CN117790101A - Cerium-containing neodymium-iron-boron sintered permanent magnet and preparation method thereof - Google Patents
Cerium-containing neodymium-iron-boron sintered permanent magnet and preparation method thereof Download PDFInfo
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- 229910052684 Cerium Inorganic materials 0.000 title claims abstract description 35
- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 31
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 title claims abstract description 29
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 145
- 239000000956 alloy Substances 0.000 claims abstract description 145
- 239000002994 raw material Substances 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 11
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 6
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 3
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 3
- 239000000843 powder Substances 0.000 claims description 87
- 238000000034 method Methods 0.000 claims description 36
- 230000008569 process Effects 0.000 claims description 29
- 238000000227 grinding Methods 0.000 claims description 25
- 239000011812 mixed powder Substances 0.000 claims description 22
- 238000005245 sintering Methods 0.000 claims description 19
- 238000000265 homogenisation Methods 0.000 claims description 17
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 16
- 239000002245 particle Substances 0.000 claims description 15
- 238000003723 Smelting Methods 0.000 claims description 14
- 230000032683 aging Effects 0.000 claims description 14
- 238000005266 casting Methods 0.000 claims description 14
- 238000000462 isostatic pressing Methods 0.000 claims description 13
- 230000005291 magnetic effect Effects 0.000 claims description 12
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 6
- 238000009461 vacuum packaging Methods 0.000 claims description 6
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 31
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 11
- 150000002910 rare earth metals Chemical class 0.000 abstract description 10
- 239000000463 material Substances 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 60
- 238000010438 heat treatment Methods 0.000 description 14
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical group [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 14
- 239000010949 copper Substances 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 239000003963 antioxidant agent Substances 0.000 description 7
- 230000003078 antioxidant effect Effects 0.000 description 7
- 238000003756 stirring Methods 0.000 description 7
- 238000007792 addition Methods 0.000 description 6
- 238000004453 electron probe microanalysis Methods 0.000 description 6
- WMOHXRDWCVHXGS-UHFFFAOYSA-N [La].[Ce] Chemical compound [La].[Ce] WMOHXRDWCVHXGS-UHFFFAOYSA-N 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- LENJPRSQISBMDN-UHFFFAOYSA-N [Y].[Ce] Chemical compound [Y].[Ce] LENJPRSQISBMDN-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
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- 238000012360 testing method Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- 235000012054 meals Nutrition 0.000 description 2
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- 229910052760 oxygen Inorganic materials 0.000 description 2
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- 230000005307 ferromagnetism Effects 0.000 description 1
- 238000005324 grain boundary diffusion Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
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Abstract
The invention belongs to the technical field of permanent magnet materials, and relates to a cerium-containing neodymium-iron-boron sintered permanent magnet and a preparation method thereof. The preparation raw materials of the cerium-containing neodymium-iron-boron sintered permanent magnet comprise an alloy I and an alloy II, wherein the chemical molecular formula of the alloy I is [ (Pr) x2 Nd 1‑x1‑ x2 RL x1 ] a M1 b M2 c B d Fe 100‑a‑b‑c‑d 0 < x1 is less than or equal to 0.4,0 < x2 is less than or equal to 0.2, 28.5 is less than or equal to a is less than or equal to 30,0 < b is less than or equal to 3,0 < c is less than or equal to 0.8,0.85 is less than or equal to d is less than or equal to 0.95, wherein RL is one or two of La and Ce, M1 is one or more of Al, cu, ga, co, mn, and M2 is one or more of Nb, zr, hf, ti, V; the chemical molecular formula of the alloy II is Pr a1 Ce b1 Ga c1 Fe 100‑a1‑b1‑c1 A1+b1 is more than or equal to 50 and less than or equal to 70, b1/a1 is more than or equal to 1 and less than or equal to 2, and c1 is more than or equal to 5 and less than or equal to 10. The invention adopts cerium-containing light rare earth alloy doping to improve the coercive force of the cerium-containing neodymium iron boron sintered permanent magnet.
Description
Technical Field
The invention belongs to the technical field of permanent magnet materials, and relates to a cerium-containing neodymium-iron-boron sintered permanent magnet and a preparation method thereof.
Background
In recent years, with the rapid expansion of the application field of neodymium iron boron magnets, the demand for raw materials has become larger and larger, but the material cost is also gradually increased due to higher cost of rare earth exploitation and with the increase of national regulatory forces. Therefore, the application of the high-abundance permanent magnet with relatively low price in the market is wider and wider, and the market competition is stronger. However, the addition of the high-abundance rare earth element lanthanum cerium can cause the deterioration of the coercive force of the neodymium-iron-boron magnet, so that the increase of the lanthanum-cerium addition amount and the non-reduction of the coercive force become a problem to be solved in the current lanthanum-cerium magnet preparation.
