阅读说明：本技术 混合稀土烧结钕铁硼永磁体及其制备方法 (Mixed rare earth sintered neodymium-iron-boron permanent magnet and preparation method thereof ) 是由 任少卿 吕科 孟恒 赵明静 李泉 高岩 付建龙 刘国征 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种混合稀土烧结钕铁硼永磁体及其制备方法,按照(MM-xRE-(1-x))-aFe-(100-a-b-)-cB-bM-c成分配料,采用速凝甩带技术得到厚度为0.2～0.5mm的速凝甩带片,然后经过氢破碎和气流磨制成平均粒度为2～5μm的磁粉；将磁粉在氮气保护下在混料罐中混合,混合均匀后在磁场下取向成型,经冷等静压制成生坯；将生坯放在真空烧结炉中进行烧结,烧结温度为950～1100℃,保温得到烧结态磁体；对烧结态磁体进行回火处理,回火温度为420～650℃,得到混合稀土烧结钕铁硼永磁体。本发明通过调整稀土元素与硼元素的比例,制备工艺采用一级回火处理,从而改善了永磁体磁性能。(The invention discloses a mixed rare earth sintered neodymium-iron-boron permanent magnet and a preparation method thereof, according to (MM) x RE 1‑x ) a Fe 100‑a‑b‑ c B b M c Preparing ingredients, namely obtaining a rapid hardening melt-spun sheet with the thickness of 0.2-0.5 mm by adopting a rapid hardening melt-spun technology, and then preparing magnetic powder with the average particle size of 2-5 mu m by hydrogen crushing and airflow milling; mixing the magnetic powder in a mixing tank under the protection of nitrogen, uniformly mixing, then carrying out orientation forming in a magnetic field, and preparing a green body through cold isostatic pressing; sintering the green body in a vacuum sintering furnace at the sintering temperature of 950-1100 ℃ to obtain a sintered magnet; and tempering the sintered magnet at the tempering temperature of 420-650 ℃ to obtain the mixed rare earth sintered neodymium-iron-boron permanent magnet. The invention adjusts the ratio of rare earth element to boron elementFor example, the preparation process adopts primary tempering treatment, thereby improving the magnetic property of the permanent magnet.)

1. The mixed rare earth sintered neodymium iron boron permanent magnet is characterized in that the general formula of the mass percent is as follows: (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cMM is mixed rare earth alloy, and the mass percentage of MM is; ce>48 percent of La 20-35 percent, Pr 4-7 percent, Nd 10-20 percent, Sm less than or equal to 0.3 percent, Fe less than or equal to 1 percent, Mg less than or equal to 0.8 percent, Si less than or equal to 0.2 percent, Ca less than or equal to 0.03 percent, S less than or equal to 0.02 percent and P less than or equal to 0.01 percent; RE is one or more of Pr, Nd, Sm, Eu, Gd, Ho, Dy and Tb, B is boron, M is one or more of Nb, V, Ti, Co, Cr, Mo, Mn, Ni, Ga, Zr, Ta, Ag, Au, Al, Pb, Cu and Si, wherein a is more than or equal to 29 and less than or equal to 35, B is more than or equal to 0.85 and less than or equal to 1, c is more than or equal to 0.5 and less than or equal to 5, and x is more than or equal to 10 and less than or equal to 40.

2. The mixed rare earth sintered NdFeB permanent magnet as claimed in claim 1 wherein a is 31. ltoreq. a.ltoreq.33, b is 0.9. ltoreq. b.ltoreq.0.95, c is 1.2. ltoreq. c.ltoreq.2.5, and x is 20. ltoreq. x.ltoreq.30.

3. The sintered ndfeb permanent magnet of mixed rare earth as claimed in claim 1, wherein the total amount of rare earth a is 32 and the boron content b is 0.92.

4. The sintered Nd-Fe-B permanent magnet according to claim 1, wherein the total amount of rare earth a is 33 and the B content is 0.9.

5. The method for preparing mixed rare earth sintered NdFeB permanent magnet as claimed in any one of claims 1 to 4, comprising:

according to (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cPreparing ingredients, namely obtaining a quick-setting melt-spun sheet with the thickness of 0.2-0.5 mm by adopting a quick-setting melt-spun technology, and preparing magnetic powder with the average particle size of 2-5 mu m from the quick-setting melt-spun sheet through hydrogen crushing and airflow milling;

mixing the magnetic powder under the protection of nitrogen, mixing for 1-3 h in a mixing tank, performing orientation molding in a 1.5-2T magnetic field after uniform mixing, and preparing a green body through cold isostatic pressing;

sintering the green body in a vacuum sintering furnace at the sintering temperature of 950-1100 ℃ for 1-10 h to obtain a sintered magnet;

and tempering the sintered magnet at the tempering temperature of 420-650 ℃ to obtain the mixed rare earth sintered neodymium-iron-boron permanent magnet.

