LARGE SINTERED R-FE-B MAGNET, PREPARATION METHOD AND USE THEREOF

Abstract

A large sintered RFeB magnet, a preparation method and use thereof are provided. The sintered RFeB magnet has a thickness not less than 10 mm in an orientation direction. Any cross section along the orientation direction is marked as a diffusion cross-section area, and a side of the diffusion cross-section area close to the outer surface of the sintered RFeB magnet is marked as the surface of the diffusion cross-section area. The difference between the coercivity of the surface of the diffusion cross-section area and the coercivity at 5 mm away from the surface of the diffusion cross-section area is H, and H is 50 kA/m.

Claims

1. A sintered RFeB magnet, wherein the sintered RFeB magnet has a thickness not less than 10 mm in an orientation direction, any cross section along the orientation direction is marked as a diffusion cross-section area and one side of the diffusion cross-section area close to the outer surface of the sintered RFeB magnet is marked as the surface of the diffusion cross-section area, and the difference between the coercivity of the surface of the diffusion cross-section area and the coercivity at 5 mm away from the surface of the diffusion cross-section area is H, wherein H is 50 kA/m.

2. The sintered RFeB magnet according to claim 1, wherein H is not greater than 45 kA/m; preferably, the thickness in the orientation direction is 10 mm to 20 mm; preferably, the raw materials of the sintered RFeB magnet comprise R, B, Fe, and M, wherein: R has a content by weight of 27 wt %-34 wt %, preferably 29 wt %-32 wt %; M has a content by weight of 0 wt %-5 wt %, preferably 0 wt %-3 wt %; preferably, R is selected from at least one of rare earth elements Nd, Pr, Tb, Dy, Gd, and Ho; preferably, M is selected from at least one of Ti, V, Cr, Mn, Co, Ga, Cu, Si, Al, Zr, Nb, W, and Mo.

3. A preparation method of the sintered RFeB magnet according to claim 1, comprising the following steps: (1) manufacturing a blank of the RFeB magnet having a thickness 10 mm; (2) diffusion part disposing: disposing diffusion parts on at least 2 surfaces in the orientation direction of the blank obtained in step (1), wherein each of the diffusion parts comprises at least 1 RH layer and 1 M layer, the M layer is in direct contact with the surface of the blank, at least 1 M layer is disposed between the RH layer and the blank; and (3) thermal diffusion treatment: conducting a thermal diffusion treatment on the blank with thick diffusion layers disposed in step (2) to give the sintered RFeB magnet.

4. The preparation method according to claim 3, wherein in step (2), the RH layer and the M layer are alternately disposed in the diffusion parts, wherein at least 1 M layer is disposed between the RH layer and the blank, the RH layer comprises 1-3 layers and the M layer comprises 1-3 layers; illustratively, the diffusion part comprises 1 M layer and 1 RH layer; illustratively, the diffusion part comprises 2 M layers and 2 RH layers disposed in an order from the surface of the blank of a first M layer, a first RH layer, a second M layer, and a second RH layer; preferably, the first M layer and the second M layer may be identical or different; preferably, the first RH layer and the second RH layer may be identical or different; preferably, in the diffusion part, each RH layer has a thickness of 1 m to 70 m.

5. The preparation method according to claim 3, wherein the method for manufacturing the RH layer comprises: applying an RH slurry on 2 surfaces of the blank in the orientation direction, and drying to give the RH layer; preferably, the RH slurry comprises a heavy rare earth element, an organic solid, and a solvent; preferably, the mass ratio of the heavy rare earth element to the organic solid to the solvent in the RH slurry is (40-70):(0.5-12):(0-50); preferably, the heavy rare earth element includes at least one of metal dysprosium, metal terbium, dysprosium hydride, terbium hydride, dysprosium fluoride, terbium fluoride, dysprosium oxide, and terbium oxide; preferably, the organic solid is at least one selected from rosin-modified alkyd resin, thermoplastic phenolic resin, urea-formaldehyde resin, and polyvinyl butyral; preferably, the solvent is selected from at least one of an alcohol solvent, an ether solvent, and an aromatic hydrocarbon solvent; preferably, in the diffusion part, each M layer has a thickness less than 20 m and greater than 0.1 m, preferably less than or equal to 10 m; preferably, in the diffusion part, the thickness ratio of each RH layer to each M layer is (1-70):(0.1-20).

