Magnetic material and method of manufacture

Abstract

The application discloses a kind of magnetic materials, it is characterized in that: the mass percentage composition of the magnetic material is RE:29~32wt%, B:0.8~1.0wt%, Ga:0.01~0.6wt%, A:0.1~0.5wt%, T:0.01~2.0wt%, wherein, A is selected from at least one of Si and Ge, T is selected from at least one of Al, Cu, Co, Zr, Ti, the balance is Fe and inevitable impurities.In the magnetic material, add A element, A element improves the resistivity of material while flowing in the sintering process, improves the density of magnetic material, not easy to form hole, while realizing high coercivity, the remanence of the alloy of the application is above 13kGs, intrinsic coercivity is above 21kOe, resistivity is above 900Ω·mm 2 / m.

Description

Technical Field

[0001] This invention pertains to magnetic materials, specifically relating to a magnetic material and its preparation method. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are widely used in new energy vehicles, variable frequency air conditioners, and industrial motors due to their high energy product. These applications require magnets to operate at high temperatures, demanding high-temperature resistance. There are two main ways to improve the temperature resistance of magnets: one is to increase the coercivity, primarily by adding heavy rare earth elements (Tb or Dy) to enhance the magnetocrystalline anisotropy field. However, due to the scarcity and high cost of Dy and Tb, this method increases magnet costs. Furthermore, since the atomic magnetic moments of Tb and Dy are antiparallel to those of Fe, their addition reduces remanence, thus limiting the manufacture of high-performance, high-coercivity magnets. The other approach is to increase the resistivity of the magnet. NdFeB magnets used in permanent magnet motors operate in alternating magnetic field environments, easily generating heat due to eddy currents, which reduces the magnet's coercivity. Since the heat generated by eddy currents is directly related to the magnet's resistivity, increasing the resistivity improves its temperature resistance.

[0003] Oxide powders, such as calcium oxide, silicon oxide, aluminum oxide, or fluoride powders, are usually added to magnets to increase their resistivity. However, when these impurity powders are mixed with NdFeB magnetic powder and then sintered, there are problems such as poor compatibility between the added powders and NdFeB magnetic powders, high melting points, and difficulty in flowing during the sintering process, resulting in low magnet density, easy formation of pores, and decreased remanence of the magnet. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a magnetic material with excellent coercivity and resistivity.

[0005] The technical solution adopted by the present invention to solve the first technical problem is: a magnetic material, characterized in that: the mass percentage composition of the magnetic material is RE: 29-32 wt%, B: 0.8-1.0 wt%, Ga: 0.01-0.6 wt%, A: 0.1-0.5 wt%, T: 0.01-2.0 wt%, wherein A is selected from at least one of Si and Ge, T is selected from at least one of Al, Cu, Co, Zr, and Ti, and the balance is Fe and unavoidable impurities.

[0006] Preferably, A is selected from Si and Ge, and the mass ratio of Si to Ga is 1:(2-5).

[0007] As preferred, the phase organization of the magnetic material comprises 2:14:1 phase and grain boundary phase distributed at the grain boundary of the 2:14:1 phase, wherein the grain boundary phase comprises RE-rich phase and R-T-Ga phase. The 2:14:1 phase is the matrix phase, ensuring the remanence performance of the material, and the RE-rich phase and R-T-Ga phase distributed in the grain boundary phase isolate the 2:14:1 phase grains, improving the resistivity and coercivity of the magnetic material. The A element is distributed in the R-T-Ga phase, the R-T-Ga phase has a high resistivity due to the semiconductor Si or Ge, and the R-T-Ga phase is a non-magnetic phase distributed on the grain boundary, thereby enhancing the demagnetization coupling effect, improving the coercivity, and reducing the A element entering the 2:14:1 phase to replace part of Fe, ensuring the remanence performance of the 2:14:1 phase.

[0008] To achieve a balance between remanence and coercivity, as preferred, the area content of the grain boundary phase in the phase organization is 3-20%, and the R-T-Ga phase accounts for 20-50% of the area content of the grain boundary phase. If the R-T-Ga phase accounts for less than 20% of the area content of the grain boundary phase, the coercivity of the magnetic material will be reduced, and if the R-T-Ga phase accounts for more than 50% of the area content of the grain boundary phase, the remanence of the magnetic material will be reduced.