The conventional method for improving the performance of the lanthanum-cerium magnet mainly comprises the technologies of a double main phase process, grain refinement, an oxygen control process and the like, and the coercivity of the magnet is improved in a mode of grain boundary phase distribution, grain refinement and magnet oxygen content reduction. As disclosed in chinese patent CN111091944B, a preparation method of a lanthanum-rich cerium-yttrium multi-main phase fine-grain rare earth permanent magnetic material is disclosed, which adopts two types of main alloy magnetic powder to mix, uses the characteristics of rapid heating speed, short heating time and short heat preservation time of discharge plasma sintering technology, controls the inter-diffusion and chemical heterogeneity of elements in the lanthanum-rich cerium-yttrium multi-main phase magnet, precisely controls various core-shell morphology, magnetic hardening and pinning effects, improves the coercive force of the magnet, simultaneously uses rapid sintering to avoid abnormal growth of crystal grains, realizes uniformity of internal structure of the magnet, has fine crystal grains, and improves the comprehensive magnetic property of the lanthanum-rich cerium-yttrium multi-main phase rare earth permanent magnetic material; but the spark plasma sintering technology with higher cost is introduced, which is not beneficial to industrial production.
During early preparation of lanthanum cerium magnet, ceFe 2 The phase is considered as the phase affecting the coercive force of the magnet, and the preparation process is regulated by a smelting process to reduce CeFe 2 The proportion of phase formation, but with the intensive research, a great deal of research has now shown that CeFe 2 The even distribution of the phases at the grain boundary can effectively improve the coercive force of the magnet.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the cerium-containing neodymium-iron-boron sintered permanent magnet and the preparation method thereof, wherein the cerium-containing neodymium-iron-boron sintered permanent magnet has higher magnet performance, and the application of the cerium-containing neodymium-iron-boron sintered permanent magnet in the market is effectively widened.
One object of the invention is achieved by the following technical scheme:
the sintered permanent magnet includes alloy one and alloy two, and the chemical molecular formula of alloy one is [ (Pr) x2 Nd 1-x1-x2 RL x1 ] a M1 b M2 c B d Fe 100-a-b-c-d 0 < x1 is less than or equal to 0.4,0 < x2 is less than or equal to 0.2, 28.5 is less than or equal to a is less than or equal to 30,0 < b is less than or equal to 3,0 < c is less than or equal to 0.8,0.85 is less than or equal to d is less than or equal to 0.95, wherein RL is one or two of La and Ce, M1 is one or more of Al, cu, ga, co, mn, and M2 is one or more of Nb, zr, hf, ti, V; the chemical molecular formula of the alloy II is Pr a1 Ce b1 Ga c1 Fe 100-a1-b1-c1 ，50≤a1+b1≤70，1≤b1/a1≤2，5≤c1≤10。
Preferably, the grain boundary of the cerium-containing neodymium-iron-boron sintered permanent magnet comprises RFe 2 Phase, R 6 Fe 13 Ga phase and R-rich phase, wherein R is Pr, nd and Ce.
Preferably, the mass percentages of the alloy I and the alloy II are 92-95 wt% and 5-8 wt%, respectively.
The second object of the invention is achieved by the following technical scheme:
the preparation method of the cerium-containing neodymium-iron-boron sintered permanent magnet comprises the following steps:
s1, preparing raw materials according to a chemical molecular formula of an alloy I, and smelting and casting the raw materials of the alloy I to obtain an alloy I sheet;
s2, preparing raw materials according to the chemical molecular formula of the alloy II, smelting and casting the raw materials of the alloy II to obtain an alloy II ingot, and carrying out homogenization treatment on the alloy II ingot;
s3, absorbing hydrogen from the alloy sheet and crushing the alloy sheet into alloy coarse powder, carrying out first dehydrogenation treatment, and then carrying out a first air stream grinding process to obtain alloy fine powder; absorbing hydrogen to the homogenized alloy two ingots, crushing the alloy two ingots into alloy two coarse powder, carrying out second dehydrogenation treatment, and carrying out a second air flow grinding process to obtain alloy two fine powder;
s4, uniformly mixing the alloy primary fine powder and the alloy secondary fine powder to form mixed powder, performing orientation molding, and performing isostatic pressing treatment after vacuum packaging;
and S5, sintering the magnet obtained through isostatic pressing treatment, and then performing aging treatment to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
Preferably, the smelting temperature of the step S1 is 1440-1470 ℃, the casting temperature is 1420-1450 ℃, and the thickness of the alloy sheet is 0.2-0.35 mm.