6. The preparation method according to claim 3, wherein the method for manufacturing the M layer comprises: applying a slurry containing an M powder on 2 surfaces of the blank in the orientation direction, and drying to give the M layer; preferably, the slurry containing the M powder comprises the M powder, an organic solid, and a solvent; preferably, the mass ratio of the M powder to the organic solid to the solvent in the slurry containing the M powder is (20-70):(1-10):(0-50); preferably, the M powder includes at least one of graphite powder, titanium powder, zirconium powder, molybdenum powder, tungsten powder, titanium oxide, zirconium oxide, molybdenum oxide, and tungsten oxide, and M powder has an oxygen atom content less than 3%, preferably less than 1%; preferably, the M powder comprises a powder having a particle size less than 5 m, wherein a powder having a particle size of between 0.5 m and 1.8 m is more than 50%, preferably more than 65%, of the total mass of the powder.

7. The preparation method according to claim 3, wherein in step (3), the thermal diffusion treatment comprises at least a DW thermal treatment and an ST thermal treatment; preferably, the DW thermal treatment comprises: after the temperature is raised to a DW temperature, holding the temperature for a period of time; preferably, the DW temperature is 280 C. to 480 C., more preferably 320 C. to 400 C.; preferably, the time of the DW thermal treatment is greater than or equal to 2 h; preferably, the DW thermal treatment is conducted in vacuum.

8. The preparation method according to claim 7, wherein in step (3), the ST thermal treatment comprises a low-temperature thermal treatment and a high-temperature thermal treatment, wherein the temperature of the low-temperature thermal treatment is 750 C. to 890 C., and the temperature of the high-temperature thermal treatment is 830 C. to 970 C., wherein the difference between temperatures of the low-temperature thermal treatment and the high-temperature thermal treatment is greater than 30 C., and the time of the low-temperature thermal treatment and/or the high-temperature thermal treatment is not greater than 50 h, wherein the holding time is 2 h; preferably, the ramping rate from the low-temperature thermal treatment to the high-temperature thermal treatment is 4-10 C./min; preferably, the low-temperature thermal treatment comprises: after the temperature is raised to the temperature of the low-temperature thermal treatment, holding the temperature for a period of time; preferably, the high-temperature thermal treatment comprises: after the temperature is raised to the temperature of the high-temperature thermal treatment, holding the temperature for a period of time; preferably, in step (3), the ST thermal treatment comprises alternate low-temperature thermal treatments and high-temperature thermal treatments; preferably, the time of the ST thermal treatment is not less than 2 h; preferably, the ST thermal treatment is conducted in vacuum or in an inert gas atmosphere.

9. The preparation method according to claim 3, wherein the blank is sequentially washed with an acid solution and deionized water, and dried before the diffusion part is disposed; preferably, the method further comprises: (4) after quenching, conducting an aging treatment in the following condition: an aging temperature of 430-650 C., and an aging time of greater than 30 min, and quenching to room temperature after the aging treatment is completed; preferably, the aging treatment is conducted in vacuum or in an inert gas atmosphere.

10. Use of the sintered RFeB magnet according to claim 1 in the fields of wind power generation, household motors, automobiles, medical equipment, or mobile communication devices, preferably in the field of wind power generation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 is a schematic view of the state of a diffusion part undergone a DW thermal process; and

[0059] FIG. 2 is a schematic view of the sampling position on a sintered RFeB magnet sample according to Example 1 (unit: mm).

DETAILED DESCRIPTION

[0060] The embodiments of the present disclosure will be further illustrated in detail with reference to the following specific examples. It will be appreciated that the following examples are merely exemplary illustrations and explanations of the present disclosure, and should not be construed as limiting the protection scope of the present disclosure. All techniques implemented based on the content of the present disclosure described above are included within the protection scope of the present disclosure. Unless otherwise stated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared using known methods.