6. The method for preparing the mixed rare earth sintered neodymium-iron-boron permanent magnet according to claim 5, wherein the tempering heat treatment is performed at 470-530 ℃ for 2-5 hours.

7. The method for preparing the mixed rare earth sintered neodymium-iron-boron permanent magnet according to claim 5, wherein a is not less than 31 and not more than 33 and b is not less than 0.9 and not more than 0.95 by controlling the total amount of the rare earth and the content of boron.

8. The method of claim 5, wherein the mixed rare earth sintered NdFeB permanent magnet is prepared as powder with average powder size less than 3.5 μm, the powder is oriented under 2T magnetic field under nitrogen protection, and is made into green compact by cold isostatic pressing at 200 MPa.

9. The method for preparing mixed rare earth sintered neodymium-iron-boron permanent magnet according to claim 5, wherein the green body is placed into a vacuum sintering furnace, sintered and insulated for 5 hours at 1060 ℃, and then tempered for 3 hours at 500 ℃.

Technical Field

The invention relates to the field of rare earth permanent magnet material preparation, in particular to a mixed rare earth sintered neodymium iron boron permanent magnet and a preparation method thereof.

Background

The neodymium iron boron permanent magnet is a third-generation permanent magnet material, has excellent comprehensive magnetic performance, is widely applied to the fields of the electronic industry, aerospace, medical appliances, wind power generation, electric automobiles, robots and the like, and is a permanent magnet material which is most widely applied in the current market. The rare earth permanent magnet manufacturing industry mainly uses praseodymium-neodymium alloy as raw materials to manufacture neodymium-iron-boron permanent magnets, and the light rare earth mainly produced in China contains a large amount of La and Ce rare earth elements, so that the rare earth elements are difficult to be effectively utilized. The proportions of La, Ce, Pr and Nd in Mischmetal (MM) maintain the proportions in the ore. Because the process flow of rare earth element separation is reduced, the mixed rare earth alloy is more environment-friendly and has obvious price advantage. The rare earth permanent magnet is manufactured by using the mixed rare earth as a raw material, so that the cost of the permanent magnet can be obviously reduced, and the balanced utilization of rare earth resources is facilitated.

Commercial magnets typically require a coercivity above 12 KOe. Due to the high content of La and Ce in the misch metal, if a pure MMFeB alloy is manufactured, the magnetic property is seriously reduced, and the application requirement is difficult to meet. Recently, the work of partially replacing PrNd by MM to produce the low-cost neodymium iron boron magnet has achieved results, and the heterogeneous neodymium iron boron alloy can maintain high magnetic performance, so that the hope is brought to the production of the low-cost magnet.

The traditional sintering permanent magnet process route adopts secondary tempering, but for (MM, Nd) -Fe-B magnets, the damage of chemical element homogenization on magnetic performance is difficult to avoid, and the preparation cost is high.

Chinese patent publication No. CN 107146674 a discloses a cerium-rich rare earth permanent magnet free of heat treatment and a production method thereof, in which the magnet includes a plurality of main phases. The process is free from a subsequent heat treatment process, and the magnet performance is realized by a plurality of main phases contained in the magnet.

Disclosure of Invention

The invention aims to provide a mixed rare earth sintered neodymium iron boron permanent magnet and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the mixed rare earth sintered neodymium iron boron permanent magnet has the general formula of mass percent: (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cMM is mixed rare earth alloy, and the mass percentage of MM is; ce>48 percent of La 20-35 percent, Pr 4-7 percent, Nd 10-20 percent, Sm less than or equal to 0.3 percent, Fe less than or equal to 1 percent, Mg less than or equal to 0.8 percent, Si less than or equal to 0.2 percent, Ca less than or equal to 0.03 percent, S less than or equal to 0.02 percent and P less than or equal to 0.01 percent; RE is one or more of Pr, Nd, Sm, Eu, Gd, Ho, Dy and Tb, B is boron, M is one or more of Nb, V, Ti, Co, Cr, Mo, Mn, Ni, Ga, Zr, Ta, Ag, Au, Al, Pb, Cu and Si, wherein a is more than or equal to 29 and less than or equal to 35, B is more than or equal to 0.85 and less than or equal to 1, c is more than or equal to 0.5 and less than or equal to 5, and x is more than or equal to 10 and less than or equal to 40.

