Method for manufacturing a hot deformed magnet and preheating device

Abstract

The application discloses a hot deformation magnet preparation method and a preheating device. The hot deformation magnet preparation method comprises the following steps: cold pressing magnetic powder to obtain a cold-pressed blank, wherein the density of the cold-pressed blank is 4.5-5.5 g / cm 3 The cold-pressed blank is hot pressed in a hot-pressing concave die at 600-800 DEG C to obtain a pre-pressed blank, the pre-pressed blank is preheated, the temperature of the pre-pressed blank after preheating is 850-950 DEG C, the pre-pressed blank after preheating is transferred into a hot deformation concave die, the temperature of the hot deformation concave die is 750-800 DEG C, the temperature of an upper punch is kept at 600-700 DEG C, the upper punch is made to enter the hot deformation concave die to hot deform the pre-pressed blank, and a magnet is obtained. In the hot deformation process of the magnet, the temperature of the pre-pressed blank is higher than that of the concave die, and the temperature of the concave die is higher than that of the upper punch, so that the precipitation of rare earth-rich phases in the pre-pressed blank is reduced, the loss of the concave die is reduced, and the service life of the die is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magnet preparation, and particularly relates to a hot deformation magnet preparation method and a preheating device. BACKGROUND

[0002] Rare earth permanent magnet materials have been widely used in many fields such as motors, computers, automobiles, instruments, household appliances, aerospace, etc. Compared with the traditional powder metallurgy sintered magnet process, the hot deformation process for preparing magnets obtains deformation texture inside the magnet through hot deformation, and anisotropic magnets can be obtained without magnetic field orientation. In addition, compared with the micron-sized grains of sintered magnets, hot deformation magnets have a nano-grain structure, and have better corrosion resistance and high temperature resistance.

[0003] However, the yield of neodymium iron boron magnets prepared by the hot deformation process accounts for a very low proportion in the entire rare earth permanent magnet industry, one of the reasons being that the hot deformation process for preparing magnets causes serious loss of mold material, and the mold needs to be replaced after about 1000 magnets are prepared. The mold is very expensive, and frequent downtime caused by mold replacement results in low production efficiency.

[0004] The inventors have found that during hot deformation, the pre-compacted body is heated by the concave die. In order to meet the temperature requirements of the hot deformation of the magnet, the temperature of the concave die is relatively high, for example, the temperature of the concave die is 850-900℃. The pre-compacted body of the magnet contains a low-melting-point rare earth-rich phase. During hot deformation, the rare earth-rich phase in the pre-compacted body has been liquefied. The hot extrusion process causes a large amount of rare earth-rich phase to precipitate. The rare earth-rich phase is in contact with the hard alloy inner wall of the concave die for a long time at high temperature, which causes corrosion of the inner wall of the concave die, thereby causing loss of mold material and affecting the service life of the mold. SUMMARY

[0005] Based on the above problems, the present application provides a hot deformation magnet preparation method and a preheating device, which reduces the precipitation of rare earth-rich phase in the pre-compacted body during hot deformation and improves the service life of the mold.

[0006] In order to achieve the above effects, the technical scheme adopted by the present application is as follows:

[0007] A hot deformation magnet preparation method, comprising:

[0008] cold pressing the magnetic powder to obtain a cold-pressed blank, the density of the cold-pressed blank being 4.5-5.5 g / cm 3 ,

[0009] hot pressing the cold-pressed blank in a hot pressing concave die at 600-800℃ to obtain a pre-compacted body;

[0010] preheating the pre-compacted body, the temperature of the pre-compacted body after preheating being 850-950℃;

[0011] transferring the preheated pre-pressed blank into a hot deformation die, the temperature of the hot deformation die being 750-800℃;

[0012] The temperature of the upper punch is kept at 600-700℃, and the upper punch is moved into the hot deformation die to perform hot deformation on the preheated pre-pressed blank, thereby obtaining the magnet.

[0013] According to some embodiments of the present application, the preheating of the pre-pressed blank comprises heating the pre-pressed blank at 850-950℃ for 1-10min.

[0014] According to some embodiments of the present application, the preheated pre-pressed blank is transferred into the hot deformation die within 5s.

[0015] According to some embodiments of the present application, the temperature of the pre-pressed blank decreases by ≤15℃ during the transferring of the preheated pre-pressed blank into the hot deformation die.

[0016] According to some embodiments of the present application, the hot deformation of the pre-pressed blank is performed by floating pressing.