Preferably, the smelting temperature of step S2 is 1460-1485℃and the casting temperature is 1440-1465 ℃.
Preferably, the homogenization treatment temperature in step S2 is 900-1000 ℃ and the homogenization treatment time is 4-8 hours. The uniformity treatment of the alloy two cast ingots can effectively improve the grain size and component uniformity, provides a basis for preparing fine powder with good uniformity for the subsequent air flow mill, ensures that the grain boundary phase can better wrap the main phase grains after the alloy powder is doped, improves the distribution uniformity of the grain boundary phase, and is beneficial to forming uniformly distributed RFe 2 Phase and R 6 Fe 13 Ga phase.
Preferably, the average particle size of the alloy one meal and the alloy two meal are 20 to 200 μm respectively.
Preferably, the temperature of the first dehydrogenation treatment is 450-600 ℃ and the time is 100-500 min; the temperature of the second dehydrogenation treatment is 300-440 ℃ and the time is 100-500 min. Because the rare earth content of the alloy II is high and is easy to oxidize, the residual hydrogen content of the powder is improved by reducing the dehydrogenation temperature of the alloy II, and the oxidation resistance of the alloy II powder is improved.
Preferably, after dehydrogenation treatment and before the air flow grinding process, antioxidant is added into the coarse powder, and the air flow grinding process is carried out after stirring for 0.5-5 h.
Preferably, the antioxidant is added in an amount of 0.01 to 0.1wt% based on the mass of the coarse powder. The average particle size of the antioxidant is 1-50 mu m.
The antioxidant is zinc stearate, glycerol, etc.
Preferably, in the first air flow grinding process, the rotating speed of an air flow grinding sorting wheel is 2500-4000 r/min, the air flow grinding time is 1-5 h, and the surface area average particle Size (SMD) of alloy-fine powder is controlled to be 2.5-3.5 mu m; in the second air flow grinding process, the rotating speed of a sorting wheel of the air flow mill is 900-1100 r/min, and the air flow grinding time is 1-5 h. The surface area average particle Size (SMD) of the alloy two fine powder is controlled to be 3-4 mu m. Because the total amount of rare earth of the alloy II is high and is easy to oxidize, the alloy II powder is too fine and is easy to oxidize due to the too high rotating speed of the air flow mill sorting wheel, the magnetic property is poor, the powder granularity is too coarse due to the too low rotating speed, the grain boundary phase cannot be uniformly distributed around grains, and the grain boundary reconstruction modification is influenced.
Preferably, in the mixed powder in the step S4, the mass percentages of the alloy primary fine powder and the alloy secondary fine powder are 92-95 wt% and 5-8 wt%, respectively.
Preferably, the antioxidant and gasoline are added into the mixed powder to be stirred for 2 to 6 hours, and then the mixed powder is subjected to orientation molding.
More preferably, the addition amount of the antioxidant is 0.02-0.1 wt% of the mass of the mixed powder, and the addition amount of the gasoline is 0.02-0.06 wt% of the mass of the mixed powder.
Preferably, the orientation molding is performed under an inert gas atmosphere in a magnetic field of 1.5 to 2.2T.
Preferably, the pressure of the isostatic pressing treatment is 50-200 Mpa and the dwell time is 10-60 s.
Preferably, the sintering is vacuum sintering, the sintering temperature is 1000-1200 ℃, and the sintering time is 3-10 h.
Preferably, the aging treatment comprises: treating at 800-950 deg.c for 2-5 hr and then at 400-600 deg.c for 3-8 hr. And (5) air cooling to room temperature after aging treatment.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention adopts cerium-containing light rare earth alloy doping to improve the coercive force of the cerium-containing neodymium iron boron sintered permanent magnet, utilizes the characteristic of low melting point of the cerium-containing light rare earth alloy, is easier to wrap in main phase grains in the sintering process, forms a continuous and uniform grain boundary phase while inhibiting the growth of the grains, and reduces the ferromagnetism of the grain boundary phase according to the non-ferromagnetic characteristic of the grain boundary phase, thereby effectively improving the coercive force of the magnet.
(2) The grain boundary of the cerium-containing neodymium-iron-boron sintered permanent magnet provided by the invention comprises RFe 2 Phase, R 6 Fe 13 Ga phase and R-rich phase, wherein R is Pr, nd and Ce.
