 80 seconds.

[0083] The second pre-deformation pressure may be 50 to 500 MPa, preferably 100 to 450 MPa, and more preferably 150 to 400 MPa.

[0084] The holding time may be 10 to 500 seconds, preferably 20 to 40 seconds, and more preferably 25 to 35 seconds.

[0085] In the prior art, since different processes are completed in different equipment, the sample obtained in the previous process needs to be cooled and transferred to the next device to be reheated to the required temperature. Such repeated cooling and reheating can easily reduce the magnetic properties of the magnetic ring. In the present invention, the temperature gradually rises from the hot pressing step to the first pre-deformation step and the second pre-deformation step, so that the temperature can be directly raised when transferring from the previous process to the next process, avoiding repeated heating → cooling → reheating, and improving the magnetic properties of the NdFeB magnetic ring.

[0086] Extrusion steps

[0087] Keep the second body and the lower inner punch stationary, continue to move the upper punch downward to slowly press the magnetic ring precursor, the pressure is 120-300MPa, the pressing speed is 0.01-10mm / s, and at the same time, the first body presses the lower edge of the magnetic ring, and the pressure applied to the first body is less than 50MPa.

[0088] In this step, the upper punch presses the magnetic ring precursor downwards, and at the same time the first body presses the lower edge of the magnetic ring, which ensures that the first body can passively move downwards during the sample extrusion process.

[0089] The extrusion pressure of the upper punch may be 120 to 300 MPa, preferably 150 to 250 MPa, and more preferably 150 to 200 MPa.

[0090] The pressing speed of the upper punch may be 0.01 to 10 mm / s, preferably 0.05 to 5 mm / s, and more preferably 0.08 to 2 mm / s.

[0091] The pressure of the first body extrusion may be less than 50 MPa, preferably less than 10 MPa, and more preferably less than 5 MPa.

[0092] Demolding steps

[0093] The upper punch is quickly returned to escape from the cavity of the female mold, the second body and the lower inner punch are moved downward to a position flush with the upper end surface of the first body, and the first body, the second body and the lower inner punch are simultaneously moved upward to be flush with the upper edge of the female mold, completing the demolding of the sample to obtain a thermally deformed NdFeB magnetic ring.

[0094] <NdFeB Magnetic Ring>

[0095] The NdFeB magnetic ring of the present invention is prepared by the above method.

[0096] Example 1

[0097] like Figure 1As shown, a NdFeB magnetic ring forming device of this embodiment includes an upper punch 1, a female mold 2, a lower outer punch 3 and a lower inner punch 4.

[0098] The female mold 2 is provided with a cavity for accommodating NdFeB magnetic powder and at least a portion of the upper punch 1, at least a portion of the lower outer punch 3 and at least a portion of the lower inner punch 4. The cavity of the female mold 2 has an upper opening and a lower opening.

[0099] The upper punch 1 includes an upper punch head 11, and the cross section of the upper punch 1 is a "T"-shaped structure as a whole. The upper punch head 11 is a solid structure. The diameter of the upper punch head 11 is the same as the diameter of the cavity of the female mold 2. The upper punch head 11 can extend into the cavity of the female mold 2 from the upper end opening of the cavity, and can move up and down in the cavity of the female mold 2.

[0100] The lower outer punch 3 includes a first body 311 , a first connecting portion 312 , a second body 321 and a second connecting portion 322 .

[0101] The first body 311 has a first body cavity. The first body 311 can extend into the cavity from the lower end opening of the cavity of the female mold 2 and move up and down in the cavity. The first connecting portion 312 is sleeved on the bottom periphery of the first body 311. The first connecting portion 312 is located below the bottom of the female mold 2.

[0102] The second body 321 has a second body cavity. The second body 321 can extend into the cavity from the lower end opening of the cavity of the female mold 2 and move up and down in the cavity. The second connecting portion 322 is sleeved on the bottom periphery of the second body 321. The second connecting portion 322 is located below the first connecting portion 312. The outer diameter of the second body 321 matches the diameter of the first body cavity. The height of the second body 321 is greater than the height of the first body 311, and the length of the second connecting portion 322 is less than the length of the first connecting portion 312.

