CN115938778A - Preparation method of sintered neodymium-iron-boron permanent magnet material with high temperature stability - Google Patents
Preparation method of sintered neodymium-iron-boron permanent magnet material with high temperature stability Download PDFInfo
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Abstract
The invention provides a preparation method of a sintered neodymium iron boron permanent magnet material with high temperature stability, which comprises the following chemical components of formula RE x B y Co a M b Fe 100‑x‑y‑a‑b The main phase alloy powder and the chemical composition are shown as the formula Re c B d Co e M f Fe 100‑c‑d‑e‑f The auxiliary phase alloy powder is used as a raw material, and after the auxiliary phase alloy powder and the raw material are mixed, the oriented pressing, sintering and tempering are sequentially carried out, so that the sintered neodymium iron boron material with high temperature stability is obtained. The invention uses double alloy to introduce the auxiliary phase and the boron-rich phase in the crystal boundary to carry out alloying reaction, regenerates a new main phase shell layer, stabilizes the main phase by using the cobalt concentration difference between the two phases, inhibits the generation of impurity phases, can prepare the high-cobalt sintered neodymium-iron-boron magnet with high temperature stability, has easy process control and is suitable for batch production.
Description
Technical Field
The invention relates to the technical field of rare earth permanent magnet materials, in particular to a preparation method of a sintered neodymium iron boron permanent magnet material with high temperature stability.
Background
Since the 60 th generation of the 20 th century, the research, production and application of rare earth permanent magnet materials have been rapidly developed, and the rare earth permanent magnet materials are developed into the third generation of rare earth permanent magnet neodymium iron boron. Compared with the rare earth permanent magnet materials of the first two generations, the neodymium iron boron permanent magnet material has the characteristics of high remanence, high magnetic energy product and high intrinsic coercive force, and is one of the permanent magnet materials found in the world at present, and the magnetic property of the permanent magnet material is strongest. However, because of its poor temperature stability, its application in the fields of high temperature motors, precision instruments, etc. has been greatly limited. In order to meet the application requirements of industries such as new energy automobiles, national defense and military industry and the like on high temperature stability, the temperature stability of the neodymium iron boron is improved, and the development of the neodymium iron boron permanent magnet material with high temperature stability has important significance.
Research shows that Co atoms are added into the magnet to replace Fe and preferentially occupy RE 2 Fe 14 8j of the Compound B 1 Crystal position, which reduces the negative exchange effect and strengthens the exchange effect of 3d-3d metal atoms; RE 2 Co 14 The 3d-3d exchange coupling in B is RE 2 Fe 14 B is 3 times of the magnetic flux, plays a role in improving the Curie temperature and reducing the temperature coefficient of remanence, and becomes an important means for improving the temperature stability of the magnet. However, when the Co content is high, RE (Fe, co) appears 2 、RE(Fe，Co) 3 、RE(Fe，Co) 4 B、RE 2 (Fe，Co) 17 And the like. The coercive force of the sintered neodymium iron boron is a structure sensitive parameter, and the ideal structure of the sintered neodymium iron boron material is as follows: uniform thin zone grain boundary wrapping RE 2 Fe 14 The B main phase crystal grains are fine and are uniformly distributed. The presence of a hetero-phase, where RE (Fe, co) 2 Is a soft magnetic phase, is precipitated along the grain boundary, weakens the magnetic isolation effect among main phase grains, and has no coercive force on the magnetAnd (6) benefiting. In addition, the presence of the hetero-phase reduces the main phase ratio and lowers the remanence of the magnet. Therefore, it is a challenge to suppress the impurity phase in the high cobalt magnet and to prepare a magnet having both high performance and high temperature stability.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method of a sintered neodymium-iron-boron magnet, and the prepared neodymium-iron-boron permanent magnet material has high temperature stability, high coercivity and high remanence.