[0017] According to some embodiments of the present application, the moving speed V1 of the upper punch is 0.2-1.0mm / s, and the moving speed of the hot deformation die is:

[0018]

[0019] wherein K is 0.8-1.2, D is the inner diameter of the hot deformation die, d is the outer diameter of the upper punch, and V1 is the moving speed of the upper punch.

[0020] One embodiment of the present application provides a preheating device, comprising:

[0021] a heater provided with a heating cavity with two open ends;

[0022] a first ejector rod slidingly arranged at one end of the heater, the first ejector rod being capable of closing the open end of the heater;

[0023] a second ejector rod slidingly arranged at the other end of the heater, the second ejector rod being capable of closing the other open end of the heater;

[0024] a storage device for storing pre-pressed blanks, the first ejector rod being capable of pushing the pre-pressed blanks on the storage device into the heating cavity;

[0025] a turning wheel arranged below the second ejector rod, the pre-pressed blanks being rotated when passing through the turning wheel.

[0026] This application uses a hot deformation process to prepare magnets. During the hot deformation process, the temperature of the pre-pressed blank is higher than the temperature of the hot deformation die, and the temperature of the hot deformation die is higher than the temperature of the upper punch, so as to reduce the precipitation of rare earth-rich phases in the pre-pressed blank, reduce the wear on the hot deformation die, and improve the die life. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without exceeding the scope of protection claimed by this application.

[0028] Figure 1 These are micrographs of the magnets in embodiments of this application;

[0029] Figure 2 This is a schematic diagram of the method for preparing a hot-deformable magnet according to an embodiment of this application;

[0030] Figure 3 This is a schematic diagram of the thermal deformation process in an embodiment of this application;

[0031] Figure 4 This is a schematic diagram of the preheating device according to an embodiment of this application;

[0032] Figure 5 This is a side view of the preheating device according to an embodiment of this application;

[0033] Figure 6 This is the working process of the preheating device in the embodiments of this application. Figure 1 ;

[0034] Figure 7 This is the working process of the preheating device in the embodiments of this application. Figure 2 ;

[0035] Figure 8 This is the working process of the preheating device in the embodiments of this application. Figure 3 . Detailed Implementation

[0036] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] Traditional hot deformation processes for preparing hot-deformable magnets include:

[0038] 1. Cold press the magnetic powder to obtain a cold-pressed blank;

[0039] 2. hot-pressing the cold-pressed blank to obtain a pre-pressed blank;

[0040] 3. hot-deforming the pre-pressed blank in a concave die at 850-900℃ to obtain a cup-shaped magnet.

[0041] The pre-pressed blank is heated by the concave die during hot-deformation, the temperature of the concave die is 850-900℃, the material of the concave die is cemented carbide, and the high temperature makes the strength and hardness of the cemented carbide rapidly decay. During the hot-deformation process, the rare earth-rich phase in the pre-pressed blank melts and is extruded out, and the extruded rare earth-rich phase corrodes the inner wall of the concave die, affecting the service life of the concave die.

[0042] As shown in FIG. 1, the microstructure of the magnet includes a main phase and a rare earth-rich phase, and the c-axis is the easy magnetization direction. Figure 1 As shown in FIG. 2, the area ratio of the main phase grains that do not melt at the hot-deformation process temperature is high, and the area ratio of the rare earth-rich phase that corrodes the inner wall of the concave die is small. Figure 1 The black part is a lath-shaped main phase, the white part is a rare earth-rich phase, and the c-axis is the easy magnetization direction.

[0043] The inventors found that when the temperature of the concave die is appropriately lower than the temperature of the pre-pressed blank, the main phase grains on the surface of the pre-pressed blank can cool the rare earth-rich phase around the main phase through contact with the inner wall of the concave die, the cooled rare earth-rich phase is in a viscous state or even returns to a solid state, thereby forming a diaphragm to prevent the liquid rare earth-rich phase inside the pre-pressed blank from being extruded out.

[0044] As shown in FIG. 3, the embodiment of the present application proposes a hot-deformation magnet preparation method, which comprises: Figure 2

[0045] S1. cold-pressing the magnetic powder in a room-temperature atmospheric environment to obtain a cold-pressed blank, the density of the cold-pressed blank being 4.5-5.5 g / cm 3 .

[0046] S2. hot-pressing the cold-pressed blank in a hot-pressing concave die at 600-800℃ in an argon atmosphere to obtain a pre-pressed blank. Optionally, the density of the pre-pressed blank is 7.5-7.6 g / cm 3 .

[0047] S3. preheating the pre-pressed blank, the temperature of the pre-pressed blank after preheating being 850-950℃.

