CN113012925A - Preparation method of high-magnetism low-rare earth content neodymium iron boron magnet - Google Patents
Preparation method of high-magnetism low-rare earth content neodymium iron boron magnet Download PDFInfo
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Abstract
The invention discloses a preparation method of a high-magnetism low-rare earth content neodymium iron boron magnet, which belongs to the technical field of magnet preparation. In the preparation process of the preparation method, dysprosium and terbium are not used, and Cu, Zr and Ti alloys are added and are matched with high-temperature sintering at the temperature higher than 1100 ℃, so that the movement of the grain boundary of the main phase is limited by the grain boundary of the Cu, Zr and Ti alloys, the growth of grains in the main phase is hindered, and the magnetic exchange among the grains in the main phase is blocked. And then the coercive force and the working temperature of the neodymium iron boron magnet are improved, the preparation of the magnet with high thermal stability is facilitated, meanwhile, rare earth metals Dy and Tb are not used, and the preparation cost of the magnet is greatly reduced.
Description
The application is divided into separate applications by taking an invention patent with the application date of 2019-07-16 and the application number of 2019106397192 and named as a preparation method of a neodymium-iron-boron magnet with low rare earth content as a parent.
Technical Field
The invention belongs to the technical field of magnet preparation, and particularly relates to a preparation method of a high-magnetism low-rare earth content neodymium iron boron magnet.
Background
Neodymium magnet (Neodymium magnet), also known as Neodymium-iron-boron magnet (NdFeB magnet), is made of Neodymium, iron, boron (Nd)2Fe14B) The tetragonal system crystal is formed. The neodymium iron boron magnet has the characteristics of small volume, light weight, strong magnetism and the like. Neodymium iron boron magnets have been used in the fields of automobiles, computers, information, aviation, and the like since their discovery. However, the curie temperature of the ndfeb magnet is low, and the magnetism of the ndfeb magnet is weakened along with the increase of the casting with high working temperature. In order to change the characteristics of the neodymium iron boron magnet, the coercivity of the neodymium magnet is improved by adding dysprosium (Dy) and terbium (Tb), and the thermal stability and magnetism of the neodymium magnet at high temperature are improved.
Both Dy and Tb are rare earth metals with lower contents than other metals, and with the recent widespread use of neodymium-iron-boron magnets, the mining amount of Dy and Tb is continuously increasing, making Dy and Tb expensive raw materials. If the using amount of Dy and Tb can be reduced or Dy and Tb are not used in the preparation process of the neodymium iron boron magnet, the cost of the neodymium iron boron magnet can be greatly reduced. In the prior art, although a preparation method for improving the neodymium iron boron magnet by adding cobalt (Co) exists, the problem of reduced magnetism is caused by adding Co.
Disclosure of Invention
In order to overcome the defects of the prior art, the technical problems to be solved by the invention are as follows: the preparation method of the neodymium iron boron magnet with high magnetism and low rare earth content, which does not use dysprosium and terbium, and has higher working temperature, is provided.
In order to solve the technical problems, the invention adopts the technical scheme that: a preparation method of a high-magnetism low-rare earth content neodymium iron boron magnet comprises the following steps:
step 1, mixing materials prepared by 1.5-3% of zirconium, 0.5-2% of titanium and the balance of copper in percentage by weight, then repeatedly smelting for many times under the protection of argon, and rapidly solidifying and casting the molten material when smelting for the last time to obtain an alloy casting sheet;
step 2, mixing materials which are prepared according to the weight percentage of 10-15% of praseodymium, 13-18% of neodymium, 0.8-1.5% of boron and the balance of iron, then smelting under the protection of argon, and rapidly solidifying the molten materials to obtain a main phase alloy cast sheet;
step 3, respectively carrying out hydrogen fracturing on the alloy casting sheet and the main phase casting sheet to obtain alloy powder and main phase powder;
step 4, adding alloy powder accounting for 2-5% of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill;
step 5, pressing and molding the neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1110-1120 ℃ for 7-9h, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet;
the time of the first-stage tempering in the step 5 is 3.5-4h, and the temperature is 900-; the time of the secondary tempering is 3-4h, and the temperature is 600-620 ℃.
Wherein, after the hydrogen breaking in the step 3 is finished, the method also comprises the step of vacuumizing and dehydrogenating, wherein the dehydrogenation temperature is 660-680 ℃, and the dehydrogenation time is 3-4.5 h.