[0103] The lower inner punch 4 includes a lower inner punch head 41 and a third connecting portion 42. The third connecting portion 42 is vertically connected to the bottom of the lower inner punch head 41. The cross-section of the lower inner punch 4 generally forms a "T"-shaped structure. The lower inner punch head 41 is a solid structure. The lower inner punch head 41 can extend into the cavity from the lower end opening of the cavity of the female mold 2, and can move up and down in the cavity of the female mold 2. The third connecting portion 42 is located below the second connecting portion 322. Specifically, the lower inner punch head 41 is arranged in the cavity of the second body 321. The diameter of the lower inner punch head 41 is the same as the diameter of the cavity of the second body. The height of the lower inner punch head 41 is greater than the height of the second body 321, and the length of the third connecting portion 42 is less than the length of the second connecting portion 322.

[0104] In this embodiment, the diameter of the upper punch 11, the diameter of the inner cavity of the female mold 2, and the outer diameter of the first body 311 are 50.8 mm, the diameter of the first body cavity and the outer diameter of the second body 321 are 44.8 mm, and the diameter of the lower inner punch 41 and the diameter of the second body cavity are 27.8 mm.

[0105] Example 2

[0106] In this embodiment, except that the diameter of the upper punch 11, the diameter of the inner cavity of the female mold 2, and the outer diameter of the first body 311 are 38 mm, the diameter of the first body cavity and the outer diameter of the second body 321 are 30.2 mm, and the diameter of the lower inner punch 41 and the diameter of the second body cavity are 17 mm, the rest is the same as in Example 1.

[0107] Example 3

[0108] The device of Example 1 is used to prepare a NdFeB magnetic ring, wherein the composition of the NdFeB blank is the total weight of Pr and Nd (the weight ratio of Pr and Nd is 25:75): 30.6wt%; Fe: 62.98wt%; Co: 5wt%; Ga: 0.5wt%; B: 0.92wt%. The process includes the following steps:

[0109] The entire cavity of the hot press is sealed and evacuated, and then filled with argon gas to repeatedly clean the inside of the equipment cavity to reduce the oxygen content of the gas inside the equipment to less than 50ppm.

[0110] like Figure 1 and 2 As shown, the upper punch 11, the first body 311, the side and bottom surfaces of the second body 321 and the inner cavity of the female mold 2 are coated with a release agent, and the release agent is formed by uniformly mixing molybdenum disulfide powder and graphite powder in a ratio of 1:1. The first body 311, the second body 321 and a part of the lower inner punch 41 are placed in the cavity of the female mold 2, wherein the upper end surface of the first body 311 is flush with the upper end surface of the second body 321, and the upper end surface of the lower inner punch 41 is lower than the upper end surface of the first body 311 and the upper end surface of the second body 321. A distance is formed between the upper end surface of the lower inner punch 41 and the upper end surface of the first body 311, and the NdFeB blank is placed in the space formed by the two; then the upper punch 11 is moved downward to a position flush with the upper end surface of the first body 311 and the upper end surface of the second body 321, and the lower inner punch 4 is moved upward to press the NdFeB blank. When the density of the NdFeB blank reaches 4.0g / cm 3 Stop when the cold pressed green body is obtained.

[0111] The cold pressed blank is placed at a temperature of 600°C, and the lower inner punch 4 is moved upward to continue pressing for 30 seconds at a pressure of 200 MPa. When the density of the NdFeB blank reaches 7.3 g / cm3 The hot pressed green body 100 is formed.

[0112] like Figure 1 and 3 As shown, the second body 321 is moved downward to a position where the upper end surface of the second body 321 is flush with the upper end surface of the lower inner punch 41, the temperature is heated to 720°C, and the second body 321 and the lower inner punch 41 are moved upward at the same time to press the hot-pressed blank 100 at a pressure of 200 MPa. The pressure is maintained for 30 seconds to form a first pre-deformed blank 200 in the inner cavity of the first body 311.