[0048] S4. transferring the preheated pre-pressed blank to a hot-deformation concave die, the temperature of the hot-deformation concave die being 750-800℃.

[0049] As shown in FIG. 4, the embodiment of the present application proposes a hot-deformation magnet preparation method, which comprises: Figure 3 ​As shown, the hot deformation device can be selected from existing hot deformation devices, and the hot deformation device can heat the hot deformation die 30 and the upper punch 10 to keep the hot deformation die 30 and the upper punch 10 at a preset temperature. The pre-pressed blank 40 after preheating is transferred to the lower punch 20, and the lower punch 20 and the pre-pressed blank 40 are lowered synchronously, and the pre-pressed blank 40 enters the hot deformation die 30.

[0050] During the process of transferring the preheated pre-pressed blank to the hot deformation die, the temperature of the pre-pressed blank will decrease slightly, and when the pre-pressed blank enters the hot deformation die, the temperature of the hot deformation die should be lower than that of the pre-pressed blank, and the temperature difference between the pre-pressed blank and the hot deformation die is in the range of 50-200°C.

[0051] The temperature of the preheated pre-pressed blank cooperates with the temperature of the hot deformation die to make the pre-pressed blank in the hot deformation die meet the temperature required for hot deformation, and at the same time, since the temperature of the hot deformation die is lower than that of the preheated pre-pressed blank, the rare earth-rich phase precipitated from the pre-pressed blank is reduced during hot deformation to reduce the corrosion of the hot deformation die.

[0052] S5, the temperature of the upper punch is kept at 600-700°C, and the upper punch 10 enters the hot deformation die 30 to perform hot deformation on the preheated pre-pressed blank 40 to obtain the magnet 50.

[0053] Keeping the temperature of the upper punch at 600-700°C can avoid cracks in the pre-pressed blank during hot deformation.

[0054] During the process of preparing the magnet by the hot deformation process in this embodiment, the temperature arrangement is: the temperature of the preheated pre-pressed blank > the temperature of the hot deformation die > the temperature of the upper punch. Since the temperature of the hot deformation die is relatively low, a small amount of rare earth-rich phase precipitated from the pre-pressed blank solidifies after contacting the inner wall of the hot deformation die to prevent more rare earth-rich phase from precipitating inside the pre-pressed blank, reduce the corrosion of the hot deformation die, improve the service life of the hot deformation die, and improve the production efficiency.

[0055] Optionally, the bottom of the cup-shaped magnet is cut off as needed to obtain a magnetic ring.

[0056] In some embodiments, preheating the pre-pressed blank includes heating the pre-pressed blank at 850-950°C for 1-10 min. The preheating time of the pre-pressed blank is determined according to the size of the pre-pressed blank to make the pre-pressed blank fully heated, facilitating the subsequent hot deformation.

[0057] In some embodiments, the preheated pre-pressed blank is transferred to the hot deformation die within 5 seconds. Too much time consumption in the process of transferring the preheated pre-pressed blank to the hot deformation die will cause the temperature of the pre-pressed blank to decrease too much, affecting the subsequent hot deformation.

[0058] In some embodiments, the temperature of the pre-pressed blank decreases by ≤15℃ during the process of transferring the pre-pressed blank to the hot deformation die, so as to ensure that the temperature difference between the pre-pressed blank and the hot deformation die is in the range of 50-200℃ when the pre-pressed blank enters the hot deformation die.

[0059] In some embodiments, the hot deformation of the pre-pressed blank is performed by floating pressing. When only the up-and-down pressing mode is used, the friction between the inner wall of the hot deformation die and the pre-pressed blank can cause the pressing force of the up punch to increase, and can cause cracks in the magnet. By using floating pressing of the hot deformation die, the hot deformation die moves upward together with the part of the pre-pressed blank that contacts the hot deformation die, so as to avoid the influence of the friction between the inner wall of the hot deformation die and the pre-pressed blank on the pressing.

[0060] In some embodiments, the down-moving speed of the up punch V1 is 0.2-1.0 mm / s, and the moving speed of the upward movement of the hot deformation die is:

[0061]

[0062] wherein K is 1.0-1.2, D is the inner diameter of the hot deformation die, and d is the outer diameter of the up punch.

[0063] The down-moving speed of the up punch V1 can be determined according to the size of the magnet after hot deformation, for example,

[0064] when the outer diameter of the magnet is 40-50 mm and the single-side wall thickness is 4-6 mm, the down-moving speed of the up punch V1 is 0.2-0.4 mm / s;

[0065] when the outer diameter of the magnet is 30-40 mm and the single-side wall thickness is 3-4 mm, the down-moving speed of the up punch V1 is 0.5-0.6 mm / s;

[0066] when the outer diameter of the magnet is 20-30 mm and the single-side wall thickness is 2-3 mm, the down-moving speed of the up punch V1 is 0.9-1.0 mm / s.