Furthermore, a is more than or equal to 31 and less than or equal to 33, b is more than or equal to 0.9 and less than or equal to 0.95, c is more than or equal to 1.2 and less than or equal to 2.5, and x is more than or equal to 20 and less than or equal to 30.

Further, the total amount of rare earth a in the magnet was 32, and the boron content b was 0.92.

Further, the total amount of rare earth a in the magnet was 33, and the boron content b was 0.9.

The preparation method of the mixed rare earth sintered neodymium iron boron permanent magnet comprises the following steps:

according to (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cPreparing ingredients, namely obtaining a quick-setting melt-spun sheet with the thickness of 0.2-0.5 mm by adopting a quick-setting melt-spun technology, and preparing magnetic powder with the average particle size of 2-5 mu m from the quick-setting melt-spun sheet through hydrogen crushing and airflow milling;

mixing the magnetic powder under the protection of nitrogen, mixing for 1-3 h in a mixing tank, performing orientation molding in a 1.5-2T magnetic field after uniform mixing, and preparing a green body through cold isostatic pressing;

sintering the green body in a vacuum sintering furnace at the sintering temperature of 950-1100 ℃ for 1-10 h to obtain a sintered magnet;

and tempering the sintered magnet at the tempering temperature of 420-650 ℃ to obtain the mixed rare earth sintered neodymium-iron-boron permanent magnet.

Preferably, the tempering heat treatment is carried out at 470-530 ℃ for 2-5 h.

Preferably, the total amount of the rare earth and the content of the boron are controlled so that a is more than or equal to 31 and less than or equal to 33 and b is more than or equal to 0.9 and less than or equal to 0.95.

Preferably, the powder with the average powder particle size of less than 3.5 μm is prepared, the magnetic powder is oriented and molded under the protection of nitrogen under the 2T magnetic field, and a green body is prepared by cold isostatic pressing at 200 MPa.

Preferably, the green body is placed into a vacuum sintering furnace, sintered and insulated for 5 hours at 1060 ℃, and then tempered for 3 hours at 500 ℃.

The invention has the technical effects that:

the invention adopts the first-grade tempering treatment to manufacture the mixed rare earth sintered neodymium-iron-boron permanent magnet ((MM, Nd) -Fe-B magnet) with the coercive force larger than 12KOe by adjusting the proportion of the rare earth element and the boron element. The raw material cost and the manufacturing energy consumption of the magnet are reduced while the higher magnetic performance is kept.

(1) The magnet provided by the invention utilizes the mixed rare earth.

The proportions of La, Ce, Pr and Nd in the mixed rare earth maintain the proportions of elements in the Baiyunebo ore in the main producing area of the light rare earth in China. Because the process flow of rare earth element separation is reduced, the mixed rare earth alloy is more environment-friendly and has obvious price advantage. The invention uses MM part to replace Nd to prepare and produce rare earth permanent magnet, and realizes cost control.

(2) The invention ensures the content of the rare earth-rich phase in the permanent magnet liquid phase sintering process by controlling the total amount of the rare earth and the content of boron, thereby improving the magnetic performance.

(3) The invention adopts a primary tempering process route, and greatly reduces the production energy consumption compared with a secondary tempering process route manufactured by the traditional permanent magnet.

The invention adopts the primary tempering, is beneficial to avoiding the damage of the homogenization of chemical elements to the magnetic performance, and has shorter manufacturing process flow of the (MM, Nd) -Fe-B magnet, thereby not only reducing the cost of raw materials, but also reducing the energy consumption in the manufacturing process, and having great significance for the production of low-cost magnets.

Detailed Description

The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce it.

The preparation method of the mixed rare earth sintered neodymium iron boron permanent magnet comprises the following steps:

step 1: according to (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cPreparing ingredients, namely obtaining a rapid hardening melt-spun sheet with the thickness of 0.2-0.5 mm by adopting a rapid hardening melt-spun technology, and then preparing magnetic powder with the average particle size of 2-5 mu m by hydrogen crushing and airflow milling;

step 2: mixing the magnetic powder under the protection of nitrogen, mixing for 1-3 h in a mixing tank, performing orientation molding in a 1.5-2T magnetic field after uniform mixing, and preparing a green body through cold isostatic pressing;

the cold isostatic pressure was 200 MPa.

And step 3: sintering the green body in a vacuum sintering furnace at the sintering temperature of 950-1100 ℃ for 1-10 h to obtain a sintered magnet;

and 4, step 4: and tempering the sintered magnet at the tempering temperature of 420-650 ℃ to obtain the mixed rare earth sintered neodymium-iron-boron permanent magnet.

