Hot-rolled rare earth permanent magnet and preparation method thereof

Abstract

The invention relates to a hot-rolled rare earth permanent magnet and a preparation method thereof, belongs to the technical field of vacuum hot rolling of rare earth permanent magnet materials, and provides a method for carrying out vacuum hot rolling on a hot-pressed full-density RE-Ga-M-Fe-B permanent magnet under the uncoated condition to enable crystal grains to be subjected to flow deformation and finally enabling the magnet to be oriented parallel to the rolling direction. The problem that large-scale production of the Nd-Fe-B permanent magnet prepared through an existing heat rheological method cannot be achieved is solved. The invention relates to a hot-rolled rare earth permanent magnet, the general formula of components of the permanent magnet is REaGabMcFedBe, and RE is one or more than two of Nd, Pr, Ce, La or Dy; m is one or more than two of Co, Cu, Al, Zr, Ti and Nb; in percentage by mass, a is greater than or equal to 28.0 and less than or equal to 32.0; 0.2 < = b < = 0.8; 3.0 < = c < = 6.0; 0.8 < = e < = 1.1; and d is equal to 100 to a-b to c-e. High-performance plate-shaped, tile-shaped and tubular rolled permanent magnets with high density, high orientation degree, good corrosion resistance and good temperature stability are realized.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum hot rolling of rare earth permanent magnet materials, in particular to a hot-rolled rare earth permanent magnet and a preparation method thereof. Background Art

[0002] As a functional material, rare earth iron-based permanent magnets are widely used in high-tech and emerging industries such as wind power generation, propulsion motors, and artificial intelligence micro motors, and have become an indispensable material basis for social progress. At present, the commercial production of Nd-Fe-B permanent magnets mainly includes three preparation methods: powder metallurgy sintering, powder bonding, and rapid quenching powder hot extrusion rheology.

[0003] Sintering technology is the main method for producing Nd-Fe-B permanent magnets, with an annual production volume of about 200,000 tons nationwide. However, sintering technology will produce 20% to 50% of processing waste; rapid quenching powder bonding technology is second, with an annual production volume of about 12,000 tons. Bonded magnets will be mixed with adhesives and have low magnetic properties; and rapid quenching powder hot extrusion rheology technology, due to the limitations of the molding process conditions, can only produce annular magnets at present, with an annual production volume of about 1,000 tons. With the development of market demand, the demand for hot extruded magnets is also increasing, and the molding process in hot extrusion has greatly restricted the industrial production of this technology.

[0004] The hot rolling process is very mature in the large metallurgical industry. It can significantly reduce energy consumption and costs, and can improve the processing performance of metals and alloys, that is, to break the coarse grains in the casting state, significantly heal cracks, reduce or eliminate casting defects, transform the cast structure into a deformed structure, and improve the processing performance of the alloy. Therefore, the hot rolling process is used for the thermal flow forming of magnetic powder. However, based on the particularity of the NdFeB material that is extremely easy to oxidize, the prior art adopts the method of coating the alloy powder for hot rolling. This method coats the alloy powder or cold-pressed powder blank with metal and evacuates it, then heat-seals it, and then heats the vacuum-sealed magnet and rolls it in the atmosphere. The method obtains the highest magnetic property of 30.1MGOe. Because the vacuum coating process of this method is complicated and can only be prepared in the laboratory, it is difficult to form large-scale industrial production, and the blank is difficult to control the heating in the sheath, resulting in low magnet performance after hot rolling. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a hot-rolled rare earth permanent magnet and a preparation method to solve at least one of the problems that the existing thermorheological method for preparing rare earth iron-based permanent magnets cannot be mass-produced, the magnet performance is low, the processing process is complicated, and the like.

[0006] On the one hand, an embodiment of the present invention provides a hot-rolled rare earth permanent magnet, wherein the composition formula of the permanent magnet is RE a Ga b Mc Fe d B e , wherein RE is one or more of Nd, Pr, Ce, La or Dy; M is one or more of Co, Cu, Al, Zr, Ti, Nb; the mass fraction is expressed in percentage as follows: 28.0≤a≤32.0; 0.2≤b≤0.8; 3.0≤c≤6.0; 0.8≤e≤1.1; d=100-abce.

[0007] On the other hand, an embodiment of the present invention further provides a method for preparing a hot-rolled rare earth permanent magnet, which is prepared according to the permanent magnet composition general formula, comprising the following steps:

[0008] Step 1, preparation of RE-Ga-M-Fe-B rapid quenching magnetic powder;

[0009] Step 2, cold molding: the quick-quenching magnetic powder prepared in step 1 is evenly loaded into a cold press mold for cold molding at a pressure greater than 100 MPa to obtain a blank with a density of more than 60%;

[0010] Step 3, hot isostatic pressing: under vacuum or argon protection, the rough part of step 2 is subjected to hot isostatic pressing to obtain an isotropic full-density rough part with a density of 100%;

[0011] Step 4, uncoated vacuum hot rolling: the full-density blank of step 3 is continuously vacuum hot rolled without coating, and the hot rolling temperature is 800-900° C. to obtain a hot-rolled permanent magnet product.

[0012] Preferably, the method for preparing the RE-Ga-M-Fe-B rapid quenching magnetic powder in step 1 comprises the following steps:

[0013] S1-1. According to the designed composition ratio, the alloy raw materials are subjected to vacuum induction melting at a melting temperature of 1400° C. to 1500° C. to obtain an alloy ingot;

[0014] S1-2, the alloy ingot obtained in S1 is rapidly quenched to obtain a rapidly quenched thin strip, the roller surface linear speed of the rapidly quenching roller is 25-50 m / s, and the average grain size of the rapidly quenched thin strip is 30-300 nm;

[0015] S1-3, mechanically crushing the quick-quenching thin strip obtained in S2 into quick-quenching magnetic powder with an average particle size of 100-200 mesh.

