A high coercivity rare earth neodymium iron boron magnet and its preparation method

Abstract

The present invention discloses a high coercivity rare earth neodymium iron boron magnet and a preparation method thereof, which relates to the technical field of magnetic materials and comprises the following steps: preparing a PrCo5-type powder according to the following atomic ratio to obtain a Pr15.87Co84.13-x-y-z-mFexZnyTizAgm alloy, melting under vacuum and filling with argon gas, and casting to obtain a sheet alloy; performing a saturation hydrogen absorption treatment on the sheet alloy, and obtaining an alloy powder after cooling under nitrogen protection; mixing and ball-milling the alloy powder with zirconia balls to obtain an alloy fine powder; mixing the alloy fine powder with a jet mill powder of commercial N40 to obtain a fine powder; placing the fine powder into a magnetic field forming press for orientation forming to obtain a green compact; and subjecting the green compact to vacuum sintering and magnetic field heat treatment to obtain a magnet.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, particularly to the field of rare earth neodymium iron boron permanent magnetic materials, and specifically to a high coercivity rare earth neodymium iron boron magnet and a preparation method thereof. Background Art

[0002] Rare earth neodymium iron boron permanent magnetic materials, as the most representative magnetic materials today, are widely used in high-tech fields such as communication electronics, new energy vehicles, wind power generation, and industrial energy-saving motors. With the wide application, the performance and price competition of neodymium iron boron products are becoming increasingly fierce. How to obtain a neodymium iron boron magnet with high coercivity and high cost performance has become a difficult problem that domestic manufacturers urgently need to solve.

[0003] Currently, the intrinsic coercivity of commercial neodymium iron boron is only 1 / 5 to 1 / 3 of the theoretical value. In order to obtain magnets with high coercivity, a large number of studies have been carried out by various researchers. The most effective method is to add heavy rare earth elements such as Dy and Tb. However, the heavy rare earth resources are limited and the price is expensive. Therefore, how to reduce the price and the usage amount of heavy rare earth while ensuring high coercivity and improve the product cost performance has become one of the key development directions of enterprises in the future. Summary of the Invention

[0004] In order to solve the problems that the intrinsic coercivity of current commercial neodymium iron boron far fails to reach the theoretical value and expensive heavy rare earth elements need to be added, resulting in high cost for improving coercivity and low product cost performance, the present invention provides a high coercivity rare earth neodymium iron boron magnet and a preparation method thereof.

[0005] The present invention is implemented as follows:

[0006] The present invention provides a preparation method of a high coercivity rare earth neodymium iron boron magnet, comprising the following steps:

[0007] a, batching

[0008] Batch PrCo5 type powder according to the following atomic ratio to obtain Pr 15.87 Co 84.13-x-y-z-m Fe x Zn y Ti z Ag m alloy, where x = 4 - 15, y = 3.2 - 9.5, z = 2.7 - 4.4, m = 1.8 - 5.4;

[0009] b, melting

[0010] Pr 15.87 Co 84.13-x-y-z-m Fe x Zn y Ti z Agm The alloy is pumped to a vacuum degree less than 0.7 Pa, and argon gas is filled for melting. After all the metal is melted, continue melting for 2 - 3 min. Wait until the alloy solution is evenly mixed, adjust the rotation speed of the water-cooled copper roller for casting, and obtain sheet-like alloy for standby. The thickness of the sheet-like alloy is 0.3 - 0.4 mm;

[0011] c, Hydrogen absorption treatment

[0012] Place the sheet-like alloy prepared in step b in a hydrogen explosion furnace for saturated hydrogen absorption treatment. After the hydrogen absorption and crushing are completed, dehydrogenation is not carried out. After cooling, take it out of the furnace and put it into a mixing tank protected by nitrogen gas to obtain alloy powder;

[0013] d, Ball milling

[0014] Under the protection of inert gas, ball mill the alloy powder and zirconia balls with a mass ratio of (15 - 25):1 in a zirconia tank at a rotation speed of 300 - 400 r / min for 3 - 10 h to obtain alloy micropowder;

[0015] e, Mixing

[0016] Evenly mix the alloy micropowder in step d and the gas atomized powder of commercial N40. The component mass percentage of commercial N40 is PrNd: 24.5%, Ce: 7%, Al: 0.2%, Cu: 0.15%, Zr: 0.1%, and the balance is Fe. The proportion of the alloy micropowder by weight in the total weight is 1% - 7% to obtain fine powder containing alloy micropowder;

