A composite permanent magnet steel with gradually changing concentration of magnetic powder and a manufacturing method and application thereof

Abstract

This invention belongs to the field of magnetic materials technology, and specifically relates to a composite permanent magnet with gradually varying magnetic powder concentration, its preparation method, and its application. The composite permanent magnet with gradually varying magnetic powder concentration includes rare-earth neodymium iron boron (NdFeB) material and cerium iron boron (CFeB) material; the concentration of NdFeB material gradually increases from the middle layer towards the poles of the composite permanent magnet according to a certain gradient rule; the concentration of CFeB material gradually decreases from the middle layer towards the poles of the composite permanent magnet according to a certain gradient rule; the rare-earth NdFeB material includes NdFeB... 13.21 Fe 80.99 B 5.8 Cerium iron boron materials include Ce 19 Fe 75 B6. The permanent magnets of the present invention have a basically consistent degree of demagnetization inside and outside, and there will be no situation where the inner layer still has a large residual magnetism after demagnetization. This makes full use of high-abundance rare earth resources and reduces the use of low-abundance rare earth resources, which can promote the balanced use of rare earth resources and reduce the cost of magnets.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, and specifically relates to a composite permanent magnet with gradually varying magnetic powder concentration, its manufacturing method, and its application. Background Technology

[0002] Rare earth permanent magnet materials, especially rare earth neodymium iron boron permanent magnet materials, have been widely used in wind power generation, environmentally friendly home appliances, industrial energy-saving motors and hybrid electric vehicles since their advent.

[0003] Traditional rare-earth permanent magnets are composed of a single component. Under high-speed motor operation, eddy currents form inside the magnet, causing its temperature to rise and leading to gradual demagnetization and failure. In this case, the rare-earth permanent magnets in the motor need to be replaced, and the failed magnets are recycled or discarded. However, the eddy current effect in rare-earth magnets is caused by the skin effect during motor operation. The skin effect causes the outer layer of the rare-earth magnet to have a larger reverse demagnetizing field than the inner layer. This causes the outer layer to heat up and demagnetize first, while the inner layer, with a smaller demagnetizing field, experiences less severe demagnetization. Consequently, the inner layer of the rare-earth permanent magnet is not fully demagnetized before being recycled or discarded, resulting in the underutilization of rare-earth resources and waste. Furthermore, because neodymium is a low-abundance rare-earth element and is expensive, neodymium-iron-boron magnets are costly, while other associated high-abundance rare-earth elements are not fully utilized, leading to an imbalance in rare-earth development and utilization.

[0004] Therefore, there is an urgent need to provide a composite permanent magnet with a gradually varying magnetic powder concentration. The demagnetization degree of the permanent magnet is basically the same inside and outside, and there will be no situation where the inner layer of the demagnetized permanent magnet still has a large residual magnetism. Moreover, it makes full use of high-abundance rare earth resources and reduces the amount of low-abundance rare earth resources used, which can promote the balanced utilization of rare earth resources and reduce the cost of magnets. Summary of the Invention

[0005] This invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions. This invention provides a composite permanent magnet with gradually varying magnetic powder concentration. The degree of demagnetization inside and outside the permanent magnet is basically the same, avoiding the situation where the inner layer of the demagnetized permanent magnet still has a large amount of residual magnetism. This fully utilizes high-abundance rare earth resources, reduces the use of low-abundance rare earth resources, promotes the balanced utilization of rare earth resources, and reduces the cost of the magnet.

[0006] The inventive concept of this invention: The permanent magnet of this invention comprises rare earth neodymium iron boron (NdFeB) material and cerium iron boron (CFeB) material; the content concentration of NdFeB material gradually increases from the middle layer to the poles of the composite permanent magnet according to a certain gradient rule, and the content concentration of CFeB material gradually decreases from the middle layer to the poles of the composite permanent magnet according to a certain gradient rule; the composite permanent magnet prepared has a higher content of NdFeB in the outer layer and a higher content of CFeB in the inner layer in the pole direction. The magnetism of the outer layer is better than that of the inner layer. Because the demagnetization rate of the outer layer of the rare earth magnet is faster than that of the inner layer, the demagnetization degree of the inner and outer layers of the permanent magnet can be basically the same after demagnetization, and there will be no situation where the inner layer of the permanent magnet still has a large residual magnetism after demagnetization. In addition, since neodymium is a low-abundance rare earth element and is expensive, while cerium is a high-abundance rare earth element and is cheaper, replacing traditional single-component rare earth permanent magnets by uniformly mixing rare earth neodymium iron boron materials and cerium iron boron materials according to a method of gradually changing the content concentration can make full use of high-abundance rare earth resources, reduce the use of low-abundance rare earth resources, promote the balanced use of rare earth resources, and reduce the cost of magnets.