Wherein, in the step 1, the content of zirconium is 2 percent, and the content of titanium is 0.8 percent; in the step 2, the content of praseodymium is 15%, the content of neodymium is 16%, and the content of boron is 1.5%.
The invention has the beneficial effects that: according to the preparation method of the neodymium iron boron magnet with low rare earth content, Dy and Tb are not added in the preparation process, and Cu, Zr and Ti alloys are added and are matched with high-temperature sintering at the temperature higher than 1100 ℃, so that the movement of the grain boundary of the main phase is limited by the alloy grain boundary of Cu, Zr and Ti, the growth of crystal grains in the main phase is hindered, and the magnetic exchange among the crystal grains in the main phase is blocked. And then the coercive force and the working temperature of the neodymium iron boron magnet are improved, the preparation of the magnet with high thermal stability is facilitated, meanwhile, rare earth metals Dy and Tb are not used, and the preparation cost of the magnet is greatly reduced.
Detailed Description
In order to explain the technical content, the objects and the effects of the present invention in detail, the following description will be given with reference to the embodiments.
The most key concept of the invention is as follows: and the alloy of Cu, Zr and Ti is used for replacing Dy and Tb, so that the coercive force and the working temperature of the neodymium iron boron magnet are improved.
The invention provides a preparation method of a neodymium iron boron magnet with low rare earth content, which comprises the following steps:
step 1, mixing materials of 1.5-3% of zirconium, 0.5-2% of titanium and the balance of copper according to weight percentage, then repeatedly smelting for many times under the protection of argon, and rapidly solidifying and casting the molten materials during the last smelting to obtain alloy cast pieces;
step 2, mixing 10-15% of praseodymium, 13-18% of neodymium, 0.8-1.5% of boron and the balance of iron according to the weight percentage, then smelting under the protection of argon, and rapidly solidifying and casting the molten material to obtain a main phase casting sheet;
step 3, respectively carrying out hydrogen fracturing on the alloy casting sheet and the main phase casting sheet to obtain alloy powder and main phase powder;
step 4, adding 2-5% of alloy powder into the main phase powder, fully and uniformly mixing, and crushing into neodymium iron boron powder with the particle size of 2.5-3.8 microns by using an airflow mill;
and 5, pressing and molding the neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1110-1120 ℃ for 7-9h at the heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain the neodymium iron boron magnet.
From the above description, the beneficial effects of the present invention are: according to the preparation method of the neodymium iron boron magnet with low rare earth content, Dy and Tb are not added in the preparation process, and Cu, Zr and Ti alloys are added and are matched with high-temperature sintering at the temperature higher than 1100 ℃, so that the movement of the grain boundary of the main phase is limited by the alloy grain boundary of Cu, Zr and Ti, the growth of crystal grains in the main phase is hindered, and the magnetic exchange among the crystal grains in the main phase is blocked. And then the coercive force and the working temperature of the neodymium iron boron magnet are improved, the preparation of the magnet with high thermal stability is facilitated, meanwhile, rare earth metals Dy and Tb are not used, and the preparation cost of the magnet is greatly reduced.
Further, in the step 1, the content of zirconium is 2%, and the content of titanium is 0.8%.
Further, in the step 2, the content of praseodymium is 14%, the content of neodymium is 18%, and the content of boron is 0.9%.
Furthermore, the smelting times in the step 1 are 3-6 times. The uniformity of mixing is ensured by multiple melting.
Further, after the hydrogen breaking in the step 3 is finished, vacuumizing and dehydrogenation treatment is further included, wherein the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4.5 hours.
Further, the time of the first-stage tempering in the step 5 is 4 hours, and the temperature is 950 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
Example 1:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing materials of 2% of zirconium, 0.8% of titanium and the balance of copper according to the weight percentage, then repeatedly smelting for 4 times under the protection of argon, and rapidly solidifying the molten materials to obtain alloy cast pieces during the last smelting;
step 2, mixing materials including 15% of praseodymium, 16% of neodymium, 1.5% of boron and the balance of iron according to the weight percentage, then smelting under the protection of argon, and rapidly solidifying and casting the molten materials to obtain a main phase casting sheet;
step 3, performing hydrogen breaking and vacuum pumping dehydrogenation treatment on the alloy casting sheet and the main phase casting sheet respectively to obtain alloy powder and main phase powder; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4.5 h;
step 4, adding alloy powder accounting for 5 percent of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 mu m by an airflow mill;
step 5, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1120 ℃ for 8h at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet A; wherein, the time of the first-stage tempering is 4h, and the temperature is 950 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet a is as follows: 13.58 KGs; coercivity Hcb is: 12.93 KOe; the magnetic energy product BH (max) is: 40.23 MGOe.