[0017] f, Green compact

[0018] Put the fine powders prepared in step e into a fully sealed magnetic field forming press with an oxygen content less than 10 ppm for orientation forming. The magnetic field strength is 1.8 T, and the density of the formed green compact is 4.3 ± 0.5 g / cm 3 , and obtain green compacts;

[0019] g, Vacuum sintering

[0020] Keep the green compacts prepared in step f in a vacuum environment below 1040 °C and 0.7 Pa for 180 min. After the heat preservation is completed, cool it in air under the protection of argon gas to below 50 °C and then take it out of the furnace;

[0021] h, Magnetic field heat treatment

[0022] Carry out magnetic field heat treatment on the product after vacuum sintering. The magnetic field heat treatment is carried out in a vacuum magnetic field heat treatment furnace with a vacuum degree less than 1.0E -1 Pa. Heat it up to 620 °C at a magnetic field strength of 2.5 T, keep it warm for 4 h. After the heat preservation is completed, cool it in air under the protection of argon gas to below 60 °C and then take it out of the furnace.

[0023] Preferably, in step a, x = 4, y = 9.5, z = 4.4, m = 1.8.

[0024] Preferably, in step a, x = 10, y = 3.2, z = 2.7, m = 3.1.

[0025] Preferably, in step a, x = 15, y = 6.4, z = 3.1, m = 5.4.

[0026] The present invention also provides a high coercivity rare earth neodymium iron boron magnet prepared according to the above method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The preparation method of the high coercivity rare earth neodymium iron boron magnet provided by the present invention, by utilizing that PrCo5 has a relatively high magnetocrystalline anisotropy field Ha (Ha: 167 Koe), and adopting a variety of processes such as hydrogen breaking, ball milling modification treatment, powder mixing and cooling treatment, magnetic field orientation forming, high temperature sintering and magnetic field aging heat treatment to mix with the neodymium iron boron magnetic powder, that is, adding an appropriate amount of PrCo5 type alloy micropowder to the Nd2Fe 14 B permanent magnet material, greatly improves the coercivity of the neodymium iron boron magnet when the PrCo5 type alloy is applied to the neodymium iron boron magnetic powder; enables the neodymium iron boron magnet to have a relatively high magnetocrystalline anisotropy field, while reducing the addition of heavy rare earths, reducing the production cost of the neodymium iron boron magnet, thereby obtaining a high coercivity neodymium iron boron magnet with low cost and increasing the economic benefits of actual production and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It shows the particle size distribution diagram of the powder in Example 1 of the present invention.

[0030] Figure 2 It shows the particle size distribution diagram of the powder in Example 2 of the present invention.

[0031] Figure 3 It shows the particle size distribution diagram of the powder in Example 3 of the present invention.

[0032] Figure 4 It shows the electron microscope image of the sintered magnet with a powder addition amount of 5% in Example 1 of the present invention.

[0033] Figure 5 It shows the electron microscope image of the sintered magnet with a powder addition amount of 7% in Example 2 of the present invention.

[0034] Figure 6 It shows the electron microscope image of the sintered magnet with a powder addition amount of 17% in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The following will give a detailed description of the specific embodiments of the present invention. Example 1

[0036] A preparation method of a high coercivity rare earth neodymium iron boron magnet is as follows:

[0037] a, batching

[0038] The PrCo5 type powder is batched according to the following atomic ratio to obtain Pr 15.87 Co 84.13-x-y-z-m Fe x Zn y Ti z Ag m alloy, x = 4, y = 9.5, z = 4.4, m = 1.8; that is, Pr 15.87 Co 64.43 Fe4Zn 9.5 Ti 4.4 Ag 1.8 alloy;

[0039] b, melting

[0040] Put the Pr 15.87 Co 64.43 Fe4Zn 9.5 Ti 4.4 Ag 1.8 alloy into a vacuum melting furnace and pump it to a vacuum degree less than 0.7 Pa, fill it with argon for melting, continue melting for 2 - 3 min after all the metals are melted, wait for the alloy solution to be mixed evenly, adjust the rotation speed of the water - cooled copper roller for casting, and obtain a sheet - shaped alloy with a thickness of 0.3 - 0.4 mm for standby;