[0007] Therefore, a first aspect of the present invention provides a composite permanent magnet with a gradually varying magnetic powder concentration.

[0008] Specifically, a composite permanent magnet with gradually varying magnetic powder concentration includes rare earth neodymium iron boron materials and cerium iron boron materials;

[0009] The concentration of the rare earth neodymium iron boron material gradually increases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule;

[0010] The concentration of the cerium-iron-boron material gradually decreases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule.

[0011] Preferably, the rare earth neodymium iron boron material includes Nd... 13.21 Fe 80.99 B 5.8 .

[0012] Preferably, the cerium-iron-boron material includes Ce 19 Fe 75 B6.

[0013] Preferably, the rare earth neodymium iron boron material and the cerium iron boron material also independently include additives and antioxidants.

[0014] Preferably, the content of additives in the rare earth NdFeB material accounts for 0.4-0.6% of the weight of the rare earth NdFeB material.

[0015] More preferably, the content of additives in the rare earth NdFeB material accounts for 0.5% of the weight of the rare earth NdFeB material.

[0016] Preferably, the content of additives in the cerium iron boron material accounts for 0.4-0.6% of the weight of the cerium iron boron material.

[0017] More preferably, the content of additives in the cerium iron boron material accounts for 0.5% of the weight of the cerium iron boron material.

[0018] Preferably, the additive is Pr 35 Tb 35 Cu 10 Al 20 .

[0019] Preferably, the antioxidant is a phosphite.

[0020] A second aspect of the present invention provides a method for preparing a composite permanent magnet with gradually varying magnetic powder concentration.

[0021] Specifically, a method for preparing a composite permanent magnet with gradually varying magnetic powder concentration includes the following steps:

[0022] (1) Place rare earth neodymium iron boron fine powder and cerium iron boron fine powder into powder sieve A and powder sieve B respectively, and place powder sieve A and B alternately above the mold and vibrate them. The rare earth neodymium iron boron fine powder and cerium iron boron fine powder fall into the mold to obtain mixed magnetic powder.

[0023] (2) The mixed magnetic powder obtained in step (1) is oriented, pressed, isostatically pressed, and sintered to obtain permanent magnet steel.

[0024] Preferably, in step (1), the preparation process of the rare earth neodymium iron boron fine powder and cerium iron boron fine powder is as follows: the raw material components of rare earth neodymium iron boron and cerium iron boron are respectively smelted, spun, hydrogen crushed and air jet milled to obtain the rare earth neodymium iron boron fine powder and cerium iron boron fine powder.

[0025] Preferably, the raw material composition of the rare earth neodymium iron boron includes Nd. 13.21 Fe 80.99 B 5.8 .

[0026] Preferably, the raw material components of the cerium-iron-boron alloy include Ce. 19 Fe 75 B6.

[0027] Preferably, the raw material components of the rare earth neodymium iron boron and the cerium iron boron are smelted in a spinning furnace at 1400-1500°C, and the rare earth neodymium iron boron sheets and cerium iron boron sheets are obtained after spinning through copper rollers.

[0028] Preferably, during the smelting process, additive Pr can be added. 35 Tb 35 Cu 10 Al 20.

[0029] Preferably, the thickness of both the rare earth neodymium iron boron sheet and the cerium iron boron sheet is 0.25-0.5 mm.

[0030] Preferably, the hydrogen peroxide process yields rare earth neodymium iron boron coarse powder and cerium iron boron coarse powder, respectively; the fineness of both the rare earth neodymium iron boron coarse powder and the cerium iron boron coarse powder is 98-102 μm.

[0031] Preferably, antioxidants are added to the rare earth NdFeB coarse powder and the cerium iron boron coarse powder respectively, and the powder is subjected to air jet milling to obtain rare earth NdFeB fine powder and cerium iron boron fine powder; the fineness of the rare earth NdFeB fine powder and the cerium iron boron fine powder is 4μm.

[0032] Preferably, the amount of antioxidant added is 0.07-0.09% of the weight of the rare earth neodymium iron boron powder or the cerium iron boron powder.

[0033] More preferably, the amount of antioxidant added is 0.08% of the weight of the rare earth neodymium iron boron powder or the cerium iron boron powder.

[0034] Preferably, in step (1), the middle layer of the powder sieve A has no openings, and the opening diameter gradually increases from the middle layer to both sides; the two sides of the powder sieve B have no openings, and the opening diameter gradually increases from both sides to the middle layer.

