A grain boundary diffusion source and preparation method, and a preparation method of a neodymium iron boron magnet

Abstract

The present invention discloses a grain boundary diffusion source and a preparation method thereof, and a preparation method of a neodymium iron boron magnet. The grain boundary diffusion source is expressed in atomic percentage (RE 1‑x‑y HRE x Y y ) 70 (MⅠ 1‑z MⅡ z ) 30 alloy powder; the RE is selected from one or more of La, Ce, Pr or Nd; the HRE is selected from one or more of Dy or Tb, and the MI and MI are selected from one or more of Fe, Co, Al, Mg, Cu, Zn, Si, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Hf, Ta or W; wherein 0≤x≤1, 0≤y≤0.3, 0≤z≤1, x(RE)+x(HRE)+x(Y)=70at.%, and x(MI)+x(MI)=30at.%. The present invention adopts a grain boundary diffusion process to infiltrate elements such as Dy / Tb and Y into the sintered magnet. Under the premise that the reduction in remanence is not large, due to the synergistic effect of Dy / Tb and Y, a magnet with high coercivity and low demagnetization factor can be prepared. At the same time, due to the low cost of the Y element, the production cost can be greatly reduced, and the high temperature performance and thermal stability of the magnet can be guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet preparation, and in particular relates to a grain boundary diffusion source and a preparation method thereof, and a preparation method of a neodymium iron boron magnet. Background Art

[0002] Based on RE2Fe 14 B intermetallic compounds (mainly Nd2Fe 14 B) permanent magnets have had a great technological impact. In the past 20 years, extensive research has been carried out to develop and improve their magnetic properties. Commercially, two types have been successfully developed: sintered Nd2Fe 14 B magnets and isotropic nanocrystalline Nd2Fe 14 B magnets, these magnets have excellent room temperature magnetic properties and are the main candidates for applications with operating temperatures of 120°C or below; however, these magnets have poor temperature stability above 120°C, which limits their application. Although many methods have been tried to improve the high temperature performance of Nd2Fe14B magnets, 14 The inherent properties of the B phase determine the Nd2Fe 14 B magnets have a larger demagnetization factor (larger remanence temperature coefficient α and coercive force temperature coefficient β).

[0003] For sintered magnets used at higher temperatures, heavy rare earth elements Dy or Tb are often added to improve high temperature performance and thermal stability by increasing coercivity. However, the addition of Dy / Tb Improved magnet In order to reduce the Dy / Tb content of Nd-Fe-B magnets, various methods have been successfully developed, including grain refinement and grain boundary diffusion processes as well as element substitution or addition, but with less success.

[0004] Recent studies have shown that using Dy / Tb and Y to replace Nd to improve the thermal stability of RE2Fe14B magnets is to directly introduce Dy / Tb and Y into the magnet. Although this method can improve the coercive force and the thermal stability of the magnet, it will also lead to a significant deterioration of the remanence (Br). This is because Y2Fe 14 B / Tb2Fe 14 B / Dy2 Fe 14 The Js of B (1.41T / 0.66T / 0.71T) is lower than that of Nd2Fe 14 B's Js (1.61T). Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a grain boundary diffusion source and a preparation method, as well as a preparation method for NdFeB magnets. The method has low processing cost and can prepare magnets with high coercive force and low demagnetization factor without significantly reducing the remanence.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a grain boundary diffusion source, the grain boundary diffusion source is (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 alloy powder; the RE is selected from one or more of La, Ce, Pr or Nd; the HRE is selected from one or more of Dy or Tb, and the MI and MI are selected from one or more of Fe, Co, Al, Mg, Cu, Zn, Si, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Hf, Ta or W; wherein 0≤x≤1, 0≤y≤0.3, 0≤z≤1, x(RE)+x(HRE)+x(Y)=70at.%, x(MI)+x(MI)=30at.%.

