Method for preparing lanthanum-cerium-added neodymium-iron-boron magnet

Abstract

The application discloses a preparation method of a lanthanum-cerium-added neodymium-iron-boron magnet, and belongs to the field of magnet preparation. According to a certain element proportion, R1 and R2 alloys are prepared by using a vacuum spinning belt furnace. After the two kinds of alloys are subjected to hydrogen treatment, two kinds of powders with different particle sizes are respectively obtained, the two kinds of powders are mixed according to a certain proportion, and the magnet is obtained through the processes of forming and orientation, cold isostatic pressing, sintering and aging. The magnet prepared by the method has high performance.

Description

Technical Field

[0001] This invention relates to the field of magnet manufacturing, and more particularly to a method for preparing a lanthanum-cerium-added neodymium iron boron magnet. Background Technology

[0002] The addition of highly abundant light rare earth elements is an important means of reducing the material cost of NdFeB magnets. However, because highly abundant rare earth elements, such as lanthanum and cerium, have relatively low magnetic property parameters, their addition leads to a significant decrease in magnetic properties. (Nd₂Fe) 14 B's J s (Magnetic polarization) is 1.61T, H A (Magnetocrystalline anisotropic field) is 73 kOe; Pr2Fe 14 B's J s It is 1.56T, H A It is 75 kOe; while La2Fe 14 B's J s It is 1.38T, H A 20kOe; Ce2Fe 14 B's J s It is 1.17T, H A The value is 26 kOe. To minimize the impact of adding elements such as lanthanum and cerium on the magnetic properties of rare-earth magnetic materials, the industry has recently adopted methods such as multi-phase processes, surface grain boundary diffusion, and intergranular addition to optimize magnets. Chinese patent CN102800454A, entitled "Low-Cost Dual-Phase Ce Permanent Magnet Alloy and Its Preparation Method," describes a method that utilizes two different H phases: Nd-Fe-B and (Ce,Re)-Fe-B. A The main phase of the (Ce,Re)-Fe-B phase in this method achieves higher magnetic properties. However, the H content of the (Ce,Re)-Fe-B main phase in this method is... A Excessive reduction limits the improvement of magnetic properties. Chinese patent CN106710768A, entitled "A Method for Adding Coercivity to Sintered Magnets of NdH₂," builds upon a dual-phase process by adding NdH₂. X One method involves forming a hard magnetic layer of Nd on the outer layer of NdFeB using powder to enhance the magnetocrystalline anisotropy field, effectively improving coercivity. However, this method requires preparing three powders and then mixing them, making the process complex. Furthermore, the added NdHx powder needs to be considered for dehydrogenation during the sintering process, further increasing the difficulty. The patented method (CN102842400B, titled "Method for Preparing Low-Cost Sintered NdFeB with Lanthanum and Cerium Doping") replaces the NdFeB-rich phase with specially processed lanthanum and cerium powder, preventing excessive incorporation of lanthanum and cerium into the NdFeB main phase, thus improving product performance while reducing costs. However, lanthanum and cerium are among the most reactive rare earth elements, and lanthanum and cerium powder is highly susceptible to oxidation and nitridation, affecting the addition effect.

[0003] However, the production process of lanthanum-cerium powder is quite difficult and the process control cost is relatively high. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a method for preparing lanthanum-cerium-added neodymium iron boron magnets, so as to solve the problem that the magnet performance is too low after adding light rare earth elements lanthanum or cerium.

[0005] Technical solution: To achieve the above objectives, the present invention provides a method for preparing a lanthanum-cerium-added neodymium iron boron magnet, comprising the following steps:

[0006] Step (S1) Prepare R1 alloy and R2 alloy by mixing materials according to the proportion and using a vacuum belt spinning furnace. The R1 alloy contains La and / or Ce elements, and the R2 alloy contains 33.10-35.00 wt.% of rare earth elements Pr and / or Nd. The R2 alloy does not contain La and / or Ce elements.