(3) According to the invention, through the alloy powder doping and combining preparation process, the magnet grain boundary phase is subjected to reconstruction modification, three grain boundary phases are formed at the grain boundary, the effect of exchange coupling removal is effectively achieved, the hard magnetization of the surface of the magnet crystal grain is realized, the coercive force of the magnet can be effectively improved, and the application of the magnet in the market is widened.
(4) The invention effectively solves the problems that the doped alloy powder with higher total rare earth amount is easy to oxidize and the magnetic performance is influenced by combining the processes of hydrogen breaking temperature, air mill separation wheel rotating speed, antioxidant addition and the like.
(5) The invention can effectively improve the grain size and component uniformity of the auxiliary phase ingot alloy by carrying out homogenization treatment, and has certain reference significance for alloy powder doping and grain boundary diffusion infiltration source preparation.
Drawings
Fig. 1 is a schematic diagram of SEM images and EPMA point scans of the magnets of example 1 and comparative example 1, wherein (a) is a schematic diagram of SEM images and EPMA point scans of the magnets of example 1, and (b) is a schematic diagram of SEM images and EPMA point scans of the magnets of comparative example 1.
Fig. 2 is a schematic diagram of SEM images and EPMA point scans of the magnets of comparative example 3 and comparative example 5, wherein (a) is a schematic diagram of SEM images and EPMA point scans of the magnet of comparative example 3, and (b) is a schematic diagram of SEM images and EPMA point scans of the magnet of comparative example 5.
Detailed Description
The technical solution of the present invention will be further described by means of specific examples and drawings, it being understood that the specific examples described herein are only for aiding in understanding the present invention and are not intended to be limiting. And the drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure. Unless otherwise indicated, all materials used in the examples of the present invention are those commonly used in the art, and all methods used in the examples are those commonly used in the art.
Example 1
The preparation method of the cerium-containing neodymium-iron-boron sintered permanent magnet comprises the following steps:
s1, nd1 17.2 Pr 4.3 Ce 8 Al 0.6 Cu 0.15 Zr 0.2 Co 0.5 B 0.95 Fe 68.1 Smelting each metal element at 1460 ℃, casting the metal element on a copper roller at 1440 ℃ to obtain an alloy sheet with the thickness of 0.2-0.35 mm;
s2 according to Pr 25 Ce 30 Ga 8 Fe 37 Smelting each metal element at 1480 ℃ and casting at 1460 ℃ to obtain an alloy two-ingot, heating the alloy two-ingot to 950 ℃ and carrying out homogenization heat treatment for 6h (950 ℃ is 6 h);
s3, hydrogen absorption and crushing of an alloy sheet into alloy coarse powder (the average particle size is about 150 mu m), adding zinc stearate powder with the average particle size of 5 mu m, which is 0.05wt% of the mass of the coarse powder, into the alloy coarse powder after first dehydrogenation treatment (550 ℃ for 300 min), stirring for 1h, and obtaining alloy fine powder (SMD is 3.1 mu m) through a first air flow grinding process (the rotating speed of a sorting wheel is 3000r/min,3 h); the homogenized alloy two-ingot is crushed into alloy two-coarse powder (the average grain diameter is about 170 mu m) by absorbing hydrogen, zinc stearate powder with the average grain diameter of 5 mu m, the weight of which is 0.05 percent of the mass of the coarse powder, is added after the second dehydrogenation treatment (400 ℃ and 300 min), and is stirred for 1h, and then alloy two-fine powder (SMD is 3.5 mu m) is obtained through a second air-stream grinding process (the rotating speed of a sorting wheel is 1000r/min and 3 h);
s4, uniformly mixing 94wt% of alloy primary fine powder and 6wt% of alloy secondary fine powder to form mixed powder, adding zinc stearate accounting for 0.05wt% of the mixed powder and gasoline accounting for 0.04wt% of the mixed powder into the mixed powder, stirring for 3 hours, carrying out orientation molding on the mixed powder in a magnetic field of 1.8T under the protection of nitrogen, and carrying out isostatic pressing treatment (180 Mpa and 22S for pressure maintaining) after vacuum packaging;
s5, sintering the magnet obtained through isostatic pressing at 1065 ℃ for 5 hours under vacuum, then aging at 900 ℃ for 2.5 hours, aging at 485 ℃ for 4.5 hours, and introducing argon gas for air cooling to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