[0016] Specifically, the full-density blank in step 3 is in the shape of a plate, a tile or a tube.

[0017] Furthermore, the hot isostatic pressing process parameters in step 3 are: temperature 700-750° C., pressure 60-70 MPa.

[0018] Furthermore, the uncoated vacuum hot rolling in step 4 comprises the following steps:

[0019] S4-1, heating: the full density blank obtained in step 3 is placed in a continuous hot rolling equipment, and vacuumized to 10 -3 Pa and filled with argon, then quickly heated to 800 °C;

[0020] S4-2, hot rolling: the heated full-density blank enters the vacuum rolling mill chamber and is hot rolled at 800-850°C to obtain a rolled permanent magnet;

[0021] S4-3, leveling and bending: after rolling, the permanent magnet enters the leveling roller and the bending roller for leveling and bending;

[0022] S4-4, cooling: after flattening and flat bending, the magnet enters a cooling chamber and is cooled to room temperature at a rate of 5-10°C / min to obtain anisotropic hot-rolled permanent magnet products with the required shape and size and orientation parallel to the rolling direction.

[0023] It should be noted that the heating method in step S4-1 adopts vacuum induction heating.

[0024] Preferably, during the hot rolling process in step S4-2, the rolling roller pressure is 2 to 5 tons and the roller speed is 2 to 5 m / min.

[0025] Specifically, during the hot rolling process in step S4-2, the reduction ratio of the full-density blank is between 60% and 75%.

[0026] Exemplarily, the process conditions of the leveling and bending process in step S4-3 are: roller speed 2 to 10 m / min, roller spacing size is the same as the hot rolling roller spacing size, and temperature is 800 to 850°C.

[0027] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0028] 1. The present invention optimizes the design of rare earth permanent magnet components to improve the high-temperature thermal deformation capacity of the permanent magnet, and can perform continuous hot rolling operations to ensure the performance and quality of the permanent magnet during the continuous hot rolling process.

[0029] 2. The method provided by the present invention for preparing permanent magnets by vacuum hot rolling RE-Ga-M-Fe-B full-density blanks without coating has a simple process, and the blank temperature is easy to control and heated evenly, which solves the problem that grain rheology permanent magnets cannot be produced on an industrial scale, and obtains plate-shaped, tile-shaped, and tubular high-performance permanent magnets with high density, high orientation, good corrosion resistance, and good temperature stability.

[0030] 3. The present invention is under vacuum and inert gas protection, without using a coating process, and can continuously and quickly carry out the hot rolling process including four process processes of heating, rolling, leveling and bending, and cooling to achieve large-scale industrial production. Compared with the traditional sintering process, it has the characteristics of short process, fast magnet preparation speed, near-final forming, and low cost; due to the near-final forming size and shape of this vacuum hot rolling technology and reasonable cost performance, it is also highly competitive compared with traditional bonded magnet production. The maximum magnetic energy product of the vacuum hot-rolled RE-Ga-M-Fe-B rheological permanent magnet prepared by this method is ≥38MGOe.

[0031] 4. The present invention optimizes and precisely controls parameters such as vacuum hot rolling temperature, speed, and roller pressure, so as to control the shrinkage ratio of the full-density blank reduction to be between 60% and 75%, and the entire hot rolling process is carried out continuously and rapidly, ultimately obtaining a high-performance hot-rolled permanent magnet with grain rheological orientation.

[0032] 5. The present invention continuously performs cold molding and hot isostatic pressing and accurately controls the temperature and pressure of the hot isostatic pressing process to press the magnetic powder into an isotropic blank with qualified composition and high density (>99%) to meet the billet density requirement required by the subsequent hot rolling process.

[0033] 6. The present invention adopts induction heating in the hot rolling process to quickly heat the blank to the required temperature, effectively avoiding the long heat diffusion time that causes the magnet grains to grow and affects the magnetic properties.

[0034] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be obvious from the description or understood by practicing the present invention. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described in detail below, and together with the embodiments of the present invention, they are used to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0036] On the one hand, a specific embodiment of the present invention discloses a hot-rolled rare earth permanent magnet, wherein the composition formula of the permanent magnet is RE a Ga b M c Fe d B e , wherein RE is one or more of Nd, Pr, Ce, La or Dy; M is one or more of Co, Cu, Al, Zr, Ti, Nb; the mass fraction is expressed in percentage as follows: 28.0≤a≤32.0; 0.2≤b≤0.8; 3.0≤c≤6.0; 0.8≤e≤1.1; d=100-abce.

[0037] The composition of rare earth permanent magnets is optimized and designed, and the comprehensive characteristics of rare earth elements and ferromagnetic elements are fully utilized to improve the high-temperature thermal deformation ability of permanent magnets, so that continuous hot rolling operations can be carried out to ensure the performance and quality of permanent magnets during continuous hot rolling. In particular, precise control of Ga content can significantly improve the rolling characteristics of the alloy.

[0038] On the other hand, a specific embodiment of the present invention also discloses a method for preparing a hot-rolled rare earth permanent magnet, which is prepared according to the permanent magnet composition general formula, comprising the following steps:

[0039] Step 1, preparation of RE-Ga-M-Fe-B rapid quenching magnetic powder;

[0040] Step 2, cold molding: the quick-quenching magnetic powder prepared in step 1 is evenly loaded into a cold press mold for cold molding at a pressure greater than 100 MPa to obtain a blank with a density of more than 60%;

[0041] Step 3, hot isostatic pressing: under vacuum or argon protection, the rough part of step 2 is subjected to hot isostatic pressing to obtain an isotropic full-density rough part;

[0042] Step 4, uncoated vacuum hot rolling: the full-density blank of step 3 is continuously vacuum hot rolled without coating, and the hot rolling temperature is 800-900° C. to obtain a hot-rolled permanent magnet product.

