Corrosion-resistant permanent magnet material and method for producing the same

Abstract

The application relates to a kind of corrosion-resistant permanent magnet materials and its preparation method, raw materials include: 95~98% main phase alloy, 2~5% grain boundary alloy;The total amount of main phase alloy and grain boundary alloy is 100%;It also includes auxiliary alloy, the addition amount of auxiliary alloy is 0.3~0.8% of the total amount of main phase alloy and grain boundary alloy.In the application, the main phase alloy and the grain boundary alloy are prepared into thin strips separately, and then sintering, which can greatly reduce the grain boundary alloy into 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 the form of dispersed phase, using such a treatment scheme, the coercivity of the permanent magnet can be improved, and the potential difference between the rich rare earth phase and the main phase can be reduced, so that the high-temperature resistance and corrosion resistance can be improved without significantly reducing the magnetic properties.

Description

TECHNICAL FIELD

[0001] 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

[0002] Nd-Fe-B-based rare earth permanent magnetic material is the third generation of rare earth permanent magnetic functional material, has the strongest magnetism, and is the most widely used rare earth permanent magnetic material at present. At present, the Nd-Fe-B-based rare earth permanent magnetic material has become one of indispensable materials in emerging fields such as information, energy, medical treatment, transportation and national defense. With the popularization of the application range of the rare earth permanent magnetic material, the environment for use is more and more complex, and thus new requirements are put forward for corrosion resistance and high-temperature resistance.

[0003] Although the Nd-Fe-B-based rare earth permanent magnetic material has good comprehensive magnetic properties, the coercivity is not high, which causes a serious thermal demagnetization phenomenon in a high-temperature environment, seriously affecting the service life. At present, the most commonly used method is to add heavy rare earth elements to improve the temperature resistance, but the heavy rare earth elements will partially replace Nd in the main phase, causing a significant decrease in the magnetic properties.

[0004] In the Nd-Fe-B-based rare earth permanent magnetic material, the Nd element in the Nd-rich phase is very active, is easy to react with oxygen and water in the air to cause corrosion, and the electrode potential of the Nd-rich phase is greatly different from that of the main phase, so that a primary cell is easily formed in a corrosive environment to cause electrochemical corrosion, accelerate the corrosion of the magnet, and finally cause the grains of the main phase of the magnet to fall off and the magnet to powder. At present, the main method for improving the corrosion resistance of the Nd-Fe-B-based rare earth permanent magnetic material is to prepare a corrosion-resistant coating, but the preparation process of the corrosion-resistant coating is complex, and the bonding strength of the corrosion-resistant coating with the magnet is not enough, so the corrosion-resistant coating is easy to fall off and has limited corrosion resistance.

[0005] In view of the above related technologies, the inventors believe that the Nd-Fe-B-based rare earth permanent magnetic material has the defects of insufficient high-temperature resistance and corrosion resistance. SUMMARY

[0006] In order to improve the corrosion resistance and high-temperature resistance of the permanent magnetic material, the application provides a corrosion-resistant permanent magnetic material and a preparation method thereof.

[0007] In a first aspect, the application provides a corrosion-resistant permanent magnetic material, which adopts the following technical scheme:

[0008] A corrosion-resistant permanent magnetic material, raw materials of which include 95-98% of a main phase alloy and 2-5% of a grain boundary alloy; the total amount of the main phase alloy and the grain boundary alloy is 100%; and the corrosion-resistant permanent magnetic material further includes 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.

[0009] The main phase alloy component is composed of Fe, PrNd, B, Al, Ti and Ni with a mass ratio of (64-68):(27-31):(0.92-1.02):(0.33-0.36):(0.05-0.15):(0.05-0.15);

[0010] The grain boundary alloy is composed of Dy, Co, Ga and Cu with a mass ratio of (1.1-2.0):(0.8-1.5):(0.1-0.3):(0.1-0.2);

[0011] The auxiliary alloy is MgZn alloy.