[0067] When the coefficient K is determined by experiment, K can be selected as 0.8, 0.9, 1.0, 1.1 and 1.2. When K=1 is selected at the beginning of the preparation of the hot deformation sample, if no cracks are found on the surface of the sample, then the value is used, and if cracks are found on the surface of the sample, then K needs to be adjusted to 0.8, 0.9, 1.1 or 1.2 to ensure that no cracks are found on the surface of the sample.

[0068] During the pressing process, the down-moving speed of the up punch V1 and the upward moving speed of the hot deformation die V2 are matched, so that the deformation rate of the inner part of the ring wall (the part not in contact with the die) and the deformation rate of the edge part of the ring wall (the part in contact with the die) during the hot deformation of the pre-pressed blank are the same, so as to avoid cracks in the pre-pressed blank due to the difference in the deformation rates of the inner part and the edge part.

[0069] Optionally, the hot deformation of the pre-compacted blank is completed within 30 seconds, so as to ensure that the pre-compacted blank maintains the optimal process temperature during the hot deformation.

[0070] As shown in Figure 4 , the embodiment of the present application provides a preheating device 100 for preheating the pre-compacted blank. The preheating device 100 comprises a heater 1, a first ejector rod 2, a second ejector rod 3, a storage device 4, and a turnover wheel 5.

[0071] The heater 1 is provided with a heating cavity with two open ends. Optionally, the axis of the heater 1 is parallel to the horizontal direction. The heater 1 is provided with a temperature sensor 11 for detecting the temperature in the heating cavity. The pre-compacted blank 40 enters the heating cavity for preheating.

[0072] The first ejector rod 2 is slidingly arranged at one end of the heater 1, and can close the open end of the heater 1. The second ejector rod 3 is slidingly arranged at the other end of the heater 1, and can close the other open end of the heater 1. The open end of the heater 1 closed by the first ejector rod 2 is the feeding port, and the open end of the heater 1 closed by the second ejector rod 3 is the discharging port.

[0073] As shown in Figure 5 , a plurality of pre-compacted blanks are arranged in the storage device 4 in sequence. The storage device 4 is arranged obliquely, and the first ejector rod 2 can push the pre-compacted blank 40 at the bottom end of the storage device 4 into the heating cavity.

[0074] The turnover wheel 5 is arranged below the second ejector rod 3, and the pre-compacted blank 40 rotates when passing through the turnover wheel 5.

[0075] As shown in Figure 6 , after the pre-compacted blank 40 in the heater 1 is heated, the second ejector rod 3 slides away from the first ejector rod 2, the discharging port of the heater 1 is opened, the first ejector rod 2 slides towards the second ejector rod 3, pushes one pre-compacted blank in the heating cavity out, the preheated pre-compacted blank rotates when passing through the turnover wheel 5, the axis of the pre-compacted blank 40 changes from the horizontal direction to the vertical direction, and the pre-compacted blank 40 slides onto the supporting plate 6. The pre-compacted blank 40 on the supporting plate 6 is quickly transferred to the hot deformation concave die.

[0076] As shown in Figure 7 , the second ejector rod 3 slides towards the first ejector rod 2 to close the discharging port of the heater 1, and the first ejector rod 2 slides away from the second ejector rod 3. The first ejector rod 2 slides to the side of the storage device 4 away from the heater 1, the feeding port of the heater 1 is opened, and the pre-compacted blank at the bottom end of the storage device 4 slides to the feeding position.

[0077] As shown in Figure 8 , the first ejector rod 2 slides towards the second ejector rod 3 to push the pre-compacted blank at the feeding position into the heating cavity and close the feeding port of the heater 1.

[0078] Optionally, the reservoir 4 is provided with a displacement sensor 41 and a blocking plate 42. The displacement sensor 41 is used to detect whether the first ejector rod 2 moves to the side of the reservoir 4 away from the heater 1. The blocking plate 42 is slidably arranged on the bottom plate of the reservoir 4. When the displacement sensor 41 detects that the first ejector rod 2 moves to the side of the reservoir 4 away from the heater 1, the blocking plate 42 moves downward, the pre-pressed compact at the lowermost end of the reservoir 4 falls to the feeding position, and the blocking plate 42 moves upward to block the movement of the remaining pre-pressed compacts in the reservoir 4.