[0043] Specifically, in step 1, the method for preparing the RE-Ga-M-Fe-B rapid quenching magnetic powder comprises the following steps:

[0044] S1-1. According to the designed composition ratio, the alloy raw materials are subjected to vacuum induction melting at a melting temperature of 1400° C. to 1500° C. to obtain an alloy ingot;

[0045] S1-2, the alloy ingot obtained in S1 is rapidly quenched to obtain a rapidly quenched thin strip, the roller surface linear speed of the rapidly quenching roller is 25-50 m / s, and the average grain size of the rapidly quenched thin strip is 30-300 nm;

[0046] S1-3, mechanically crushing the quick-quenching thin strip obtained in S2 into quick-quenching magnetic powder with an average particle size of 100-200 mesh.

[0047] Exemplarily, the full-density blank in step 3 is in the shape of a plate, a tile or a tube. The permanent magnet preparation method of the present invention can be used to prepare tile-shaped and tube-shaped permanent magnets with complex grain orientation and difficult to coat, and still obtain good magnetic properties.

[0048] Furthermore, the hot isostatic pressing process parameters in step 3 are: temperature 700-750°C, pressure 60-70MPa. Preferably, the hot isostatic pressing temperature is 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, and the pressure is 60MPa, 65MPa, 70MPa.

[0049] In order to obtain the hot-rolled permanent magnet products of the required final size and shape, it is first necessary to obtain cold-molded blanks of the corresponding shape and size, and make the blank density reach more than 60%, in preparation for the next hot isostatic pressing process to further improve the blank density, so that the blank density is greater than 99%; the blank density required for the hot rolling process must reach 100% to ensure high magnetic properties, and the cold-molded blank density can only reach 60-70%. In order to further improve the density, a cold-molded blank hot isostatic pressing process is required; during the hot isostatic pressing process, if the temperature and pressure are too low, the required density will not be achieved, and if the temperature and pressure are too high, the rare earth liquid phase will overflow and affect the magnetic properties.

[0050] Furthermore, the uncoated vacuum hot rolling in step 4 comprises the following steps:

[0051] S4-1, heating: the full density blank obtained in step 3 is placed in a continuous hot rolling equipment, and vacuumized to 10 -3 Pa and filled with argon, then quickly heated to 800 °C;

[0052] S4-2, hot rolling: the heated full-density blank enters the vacuum rolling mill chamber and is hot rolled at 800-850°C to obtain a rolled permanent magnet;

[0053] S4-3, leveling and bending: after rolling, the permanent magnet enters the leveling roller and the bending roller for leveling and bending;

[0054] S4-4, cooling: after flattening and flat bending, the magnet enters a cooling chamber and is cooled to room temperature at a rate of 5-10°C / min to obtain anisotropic hot-rolled permanent magnet products with the required shape and size and orientation parallel to the rolling direction.

[0055] It is worth noting that the heating method in step S4-1 is vacuum induction heating. Vacuum induction heating has a fast heating speed, which prevents the magnet grains from growing during the heating process and affecting the magnetic properties.

[0056] Furthermore, during the hot rolling process in step S4-2, the roller pressure is 2 to 5 tons, and the roller speed is 2 to 5 meters per minute. Preferably, the roller pressure is 2 tons, 3 tons, 4 tons, 5 tons, the roller speed is 2, 3, 4, 5 meters per minute, and the hot rolling temperature is 800, 810, 820, 830, 840, 850°C.

[0057] Specifically, during the hot rolling process of step S4-2, the reduction ratio of the full-density blank is between 60% and 75%. Preferably, the reduction ratio of the full-density blank is 60%, 65%, 70%, or 75%.

[0058] Step S4-2, during the hot rolling process, it is necessary to control the appropriate hot rolling temperature, roller pressure and hot rolling speed; if the temperature is too high, the grains will grow rapidly and affect the coercive force performance, while if the temperature is too low, the rotation orientation of the grains will be affected, especially in the tile-shaped and tubular permanent magnet blanks, which are constrained by the rolling force and the grain orientation is more complicated, resulting in low residual magnetic properties; if the hot rolling speed is too fast, that is, the deformation rate is too fast, some grains will not have time to orient and affect the magnetic properties; if the roller pressure is too small, the permanent magnet will not reach a reduction shrinkage ratio of 60-75% and affect the magnetic properties.

[0059] It should be noted that the process conditions of the leveling and bending process in step S4-3 are: roller speed 2 to 10 m / min, roller spacing size is the same as the hot rolling roller spacing size, and temperature is 800 to 850°C; the permanent magnet after hot rolling will be deformed due to the rolling pressure, and after rolling, the permanent magnet enters the leveling roller and the bending roller for leveling and bending.

[0060] Exemplarily, the cooling speed in step S4-4 is controlled at 5-10°C / min. If the speed is too slow, the cooling time will be long and the squareness of the demagnetization curve will be affected. If the speed is too fast, the permanent magnet will easily crack. Preferably, the cooling speed is 5, 7, 8, 9, or 10°C / min.

[0061] The hot-rolled permanent magnet of the required shape and size described in step S4-4 is obtained by changing the shape of the rolling roller.

[0062] Preferably, the hot-rolled permanent magnet can be prepared into a plate shape, a tile shape, or a tube shape. The size requirements of hot-rolled permanent magnets of different shapes are: plate shape, length 50-200 mm × width 50-100 mm × height 2-10 mm; tile shape, radius R10-50 mm × height 50-200 mm × wall thickness 2-10 mm; tube shape, diameter Ф20-100 mm × height 50-200 mm × wall thickness 2-10 mm.

