CN115862985A - Corrosion-resistant permanent magnet material and preparation method thereof - Google Patents
Corrosion-resistant permanent magnet material and preparation method thereof Download PDFInfo
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Abstract
The application relates to a corrosion-resistant permanent magnet material and a preparation method thereof, wherein the corrosion-resistant permanent magnet material comprises the following raw materials: 95 to 98 percent of main phase alloy and 2 to 5 percent of grain boundary alloy; the total amount of the main phase alloy and the grain boundary alloy is 100 percent; the alloy also comprises an auxiliary alloy, and the addition amount of the auxiliary alloy is 0.3 to 0.8 percent of the total amount of the main phase alloy and the grain boundary alloy. According to the method, the main phase alloy and the grain boundary alloy are separated to prepare the thin strip and then sintered, so that the grain boundary alloy can be greatly reduced from entering the main phase, the rare earth elements in the grain boundary alloy mainly form a shell layer rich in heavy rare earth at the edge of the main phase grain, and the non-rare earth elements mainly exist in a dispersed phase form.
Description
Technical Field
The application relates to the technical field of magnetic materials, in particular to a corrosion-resistant permanent magnetic material and a preparation method thereof.
Background
The Nd-Fe-B based permanent magnetic RE material is the third generation permanent magnetic RE material with strongest magnetism and wide application. At present, the neodymium-iron-boron based rare earth permanent magnetic material becomes one of indispensable materials in emerging fields of information, energy, medical treatment, traffic, national defense and the like. With the popularization of the application range of the rare earth permanent magnet material, the using environment is more and more complex, so that new requirements on corrosion resistance and high temperature resistance are provided.
Although the neodymium-iron-boron-based rare earth permanent magnet material has better comprehensive magnetic property, the coercive force is not high, so that the neodymium-iron-boron-based rare earth permanent magnet material has a serious thermal demagnetization phenomenon in a high-temperature environment and the service life of the neodymium-iron-boron-based rare earth permanent magnet material is seriously influenced. At present, the most common method is to improve the temperature resistance by adding heavy rare earth elements, but the heavy rare earth elements can partially replace Nd in the main phase, so that the magnetic property of the heavy rare earth elements is obviously reduced.
In the Nd-Fe-B based rare earth permanent magnet material, because Nd elements in Nd-rich phases are very active and are easy to react with oxygen and water in air, so that corrosion occurs, the difference between the electrode potential of the Nd-rich phases and the electrode potential of a main phase is large, a primary battery is very easy to form in a corrosive environment, electrochemical corrosion occurs, corrosion of a magnet is accelerated, and finally crystal grains of the main phase of the magnet fall off and the magnet is pulverized. At present, the main method for improving the corrosion resistance of the neodymium-iron-boron-based rare earth permanent magnet material is to prepare an anticorrosive coating, but the preparation process of the anticorrosive coating is complex, and the binding strength of the anticorrosive coating and a magnet is not enough, so the anticorrosive coating is easy to fall off, and the corrosion resistance is limited.
In view of the above-mentioned related art, the inventors believe that neodymium-iron-boron based rare earth permanent magnetic materials have the defect of insufficient high temperature resistance and corrosion resistance.
Disclosure of Invention
In order to improve the corrosion resistance and high temperature resistance of the permanent magnet material, the application provides the corrosion-resistant permanent magnet material and the preparation method thereof.
In a first aspect, the present application provides a corrosion-resistant permanent magnetic material, which adopts the following technical scheme:
a corrosion-resistant permanent magnetic material comprises the following raw materials: 95-98% of main phase alloy and 2-5% of grain boundary alloy; the total amount of the main phase alloy and the grain boundary alloy is 100 percent; the alloy also comprises an auxiliary alloy, and the addition amount of the auxiliary alloy is 0.3-0.8% of the total amount of the main phase alloy and the grain boundary alloy;
wherein: the main phase alloy comprises the following components in percentage by mass: (64-68), 27-31, (0.92-1.02), (0.33-0.36), (0.05-0.15) and (0.05-0.15) Fe, prNd, B, al, ti and Ni;
the grain boundary alloy comprises the following components in percentage by mass: dy, co, ga and Cu of (1.1-2.0), (0.8-1.5), (0.1-0.3) and (0.1-0.2);
the auxiliary alloy is MgZn alloy.