[0079] In the hot deformation process in the embodiment, the temperature arrangement is: the temperature of the pre-pressed compact after preheating > the temperature of the hot deformation concave die > the temperature of the upper punch. Through the cooperation of the moving speed of the upper punch and the moving speed of the hot deformation concave die, the amount of rare earth-rich phase precipitated during the hot deformation of the pre-pressed compact is reduced, and the service life of the hot deformation concave die is improved.

[0080] Embodiment 1

[0081] MQU-F magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%).

[0082] 1. Weigh 50 g of magnetic powder at normal temperature and pressure, pour the magnetic powder into a cold pressing concave die sprayed with lubricant, and cold press at a pressure of 300 MPa. After pressing, a columnar cold pressing blank with an outer diameter of 21.0 mm and a height of 27.9 mm is obtained. The lubricant is graphite.

[0083] 2. Under an argon atmosphere, the cold pressing blank sprayed with lubricant on the surface is transferred to a hot pressing concave die with a temperature of 700℃, at which time the upper punch of the press is heated to 600℃, hot pressing is performed at a pressure of 400 MPa, and after hot pressing, a columnar pre-pressed compact with an outer diameter of 22.1 mm and a height of 17.3 mm is obtained. The lubricant is graphite.

[0084] 3. The pre-pressed compact is preheated in a heater at 900℃ and held for 2 min, and then transferred to the lower punch within 5 s. The temperature of the hot deformation concave die is maintained at 800℃, and the temperature of the upper punch is maintained at 650℃. Floating pressing is performed, the moving speed of the upper punch is 0.90 mm / s, the floating speed of the hot deformation concave die is 2.23 mm / s (the inner diameter of the hot deformation concave die D = 25.00 mm, the outer diameter of the upper punch d = 20.80 mm, and the value of k is 1.1), and the pressing is completed within 30 s. A cup-shaped magnet with a size of 24.8(Φ outer) × 21(Φ inner) × 43 mm(H) is obtained. The lubricant is graphite.

[0085] 4. The bottom of the magnet is cut off to obtain a magnetic ring with a height of 38 mm.

[0086] ​5. Cut the magnetic ring to obtain a sample for measuring magnetic properties, and measure the magnetic properties.

[0087] Example 2

[0088] MQU-F magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%) was selected.

[0089] 1. Weigh 150 g of the magnetic powder at normal temperature and pressure, pour the magnetic powder into a lubricant-sprayed cold-pressing concave mold, and cold-press at a pressure of 300 MPa. After the pressing is completed, a columnar cold-pressed blank with an outer diameter of 36.0 mm and a height of 29.2 mm is taken out. The lubricant is molybdenum disulfide.

[0090] 2. Under an argon atmosphere, the cold-pressed blank sprayed with the lubricant is transferred to a hot-pressing concave mold with a temperature of 700℃, at which time the upper punch of the press is heated to 600℃, and hot-pressing is performed at a pressure of 400 MPa. After the hot-pressing, a columnar pre-pressed blank with an outer diameter of 37.5 mm and a height of 18.1 mm is taken out. The lubricant is molybdenum disulfide.

[0091] 3. The pre-pressed blank is preheated in a heater at 950℃ and kept for 4 min, and the pre-pressed blank is transferred to the lower punch within 5 s. The temperature of the hot-deformation concave mold is kept at 750℃, and the temperature of the upper punch is kept at 650℃. Floating pressing is performed, the moving rate of the upper punch is 0.30 mm / s, the floating rate of the hot-deformation concave mold is 0.88 mm / s (the inner diameter D of the hot-deformation concave mold is 42.70 mm, the outer diameter d of the upper punch is 36.40 mm, and the value of k is 1.1), and the pressing is completed within 30 s. A cup-shaped magnet with an outer diameter of 42.5(Φ), an inner diameter of 36.7(Φ), and a height of 33 mm (H) is prepared. The lubricant is molybdenum disulfide.

[0092] 4. The bottom of the magnet is cut off to obtain a magnetic ring with a height of 28 mm.

[0093] 5. Cut the magnetic ring to obtain a sample for measuring magnetic properties, and measure the magnetic properties.

[0094] Example 3

[0095] MQU-G magnetic powder (Nd 11.2 Pr 16.8 Dy 1.92 Fe bal .B 0.91 Co 4.0 Ga 0.49 , wt%) was selected.