[0035] Specifically, rare earth neodymium iron boron magnetic fine powder and cerium iron boron fine powder are placed in powder sieve A and powder sieve B respectively. The powder sieve A and powder sieve B are alternately placed above the mold and vibrated to obtain mixed magnetic powder in the mold in which the concentration of rare earth neodymium iron boron magnetic powder gradually increases from the middle layer to the two poles, and the concentration of cerium iron boron magnetic powder gradually decreases from the middle layer to the two poles.

[0036] Preferably, in step (2), the magnetic field for orientation pressing is 1-3T, the pressure for isostatic pressing is 220-250Mpa, and the holding time is 30-50s.

[0037] Preferably, in step (2), the sintering heat treatment is performed under vacuum conditions, wherein the vacuum degree is less than 3 × 10⁻⁶. -3 Pa, the sintering heat treatment is performed three times.

[0038] Preferably, in step (2), the green billet obtained by isostatic pressing is placed into a sintering furnace, and the vacuum degree inside the furnace is lower than 3×10⁻⁶. -3 The magnet is sintered at 1070-1080℃ for 2 hours, then cooled to room temperature to obtain a dense sintered magnet. The furnace is then evacuated to a vacuum level below 3 × 10⁻⁶. -3The furnace is sintered at 900°C for 2 hours, followed by cooling to room temperature. Finally, the furnace is evacuated to a vacuum level below 3 × 10⁻⁶. -3 Pa is sintered at a temperature of 500°C and a holding time of 2 hours, and then cooled to room temperature.

[0039] A third aspect of the present invention provides an application of a composite permanent magnet with gradually varying magnetic powder concentration in the fields of wind power generation, new energy vehicles, and home appliances.

[0040] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0041] (1) In the composite permanent magnet of the present invention, the content concentration of rare earth neodymium iron boron material gradually increases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule; the content concentration of cerium iron boron material gradually decreases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule. This makes the prepared permanent magnet with a higher content of rare earth neodymium iron boron material in the outer layer and a higher content of cerium iron boron material in the inner layer in the two pole directions. The magnetism of the outer layer is better than that of the inner layer. Since the demagnetization speed of the outer layer of the rare earth magnet is faster than that of the inner layer of the magnet, the demagnetization degree of the inner and outer layers of the permanent magnet is basically the same after demagnetization. There will be no situation where the inner layer of the permanent magnet still has a large residual magnetism after demagnetization.

[0042] (2) Since neodymium is a low-abundance rare earth and is expensive, while cerium is a high-abundance rare earth and is relatively inexpensive, this invention replaces the traditional single-component rare earth permanent magnet steel by uniformly mixing rare earth neodymium iron boron materials and cerium iron boron materials according to a method of gradually changing the content concentration. This can make full use of high-abundance rare earth resources, reduce the amount of low-abundance rare earth resources used, promote the balanced use of rare earth resources, and reduce the cost of magnet steel. Attached Figure Description

[0043] Figure 1 This is a schematic diagram showing the gradual change in magnetic powder concentration in the composite permanent magnet of the present invention;

[0044] Figure 2 This is a schematic diagram of the powder sieve A of the present invention;

[0045] Figure 3 This is a schematic diagram of the powder sieve B of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0047] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0048] Example 1

[0049] A composite permanent magnet with gradually varying magnetic powder concentration, comprising rare earth Nd 13.21 Fe 80.99 B 5.8 Materials and Cerium Iron Boron (Ce) 19 Fe 75 B6 material;

[0050] Rare earth Nd 13.21 Fe 80.99 B 5.8 The concentration of the material gradually increases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule;

[0051] Cerium iron boron (Ce) 19 Fe 75 The concentration of B6 material gradually decreases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule.

[0052] A schematic diagram illustrating the gradual change in magnetic powder content concentration in composite permanent magnets, as shown below. Figure 1 As shown.

[0053] This embodiment of a composite permanent magnet raw material with gradually varying magnetic powder concentration includes cerium iron boron magnet powder (cerium iron boron Ce). 19 Fe 75 B6) and rare earth neodymium iron boron magnet powder (rare earth Nd) 13.21 Fe 80.99 B 5.8 The two magnetic powders are mixed in a 1:1 weight ratio. Other elements may also be included, such as Ti, Al, Cu, Co, Ga, Zr, Nb, Ho, Gd, V, and Mn, with the amount added depending on the specific conditions during smelting.