By adopting the technical scheme, the raw material components are divided into 3 types according to the performance, and the main phase alloy mainly constructs a rare earth-rich phase and a main phase; then introducing a grain boundary alloy, and preparing the crystal alloy phase powder and the main phase alloy powder separately, wherein the separate preparation is mainly used for avoiding that elements in the grain boundary alloy replace elements in the main phase, so that the magnetic property is obviously reduced. The heavy rare earth element Dy prepared by separating the two kinds of powder can not enter the main phase to cause antiferromagnetic coupling but can be diffused to the surface of the main phase grains along the grain boundary phase, and a shell layer rich in heavy rare earth is formed at the edge of the main phase grains, and the heavy rare earth shell layer can enhance the anisotropy of local magnetocrystalline, so that the coercive force of the magnet is optimized, but the magnetic performance is not obviously reduced. The introduction of Gd in the grain boundary alloy can form a non-ferromagnetic grain boundary phase Nd at the grain boundary phase 6 Fe 13 Ga can not only improve the coercive force of the magnet, but also improve the wettability of the rare earth-rich phase; the coercive force of the magnet can be further improved by the synergistic effect of the rare earth elements Dy and Ga. Cu and Co in the grain boundary alloy can not enter the main phase, but form a dispersed phase at the grain boundary, and the existence of the dispersed phase can reduce the potential difference between the main phase and the rare earth-rich phase, thereby improving the corrosion resistance of the magnet.
The method also introduces an auxiliary alloy, wherein the auxiliary alloy mainly adopts a low-melting-point MgZn alloy; mainly because the main phase alloy and the grain boundary alloy are prepared separately; in order to improve the diffusion properties of the grain boundary alloy, an auxiliary alloy is used. The low-melting-point auxiliary alloy can form a solid solution with the grain boundary alloy, so that the diffusivity of the grain boundary alloy can be improved, the auxiliary metal can form a dispersed phase in the diffusion process and surround the main phase, and the grain boundary phase is prevented from entering the main phase. Meanwhile, the auxiliary alloy is volatilized in the sintering process due to the low boiling point, so that the residual quantity in the magnet is low, and a small amount of residual metal is mainly dispersed and distributed at a crystal boundary, so that the potential difference between a main phase and a rare earth-rich phase can be reduced, and the corrosion resistance is improved; and the auxiliary alloy has high reducibility, so that the oxidation of other metals in the sintering process can be reduced, and the stability of the permanent magnet is further improved.
Preferably, the alloy comprises 97.35% of main phase alloy, 2.65% of grain boundary alloy; the addition amount of the auxiliary alloy is 0.5 percent of the total amount of the main phase alloy and the grain boundary alloy; wherein: the main phase alloy comprises the following components in percentage by mass: 66.82;
the grain boundary alloy comprises the following components in percentage by mass: 1.30 Dy, co, ga and Cu; the auxiliary alloy is a 60.
By adopting the technical scheme, the comprehensive performance of the permanent magnet can be further improved by further controlling the proportion of each component.
In a second aspect, the present application provides a method for preparing a corrosion-resistant permanent magnetic material, which adopts the following technical scheme:
a preparation method of the corrosion-resistant permanent magnet material comprises the following steps:
s1, proportioning a main phase alloy and a grain boundary alloy according to a proportion, respectively adding the main phase alloy and the grain boundary alloy into a vacuum induction furnace, carrying out vacuum melting, and after the melting is finished, respectively preparing a main phase alloy thin strip and a grain boundary alloy thin strip from an alloy liquid solution by a rapid hardening strip throwing process;
s2: respectively carrying out hydrogen crushing on the main phase alloy thin strip and the grain boundary alloy thin strip, mechanically crushing the auxiliary alloy to respectively obtain corresponding coarse powder, then mixing the three coarse powders according to a ratio, and carrying out jet milling to obtain mixed powder;
s3: adding a lubricant into the mixed powder in the step S3, and uniformly mixing to obtain a mixture; pressing the mixture into a blank by a magnetic field press, then placing the vacuum-packaged blank into a cold isostatic pressing mold, and further pressing to obtain a blank body;
s4: carrying out four-stage temperature vacuum sintering on the green body, obtaining a sintered blank after sintering, further carrying out aging treatment on the sintered blank to obtain the corrosion-resistant permanent magnet material,
by adopting the technical scheme, the green body is subjected to multi-stage vacuum sintering, the first stage sintering temperature is mainly used for removing the lubricant in the green body, and the second stage vacuum sintering is mainly used for enabling the auxiliary alloy and the grain boundary alloy to generate solid solution so as to form a solid solution phase; the third stage of sintering is mainly used for enabling solid solution phase and main phase alloy to be diffused, and the fourth stage of sintering temperature is mainly used for removing auxiliary alloy components; by the action of multi-stage vacuum sintering, the reduction of magnetic performance caused by the replacement of elements in the main phase by the grain boundary alloy can be reduced.