[0007] In step (S2), after R1 alloy and R2 alloy are treated by hydrogen absorption and dehydrogenation processes, they are ground into powder by air jet milling. After air jet milling, the average particle size of R1 alloy powder and R2 alloy powder satisfies the following relationship: 0.32≤R2 alloy powder particle size / R1 alloy powder particle size≤0.66.

[0008] Step (S3) involves mixing the two alloy powders;

[0009] The powder mixed in step (S4) is then molded and oriented, and then cold isostatically pressed, sintered, and aged to produce magnets.

[0010] As a preferred embodiment, the total rare earth element content in the R1 alloy described in step (S1) is 29.00-31.00 wt.%.

[0011] Furthermore, in the rare earth elements of the R1 alloy, the content of La and / or Ce is 6.00-20.00 wt.%, and the remainder is Nd and / or Pr.

[0012] As a preferred embodiment, in step (S2), the average particle size range of the R1 alloy powder is 3.1-5.5 μm, and the average particle size range of the R2 alloy powder is 1.0-3.6 μm.

[0013] As a preferred embodiment, in step (S1), the R1 alloy and R2 alloy include, but are not limited to, elements such as B, Co, Cu, Ga, Ti, Al, and Fe.

[0014] As a preferred embodiment, in step (S3), the mixing ratio of R1 alloy powder and R2 alloy powder is 1:1.

[0015] The present invention discloses a method for preparing a lanthanum-cerium-added neodymium iron boron magnet, which has at least the following technical effects: The lanthanum-cerium-free R2 alloy powder has a high total rare earth content, forming a large amount of praseodymium-neodymium phase. Simultaneously, due to the small average particle size of the alloy powder, it can better coat the outer periphery of the large lanthanum-cerium particles. The praseodymium-neodymium phase introduced by the small particle coating can diffuse to the outer periphery of the large lanthanum-cerium particles during sintering and aging, forming a hard magnetic layer on the outer side of the large particles, improving the magnetic properties of the lanthanum-cerium main phase, and weakening the magnetic property deterioration caused by the addition of lanthanum-cerium. This method limits the particle size ratio of the two alloy powders to obtain a better coating effect, limits the rare earth content of the two alloys to produce a suitable rare earth concentration gradient, and ensures that the praseodymium-neodymium phase can fully coat the outer side of the lanthanum-cerium particles. Attached Figure Description

[0016] Figure 1 Diagram illustrating the structural mechanism of neodymium iron boron magnets added to lanthanum and cerium. Detailed Implementation

[0017] The following combination Figure 1 The principles and features of the present invention are described, and the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0018] Example 1

[0019] Step (S1) involves preparing alloys R1 and R2 using a vacuum spinning furnace according to the specified proportions. The R1 alloy contains the following elemental composition (mass percentage): 23.00% Nd, 6.00% Ce, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R2 alloy contains the following elemental composition (mass percentage): 35.00% Pr, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R1 and R2 alloys are then separately processed into thin alloy strips using a vacuum spinning furnace.

[0020] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 5.5 μm, and R2 alloy is ground into powder with an average particle size of 3.6 μm.

[0021] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0022] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0023] Example 2

[0024] Step (S1) involves preparing alloys R1 and R2 using a vacuum spinning furnace according to the specified proportions. The R1 alloy contains the following elements (mass percentage): 8.8% Nd, 2.2% Pr, 10% Ce, 10.00% La, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R2 alloy contains the following elements (mass percentage): 26.5% Nd, 6.6% Pr, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R1 and R2 alloys are then separately processed into thin alloy strips using a vacuum spinning furnace.

[0025] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 3.1 μm, and R2 alloy is ground into powder with an average particle size of 1.0 μm.

[0026] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0027] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0028] Example 3

[0029] Step (S1) involves preparing alloys R1 and R2 using a vacuum spinning furnace according to the specified proportions. The R1 alloy contains the following elements (mass percentage): 18% Pr, 12% La, 0.95% B, 1% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R2 alloy contains the following elements (mass percentage): 34% Nd, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R1 and R2 alloys are then separately processed into thin alloy strips using a vacuum spinning furnace.