[0096] 1. Weigh 50g of magnetic powder at normal temperature and pressure, pour the magnetic powder into a cold-pressing concave mold sprayed with lubricant, and cold-press at a pressure of 300 MPa. After the pressing is completed, a columnar cold-pressed blank with an outer diameter of 21.0 mm and a height of 29.9 mm is taken out. The lubricant is one of graphite, molybdenum disulfide, and BN.

[0097] 2. Under an argon atmosphere, the cold-pressed blank sprayed with lubricant on the surface is transferred to a hot-pressing concave mold with a temperature of 700℃, at which time the upper punch of the press is heated to 600℃, hot-pressing is performed at a pressure of 400 MPa, and after hot-pressing, a columnar pre-pressed blank with an outer diameter of 22.1 mm and a height of 17.5 mm is taken out. The lubricant is BN.

[0098] 3. The pre-pressed blank is preheated in a heater at 900℃ and kept for 2 min, and the pre-pressed blank is transferred to the lower punch within 5 s, the hot-deformation concave mold temperature is kept at 800℃, the upper punch is kept at 650℃, floating pressing is performed, the upper punch moving rate is 1.00 mm / s, the hot-deformation concave mold floating rate is 2.70 mm / s (hot-deformation concave mold inner diameter D = 25.00 mm, upper punch outer diameter d = 20.80 mm, k value is 1.2), and the pressing is completed within 30 s, to prepare a cup-shaped magnet with a size of 24.8 (Φ outer) x 21 (Φ inner) x 41 mm (H). The lubricant is BN.

[0099] 4. The bottom of the magnet is cut off to obtain a magnetic ring with a height of 35 mm.

[0100] 5. The magnetic ring is cut to obtain a magnetic performance measurement sample, and the magnetic performance is measured.

[0101] Comparative Example 1

[0102] Magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%) is selected.

[0103] 1. Weigh 50g of magnetic powder at normal temperature and pressure, pour the magnetic powder into a cold-pressing concave mold sprayed with lubricant, and cold-press at a pressure of 300 MPa. After the pressing is completed, a columnar cold-pressed blank with an outer diameter of 21.0 mm and a height of 29.9 mm is taken out. The lubricant is one of graphite, molybdenum disulfide, and BN.

[0104] 2. Under an argon atmosphere, the cold-pressed blank sprayed with lubricant on the surface is transferred to a hot-pressing concave mold with a temperature of 700℃, at which time the upper punch of the press is heated to 600℃, hot-pressing is performed at a pressure of 400 MPa, and after hot-pressing, a columnar pre-pressed blank with an outer diameter of 22.1 mm and a height of 17.5 mm is taken out. The lubricant is BN.

[0105] 3. The pre-pressed compact is transferred to the lower punch, the temperature of the hot deformation die is kept at 850°C, the temperature of the upper punch is kept at 650°C, and the floating pressing is carried out, the moving speed of the upper punch is 0.90 mm / s, the floating speed of the hot deformation die is 2.23 mm / s (the inner diameter of the hot deformation die D = 25.00 mm, the outer diameter of the upper punch d = 20.80 mm, k = 1.1), and the pressing is completed within 30 seconds, thereby obtaining a cup-shaped magnet with an outer diameter of 24.8 (Φ), an inner diameter of 21 (Φ), and a height of 41 mm (H). The lubricant is graphite.

[0106] 4. The bottom of the magnet is cut off, and a magnetic ring with a height of 35 mm is obtained.

[0107] 5. The magnetic ring is cut to obtain a sample for measuring the magnetic properties, and the magnetic properties are measured.

[0108] Comparative Example 2

[0109] MQU-F magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%) is selected.

[0110] 1. 50 g of the magnetic powder is weighed at normal temperature and pressure, and the magnetic powder is poured into a cold pressing die sprayed with a lubricant to carry out cold pressing, the pressure is 300 MPa, and after the pressing is completed, a columnar cold pressing compact with an outer diameter of 21.0 mm and a height of 27.9 mm is taken out. The lubricant is graphite.

[0111] 2. The cold pressing compact sprayed with the lubricant on the surface is transferred to a hot pressing die with a temperature of 700°C under an argon atmosphere, at this time the upper punch of the press is heated to 600°C, hot pressing is carried out, the pressure is 400 MPa, and after hot pressing, a columnar pre-pressed compact with an outer diameter of 22.1 mm and a height of 17.3 mm is taken out. The lubricant is graphite.