In the preferred embodiment, a primary tempering process route is adopted, the preferred tempering temperature is 470-530 ℃, and one temperature is selected from 470-530 ℃ to carry out tempering heat treatment for 2-5 hours. The mixed rare earth sintered neodymium iron boron permanent magnet comprises four rare earth metals of La, Ce, Pr and Nd.

The mixed rare earth sintered neodymium-iron-boron permanent magnet obtained by the invention has only one main phase, and good magnetic performance can be obtained only through primary tempering due to the adjustment of the total amount of rare earth and the content of boron. The higher total amount of rare earth and the lower boron content ensure that more neodymium-rich phases exist in the magnet, the neodymium-rich phases mainly comprise rare earth, iron and a certain amount of oxygen and other small amount of metals, and the neodymium-rich phases with the components are the reasons that the primary tempering can effectively improve the microstructure of the magnet. The primary tempering process is based on the chemical element proportion of the magnet, namely the two invention points of the invention are mutually dependent.

The mixed rare earth sintered neodymium-iron-boron permanent magnet belongs to a (MM, Nd) -Fe-B magnet, and has a general formula in percentage by mass: (MM)_xRE_1-x)_aFe_100-a-b-cB_bM_cMM is mixed rare earth alloy, and the mass percent of MM is as follows: ce>48 percent of La 20-35 percent, Pr 4-7 percent, Nd 10-20 percent, Sm less than or equal to 0.3 percent, Fe less than or equal to 1 percent, Mg less than or equal to 0.8 percent, Si less than or equal to 0.2 percent, Ca less than or equal to 0.03 percent, S less than or equal to 0.02 percent and P less than or equal to 0.01 percent; RE is one or more of Pr, Nd, Sm, Eu, Gd, Ho, Dy and Tb, B is boron, M is one or more of Nb, V, Ti, Co, Cr, Mo, Mn, Ni, Ga, Zr, Ta, Ag, Au, Al, Pb, Cu and Si, wherein a is more than or equal to 29 and less than or equal to 35, B is more than or equal to 0.85 and less than or equal to 1, c is more than or equal to 0.5 and less than or equal to 5, and x is more than or equal to 10 and less than or equal to 40.

In the preferred embodiment, a is more than or equal to 31 and less than or equal to 33, b is more than or equal to 0.9 and less than or equal to 0.95, c is more than or equal to 1.2 and less than or equal to 2.5, and x is more than or equal to 20 and less than or equal to 30. By controlling the total amount of rare earth and the content of boron, a is more than or equal to 31 and less than or equal to 33, and b is more than or equal to 0.9 and less than or equal to 0.95, the content of a rare earth-rich phase in the liquid phase sintering process of the permanent magnet is ensured, so that the magnetic property is improved.

By controlling the total amount of rare earth and the content of boron, the microstructure of the rapid hardening melt-spun strip is ensured to be composed of good columnar crystals, and rare earth-rich phases are filled among the columnar crystals, which is the precondition guarantee of the magnetic property of the magnet. The subsequent one-stage tempering process effectively regulates the composition of the rare earth-rich phase, forms a good crystal boundary structure and improves the coercive force of the magnet. The mixed rare earth sintered neodymium iron boron permanent magnet with the chemical components does not need aging treatment in a high-temperature stage, and can reach the optimal value of coercive force only through aging treatment in a low-temperature stage.

Comparative example 1

The mass percentage is (MM)_0.25Re_0.75)₃₀Fe_balB₁Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1The chemical components are mixed, and the powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of rapid hardening and melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, orienting and molding the magnetic powder in a 2T magnetic field under the protection of nitrogen, and cold isostatic pressing at 200MPa to obtain a green body. Putting the green body into a vacuum sintering furnace, sintering at 1060 ℃ and keeping the temperature for 5 hours; then, the magnet was subjected to primary tempering heat treatment at 900 ℃ for 3 hours and then secondary tempering treatment at 500 ℃ for 3 hours, and the magnetic properties of the obtained magnet were as shown in Table 1.

Comparative example 2

The mass percentage is (MM)_0.25Re_0.75)₃₂Fe_balB_0.92Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1The chemical components are mixed, and the powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of rapid hardening and melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, orienting and molding the magnetic powder in a 2T magnetic field under the protection of nitrogen, and cold isostatic pressing at 200MPa to obtain a green body. Putting the green body into a vacuum sintering furnace, sintering at 1060 ℃ and keeping the temperature for 5 hours; then, the magnet was subjected to primary tempering heat treatment at 900 ℃ for 3 hours and then secondary tempering treatment at 500 ℃ for 3 hours, and the magnetic properties of the obtained magnet were as shown in Table 1.