[0009] The second technical problem to be solved by the present application is to provide a preparation method of a magnetic material.

[0010] The technical scheme adopted by the present application to solve the second technical problem is: a preparation method of a magnetic material, characterized by comprising the following preparation steps:

[0011] 1) batching: batching according to the required ingredients, including alloy M and alloy N, wherein the element composition of the alloy M is RE, B, Ga, and Fe, and the element composition of the alloy N is RE, Ga, T, and A, wherein RE is selected from Pr and / or Nd; the alloy M and the alloy N are mixed to form a mixture;

[0012] 2) powder preparation: after hydrogen absorption and then hydrogen desorption treatment of the mixture, the mixture is powdered under a protective atmosphere, the protective gas contains 20-100 ppm of oxygen, and the balance is nitrogen; the average particle size of the powder is 1.5-3 μm;

[0013] 3) compression molding: the powder is oriented under a magnetic field with a strength of 1.5-3.0 T, and then compressed into a blank under a nitrogen protective atmosphere;

[0014] 4) sintering: the sintering temperature is 1000-1100°C, the holding time is 6-10 h, and the sintering vacuum degree is 2-5×10 -3 Pa;

[0015] 5) tempering: the temperature is decreased to 850-950 DEG C, the holding time is 1-3 h, then the temperature is decreased to 500-600 DEG C, and the holding time is 2-6 h.

[0016] In alloy M, Si or Ge is not added, so that the two elements do not enter the 2:14:1 phase during smelting, and the remanence of the magnetic material is reduced.

[0017] The element composition of alloy N is RE, Ga, T, and A, RE is selected from Pr and / or Nd, the melting point of alloy N is between 650 DEG C and 900 DEG C, so that the alloy N can be distributed continuously on the grain boundary in the melting point range, and the coercivity of the R-T-Ga phase is improved.

[0018] In order to improve the resistivity of the magnetic material and thus improve the coercivity, the protective gas contains 20-100 ppm of oxygen. The average particle size of the powder is 1.5-3 microns, which is equivalent to the average grain size of the columnar crystal in alloy M, so that the powder particles are wrapped with the rare earth-rich phase, which improves the coercivity and reduces the risk of grain growth.

[0019] The sintering temperature is 1000-1100 DEG C, and a too high sintering temperature causes the 2:14:1 phase grains to grow during the dissolution and precipitation and recombination process, and the smaller the powder particle size, the more the grains will abnormally grow, thereby reducing the coercivity of the magnet. A low sintering temperature will result in a low density of the magnet, which will cause the performance of the magnet to deteriorate.

[0020] In order to realize fine grains of alloy M and N, as a preferred embodiment, in step 1), the alloy M and N are in a quenched state, the smelting temperature of the alloy M is 1450-1500 DEG C, and the smelting temperature of the alloy N is 1000-1400 DEG C, and both are solidified at a cooling speed of ≥1000 DEG C / s.

[0021] As a preferred embodiment, in step 2), the mixing is dehydrogenated at a temperature below 500 DEG C.

[0022] Compared with the prior art, the advantages of the present application are that the A element is added to the magnetic material, the A element improves the resistivity of the material, and is easy to flow during sintering, improves the density of the magnetic material, and is not easy to form pores, realizes high coercivity, and improves the remanence of the material. The remanence of the alloy of the present application is above 13 kGs, the intrinsic coercivity is above 21 kOe, and the resistivity is above 900 (Ω·mm / m). 2 BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is an electron microscope photo of the present application example 2.

[0024] Figure 2 It is an electron microscope photo of the present application comparative example 2. ​DETAILED DESCRIPTION

[0025] The application will be further described in detail in connection with the following examples with reference to the accompanying drawings.

[0026] The application provides three examples and three comparative examples, and the specific components are shown in Table 1.