[0063] It is worth noting that the entire hot rolling process is carried out continuously in a hot rolling equipment in a vacuum environment, and finally anisotropic high-performance RE-Ga-M-Fe-B hot-rolled permanent magnet with rheological orientation of grains is obtained, and the maximum magnetic energy product of the magnet is greater than 38MGOe.

[0064] In summary, the present invention optimizes the design of rare earth permanent magnet components to improve the high-temperature thermal deformation ability of permanent magnets, and can perform continuous hot rolling operations to ensure the performance and quality of permanent magnets during continuous hot rolling. The method for preparing permanent magnets by vacuum hot rolling RE-Ga-M-Fe-B full-density blanks without coating has a simple process, and the blank temperature is easy to control and heated evenly, which solves the problem that grain rheology permanent magnets cannot be produced on an industrial scale. The vacuum hot rolling temperature, speed, roller pressure and other parameters are optimized and precisely controlled to obtain plate-shaped, tile-shaped, and tubular high-performance permanent magnets with high density, high orientation, good corrosion resistance, and good temperature stability.

[0065] The hot-rolled rare earth permanent magnet and the preparation method of the present invention are described below with reference to specific embodiments.

[0066] Example 1 and Comparative Examples 1 to 6 are plate-shaped hot-rolled rare earth permanent magnets, Example 2 and Comparative Examples 7 to 12 are tile-shaped hot-rolled rare earth permanent magnets, and Example 3 and Comparative Examples 13 to 18 are tubular hot-rolled rare earth permanent magnets.

[0067] Embodiment 1-1, 1-2

[0068] This embodiment provides a hot-rolled rare earth permanent magnet and a preparation method thereof.

[0069] The composition of permanent magnets is expressed in mass percentage: Nd 28 Pr 3 Ga 0.6 Co 4 Cu 0.5 Fe 63 B 0.9

[0070] The specific preparation process is as follows:

[0071] Step 1: Prepare magnetic powder that meets the composition requirements: According to the designed composition ratio, prepare rapid quenching magnetic powder with a particle size of 100-200 mesh.

[0072] Step 2, cold molding: the quick-quenching magnetic powder is evenly loaded into the cold press mold for cold molding, and pressed into a plate-shaped blank at a pressure greater than 100 MPa. The blank size is: 76×46×26 mm, and the density of the blank reaches 65%.

[0073] Step 3, hot isostatic pressing: place the molded Nd-Fe-B plate blank on a grid support and put it into a hot isostatic pressing device; the process parameters are: the temperature is set at 750°C, the pressure is set at 70MPa, and argon is used for hot isostatic pressing to obtain a shrunken plate blank, the blank size is: 50×30×17mm, and the blank density reaches 100%.

[0074] Step 4: Vacuum continuous hot rolling:

[0075] S4-1. Place the full density blank after hot isostatic pressing in a continuous professional hot rolling equipment and pre-evacuate to 10 -3 Pa is filled with argon gas, and then the temperature is quickly raised to 800°C using vacuum induction heating;

[0076] S4-2, the heated blank enters the vacuum rolling mill chamber, and the temperature is controlled at 800°C (Example 1-2) and 830°C (Example 1-1) for rolling process. During the rolling process, the blank does not need to be covered for protection, the roller pressure is controlled at 3 tons, and the roller speed is controlled at 4 meters / minute for hot rolling operation, and a 100×50×5mm plate-shaped magnet with a reduction ratio of about 70% is obtained;

[0077] S4-3, the plate-shaped magnet after rolling enters the leveling roller for leveling process, the roller speed is 5 m / min, the roller spacing size is the same as the hot rolling roller spacing size, and the temperature is 800-850°C to complete the leveling process;

[0078] S4-4. The flattened magnet enters a cooling chamber and is cooled to room temperature at a cooling rate of 5°C / min (Example 1-1) and 10°C / min (Example 1-2), respectively, to obtain a plate-shaped hot-rolled permanent magnet.

[0079] The magnetic properties of the hot-rolled magnets obtained in Example 1-1 and Example 1-2 and the results of adjustment of related process parameters are shown in Table 1.

[0080] It can be seen from Examples 1-1 and 1-2 that a plate-shaped hot-rolled permanent magnet with excellent magnetic properties can be obtained by using the method of the present invention for vacuum hot rolling.

[0081] Comparative Examples 1 to 6

[0082] The permanent magnets and preparation methods provided in Comparative Examples 1 to 6 have the same composition and shape as those in Examples 1-1 and 1-2.

[0083] The difference between Comparative Example 1 and Example 1 is that the hot rolling process in step 4 is different, a metal outer layer is used for coating, and a muffle furnace is used for heating.

[0084] The difference between Comparative Example 2 and Example 1 is that the heating method in step 4 (1) is different, and a vacuum molybdenum belt furnace is used for heating.

[0085] The difference between Comparative Example 3 and Example 1 is that the hot rolling temperature in step 4 (2) is different;

[0086] Comparative Example 3-1 adopts a hot rolling temperature of 900°C;

[0087] Comparative Example 3-2 adopted a hot rolling temperature of 750°C.

[0088] The difference between Comparative Example 4 and Example 1 is that the rolling speed and rolling pressure in step 4 (2) are different;

[0089] Comparative Example 4-1 uses a rolling speed of 10 m / min and a rolling pressure of 3 tons;

[0090] Comparative Example 4-2 adopts a rolling speed of 4 m / min and a rolling pressure of 1 ton.

[0091] The difference between Comparative Example 5 and Example 1 is that the pressure and temperature of hot isostatic pressing in step 3 are different;

[0092] Comparative Example 5-1 adopts a hot isostatic pressing process at 100 MPa and 750°C;

[0093] Comparative Example 5-2 adopts a hot isostatic pressing process at 70 MPa and 650°C.