Example 2
The preparation method of the cerium-containing neodymium-iron-boron sintered permanent magnet comprises the following steps:
s1, nd 14.8 Pr 3.7 Ce 10 Al 0.4 Cu 0.15 Zr 0.3 Co 0.5 B 0.95 Fe 69.2 Smelting each metal element at 1450 ℃, casting the metal element on a copper roller at 1430 ℃ to obtain an alloy sheet with the thickness of 0.2-0.35 mm;
s2 according to Pr 25 Ce 30 Ga 8 Fe 37 Smelting each metal element at 1470 ℃, casting at 1450 ℃ to obtain an alloy two cast ingot, heating the alloy two cast ingot to 980 ℃ and carrying out homogenization heat treatment for 5h (980 ℃ for 5 h);
s3, hydrogen absorption and crushing of an alloy sheet into alloy coarse powder (the average particle size is about 160 mu m), adding zinc stearate powder with the average particle size of 5 mu m, wherein the weight of the zinc stearate powder is 0.06wt% of the mass of the coarse powder after first dehydrogenation treatment (520 ℃ for 300 min), stirring for 2h, and obtaining alloy fine powder (SMD is 3.2 mu m) through a first air flow grinding process (the rotating speed of a sorting wheel is 2800r/min and 3 h); the homogenized alloy two-ingot is crushed into alloy two-coarse powder (average particle size is about 170 mu m), zinc stearate powder with average particle size of 5 mu m, which is 0.06wt% of the mass of the coarse powder, is added after the second dehydrogenation treatment (380 ℃ for 300 min), and is stirred for 2h, and then alloy two-fine powder (SMD is 3.6 mu m) is obtained through a second air-stream grinding process (the rotating speed of a sorting wheel is 950r/min,3 h);
s4, uniformly mixing 93wt% of alloy primary fine powder and 7wt% of alloy secondary fine powder to form mixed powder, adding zinc stearate accounting for 0.06wt% of the mixed powder and gasoline accounting for 0.03wt% of the mixed powder into the mixed powder, stirring for 4 hours, carrying out orientation molding on the mixed powder in a magnetic field of 2.0T under the protection of nitrogen, and carrying out isostatic pressing treatment (200 Mpa and pressure maintaining for 20S) after vacuum packaging;
s5, sintering the magnet obtained through isostatic pressing treatment for 4.5 hours at 1080 ℃ under vacuum, then aging for 3 hours at 880 ℃, aging for 5 hours at 460 ℃, and introducing argon for air cooling to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
Example 3
Example 3 differs from example 1 only in that 92wt% of the alloy primary fine powder and 8wt% of the alloy secondary fine powder were uniformly mixed to form a mixed powder in step S4 of example 3. The other steps are the same as in example 1.
Example 4
Example 4 differs from example 2 only in that 95wt% of the alloy primary fine powder and 5wt% of the alloy secondary fine powder were uniformly mixed to form a mixed powder in step S4 of example 3. The other steps are the same as in example 2.
Comparative example 1
The preparation method of the cerium-containing neodymium-iron-boron sintered permanent magnet of the comparative example 1 comprises the following steps:
s1, nd 16.2 Pr 5.5 Ce 9.3 Al 0.56 Cu 0.14 Zr 0.19 Co 0.47 Ga 0.48 B 0.89 Fe 66.27 Smelting each metal element at 1460 ℃, casting the metal element on a copper roller at 1440 ℃ to obtain an alloy sheet with the thickness of 0.2-0.35 mm;
s2, hydrogen absorption and crushing of alloy flakes into alloy coarse powder (the average particle size is about 150 mu m), after dehydrogenation treatment (550 ℃ for 300 min), adding zinc stearate powder with the average particle size of 5 mu m, wherein the weight of the zinc stearate powder is 0.05wt% of the mass of the coarse powder, stirring for 1h, and then obtaining alloy fine powder (SMD is 3.1 mu m) through an air flow grinding process (the rotating speed of a sorting wheel is 3000r/min,3 h);
s3, zinc stearate accounting for 0.05 weight percent of the fine powder mass and gasoline accounting for 0.04 weight percent of the fine powder mass are added into the alloy fine powder and stirred for 3 hours, the mixed powder is oriented and molded in a magnetic field of 1.8T under the protection of nitrogen, and isostatic pressing treatment (180 Mpa, pressure maintaining for 22S) is carried out after vacuum packaging;
and S4, sintering the magnet obtained through isostatic pressing at 1065 ℃ for 5 hours under vacuum, then aging at 900 ℃ for 2.5 hours, aging at 485 ℃ for 4.5 hours, and introducing argon gas for air cooling to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
Comparative example 2
The preparation method of the cerium-containing neodymium-iron-boron sintered permanent magnet of comparative example 2 comprises the following steps:
s1, toNd 13.8 Pr 5.5 Ce 12.1 Al 0.37 Cu 0.14 Zr 0.28 Co 0.47 Ga 0.35 B 0.88 Fe 66.11 Smelting each metal element at 1450 ℃, casting the metal element on a copper roller at 1430 ℃ to obtain an alloy sheet with the thickness of 0.2-0.35 mm;
s2, hydrogen absorption and crushing of alloy flakes into alloy coarse powder (the average particle size is about 160 mu m), dehydrogenation treatment (520 ℃ for 300 min), adding zinc stearate powder with the average particle size of 5 mu m, wherein the weight of the zinc stearate powder is 0.06wt% of the mass of the coarse powder, stirring for 2h, and then obtaining alloy fine powder (SMD is 3.2 mu m) through an air flow grinding process (the rotating speed of a sorting wheel is 2800r/min,3 h);
s3, zinc stearate accounting for 0.06 weight percent of the fine powder mass and gasoline accounting for 0.03 weight percent of the fine powder mass are added into the alloy fine powder and stirred for 4 hours, the mixed powder is oriented and molded in a magnetic field of 2.0T under the protection of nitrogen, and isostatic pressing treatment (200 Mpa, pressure maintaining for 20S) is carried out after vacuum packaging;
and S4, sintering the magnet obtained by isostatic pressing treatment for 4.5 hours at 1080 ℃ under vacuum, then aging for 3 hours at 880 ℃, aging for 5 hours at 460 ℃, and introducing argon for air cooling to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
Comparative example 3
Comparative example 3 differs from example 1 in that the alloy of comparative example 3 has a composition Nd 17.2 Pr 2.3 Ce 9.9 Al 0.6 Cu 0.1 5 Zr 0.2 Co 0.5 B 0.95 Fe 68.2 The alloy two components are Pr 55 Ga 8 Fe 37 The other steps are the same as in example 1.
Comparative example 4
Comparative example 4 differs from example 1 in that the alloy of comparative example 4 has a binary Pr 55 Ga 8 Fe 37 The other steps are the same as in example 1.
Comparative example 5
Comparative example 5 differs from example 1 in that the alloy of comparative example 5 has Nd as one component 17.2 Pr 5.3 Ce 7 Al 0.6 Cu 0.15 Zr 0.2 Co 0.5 B 0.95 Fe 68.1 Alloy IIThe component is Pr 10 Ce 45 Ga 8 Fe 37 The other steps are the same as in example 1.
Comparative example 6
Comparative example 6 differs from example 1 in that the alloy of comparative example 6 has a binary Pr 10 Ce 45 Ga 8 Fe 37 The other steps are the same as in example 1.
Comparative example 7
Comparative example 7 differs from example 1 in that the alloy of comparative example 7 has a composition Nd 16.5 Pr 5.15 Ce 8.9 Al 0.58 Cu 0.14 Zr 0.19 Co 0.48 Ga 0.33 B 0.91 Fe 66.82 The mixing proportion of the alloy primary fine powder and the alloy secondary fine powder is 98 percent: 2, the other steps are the same as in example 1.
Comparative example 8
Comparative example 8 differs from example 1 in that the alloy primary powder and alloy secondary powder were mixed in a powder mixing ratio of 98%:2, the other steps are the same as in example 1.
Comparative example 9
Comparative example 9 differs from example 1 in that the alloy of comparative example 9 has a composition Nd 18 Pr 3.5 Ce 7 Al 0.6 Cu 0.16 Zr 0.2 Co 0.5 B 0.98 Fe 69.06 The mixing proportion of the alloy I and alloy II fine powder is 90 percent: 10. Other steps are the same as in example 1.
Comparative example 10
Comparative example 10 differs from example 1 in that the alloy primary powder and alloy secondary powder were mixed in a powder mixing ratio of 90%: 10. Other steps are the same as in example 1.
Comparative example 11
The alloy two ingot stock homogenization heat treatment process of comparative example 11 was 950 ℃ for 2 hours, with the other steps being the same as in example 1.
Comparative example 12
The alloy two ingot stock homogenization heat treatment process of comparative example 12 was 950 ℃ for 10 hours, and the other steps were the same as in example 1.
Comparative example 13
The alloy two ingot stock homogenization heat treatment process of comparative example 13 was 800 ℃ for 6 hours, and the other steps were the same as in example 1.
Comparative example 14
The alloy two ingot stock homogenization heat treatment process of comparative example 14 was 800 ℃ for 10 hours, and the other steps were the same as in example 1.
Comparative example 15
The alloy two ingot stock homogenization heat treatment process of comparative example 15 was 1050 ℃ for 4 hours, and the other steps were the same as in example 1.
Comparative example 16
The alloy two ingot stock homogenization heat treatment process of comparative example 16 was 1050 ℃ for 6 hours, and the other steps were the same as in example 1.