Example 1

[0061] The procedures for manufacturing the large sintered magnet are as follows: [0062] (1) A neodymium-iron-boron magnet (RFeB magnet) was prepared from raw materials according to the formula: 29.1% of Nd, 1.2% of Dy, 1.5% of Co, 0.2% of Al, 0.1% of Ga, 0.2% of Ti, 0.17% of Cu, 0.98% of B, and the remaining of Fe. Raw materials were smelted in a furnace through strip casting process to manufacture neodymium-iron-boron alloy flakes with a thickness in a range of 0.1-0.5 mm. The alloy flakes were subjected to coarse crushing with hydrogen embrittlement process to give a powder. The powder was ground with a jet mill to give a fine powder with an SMD of 2.85 m. The fine powder was oriented in a magnetic field, compressed, and molded to give a compact blank with a density of 3.98 g/cm.sup.3. The compact blank was then subjected to sintering in a sintering furnace and aging treatment to give a raw blank. The raw blank was processed to give a blank. The surface of the blank was washed with a nitric acid solution and deionized water, and dried to obtain a neodymium-iron-boron magnet blank A1 with dimensions of 80 mm40 mm11 mm, a dimensional tolerance of 0.03 mm, and a thickness of Z=11 mm in the orientation direction of A1. [0063] (2) Diffusion part was disposed. Diffusion parts were disposed on 2 surfaces in the orientation direction of the blank A1. Each of the diffusion parts was in a two-layer structure and comprised an M layer and an RH layer. The M layer was in direct contact with the surface of the blank A1, and the RH layer was disposed on the surface of the M layer. The specific procedures are as follows: [0064] (a) The manufacturing procedures of the M layer are as follows: Graphite powder (the content of oxygen in powder was 0.07%), an organic solid rosin-modified alkyd resin, and ethanol were prepared into a first slurry according to weight percentages of 55 wt %, 2 wt %, and 43 wt %, respectively. The first slurry was applied to the surface of the blank A1 by spraying, and dried by hot air blast at 60 C. to give the M layer with a thickness of 32 m. [0065] (b) An RH layer was disposed on the surface of the dried M layer by the following procedures: Terbium hydride powder, an organic solid rosin-modified alkyd resin, and ethanol were prepared into a second slurry according to weight percentages of 62 wt %, 3 wt %, and 35 wt %, respectively. The second slurry was applied to the surface of the M layer described above by spraying, and dried by hot air blast at 60 C. to give the RH layer with a thickness of 5015 m. A blank A2 was obtained after the diffusion parts were disposed on the surface of the blank A1. [0066] (3) Thermal diffusion treatment: The blank A2 was placed in a graphite container for thermal diffusion treatment. The thermal diffusion treatment process was conducted in vacuum, and heating was started when the vacuum degree was 10 Pa. The thermal diffusion treatment process mainly comprised heating, DW, ST, and cooling, as described below: [0067] 1) Heating: the temperature was raised to 400 C. in 80 min; [0068] 2) DW: the temperature was held at 400 C. for 240 min; [0069] 3) Heating: the temperature was raised from 400 C. to 850 C. in 70 min; [0070] 4) ST1: the temperature was held at 850 C. for 480 min; [0071] 5) Heating: the temperature was raised from 850 C. to 940 C. in 30 min; [0072] 6) ST2: the temperature was held at 940 C. for 1080 min; [0073] (4) Aging treatment: After the thermal diffusion treatment was finished, argon was filled, and the system was quenched with a fan to a temperature below 80 C. After quenching, the system was heated to 500 C. for aging treatment at a ramping rate of 5 C./min. The temperature was held for 120 min (the aging treatment refers to a thermal treatment process in which alloy workpieces, after solution treatment, cold plastic formation or casting and forging, are placed at a high temperature or kept at room temperature to maintain the variation in performance, shape and size over time). After the aging treatment, argon was filled again, and the system was quenched with a fan to a temperature below 80 C. to give a finished sintered neodymium-iron-boron magnet A3.

[0074] FIG. 1 is a schematic view of the diffusion part undergone a DW thermal process. After the DW process, the organic solid and the solvent were removed from the diffusion parts in the M layer. As such, the M layer in the diffusion part mainly comprised graphite powder, and the RH layer mainly comprised terbium hydride powder. [0075] (5) The above sintered neodymium-iron-boron magnet A3 was tested as follows: [0076] 1) Sampling: As shown in FIG. 2, a diffusion cross-section area was obtained by sectioning the sintered neodymium-iron-boron magnet A3 in the orientation direction of the A3, and samples with the dimensions of 1 mm1 mm1 mm were taken at the surface and a position 5 mm away from the surface of the sintered magnet in the diffusion cross-sectional area, which were respectively designated as H1-1 and H1-2.