[0094] The difference between Comparative Example 6 and Example 1 is that the hot isostatic pressing process in step 3 is not performed.

[0095] The obtained magnetic properties of the magnet and the related process parameter adjustment results are shown in Table 1.

[0096] As can be seen from Table 1, the outer layer coating in Comparative Example 1 requires processes such as metal shape processing, welding sealing and vacuum coating sealing in order to perform hot rolling in the atmosphere. The coated permanent magnet requires a long period of temperature diffusion to be evenly heated, resulting in grain growth that affects performance. The heated coated sample needs to be manually clamped out and then fed into the rolling mill, and the cooling rate is relatively fast, which affects performance. Therefore, the metal outer layer coating process is complicated and cannot be continuously rolled. It can only be used for laboratory research and is not suitable for large-scale industrial production.

[0097] In Comparative Example 2, a vacuum molybdenum strip furnace is used for heating. Although hot rolling operation can be performed continuously, this heating method requires a long thermal diffusion time to heat the permanent magnet blank evenly, which will cause grain growth and affect magnetic properties.

[0098] Comparative Examples 3-1 and 3-2 use hot rolling temperatures of 900°C and 750°C, respectively, which exceed the optimal rolling temperature range required by the present invention. Too high a temperature will cause the grains to grow rapidly and affect the coercive force performance, while a low temperature will affect the rotation orientation of the grains and the residual magnetic properties will be low.

[0099] In comparative example 4-1, a rolling process of 10 m / min is adopted, and its rolling speed exceeds the hot rolling speed range of the present invention. The hot rolling speed is too fast, that is, the deformation rate is too fast, so that some grains do not have time to orient themselves and thus affect the magnetic properties. In addition, in comparative example 4-2, a rolling roller pressure of 1 ton is adopted, as a result, the permanent magnet cannot reach the reduction shrinkage ratio in the present invention and thus affects the magnetic properties.

[0100] In Comparative Example 5-1, a hot isostatic pressing process of 100 MPa was used. Due to the excessive pressure, some liquid phase of the magnet overflowed, resulting in changes in composition and affecting the magnetic properties. In Comparative Example 5-2, a hot isostatic pressing process of 650°C was used. Due to the low temperature, the density of the blank after pressing was low, affecting the magnetic properties.

[0101] In Comparative Example 6, the cold molded blank was directly heated and then hot rolled without hot isostatic pressing. Similarly, due to the low density of the initial blank, the magnetic properties of the permanent magnet after hot rolling were ultimately affected.

[0102] The above comparative examples further illustrate that the vacuum hot rolling method of the present invention can continuously and rapidly perform hot rolling operations, and finally obtain high-performance plate-shaped hot-rolled permanent magnets with grain rheological orientation, and can also achieve large-scale industrial production. For the cooling rate of the magnet after hot rolling, Examples 1-1 and 1-2 are set at 5 and 10°C / min, and both obtain ideal magnetic properties. If the speed is too slow, the cooling time will be long and the squareness of the demagnetization curve will be affected. If the speed is too fast, the magnet is prone to cracking.

[0103] Table 1 Magnetic properties of hot-rolled permanent magnets and main adjustment process parameters

[0104]

[0105] Embodiment 2-1, 2-2

[0106] This embodiment provides a hot-rolled rare earth permanent magnet and a preparation method thereof.

[0107] The composition of permanent magnets is expressed in mass percentage: Nd 28 Dy 2 Ga 0.4 Co 5.5 Al 0.5 Fe 62.7 B 0.9 ; Step 1, prepare magnetic powder that meets the composition requirements: according to the designed composition ratio, prepare rapid quenching magnetic powder with a particle size of 100-200 mesh.

[0108] Step 2, cold molding: The quick-quenching magnetic powder is evenly loaded into the cold press mold for cold molding, and pressed into a tile-shaped blank at a pressure greater than 100MPa. The blank size is: R30 (black length: 28) × height 110 × wall thickness 22mm, and the density of the blank reaches 65%.

[0109] Step 3, hot isostatic pressing: Place the molded Nd-Fe-B blank on a grid support and put it into a hot isostatic pressing device. The process parameters are: the temperature is set at 750℃, the pressure is set at 70MPa, and argon is used for hot isostatic pressing to obtain a shrinkage tile-shaped blank. The blank size is: R30 (black length: 18) × height 70 × wall thickness 14mm. The blank density reaches 100%.

[0110] Step 4: Vacuum continuous hot rolling:

[0111] S4-1. Place the full density blank after hot isostatic pressing in a continuous professional hot rolling equipment and pre-evacuate to 10 -3 Pa is filled with argon gas, and then the temperature is quickly raised to 800°C using vacuum induction heating;

[0112] S4-2, the heated blank enters the vacuum rolling mill chamber, and the temperature is controlled at 800°C (Example 2-2) and 830°C (Example 2-1) for rolling process. During the rolling process, the blank does not need to be covered for protection, the roller pressure is controlled at 3 tons, and the roller speed is controlled at 4 meters / minute for hot rolling operation, and a R30×100×4mm thick magnet with a reduction ratio of about 70% is obtained;

[0113] S4-3, the rolled magnet enters the leveling roller for leveling process, and the roller speed is 5 m / min, the roller spacing size is the same as the hot rolling roller spacing size, and the temperature is 800-850°C to complete the leveling process.

[0114] S4-4. The flattened magnet enters a cooling chamber and is cooled to room temperature at a cooling rate of 5°C / min (Example 2-1) and 10°C / min (Example 2-2).