Preparing a magnetic property measurement sample by adopting a linear cutting, coreless grinding and end face grinding method, wherein the sample isThe magnetic properties of the sintered NdFeB magnets prepared in examples and comparative examples were obtained by testing the cylinders at room temperature of 20℃using NIM-62000 demagnetization curve testing equipment, and the test results are shown in Table 1.
TABLE 1
Comparative example 1 differs from example 1 in that comparative example 1 employs a single alloy; comparative example 2 differs from example 2 in that comparative example 2 employs a single alloy. As can be seen from comparative examples 1 and 1, and comparative examples 2 and 2, the coercivity of magnets prepared with alloy powder doping was significantly higher than that of single alloys.
The sintered neodymium-iron-boron magnets obtained in example 1 and comparative example 1 were observed for their microstructure by SEM, and the results are shown in fig. 1 (a) and 1 (b). The SEM images of fig. 1 (a) and 1 (b) were subjected to a point scan schematic diagram, and the composition mass ratios are shown in table 2:
TABLE 2
As can be seen from the data in Table 2, the grain boundary phase distribution in example 1 is more uniform and clear than that in comparative example 1, and neither Ga nor Ce elements in comparative example 1 are effective nor Fe element is formed (CePrNd) 6 Fe 13 Ga phase, (CePrNd) Fe 2 The Ga element enters the main phase more easily, and Ce and PrNd are aggregated to form an R-rich phase more easily. Example 1 can effectively solve the problem, the two phases formed are uniformly distributed in the grain boundary, the coupling effect between grains can be effectively inhibited, and the coercive force of the magnet is improved. And the Pr/Nd content ratio in the grain boundary of example 1 is significantly higher than that in comparative example 1, indicating that Pr in the doped powder effectively enters the grain boundary phase.
The sintered neodymium-iron-boron magnets obtained in comparative examples 3 and 5 were observed for the microstructure of the magnets by SEM, and the results are shown in fig. 2 (a) and 2 (b). The SEM images of fig. 2 (a) and 2 (b) were subjected to a point scan schematic diagram, and the composition mass ratios are shown in table 3:
as can be seen from the data in Table 2, the Ce/Pr ratio in alloy two is too low and the grain boundary is not effective to form (CePrNd) Fe 2 Phase, resulting in a substantial decrease in coercivity; if the Ce/Pr ratio in alloy II is too high, there will be (CePrNd) Fe 2 Phase formation, but R 6 Fe 13 The Ce content in the Ga grain boundary phase is higher than the total rare earth content, because Ce 6 Fe 13 Ga vs Pr 6 Fe 13 Ga is distributed in grain boundaries to have poor effect of inhibiting coupling effect on grains, so that coercivity is reduced, but the reduction amplitude of the overall coercivity is smaller when the Ce/Pr ratio of the doped powder is lower.
Comparative example 1, comparative examples 7-10, the alloy two-doping ratio was too low to form (CePrNd) Fe efficiently at the grain boundary 2 And R is 6 Fe 13 Ga phase, and therefore coercive force is not significantly improved over single alloy. The alloy II has too high doping ratio, so that the aggregation condition of a grain boundary phase is obvious, a certain ferromagnetic phase exists in the grain boundary, the coercivity of the magnet is reduced, and meanwhile, the squareness is also deteriorated.
In comparative example 1 and comparative examples 11 to 16, the homogenization heat treatment temperature was too low or the time was too short, and the homogenization effect deviation of the alloy grain size was caused, resulting in uneven grain size of the fine powder after air flow grinding, affecting the grain boundary phase flow during sintering, and failing to uniformly wrap around the grains, thereby resulting in deterioration of coercive force and squareness. The heat treatment temperature is too high or the time is too long, the condition of grain growth can appear, the uniformity of powder granularity after air flow grinding is also influenced, the grain boundary phase is easier to gather in the sintering process, and the coercivity is reduced and the squareness is poor.
The various aspects, embodiments, features of the invention are to be considered as illustrative in all respects and not restrictive, the scope of the invention being indicated only by the appended claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
In the preparation method of the invention, the sequence of each step is not limited to the listed sequence, and the sequential change of each step is also within the protection scope of the invention without the inventive labor for the person skilled in the art. Furthermore, two or more steps or actions may be performed simultaneously.
Finally, it should be noted that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention's embodiments. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions in a similar manner, and need not and cannot fully practice all of the embodiments. While these obvious variations and modifications, which come within the spirit of the invention, are within the scope of the invention, they are to be construed as being without departing from the spirit of the invention.