[0007] Furthermore, the (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 for:

[0008] (Pr 1-x-y HRE x Y y ) 70 Al 15 Cu 15 / (Pr 1-x-y HRE x Y y ) 70 Al 15 Ni 15 / (Pr 1-x-y HRE x Y y ) 70 Al 15 Ga 15 / (Pr 1-x-y HRE x Y y ) 70 Cu 15 Ga 15 / (HRE 1-y Y y ) 70 Al 15 Cu 15 / (HRE 1-y Y y )70 Al 15 Ni 15 / (HRE 1-y Y y ) 70 Al 15 Ga 15 / (HRE 1-y Y y ) 70 Cu 15 Ga 15 alloy powder.

[0009] A method for preparing a grain boundary diffusion source comprises the following steps:

[0010] ①According to (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The ingredients are prepared according to the mass percentage of each component;

[0011] ② Add all the raw materials into the quick-setting furnace, flush the furnace cavity with argon, and then evacuate to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through the tundish onto a rotating water-cooled copper roller to obtain (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Rapid solidification sheet; wherein, the melting temperature is 1000-1500℃, and the speed of the water-cooled copper roller is 1.2m / s;

[0012] ③ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Hydrogen cracking coarse powder; wherein, during the hydrogen cracking process, the hydrogen absorption temperature is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 400°C, and the dehydrogenation time is 2h;

[0013] ④ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box and then jet milled for 30-120 minutes at a sorting wheel speed of 3000, and finally a particle size of 4-6 μm was obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder.

[0014] A method for preparing a neodymium iron boron magnet comprises the following steps:

[0015] S1) preparing a sintered NdFeB blank for grain boundary diffusion treatment;

[0016] S2) processing the sintered NdFeB blank into a substrate treated with grain boundary diffusion and performing surface treatment;

[0017] S3) placing the adhesive into the liquid dispersant and stirring to dissolve the adhesive, wherein the weight ratio of the adhesive to the liquid dispersant is 1:9;

[0018] S4) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve and the nitrogen inlet valve of the glove box to allow nitrogen to evacuate the air in the glove box to reduce the oxygen content to less than 0.04%;

[0019] S5) the (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder is added to the colloid several times, stirring evenly each time until it is completely added, and then the stirring time is extended for 5 minutes to make (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The diffusion source powder is completely covered by the colloid to obtain the target slurry, (RE 1-x-y HRE x Y y )70 (MⅠ 1-z MⅡ z ) 30 The mass percentage of the diffusion source powder in the slurry is 1%-90%;

[0020] S6) Print a layer of (RE) on the surface of the diffusion magnet substrate using screen printing 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source film, (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The diffusion source film accounts for 0.1-2 wt.% of the substrate mass;

[0021] S7) will be plated with (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The magnet of the diffusion source film is dried to obtain the magnet to be diffused, the drying temperature is 100-120°C, and the drying time is 8-15 minutes;

[0022] S8) transferring the magnet to be diffused to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

[0023] Furthermore, the components of the sintered NdFeB blank are composed of the following by mass percentage: Pr-Nd: 30%, Al: 0.1%, Co: 0.25%, B: 0.96%, Cu: 0.1%, Ti: 0.2%, Zr: 0.1% and the balance Fe.

[0024] Furthermore, the surface treatment refers to removing the oxide layer, polishing to a mirror surface and cleaning.

[0025] Furthermore, the diffusion heat treatment is divided into primary heat treatment and secondary heat treatment. The primary heat treatment temperature is 700-950℃, and the heat preservation time is 8-20h; the secondary heat treatment temperature is 400-600℃, and the heat preservation time is 4-8h. The vacuum degree of the sintering furnace is controlled at 5*10 -3 Pa-5*10 -2 Pa.

