A sintered NdFeB magnet and its preparation method

Abstract

The present invention relates to the technical field of powder metallurgy, and in particular to a sintered NdFeB and a preparation method thereof, wherein the heat treatment temperature and time are adjusted to promote the RE6Fe 13 The M phase is generated or disappears, thereby increasing or decreasing the remanence and coercivity of the magnet; specifically, by composition design or adding RE6Fe to the grain boundary 13 The M phase alloy composition is then adjusted to 420‑700°C heat treatment temperature to promote RE6Fe 13 The M phase is formed or disappears. This method can regulate the changes in remanence and coercivity within a certain range to improve the redundancy of the formulation process, and at the same time can better adapt to the different performance requirements of customers, with excellent economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, in particular to sintered NdFeB and a preparation method thereof. Background Art

[0002] Sintered NdFeB has a record-breaking magnetic energy product. Due to its high magnetic flux density, it meets the current requirements for miniaturization, thinness and high efficiency of magnetic devices. It is widely used in new energy, IT electronics, rail transportation, aerospace and other fields.

[0003] Remanence and coercivity are two key parameters used to define the performance of a magnetic material. The remanence parameter directly affects the magnetic energy product of the magnet, that is, the magnetic field strength and storage capacity. For a specific magnetic circuit, too high or too low remanence will have an adverse effect. It is generally required that the remanence be controlled within a small fluctuation range. The coercivity parameter is an important indicator for evaluating its anti-demagnetization ability. In order to avoid irreversible loss of magnets due to factors such as high temperature, a certain amount of redundant coercivity is usually required.

[0004] In the sintered NdFeB preparation technology system, under fixed formula and process, the remanence and coercive force of the magnet are usually unchanged, but are affected by the composition, process and structure. For example, combination with oxygen, nitrogen, carbon, etc. will lead to irreversible performance degradation. Although it can be remedied by designing a certain amount of redundancy and using technologies such as grain boundary diffusion, it will also increase unnecessary quality costs.

[0005] Therefore, finding a method that can regulate the changes in remanence and coercive force within a certain range to improve the redundancy of the formulation process and better meet the different performance requirements of customers has important value and economic benefits. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention promotes the main phase of NdFeB and RE6Fe 13 The present invention provides a sintered NdFeB magnet and a preparation method thereof, which are specifically achieved through the following technical solutions.

[0007] A sintered NdFeB magnet containing RE6Fe 13 The raw material ratio of M phase is as follows: 29-35% RE, 0.81-0.95% B, 0.2-2.0% M, 0.5-1.5% N, Fe; 100ω B : 100ω Fe =1.32-1.37, (ω Re -26.68*ω B ):ω M ≥5.

[0008] Furthermore, the RE is one or more rare earth elements; the M is one or more of Al, Cu, and Ga mixed in any proportion; and the N is one or more of Zr, Ti, Nb, Mo, Ta, Co, and Ni mixed in any proportion.

[0009] Furthermore, the magnet contains RE6Fe 13 M phase, the raw material ratio is as follows: 29-35% RE, 0.81-0.95% B, 0.2-2.0% M, 0.5-1.5% N, Fe balance; the magnet can be prepared by single alloy or double alloy, at least one of the double alloys can form RE6Fe 13 M phase.

[0010] The preparation method of sintered NdFeB is to adjust RE6Fe 13 The volume fraction of the M phase is used to adjust the remanence and coercivity of the magnet. Specifically, RE6Fe can be formed by composition design or grain boundary addition. 13 M phase alloy composition, and then promote RE6Fe by heat treatment in the grain boundary phase transformation temperature range 13 The M phase is formed or disappears.

[0011] Furthermore, by adjusting the heat treatment temperature and time, RE6Fe 13 The M phase is generated or disappears, thereby increasing or decreasing the remanence and coercive force of the magnet.

[0012] Furthermore, the grain boundary phase transition temperature ranges from 400 to 750°C.

[0013] Further, the specific steps include:

[0014] (1) Vacuum melting; (2) Hydrogen crushing treatment; (3) Air flow grinding; (4) Magnetic field forming; (5) Vacuum sintering; (6) Vacuum heat treatment.