Preferably, in the step S1, the vacuum melting temperature is 1200-1600 ℃, and the melting time is 7-10 min.
By adopting the technical scheme, the components can be uniformly mixed by controlling the smelting temperature and time, so that uniform alloy sheets can be better formed.
Preferably, in the step S1, in the rapid hardening and strip casting process, the rotation speed of the water-cooled copper roller is 0.8 to 4.0m/S, the cooling rate is 150 to 200 ℃/S, and the thickness of the sheet is 0.2 to 0.4mm.
By adopting the technical scheme, the alloy solution after smelting can be rapidly cooled to room temperature by the rapid hardening strip-spinning process, so that the growth of crystal grains can be effectively inhibited, and the magnetic performance of the magnet is improved; and the hydrogen is easier to crush by preparing the raw materials into slices, so that the crushing efficiency is improved.
Preferably, in step S2, the specific process of hydrogen fragmentation is as follows: placing the thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing hydrogen until the pressure in the furnace reaches 10 2 ～10 3 Pa above, the hydrogen pressure is continuously reduced along with the crushing of the thin strip in hydrogen absorption reaction, and hydrogen needs to be introduced to maintain the hydrogen pressure stable; the grain diameter of the coarse powder after hydrogen crushing or mechanical crushing needs to be controlled between 60 and 100um; the particle size of the powder after the jet milling needs to be controlled between 2.5 and 5um.
By adopting the technical scheme, the hydrogen crushing is mainly adopted for the thin strip in the application so as to ensure that the thin strip is subjected to crystal-along fracture and crystal-through fracture; the hardness of the auxiliary alloy is low, and a good crushing effect can be obtained by adopting mechanical crushing, so that the crushing process can be simplified; the coarse powder is mixed and then crushed by gas flow, so that the mixing uniformity of the three components can be increased, and the magnetic performance of the magnet can be improved.
Preferably, in the step S3, the lubricant is gasoline, and the addition amount of the lubricant is 0.04-0.1% of the total mass of the main phase alloy and the grain boundary alloy; the magnetic field intensity of the magnetic field press during pressing is 1.5-2.0T, and the pressing pressure is 14-18 MPa; the pressure of the cold isostatic pressing is 180-220 MPa.
By adopting the technical scheme, the pressing is carried out in the magnetic field press mainly for arranging the magnetic powder along the C axis direction as much as possible and improving the residual magnetism of the magnet; and further cold isostatic pressing is mainly performed to avoid cracking mainly in the magnet during vacuum sintering. The lubricant is added primarily to reduce the surface tension between the powders so that they can be better pressed into green bodies.
Preferably, in the step S4, the specific process of the four-stage temperature vacuum sintering includes: firstly, heating to 300-350 ℃, and preserving heat for 0.5-1.5 h; then heating to 650-700 ℃, and preserving heat for 3-4 h; then heating to 850-900 ℃, and preserving the heat for 3-4 h; finally, the temperature is raised to 1000-1200 ℃, and the temperature is kept for 1-2 h.
By adopting the technical scheme, firstly heating to 300-350 ℃ to remove the lubricant in the components, then heating to 650-700 ℃ to assist solid solution between the alloy and the grain boundary alloy, and then continuously heating to 850-900 ℃ to diffuse the formed solid solution; and finally, heating to the sintering temperature to assist the volatilization of the alloy.
Preferably, in step S4, the specific process parameters of the aging treatment are as follows: heating the sintered blank to 900-950 ℃ for aging treatment for 3-4 h, then cooling to room temperature at the cooling rate of 1-3 ℃/min, then heating to 600-750 ℃ for aging treatment for 3-4 h, and then cooling to room temperature at the cooling rate of 1-3 ℃/min.