In view of this, the present application provides a method for preparing a sintered ndfeb permanent magnetic material with high temperature stability, which includes:
mixing the main phase alloy powder with the components shown as the formula (I) and the auxiliary phase alloy powder with the components shown as the formula (II), and then sequentially carrying out orientation compression, sintering and tempering to obtain the sintered neodymium-iron-boron permanent magnet material with high temperature stability;
RE x B y Co a M b Fe 100-x-y-a-b (I)，
in the formula (I), RE is selected from one or more of Dy, tb, pr, nd, la, ce, Y and Ho;
m is selected from one or more of Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤x≤34，1.0≤y≤1.8，10≤a≤30，0.1≤b≤2.0；
RE c B d Co e M f Fe 100-c-d-e-f (II)，
in the formula (II), RE is one or more selected from Dy, tb, pr, nd, la, ce, Y and Ho;
m is selected from one or more of Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤c≤70，0≤d≤2，0≤e＜a≤20，0.1≤f≤50。
preferably, the main phase molecule of the sintered NdFeB with high temperature stability is RE 2 (Fe，Co) 14 B。
Preferably, the auxiliary phase alloy powder is 0.5 to 30wt% of the total of the main phase alloy powder and the auxiliary phase alloy powder.
Preferably, the particle size of the main phase alloy powder is 1 to 5 μm, and the particle size of the auxiliary phase alloy powder is 1 to 5 μm.
Preferably, the magnetic field intensity of the orientation pressure type is 1.0-2.0T, and the pressure is 100-200 MPa.
Preferably, the sintering process specifically comprises:
sintering the oriented magnet at 900-1100 deg.c for 1-6 hr, lowering the temperature to 800-1000 deg.c, maintaining for 0.5-2 hr, and raising the temperature to 900-1100 deg.c for 0.5-2 hr.
Preferably, the preparation method of the main-phase alloy powder and the auxiliary-phase alloy powder comprises the following steps:
and respectively carrying out hydrogen crushing on the main-phase alloy casting sheet and the auxiliary-phase alloy casting sheet, and then carrying out jet milling.
Preferably, the hydrogen pressure for hydrogen crushing is independently selected from 0.1-0.5 MPa, the hydrogen absorption time is independently selected from 2-5 h, the dehydrogenation temperature is independently selected from 300-500 ℃, and the dehydrogenation time is independently selected from 4-8 h.
Preferably, the hydrogen content of the powder obtained by hydrogen crushing is independently less than 1500ppm, and the average particle size of the powder is independently selected from 100 to 250 μm.
Preferably, the tempering treatment is firstly carried out at 800-1000 ℃ for 2-4 h and then at 450-600 ℃ for 2-4 h.
The application provides a preparation method of a sintered neodymium iron boron permanent magnet material with high temperature stability, which comprises the following chemical components in formula RE x B y Co a M b Fe 100-x-y-a-b The main phase alloy powder and the chemical composition are shown as the formula Re c B d Co e M f Fe 100-c-d-e-f The method comprises the following steps of (1) preparing a magnet by using two kinds of alloy powder with different cobalt contents of a main phase and an auxiliary phase as raw materials, wherein the cobalt content of the auxiliary phase alloy powder is lower than that of the main phase alloy; secondly, when the boron content of the main phase alloy powder is more than 1.0wt%, a boron-rich phase (Re) is generated 1+ε Fe 4 B 4 ) The cobalt element and rare earth element introduced into the auxiliary phase can react with the boron-rich phase to generate a new main phase RE containing cobalt 2 (Fe，Co) 14 B. The two modes can inhibit the cobalt element and the rare earth element in the crystal boundary from generating a mixed phase, improve the cobalt content in the main phase crystal grains and improve the temperature stability of the magnet.
In conclusion, the invention selects reasonable element components and carries out proportioning design, can control the microstructure of the obtained rapid hardening alloy cast sheet to obtain fine columnar crystals without adopting special casting equipment, has easy control of process flow and is suitable for large-scale production. The residual magnetism and coercive force of the neodymium iron boron permanent magnet material prepared by the method provided by the invention are simultaneously improved, and the comprehensive performance is excellent.