[0012] By adopting the technical scheme, the raw material components are divided into three categories according to the performance in the application, the main phase alloy is mainly used to construct the rare earth-rich phase and the main phase, then the grain boundary alloy is introduced, the grain alloy phase powder and the main phase alloy powder are prepared separately, and the separate preparation is mainly to avoid the elements in the grain boundary alloy replacing the elements in the main phase, so that the magnetic performance is obviously decreased. The two kinds of powders are prepared separately, the heavy rare earth element Dy will not enter the main phase to cause the antiferromagnetic coupling, but will diffuse along the grain boundary phase to the surface of the main phase grain, and a heavy rare earth-rich shell layer is formed at the edge of the main phase grain, the heavy rare earth shell layer can enhance the local magnetic crystal anisotropy, thereby optimizing the coercivity of the magnet, but will not cause the magnetic performance to be obviously decreased. The introduction of Gd in the grain boundary alloy can form a non-ferromagnetic grain boundary phase Nd6Fe 13 Ga at the grain boundary phase, which not only can improve the coercivity of the magnet, but also can improve the wettability of the rare earth-rich phase; the synergistic effect of the rare earth element Dy and Ga can further improve the coercivity of the magnet. The Cu and Co in the grain boundary alloy will 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.

[0013] The auxiliary alloy is also introduced in the application, and the auxiliary alloy mainly adopts the 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 performance of the grain boundary alloy, the auxiliary alloy is adopted. The low-melting-point auxiliary alloy can form a solid solution with the grain boundary alloy, thereby improving the diffusion performance of the grain boundary alloy, and the auxiliary metal will form a dispersed phase during the diffusion process, which surrounds the main phase to avoid the grain boundary phase entering the main phase. At the same time, the auxiliary alloy has a low boiling point, which will volatilize during the sintering process, so that the residual amount in the magnet will be relatively low, and a small amount of residual metal is mainly dispersedly distributed at the grain boundary, which can reduce the potential difference between the main phase and the rare earth-rich phase, thereby improving the corrosion resistance; and the auxiliary alloy has high reducibility, which can reduce the oxidation of other metals during the sintering process, thereby further improving the stability of the permanent magnet.

[0014] Preferably, the 97.35% main phase alloy, 2.65% grain boundary alloy; the addition amount of the auxiliary alloy is 0.5% of the total amount of the main phase alloy and the grain boundary alloy; wherein: the main phase alloy component is composed of Fe, PrNd, B, Al, Ti and Ni with a mass ratio of 66.82:29.00:0.98:0.35:0.10:0.10;

[0015] The grain boundary alloy is composed of Dy, Co, Ga and Cu with a mass ratio of 1.30:1.00:0.20:0.15; and the auxiliary alloy is a MgZn alloy with a mass ratio of 60:30.

[0016] By adopting the above technical solution, the comprehensive performance of the permanent magnet can be further improved by further controlling the proportion of each component.

[0017] In a second aspect, the application provides a preparation method of a corrosion-resistant permanent magnetic material, which adopts the following technical solution:

[0018] A preparation method of a corrosion-resistant permanent magnetic material, comprising the following steps:

[0019] S1: After the main phase alloy and the grain boundary alloy are proportioned, they are respectively added to a vacuum induction furnace for vacuum melting; after the melting is completed, the alloy liquid solution is prepared into a main phase alloy ribbon and a grain boundary alloy ribbon respectively by a rapid solidification ribbon casting process;

[0020] S2: The main phase alloy ribbon and the grain boundary alloy ribbon are respectively subjected to hydrogen crushing, and the auxiliary alloy is subjected to mechanical crushing to obtain corresponding coarse powders; then the three kinds of coarse powders are mixed in proportion and subjected to airflow milling to obtain a mixed powder;

[0021] S3: A lubricant is added to the mixed powder in step S3, and the mixed powder is uniformly mixed to obtain a mixed material; the mixed material is pressed into a blank by a magnetic field press, and then the blank is vacuum packaged and placed in a cold isostatic pressing mold for further pressing to obtain a compact;

[0022] S4: The compact is subjected to four-stage temperature vacuum sintering, and after sintering is completed, a sintered compact is obtained; the sintered compact is further subjected to aging treatment to obtain a corrosion-resistant permanent magnetic material,

[0023] By adopting the above technical solution, the compact is subjected to multi-stage vacuum sintering in the application, the first-stage sintering temperature is mainly to remove the lubricant in the compact, the second-stage vacuum sintering is mainly to make the auxiliary alloy and the grain boundary alloy form a solid solution phase, the third-stage sintering is mainly to make the solid solution phase diffuse with the main phase alloy, and the fourth-stage sintering temperature is mainly to remove the auxiliary alloy component; through the action of multi-stage vacuum sintering, the decline of magnetic performance caused by the replacement of elements in the main phase by the grain boundary alloy can be reduced.

[0024] Preferably, in step S1, the vacuum melting temperature is 1200–1600°C and the melting time is 7–10 min.