By adopting the technical scheme, the phenomena of uneven main phase grain boundary of the magnet, uneven distribution of the rare earth-rich phase at the main phase grain boundary, serious segregation and the like can be effectively prevented through two-stage temperature aging treatment, and the distribution of a shell layer dispersion phase formed by the grain boundary alloy can be more uniform; the aging treatment can also make the crystal grains more uniformly distributed and the shape more regular, and can make the distribution of each phase more uniform, thereby achieving the purpose of fully inhibiting the magnetic coupling effect among the crystal grains of the main phase of the magnet and further improving the coercive force of the neodymium iron boron magnet.
In summary, the present application includes at least one of the following beneficial technical effects:
1. according to the method, the main phase alloy and the grain boundary alloy are separated to prepare the thin strip and then sintered, so that the grain boundary alloy can be greatly reduced from entering the main phase, the rare earth elements in the grain boundary alloy mainly form a shell layer rich in heavy rare earth at the edge of the main phase grain, and the non-rare earth elements mainly exist in a dispersed phase form.
2. The auxiliary alloy is added in the application, the auxiliary alloy is mainly used for carrying out solid solution with the grain boundary alloy to form a solid solution phase, so that the grain boundary alloy can be well introduced into the edge of the main phase, a dispersed phase is formed at the same time, the further reaction of the grain boundary alloy and elements in the main phase is reduced, and the magnetic performance is reduced.
3. According to the method, the sintering process is designed according to the components, and the reduction of magnetic performance caused by the fact that the grain boundary alloy replaces elements in the main phase can be reduced by adopting the sintering process.
Detailed Description
Example 1
The ratio of each component in this example is shown in table 1, and the specific preparation process is as follows:
TABLE 1
S1: the main phase alloy is proportioned according to the proportion and then added into a vacuum induction furnace, heated to 1550 ℃ and smelted for 8min to obtain main phase alloy melt; then controlling the rotating speed of the water-cooling copper roller to be 2.6m/s, reducing the temperature at a cooling rate of 180 ℃/s, and carrying out rapid hardening and throwingThe strip was obtained as a thin strip of the main phase alloy having an average thickness of about 0.28mm. Then putting the main phase alloy thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the particle size of the coarse powder is 60-100 um to obtain main phase alloy coarse powder.
S2, proportioning the grain boundary alloy according to a proportion, adding the mixture into a vacuum induction furnace, heating to 1500 ℃, and smelting for 7min to obtain a grain boundary alloy melt; and then controlling the rotating speed of the water-cooling copper roller to be 1.8m/s, reducing the temperature at a cooling rate of 155 ℃/s, and carrying out rapid solidification strip throwing to obtain a grain boundary alloy thin strip, wherein the average thickness of the thin strip is about 0.33mm. Then putting the main phase alloy thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the grain diameter of coarse powder is 60-100 um to obtain grain boundary alloy coarse powder.
S3: and mechanically crushing the MgZn alloy in an inert atmosphere until the crushed MgZn alloy is less than 100um to obtain auxiliary alloy coarse powder.
S4: and mixing the main phase alloy coarse powder, the crystal boundary alloy coarse powder and the auxiliary alloy coarse powder according to a ratio, and then carrying out jet milling to obtain mixed powder with the particle size of less than 5um.
S5: adding gasoline which is 0.06 percent of the total mass of the mixed powder into the mixed powder, and uniformly mixing to obtain a mixture; placing the mixture in a mold of a magnetic field press, pressing into a blank in a magnetic field with the magnetic strength of 2.0T under 16MPa, then vacuum packaging the blank, placing in a cold isostatic pressing mold, and further pressing under 200MPa to obtain a blank.
S6: placing the blank in a vacuum sintering furnace, firstly heating to 350 ℃, and preserving heat for 1h; then heating to 700 ℃, and preserving heat for 3h; then raising the temperature to 900 ℃, and preserving the heat for 4 hours; finally, heating to 1100 ℃, and preserving heat for 2 hours to obtain a sintered blank; and after cooling the sintered blank to room temperature, heating the sintered blank to 900 ℃ for carrying out primary aging treatment for 3h, then cooling to room temperature at the cooling rate of 3 ℃/min, then heating to 700 ℃, carrying out aging treatment for 3h, and then cooling to room temperature at the cooling rate of 3 ℃/min to obtain the corrosion-resistant permanent magnet material.