[0041] c, hydrogen absorption treatment

[0042] Put the sheet - shaped alloy prepared in step b into a hydrogen explosion furnace for saturated hydrogen absorption treatment. After hydrogen absorption and crushing are completed, dehydrogenation is not carried out. After cooling, take it out and put it into a mixing tank protected by nitrogen to obtain alloy powder;

[0043] d, ball milling

[0044] Put the alloy powder and zirconia balls with a mass ratio of 25:1 into a zirconia tank, and ball mill at a rotation speed of 350 r / min for 3 h under the protection of inert gas to obtain alloy fine powder;

[0045] e, mixing

[0046] Evenly mix the alloy fine powder in step d and the gas - atomized powder of commercial N40. The proportion of the alloy fine powder by weight in the total weight is 2%, 3%, 4%, 5% to obtain four groups of fine powders containing alloy fine powder;

[0047] f, compacting

[0048] Put the fine powders obtained in step e into a fully sealed magnetic field molding press with an oxygen content of less than 10 ppm for orientation molding. The magnetic field strength is 1.8 T, and the density of the molded green compact is 4.3 ± 0.5 g / cm 3 , and green compacts are obtained;

[0049] g, vacuum sintering

[0050] Place the green compacts obtained in step f into a vacuum sintering furnace. Evacuate the furnace to below 0.7 Pa, heat up to 1040 °C, hold for 180 min, and after the holding is completed, cool it in air under argon protection to below 50 °C and then take it out of the furnace;

[0051] h, magnetic field heat treatment

[0052] Place the product after vacuum sintering into a vacuum magnetic field heat treatment furnace with a vacuum degree of less than 1.0E -1 Pa. Heat it up to 620 °C under a magnetic field strength of 2.5 T, hold for 4 h, and after the holding is completed, cool it in air under argon protection to below 60 °C and then take it out of the furnace.

[0053] Observe the prepared high coercivity rare earth neodymium iron boron magnet. As Figure 1 , 4 shown, Pr 15.87 Co 64.43 Fe4Zn 9.5 Ti 4.4 Ag 1.8 alloy fine powders are distributed around the main alloy and together with the rare earth rich phase form a smooth and continuous neodymium rich phase that wraps the main phase particles, thus realizing the optimization of the grain boundary structure and ultimately significantly improving the coercivity of the magnet.

[0054] Test the product performance, and the specific results are shown in Table 1 below:

[0055] Table 1

[0056]

[0057] When the powder addition amount in Example 1 is 5%, the intrinsic coercivity Hcj increases by 38.84% year-on-year, and the remanence Br decreases by 2.22% year-on-year. Example 2

[0058] A preparation method of a high coercivity rare earth neodymium iron boron magnet, the specific steps are as follows:

[0059] a, batching

[0060] Batch the PrCo5 type powder according to the following atomic ratio to obtain Pr 15.87 Co 84.13-x-y-z-m Fe x Zn y Ti z Agm Alloy, x = 10, y = 3.2, z = 2.7, m = 3.1; that is, Pr is obtained 15.87 Co 65.13 Fe 10 Zn 3.2 Ti 2.7 Ag 3.1 alloy;

[0061] b, melting

[0062] Put the Pr 15.87 Co 65.13 Fe 10 Zn 3.2 Ti 2.7 Ag 3.1 alloy into a vacuum melting furnace and evacuate it to a vacuum degree less than 0.7 Pa, then fill it with argon for melting. After all the metals are melted, continue melting for 2 - 3 min. Wait until the alloy solution is evenly mixed, adjust the rotation speed of the water-cooled copper roller for casting, and obtain a flaky alloy with a thickness of 0.3 - 0.4 mm for standby;

[0063] c, hydrogen absorption treatment

[0064] Put the flaky alloy prepared in step b into a hydrogen explosion furnace for saturated hydrogen absorption treatment. After hydrogen absorption and crushing are completed, do not dehydrogenate, and cool it and then take it out into a mixing tank protected by nitrogen to obtain alloy powder;

[0065] d, ball milling

[0066] Put the alloy powder and zirconia balls with a mass ratio of 15:1 into a zirconia tank, and ball mill at a rotation speed of 390 r / min for 5 h under the protection of inert gas to obtain alloy fine powder;

[0067] e, mixing

[0068] Evenly mix the alloy fine powder in step d and the gas atomized powder of commercial N40. The proportion of the alloy fine powder by weight in the total weight is 1%, 3%, 5%, 7%, and four groups of fine powders containing alloy fine powder are prepared;