[0025] By adopting the above technical solution and controlling the melting temperature and time, the components can be mixed evenly, thereby forming a more uniform alloy sheet.

[0026] Preferably, in step S1, during the rapid solidification and spinning process, the rotation speed of the water-cooled copper roller is 0.8–4.0 m / s, the cooling rate is 150–200 °C / s, and the thickness of the sheet is 0.2–0.4 mm.

[0027] By adopting the above technical solution, the rapid solidification and strip spinning process can quickly cool the smelted alloy solution to room temperature, which can effectively inhibit grain growth and improve the magnetic properties of the magnet; moreover, by preparing it into thin sheets, it is easier to hydrogen break and improve the breaking efficiency.

[0028] Preferably, in step S2, the specific process of hydrogen crushing is as follows: the thin strip is placed in a stainless steel container and vacuumed to 10... -2 Pa, hydrogen gas is introduced until the gas pressure inside the furnace reaches 10. 2 ~10 3 Above Pa, as the thin strip breaks down due to hydrogen absorption reaction, the hydrogen pressure continuously decreases, requiring the introduction of hydrogen gas to maintain stable hydrogen pressure; the particle size of the coarse powder after hydrogen crushing or mechanical crushing needs to be controlled between 60 and 100 μm; the particle size of the powder after air jet milling needs to be controlled between 2.5 and 5 μm.

[0029] By adopting the above technical solutions, the hydrogen crushing of the thin strip in this application is mainly to induce intergranular and transgranular fractures in the thin strip; while the auxiliary alloy has low hardness, mechanical crushing can achieve a better crushing effect and simplify the crushing process; airflow crushing after mixing coarse powder can increase the mixing uniformity of the three components, thereby improving the magnetic properties of the magnet.

[0030] Preferably, in step S3, the lubricant is gasoline, and the amount added is 0.04 to 0.1% of the total mass of the main phase alloy and the grain boundary alloy; the magnetic field strength of the magnetic press is 1.5 to 2.0 T, the pressing pressure is 14 to 18 MPa, and the pressure of cold isostatic pressing is 180 to 220 MPa.

[0031] By adopting the above technical solution, pressing in a magnetic field press is mainly to ensure that the magnetic powder is aligned along the C-axis as much as possible, thereby increasing the remanence of the magnet. Further cold isostatic pressing is primarily to prevent cracking of the magnet during vacuum sintering. Adding a lubricant is mainly to reduce the surface tension between the powders, thus allowing for better pressing into a blank.

[0032] As preferred, in the step S4, the specific process of the four-stage temperature vacuum sintering is: firstly, heating to 300-350℃, and keeping for 0.5-1.5h; secondly, heating to 650-700℃, and keeping for 3-4h; thirdly, heating to 850-900℃, and keeping for 3-4h; and finally, heating to 1000-1200℃, and keeping for 1-2h.

[0033] By using the above technical solution, in the present application, firstly, the lubricant in the components is removed by heating to 300-350℃, then the solid solution between the auxiliary alloy and the grain boundary alloy occurs by heating to 650-700℃, then the diffusion of the formed solid solution occurs by continuing heating to 850-900℃, and finally, the auxiliary alloy volatilizes by heating to the sintering temperature.

[0034] As preferred, in the step S4, the specific process parameters of the aging treatment are: heating the sintered blank to 900-950℃ for aging treatment for 3-4h, then cooling to room temperature at a cooling rate of 1-3℃ / min, then heating to 600-750℃ for aging treatment for 3-4h, and then cooling to room temperature at a cooling rate of 1-3℃ / min.

[0035] By using the above technical solution, in the present application, the two-stage temperature aging treatment can effectively prevent the occurrence of the phenomena that the grain boundary of the main phase of the magnet is not straight, the rare earth-rich phase is not uniformly distributed at the grain boundary of the main phase, and the segregation is serious, and can also make the shell layer dispersed phase formed by the grain boundary alloy more uniformly distributed; the aging treatment can also make the grain distribution more uniform, the shape more regular, and the phase distribution more uniform, so as to fully inhibit the magnetic coupling effect between the main phase grains of the magnet, thereby improving the coercivity of the neodymium-iron-boron magnet.

[0036] In summary, the present application includes at least one of the following beneficial technical effects:

[0037] 1. In the present application, the main phase alloy and the grain boundary alloy are prepared separately into thin strips, and then sintered, which can greatly reduce the grain boundary alloy into 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 the form of dispersed phase. By using such a treatment scheme, the coercivity of the permanent magnet can be improved, and the potential difference between the rare earth-rich phase and the main phase can be reduced, thereby improving the high temperature resistance and corrosion resistance of the magnet with a small decrease in magnetic performance.