Example 2
Substantially the same as example 1, except that the sintering process in step S6 is different, specifically as follows;
s6: placing the blank in a vacuum sintering furnace, firstly heating to 350 ℃, and preserving heat for 1h; then heating to 900 ℃, and preserving heat for 4 hours; finally, heating to 1100 ℃, and preserving the heat for 2 hours to obtain a sintered blank; and after cooling the sintered blank to room temperature, heating the sintered blank to 900 ℃ for carrying out primary aging treatment for 3h, then cooling to room temperature at the cooling rate of 3 ℃/min, then heating to 700 ℃, carrying out aging treatment for 3h, and then cooling to room temperature at the cooling rate of 3 ℃/min to obtain the corrosion-resistant permanent magnet material.
Example 3
Substantially the same as example 1, except that there is no aging process in step S6, as follows;
s6: placing the blank in a vacuum sintering furnace, firstly heating to 350 ℃, and preserving heat for 1h; then heating to 900 ℃, and preserving heat for 4 hours; and finally, heating to 1100 ℃, and preserving the heat for 2 hours to obtain the corrosion-resistant permanent magnet material.
Comparative example 1
The procedure was substantially the same as in example 1, except that no auxiliary alloy was added, and the remaining steps were the same.
Comparative example 2
Basically consistent with the embodiment 1, the difference is that the crystal boundary alloy and the main phase alloy are not distinguished, and the thin strip is prepared by directly mixing the raw materials according to the proportion; the method comprises the following specific steps:
s1: after proportioning the main phase alloy and the grain boundary alloy according to the proportion, adding the main phase alloy and the grain boundary alloy into a vacuum induction furnace together, heating to 1550 ℃ and smelting for 8min to obtain main phase alloy melt; and then controlling the rotating speed of the water-cooling copper roller to be 2.6m/s and the cooling rate to be 180 ℃/s, and carrying out rapid hardening strip throwing to obtain a main-phase alloy thin strip, wherein the average thickness of the thin strip is about 0.28mm. Then the main phase alloy thin strip is put into a stainless steel container,vacuum pumping is carried out to 10 -2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the particle size of the coarse powder is 60-100 um to obtain mixed alloy coarse powder.
S2: and mechanically crushing the MgZn alloy in an inert atmosphere until the size is less than 100um to obtain auxiliary alloy coarse powder.
The subsequent steps are consistent.
The permanent magnets in examples 1 to 3 and comparative examples 1 to 2 were tested for magnetic properties (coercive force, remanence, and maximum magnetic energy product), and the data thereof are shown in table 2.
The permanent magnets of examples 1 to 3 and comparative examples 1 to 2 were prepared into 10 cylindrical samples of phi 10X 10mm by machining, and subjected to HAST test (120 ℃,96% RH,1.5bar, 168H) to characterize their corrosion resistance properties, and the weight loss data thereof are shown in Table 2.
As can be seen from the data in Table 2, example 1 has better comprehensive magnetic properties, and the coercive force is relatively higher, which shows that the high temperature resistance is better.
Compared with the embodiment 2, the embodiment 1 only carries out three-stage temperature sintering, and a period of solid solution heat preservation time is shortened, so that the grain boundary alloy component and the auxiliary alloy component do not fully generate solid solution, and when the grain boundary alloy diffuses to the periphery of the main phase, the dispersed phase of the auxiliary alloy does not fully exert the barrier effect, so that a small part of the grain boundary alloy enters the main phase to replace elements in the main phase, and the remanence and the maximum magnetic energy product of the grain boundary alloy are greatly reduced; the corrosion resistance in example 2 also shows a certain decrease, probably because the MgZn dispersed phase remaining in the magnet after solid solution in example 1 is relatively more, and thus the potential difference between the rare-earth-rich phase and the main phase can be better decreased, thereby improving the corrosion resistance.
Compared with the embodiment 3, the embodiment 1 mainly does not carry out aging treatment, so the coercive force is slightly reduced, probably because the aging treatment carried out in the embodiment 1 can ensure that the crystal grains are more uniformly distributed and the shape is more regular, and each phase is more uniformly distributed, so that the magnetic coupling effect among the crystal grains of the main phase of the magnet is sufficiently inhibited, and the coercive force of the neodymium iron boron magnet is improved.