[0026] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0027] The grain boundary diffusion source and preparation method, as well as the preparation method of the NdFeB magnet of the present invention, adopt a grain boundary diffusion process to infiltrate elements such as Dy / Tb and Y into the sintered magnet. Under the premise that the reduction of the remanence is not large, due to the synergistic effect of Dy / Tb and Y, a magnet with high coercive force and low demagnetization factor can be prepared. At the same time, due to the low cost of the Y element, the production cost can be greatly reduced, and the high-temperature performance and thermal stability of the magnet can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings:

[0029] Figure 1 B in Examples 1.1-1.7 of the present invention r Increment and H cj Values at temperatures of 20°, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, and 160°C;

[0030] Figure 2 B in Examples 2.1-2.7 of the present invention r Increment and H cj Values at temperatures of 20°, 40℃, 60℃, 80℃, 100℃, 120℃, 140℃, and 160℃. DETAILED DESCRIPTION

[0031] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0032] The present invention provides a grain boundary diffusion source and a preparation method, as well as a preparation method for a neodymium iron boron magnet, to solve the problem that in the prior art, heavy rare earth elements Dy / Tb are often added to sintered magnets used at higher temperatures to improve high-temperature performance and thermal stability by increasing coercivity. However, the addition of Dy / Tb increases the price of the magnet, resulting in high cost.

[0033] Numerous studies have shown that, unlike many other Nd2Fe 14 Compared with B (rare earth element) compounds, Y2Fe 14 B shows a weaker temperature dependence, which is beneficial to improve the temperature stability. The main reason is that it is based on Y2Fe 14 B is caused by the positive temperature coefficient of the anisotropy field (Ha) in a wide temperature range.

[0034] In the embodiment of the present application, a grain boundary diffusion source is provided, wherein the composition of the grain boundary diffusion source alloy powder is calculated as follows in atomic percentage: 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 , wherein RE is selected from one or more of La, Ce, Pr or Nd; HRE is selected from one or more of Dy or Tb, and the MI and MI are selected from one or more of Fe, Co, Al, Mg, Cu, Zn, Si, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Hf, Ta or W, wherein 0≤x≤1, 0≤y≤0.3, and 0≤z≤1; the combination of RE element, HRE element and Y element satisfies x(RE)+x(HRE)+x(Y)=70at.%; the combination of MI element and MI element satisfies x(MI)+x(MI)=30at.%.

[0035] The (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Alloy powder, more preferably (Pr 1-x-y HRE x Y y ) 70 Al 15 Cu 15 / (Pr 1-x-y HRE x Y y ) 70 Al 15 Ni 15 / (Pr 1-x-y HRE x Y y ) 70 Al 15 Ga 15 / (Pr 1-x-y HRE x Y y ) 70 Cu 15 Ga 15 / (HRE 1-y Y y ) 70 Al 15 Cu 15 / (HRE 1-y Y y ) 70Al 15 Ni 15 / (HRE 1-y Y y ) 70 Al 15 Ga 15 / (HRE 1-y Y y ) 70 Cu 15 Ga 15 alloy powder.

[0036] The Y element added to the grain boundary diffusion source is a high-abundance rare earth element, which has the advantages of low cost while maintaining a low demagnetization factor and good hard magnetic properties of the magnet, and can effectively utilize high-abundance rare earth metals.

[0037] In addition, the present invention also provides a method for preparing a grain boundary diffusion source, comprising the following steps:

[0038] ①According to (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The mass percentage of each component in the mixture is used for batching, and before batching, the oxide layer on the surface of the HRE and Y needs to be removed by a shot blasting machine;

[0039] ② Add all the raw materials into the quick-setting furnace, flush the furnace cavity with argon, and then evacuate to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through the tundish onto a rotating water-cooled copper roller to obtain (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Rapid solidification sheet; wherein, the melting temperature is 700-1000℃, and the speed of the water-cooled copper roller is 1.2m / s;

[0040] ③ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (RE 1-x-y HRE x Y y )70 (MⅠ 1-z MⅡ z ) 30 Hydrogen cracking coarse powder; wherein, during the hydrogen cracking process, the hydrogen absorption temperature is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 400°C, and the dehydrogenation time is 2h;

[0041] ④ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box and then jet milled for 30-120 minutes at a sorting wheel speed of 3000, and finally a particle size of 4-6 μm was obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder.