Drawings
Fig. 1 is a schematic diagram of a preparation principle of the sintered nd-fe-b permanent magnetic material with high temperature stability provided by the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
In view of the problem that the cobalt-containing impurity phase in the neodymium-iron-boron magnet is not beneficial to the magnetic performance of the magnet in the prior art, the method utilizes a double-main-phase mode (high cobalt phase and low cobalt phase) and utilizes a boron-rich phase and Co in a crystal boundary to form a cobalt-containing main phase, thereby inhibiting the generation of impurity phase, and allowing more Co elements to enter main-phase crystal grains to form RE 2 (Fe,Co) 14 B, the more Co content in the grains, the better the temperature stability of the magnet. Specifically, the embodiment of the invention discloses a preparation method of a sintered neodymium iron boron permanent magnet material with high temperature stability, which comprises the following steps:
mixing the main phase alloy powder with the components shown as the formula (I) and the auxiliary phase alloy powder with the components shown as the formula (II), and then sequentially carrying out orientation compression, sintering and tempering to obtain the sintered neodymium-iron-boron permanent magnet material with high temperature stability;
RE x B y Co a M b Fe 100-x-y-a-b (I)，
in the formula (I), RE is selected from one or more of Dy, tb, pr, nd, la, ce, Y and Ho;
m is one or more selected from Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤x≤34，1.0≤y≤1.8，10≤a≤30，0.1≤b≤2.0；
Re c B d Co e M f Fe 100-c-d-e-f (II)，
in the formula (II), RE is one or more selected from Dy, tb, pr, nd, la, ce, Y and Ho;
m is one or more selected from Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤c≤70，0≤d≤2，0≤e＜a≤20，0.1≤f≤50。
the mechanism schematic diagram of the sintered neodymium iron boron permanent magnet with high temperature stability is shown in fig. 1, a high-cobalt main phase and a low-cobalt main phase exist in the magnet, the cobalt content in the low-cobalt main phase is lower than that in the high-cobalt main phase, co atoms in the high-cobalt main phase can migrate to a grain boundary in the sintering process, and due to the fact that the concentration difference of Co exists, cobalt in a region with higher concentration in the grain boundary can diffuse to grains with lower concentration in the low-cobalt main phase; in addition, co migrating from the grains to the grain boundaries metallurgically reacts with the boron-rich phase surrounding the main phase grains to form a new main phase. The two modes can inhibit the cobalt element and the rare earth element in the crystal boundary from generating a mixed phase, improve the cobalt content in the main phase crystal grains and improve the temperature stability of the magnet.
In the present invention, x in the formula I is preferably 30 to 33, more preferably 31 to 32; y is preferably 1.2 to 1.8, more preferably 1.4 to 1.6, most preferably 1.5; a is preferably from 10 to 28, more preferably from 16 to 22, most preferably 20; b is preferably 0.1 to 0.5, more preferably 0.2 to 0.4, and most preferably 0.3.
In the present invention, in the formula II, c is preferably 30 to 60, more preferably 45 to 55, and most preferably 50; d is preferably from 0 to 1, more preferably from 0 to 0.8, most preferably 0.4; e is preferably from 5 to 15, more preferably from 8 to 12, most preferably 10; f is preferably 0.5 to 40, more preferably 1 to 25.
In the present invention, the average particle diameters of the main-phase alloy powder and the auxiliary-phase alloy powder are preferably 2 to 5 μm, and more preferably 3 to 4 μm, independently.
In the present invention, the method for preparing the main phase alloy powder preferably includes:
and (3) carrying out gas flow grinding crushing on the main phase alloy cast sheet after hydrogen crushing.
In the present invention, the method for producing the main phase alloy cast sheet preferably includes:
and smelting the alloy raw materials and then quickly solidifying to obtain the main-phase alloy cast sheet.
The smelting method is not particularly limited, and the alloy raw materials are mixed according to the components obtained in advance by adopting a smelting method known by the technical personnel in the field and then smelted. In the present invention, the degree of vacuum in the rapid setting process is preferably less than 10 -2 Pa, the rotating speed is preferably 1.8-3.0 m/s, and more preferably 2.0-2.5 m/s; the casting temperature is preferably 1200 to 1500 deg.C, more preferably 1300 to 1400 deg.C, and most preferably 1350 deg.C.
In the present invention, the hydrogen pressure in the hydrogen crushing process is preferably 0.1 to 0.4MPa, more preferably 0.2 to 0.3MPa; the hydrogen absorption time is preferably 2 to 5 hours, and more preferably 3 to 4 hours; the dehydrogenation temperature is preferably 320 to 500 ℃, more preferably 350 to 450 ℃, and most preferably 400 ℃; the dehydrogenation is preferably vacuum dehydrogenation; the dehydrogenation time is preferably from 4 to 8 hours, more preferably from 5 to 7 hours, most preferably 6 hours.
In the present invention, the hydrogen content of the powder obtained after the hydrogen pulverization is preferably less than 1500ppm, and the average particle diameter of the powder is preferably 100 to 250. Mu.m, more preferably 150 to 200. Mu.m, and most preferably 160 to 180. Mu.m.