[0077] The performances of the samples H1-1 and H1-2 of Example 1 were tested and compared. The results are shown in Table 1. [0078] 2) The test condition is as follows: [0079] Sample size: 1 mm1 mm1 mm, tolerance: 0.03 mm; [0080] Temperature: 23 C.; [0081] Instrument: HIRST PFM06 (upper detection limit of coercivity: 60 kOe, temperature range: 16-40 C., minimum sample size: B111).

TABLE-US-00001 TABLE 1 Performance of samples H1-1 and H1-2 in Example 1 Item Hcj (kA/m) H (kA/m) H1-1 2154 42 H1-2 2112

Example 2

[0082] The procedures for manufacturing the large sintered magnet are as follows: [0083] (1) A neodymium-iron-boron magnet (RFeB magnet) was prepared from raw materials according to the formula: 28.6% of PrNd, 1.5% of Dy, 1.0% of Co, 0.1% of Al, 0.2% of Ga, 0.12% of Ti, 0.10% of Cu, 0.98% of B, and the remaining of Fe. Raw materials were smelted in a furnace through strip casting process to manufacture neodymium-iron-boron alloy flakes with a thickness in a range of 0.1-0.5 mm. The alloy flakes were subjected to coarse crushing with hydrogen embrittlement process to give a powder. The powder was ground with a jet mill to give a fine powder with an SMD of 2.85 m. The fine powder was oriented in a magnetic field, compressed, and molded to give a compact blank with a density of 3.95 g/cm.sup.3. The compact blank was then subjected to sintering in a sintering furnace and aging treatment to give a raw blank. The raw blank was processed to give a blank. The surface of the blank was washed with a nitric acid solution and deionized water, and dried to obtain a neodymium-iron-boron blank B1 with dimensions of 100 mm50 mm15 mm, a dimensional tolerance of 0.03 mm, and a thickness of Z=15 mm in the orientation direction of B1. [0084] (2) Diffusion part disposing: Diffusion part was disposed on a surface of the neodymium-iron-boron blank B1. The diffusion part was in a four-layer structure and comprised, sequentially from the surface of the neodymium-iron-boron blank B1, an M1 layer, an RH1 layer, an M2 layer, and an RH2 layer. The M1 layer was in direct contact with the blank B1. The specific procedures are as follows: [0085] (a) The manufacturing procedures of the M1 layer are as follows: Molybdenum powder (the content of oxygen in powder was 0.65%), an organic solid polyvinyl butyral, and ethanol were prepared into a first slurry according to weight percentages of 60 wt %, 5 wt %, and 35 wt %, respectively. The first slurry was applied to the surface of the blank B1 by spraying, and dried by hot air blast at 60 C. to give the M1 layer with a thickness of 32 m. [0086] (b) An RH1 layer was disposed on the surface of the dried M1 layer by the following procedures: Dysprosium hydride powder, an organic solid polyvinyl butyral, and ethanol were prepared into a second slurry according to weight percentages of 60 wt %, 8 wt %, and 32 wt %, respectively. The second slurry was applied to the surface of the M1 layer by spraying, and dried by hot air blast at 60 C. to give the RH1 layer with a thickness of 4015 m. [0087] (c) After drying, steps (a) and (b) were repeated to sequentially dispose an M2 layer and an RH2 layer with the first slurry and the second slurry in steps (a) and (b), respectively. The disposing of the diffusion parts on surfaces of the blank B1 was completed after drying to obtain a blank B2, with the thickness of the M2 layer being 21 m and the thickness of the RH2 layer being 3515 m. [0088] (3) Thermal diffusion treatment: The blank B2 was placed in a graphite container for thermal diffusion treatment. The thermal diffusion treatment process was conducted in vacuum. Heating was started when the vacuum degree is 10 Pa. The thermal diffusion treatment process mainly comprised heating, DW, ST, and cooling, as described below: [0089] 1) Heating: the temperature was raised from 50 C. to 420 C. in 80 min; [0090] 2) DW: the temperature was held at 420 C. for 240 min; [0091] 3) Heating: the temperature was raised from 420 C. to 750 C. in 70 min; [0092] 4) ST1: the temperature was held at 750 C. for 300 min; [0093] 5) Heating: the temperature was raised from 750 C. to 810 C. in 30 min; [0094] 6) ST2: the temperature was held at 810 C. for 420 min; [0095] 7) Heating: the temperature was raised from 780 C. to 870 C. in 40 min; [0096] 8) ST3: the temperature was held at 870 C. for 1200 min; [0097] (4) Aging treatment: After the thermal diffusion treatment was finished, argon was filled, and the system was quenched with a fan to a temperature below 80 C. After quenching, the system was heated to 520 C. for aging treatment at a ramping rate of 5 C./min. The temperature was held for 300 min (the aging treatment refers to a thermal treatment process in which alloy workpieces, after solution treatment, cold plastic formation or casting and forging, are placed at a high temperature or kept at room temperature to maintain the variation in performance, shape and size over time). After the aging treatment, argon was filled again, and the system was quenched with a fan to a temperature below 80 C. to give a finished sintered neodymium-iron-boron magnet B3. [0098] (5) The sintered neodymium-iron-boron magnet B3 of this example was tested with reference to Example 1, except that the A3 was replaced with the B3, and the samples were designated as H2-1 and H2-2. The test results are shown in Table 2.