[0115] The magnetic properties of the hot-rolled permanent magnets obtained in Example 2-1 and Example 2-2 and the results of adjustment of related process parameters are shown in Table 2.

[0116] It can be seen from Examples 2-1 and 2-2 that the tile-shaped hot-rolled permanent magnet with excellent magnetic properties can be obtained by using the method of the present invention for vacuum hot rolling.

[0117] Comparative Examples 7 to 12

[0118] The permanent magnets and preparation methods provided in Comparative Examples 7 to 12 have the same composition and shape as those in Examples 2-1 and 2-2.

[0119] The difference between Comparative Example 7 and Example 2 is that the hot rolling process in step 4 is different, a metal outer layer is used for coating, and a muffle furnace is used for heating.

[0120] The difference between Comparative Example 8 and Example 2 is that the heating method in step 4 (1) is different, and a vacuum molybdenum belt furnace is used for heating.

[0121] The difference between Comparative Example 9 and Example 2 is that the hot rolling temperature in step 4(2) is different;

[0122] Comparative Example 9-1 adopts a hot rolling temperature of 900°C;

[0123] Comparative Example 9-2 adopted a hot rolling temperature of 750°C.

[0124] The difference between Comparative Example 10 and Example 2 is that the rolling speed and rolling pressure in step 4 (2) are different;

[0125] Comparative Example 10-1 uses a rolling speed of 10 m / min and a rolling pressure of 3 tons;

[0126] Comparative Example 10-2 adopts a rolling speed of 4 m / min and a rolling pressure of 1 ton.

[0127] The difference between Comparative Example 11 and Example 2 is that the pressure and temperature of hot isostatic pressing in step 3 are different;

[0128] Comparative Example 11-1 adopts a hot isostatic pressing process at 100 MPa and 750°C;

[0129] Comparative Example 11-2 adopts a hot isostatic pressing process at 70 MPa and 650°C.

[0130] The difference between Comparative Example 12 and Example 2 is that the hot isostatic pressing process in step 3 is not performed.

[0131] The obtained magnetic properties of the magnet and the related process parameter adjustment results are shown in Table 2.

[0132] As can be seen from Table 2, the outer layer coating used in Comparative Example 7 requires processes such as metal shape processing, welding sealing and vacuum coating sealing in order to perform hot rolling operations under the atmosphere. The coated permanent magnets require a long period of temperature diffusion to be evenly heated, resulting in grain growth that affects performance. The heated coated samples need to be manually clamped out and then fed into the rolling mill, and the cooling rate is relatively fast, which affects performance. Therefore, the metal outer layer coating process is complicated and cannot be continuously rolled. It can only be used for laboratory research and is not suitable for large-scale industrial production.

[0133] In Comparative Example 8, a vacuum molybdenum strip furnace is used for heating. Although hot rolling operation can be performed continuously, this heating method requires a long thermal diffusion time to heat the permanent magnet blank evenly, which will cause grain growth and affect magnetic properties.

[0134] Comparative Examples 9-1 and 9-2 use hot rolling temperatures of 900°C and 750°C, respectively, which exceed the optimal rolling temperature range required by the present invention. Too high a temperature will cause the grains to grow rapidly and affect the coercive force performance, while a low temperature will affect the rotation orientation of the grains, resulting in low residual magnetic properties. In particular, the tile-shaped permanent magnet blank is constrained by the rolling force, and the grain orientation is more complicated, resulting in low residual magnetic properties.

[0135] Comparative Example 10-1 adopts a rolling process of 10 m / min, and its rolling speed exceeds the hot rolling speed range of the present invention. The hot rolling speed is too fast, that is, the deformation rate is too fast, so that some grains do not have time to orient themselves and affect the magnetic properties. In addition, Comparative Example 10-2 adopts a 1-ton rolling roller pressure, as a result, the magnet cannot reach the reduction shrinkage ratio of the present invention and affects the magnetic properties.

[0136] In comparative example 11-1, a hot isostatic pressing process of 100 MPa was adopted. Due to the excessive pressure, some liquid phase of the magnet overflowed, resulting in changes in composition and affecting the magnetic properties. In comparative example 11-2, a hot isostatic pressing process of 650°C was adopted. Due to the low temperature, the density of the blank after pressing was low, affecting the magnetic properties.

[0137] In Comparative Example 12, the cold molded blank was directly heated and then hot rolled without hot isostatic pressing. Similarly, due to the low density of the initial blank, the magnetic properties of the magnet after hot rolling were ultimately affected.

[0138] The above comparative examples further illustrate that the vacuum hot rolling method of the present invention can not only perform hot rolling operations continuously and quickly, and finally obtain high-performance tile-shaped hot-rolled permanent magnets with grain rheological orientation, but also realize large-scale industrial production. For the cooling rate of the magnet after hot rolling, Examples 2-1 and 2-2 are set at 5 and 10°C / min, and both obtain ideal magnetic properties. However, if the speed is too slow, the cooling time will be long and the squareness of the demagnetization curve will be affected. If the speed is too fast, the magnet is prone to cracking.

[0139] Table 2 Magnetic properties and main adjustment process parameters of tile-shaped hot-rolled permanent magnets

[0140]

[0141] Embodiment 3-1, 3-2

[0142] This embodiment provides a hot-rolled rare earth permanent magnet and a preparation method thereof.

[0143] The composition of permanent magnets is expressed in mass percentage: Nd 25 Ce 3 Dy 4 Ga 0.8 Co 5.8 Ti 0.2 Fe 60.3 B 0.9

[0144] Step 1: Prepare magnetic powder that meets the composition requirements: According to the designed composition ratio, prepare rapid quenching magnetic powder with a particle size of 100-200 mesh.

