Method for improving performance consistency of neodymium iron boron low-boron high-gallium formula product

Abstract

The invention discloses a method for improving the performance consistency of a neodymium iron boron low-boron high-gallium formula product, which comprises the following steps of: when a sintering basin on which a pressed blank is placed is fed into a sintering furnace for sintering, firstly heating the sintering furnace to 730-770 DEG C, preserving heat on a temperature platform of 730-770 DEG C for 5-8 hours, then heating the sintering furnace to 910-950 DEG C, preserving heat for 1-2 hours, and then cooling to the room temperature to obtain the neodymium iron boron low-boron high-gallium formula product. The temperature of the sintering furnace is increased to 1050-1080 DEG C, heat preservation is conducted for 3-5 h, then the sintering furnace is cooled to the temperature below 100 DEG C, the cooling time is longer than 2.5 h, then the temperature is continuously increased to 880-920 DEG C, then heat preservation is conducted for 2-4 h, the temperature increasing time is longer than 2 h, then the temperature is cooled to the temperature below 100 DEG C, the cooling time is longer than 2.5 h, then the temperature is continuously increased to 400-550 DEG C, then heat preservation is conducted for 4-6 h, the temperature increasing time is longer than 2 h, and the heat preservation is conducted for 3-5 h. Then cooling to the temperature of 30 DEG C or below, wherein the cooling time is longer than 2.5 h; the method has the advantages that the sintering time can be prevented from being greatly prolonged and the production efficiency can be prevented from being greatly reduced while the performance consistency of the neodymium iron boron low-boron high-gallium formula product is remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for improving the consistency of product performance, and in particular to a method for improving the consistency of performance of NdFeB low-boron high-gallium formula products. Background Art

[0002] With the rapid development of the sintered NdFeB magnet industry, the market demand for high-performance and high-consistency sintered NdFeB magnets is increasing. The coercive force and maximum magnetic energy product of sintered NdFeB magnets produced by many manufacturers have reached the performance requirements of certain high-tech products, but an important reason why they are still not accepted is that the consistency is not high enough. The inconsistency of the performance of sintered NdFeB magnets will cause some sintered NdFeB magnets to fail to meet specific performance requirements in actual applications, thereby affecting the performance and service life of the overall product. In addition, sintered NdFeB magnets with inconsistent performance may also increase the cost of screening and inspection during the production process, and reduce production efficiency. Therefore, even if the performance of the sintered NdFeB magnets meets the requirements, if the consistency is not high enough, it will still affect the market competitiveness and customer satisfaction of the product.

[0003] The Chinese patent with the authorization announcement number CN213833747U discloses "A method for improving the performance consistency of sintered NdFeB magnets and its products". This method improves the performance consistency of sintered NdFeB magnets by adding a three-stage aging process in the tempering stage of the sintering process. Although this method can significantly improve the consistency, it usually takes 10-12 hours to add the three-stage aging process, which greatly increases the sintering time and reduces the production efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for improving the performance consistency of NdFeB low-boron high-gallium formula products, which can significantly improve the performance consistency of NdFeB low-boron high-gallium formula products while avoiding a significant increase in sintering time and a significant decrease in production efficiency.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for improving the performance consistency of NdFeB low-boron high-gallium formula products, first preparing powder, pressing the powder into a compact, then vacuum packaging the compact and then subjecting it to water isostatic pressing, then removing the vacuum packaging and placing it in a sintering basin at intervals and sending it into a sintering furnace for sintering, and the specific sintering process is: first heating the sintering furnace to 730°C-770°C, keeping it at the temperature platform of 730°C-770°C for 5-8h, then heating the sintering furnace to 910°C-950°C, and keeping it for 1-2h, and then heating the sintering furnace to 1050°C

[0006] -1080℃, keep warm for 3-5h, then cool the sintering furnace to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat up to 880℃-920℃ and keep warm for 2-4h, wherein the heating time is greater than 2h, then cool to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat up to 400℃-550℃ and keep warm for 4-6h, wherein the heating time is greater than 2h, then cool to a temperature below 30℃, wherein the cooling time is greater than 2.5h, at this time, a NdFeB low-boron and high-gallium formula product is obtained.

[0007] The sintering basin is sent into the sintering furnace in a nitrogen-protected manner.

[0008] The powder is prepared by the following process:

[0009] S1. The raw materials of the NdFeB low-boron and high-gallium formula products are melted into alloy liquid by a vacuum induction furnace, and the alloy liquid is cast into casting sheets by a rapid solidification and sheet throwing technology, and then preliminarily crushed to obtain casting sheet fragments;

[0010] S2. Crushing the cast sheet fragments by hydrogen to form coarse powder to obtain coarse powder particles with a diameter of 3.5-5 mm, and placing them in a tank protected by inert gas to prevent the coarse powder particles from contacting oxygen;

[0011] S3, transferring the coarse powder particles protected by inert gas to a jet mill for grinding to obtain fine powder particles with a particle size (D50) of 3.6 μm-4.0 μm. During the grinding process, oxygen is supplemented according to the process requirements, and the oxygen supplementation amount is between 0-30 ppm;

[0012] S4. Put the fine powder particles into a tank protected by inert gas, add agents and stir to form powder.