[0113] like Figure 1 and 4 As shown, the first pre-deformed body 200 is further heated to 820°C and kept warm for 60 seconds, the first body 311 is moved downward to a position where the upper end surface of the first body 311 is flush with the upper end surface of the second body 321 and the upper end surface of the lower inner punch 41, the first body 311, the second body 321 and the lower inner punch 41 are kept stationary, the upper punch 11 is moved downward to press the first pre-deformed body 200 at a pressure of 150 MPa, and the pressure is maintained for 30 seconds to form a magnetic ring precursor 300 in the female mold 2.

[0114] like Figure 1 and 5 As shown, the second body 321 and the lower inner punch 41 are kept stationary, and the pressure applied by the first body 311 is less than 5MPa; then the upper punch 11 is moved downward to slowly press the magnetic ring precursor 300, and the pressure applied by the upper punch 11 is 150MPa, and the pressing speed is 0.1mm / s. Since the pressure applied to the first body 311 is small, the first body 311 will move downward during the extrusion of the magnetic ring precursor 300.

[0115] After the extrusion process is completed, the upper punch 11 quickly returns to the cavity of the female mold 2, and the second body 321 and the lower inner punch 41 move downward to a position flush with the upper end surface of the first body 311. The first body 311, the second body 321 and the lower inner punch 41 move upward at the same time to be flush with the upper edge of the female mold 2, completing the sample demolding and obtaining the thermally deformed NdFeB magnetic ring 400.

[0116] Example 4

[0117] The apparatus of Example 2 is used to prepare a NdFeB magnetic ring, wherein the composition of the NdFeB blank is the total weight of Pr and Nd (the weight ratio of Pr and Nd is 25:75): 29.8wt%; Fe: 64.83wt%; Co: 4wt%; Ga: 0.45wt%; B: 0.92wt%. The process includes the following steps:

[0118] The entire cavity of the hot press is sealed and evacuated, and then filled with argon gas to repeatedly clean the inside of the equipment cavity to reduce the oxygen content of the gas inside the equipment to less than 30ppm.

[0119] like Figure 1 and 2 As shown, the upper punch 11, the first body 311, the side and bottom surfaces of the second body 321 and the inner cavity of the female mold 2 are coated with a release agent, and the release agent is formed by uniformly mixing molybdenum disulfide powder and graphite powder in a ratio of 1:1. The first body 311, the second body 321 and a part of the lower inner punch 41 are placed in the cavity of the female mold 2, wherein the upper end surface of the first body 311 is flush with the upper end surface of the second body 321, and the upper end surface of the lower inner punch 41 is lower than the upper end surface of the first body 311 and the upper end surface of the second body 321. A distance is formed between the upper end surface of the lower inner punch 41 and the upper end surface of the first body 311, and the NdFeB blank is placed in the space formed by the two; then the upper punch 11 is moved downward to a position flush with the upper end surface of the first body 311 and the upper end surface of the second body 321, and the lower inner punch 4 is moved upward to press the NdFeB blank. When the density of the NdFeB blank reaches 4.0g / cm 3 Stop when the cold pressed green body is obtained.

[0120] The cold pressed blank is placed at a temperature of 650°C, and the lower inner punch 4 is moved upward to continue pressing for 30 seconds at a pressure of 350 MPa. When the density of the NdFeB blank reaches 7.5 g / cm 3 The hot pressed green body 100 is formed.

[0121] like Figure 1 and 3 As shown, the second body 321 is moved downward to a position where the upper end surface of the second body 321 is flush with the upper end surface of the lower inner punch 41, the temperature is heated to 750°C, and the second body 321 and the lower inner punch 41 are moved upward at the same time to press the hot-pressed blank 100 at a pressure of 200 MPa. The pressure is maintained for 30 seconds to form a first pre-deformed blank 200 in the inner cavity of the first body 311.