[0145] Step 2, cold molding: the quick-quenching magnetic powder is evenly loaded into the cold press mold for cold molding, and pressed into a tubular blank at a pressure greater than 100 MPa. The blank size is: 98 mm × height 110 mm × wall thickness 22 mm, and the density of the blank reaches 65%.

[0146] Step 3, hot isostatic pressing: Place the molded Nd-Fe-B blank on a grid support and put it into a hot isostatic pressing device. The process parameters are: the temperature is set at 750℃, the pressure is set at 70MPa, and argon is used for hot isostatic pressing to obtain a tubular blank. The blank size is: 64mm × height 70mm × wall thickness 14mm, and the blank density reaches 100%.

[0147] Step 4: Vacuum continuous hot rolling:

[0148] S4-1. Place the full density blank after hot isostatic pressing in a continuous professional hot rolling equipment and pre-evacuate to 10 -3 Pa is filled with argon gas, and then the temperature is quickly raised to 800°C using vacuum induction heating;

[0149] S4-2, the heated blank enters the vacuum rolling mill chamber, and the temperature is controlled at 800°C (Example 3-2) and 830°C (Example 3-1) for rolling process. During the rolling process, the blank does not need to be covered for protection, the roller pressure is controlled at 3 tons, and the roller speed is controlled at 4 meters / minute for hot rolling operation, and a magnet with a reduction ratio of about 70% and a size of 50×100×4 mm in thickness is obtained;

[0150] S4-3, the rolled magnet enters the leveling roller for leveling process, and the roller speed is 5 m / min, the roller spacing size is the same as the hot rolling roller spacing size, and the temperature is 800-850°C to complete the leveling process.

[0151] S4-4. The flattened magnet enters a cooling chamber and is cooled to room temperature at a cooling rate of 5°C / min (Example 3-1) and 10°C / min (Example 3-2).

[0152] The magnetic properties of the hot-rolled permanent magnets obtained in Example 3-1 and Example 3-2 and the results of adjustment of related process parameters are shown in Table 3.

[0153] It can be seen from Examples 3-1 and 3-2 that a tubular hot-rolled permanent magnet with excellent magnetic properties can be obtained by using the method of the present invention for vacuum hot rolling.

[0154] Comparative Examples 13 to 18

[0155] The permanent magnets and preparation methods provided in Comparative Examples 13 to 18 have the same composition and shape as those in Examples 3-1 and 3-2.

[0156] The difference between Comparative Example 13 and Example 3 is that the hot rolling process in step 4 is different, a metal outer layer is used for coating, and a muffle furnace is used for heating.

[0157] The difference between Comparative Example 14 and Example 3 is that the heating method of step 4 (1) is different, and a vacuum molybdenum belt furnace is used for heating.

[0158] The difference between Comparative Example 15 and Example 3 is that the hot rolling temperature in step 4 (2) is different;

[0159] Comparative Example 15-1 adopts a hot rolling temperature of 900°C;

[0160] Comparative Example 15-2 adopted a hot rolling temperature of 750°C.

[0161] The difference between Comparative Example 16 and Example 3 is that the rolling speed and rolling pressure in step 4 (2) are different;

[0162] Comparative Example 16-1 uses a rolling speed of 10 m / min and a rolling pressure of 3 tons;

[0163] Comparative Example 16-2 uses a rolling speed of 4 m / min and a rolling pressure of 1 ton.

[0164] The difference between Comparative Example 17 and Example 3 is that the pressure and temperature of hot isostatic pressing in step 3 are different;

[0165] Comparative Example 17-1 adopts a hot isostatic pressing process at 100 MPa and 750°C;

[0166] Comparative Example 17-2 adopts a hot isostatic pressing process at 70 MPa and 650°C.

[0167] The difference between Comparative Example 19 and Example 3 is that the hot isostatic pressing process in step 3 is not performed.

[0168] The obtained magnetic properties of the magnet and the related process parameter adjustment results are shown in Table 2.

[0169] As can be seen from Table 2, the outer layer coating used in Comparative Example 13 requires processes such as metal shape processing, welding sealing and vacuum coating sealing in order to perform hot rolling operations in the atmosphere. The coated magnets require a long period of temperature diffusion to be evenly heated, resulting in grain growth that affects performance. The heated coated samples need to be manually clamped out and then fed into the rolling mill, and the cooling rate is relatively fast, which affects performance. Therefore, the metal outer layer coating process is complicated and cannot be continuously rolled. It can only be used for laboratory research and is not suitable for large-scale industrial production.

[0170] In Comparative Example 14, a vacuum molybdenum strip furnace is used for heating. Although hot rolling operation can be performed continuously, this heating method requires a long thermal diffusion time to heat the magnet blank evenly, which will cause grain growth and affect the magnetic properties.

[0171] Comparative Examples 15-1 and 15-2 use hot rolling temperatures of 900°C and 750°C, respectively, which exceed the optimal rolling temperature range required by the present invention. Too high a temperature will cause the grains to grow rapidly and affect the coercive force performance, while a low temperature will affect the rotation orientation of the grains, resulting in low residual magnetic properties. In particular, the tubular permanent magnet blank is constrained by the rolling force, and the grain orientation is more complicated, resulting in low residual magnetic properties.

[0172] Comparative Example 16-1 adopts a rolling process of 10 m / min, and its rolling speed exceeds the hot rolling speed range of the present invention. The hot rolling speed is too fast, that is, the deformation rate is too fast, so that some grains do not have time to orient themselves and affect the magnetic properties. In addition, Comparative Example 16-2 adopts a 1-ton rolling roller pressure, as a result, the magnet cannot reach the reduction shrinkage ratio of the present invention and affects the magnetic properties.