[0015] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0016] The sintered NdFeB and the preparation method thereof of the present invention can regulate the changes of remanence and coercive force within a certain range to improve the redundancy of the formulation process, and at the same time can better adapt to the different performance requirements of customers and have excellent economic benefits. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0018] Example 1

[0019] Nominal composition (mass ratio): (Pr+Nd) 29%, B 0.95%, Ga 0.25%, Cu 0.15%, Zr 0.15%, Co 0.35%, Fe balance. The raw materials are melted at 1400-1500℃ in a vacuum rapid solidification melting furnace to form a NdFeB alloy with an average thickness of 0.27-0.30mm. The alloy is subjected to hydrogen crushing treatment to fully absorb hydrogen and then vacuum heated for dehydrogenation treatment to a hydrogen content of less than 1000ppm. Subsequently, the alloy is pulverized into 2-4 micron powder by air flow milling under nitrogen protection, and then pressed in a magnetic field above 1.5T. Subsequently, the alloy is sintered at 1000-1100℃ and subjected to primary aging treatment at 850-950℃, and then treated at a grain boundary phase transition temperature of 700℃ for 6h, and quenched to room temperature to obtain a NdFeB magnet.

[0020] Example 2

[0021] Nominal composition (mass ratio): (Pr+Nd) 29%, B 0.95%, Ga 0.25%, Cu 0.15%, Zr 0.15%, Co 0.35%, Fe balance. The raw materials are melted at 1400-1500℃ in a vacuum rapid solidification melting furnace to form a NdFeB alloy with an average thickness of 0.27-0.30mm. The alloy is subjected to hydrogen crushing treatment to fully absorb hydrogen and then vacuum heated for dehydrogenation treatment to a hydrogen content of less than 1000ppm. Subsequently, the alloy is pulverized into 2-4 micron powder by air flow milling under nitrogen protection, and then pressed and formed in a magnetic field above 1.5T. Subsequently, the alloy is sintered at 1000-1100℃ and subjected to primary aging treatment at 850-950℃, and then treated at a grain boundary phase transition temperature of 420℃ for 6h, and quenched to room temperature to obtain a NdFeB magnet.

[0022] Example 3

[0023] Nominal composition (mass ratio): (Pr+Nd) 35%, B 0.81%, Ga 0.75%, Cu 0.5%, Al 0.75%, Zr0.1%, Ti 0.1%, Co 1.3%, Fe balance. The raw materials are melted at 1400-1500℃ in a vacuum rapid solidification melting furnace to form a NdFeB alloy with an average thickness of 0.27-0.30mm. The alloy is subjected to hydrogen crushing treatment to fully absorb hydrogen and then vacuum heated for dehydrogenation treatment to a hydrogen content of less than 2000ppm. Subsequently, it is pulverized into 2-4 micron powder by air flow milling under nitrogen protection, and then pressed into shape in a magnetic field above 1.5T. Subsequently, it is sintered at 1000-1100℃ and subjected to primary aging treatment at 850-950℃, and then treated at a grain boundary phase transition temperature of 650℃ for 5h, and quenched to room temperature to obtain a NdFeB magnet.

[0024] Example 4

[0025] Nominal composition (mass ratio): (Pr+Nd) 35%, B 0.81%, Ga 0.75%, Cu 0.5%, Al 0.75%, Zr0.1%, Ti 0.1%, Co 1.3%, Fe balance. The raw materials are melted at 1400-1500℃ in a vacuum rapid solidification melting furnace to form a NdFeB alloy with an average thickness of 0.27-0.30mm. The alloy is subjected to hydrogen crushing treatment to fully absorb hydrogen and then vacuum heated for dehydrogenation treatment to a hydrogen content of less than 2000ppm. Subsequently, it is pulverized into 2-4 micron powder by air flow milling under nitrogen protection, and then pressed into shape in a magnetic field above 1.5T. Subsequently, it is sintered at 1000-1100℃ and subjected to primary aging treatment at 850-950℃, and then treated at a grain boundary phase transition temperature of 450℃ for 5h, and quenched to room temperature to obtain a NdFeB magnet.