Compared with the comparative example 1, in the comparative example 1, the auxiliary alloy is not added, so that after the grain boundary alloy is added, a small part of grain boundary alloy elements enter a main phase, and the magnetic performance is reduced to a certain extent. More importantly, the corrosion resistance is obviously reduced, mainly because the dispersed phase in the permanent magnet is reduced more without the auxiliary alloy, so that the reduction of the potential difference between the rare earth-rich phase and the main phase is limited, and the corrosion resistance is obviously reduced.
Example 1 compared with comparative example 2, the main phase alloy and the grain boundary alloy in comparative example 2 were melted together, so that the grain boundary alloying element would tend to replace the element in the main phase by a large amount, causing antiferromagnetic coupling, and although the coercive force is increased remarkably, the magnetic performance is greatly reduced. As can be seen from the data in table 2, the corrosion resistance in comparative example 2 also showed a significant decrease, mainly due to the more decreased dispersed phases in the permanent magnet; because the auxiliary alloy basically volatilizes, the dispersion phase of Co and Cu is greatly reduced.
Example 4
In substantial agreement with example 1, with the difference that the proportions of the individual components are different, see table 3.
Example 5
In substantial agreement with example 1, with the difference that the proportions of the components are different, see table 4.
Example 6
The proportions of the components in this example are shown in table 5, and the specific preparation method is as follows:
TABLE 5
S1: after proportioning the main phase alloy according to the proportion, adding the main phase alloy into a vacuum induction furnace, heating to 1500 ℃ and smelting for 10min to obtain main phase alloy melt; and then controlling the rotating speed of the water-cooling copper roller to be 3.3m/s and the cooling rate to be 200 ℃/s, and performing rapid solidification strip throwing to obtain a main-phase alloy thin strip, wherein the average thickness of the thin strip is about 0.25mm. Then putting the main phase alloy thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the grain diameter of the coarse powder is 60-100 um to obtain main phase alloy coarse powder.
S2, proportioning the grain boundary alloy according to a proportion, adding the grain boundary alloy into a vacuum induction furnace, heating to 1450 ℃, and smelting for 9min to obtain a grain boundary alloy melt; and then controlling the rotating speed of the water-cooling copper roller to be 2.0m/s and the cooling rate to be 165 ℃/s, and carrying out rapid solidification strip throwing to obtain a grain boundary alloy thin strip, wherein the average thickness of the thin strip is about 0.31mm. Then putting the main phase alloy thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the grain diameter of the coarse powder is 60-100 um to obtain the grain boundary alloy coarse powder.
S3: and mechanically crushing the MgZn alloy in an inert atmosphere until the crushed MgZn alloy is less than 100um to obtain auxiliary alloy coarse powder.
S4: and mixing the main phase alloy coarse powder, the crystal boundary alloy coarse powder and the auxiliary alloy coarse powder according to a ratio, and then carrying out jet milling to obtain mixed powder with the particle size of less than 5um.
S5: adding gasoline which is 0.08 percent of the total mass of the mixed powder into the mixed powder, and uniformly mixing to obtain a mixed material; placing the mixture in a mold of a magnetic field press, pressing into a blank in a magnetic field with the magnetic strength of 1.5T under 18MPa, then vacuum packaging the blank, placing in a cold isostatic pressing mold, and further pressing under the pressure of 180MPa to obtain a blank.
S6: placing the blank in a vacuum sintering furnace, firstly heating to 300 ℃, and preserving heat for 1h; then heating to 650 ℃, and preserving heat for 3 hours; then heating to 850 ℃, and preserving heat for 4 hours; finally, heating to 1150 ℃, and preserving heat for 2 hours to obtain a sintered blank; and after cooling the sintered blank to room temperature, heating the sintered blank to 950 ℃ for carrying out primary aging treatment for 3h, then cooling to room temperature at the cooling rate of 2 ℃/min, then heating to 750 ℃, carrying out aging treatment for 3h, and then cooling to room temperature at the cooling rate of 2 ℃/min to obtain the corrosion-resistant permanent magnet material.
Example 7
The proportions of the components in this example are shown in table 6, and the specific preparation method is as follows:
TABLE 6
S1: after proportioning the main phase alloy according to the proportion, adding the main phase alloy into a vacuum induction furnace, heating to 1580 ℃, and smelting for 7min to obtain main phase alloy melt; and then controlling the rotating speed of the water-cooling copper roller to be 3.0m/s and the cooling rate to be 192 ℃/s, and carrying out rapid hardening strip throwing to obtain a main-phase alloy thin strip, wherein the average thickness of the thin strip is about 0.27mm. Then the main phase alloy thin strip is put into a stainless steel container and is vacuumized to 10- 2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing hydrogen pressure along with the crushing of the thin strip in hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the grain diameter of the coarse powder is 60-100 um to obtain main phase alloy coarse powder.