[0173] In Comparative Example 17-1, a hot isostatic pressing process of 100 MPa was adopted. Due to the excessive pressure, some liquid phase of the magnet overflowed, resulting in changes in composition and affecting the magnetic properties. In Comparative Example 17-2, a hot isostatic pressing process of 650°C was adopted. Due to the low temperature, the density of the blank after pressing was low, affecting the magnetic properties.

[0174] In Comparative Example 18, the cold molded blank was directly heated and then hot rolled without hot isostatic pressing. Similarly, due to the low density of the initial blank, the magnetic properties of the magnet after hot rolling were ultimately affected.

[0175] The above comparative examples further illustrate that the vacuum hot rolling method of the present invention can not only perform hot rolling operations continuously and quickly, and finally obtain high-performance tubular hot-rolled permanent magnets with grain rheological orientation, but also realize large-scale industrial production. For the cooling rate of the magnet after hot rolling, Examples 3-1 and 3-2 are set at 5 and 10°C / min, and both obtain ideal magnetic properties. If the speed is too slow, the cooling time will be long and the squareness of the demagnetization curve will be affected. If the speed is too fast, the magnet is prone to cracking.

[0176] Table 3 Magnetic properties of tubular hot-rolled permanent magnets and main adjustment process parameters

[0177]

[0178] In summary, the present invention optimizes the design of rare earth permanent magnet components to improve the high-temperature thermal deformation ability of permanent magnets, and can perform continuous hot rolling operations to ensure the performance and quality of permanent magnets during continuous hot rolling. The method for preparing permanent magnets by vacuum hot rolling RE-Ga-M-Fe-B full-density blanks without coating has a simple process, and the blank temperature is easy to control and heated evenly, which solves the problem that grain rheology permanent magnets cannot be produced on an industrial scale. The vacuum hot rolling temperature, speed, roller pressure and other parameters are optimized and precisely controlled to obtain plate-shaped, tile-shaped, and tubular high-performance permanent magnets with high density, high orientation, good corrosion resistance, and good temperature stability.

[0179] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A hot-rolled rare earth permanent magnet, characterized in that: The permanent magnet has a general formula of RE a Ga b M c Fe d B e ,in, RE is one or more of Nd, Pr, Ce, La or Dy; M is one or more of Co, Cu, Al, Zr, Ti, Nb; the mass fraction is expressed in percentage as follows: 28.0≤a≤32.0; 0.2≤b≤0.8; 3.0≤c≤6.0; 0.8≤e≤1.1; d=100-abce.

2. A method for preparing a hot-rolled rare earth permanent magnet, characterized in that: The permanent magnet composition according to claim 1 is prepared, comprising the following steps: Step 1, preparation of RE-Ga-M-Fe-B rapid quenching magnetic powder; Step 2, cold molding: the quick-quenching magnetic powder prepared in step 1 is evenly loaded into a cold press mold for cold molding at a pressure greater than 100 MPa to obtain a blank with a density of more than 60%; Step 3, hot isostatic pressing: under vacuum or argon protection, the rough part of step 2 is subjected to hot isostatic pressing to obtain an isotropic full-density rough part; Step 4, uncoated vacuum hot rolling: the full-density blank of step 3 is continuously vacuum hot rolled without coating, and the hot rolling temperature is 800-900° C. to obtain a hot-rolled permanent magnet product.

3. The preparation method according to claim 2, characterized in that: The preparation method of the RE-Ga-M-Fe-B rapid quenching magnetic powder described in step 1 comprises the following steps: S1-1. According to the designed composition ratio, the alloy raw materials are subjected to vacuum induction melting at a melting temperature of 1400° C. to 1500° C. to obtain an alloy ingot; S1-2, the alloy ingot obtained in S1 is rapidly quenched to obtain a rapidly quenched thin strip, the roller surface linear speed of the rapidly quenching roller is 25-50 m / s, and the average grain size of the rapidly quenched thin strip is 30-300 nm; S1-3, mechanically crushing the quick-quenching thin strip obtained in S2 into quick-quenching magnetic powder with an average particle size of 100-200 mesh.

4. The preparation method according to claim 2, characterized in that: The full-density blank in step 3 is in the shape of a plate, a tile or a tube.

5. The preparation method according to claim 2, characterized in that: The hot isostatic pressing process parameters in step 3 are: temperature 700-750° C., pressure 60-70 MPa.

6. The preparation method according to claim 2, characterized in that: The uncoated vacuum hot rolling in step 4 comprises the following steps: S4-1, heating: the full density blank obtained in step 3 is placed in a continuous hot rolling equipment, and vacuumized to 10 -3 Pa and filled with argon, then quickly heated to 800 °C; S4-2, hot rolling: the heated full-density blank enters the vacuum rolling mill chamber and is hot rolled at 800-850°C to obtain a rolled permanent magnet; S4-3, leveling and bending: after rolling, the permanent magnet enters the leveling roller and the bending roller for leveling and bending; S4-4, cooling: after flattening and flat bending, the magnet enters a cooling chamber and is cooled to room temperature at a rate of 5-10°C / min to obtain anisotropic hot-rolled permanent magnet products with the required shape and size and orientation parallel to the rolling direction.

7. The preparation method according to claim 6, characterized in that: The heating method in step S4-1 is vacuum induction heating.

8. The preparation method according to claim 6, characterized in that: During the hot rolling process in step S4-2, the roller pressing force is 2 to 5 tons and the roller speed is 2 to 5 meters per minute.

9. The preparation method according to claim 8, characterized in that: During the hot rolling process of step S4-2, the reduction ratio of the full-density blank is between 60% and 75%.

10. The preparation method according to claim 6, characterized in that: The process conditions of the leveling and bending process in step S4-3 are: roller speed 2 to 10 m / min, roller spacing size is the same as the hot rolling roller spacing size, and temperature is 800 to 850°C.

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