[0026] Example 5

[0027] Nominal composition (mass ratio): (Pr+Nd) 32%, B 0.88%, Ga 0.50%, Cu 0.35%, Al 0.30%, Zr 0.1%, Ti 0.1%, Co 0.8%, Fe balance. The composition of alloy 1 is (Pr+Nd) 30.26%, B 0.93%, Ga0.26%, Cu 0.11%, Al 0.05%, Zr 0.1%, Co0.85%, Fe balance. The composition of alloy 2 is Pr 65%, Ga 5%, Cu 5%, Al 5%, Ti 0.2%, Fe 18%. The raw materials are smelted into alloys at 1400-1500°C in a vacuum rapid solidification melting furnace, mixed in a ratio of alloy 1: alloy 2 = 95:5, subjected to hydrogen crushing treatment to fully absorb hydrogen, and then subjected to vacuum heating dehydrogenation treatment to a hydrogen content of less than 1000ppm, and then ground into 2-4 micron powder by air flow milling under nitrogen protection, pressed into shape in a magnetic field above 1.5T, and then sintered at 1000-1100°C and subjected to primary aging treatment at 850-950°C, and then treated at a grain boundary phase transition temperature of 600°C for 5h, and quenched to room temperature to obtain a NdFeB magnet.

[0028] Example 6

[0029] Nominal composition (mass ratio): (Pr+Nd) 32%, B 0.88%, Ga 0.50%, Cu 0.35%, Al 0.30%, Zr 0.1%, Ti 0.1%, Co 0.8%, Fe balance. The composition of alloy 1 is (Pr+Nd) 30.26%, B 0.93%, Ga0.26%, Cu 0.11%, Al 0.05%, Zr 0.1%, Co0.85%, Fe balance. The composition of alloy 2 is Pr 65%, Ga 5%, Cu 5%, Al 5%, Ti 0.2%, Fe 18%.

[0030] The raw materials are smelted into alloys at 1400-1500°C in a vacuum rapid solidification melting furnace, mixed in a ratio of alloy 1: alloy 2 = 95:5, subjected to hydrogen crushing treatment to fully absorb hydrogen, and then subjected to vacuum heating dehydrogenation treatment to a hydrogen content of less than 1000ppm, and then ground into 2-4 micron powder by air flow milling under nitrogen protection, pressed into shape in a magnetic field above 1.5T, and then sintered at 1000-1100°C and subjected to primary aging treatment at 850-950°C, and then treated at a grain boundary phase transition temperature of 480°C for 5h, and quenched to room temperature to obtain a NdFeB magnet.

[0031] Subsequently, magnets with different remanence and coercivity were obtained at different heat treatment temperatures, as shown in the following table:

[0032]

[0033] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A sintered NdFeB magnet, characterized in that: The magnet contains RE6Fe 13 The raw material ratio of M phase is as follows: 29-35% RE, 0.81-0.95% B, 0.2-2.0% M, 0.5-1.5% N, Fe; 100ω B : 100ω Fe =1.32-1.37, (ω Re -26.68*ω B ):ω M ≥5.

2. The sintered NdFeB according to claim 1, characterized in that: The RE is one or more rare earth elements, the M is one or more of Al, Cu, and Ga mixed in any proportion; and the N is one or more of Zr, Ti, Nb, Mo, Ta, Co, and Ni mixed in any proportion.

3. The sintered NdFeB according to claim 1, characterized in that: The magnet contains RE6Fe 13 M phase, the raw material ratio is as follows: 29-35% RE, 0.81-0.95% B, 0.2-2.0% M, 0.5-1.5% N, Fe balance; the magnet can be prepared by single alloy or double alloy, at least one of the double alloys can form RE6Fe 13 M phase.

4. The method for preparing sintered NdFeB according to claim 1, characterized in that: By regulating RE6Fe 13 The volume fraction of the M phase is used to adjust the remanence and coercivity of the magnet. Specifically, RE6Fe can be formed by composition design or grain boundary addition. 13 M phase alloy components, and then promote RE6Fe by heat treatment in the grain boundary phase transformation temperature range 13 The M phase is formed or disappears.

5. The preparation method according to claim 4, characterized in that: By adjusting the heat treatment temperature and time, RE6Fe 13 The M phase is generated or disappears, thereby increasing or decreasing the remanence and coercive force of the magnet.

6. The preparation method according to claim 4, characterized in that: The grain boundary phase transition temperature ranges from 420 to 700°C.

7. The preparation method according to claim 4, characterized in that: The specific steps include: (1) Vacuum melting; (2) Hydrogen crushing treatment; (3) Air flow grinding; (4) Magnetic field forming; (5) Vacuum sintering; (6) Vacuum heat treatment.

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