[0112] 3. The pre-pressed compact is transferred to the lower punch, the temperature of the hot deformation die is kept at 850°C, the temperature of the upper punch is kept at 650°C, and the floating pressing is carried out, the moving speed of the upper punch is 0.90 mm / s, the floating speed of the hot deformation die is 2.23 mm / s (the inner diameter of the hot deformation die D = 25.00 mm, the outer diameter of the upper punch d = 20.80 mm, k = 1.1), and the pressing is completed within 30 seconds, thereby obtaining a cup-shaped magnet with an outer diameter of 24.8 (Φ), an inner diameter of 21 (Φ), and a height of 41 mm (H). The lubricant is graphite.

[0113] 4. The bottom of the magnet is cut off, and a magnetic ring with a height of 32 mm is obtained.

[0114] 5. The magnetic ring is cut to obtain a sample for measuring the magnetic properties, and the magnetic properties are measured.

[0115] Comparative Example 3

[0116] MQU-F magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%).

[0117] 1. Weigh 50g of the magnetic powder at normal temperature and pressure, pour the magnetic powder into a cold-pressing concave mold sprayed with lubricant, and perform cold pressing at a pressure of 300 MPa. After the pressing is completed, a columnar cold-pressed blank with an outer diameter of 21.0 mm and a height of 27.9 mm is taken out. The lubricant is graphite.

[0118] 2. Under an argon atmosphere, the cold-pressed blank sprayed with lubricant on the surface is transferred to a hot-pressing concave mold with a temperature of 700℃, at which time the upper punch of the press is heated to 600℃, hot pressing is performed at a pressure of 400 MPa, and after hot pressing, a columnar pre-pressed blank with an outer diameter of 22.1 mm and a height of 17.3 mm is taken out. The lubricant is graphite.

[0119] 3. The pre-pressed blank is preheated in a heater at 900℃ and kept for 2 min, and the pre-pressed blank is transferred to the lower punch within 5 seconds, the hot-deformation concave mold temperature is kept at 800℃, the upper punch is kept at 650℃, floating pressing is performed, the upper punch moving rate is 0.90 mm / s, the hot-deformation concave mold floating rate is 1.01 mm / s (hot-deformation concave mold inner diameter D = 25.00 mm, upper punch outer diameter d = 20.80 mm, k value is 0.5), and the pressing is completed within 30 seconds, thereby preparing a cup-shaped magnet with a size of 24.8 (Φ outer) x 21 (Φ inner) x 40 mm (H). The lubricant is graphite.

[0120] 4. The bottom of the magnet is cut off to obtain a magnetic ring with a height of 33 mm.

[0121] 5. The magnetic ring is cut to obtain a magnetic performance measurement sample, and the magnetic performance is measured.

[0122] Comparative Example 4

[0123] MQU-F magnetic powder (Nd 30.2 Fe bal B 0.92 Co 4.1 Ga 0.44 , wt%).

[0124] 1. Weigh 50g of the magnetic powder at normal temperature and pressure, pour the magnetic powder into a cold-pressing concave mold sprayed with lubricant, and perform cold pressing at a pressure of 300 MPa. After the pressing is completed, a columnar cold-pressed blank with an outer diameter of 21.0 mm and a height of 27.9 mm is taken out. The lubricant is graphite.

[0125] 2. The cold-pressed compact was transferred into the hot-pressing female die at 700°C under an argon atmosphere, and the upper punch of the press was heated to 600°C. Hot-pressing was performed at a pressure of 400 MPa. The pre-compacts were removed as cylindrical bodies with an outer diameter of 22.1 mm and a height of 17.3 mm. The lubricant was graphite.

[0126] 3. The pre-compacts were preheated in a heater at 900°C for 2 min, and were transferred into the lower punch within 5 s. Hot deformation was performed by floating pressing at a temperature of 800°C for the hot-deformation female die and 650°C for the upper punch. The upper punch moved at a rate of 0.90 mm / s, and the hot-deformation female die floated at a rate of 2.84 mm / s (hot-deformation female die inner diameter D = 25.00 mm, upper punch outer diameter d = 20.80 mm, k = 1.4). The pressing was completed within 30 s, and a cup-shaped magnet with an outer diameter of 24.8 Φ, an inner diameter of 21 Φ, and a height of 44 mm was obtained. The lubricant was graphite.

[0127] 4. The bottom of the magnet was cut off to obtain a magnetic ring with a height of 36 mm.

[0128] 5. The magnetic ring was cut to obtain a sample for measuring magnetic properties, and the magnetic properties were measured.