S2, mixing the grain boundary alloy according to a proportion, adding the mixture into a vacuum induction furnace, and heatingSmelting at 1550 ℃ for 7min to obtain a crystal boundary alloy solution; and then controlling the rotating speed of the water-cooling copper roller to be 2.0m/s and the cooling rate to be 165 ℃/s, and carrying out rapid solidification strip throwing to obtain a grain boundary alloy thin strip, wherein the average thickness of the thin strip is about 0.32mm. Then the main phase alloy thin strip is put into a stainless steel container and is vacuumized to 10- 2 Pa, introducing high-purity hydrogen (purity 99.9999%) until the gas pressure in the furnace reaches 10% 3 Pa, continuously reducing the hydrogen pressure along with the crushing of the thin strip in a hydrogen absorption reaction, and introducing high-purity hydrogen to maintain the stable hydrogen pressure; and (3) crushing hydrogen until the grain diameter of coarse powder is 60-100 um to obtain grain boundary alloy coarse powder.
S3: and mechanically crushing the MgZn alloy in an inert atmosphere until the crushed MgZn alloy is less than 100um to obtain auxiliary alloy coarse powder.
S4: and mixing the main phase alloy coarse powder, the crystal boundary alloy coarse powder and the auxiliary alloy coarse powder according to a ratio, and then carrying out jet milling to obtain mixed powder with the particle size of less than 5um.
S5: adding gasoline which accounts for 0.09 percent of the total mass of the mixed powder into the mixed powder, and uniformly mixing to obtain a mixture; placing the mixture in a mold of a magnetic field press, pressing into a blank in a magnetic field with the magnetic strength of 2.0T under 14MPa, then vacuum packaging the blank, placing in a cold isostatic mold, and further pressing under 220MPa to obtain a blank.
S6: placing the blank in a vacuum sintering furnace, firstly heating to 330 ℃, and preserving heat for 0.5h; then heating to 650 ℃, and preserving heat for 4 hours; then heating to 900 ℃, and preserving heat for 3 hours; finally, heating to 1050 ℃, and preserving heat for 2 hours to obtain a sintered blank; and cooling the sintered blank to room temperature, heating the sintered blank to 950 ℃ for carrying out primary aging treatment for 3h, then cooling to room temperature at the cooling rate of 2 ℃/min, then heating to 750 ℃, carrying out aging treatment for 3h, and then cooling to room temperature at the cooling rate of 2 ℃/min to obtain the corrosion-resistant permanent magnet material.
The magnetic property data and the corrosion resistance data of the permanent magnetic materials of examples 4 to 7 are shown in table 7.
In examples 4 to 5, the ratio of the main phase alloy, the grain boundary alloy and the auxiliary alloy components was adjusted to a proper degree, and the magnetic properties, the temperature resistance and the corrosion resistance were uniform and varied to a certain extent, but the overall properties were good. In the embodiments 6 to 7, the component proportion and the process parameters are mainly carried out, the comprehensive performance of the permanent magnet also changes to a certain extent, but the overall performance is better.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (9)
1. The corrosion-resistant permanent magnetic material is characterized by comprising the following raw materials: 95 to 98 percent of main phase alloy and 2 to 5 percent of grain boundary alloy; the total amount of the main phase alloy and the grain boundary alloy is 100 percent; the alloy also comprises an auxiliary alloy, and the addition amount of the auxiliary alloy is 0.3 to 0.8 percent of the total amount of the main phase alloy and the grain boundary alloy;
wherein: the main phase alloy comprises the following components in percentage by mass: (64) - (68), (27) - (31), (0.92) - (1.02), (0.33) - (0.36), (0.05) - (0.15) of Fe, prNd, B, al, ti and Ni;
the grain boundary alloy comprises the following components in percentage by mass: dy, co, ga and Cu in the proportions of (1.1 to 2.0): 0.8 to 1.5): 0.1 to 0.3): 0.1 to 0.2;
the auxiliary alloy is MgZn alloy.