[0038] 2. In the present application, an auxiliary alloy is also added, which mainly forms a 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, and a dispersed phase is formed, reducing the further reaction between the grain boundary alloy and the elements in the main phase, and reducing the magnetic performance.

[0039] 3. The sintering process is designed according to the components in the method in the application, and the sintering process can reduce the decrease of magnetic properties caused by the substitution of elements in the main phase by grain boundary alloy. DETAILED DESCRIPTION

[0040] Example 1

[0041] The proportions of the components in this example are shown in Table 1, and the specific preparation process is as follows:

[0042] Table 1

[0043]

[0044] S1: The main phase alloy was proportioned according to the proportion, then added to a vacuum induction furnace, heated to 1550℃ for melting for 8min, to obtain a main phase alloy melt; then the rotating speed of the water-cooled copper roller was controlled at 2.6m / s, and the cooling rate was 180℃ / s, and rapid solidification tape casting was carried out, to obtain a main phase alloy thin strip, and the average thickness of the thin strip was about 0.28mm. Then the main phase alloy thin strip was placed in a stainless steel container, vacuumized to 10 -2 Pa, high-purity hydrogen (purity 99.9999%) was introduced, until the hydrogen pressure in the furnace reached 10 3 Pa, with the hydrogen absorption reaction of the thin strip breaking, the hydrogen pressure continuously decreased, and high-purity hydrogen needed to be introduced to maintain stable hydrogen pressure; the hydrogen broken to coarse powder had a particle size of 60-100um, and the main phase alloy coarse powder was obtained.

[0045] S2: The grain boundary alloy was proportioned according to the proportion, then added to a vacuum induction furnace, heated to 1500℃ for melting for 7min, to obtain a grain boundary alloy melt; then the rotating speed of the water-cooled copper roller was controlled at 1.8m / s, and the cooling rate was 155℃ / s, and rapid solidification tape casting was carried out, to obtain a grain boundary alloy thin strip, and the average thickness of the thin strip was about 0.33mm. Then the main phase alloy thin strip was placed in a stainless steel container, vacuumized to 10 -2 Pa, high-purity hydrogen (purity 99.9999%) was introduced, until the hydrogen pressure in the furnace reached 10 3 Pa, with the hydrogen absorption reaction of the thin strip breaking, the hydrogen pressure continuously decreased, and high-purity hydrogen needed to be introduced to maintain stable hydrogen pressure; the hydrogen broken to coarse powder had a particle size of 60-100um, and the main phase alloy coarse powder was obtained.

[0046] S3: The MgZn alloy was mechanically broken in an inert atmosphere, broken to below 100um, to obtain auxiliary alloy coarse powder.

[0047] S4: The main phase alloy coarse powder, the grain boundary alloy coarse powder and the auxiliary alloy coarse powder were mixed according to the proportion, then airflow milling was carried out, and the powder particle size was less than 5um, to obtain a mixed powder.

[0048] S5: to the mixed powder, 0.06% of gasoline relative to the total mass of the mixed powder is added, and after being mixed uniformly, a mixture is obtained; the mixture is placed in a mold of a magnetic field press, and a blank is pressed in a magnetic field with a magnetic intensity of 2.0 T by adopting 16 MPa, then the blank is vacuum packaged, placed in a mold of cold isostatic pressing, and further pressed by adopting 200 MPa to obtain a compact.

[0049] S6: the compact is placed in a vacuum sintering furnace, first heated to 350℃, and kept for 1h; then heated to 700℃, and kept for 3h; then heated to 900℃, and kept for 4h; finally heated to 1100℃, and kept for 2h, to obtain a sintered compact; after the sintered compact is cooled to room temperature, the sintered compact is heated to 900℃ for the first aging treatment for 3h, then cooled to room temperature at a cooling rate of 3℃ / min, then heated to 700℃ for aging treatment for 3h, and then cooled to room temperature at a cooling rate of 3℃ / min, to obtain a corrosion-resistant permanent magnet material.