[0042] Diffusion source powder is prepared by the above preparation method, which is convenient for the subsequent preparation of neodymium boron ferromagnets.

[0043] In addition, the present invention also discloses a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0044] S1) preparing a sintered NdFeB blank for grain boundary diffusion treatment;

[0045] The components in the sintered NdFeB blank are composed of: Pr-Nd: 30%, Al: 0.1%, Co: 0.25%, B: 0.96%, Cu: 0.1%, Ti: 0.2%, Zr: 0.1% and the balance Fe, and then the sintered NdFeB blank is produced according to the existing rare earth magnet smelting, belt throwing, hydrogen crushing, air flow grinding, orientation pressing, sintering and heat treatment processes.

[0046] S2) processing the sintered NdFeB blank into a substrate treated with grain boundary diffusion, wherein the orientation dimension of the substrate is similar to that of the finished product, within a range of 1 mm to 10 mm, and the substrate is surface treated, wherein the surface treatment includes removing the oxide layer, polishing to a mirror surface, cleaning, etc.;

[0047] S3) placing the adhesive into the liquid dispersant and stirring to dissolve the adhesive, wherein the weight ratio of the adhesive to the liquid dispersant is 1:9;

[0048] S4) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve and the nitrogen inlet valve of the glove box to allow nitrogen to evacuate the air in the glove box to reduce the oxygen content to less than 0.01%;

[0049] S5) the particle size of 4-6um (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder is added to the colloid several times, stirring evenly each time until it is completely added, and then the stirring time is extended for 5 minutes to make (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The diffusion source powder is completely covered by the colloid to obtain the target slurry, (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The mass percentage of the diffusion source powder in the slurry is 1%-90%;

[0050] S6) Print a layer of (RE) on the surface of the diffusion magnet substrate using screen printing 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source film, (HRE 1-x Y x ) 70 M 30 The diffusion source film accounts for 0.1-2 wt.% of the substrate mass;

[0051] S7) will be plated with (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The magnet of the diffusion source film is dried to obtain the magnet to be diffused, the drying temperature is 100-120°C, and the drying time is 8-15 minutes;

[0052] S8) transferring the magnet to be diffused to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

[0053] The diffusion heat treatment is divided into primary heat treatment and secondary heat treatment. The primary heat treatment temperature is 700-950°C and the insulation time is 8-20h; the secondary heat treatment temperature is 400-600°C and the insulation time is 4-8h. During the diffusion heat treatment, the vacuum degree of the sintering furnace is controlled at 5*10-3Pa-5*10-2Pa.

[0054] The following are several examples of methods for preparing NdFeB magnets for illustration:

[0055] Example 1

[0056] A method for preparing a neodymium iron boron magnet comprises the following steps:

[0057] S1) Using Dy, Y, Cu, Al with a purity of 99.9% by mass as raw materials, according to the atomic percentage (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) for batching, and before batching, the oxide layer of the Dy and Y surfaces needs to be removed by a shot blasting machine;

[0058] S2) All raw materials are added to the rapid solidification furnace, and the furnace cavity is flushed with argon gas, and then vacuumed to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through the tundish onto a rotating water-cooled copper roller to obtain (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3), where the melting temperature is 830°C and the speed of the water-cooled copper roller is 1.2 m / s;

[0059] S3) the obtained (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)

[0060] The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (Dy 1-x Y x ) 70 Al 15 Cu 15(x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) hydrogen-crushed coarse powder, the hydrogen absorption temperature during ZAI hydrogen cracking is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 400°C, and the dehydrogenation time is 2h;

[0061] S4) the obtained (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3))

[0062] The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box and then jet milled for 30 minutes at a speed of 3000 for the separation wheel. Finally, the particle size of 5.6 μm (Dy 1-x Y x ) 70 Al 15 Cu 15 Diffusion source powders of (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3);

[0063] S5) preparing a sintered NdFeB blank for grain boundary diffusion treatment;