[0027] The preparation steps of Example 1 are as follows:

[0028] 1) ingredient preparation: ingredients are prepared according to the required components, including alloy M and alloy N, wherein, in terms of weight percentage, the composition of alloy M is Pr 7.5 Nd 22.5 Al 0.25 Cu 0.1 Ga 0.2 Zr 0.1 Fe 68.42 B 0.93 , and the composition of alloy N is Pr 30 Nd 55 Al2Cu5Ga4Si4; alloy M and alloy N are in quenched state, the smelting temperature of alloy M is 1450-1500℃, the smelting temperature of alloy N is 1200-1300℃, the cooling speed of alloy M is 1000℃ / s, and the cooling speed of alloy N is 1100℃ / s; alloy M and alloy N are mixed to form a mixture;

[0029] 2) powder preparation: the mixture is hydrogenated and then dehydrogenated at 450℃, and the mixture is powdered in a protective atmosphere containing 70ppm of oxygen and the balance of nitrogen; the average particle size of the powder is 2.86μm;

[0030] 3) compression molding: the powder is oriented under a magnetic field with a strength of 2.0T, and then compressed into a blank under a nitrogen protective atmosphere;

[0031] 4) sintering: the sintering temperature is 1060℃, the holding time is 6h, and the sintering vacuum degree is 5×10 -3 Pa;

[0032] 5) tempering: the temperature is reduced to 900℃, the holding time is 2h, then the temperature is reduced to 540℃, and the holding time is 4h.

[0033] The preparation steps of Example 2 are as follows:

[0034] 1) ingredient preparation: ingredients are prepared according to the required components, including alloy M and alloy N, wherein, in terms of weight percentage, the composition of alloy M is Pr 7.125 Nd 21.375 Dy1Al 0.2 Cu 0.1 Ga 0.2 Zr 0.1 Fe 68.95B 0.95 , alloy N is Pr 30 Nd 55 Al2Cu5Ga4Si4; alloy M and alloy N are in quenched state, the smelting temperature of alloy M is 1450-1500℃, the smelting temperature of alloy N is 1200-1300℃, the cooling speed of alloy M is 1500℃ / s, the cooling speed of alloy N is 1100℃ / s, alloy M and alloy N are mixed to form a mixture;

[0035] 2) powder preparation: the mixture is treated by hydrogen absorption and then dehydrogenation at 480℃, the mixture is powdered in a protective atmosphere, the protective gas contains 60ppm of oxygen and the balance is nitrogen; the average particle size of the powder is 2.95μm;

[0036] 3) pressing forming: the powder is oriented under a magnetic field with a magnetic field strength of 2.0T, and then pressed into a blank under a nitrogen protective atmosphere;

[0037] 4) sintering: the sintering temperature is 1050℃, the holding time is 6h, and the sintering vacuum degree is 2×10 -3 Pa;

[0038] 5) tempering: the temperature is reduced to 900℃, the holding time is 3h, then the temperature is reduced to 580℃, and the holding time is 4h.

[0039] The preparation steps of example 3 are:

[0040] 1) batching: batching according to the required ingredients, including alloy M and alloy N, wherein the composition of alloy M is Pr5Nd 25 Al 0.25 Cu 0.1 Ga 0.2 Zr 0.1 Fe 68.42 B 0.93 , alloy N is Pr 30 Nd 55 Al2Cu5Ge8; the smelting temperature of alloy M is 1450-1500℃, the smelting temperature of alloy N is 1150-1250℃, the cooling speed of alloy M is 1200℃ / s, the cooling speed of alloy N is 1000℃ / s, alloy M and alloy N are mixed to form a mixture;

[0041] 2) powder preparation: the mixture is treated by hydrogen absorption and then dehydrogenation at 450℃, the mixture is powdered in a protective atmosphere, the protective gas contains 50ppm of oxygen and the balance is nitrogen; the average particle size of the powder is 2.65μm;

[0042] 3) pressing forming: the powder is oriented under a magnetic field with a magnetic field strength of 2.0T, and then pressed into a blank under a nitrogen protective atmosphere;

[0043] 4) sintering: sintering temperature 1040℃, holding time 6h, sintering vacuum 2x10 -3 Pa;

[0044] 5) tempering: temperature is reduced to 900℃, holding time 3h, then temperature is reduced to 580℃, holding time 4h.

[0045] Comparative Example 1 differs from Example 1 in that it does not contain Si element.

[0046] Comparative Example 2 differs from Example 2 in that it uses a single alloy, i.e. alloy M and alloy N are the same alloy, the melting temperature is 1450-1500℃, and the cooling rate is 1500℃ / s.