[0030] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 4.0 μm, and R2 alloy is ground into powder with an average particle size of 2.0 μm.

[0031] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0032] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0033] The rare earth element content in R1 alloy and R2 alloy in Examples 1 to 3 is shown in Table 1. The particle size of R1 alloy powder and R2 alloy powder and the magnetic properties of the resulting magnets in Examples 1 to 3 are shown in Table 2.

[0034] Table 1 shows the rare earth element content of the alloys in the examples.

[0035]

[0036] Table 2: Alloy Powder Particle Size and Magnetic Properties in Examples

[0037]

[0038]

[0039] Comparative Example 1

[0040] Step (S1) involves preparing alloys R1 and R2 using a vacuum spinning furnace according to the specified proportions. The R1 alloy contains the following elemental composition (mass percentage): 23.00% Nd, 6.00% Ce, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R2 alloy contains the following elemental composition (mass percentage): 35.00% Pr, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R1 and R2 alloys are then separately processed into thin alloy strips using a vacuum spinning furnace.

[0041] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 3.6 μm, and R2 alloy is ground into powder with an average particle size of 3.6 μm.

[0042] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0043] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0044] Comparative Example 2

[0045] According to the specified proportions, alloys R1 and R2 were prepared using a vacuum strip spinning furnace. The elements and their contents (by mass percentage) in alloy R1 were: 26.00% Nd, 6.00% Ce, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The elements and their contents (by mass percentage) in alloy R2 were: 32.00% Pr, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. Alloys R1 and R2 were then processed into thin alloy strips using a vacuum strip spinning furnace.

[0046] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 5.5 μm, and R2 alloy is ground into powder with an average particle size of 3.6 μm.

[0047] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0048] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0049] Comparative Example 3

[0050] Step (S1) involves preparing alloys R1 and R2 using a vacuum spinning furnace according to the specified proportions. The R1 alloy contains the following elements (mass percentage): 7.2% Nd, 1.8% Pr, 11% Ce, 11.00% La, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R2 alloy contains the following elements (mass percentage): 26.5% Nd, 6.6% Pr, 0.95% B (boron), 1.00% Co, 0.60% Al, 0.15% Cu, 0.40% Ga, 0.15% Ti, with the balance being Fe and unavoidable impurities. The R1 and R2 alloys are then separately processed into thin alloy strips using a vacuum spinning furnace.

[0051] In step (S2), after conventional hydrogen absorption and dehydrogenation processes, R1 alloy is ground into powder with an average particle size of 3.1 μm, and R2 alloy is ground into powder with an average particle size of 1 μm.

[0052] Step (S3) involves mixing R1 alloy powder and R2 alloy powder, wherein the weight percentage of R1 alloy powder and R2 alloy powder is 50.0% each.

[0053] After the mixture in step (S4) is homogeneous, it undergoes molding, orientation, and cold isostatic pressing. Then, it is sintered at 1030℃ for 5 hours, cooled to room temperature, heated to 850℃ and held for 3 hours, cooled to room temperature, and then heated to 500℃ and held for 3 hours. The resulting sample is then subjected to magnetic property testing.

[0054] The rare earth element content in the alloys of Comparative Examples 1 to 3 is shown in Table 3, and the particle size of the alloy powder and the magnetic properties of the resulting magnets of Comparative Examples 1 to 3 are shown in Table 4.

[0055] Table 3 Rare Earth Element Content in Comparative Alloys

[0056]

[0057] Table 4 Comparative alloy powder particle size and magnetic properties

[0058]

[0059] As can be seen from the above, when the final cerium content of the magnet in Example 1 is 3.00 wt.%, the Br content is 12.45 kGs and the Hcj content is 19.35 kOe; when the final lanthanum and cerium content of the magnet in Example 2 is 10.00 wt.%, the Br content is 12.05 kGs and the Hcj content is 16.13 kOe; and when the final lanthanum content of the magnet in Example 3 is 6.00 wt.%, the Br content is 12.43 kGs and the Hcj content is 17.05 kOe. It can be seen that good magnetic properties can be obtained under the conditions defined by the present invention.