[0064] S6) processing the processed sintered magnet into a 10mm*10mm*4mm square magnet, with the 4mm direction being the magnetic field orientation direction. After surface cleaning, the processed magnet was subjected to magnetic property testing using a Mianyang Bipolar 264Y permanent magnet property automatic measuring instrument at a measuring temperature of 20°C. The test results were Br: 14.42kGs, Hcj: 14.58kOe, (BH)max: 50.31MGOe, and SQ: 97.63%;

[0065] S7) placing an adhesive into a liquid dispersant and stirring to dissolve the adhesive, wherein the weight ratio of the adhesive to the liquid dispersant is 1:9;

[0066] S8) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve and the nitrogen inlet valve of the glove box to allow nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%;

[0067] S9) the particle size of 5.6um (Dy 1-x Y x ) 70 Al 15 Cu 15(x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) diffusion source powder was added to the colloid several times, stirring evenly each time until it was completely added, and then the stirring time was extended for 5 minutes to make the metal powder completely covered by the colloid to obtain the target slurry, (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) the mass percentage of the diffusion source powder in the slurry is 75%;

[0068] S10) a layer of (Dy) is printed on the surface of the diffusion magnet substrate by screen printing. 1-x Y x ) 70 Al 15 Cu 15 (x=0、0.05、0.1、0.15、0.2、0.25、0.3) diffusion source film, (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) the diffusion source film accounts for 1.0 wt.% of the substrate mass;

[0069] S11) will be plated with (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)

[0070] The magnet of the diffusion source film is dried to obtain the magnet to be diffused;

[0071] S12) transferring the magnet to be diffused to a sintering furnace for diffusion heat treatment to obtain a diffused magnet (Examples 1.1-1.7);

[0072] 13) The diffused magnets were tested for magnetic properties using a 264Y permanent magnet automatic measuring instrument from Mianyang Bipolar. The measuring temperatures were 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, and 160°C.

[0073] The evaluation results of the magnetic properties of Examples 1.1-1.7 at 20°C are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] As shown in Table 1 above, by analyzing the magnetic properties of Examples 1.1-1.7, it can be seen that (Dy 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) After the diffusion source diffuses into the base magnet through the grain boundaries, the coercive force is greatly improved.

[0078] In addition, the remanence of the diffused magnets is lower than that of the diffused matrix. The reason for the decrease in remanence is that Y2Fe 14 B and Dy2Fe 14 The Js value of B is lower than that of Nd2Fe 14 The Js value of B, during the diffusion heat treatment process, Dy and Y elements will replace Nd2Fe 14 The Nd element in the B grain forms (Nd-Dy-Y)2Fe on the grain surface. 14 The magnetic dilution effect produced by the substitution of Dy and Y elements for Nd in the B shell reduces the remanence of the magnet, but the reduction is not large. This is due to the use of the grain boundary diffusion process.

[0079] For diffusion magnets, (Dy 0.85 Y 0.15 ) 70 Al 15 Cu 15 The best magnetic properties that can be achieved by diffusion of the diffusion source are: Br = 14.16 kGs, Hcj = 23.42 kOe and (BH)max = 48.58 MGOe.

[0080] With the increase of Y content, the coercive force and remanence of the diffused magnet show a trend of increasing first and then decreasing; when the Y content is x=0-0.15, the remanence of the diffused magnet increases with the increase of Y content. The reason is that Y2Fe 14 The Js value of B is higher than that of Dy2Fe 14 B's Js value.

[0081] When Y content x>0.15, Y tends to enter Nd2Fe 14 B grains, which intensifies the magnetic dilution effect and reduces the remanence of the magnet. According to the research of Ningbo Institute, Dy and Y diffuse into the magnet at the same time, and Y tends to enter Nd2Fe 14 The B grains form a synergistic effect with the Dy element, making (Nd-Dy)2Fe 14The shell of B will not be too thick, which improves the utilization rate of the Dy element; therefore, in the present invention, when the Y content is x=0-0.15, the coercive force of the magnet increases with the increase of the Y content due to the synergistic effect of Dy and Y.