[0054] A method for preparing a composite permanent magnet with gradually varying magnetic powder concentration includes the following steps:

[0055] (1) Material preparation: Prepare rare earth Nd 13.21 Fe 80.99 B 5.8 and cerium iron boron Ce 19 Fe 75 B6, additive Pr- 35 Tb 35 Cu 10 Al 20 ;

[0056] (2) Preparation of rare earth Nd 13.21 Fe80.99 B 5.8 Fine powder: rare earth Nd 13.21 Fe 80.99 B 5.8 and additive Pr- 35 Tb 35 Cu 10 Al 20 It is placed in a spinning furnace, wherein the amount of additive added is rare earth Nd. 13.21 Fe 80.99 B 5.8 0.5% of the raw material weight; rare earth Nd 13.21 Fe 80.99 B 5.8 and additive Pr 35 Tb 35 Cu 10 Al 20 The material was smelted at 1450℃ in a spinning furnace and then spun through copper rollers to obtain a sheet with a thickness of 0.4 mm. After hydrogen crushing, the sheet was used to obtain a coarse powder with a fineness of 100 μm. Approximately 0.08% by weight of phosphite antioxidant was added to the coarse powder, and the powder was then pulverized in an air jet mill to obtain rare earth Nd with a fineness of 4 μm. 13.21 Fe 80.99 B 5.8 powder;

[0057] (3) Preparation of cerium iron boron (Ce) 19 Fe 75 B6 fine powder: Cerium iron boron (Ce) 19 Fe 75 B6 and additive Pr 35 Tb 35 Cu 10 Al 20 It is placed in a spinning furnace, wherein the amount of additive added is cerium iron boron (Ce). 19 Fe 75 0.5% by weight of B6 raw material; Cerium iron boron (Ce) 19 Fe 75 B's raw materials and additives Pr 35 Tb 35 Cu 10 Al 20 The material was smelted at 1450℃ in a spinning furnace and then spun through copper rollers to obtain a sheet with a thickness of 0.4 mm. After hydrogen crushing, the sheet was used to obtain a coarse powder with a fineness of 100 μm. Approximately 0.08% by weight of phosphite antioxidant was added to the coarse powder, and the powder was then pulverized in an air jet mill to obtain cerium iron boron (Ce) with a fineness of 4 μm. 19 Fe 75 B6 fine powder;

[0058] (4) Preparation of mixed magnetic powder: rare earth Nd 13.21Fe 80.99 B 5.8 Fine powder and cerium iron boron Ce 19 Fe 75 B6 fine powder was alternately placed in a 10*10*10mm green mold at a 1:1 ratio. Specifically, 100g of rare earth Nd2 was taken from each mold. 13.21 Fe 80.99 B 5.8 Fine powder is placed in sieve A and mixed with 100g of cerium iron boron (Ce). 19 Fe 75 B6 fine powder is placed in sieve B. First, sieve A is placed above the green mold and vibrated at a frequency of 15 times / s for 10 seconds to allow the rare earth Nd2 to pass through. 13.21 Fe 80.99 B 5.8 The fine powder falls into the mold, and then the powder sieve B is placed above the green mold and vibrated at a frequency of 15 times / s for 10 seconds, so that the cerium iron boron Ce... 19 Fe 75 B6 fine powder falls into the mold, and powder sieves A and B are alternately placed above the green mold until the mixed powder is filled in, thus obtaining rare earth Nd in the mold. 13.21 Fe 80.99 B 5.8 The concentration of magnetic powder gradually increases from the middle layer to the poles, with cerium iron boron (Ce) content increasing. 19 Fe 75 B6 is a mixture of magnetic powders whose magnetic powder concentration gradually decreases from the middle layer towards the poles. Schematic diagrams of sieves A and B are shown below. Figure 2 and 3 As shown;

[0059] (5) Compression molding: The mixed powder in the mold is oriented and pressed in a 2T magnetic field, and then isostatically pressed in a cold isostatic press to produce a powder with a density of 4 g / cm³. 3 The green billet, wherein the isostatic pressing pressure is 220 MPa and the isostatic pressing holding time is 30 s;

[0060] (6) Sintering heat treatment: Place the green billet obtained in step (5) into a sintering furnace and evacuate the furnace to a vacuum of 2×10⁻⁶. -3 The magnet was sintered at Pa, with the sintering heat treatment temperature at 1075℃ and the holding time at 1075℃ for 2 hours, followed by cooling to room temperature to obtain a dense sintered magnet; then the furnace was evacuated to a vacuum of 2×10⁻⁶. -3 The furnace is sintered at Pa, with a sintering heat treatment temperature of 900℃ and a holding time of 2 hours, followed by cooling to room temperature; finally, the furnace is evacuated to a vacuum of 2×10⁻⁶. -3 The composite permanent magnet steel 45SH- was obtained by sintering Pa at a temperature of 500℃ and a holding time of 2h. After cooling to room temperature, the composite permanent magnet steel was obtained.