[0129] Table 1 Magnetic properties of the magnetic ring

[0130]

[0131]

[0132] Table 2 Maximum pit size of the inner wall corrosion of the hot-deformation female die after the preparation of the multi-piece magnet

[0133]

[0134] Table 3 Upper punch pressing rate and hot-deformation female die floating rate in the examples

[0135]

[0136] As can be seen from the data in Tables 1 and 2, good magnetic properties were obtained for all of the examples and all of the comparative examples. The corrosion pits of the inner wall of the hot-deformation female die in Table 2 were formed by the corrosion of the rare earth-rich phase precipitated from the magnet. The maximum pit size of the inner wall corrosion of the hot-deformation female die was measured after the preparation of the multi-piece magnet. The maximum pit size of the inner wall corrosion of the hot-deformation female die was smaller for Examples 1-3 than for Comparative Examples 1 and 2, i.e., the temperature arrangement of the present application can greatly reduce the wear of the hot-deformation female die and improve the service life of the die.

[0137] Comparing Example 1 and Example 3, it is found that G magnetic powder and F magnetic powder are used for hot deformation, because the cold-pressed blank prepared by using G magnetic powder is higher under the same pressure, G magnetic powder is a little harder, so the pressing rate and the floating rate of the hot deformation die are different from F magnetic powder. In addition, because G magnetic powder contains heavy rare earth Dy, the magnetic properties of the hot deformation magnet prepared by G magnetic powder are higher than those of F magnetic powder.

[0138] Comparing Example 1 and Example 2, it is found that the same magnetic powder F is used to prepare the hot deformation magnetic ring, because the weight and volume of the magnet prepared in Example 2 are larger, the preheating temperature and holding time are longer, so that the pre-pressed blank can be smoothly transferred to the hot deformation die for hot deformation. Because the preheating temperature is higher, the magnetic properties of the magnet in Example 2 are lower than those of the magnet in Example 1. In addition, the pressing rate V1 of the upper punch and the floating rate V2 of the hot deformation die in Example 2 are smaller, so as to facilitate the smooth hot deformation of the magnet.

[0139] By comparing Comparative Example 2 (k=0), Comparative Example 3 (k=0.5), Example 1 (k=1.1) and Comparative Example 4 (k=1.4), it is found that the value of k has little effect on the magnetic properties, but has a great influence on the maximum pit size of the inner wall of the hot deformation die. When k=0 (no floating of the hot deformation die), after pressing about 1000 hot deformation magnets, the hot deformation die is greatly worn, and the lower punch and the hot deformation die are stuck under the resistance of the magnet, so that the pressing cannot continue. When there is preheating and floating pressing, the lower punch and the hot deformation die can continue to work when pressing to 4000, which indicates that the situation of the rare earth-rich substance is improved.

[0140] The above describes the embodiments of the present application in detail. The principles and implementation manners of the present application are described by applying specific examples, and the above description of the embodiments is only used to help understand the technical solutions and core ideas of the present application. Therefore, the changes or deformations made by the person skilled in the art according to the ideas of the present application, based on the specific implementation manners and application scope of the present application, all belong to the scope of protection of the present application. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method of making a hot deformed magnet, comprising: The application relates to a method for manufacturing a magnetic body, which comprises the following steps: The magnetic powder is cold-pressed to obtain a cold-pressed blank, wherein the density of the cold-pressed blank is 4.5-5.5 g / cm 3 , hot-pressing the cold-pressed blank in a hot-pressing concave die at 600-800 DEG C to obtain a pre-pressed blank; preheating the pre-pressed blank, wherein the temperature of the pre-pressed blank after preheating is 850-950 DEG C; transferring the preheated pre-pressed blank into a hot-deformation concave die, wherein the temperature of the hot-deformation concave die is 750-800 DEG C; the temperature of the pre-pressed blank is decreased by no more than 15 DEG C during the transferring process; maintaining the temperature of the upper punch at 600-700 DEG C, and making the upper punch enter the hot-deformation concave die to perform hot deformation on the preheated pre-pressed blank to obtain a magnetic body; wherein the hot-deformation step is performed by floating pressing, the moving speed V1 of the upper punch is 0.2-1.0 mm / s, and the moving speed of the hot-deformation concave die is: wherein K is 0.8-1.2, D is the inner diameter of the hot-deformation concave die, and d is the outer diameter of the upper punch.

2. The method of claim 1, wherein the hot deforming is performed at a temperature of 800- 1000°C. The preheating of the pre-pressed blank comprises heating the pre-pressed blank at 850-950 DEG C for 1-10 min.

3. The method of claim 1, wherein the hot deforming is performed at a temperature of 800- 1000°C. The preheated pre-pressed blank is transferred into the hot-deformation concave die within 5 seconds.

Images