[0082] The demagnetization factors of the diffused magnets of Examples 1.1-1.7 are all smaller than those of the diffused matrix, indicating that the temperature stability of the diffused magnets has been improved. The improvement in temperature stability comes from the Dy2Fe 14 B high anisotropy field Ha and Y2Fe 14 The temperature coefficient of the anisotropy field (Ha) of B is positive over a wide temperature range.

[0083] In addition, from Table 1 and Figure 1 It can be seen that using (Dy 0.85 Y 0.15 ) 70 Al 15 Cu 15 Diffusion of the diffusion source can achieve the best demagnetization factor.

[0084] Example 2

[0085] A method for preparing a neodymium iron boron magnet comprises the following steps:

[0086] S1) Using Tb, Y, Cu, Al with a purity of 99.9% by mass as raw materials, according to the atomic percentage (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) for batching, and before batching, the oxide layer of the Tb and Y surface needs to be removed by a shot blasting machine;

[0087] S2) All raw materials are added to the rapid solidification furnace, and the furnace cavity is flushed with argon gas, and then vacuumed to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through the tundish onto a rotating water-cooled copper roller to obtain (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) rapid solidification sheet, melting temperature is 830℃, water-cooled copper roller speed is 1.2m / s;

[0088] S3) the obtained (Tb 1-x Y x ) 70 Al 15Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)

[0089] The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) hydrogen-crushed coarse powder, the hydrogen absorption temperature during hydrogen cracking is 300℃, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 400℃, and the dehydrogenation time is 2h;

[0090] S4) will get (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)

[0091] The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box and then jet milled for 30 minutes at a speed of 3000 for the separation wheel. Finally, the particle size of 5.6 μm (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) diffusion source powder;

[0092] S5) preparing a sintered NdFeB blank for grain boundary diffusion treatment;

[0093] S6) processing the processed sintered magnet into a 10mm*10mm*4mm square magnet, with the 4mm direction being the magnetic field orientation direction. After surface cleaning, the processed magnet was tested for magnetic properties using a Mianyang Bipolar 264Y permanent magnet property automatic measuring instrument at a measurement temperature of 20°C. The measurement results were Br: 14.42kGs, Hcj: 14.58kOe, (BH)max: 50.31MGOe, and SQ: 97.63%;

[0094] S7) placing the adhesive into the liquid dispersant and stirring to dissolve the adhesive, wherein the weight ratio of the adhesive to the liquid dispersant is 1:9;

[0095] S8) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve and the nitrogen inlet valve of the glove box to allow nitrogen to evacuate the air in the glove box to reduce the oxygen content to less than 0.01%;

[0096] S9) the particle size of 5.6um (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) diffusion source powder was added to the colloid in several times, and stirred evenly each time until it was completely added. The stirring time was then extended for 5 minutes to make the metal powder completely covered by the colloid to obtain the target slurry, (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) the mass percentage of the diffusion source powder in the slurry is 75%;

[0097] S10) a layer of (Tb) is printed on the surface of the diffusion magnet substrate by screen printing. 1-x Y x ) 70 Al 15 Cu 15 (x=0、0.05、0.1、0.15、0.2、0.25、0.3) diffusion source film, the (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) the diffusion source film accounts for 1.0 wt.% of the substrate mass;

[0098] S11) will be plated with (Tb 1-x Y x ) 70 Al 15 Cu 15 (x=0、0.05、0.1、0.15、0.2、0.25、0.3)

[0099] The magnet of the diffused source film is dried to obtain the magnet to be diffused;

[0100] S12) transferring the magnet to be diffused to a sintering furnace for diffusion heat treatment to obtain a diffused magnet;

[0101] S13) The diffused magnets were tested for magnetic properties using a 264Y permanent magnet property automatic measuring instrument from Mianyang Bipolar, with the measuring temperatures being 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, and 160°C.