In the present invention, the method for preparing the secondary alloy powder preferably includes:
and (4) crushing the auxiliary phase alloy casting sheet by hydrogen, and then performing gas flow milling crushing.
In the present invention, the method for preparing the secondary phase alloy cast sheet preferably includes:
and smelting the alloy raw materials and then quickly solidifying to obtain the main-phase alloy cast sheet.
The smelting method is not particularly limited, and the alloy raw materials are mixed according to the components obtained in advance by adopting a smelting method well known by the technical personnel in the field and then smelted. In the present invention, the degree of vacuum in the rapid setting process is preferably less than 10 -2 Pa, the rotating speed is preferably 1.8-3.0 m/s, and more preferably 2.0-2.5 m/s; the casting temperature is preferably 900 to 1500 ℃, more preferably 1000 to 1400 ℃, more preferably 1100 to 1300 ℃, most preferably 1200 ℃.
In the invention, the selection range of the process parameters of the hydrogen crushing is consistent with that of the technical scheme, and is not repeated herein; the hydrogen content of the powder obtained after the hydrogen crushing is preferably less than 1500ppm, and the average particle diameter of the powder is preferably 100 to 250. Mu.m, more preferably 150 to 200 μm, and most preferably 160 to 180. Mu.m.
In the present invention, the thicknesses of the primary alloy cast piece and the secondary alloy cast piece are independently preferably 0.1 to 0.5mm, more preferably 0.2 to 0.4mm, and most preferably 0.3mm.
In the present invention, the mass of the secondary alloy powder is preferably 0.5 to 30%, more preferably 1 to 25%, more preferably 5 to 20%, and most preferably 10 to 15% of the total mass of the main phase alloy powder and the secondary alloy powder.
In the present invention, the orientation die is preferably subjected to isostatic pressing in a magnetic field; the intensity of the magnetic field is preferably 1.5 to 2.0T, more preferably 1.6 to 1.9T, and most preferably 1.7 to 1.8T; the pressure of the isostatic pressing is preferably 150 to 200MPa, more preferably 160 to 190MPa, and most preferably 170 to 180MPa.
In the present invention, the sintering is preferably vacuum sintering. In the invention, the sintering is specifically as follows:
sintering the oriented magnet at 900-1100 deg.c for 1-6 hr, lowering the temperature to 800-1000 deg.c, maintaining for 0.5-2 hr, and raising the temperature to 900-1100 deg.c for 0.5-2 hr.
More specifically, the sintering temperature is preferably 900 to 1100 ℃, more preferably 950 to 1050 ℃, and most preferably 1000 ℃; the sintering time is preferably 2 to 5 hours, more preferably 3 to 4 hours. The temperature is reduced to be preferably 800-1000 ℃, most preferably 900 ℃, and the heat preservation time is preferably 0.5-2 h, most preferably 1h; the temperature is raised to the sintering temperature for a time period of preferably 0.5 to 2 hours, most preferably 1 hour.
In the invention, the tempering treatment is firstly carried out for 2 to 4 hours at the temperature of 800 to 1000 ℃ and then for 2 to 4 hours at the temperature of 450 to 600 ℃.
The invention inhibits the generation of impure phases in the high-cobalt magnet and improves the utilization rate of cobalt by two modes, and the high-temperature stable magnet is prepared; firstly, preparing a magnet by using two alloy powders with different cobalt contents of a main phase and an auxiliary phase, wherein the cobalt content of the auxiliary phase alloy powder is lower than that of the main phase alloy, cobalt in a high-cobalt main phase diffuses to a grain boundary ((1)) in a sintering process, and cobalt in a higher-concentration area in the grain boundary diffuses to a main phase grain with a lower concentration ((2)) due to the cobalt concentration difference; secondly, when the boron content of the main phase alloy powder is not less than 1.0wt%, a boron-rich phase (RE) is generated 1+ε Fe 4 B 4 ) The cobalt element and rare earth element introduced into the auxiliary phase react with the boron-rich phase in the designed heat treatment window ((2)) to generate a new main phase RE containing cobalt 2 (Fe,Co) 14 B ((3)). The two modes can inhibit the cobalt element and the rare earth element in the crystal boundary from generating a mixed phase, improve the cobalt content in the main phase crystal grains and improve the temperature stability of the magnet.
For further understanding of the present invention, the following examples are given to illustrate the preparation method of the sintered ndfeb permanent magnetic material with high temperature stability, and the scope of the present invention is not limited by the following examples.