[0061] Performance testing: The permanent magnet was tested for magnetic properties, and the results were: BR = 13.2 kGs, Hcj = 19.5 kOe.

[0062] In permanent magnet equipment with large usage and non-ultra-high precision requirements, the 45SH-permanent magnet steel obtained by this invention can replace standard pure NdFeB permanent magnet steel, with a cost of only about 70% of that of standard pure NdFeB permanent magnet steel. Especially in large permanent magnet motors, the density of the magnetic field on the surface of the magnet steel is mainly utilized. However, the demagnetization rate of the outer layer of rare earth magnet steel is faster than that of the inner layer. The outer layer of the permanent magnet steel of this invention has better magnetism than the inner layer, making the degree of demagnetization of the permanent magnet steel basically the same inside and outside, and avoiding the situation where the inner layer of the permanent magnet steel still has a large residual magnetism after demagnetization. In addition, by uniformly mixing rare earth NdFeB materials and cerium iron boron materials according to a gradual change in content concentration to replace the traditional single-component rare earth permanent magnet steel, the high-abundance rare earth resources are fully utilized and the usage of low-abundance rare earth resources is reduced, which can promote the balanced utilization of rare earth resources, reduce the cost of magnet steel, and promote the popularization and development of permanent magnet equipment.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite permanent magnet with gradually varying magnetic powder concentration, characterized in that, Including rare earth neodymium iron boron materials and cerium iron boron materials; The concentration of the rare earth neodymium iron boron material gradually increases from the middle layer to the two poles of the composite permanent magnet according to a certain gradient rule; The concentration of the cerium iron boron material gradually decreases from the middle layer toward the two poles of the composite permanent magnet according to a certain gradient rule. The rare earth neodymium iron boron material includes Nd... 13.21 Fe 80.99 B 5.8 ; The cerium iron boron material includes Ce 19 Fe 75 B6; The method for preparing the composite permanent magnet with gradually varying magnetic powder concentration includes the following steps: (1) Place rare earth neodymium iron boron fine powder and cerium iron boron fine powder into powder sieve A and powder sieve B respectively, and place powder sieve A and powder sieve B alternately above the mold and vibrate them. The rare earth neodymium iron boron fine powder and cerium iron boron fine powder fall into the mold to obtain mixed magnetic powder. (2) The mixed magnetic powder obtained in step (1) is oriented, pressed, isostatically pressed, and sintered to obtain the composite permanent magnet steel; In step (1), the middle layer of the powder sieve A has no openings, and the opening diameter gradually increases from the middle layer to both sides; the two sides of the powder sieve B have no openings, and the opening diameter gradually increases from both sides to the middle layer.

2. The composite permanent magnet according to claim 1, characterized in that, The rare earth neodymium iron boron materials and cerium iron boron materials also independently include additives and antioxidants.

3. The composite permanent magnet according to claim 2, characterized in that, The additive is Pr 35 Tb 35 Cu 10 Al 20 The antioxidant is a phosphite.

4. The method for preparing the composite permanent magnet with gradually varying magnetic powder concentration as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Place rare earth neodymium iron boron fine powder and cerium iron boron fine powder into powder sieve A and powder sieve B respectively, and place powder sieve A and powder sieve B alternately above the mold and vibrate them. The rare earth neodymium iron boron fine powder and cerium iron boron fine powder fall into the mold to obtain mixed magnetic powder. (2) The mixed magnetic powder obtained in step (1) is oriented, pressed, isostatically pressed, and sintered to obtain the composite permanent magnet steel; In step (1), the middle layer of the powder sieve A has no openings, and the opening diameter gradually increases from the middle layer to both sides; the two sides of the powder sieve B have no openings, and the opening diameter gradually increases from both sides to the middle layer.

5. The preparation method according to claim 4, characterized in that, In step (1), the preparation process of the rare earth neodymium iron boron magnetic fine powder and cerium iron boron fine powder is as follows: the raw material components of rare earth neodymium iron boron and cerium iron boron are respectively smelted, spun, hydrogen crushed and air jet milled to obtain the rare earth neodymium iron boron fine powder and cerium iron boron fine powder.

6. The preparation method according to claim 4, characterized in that, In step (2), the magnetic field for orientation pressing is 1-3T; the pressure for isostatic pressing is 220-250MPa; the holding time for isostatic pressing is 30-50s; and the number of sintering heat treatments is three.

7. The application of the composite permanent magnet with gradually varying magnetic powder concentration as described in any one of claims 1-3 in the fields of wind power generation, new energy vehicles, and home appliances.

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