[0047] Comparative Example 3 differs from Example 3 in that it does not contain Ge element.

[0048] The obtained examples and comparative examples are subjected to performance detection:

[0049] Phase structure: the content of different phases is measured using area method on the scanning electron image of the magnet, and the phase structure is shown in the attached figure. Figure 1 As can be seen, the phase structure of the magnetic material of Example 2 includes 2:14:1 phase and grain boundary phase distributed at the grain boundary of the 2:14:1 phase, wherein the grain boundary phase includes RE-rich phase and R-T-Ga phase. The area content of the grain boundary phase in the phase structure is 18.7%, and the R-T-Ga phase accounts for 43% of the area content of the grain boundary phase.

[0050] The phase structure of the magnetic material of Example 2 is shown in the attached figure. Figure 2 As can be seen, the magnet is composed of 2:14:1 phase and grain boundary phase, and there is no dark gray R-T-Ga phase on the grain boundary, and the area ratio of the grain boundary phase is 17.6%.

[0051] Green density detection after compression molding: the molding density of the compression is calculated by mass divided by volume, wherein the volume is calculated by size measurement using vernier caliper.

[0052] Magnetic performance detection: the magnetic material obtained by the detection method according to GB13560-2017 is processed into a sample column with a diameter of Φ10mm and a length of 10mm, and the main test items are residual magnetization Br and intrinsic coercive force Hcj. The detection results are shown in Table 2.

[0053] Resistivity detection: the resistivity of the magnet is tested according to the four-probe method. The obtained magnetic material is processed into a sample with a size of 1x1x10mm 3 The resistivity of the sample is tested, and the detection results are shown in Table 2.

[0054] Table 1 Composition of the examples and comparative examples of the present application / wt%

[0055]

[0056] Table 2 Magnetic properties and resistivity of inventive examples, comparative examples

[0057]

Claims

1. A magnetic material, characterized by: The magnetic material has a mass percentage composition of RE: 29-32wt%, B: 0.8-1.0wt%, Ga: 0.01-0.6wt%, A: 0.1-0.5wt%, T: 0.01-2.0wt%, wherein T is selected from at least one of Al, Cu, Co, Zr, Ti, and the balance is Fe and inevitable impurities; A is selected from Si and Ge, and the mass ratio of Si to Ga is 1:(2-5); the phase organization of the magnetic material includes a 2:14:1 phase and a grain boundary phase distributed at the grain boundary of the 2:14:1 phase, wherein the grain boundary phase includes a RE-rich phase and an R-T-Ga phase.

2. The magnetic material of claim 1, wherein: The area content of the grain boundary phase in the phase organization is 3-20%, and the R-T-Ga phase accounts for 20-50% of the area content of the grain boundary phase.

3. A method of producing a magnetic material as claimed in claim 1 or 2, characterized in that: The method comprises the following preparation steps: 1) batching: batching according to the required ingredients, including alloy M and alloy N, wherein alloy M has a composition of RE, B, Ga, and Fe, and alloy N has a composition of RE, Ga, T, and A, wherein RE is selected from Pr and / or Nd; alloy M and alloy N are mixed to form a mixture; 2) powder preparation: after hydrogen absorption and then dehydrogenation treatment, the mixture is powdered in a protective atmosphere containing 20-100ppm of oxygen and the balance of nitrogen; the average particle size of the powder is 1.5-3μm; 3) compression molding: the powder is oriented under a magnetic field with a strength of 1.5-3.0T, and then compressed into a blank under a nitrogen protective atmosphere; 4) sintering: sintering temperature 1000-1100 °C, holding time 6-10 h, sintering vacuum 2-5 x 10 -3 Pa; 5) tempering: the temperature is reduced to 850-950℃, and the temperature is maintained for 1-3h, then the temperature is reduced to 500-600℃, and maintained for 2-6h.

4. The method of producing a magnetic material according to claim 3, wherein: In the step 1), alloy M and alloy N are in a quenched state, the melting temperature of alloy M is 1450-1500℃, and the melting temperature of alloy N is 1000-1400℃, and both are solidified at a cooling speed of ≥1000℃ / s.

5. The method of producing a magnetic material according to claim 3, wherein: In the step 2), the mixture is dehydrogenated at a temperature lower than 500℃.

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