Example 1
Smelting according to the proportion of each element to prepare a main phase rapid hardening alloy cast sheet and an auxiliary phase rapid hardening alloy cast sheet, wherein the vacuum degree in the preparation process of the main phase rapid hardening alloy cast sheet is 3x10 -2 Pa, the rotating speed is 2.0m/s, the pouring temperature is 1380 ℃, and the vacuum degree is 3x10 in the preparation process of the auxiliary phase rapid-hardening alloy cast sheet -2 Pa, rotation speed of 2.0m/s, casting temperature of 1350 deg.C, and main phase chemical formula of Nd 29.5 B 1.0 Co 20 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 49.0 Mass of the auxiliary phase chemical formulaPercentage of Nd 29.5 B 1.0 Co 10 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 59.0 ；
Respectively preparing powder from a main-phase alloy casting sheet and an auxiliary-phase alloy casting sheet, absorbing hydrogen for 3 hours at room temperature under the condition that the hydrogen pressure is 0.2MPa, and carrying out vacuum dehydrogenation for 9 hours at 450 ℃ to obtain hydrogen broken powder; then, continuously crushing the hydrogen powder by using an airflow mill to respectively obtain main-phase alloy powder and auxiliary-phase alloy powder;
mixing main-phase alloy powder and auxiliary-phase alloy powder, wherein the auxiliary-phase alloy powder accounts for 30% of the total weight (the main-phase alloy powder and the auxiliary-phase alloy powder), then carrying out orientation compression on the mixed powder in a 1.8T magnetic field, and carrying out isostatic pressing under the pressure of 180MPa to obtain a magnet; and then, under the condition of being isolated from the atmosphere, sending the magnet into a vacuum sintering furnace for sintering, wherein the sintering temperature is 1080 ℃, after sintering for 4 hours, reducing the temperature to 980 ℃, preserving the heat for 1 hour, then increasing the temperature to 1080 ℃, preserving the heat for 1 hour, and finally, respectively carrying out heat treatment for 2 hours at the temperature of 900 ℃ and the temperature of 500 ℃ to obtain the neodymium-iron-boron permanent magnet.
Comparative example 1
Smelting according to the proportion of each element to prepare the rapid hardening alloy cast piece, wherein the vacuum degree is 3x10 in the preparation process of the rapid hardening alloy cast piece -2 Pa, rotation speed of 2.0m/s, casting temperature of 1380 ℃ and chemical formula mass percentage of Nd 29.5 B 1.0 Co 17 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 52.0 The subsequent process is the same as in example 1;
detecting the remanence and the coercive force of the products prepared in the embodiment 1 and the comparative example 1 of the invention by adopting an ultra-high coercive force permanent magnet measuring instrument provided by HIRST company and having the model of PFM14.CN, and calculating the temperature coefficient of the remanence (20-120 ℃); testing a 400-900K thermomagnetic curve and determining the Curie temperature under a 500Oe magnetic field by adopting a vibration sample magnetometer provided by Quantum Design company and having a SQUID model; the XRD result of the magnet powder is subjected to Rietveld refinement calculation to obtain a phase ratio; the detection results are shown in table 1;
table 1 table of performance data of the ndfeb permanent magnets prepared in example 1 and comparative example 1
Example 2
Smelting according to the proportion of each element to prepare a main phase rapid hardening alloy cast sheet and an auxiliary phase rapid hardening alloy cast sheet, wherein the vacuum degree in the preparation process of the main phase rapid hardening alloy cast sheet is 3x10 -2 Pa, the rotating speed is 2.0m/s, the pouring temperature is 1340 ℃, and the vacuum degree in the preparation process of the auxiliary phase rapid-hardening alloy cast sheet is 3x10 -2 Pa, rotation speed of 2.0m/s, casting temperature of 950 ℃, and mass percentage of main phase chemical formula of Nd 29.5 B 1.2 Co 20 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 48.8 The auxiliary phase chemical formula is Pr by mass percent 60 Co 15 Al 25 ；
Respectively preparing powder from a main-phase alloy casting sheet and an auxiliary-phase alloy casting sheet, absorbing hydrogen for 3 hours at room temperature under the condition that the hydrogen pressure is 0.2MPa, and carrying out vacuum dehydrogenation for 9 hours at 450 ℃ to obtain hydrogen broken powder; then, continuously crushing the hydrogen broken powder by adopting an airflow mill to obtain main-phase alloy powder and auxiliary-phase alloy powder;
mixing main-phase alloy powder and auxiliary-phase alloy powder, wherein the auxiliary-phase alloy powder accounts for 5% of the total weight (the main-phase alloy powder and the auxiliary-phase alloy powder), then carrying out orientation compression on the mixed powder in a 1.8T magnetic field, and carrying out isostatic pressing under the pressure of 180MPa to obtain the magnet. And then, under the condition of being isolated from the atmosphere, sending the magnet into a vacuum sintering furnace for sintering, wherein the sintering temperature is 1060 ℃, after sintering for 4 hours, reducing the temperature to 950 ℃, preserving the heat for 1 hour, then increasing the temperature to 1060 ℃, preserving the heat for 1 hour, and finally, respectively carrying out heat treatment for 2 hours at the temperature of 900 ℃ and the temperature of 500 ℃ to obtain the neodymium-iron-boron permanent magnet.