[0122] like Figure 1 and 4 As shown, the first pre-deformed body 200 is further heated to 850°C and kept warm for 60 seconds, the first body 311 is moved downward to a position where the upper end surface of the first body 311 is flush with the upper end surface of the second body 321 and the upper end surface of the lower inner punch 41, the first body 311, the second body 321 and the lower inner punch 41 are kept stationary, the upper punch 11 is moved downward to press the first pre-deformed body 200 at a pressure of 150 MPa, and the pressure is maintained for 30 seconds to form a magnetic ring precursor 300 in the female mold 2.

[0123] like Figure 5As shown, the second body 321 and the lower inner punch 41 are kept stationary, and the pressure applied by the first body 311 is less than 10MPa; then the upper punch 11 is moved downward to slowly press the magnetic ring precursor 300. The pressure applied by the upper punch 11 is 200MPa, and the pressing speed is 0.1mm / s. Since the pressure applied to the first body 311 is small, the first body 311 will move downward during the extrusion of the magnetic ring precursor 300.

[0124] After the extrusion process is completed, the upper punch 11 quickly returns to the cavity of the female mold 2, and the second body 321 and the lower inner punch 41 move downward to a position flush with the upper end surface of the first body 311. The first body 311, the second body 321 and the lower inner punch 41 move upward at the same time to be flush with the upper edge of the female mold 2, completing the sample demolding and obtaining the thermally deformed NdFeB magnetic ring 400.

[0125] Comparative Example 1

[0126] The method of Example 1 of the prior art CN113996791A is adopted to perform cold pre-pressing, hot pressing and hot deformation steps on the NdFeB blank with the same composition as Example 3 of the present application to obtain a NdFeB magnetic ring.

[0127] Comparative Example 2

[0128] The method of Example 1 of the prior art CN113996791A is adopted to perform cold pre-pressing, hot pressing and hot deformation steps on the NdFeB blank with the same composition as Example 4 of the present application to obtain a NdFeB magnetic ring.

[0129] The thermally deformed NdFeB magnetic rings obtained in Examples 3 and 4 and Comparative Examples 1 and 2 were tested using the following method:

[0130] The sample to be tested was cut into a cubic test sample with a diameter of 2×2×2mm using an electric spark wire cutting machine, and the remanent magnetism B of the magnet was measured using a vibrating sample magnetometer. r 、Maximum magnetic energy product (BH) max , intrinsic coercivity H cJ Equivalent magnetic properties.

[0131] The results are shown in Table 1.

[0132] Table 1

[0133]

[0134] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be thought of by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A NdFeB magnetic ring forming device, characterized in that: It includes upper punch, female die, lower outer punch and lower inner punch; among them, A cavity is provided in the female mold for accommodating NdFeB magnetic powder and at least a portion of the upper punch, at least a portion of the lower outer punch and at least a portion of the lower inner punch; the cavity of the female mold has an upper opening and a lower opening; The upper punch comprises an upper punch head; the diameter of the upper punch head is adapted to the diameter of the cavity of the female die; the upper punch head is arranged to extend into the cavity of the female die from the upper end opening of the cavity, and to move up and down in the cavity of the female die; The lower outer punch comprises a lower outer punch head; the outer diameter of the lower outer punch head is less than or equal to the diameter of the female die; the lower outer punch head is arranged to extend from the lower end opening of the cavity into the cavity of the female die, and move up and down in the cavity of the female die; The lower inner punch includes a lower inner punch head; the diameter of the lower inner punch head is less than or equal to the inner diameter of the lower outer punch head; the lower inner punch is configured to extend from the lower end opening of the cavity into the cavity of the female mold and move up and down in the cavity of the female mold.

2. The NdFeB magnetic ring forming device according to claim 1, characterized in that: The lower outer punch includes a first body and a second body; the first body has a first body cavity; the first body is configured to extend from the lower end opening of the female mold cavity and move up and down in the female mold cavity; the second body has a second body cavity; the second body is inserted into the first body cavity and moves up and down in the first body cavity.

3. The NdFeB magnetic ring forming device according to claim 2, characterized in that: The lower outer punch also includes a first connecting part and a second connecting part; the first connecting part is sleeved on the bottom periphery of the first body; the first connecting part is located below the bottom of the female mold; the second connecting part is sleeved on the bottom periphery of the second body; the second connecting part is located below the first connecting part.