TABLE-US-00002 TABLE 2 Performance of samples H2-1 and H2-2 in Example 2 Item Hcj (kA/m) H(kA/m) H2-1 1920 38 H2-2 1881

Comparative Example 1

[0099] This comparative example produced a blank using the same process for manufacturing the samples as in Example 1, except that: [0100] (2) Diffusion part disposing: Diffusion parts were disposed on 2 surfaces in the orientation direction of the blank A1, and an RH layer was directly disposed on the diffusion parts by the following procedures: Terbium hydride powder, an organic solid rosin-modified alkyd resin, and ethanol were prepared into a slurry according to weight percentages of 62 wt %, 3 wt %, and 35 wt %, respectively. The slurry was directly applied to the surface of the blank A1 by spraying, and dried by hot air blast at 60 C. to give the RH layer with a thickness of 5015 m.

[0101] The other steps (1), (3), and (4) were the same as Example 1, and a sintered neodymium-iron-boron magnet C3 was finally obtained in this comparative example. [0102] (5) The sintered neodymium-iron-boron magnet C3 was tested with reference to Example 1, except that the A3 was replaced with the C3, and samples D3-1 and D3-2 of Comparative Example 1 were obtained.

TABLE-US-00003 TABLE 3 Performance of samples H3-1 and H3-2 in Comparative Example 1 Item Hcj (kA/m) H (kA/m) D3-1 2159 83 D3-2 2076

Comparative Example 2

[0103] This comparative example produced a blank using the same process for manufacturing the samples as in Example 2, except that: [0104] (2) Diffusion part disposing: The content of oxygen in the molybdenum powder used for the M layer was 5.5%, while the content of oxygen in the molybdenum powder used in Example 2 was 0.65%. The other steps (1), (3), and (4) were the same as Example 2, and a sintered neodymium-iron-boron magnet D4 was finally obtained in this comparative example. Samples D4-1 and D4-2 were manufactured for Comparative Example 2. It can be seen that the overall performance of the samples was reduced and the uniformity of coercivity was deteriorated.

TABLE-US-00004 TABLE 4 Performance of samples D4-1 and D4-2 in Comparative Example 2 Item Hcj (kA/m) H (kA/m) D4-1 1902 65 D4-2 1837

Comparative Example 3

[0105] This comparative example was substantially the same as Example 2, except that the thermal diffusion treatment in step (3) is specifically as follows: [0106] 1) Heating: the temperature was raised from 50 C. to 420 C. in 80 min; [0107] 2) DW: the temperature was held at 420 C. for 240 min; [0108] 3) Heating: the temperature was raised from 420 C. to 870 C. in 140 min; [0109] 4) ST: the temperature was held at 870 C. for 900 min.

[0110] The other steps (1), (2), and (4) were the same as Example 1, and a sintered neodymium-iron-boron magnet E5 was finally obtained in this comparative example. [0111] (5) The sintered neodymium-iron-boron magnet E5 of this example was tested with reference to Example 1, except that the A3 was replaced with the E5, and the samples were designated as E5-1 and E5-2. The test results are shown in Table 5.

TABLE-US-00005 TABLE 5 Performance of samples E5-1 and E5-2 in Comparative Example 3 Item Hcj (kA/m) H (kA/m) E5-1 1913 67 E5-2 1846

[0112] The exemplary embodiments of the present disclosure have been described above. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent, improvement, and the like made by those skilled in the art without departing from the spirit and principle of the present disclosure shall fall within the protection scope of the present disclosure.