[0102] The evaluation results of the magnetic properties at 20°C of Examples 2.1-2.7 are shown in Table 2.

[0103] Table 2

[0104]

[0105] As shown in Table 2, the magnetic properties of Examples 2.1-2.7 were analyzed and found to be 1-x Y x ) 70 Al 15 Cu 15 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) After the diffusion source performs grain boundary diffusion on the base magnet, the coercive force is greatly improved; the remanence of the diffused magnets is lower than that of the diffused base. The reason for the reduction in remanence is the same as that in Example 1, but since the grain boundary diffusion process is adopted, the reduction is not large.

[0106] For diffusion magnets, (Tb 0.85 Y 0.15 )0Al 15 Cu 15 The best magnetic properties that can be achieved by diffusion of the diffusion source are: Br = 14.11 kGs, Hcj = 26.18 kOe and (BH)max = 49.35 MGOe.

[0107] With the increase of Y content, the coercivity and remanence of the diffused magnet show a trend of increasing first and then decreasing. When the Y content is x=0-0.15, the remanence of the diffused magnet increases with the increase of Y content. The reason is that Y2Fe 14 The Js value of B is higher than that of Tb2Fe 14 Js value of B. When Y content x>0.15, Y tends to enter Nd2Fe 14 B in the grains, which intensifies the magnetic dilution effect and reduces the remanence of the magnet. According to the research of Ningbo Institute, Tb and Y diffuse into the magnet at the same time, and Y tends to enter Nd2Fe 14 The B grains form a synergistic effect with the Dy element, making (Nd-Tb)2Fe 14 The B shell will not be too thick, thus improving the utilization rate of the Tb element. Therefore, in the present invention, when the Y content is x=0-0.10, the coercive force of the magnet increases with the increase of the Y content due to the synergistic effect of Tb and Y.

[0108] The demagnetization factors of the diffused magnets of Examples 2.1-2.7 are all smaller than that of the diffused matrix, indicating that the temperature stability of the diffused magnets has been improved. The improvement in temperature stability comes from Tb2Fe 14 B high anisotropy field Ha and Y2Fe 14The temperature coefficient of the anisotropy field (Ha) of B is positive over a wide temperature range.

[0109] In addition, from Table 2 and Figure 2 It can be seen that using (Dy 0.9 Y 0.10 ) 70 Al 15 Cu 15 Diffusion of the diffusion source can achieve the best demagnetization factor.

[0110] In summary, the grain boundary diffusion source and preparation method, as well as the preparation method of the NdFeB magnet of the present invention, adopt a grain boundary diffusion process to infiltrate elements such as Dy / Tb and Y into the sintered magnet. Under the premise that the reduction in remanence is not large, due to the synergistic effect of Dy / Tb and Y, a magnet with high coercive force and low demagnetization factor can be prepared. Since the cost of the Y element is low, the production cost can be greatly reduced, and the high temperature performance and thermal stability of the magnet can also be guaranteed.

[0111] In addition, the rare earth element Y used in the present invention is a high-abundance rare earth element, which has the advantages of low cost while maintaining a low demagnetization factor and good hard magnetic properties of the magnet. It can effectively utilize high-abundance rare earth metals and achieve a comprehensive and balanced utilization of rare earth resources, which is of great significance to the sustainable development of the rare earth permanent magnet industry.

[0112] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A grain boundary diffusion source, characterized in that: The grain boundary diffusion source is expressed in atomic percentages as (RE 1-x- y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 alloy powder; the RE is selected from one or more of La, Ce, Pr or Nd; the HRE is selected from one or more of Dy or Tb, and the MI and MII are selected from one or more of Fe, Co, Al, Mg, Cu, Zn, Si, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Hf, Ta or W; wherein 0<x<1, 0<y≤0.3, 0≤z≤1, x(RE)+x(HRE)+x(Y)=70 at.%, x(MI)+x(MII)=30 at.%.