Example 1

The mass percentage is (MM)_0.25Re_0.75)₃₂Fe_balB_0.92Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1Chemical ingredient compounding ofThe powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of quick setting melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, orienting and molding the magnetic powder in a 2T magnetic field under the protection of nitrogen, and cold isostatic pressing at 200MPa to obtain a green body. Putting the green body into a vacuum sintering furnace, sintering at 1060 ℃ and keeping the temperature for 5 hours; then, tempering the magnet at 500 ℃ for 3 hours to obtain a magnet having magnetic properties as shown in Table 1

TABLE 1

Performance parameter	Br/kGs	Hcj/kOe	(BH)max/MGOe	Squareness/%)
					Comparative example 1	13.08	7.698	37.68	76.2
Comparative example 2	13.03	12.19	40.96	96.7
					Example 1	12.88	11.89	40.14	95.1

Description of the drawings: in comparative example 1, the total rare earth content a of the magnet was 30, the boron content b was 1, and the magnetic properties were low.

The total amount of rare earth in the magnet in example 1 is preferably 32 a, and the boron content b is 0.92, and the magnetic performance is significantly higher than that in comparative example 1. The magnet of example 1 was not tempered at 900 c for 3 hours and still maintained comparable magnetic properties to comparative example 2. The comparison shows that the proper total amount of the rare earth can ensure the higher magnetic performance of the permanent magnet, the invention not only shortens the process flow and reduces the production energy consumption, but also ensures that the magnet can obtain better magnetic performance.

Comparative example 3

The mass percentage is (MM)_0.25Re_0.75)₃₃Fe_balB_0.9Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1The chemical components are mixed, and the powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of rapid hardening and melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, orienting and molding the magnetic powder in a 2T magnetic field under the protection of nitrogen, and cold isostatic pressing at 200MPa to obtain a green body. Putting the green body into a vacuum sintering furnace, sintering at 1060 ℃ and keeping the temperature for 5 hours; then, the magnet was subjected to primary tempering heat treatment at 900 ℃ for 3 hours and then secondary tempering treatment at 500 ℃ for 3 hours, and the magnetic properties of the obtained magnet were as shown in Table 2.

Comparative example 4

The mass percentage is (MM)_0.25Re_0.75)₃₀Fe_balB₁Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1The chemical components are mixed, and the powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of rapid hardening and melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, and making the magnetic powder under the protection of nitrogenOriented and molded under a 2T magnetic field, and is made into a green body through cold isostatic pressing at 200 MPa. The green body was placed in a vacuum sintering furnace, sintered at 1060 ℃ for 5 hours, and then subjected to primary tempering at 500 ℃ for 3 hours, and the magnetic properties of the obtained magnet were as shown in table 3.

Example 2

The mass percentage is (MM)_0.25Re_0.75)₃₃Fe_balB_0.9Co_0.5Al_0.4Ga_0.2Cu_0.1Zr_0.1The chemical components are mixed, and the powder with the average powder granularity of less than 3.5 mu m is prepared by adopting the process flows of rapid hardening and melt spinning, hydrogen crushing and jet milling. Adding lubricant and antioxidant into the magnetic powder, mixing, orienting and molding the magnetic powder in a 2T magnetic field under the protection of nitrogen, and cold isostatic pressing at 200Mpa to obtain a green body. The green body was placed in a vacuum sintering furnace, sintered at 1060 ℃ for 5 hours, and then subjected to primary tempering at 500 ℃ for 3 hours, and the magnetic properties of the obtained magnet were as shown in table 2.

TABLE 2

Performance parameter	Br/kGs	Hcj/kOe	(BH)max/MGOe	Squareness/%)
					Comparative example 3	12.77	12.07	39.74	97
Comparative example 4	13.05	9.00	38.88	73.1
					Example 2	12.88	12.09	40.73	98.5

Description of the drawings: it can be seen from comparison of comparative example 3 and example 2 that the magnet of example 2, which has not been tempered at 900 c for 3 hours, still retains magnetic properties comparable to comparative example 3, with a magnetic energy product that is even significantly higher than that of comparative example 3, which has been tempered in more than one stage. The comparison shows that the invention not only shortens the process flow and reduces the production energy consumption, but also the magnet can obtain better magnetic performance.

In comparative example 4, the total rare earth content a of the magnet was 30, the boron content b was 1, and the magnetic properties were low.

The total rare earth content of the magnet in example 2 is preferably 33 a, the boron content b is 0.9, and the magnetic performance is significantly higher than that of comparative example 4. The above comparison shows that reasonable total amount of rare earth and boron content are the precondition for ensuring the performance of the magnet,

the terminology used herein is for the purpose of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.