Example 2:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing 2.5 percent of zirconium, 2 percent of titanium and the balance of copper according to the weight percentage, then repeatedly smelting for 3 times under the protection of argon, and rapidly solidifying the molten material to obtain an alloy cast sheet during the last smelting;
step 2, mixing materials of 14% of praseodymium, 18% of neodymium, 0.9% of boron and the balance of iron according to the weight percentage, then smelting under the protection of argon, and rapidly solidifying and casting the molten materials to obtain a main phase casting sheet during smelting;
step 3, performing hydrogen breaking and vacuum pumping dehydrogenation treatment on the alloy casting sheet and the main phase casting sheet respectively to obtain alloy powder and main phase powder; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4 h;
step 4, adding alloy powder accounting for 3 percent of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 mu m by an airflow mill;
step 5, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1115 ℃ for 9 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet B; wherein, the time of the first-stage tempering is 3.5h, and the temperature is 980 ℃; the time of the secondary tempering is 3 hours, the temperature is 620 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet B is: 12.81 KGs; coercivity Hcb is: 12.20 KOe; the magnetic energy product BH (max) is: 38.64 MGOe.
Example 3:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing 3% of zirconium, 1.5% of titanium and the balance of copper according to the weight percentage, then repeatedly smelting for 6 times under the protection of argon, and rapidly solidifying the molten material to obtain an alloy cast sheet during the last smelting;
step 2, mixing materials of 10% of praseodymium, 15% of neodymium, 1.2% of boron and the balance of iron according to the weight percentage, then smelting under the protection of argon, and rapidly solidifying and casting the molten materials to obtain a main phase casting sheet;
step 3, performing hydrogen breaking and vacuum pumping dehydrogenation treatment on the alloy casting sheet and the main phase casting sheet respectively to obtain alloy powder and main phase powder; wherein the dehydrogenation treatment temperature is 660 ℃, and the dehydrogenation time is 3 h;
step 4, adding alloy powder accounting for 5 percent of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 mu m by an airflow mill;
step 5, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1110 ℃ for 7 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet C; wherein, the time of the first-stage tempering is 4h, and the temperature is 950 ℃; the time of the secondary tempering is 3.5h, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet C is: 12.62 KGs; coercivity Hcb is: 12.07 KOe; the magnetic energy product BH (max) is: 36.82 MGOe.
Example 4:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing materials of 1.8 percent of zirconium, 0.5 percent of titanium and the balance of copper according to weight percentage, then repeatedly smelting for 6 times under the protection of argon, and rapidly solidifying the molten materials to obtain alloy cast pieces during the last smelting;
step 2, mixing materials of praseodymium accounting for 12 percent of the weight percentage, neodymium accounting for 14 percent of the weight percentage, boron accounting for 0.8 percent of the weight percentage and iron accounting for the rest, then smelting under the protection of argon, and rapidly solidifying and casting the molten materials to obtain a main phase casting sheet during smelting;
step 3, performing hydrogen breaking and vacuum pumping dehydrogenation treatment on the alloy casting sheet and the main phase casting sheet respectively to obtain alloy powder and main phase powder; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4 h;
step 4, adding alloy powder accounting for 5 percent of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 mu m by an airflow mill;
step 5, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1120 ℃ for 9 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet D; wherein, the time of the first-stage tempering is 4h, and the temperature is 900 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet D is: 13.24 KGs; coercivity Hcb is: 12.74 KOe; the magnetic energy product BH (max) is: 39.88 MGOe.