[0069] f, green compact

[0070] Put each group of fine powders prepared in step e into a fully sealed magnetic field forming press with an oxygen content less than 10 ppm for orientation forming. The magnetic field strength is 1.8 T, and the density of the formed green compact is 4.3 ± 0.5 g / cm 3 , and green compacts are obtained;

[0071] g, vacuum sintering

[0072] Place the green body obtained in step f in a vacuum sintering furnace. Evacuate the furnace to below 0.7 Pa, heat up to 1000 °C, hold for 150 min, and after the holding is completed, cool it in air under argon protection to below 50 °C and then take it out of the furnace;

[0073] h, magnetic field heat treatment

[0074] Place the product after vacuum sintering in a vacuum magnetic field heat treatment furnace with a vacuum degree less than 1.0E -1 Pa. Heat it up to 510 °C under a magnetic field intensity of 3.5 T, hold for 3 h, and after the holding is completed, cool it in air under argon protection to below 60 °C and then take it out of the furnace.

[0075] Observe the prepared high coercivity rare earth neodymium iron boron magnet. As Figure 2 、 5 shown, the fine powder is distributed around the main alloy, and together with the rare earth rich phase, it forms a smooth and continuous neodymium rich phase that wraps the main phase particles, thus realizing the optimization of the grain boundary structure and ultimately significantly improving the coercivity of the magnet.

[0076] Test the product performance, and the specific results are shown in Table 2 below:

[0077] Table 2

[0078]

[0079] When the powder addition amount in Example 2 is 7%, the intrinsic coercivity Hcj increases by 51.24% year-on-year, and the remanence Br decreases by 1.51% year-on-year. Example 3

[0080] A preparation method of a high coercivity rare earth neodymium iron boron magnet, the specific steps are as follows:

[0081] a, batching

[0082] Batch the PrCo5 type powder according to the following atomic ratios to obtain Pr 15.87 Co 84.13-x-y-z-m Fe x Zn y Ti z Ag m alloy, x = 10, x = 15, y = 6.4, z = 3.1, m = 5.4; that is, obtain Pr 15.87 Co 54.23 Fe 15 Zn 6.4 Ti 3.1 Ag 5.4 alloy;

[0083] b, melting

[0084] Pr 15.87 Co 54.23 Fe15 Zn 6.4 Ti 3.1 Ag 5.4 The alloy is placed in a vacuum melting furnace and evacuated to a vacuum degree less than 0.7 Pa, then argon gas is filled for melting. After all the metals are melted, continue melting for 2 - 3 min. Wait until the alloy solution is evenly mixed, adjust the rotation speed of the water-cooled copper roller for casting, and obtain a flaky alloy with a thickness of 0.3 - 0.4 mm for standby;

[0085] c, Hydrogen absorption treatment

[0086] The flaky alloy prepared in step b is placed in a hydrogen explosion furnace for saturated hydrogen absorption treatment. After hydrogen absorption and crushing are completed, dehydrogenation is not carried out. After cooling, it is taken out of the furnace and put into a nitrogen-protected mixing tank to obtain alloy powder;

[0087] d, Ball milling

[0088] The alloy powder and zirconia balls with a mass ratio of 20:1 are placed in a zirconia tank and ball milled at a rotation speed of 310 r / min for 10 h under the protection of inert gas to obtain alloy micropowder;

[0089] e, Mixing

[0090] The alloy micropowder obtained in step d and the jet mill powder of commercial N40 are evenly mixed. The proportion of the alloy micropowder by weight in the total weight is 5%, 9%, 13%, and 17% to obtain four groups of fine powders containing alloy micropowder;

[0091] f, Green compact

[0092] Each group of fine powders prepared in step e is respectively put into a fully sealed magnetic field forming press with an oxygen content less than 10 ppm for orientation forming. The magnetic field strength is 1.8 T, and the density of the formed green compact is 4.3 ± 0.5 g / cm 3 , to obtain a green compact;

[0093] g, Vacuum sintering

[0094] The green compact prepared in step f is placed in a vacuum sintering furnace. The furnace is evacuated to below 0.7 Pa, heated to 1060 °C, and held for 120 min. After the holding is completed, it is air-cooled to below 50 °C under the protection of argon gas and taken out of the furnace;

[0095] h, Magnetic field heat treatment

[0096] The product after vacuum sintering is placed in a vacuum magnetic field heat treatment furnace with a vacuum degree less than 1.0E -1 Pa. It is heated to 680 °C under a magnetic field strength of 3.0 T and held for 2 h. After the holding is completed, it is air-cooled to below 60 °C under the protection of argon gas and taken out of the furnace.