Claims (10)
1. The preparation raw materials of the cerium-containing neodymium-iron-boron sintered permanent magnet comprise an alloy I and an alloy II, wherein the chemical molecular formula of the alloy I is [ (Pr) x2 Nd 1-x1-x2 RL x1 ] a M1 b M2 c B d Fe 100-a-b-c-d 0 < x1 is less than or equal to 0.4,0 < x2 is less than or equal to 0.2, 28.5 is less than or equal to a is less than or equal to 30,0 < b is less than or equal to 3,0 < c is less than or equal to 0.8,0.85 is less than or equal to d is less than or equal to 0.95, wherein RL is one or two of La and Ce, M1 is one or more of Al, cu, ga, co, mn, and M2 is one or more of Nb, zr, hf, ti, V; the chemical molecular formula of the alloy II is Pr a1 Ce b1 Ga c1 Fe 100-a1-b1-c1 ，50≤a1+b1≤70，1≤b1/a1≤2，5≤c1≤10。
2. The sintered permanent magnet of claim 1 wherein the grain boundaries of the sintered permanent magnet comprise RFe 2 Phase, R 6 Fe 13 Ga phase and R-rich phase, wherein R is Pr, nd and Ce.
3. The cerium-containing neodymium-iron-boron sintered permanent magnet according to claim 1, wherein the mass percentages of the alloy one and the alloy two are 92-95 wt% and 5-8 wt%, respectively.
4. The method for preparing the cerium-containing neodymium-iron-boron sintered permanent magnet according to claim 1, which comprises the following steps:
s1, preparing raw materials according to a chemical molecular formula of an alloy I, and smelting and casting the raw materials of the alloy I to obtain an alloy I sheet;
s2, preparing raw materials according to the chemical molecular formula of the alloy II, smelting and casting the raw materials of the alloy II to obtain an alloy II ingot, and carrying out homogenization treatment on the alloy II ingot;
s3, absorbing hydrogen from the alloy sheet and crushing the alloy sheet into alloy coarse powder, carrying out first dehydrogenation treatment, and then carrying out a first air stream grinding process to obtain alloy fine powder; absorbing hydrogen to the homogenized alloy two ingots, crushing the alloy two ingots into alloy two coarse powder, carrying out second dehydrogenation treatment, and carrying out a second air flow grinding process to obtain alloy two fine powder;
s4, uniformly mixing the alloy primary fine powder and the alloy secondary fine powder to form mixed powder, performing orientation molding, and performing isostatic pressing treatment after vacuum packaging;
and S5, sintering the magnet obtained through isostatic pressing treatment, and then performing aging treatment to obtain the cerium-containing neodymium-iron-boron sintered permanent magnet.
5. The method according to claim 4, wherein the melting temperature in the step S1 is 1440-1470 ℃, the casting temperature is 1420-1450 ℃, and the thickness of the alloy sheet is 0.2-0.35 mm;
the smelting temperature of the step S2 is 1460-1485 ℃ and the casting temperature is 1440-1465 ℃.
6. The method according to claim 4, wherein the homogenization treatment temperature in step S2 is 900 to 1000℃and the homogenization treatment time is 4 to 8 hours.
7. The method according to claim 4, wherein the first dehydrogenation treatment is carried out at a temperature of 450 to 600℃for a period of 100 to 500 minutes; the temperature of the second dehydrogenation treatment is 300-440 ℃ and the time is 100-500 min;
in the first air flow grinding process, the rotating speed of a sorting wheel of the air flow mill is 2500-4000 r/min, the air flow grinding time is 1-5 h, and the average surface area granularity of alloy fine powder is controlled to be 2.5-3.5 mu m;
in the second air flow grinding process, the rotating speed of a sorting wheel of the air flow mill is 900-1100 r/min, and the air flow grinding time is 1-5 h. The surface area average particle size of the alloy fine powder is controlled to be 3-4 mu m.
8. The method according to claim 4, wherein the mass percentages of the alloy primary fine powder and the alloy secondary fine powder in the mixed powder in the step S4 are 92-95 wt% and 5-8 wt%, respectively.
9. The process according to claim 4, wherein the orientation molding is carried out under an inert gas atmosphere in a magnetic field of 1.5 to 2.2T, the isostatic pressure is 50 to 200MPa, and the dwell time is 10 to 60s.
10. The preparation method according to claim 4, wherein the sintering is vacuum sintering, the sintering temperature is 1000-1200 ℃, and the sintering time is 3-10 hours;
the aging treatment comprises the following steps: treating at 800-950 deg.c for 2-5 hr and then at 400-600 deg.c for 3-8 hr. And (5) air cooling to room temperature after aging treatment.
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