2. The grain boundary diffusion source according to claim 1, wherein: The (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 for: (Pr 1-x-y English: HRE x Y y , 70 Al 15 Cu 15 / (Pr 1-x-y English: HRE x Y y , 70 Al 15 Ni 15 , (Pr 1-x-y English: HRE x Y y , 70 Al 15 Ga 15 / (Pr 1-x-y English: HRE x Y y , 70 Cu 15 Ga 15 , (HRE 1-y Y y ) 70 Al 15 Dog 15 / (HRE 1-y Y y ) 70 Al 15 What 15 / (HRE 1-y Y y ) 70 Al 15 Ga 15 / (HRE 1-y Y y ) 70 Cu 15 Ga 15 alloy powder.

3. A method for preparing a grain boundary diffusion source according to any one of claims 1 to 2, characterized in that: The steps include: ①According to (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The ingredients are prepared according to the mass percentage of each component; ② Add all the raw materials into the quick-setting furnace, flush the furnace cavity with argon, and then evacuate to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through the tundish onto a rotating water-cooled copper roller to obtain (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Rapid solidification sheet; wherein, the melting temperature is 1000-1500℃, and the speed of the water-cooled copper roller is 1.2m / s; ③ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Hydrogen cracking coarse powder; wherein, during the hydrogen cracking process, the hydrogen absorption temperature is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 400°C, and the dehydrogenation time is 2h; ④ The obtained (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box and then jet milled for 30-120 minutes at a speed of 3000 rpm to obtain a particle size of 4-6 μm (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder.

4. A method for preparing a neodymium iron boron magnet, characterized in that: The following steps are involved: S1) preparing a sintered NdFeB blank for grain boundary diffusion treatment; S2) processing the sintered NdFeB blank into a substrate treated with grain boundary diffusion and performing surface treatment; S3) placing the adhesive into the liquid dispersant and stirring to dissolve the adhesive, wherein the weight ratio of the adhesive to the liquid dispersant is 1:9; S4) The dissolved colloid is placed in a glove box, and the nitrogen outlet valve and nitrogen inlet valve of the glove box are opened to allow nitrogen to exhaust the air in the glove box and reduce the oxygen content to less than 0.04%. S5) the (RE) having a particle size of 4-6 μm obtained by the preparation method as claimed in claim 3 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source powder is added to the colloid several times, stirring evenly each time until it is completely added, and then the stirring time is extended for 5 minutes to make (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The diffusion source powder is completely covered by the colloid to obtain the target slurry, (RE 1-x- y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The mass percentage of the diffusion source powder in the slurry is 1%-90%; S6) Print a layer of (RE) on the surface of the diffusion magnet substrate using screen printing 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 Diffusion source film, (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The diffusion source film accounts for 0.1-2 wt.% of the substrate mass; S7)will be plated with (RE 1-x-y HRE x Y y ) 70 (MⅠ 1-z MⅡ z ) 30 The magnet of the diffusion source film is dried to obtain the magnet to be diffused, the drying temperature is 100-120°C, and the drying time is 8-15 minutes; S8) transferring the magnet to be diffused to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

5. The method for preparing a NdFeB magnet according to claim 4, wherein: The components of the sintered NdFeB blank are composed by mass percentage: Pr-Nd: 30%, Al: 0.1%, Co: 0.25%, B: 0.96%, Cu: 0.1%, Ti: 0.2%, Zr: 0.1% and the balance Fe.

6. The method for preparing a NdFeB magnet according to claim 4, wherein: The surface treatment includes removing the oxidation layer, polishing to a mirror surface and cleaning.

7. The method for preparing a NdFeB magnet according to claim 4, wherein: The diffusion heat treatment is divided into primary heat treatment and secondary heat treatment. The primary heat treatment temperature is 700-950℃, and the heat preservation time is 8-20h; the secondary heat treatment temperature is 400-600℃, and the heat preservation time is 4-8h. The vacuum degree of the sintering furnace is controlled at 5x10 -3 Pa-5x10 -2 Pa.

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