[0060] Example 1 has the same composition as Comparative Example 1, but the particle sizes of alloy R1 and alloy R2 in Example 1 are 5.5 μm and 3.6 μm, respectively. The two alloy powders have a suitable particle size difference, which allows for the formation of a better coating structure. The final magnet's magnetic properties are Br 12.45 kGs and Hcj 19.35 kOe. In Comparative Example 1, the average particle size of both R1 and R2 alloy powders is 3.6 μm. Although the average particle size of R1 alloy powder is finer than that of Comparative Example 1, the coercivity of the final magnet is not as high as that of Example 1. This is because in Comparative Example 1, there is no particle size difference between R1 and R2 alloy powders, making it difficult to form a structure with sufficient praseodymium-neodymium phase coating. Consequently, it is difficult to form an effective hard magnetic layer around the lanthanum-cerium main phase particles through element diffusion during sintering and heat treatment. Compared to Example 1, Comparative Example 2 has consistent particle sizes for R1 and R2 alloy powders, and the total rare earth content and cerium content after mixing are also consistent. However, the total rare earth content of the R2 alloy in Comparative Example 2 was low, at only 32.00 wt.%, resulting in a low amount of praseodymium-neodymium phase in the R2 powder. Even though a coating structure was formed through the particle size difference between R1 and R2 powders, there was insufficient praseodymium-neodymium phase to coat the outer surface of the lanthanum-cerium particles, making it difficult to form a sufficient hard magnetic layer during the sintering and aging process. Ultimately, the Br content was 12.34 kGs and the Hcj content was 18.27 kOe, which were lower than the magnetic properties of Example 1. The poor magnetic properties of Comparative Example 3 were mainly due to the excessive amount of lanthanum and cerium added, which reduced the magnetic parameters of the magnet. At the same time, excessive lanthanum and cerium addition easily generated impurity phases, resulting in lower macroscopic magnetic properties.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a lanthanum-cerium-added neodymium iron boron magnet, characterized in that, Includes the following steps: Step (S1) involves mixing the materials according to a specified ratio and preparing R1 alloy and R2 alloy using a vacuum belt spinning furnace. The R1 alloy contains La and / or Ce elements, while the R2 alloy does not contain La and / or Ce elements. The total rare earth element content of the R1 alloy is 29.00-31.00 wt.%, of which the content of La and / or Ce is 6.00-20.00 wt.%, and the remainder is Nd and / or Pr; the R2 alloy contains 33.10-35.00 wt.% of rare earth elements Pr and / or Nd. In step (S2), after R1 alloy and R2 alloy are treated by hydrogen absorption and dehydrogenation processes, they are ground into powder by air jet milling. After air jet milling, the average particle size of R1 alloy powder and R2 alloy powder satisfies the following relationship: 0.32≤R2 alloy powder particle size / R1 alloy powder particle size≤0.

66. Step (S3) Mix R1 alloy powder and R2 alloy powder at a weight ratio of 1:1; In step (S4), the mixed powder is molded and oriented, then cold isostatically pressed, sintered, and aged to produce a magnet.

2. The method for preparing a lanthanum-cerium-added neodymium iron boron magnet according to claim 1, characterized in that, In step (S2), the average particle size range of the R1 alloy powder is 3.1-5.5 μm, and the average particle size range of the R2 alloy powder is 1.0-3.6 μm.

3. The method for preparing a lanthanum-cerium-added neodymium iron boron magnet according to claim 1, characterized in that, In step (S1), the R1 alloy and R2 alloy include, but are not limited to, B, Co, Cu, Ga, Ti, Al and Fe elements.

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