Example 5:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing materials of 1.5 percent of zirconium, 1 percent of titanium and the balance of copper according to the weight percentage, then repeatedly smelting for 5 times under the protection of argon, and rapidly solidifying the molten materials to obtain alloy cast pieces during the last smelting;
step 2, mixing 13% of praseodymium, 13% of neodymium, 1% of boron and the balance of iron according to the weight percentage, then smelting under the protection of argon, and rapidly solidifying and casting the molten material to obtain a main phase casting sheet;
step 3, performing hydrogen breaking and vacuum pumping dehydrogenation treatment on the alloy casting sheet and the main phase casting sheet respectively to obtain alloy powder and main phase powder; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4.5 h;
step 4, adding alloy powder accounting for 5 percent of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 mu m by an airflow mill;
step 5, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1120 ℃ for 7h at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet E; wherein, the time of the first-stage tempering is 4h, and the temperature is 950 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet E is: 13.06 KGs; coercivity Hcb is: 12.56 KOe; the magnetic energy product BH (max) is: 38.58 MGOe.
Comparative example 1:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, uniformly mixing 2% of zirconium, 0.8% of titanium and the balance of copper by weight;
step 2, mixing 15 wt% of praseodymium, 16 wt% of neodymium, 1.5 wt% of boron and the balance of iron materials to obtain a main phase mixture, adding an alloy mixture accounting for 5 wt% of the main phase mixture into the main phase mixture to obtain a neodymium iron boron mixture, repeatedly smelting the neodymium iron boron mixture for 4 times under the protection of argon gas, and rapidly solidifying and casting the molten material to obtain a neodymium iron boron cast sheet during the last smelting;
step 3, carrying out hydrogen breaking and vacuum pumping dehydrogenation treatment on the neodymium iron boron cast sheet, and then crushing the neodymium iron boron cast sheet into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4.5 h;
step 4, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1120 ℃ for 8h at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet F; wherein, the time of the first-stage tempering is 4h, and the temperature is 950 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet F is: 12.39 KGs; coercivity Hcb is: 11.70 KOe; the magnetic energy product BH (max) is: 36.31 MGOe.
Comparative example 2:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing 14% of praseodymium, 18% of neodymium, 0.9% of boron and the balance of iron according to the weight percentage to obtain a main phase mixture, then adding 0.075% of zirconium in the total weight of the main phase mixture into the main phase mixture to obtain a neodymium iron boron mixture, repeatedly smelting the neodymium iron boron mixture for 3 times under the protection of argon, and rapidly solidifying and casting the molten material during the last smelting to obtain a neodymium iron boron casting sheet;
step 2, carrying out hydrogen breaking and vacuum pumping dehydrogenation treatment on the neodymium iron boron cast sheet, and then crushing the neodymium iron boron cast sheet into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4 h;
step 3, pressing and molding the neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1115 ℃ for 9 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet G; wherein, the time of the first-stage tempering is 3.5h, and the temperature is 980 ℃; the time of the secondary tempering is 3 hours, the temperature is 620 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet G is: 11.57 KGs; coercivity Hcb is: 11.08 KOe; the magnetic energy product BH (max) is: 34.18 MGOe.
Comparative example 3:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing 10% of praseodymium, 15% of neodymium, 1.2% of boron and the balance of iron according to the weight percentage to obtain a main phase mixture, adding 0.03% of titanium of the total weight of neodymium iron boron into the neodymium iron boron mixture to obtain a neodymium iron boron mixture, repeatedly smelting the neodymium iron boron mixture for 6 times under the protection of argon gas, and rapidly solidifying and casting the molten material during the last smelting to obtain a neodymium iron boron casting sheet;
step 2, carrying out hydrogen breaking and vacuum pumping dehydrogenation treatment on the neodymium iron boron cast sheet, and then crushing the neodymium iron boron cast sheet into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill; wherein the dehydrogenation treatment temperature is 660 ℃, and the dehydrogenation time is 3 h;
step 3, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1110 ℃ for 7 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet H; wherein, the time of the first-stage tempering is 4h, and the temperature is 950 ℃; the time of the secondary tempering is 3.5h, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet H is: 11.92 KGs; coercivity Hcb is: 11.16 KOe; the magnetic energy product BH (max) is: 35.86 MGOe.