Comparative example 2
An iron neodymium boron permanent magnet was prepared according to the method of example 2, differing from example 2 in that the chemical formula of the main phase was Nd in mass percent 29.5 B 0.9 Co 20 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 49.1 Assistance ofThe mass percentage of the phase chemical formula is Pr 60 Co 15 Al 25 。
The iron neodymium boron permanent magnets prepared in example 2 and comparative example 2 were tested for remanence, coercive force, temperature coefficient of remanence (20 ℃ C. To 120 ℃ C.), curie temperature, and comparative example by the methods of example 1 and comparative example 1, and the test results are shown in Table 2;
table 2 table of performance data of nd-fe-b magnets prepared in example 2 and comparative example 2
Example 3
Smelting according to the proportion of each element to prepare a main phase rapid hardening alloy cast sheet and an auxiliary phase rapid hardening alloy cast sheet, wherein the vacuum degree in the preparation process of the main phase rapid hardening alloy cast sheet is 3x10 -2 Pa, the rotating speed is 2.0m/s, the pouring temperature is 1380 ℃, and the vacuum degree is 3x10 in the preparation process of the auxiliary phase rapid-hardening alloy cast sheet -2 Pa, rotation speed of 2.0m/s, pouring temperature of 1050 ℃, and mass percentage of main phase chemical formula of Nd 24.8 Ce 4.03 La 1.24 Y 0.93 B 1.1 Cu 0.1 Co 20 Fe 47.8 The auxiliary phase chemical formula is Pr by mass percent 60 Co 15 Cu 25 ；
Respectively preparing powder from a main-phase alloy casting sheet and an auxiliary-phase alloy casting sheet, absorbing hydrogen for 3 hours at room temperature under the condition that the hydrogen pressure is 0.2MPa, and carrying out vacuum dehydrogenation for 9 hours at 450 ℃ to obtain hydrogen broken powder; then, continuously crushing the hydrogen broken powder by adopting an airflow mill to obtain main-phase alloy powder and auxiliary-phase alloy powder;
mixing main phase alloy powder and auxiliary phase alloy powder, wherein the auxiliary phase alloy powder accounts for 9% of the total weight (the main phase alloy powder and the auxiliary phase alloy powder), then carrying out orientation compression on the mixed powder in a 1.8T magnetic field, and carrying out isostatic pressing under the pressure of 180MPa to obtain the magnet. And then, under the condition of being isolated from the atmosphere, the magnet is sent into a vacuum sintering furnace for sintering, the sintering temperature is 1020 ℃, after 4 hours of sintering, the temperature is reduced to 950 ℃, the temperature is kept for 1 hour, then the temperature is increased to 1020 ℃, the temperature is kept for 1 hour, and finally, heat treatment is respectively carried out for 2 hours at the temperature of 900 ℃ and the temperature of 500 ℃, so that the neodymium-iron-boron permanent magnet is obtained.