[0050] Example 2

[0051] The example is basically the same as example 1, and the difference lies in the sintering process in step S6, which is as follows:

[0052] S6: the compact is placed in a vacuum sintering furnace, first heated to 350℃, and kept for 1h; then heated to 900℃, and kept for 4h; finally heated to 1100℃, and kept for 2h, to obtain a sintered compact; after the sintered compact is cooled to room temperature, the sintered compact is heated to 900℃ for the first aging treatment for 3h, then cooled to room temperature at a cooling rate of 3℃ / min, then heated to 700℃ for aging treatment for 3h, and then cooled to room temperature at a cooling rate of 3℃ / min, to obtain a corrosion-resistant permanent magnet material.

[0053] Example 3

[0054] The example is basically the same as example 1, and the difference lies in that there is no aging process in step S6, which is as follows:

[0055] S6: the compact is placed in a vacuum sintering furnace, first heated to 350℃, and kept for 1h; then heated to 900℃, and kept for 4h; finally heated to 1100℃, and kept for 2h, to obtain a corrosion-resistant permanent magnet material.

[0056] Comparative Example 1

[0057] The example is basically the same as example 1, and the difference lies in that no auxiliary alloy is added, and the remaining steps are the same.

[0058] Comparative Example 2

[0059] The example is basically the same as example 1, and the difference lies in that the grain 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 specific steps are as follows:

[0060] S1: The main phase alloy and the grain boundary alloy were proportioned and then added into a vacuum induction furnace together, heated to 1550℃ for 8min to obtain a main phase alloy melt; then the rotating speed of a water-cooled copper roller was controlled at 2.6m / s, and the cooling rate was 180℃ / s to perform rapid solidification tape casting to obtain a main phase alloy thin strip, and the average thickness of the thin strip was about 0.28mm. Then the main phase alloy thin strip was placed in a stainless steel container, and vacuumized to 10 -2 Pa, and high-purity hydrogen (purity 99.9999%) was introduced until the gas pressure in the furnace reached 10 3 Pa, and the hydrogen pressure was continuously reduced as the hydrogen absorption reaction of the thin strip broke down, and high-purity hydrogen needed to be introduced to maintain the stability of the hydrogen pressure; the hydrogen broken down to a coarse powder with a particle size of 60-100um to obtain a mixed alloy coarse powder.

[0061] S2: The MgZn alloy was mechanically broken down in an inert atmosphere to below 100um to obtain a secondary alloy coarse powder.

[0062] The subsequent steps were consistent.

[0063] The magnetic properties (coercive force, remanence and maximum magnetic energy product) of the permanent magnets in Examples 1-3 and Comparative Examples 1-2 were tested, and the data are shown in Table 2.

[0064] The permanent magnets in Examples 1-3 and Comparative Examples 1-2 were prepared into 10 cylindrical samples of φ10x10mm by mechanical processing, and HAST test (120℃, 96%RH, 1.5bar, 168H) was performed to characterize the corrosion resistance, and the weight loss rate data are shown in Table 2.

[0065]

[0066] From the data in Table 2, it can be seen that Example 1 has better comprehensive magnetic properties, and the coercive force is relatively high, indicating that it has better high-temperature resistance.

[0067] Compared with Example 2, only three-stage temperature sintering was performed in Example 2, and one stage of solid solution holding time was less, so the components of the grain boundary alloy and the secondary alloy did not fully solid solution, and the grain boundary alloy diffused to the surrounding of the main phase, so the dispersion phase of the secondary alloy did not fully play its barrier role, and a small part of the grain boundary alloy entered the main phase, resulting in the substitution of elements in the main phase, thereby causing a large decrease in remanence and maximum magnetic energy product; the corrosion resistance in Example 2 also decreased to a certain extent, which may be because the MgZn dispersion phase remaining in the magnet after solid solution in Example 1 is relatively more, so it can better reduce the potential difference between the rare earth-rich phase and the main phase, thereby improving the corrosion resistance.

[0068] Compared with Example 3, Example 1 is mainly not subjected to aging treatment, so that the coercivity is slightly decreased. It is possible that the aging treatment in Example 1 can make the grain distribution more uniform, the shape more regular, and the phase distribution more uniform, so that the magnetic coupling effect between the grains of the main phase of the magnet is sufficiently inhibited, thereby improving the coercivity of the Nd-Fe-B magnet.

[0069] Compared with Comparative Example 1, no auxiliary alloy is added in Comparative Example 1, so that a small part of the grain boundary alloy elements will enter the main phase after the grain boundary alloy is added, so that the magnetic properties are decreased by a certain amplitude. More importantly, the corrosion resistance is obviously reduced. This is mainly because there is no auxiliary alloy, the dispersion phase in the permanent magnet is greatly reduced, so that the potential difference between the rare earth-rich phase and the main phase is reduced, thereby the corrosion resistance is obviously reduced.