2. The corrosion-resistant permanent magnetic material according to claim 1, wherein the raw materials comprise: 97.35% main phase alloy, 2.65% grain boundary alloy; the addition amount of the auxiliary alloy is 0.5 percent of the total amount of the main phase alloy and the grain boundary alloy; wherein: the main phase alloy comprises the following components in percentage by mass: 66.82;
the grain boundary alloy comprises the following components in percentage by mass: 1.30 Dy, co, ga and Cu; the auxiliary alloy is a 60.
3. A method of manufacturing a corrosion resistant permanent magnetic material according to claim 1 or 2, comprising the steps of:
s1, proportioning a main phase alloy and a grain boundary alloy according to a proportion, respectively adding the main phase alloy and the grain boundary alloy into a vacuum induction furnace, carrying out vacuum melting, and after the melting is finished, respectively preparing a main phase alloy thin strip and a grain boundary alloy thin strip from an alloy liquid solution by a rapid hardening strip throwing process;
s2: respectively carrying out hydrogen crushing on the main phase alloy thin strip and the grain boundary alloy thin strip, mechanically crushing the auxiliary alloy to respectively obtain corresponding coarse powder, then mixing the three coarse powders according to a ratio, and carrying out jet milling to obtain mixed powder;
s3: adding a lubricant into the mixed powder in the step S3, and uniformly mixing to obtain a mixture; pressing the mixture into a blank by a magnetic field press, then vacuum packaging the blank, placing the blank into a cold isostatic pressing die, and further pressing to obtain a blank body;
s4: and (3) carrying out four-stage temperature vacuum sintering on the blank, obtaining a sintered blank after sintering, and further carrying out aging treatment on the sintered blank to obtain the corrosion-resistant permanent magnet material.
4. The method for preparing the corrosion-resistant permanent magnetic material according to claim 3, wherein in the step S1, the vacuum melting temperature is 1200-1600 ℃ and the melting time is 7-10min.
5. The method for preparing the corrosion-resistant permanent magnetic material according to claim 3, wherein in the step S1, in the rapid hardening and strip spinning process, the rotating speed of the water-cooled copper roller is 0.8-4.0 m/S, the cooling rate is 150-200 ℃/S, and the thickness of the sheet is 0.2-0.4 mm.
6. The method for preparing the corrosion-resistant permanent magnetic material according to claim 3, wherein in the step S2, the specific process of hydrogen fragmentation comprises: placing the thin strip into a stainless steel container, and vacuumizing to 10 DEG -2 Pa, introducing hydrogen until the pressure in the furnace reaches 10 2 ~10 3 Pa or moreHydrogen pressure is continuously reduced along with the breakage of the thin strip after hydrogen absorption reaction, and hydrogen needs to be introduced to maintain the stability of the hydrogen pressure; the particle size of the coarse powder after hydrogen crushing or mechanical crushing needs to be controlled within 60 to 100um; the particle size of the powder after the jet milling needs to be controlled to be 2.5 to 5um.
7. The method for preparing the corrosion-resistant permanent magnetic material according to claim 3, wherein in the step S3, the lubricant is gasoline, and the addition amount of the lubricant is 0.04-0.1% of the total mass of the main phase alloy and the grain boundary alloy; the magnetic field intensity of a magnetic field press during pressing is 1.5 to 2.0T, and the pressing pressure is 14 to 18MPa; the pressure of the cold isostatic pressing is 180 to 220MPa.
8. The method for preparing the corrosion-resistant permanent magnetic material according to claim 3, wherein in the step S4, the specific process of the four-stage temperature vacuum sintering is as follows: firstly, heating to 300-350 ℃, and keeping the temperature for 0.5-1.5 h; then heating to 650 to 700 ℃, and preserving heat for 3 to 4 hours; then heating to 850-900 ℃, and preserving heat for 3-4h; finally, heating to 1000 to 1200 ℃, and preserving heat for 1 to 2h.
9. The method for preparing the corrosion-resistant permanent magnet material according to claim 3, wherein in the step S4, specific process parameters of the aging treatment are as follows: heating the sintered blank to 900-950 ℃, carrying out aging treatment for 3-4 h, then cooling to room temperature at the cooling rate of 1-3 ℃/min, then heating to 600-750 ℃, carrying out aging treatment for 3-4 h, and then cooling to room temperature at the temperature of 1-3 ℃/min.
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