Comparative example 4:
the preparation method of the neodymium iron boron magnet with low rare earth content specifically comprises the following steps:
step 1, mixing materials of praseodymium accounting for 12 weight percent, neodymium accounting for 14 weight percent, boron accounting for 0.8 weight percent and iron accounting for the balance to obtain a main phase mixture, adding copper accounting for 3.9 weight percent of the total weight of the main phase mixture into the main phase mixture to obtain a neodymium iron boron mixture, repeatedly smelting the neodymium iron boron mixture for 6 times under the protection of argon, and rapidly solidifying and casting the molten materials to obtain neodymium iron boron casting sheets;
step 2, carrying out hydrogen breaking and vacuum pumping dehydrogenation treatment on the neodymium iron boron cast sheet, and then crushing the neodymium iron boron cast sheet into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill; wherein, the dehydrogenation treatment temperature is 680 ℃, and the dehydrogenation time is 4 h;
step 3, pressing and molding neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1120 ℃ for 9 hours at a heating rate of 8-10 ℃/min, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet I; wherein, the time of the first-stage tempering is 4h, and the temperature is 900 ℃; the time of the secondary tempering is 4 hours, the temperature is 600 ℃, and argon is filled for cooling during cooling.
The remanence Br of the neodymium iron boron magnet I is as follows: 10.63 KGs; coercivity Hcb is: 9.84 KOe; the magnetic energy product BH (max) is: 32.47 MGOe.
Compared with the neodymium iron boron magnet with Cu, Zr and Ti added, the neodymium iron boron magnet with Cu, Zr and Ti added is obviously improved in magnetic force, and meanwhile, compared with the neodymium iron boron magnet prepared by directly adding Cu, Zr and Ti into raw materials, the neodymium iron boron magnet prepared by firstly preparing Cu, Zr and Ti into alloy is better in magnetic property.
In summary, according to the preparation method of the neodymium iron boron magnet with low rare earth content provided by the invention, Dy and Tb are not added in the preparation process, and the alloy grain boundary of Cu, Zr and Ti is added to be matched with high-temperature sintering at the temperature higher than 1100 ℃, so that the movement of the grain boundary of the main phase is limited by the alloy grain boundary of Cu, Zr and Ti, the growth of crystal grains in the main phase is hindered, and the magnetic exchange among the crystal grains in the main phase is blocked. And then the coercive force and the working temperature of the neodymium iron boron magnet are improved, the preparation of the magnet with high thermal stability is facilitated, meanwhile, rare earth metals Dy and Tb are not used, and the preparation cost of the magnet is greatly reduced.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention in the specification or directly or indirectly applied to the related technical field are included in the scope of the present invention.
Claims (3)
1. A preparation method of a high-magnetism low-rare earth content neodymium iron boron magnet is characterized by comprising the following steps:
step 1, mixing materials prepared by 1.5-3% of zirconium, 0.5-2% of titanium and the balance of copper in percentage by weight, then repeatedly smelting for many times under the protection of argon, and rapidly solidifying and casting the molten material when smelting for the last time to obtain an alloy casting sheet;
step 2, mixing materials which are prepared according to the weight percentage of 10-15% of praseodymium, 13-18% of neodymium, 0.8-1.5% of boron and the balance of iron, then smelting under the protection of argon, and rapidly solidifying the molten materials to obtain a main phase alloy cast sheet;
step 3, respectively carrying out hydrogen fracturing on the alloy casting sheet and the main phase casting sheet to obtain alloy powder and main phase powder;
step 4, adding alloy powder accounting for 2-5% of the total weight of the main phase powder into the main phase powder, fully and uniformly mixing, and crushing the mixture into neodymium iron boron powder with the particle size of 2.5-3.8 microns through an airflow mill;
step 5, pressing and molding the neodymium iron boron powder in an oriented magnetic field of 2.1T to obtain a pressed compact, sintering the pressed compact at 1110-1120 ℃ for 7-9h, and then performing primary tempering and secondary tempering to obtain a neodymium iron boron magnet;
the time of the first-stage tempering in the step 5 is 3.5-4h, and the temperature is 900-; the time of the secondary tempering is 3-4h, and the temperature is 600-620 ℃.
2. The method for preparing a neodymium-iron-boron magnet with high magnetism and low rare earth content as claimed in claim 1, wherein after the hydrogen breaking in step 3 is finished, the method further comprises a vacuum-pumping dehydrogenation treatment, wherein the dehydrogenation treatment temperature is 660-680 ℃, and the dehydrogenation time is 3-4.5 h.
3. The method for preparing a high-magnetism low-rare earth content neodymium iron boron magnet according to claim 1, wherein in the step 1, the content of zirconium is 2%, and the content of titanium is 0.8%; in the step 2, the content of praseodymium is 15%, the content of neodymium is 16%, and the content of boron is 1.5%.
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