[0070] Compared with Comparative Example 2, the main phase alloy and the grain boundary alloy in Comparative Example 2 are smelted together, so that the grain boundary alloy elements will inevitably replace the elements in the main phase in large quantities, causing the antiferromagnetic coupling. Although the coercivity is obviously increased, the magnetic properties are greatly decreased. As can be seen from the data in Table 2, the corrosion resistance of Comparative Example 2 is also obviously reduced, which is mainly caused by the decrease of the dispersion phase in the permanent magnet; because the auxiliary alloy is basically volatilized, and the Co and Cu dispersion phase is greatly reduced.

[0071] Example 4

[0072] The same as Example 1, the difference is that the proportions of the components are different, which can be seen in Table 3.

[0073]

[0074] Example 5

[0075] The same as Example 1, the difference is that the proportions of the components are different, which can be seen in Table 4.

[0076]

[0077] Example 6

[0078] The proportions of the components in this example are shown in Table 5, and the specific preparation method is as follows:

[0079] Table 5

[0080]

[0081] S1: The main phase alloy was proportioned and added into a vacuum induction furnace, heated to 1500℃ for 10 min to obtain a main phase alloy melt. Then the speed of the water-cooled copper roller was controlled at 3.3 m / s and the cooling rate was 200℃ / s to perform rapid solidification tape casting to obtain a main phase alloy thin strip with an average thickness of about 0.25 mm. Then the main phase alloy thin strip was placed in a stainless steel container and vacuumized to 10 -2 Pa, high-purity hydrogen (purity 99.9999%) was introduced until the furnace pressure reached 10 3 Pa, as the hydrogen absorption reaction of the thin strip broke, the hydrogen pressure continuously decreased, and high-purity hydrogen needed to be introduced to maintain stable hydrogen pressure; the hydrogen broken to coarse powder had a particle size of 60-100um, and a main phase alloy coarse powder was obtained.

[0082] S2: The grain boundary alloy was proportioned and added into a vacuum induction furnace, heated to 1450℃ for 9 min to obtain a grain boundary alloy melt. Then the speed of the water-cooled copper roller was controlled at 2.0 m / s and the cooling rate was 165℃ / s to perform rapid solidification tape casting to obtain a grain boundary alloy thin strip with an average thickness of about 0.31 mm. Then the main phase alloy thin strip was placed in a stainless steel container and vacuumized to 10 -2 Pa, high-purity hydrogen (purity 99.9999%) was introduced until the furnace pressure reached 10 3 Pa, as the hydrogen absorption reaction of the thin strip broke, the hydrogen pressure continuously decreased, and high-purity hydrogen needed to be introduced to maintain stable hydrogen pressure; the hydrogen broken to coarse powder had a particle size of 60-100um, and a main phase alloy coarse powder was obtained.

[0083] S3: The MgZn alloy was mechanically broken in an inert atmosphere to 100um or less to obtain a auxiliary alloy coarse powder.

[0084] S4: The main phase alloy coarse powder, the grain boundary alloy coarse powder and the auxiliary alloy coarse powder were mixed in proportion, and then airflow milling was performed to grind the powder particle size to less than 5um to obtain a mixed powder.

[0085] S5: Gasoline was added to the mixed powder at a proportion of 0.08% of the total mass of the mixed powder, and the mixture was uniformly mixed to obtain a mixed material; the mixed material was placed in a mold of a magnetic field press in a magnetic field with a magnetic intensity of 1.5T and was pressed into a blank at 18MPa, and then the blank was vacuum packaged and placed in a mold of cold isostatic pressing, and was further pressed at a pressure of 180MPa to obtain a billet.

[0086] S6: Put the green body into a vacuum sintering furnace, first heat to 300℃, keep for 1h; then heat to 650℃, keep for 3h; then heat to 850℃, keep for 4h; finally heat to 1150℃, keep for 2h, to obtain a sintered body; after the sintered body is cooled to room temperature, heat the sintered body to 950℃ for the first aging treatment for 3h, then reduce to room temperature at a rate of 2℃ / min, then heat to 750℃, for aging treatment for 3h, then reduce to room temperature at a rate of 2℃ / min, to obtain a corrosion-resistant permanent magnet material.