Comparative example 3
An iron neodymium boron permanent magnet was produced according to the method of example 3, differing from example 3 in that the main phase chemical formula was Nd by mass percent 24.8 Ce 4.03 La 1.24 Y 0.93 B 0.9 Cu 0.1 Co 20 Fe 48.0 The auxiliary phase chemical formula is Pr by mass percent 60 Co 15 Cu 25 。
The permanent magnets of iron neodymium boron prepared in example 3 and comparative example 3 were tested for remanence, coercive force, temperature coefficient of remanence (20 ℃ C. To 120 ℃ C.), curie temperature, and comparative example according to the methods of example 1 and comparative example 1, and the test results are shown in Table 3;
table 3 table of performance data of the neodymium iron boron magnets prepared in example 3 and comparative example 3
The invention inhibits the generation of impure phases in the high-cobalt magnet and improves the utilization rate of cobalt by two modes, and the high-temperature stable magnet is prepared. Firstly, preparing a magnet by utilizing two kinds of alloy powder with different cobalt contents of a main phase and an auxiliary phase, wherein the cobalt content of the auxiliary phase alloy powder is lower than that of the main phase alloy, and in the sintering process, because the cobalt contents of the two kinds of powder have concentration difference, cobalt in a region with higher concentration in a crystal boundary can be diffused into main phase grains with lower concentration; secondly, when the boron content of the main phase alloy powder is not less than 1.0wt%, a boron-rich phase (RE) is generated 1+ε Fe 4 B 4 ) The cobalt element and rare earth element introduced into the auxiliary phase can react with the boron-rich phase to generate a new main phase RE containing cobalt 2 (Fe,Co) 14 B. The two modes can inhibit the cobalt element and the rare earth element in the crystal boundary from generating a mixed phase, improve the cobalt content in the main phase crystal grains and improve the temperature stability of the magnet.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, it is possible to make various improvements and modifications to the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A preparation method of a sintered NdFeB permanent magnet material with high temperature stability comprises the following steps:
mixing the main phase alloy powder with the components shown as the formula (I) and the auxiliary phase alloy powder with the components shown as the formula (II), and then sequentially carrying out orientation compression, sintering and tempering to obtain the sintered neodymium-iron-boron permanent magnet material with high temperature stability;
RE x B y Co a M b Fe 100-x-y-a-b (I)，
in the formula (I), RE is selected from one or more of Dy, tb, pr, nd, la, ce, Y and Ho;
m is selected from one or more of Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤x≤34，1.0≤y≤1.8，10≤a≤30，0.1≤b≤2.0；
RE c B d Co e M f Fe 100-c-d-e-f (II)，
in the formula (II), RE is selected from one or more of Dy, tb, pr, nd, la, ce, Y and Ho;
m is selected from one or more of Al, cu, ga, si, sn, ge, zr, ti and Zn;
29≤c≤70，0≤d≤2，0≤e＜a≤20，0.1≤f≤50。
2. the preparation method according to claim 1, wherein the main phase molecule of the high-temperature-stability sintered NdFeB is RE 2 (Fe，Co) 14 B。
3. The production method according to claim 1, wherein the secondary alloy powder is 0.5 to 30wt% of the total of the primary alloy powder and the secondary alloy powder.
4. The production method according to claim 1, wherein the particle size of the main phase alloy powder is 1 to 5 μm, and the particle size of the auxiliary phase alloy powder is 1 to 5 μm.
5. The production method according to claim 1, wherein the orientation die has a magnetic field strength of 1.0 to 2.0T and a pressure of 100 to 200MPa.
6. The preparation method according to claim 1, wherein the sintering process is specifically as follows:
sintering the oriented magnet at 900-1100 deg.c for 1-6 hr, lowering the temperature to 800-1000 deg.c, maintaining for 0.5-2 hr, and raising the temperature to 900-1100 deg.c for 0.5-2 hr.
7. The method according to claim 1, wherein the method for preparing the main-phase alloy powder and the auxiliary-phase alloy powder comprises the following steps:
and respectively carrying out hydrogen crushing on the main-phase alloy casting sheet and the auxiliary-phase alloy casting sheet, and then carrying out jet milling.
8. The method according to claim 7, wherein the hydrogen pressure for hydrogen fragmentation is independently selected from 0.1 to 0.5MPa, the hydrogen absorption time is independently selected from 2 to 5 hours, the dehydrogenation temperature is independently selected from 300 to 500 ℃, and the dehydrogenation time is independently selected from 4 to 8 hours.
9. The method of claim 7, wherein the hydrogen content of the powder obtained by hydrogen fracturing is independently less than 1500ppm, and the average particle size of the powder is independently selected from 100 to 250 μm.
10. The preparation method according to claim 1, wherein the tempering treatment is performed by maintaining the temperature at 800-1000 ℃ for 2-4 hours and then maintaining the temperature at 450-600 ℃ for 2-4 hours.
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