4. The NdFeB magnetic ring forming device according to claim 3, characterized in that: The lower inner punch also includes a third connecting portion; the lower inner punch head is configured as a solid structure, and the third connecting portion is vertically connected to the bottom of the lower inner punch head; the lower inner punch head is inserted into the second body cavity and moves up and down in the second body cavity; the third connecting portion is located below the second connecting portion.

5. The NdFeB magnetic ring forming device according to claim 4, characterized in that: The outer diameter of the first body is the same as the diameter of the female die cavity; the diameter of the first body cavity is the same as the outer diameter of the second body; the diameter of the second body cavity is the same as the diameter of the lower inner punch.

6. The NdFeB magnetic ring forming device according to claim 5, characterized in that: The height of the second body is greater than that of the first body, and the length of the second connection portion is less than that of the first connection portion; the height of the third body is greater than that of the second body, and the length of the third connection portion is less than that of the second connection portion.

7. A method for preparing a NdFeB magnetic ring using the NdFeB magnetic ring forming device according to any one of claims 2 to 6, characterized in that: The steps include: (1) The first body, the second body and a part of the lower inner punch are placed in the cavity of the female mold, wherein the upper end surface of the first body is flush with the upper end surface of the second body, and a distance is formed between the upper end surface of the lower inner punch and the upper end surface of the first body, and the NdFeB blank is placed in the space formed by the two; then the upper punch is moved downward to a position flush with the upper end surface of the first body and the upper end surface of the second body, and the lower inner punch is moved upward to press the NdFeB blank. When the density of the NdFeB blank reaches 3.5-5.5 g / cm 3 Stop when the temperature reaches 0.50000, and obtain a cold pressed green body; (2) placing the cold pressed blank at a temperature of 500-700°C, and moving the lower inner punch upward to continue pressing for 10-500s at a pressure of 50-350MPa, and the density of the NdFeB blank reaches at least 7.0g / cm 3 Above, forming a hot pressed green body; (3) moving the second body downward to a position flush with the upper end surface of the lower inner punch, heating the temperature to 700-800° C., and moving the second body and the lower inner punch upward at the same time to press the hot pressed green body at a pressure of 100-300 MPa, and maintaining the pressure for 10-500 seconds to form a first pre-deformed green body in the inner cavity of the first body; (4) continuing to heat the first pre-deformed body to 800-950° C., maintaining the temperature for 30-500 seconds, moving the first body downward to a position flush with the upper end surfaces of the second body and the lower inner punch, keeping the first body, the second body and the lower inner punch stationary, moving the upper punch downward to press the first pre-deformed body at a pressure of 50-500 MPa, maintaining the pressure for 10-500 seconds, and forming a magnetic ring precursor in the female mold; (5) Keeping the second body and the lower inner punch stationary, continue to move the upper punch downward to slowly press the magnetic ring precursor, the pressure is 120 to 300 MPa, the pressing speed is 0.01 to 10 mm / s, and at the same time, the first body presses the lower edge of the magnetic ring, and the pressure applied to the first body is less than 50 MPa.

8. The preparation method according to claim 7, characterized in that: Step (1) also includes: coating the upper punch, the first body, the side and bottom surfaces of the second body, and the inner cavity of the female mold with a release agent, wherein the release agent is formed by uniformly mixing molybdenum disulfide powder and graphite powder in a mass ratio of 1:1 to 3.

9. The preparation method according to claim 8, characterized in that: The following steps are also included: The upper punch is quickly returned to escape from the cavity of the female mold, the second body and the lower inner punch are moved downward to a position flush with the upper end surface of the first body, and the first body, the second body and the lower inner punch are simultaneously moved upward to be flush with the upper edge of the female mold, completing the demolding of the sample to obtain a thermally deformed NdFeB magnetic ring.

10. A thermally deformed NdFeB magnetic ring, characterized in that: The NdFeB magnetic ring is obtained by the preparation method described in any one of claims 7 to 9.

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