[0087] Example 7

[0088] The ratio of each component in this example is shown in Table 6, and the specific preparation method is as follows:

[0089] Table 6

[0090]

[0091] S1: After the main phase alloy is proportioned, it is added to a vacuum induction furnace, heated to 1580℃ for smelting for 7min, to obtain a main phase alloy melt; then the rotating speed of the water-cooled copper roller is controlled to be 3.0m / s, and the cooling rate is 192℃ / s, to perform rapid solidification tape casting, to obtain a main phase alloy thin strip, and the average thickness of the thin strip is about 0.27mm. Then the main phase alloy thin strip is placed in a stainless steel container, vacuumized to 10 2 Pa, high-purity hydrogen gas (purity 99.9999%) is introduced, until the gas pressure in the furnace reaches 10 3 Pa, as the hydrogen absorption reaction of the thin strip breaks, the hydrogen pressure continuously decreases, and high-purity hydrogen gas needs to be introduced to maintain stable hydrogen pressure; the hydrogen broken coarse powder has a particle size of 60-100um, to obtain a main phase alloy coarse powder.

[0092] S2: After the grain boundary alloy is proportioned, it is added to a vacuum induction furnace, heated to 1550℃ for smelting for 7min, to obtain a grain boundary alloy melt; then the rotating speed of the water-cooled copper roller is controlled to be 2.0m / s, and the cooling rate is 165℃ / s, to perform rapid solidification tape casting, to obtain a grain boundary alloy thin strip, and the average thickness of the thin strip is about 0.32mm. Then the main phase alloy thin strip is placed in a stainless steel container, vacuumized to 10 2 Pa, high-purity hydrogen gas (purity 99.9999%) is introduced, until the gas pressure in the furnace reaches 10 3 Pa, as the hydrogen absorption reaction of the thin strip breaks, the hydrogen pressure continuously decreases, and high-purity hydrogen gas needs to be introduced to maintain stable hydrogen pressure; the hydrogen broken coarse powder has a particle size of 60-100um, to obtain a main phase alloy coarse powder.

[0093] S3: The MgZn alloy is mechanically broken in an inert atmosphere, to be broken to below 100um, to obtain an auxiliary alloy coarse powder.

[0094] S4: The main phase alloy coarse powder, the grain boundary alloy coarse powder and the auxiliary alloy coarse powder are mixed in proportion, and then are subjected to airflow grinding to grind the powder particle size to be less than 5um, thereby obtaining a mixed powder.

[0095] S5: Gasoline is added to the mixed powder in an amount of 0.09% relative to the total mass of the mixed powder, and the mixed powder is mixed uniformly to obtain a mixture; the mixture is placed in a mold of a magnetic field press, and is pressed in a magnetic field with a magnetic field intensity of 2.0T at a pressure of 14MPa to obtain a blank, and then the blank is vacuum packaged and is placed in a mold of a cold isostatic press, and is further pressed at a pressure of 220MPa to obtain a compact.

[0096] S6: The compact is placed in a vacuum sintering furnace, and is first heated to 330℃ and is kept at this temperature for 0.5h; then is heated to 650℃ and is kept at this temperature for 4h; then is heated to 900℃ and is kept at this temperature for 3h; and finally is heated to 1050℃ and is kept at this temperature for 2h, thereby obtaining a sintered compact; after the sintered compact is cooled to room temperature, the sintered compact is heated to 950℃ and is subjected to a first aging treatment for 3h, and then is cooled to room temperature at a cooling rate of 2℃ / min, and then is heated to 750℃ and is subjected to an aging treatment for 3h, and then is cooled to room temperature at a cooling rate of 2℃ / min, thereby obtaining a corrosion-resistant permanent magnet material.

[0097] The magnetic property data and the corrosion resistance data of the permanent magnet materials in Examples 4-7 are shown in Table 7.

[0098]

[0099] In Examples 4-5, the proportions of the main phase alloy, the grain boundary alloy and the auxiliary alloy are adjusted in an appropriate amount, and the magnetic properties, the temperature resistance and the corrosion resistance all change in a certain range, but the overall performance is good. In Examples 6-7, the proportions and the process parameters are adjusted, and the comprehensive performance of the permanent magnet also changes in a certain range, but the overall performance is good.