[0097] Observe the prepared high coercivity rare earth neodymium iron boron magnets, such as Figure 3 ,6 As shown, the fine powder is distributed around the master alloy and, together with the rare-earth-rich phase, forms a smooth and continuous neodymium-rich phase that wraps the primary-phase particles, thus optimizing the grain-boundary structure and ultimately significantly enhancing the coercivity of the magnet.

[0098] The performance of the product was tested, and the specific results are shown in Table 3 below:

[0099] Table 3

[0100]

[0101] When the powder addition amount in Example 3 was 17%, the intrinsic coercivity Hcj increased by 67.76% year-on-year, and the remanence Br decreased by 3.81% year-on-year.

[0102] The high-coercivity rare-earth neodymium-iron-boron magnet prepared by the preparation method of the present invention, while enhancing the anisotropy of the neodymium-iron-boron magnet, significantly increases the intrinsic coercivity Hcj year-on-year, reduces the addition of heavy rare earths at the same time, controls the actual production raw material cost, and effectively increases economic benefits.

[0103] The scope of protection claimed by the present invention is not limited to the above specific embodiments. Moreover, for those skilled in the art, the present invention can have various deformations and modifications, and any modifications, improvements, and equivalent replacements made within the concept and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth neodymium iron boron magnet with high coercivity, characterized in that: The specific steps are as follows: a. Ingredients Prepare the PrCo5-type powder according to the following atomic ratios to obtain Pr 15.87 Co 64.43 Fe4Zn 9.5 Ti 4.4 Ag 1.8 alloy; b. Melting Put Pr 15.87 Co 64.43 Fe4Zn 9.5 Ti 4.4 Ag 1.8 Pump the alloy to a vacuum degree less than 0.7 Pa, fill it with argon for melting. After all the metals are melted, continue melting for 2 - 3 min. Wait until the alloy solution is evenly mixed, adjust the rotation speed of the water-cooled copper roller for casting, and obtain the flaky alloy for standby; c. Hydrogen absorption treatment The flaky alloy obtained in step b is subjected to saturated hydrogen absorption treatment, and after cooling, is taken out of the furnace and placed in a nitrogen-protected mixing tank to obtain alloy powder; d. Ball milling The alloy powder and zirconia balls with a mass ratio of 25:1 were ball-milled at a speed of 350 r / min for 3 h under inert gas protection to obtain alloy fine powder; e, mixed The alloy powder of step d is uniformly mixed with commercial N40 jet mill powder, wherein the weight of the alloy powder accounts for 5% of the total weight, to obtain a fine powder containing the alloy powder; f, green compact The fine powders of each group obtained in step e are placed in a fully sealed magnetic field forming press with an oxygen content of less than 10 ppm for orientation forming to obtain green compacts; g, vacuum sintering The green body obtained in step f is kept at 1040°C and a vacuum environment below 0.7 Pa for 180 minutes, and then air-cooled to below 50°C under argon protection before being taken out of the furnace; h, magnetic field heat treatment The vacuum sintered product was heated to 620°C in a magnetic field of 2.5 T and kept warm for 4 hours. After the heat preservation was completed, it was air-cooled to below 60°C under argon protection and then taken out of the furnace.

2. The preparation method of a high coercivity rare earth neodymium iron boron magnet according to claim 1, characterized in that: In step b, the thickness of the sheet alloy is 0.3 to 0.4 mm.

3. The preparation method of a high coercivity rare earth neodymium iron boron magnet according to claim 1, characterized in that: In step f, the magnetic field strength is 1.8 T, and the density of the formed green compact is 4.3 ± 0.5 g / cm 3 .

4. The preparation method of a high coercivity rare earth neodymium iron boron magnet according to claim 1, characterized in that: In step h, the magnetic field heat treatment is carried out in a vacuum magnetic field heat treatment furnace with a vacuum degree less than 1.0E -1 Pa.

5. A high coercivity rare earth neodymium iron boron magnet prepared according to claim 1.

Images