[0100] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, so: any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A corrosion resistant permanent magnetic material, characterized by, The raw materials include: 95-98% main phase alloy, 2-5% grain boundary alloy; the total amount of the main phase alloy and the grain boundary alloy is 100%; and further include auxiliary alloy, 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; The main phase alloy component is composed of Fe, PrNd, B, Al, Ti and Ni with a mass ratio of (64-68):(27-31):(0.92-1.02):(0.33-0.36):(0.05-0.15):(0.05-0.15); The grain boundary alloy is composed of Dy, Co, Ga and Cu with a mass ratio of (1.1-2.0):(0.8-1.5):(0.1-0.3):(0.1-0.2); The auxiliary alloy is MgZn alloy; The preparation method of the corrosion-resistant permanent magnetic material comprises the following steps: S1: the main phase alloy and the grain boundary alloy are proportioned and then added into a vacuum induction furnace for vacuum melting; after the melting is completed, the alloy liquid solution is prepared into a main phase alloy ribbon and a grain boundary alloy ribbon through a rapid solidification ribbon casting process; S2: the main phase alloy ribbon and the grain boundary alloy ribbon are respectively subjected to hydrogen crushing, and the auxiliary alloy is subjected to mechanical crushing to obtain corresponding coarse powders; then the three kinds of coarse powders are mixed in proportion and subjected to airflow grinding to obtain a mixed powder; S3: a lubricant is added into the mixed powder in step S3, and the mixed powder is uniformly mixed to obtain a mixed material; the mixed material is pressed into a blank through a magnetic field press, and then the blank is vacuum packaged and placed in a mold of a cold isostatic press for further pressing to obtain a billet; S4: the billet is subjected to four-stage temperature vacuum sintering to obtain a sintered billet; and the sintered billet is further subjected to aging treatment to obtain a corrosion-resistant permanent magnetic material. In step S4, the specific process of the four-stage temperature vacuum sintering is: firstly, the temperature is raised to 300-350℃ and kept for 0.5-1.5h; then the temperature is raised to 650-700℃ and kept for 3-4h; then the temperature is raised to 850-900℃ and kept for 3-4h; finally, the temperature is raised to 1000-1200℃ and kept for 1-2h.

2. The corrosion-resistant permanent magnetic material according to claim 1, characterized in that, The raw materials include: 97.35% main phase alloy, 2.65% grain boundary alloy; the addition amount of the auxiliary alloy is 0.5% of the total amount of the main phase alloy and the grain boundary alloy; wherein: the main phase alloy component is composed of Fe, PrNd, B, Al, Ti and Ni with a mass ratio of 66.82:29.00:0.98:0.35:0.10:0.10; The grain boundary alloy is composed of Dy, Co, Ga and Cu with a mass ratio of 1.30:1.00:0.20:0.15; and the auxiliary alloy is MgZn alloy with a mass ratio of 60:

30.

3. The corrosion resistant permanent magnetic material of claim 1, wherein, In step S1, the vacuum melting temperature is 1200-1600℃, and the melting time is 7-10min.

4. The corrosion resistant permanent magnetic material of claim 1, wherein, In the rapid solidification ribbon casting process in step S1, the rotating speed of the water-cooled copper roller is 0.8-4.0m / s, the cooling rate is 150-200℃ / s, and the thickness of the ribbon is 0.2-0.4mm.

5. The corrosion resistant permanent magnetic material of claim 1, wherein, The specific process of hydrogen crushing in the step S2 is as follows: the thin strip is put into a stainless steel container, vacuumized to 10 -2 Pa, hydrogen is introduced until the gas pressure in the furnace reaches 10 2 ~10 3 Pa, and the hydrogen pressure is continuously reduced with the hydrogen absorption reaction of the thin strip, so that hydrogen needs to be introduced to maintain the stable hydrogen pressure; the particle size of the coarse powder after hydrogen crushing or mechanical crushing needs to be controlled in the range of 60-100 um; and the particle size of the powder after the airflow mill needs to be controlled in the range of 2.5-5 um.

6. The corrosion resistant permanent magnetic material of claim 1, wherein, In the step S3, the lubricant is gasoline, the additive amount is 0.04-0.1% of the total mass of the main phase alloy and the grain boundary alloy; the magnetic field strength during the pressing of the magnetic field press is 1.5-2.0T, and the pressing pressure is 14-18MPa; the pressure of the cold isostatic pressing is 180-220MPa.

7. The corrosion resistant permanent magnetic material of claim 1, wherein, In the step S4, the specific process parameters of the aging treatment are as follows: the sintered blank is heated to 900-950℃ for aging treatment for 3-4h, then cooled to room temperature at a cooling rate of 1-3℃ / min, and then heated to 600-750℃ for aging treatment for 3-4h, and then cooled to room temperature at a temperature cooling rate of 1-3℃ / min.

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