[0013] The specific process of vacuum packaging the green sheets and then subjecting them to water isostatic pressing, and then removing the vacuum packaging and placing them in a sintering basin at intervals is as follows: first, the green sheets are packaged in vacuum packaging bags and sealed with a vacuum packaging machine, and then the sealed green sheets are subjected to water isostatic pressing and sent to a nitrogen protection glove box with an oxygen content of less than 0.02%, and the film is stripped, and the green sheets are taken out of the vacuum packaging bags, and then the green sheets are spaced apart and placed in a sintering basin, wherein a gap of 50mm-80mm is left between two adjacent green sheets.

[0014] Compared with the prior art, the advantages of the present invention are that by improving the sintering process, the holding time of the temperature platform of 730℃-770℃ during the sintering process is extended from 3h in the current conventional sintering method to 5-8h, and more time is provided during the holding process of 730℃-770℃ for the gas inside the green compact to escape, so that the green compact can be degassed more fully, so that there is more space inside the green compact to optimize the grain boundary structure, improve the uniformity of the sintering density and microstructure, and thus significantly improve the performance consistency of the NdFeB low-boron high-gallium formula product. The invention only needs to appropriately extend the holding time of the temperature platform of 730℃-770℃ for 2-5h to improve the uniformity of sintering density and microstructure and achieve a significant improvement in consistency. Compared with the current method of improving the performance consistency of sintered NdFeB magnets by adding a new three-stage aging period of 10-12h, there is no need to add a three-stage aging period, and the sintering time can be reduced by 5-10h. While significantly improving the performance consistency of NdFeB low-boron and high-gallium formula products, it can avoid a significant increase in sintering time and a significant reduction in production efficiency. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below with reference to the embodiments.

[0016] Embodiment 1: A method for improving the performance consistency of NdFeB low-boron high-gallium formula products, first preparing a powder, pressing the powder into a green compact, then vacuum packaging the green compact and subjecting it to water isostatic pressing, then removing the vacuum packaging and placing it in a sintering basin at intervals and sending it into a sintering furnace for sintering, the specific sintering process is: first heating the sintering furnace to 750°C, keeping it at a temperature platform of 730°C-770°C for 5-8h, then heating the sintering furnace to 910°C-950°C, keeping it at that temperature for 1-2h, and then heating the sintering furnace to 10 50℃-1080℃, keep warm for 3-5h, then cool the sintering furnace to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat to 880℃-920℃ and keep warm for 2-4h, wherein the heating time is greater than 2h, then cool to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat to 400℃-550℃ and keep warm for 4-6h, wherein the heating time is greater than 2h, then cool to a temperature below 30℃, wherein the cooling time is greater than 2.5h, at this time, a NdFeB low-boron and high-gallium formula product is obtained.

[0017] In this embodiment, by improving the sintering process, the holding time of the temperature platform of 730℃-770℃ during the sintering process is extended from 3h in the current conventional sintering method to 5-8h, and more time is provided during the holding process of 730℃-770℃ to allow the gas inside the green compact to escape, so that the green compact can be degassed more fully, so that there is more space inside the green compact to optimize the grain boundary structure, improve the uniformity of the sintering density and microstructure, and thus significantly improve the performance consistency of the NdFeB low-boron high-gallium formula product. Therefore, the present invention only requires Properly extending the holding time of the temperature platform of 730℃-770℃ for 2-5h can improve the uniformity of sintered density and microstructure and achieve a significant improvement in consistency. Compared with the current method of improving the performance consistency of sintered NdFeB magnets by adding a new three-stage aging period of 10-12h, there is no need to add a three-stage aging period, and the sintering time can be reduced by 5-10h. While significantly improving the performance consistency of NdFeB low-boron and high-gallium formula products, it can avoid a significant increase in sintering time and a significant reduction in production efficiency.

[0018] Embodiment 2: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, the sintering basin is sent into the sintering furnace in a nitrogen-protected manner.

[0019] Embodiment 3: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, the powder is prepared by the following process:

[0020] S1. The raw materials of the NdFeB low-boron and high-gallium formula products are melted into alloy liquid by a vacuum induction furnace, and the alloy liquid is cast into casting sheets by a rapid solidification and sheet throwing technology, and then preliminarily crushed to obtain casting sheet fragments;

[0021] S2. Crushing the cast sheet fragments by hydrogen to form coarse powder to obtain coarse powder particles with a diameter of 3.5-5 mm, and placing them in a tank protected by inert gas to prevent the coarse powder particles from contacting oxygen;

[0022] S3, transferring the coarse powder particles protected by inert gas to a jet mill for grinding to obtain fine powder particles with a particle size (D50) of 3.6 μm-4.0 μm. During the grinding process, oxygen is supplemented according to the process requirements, and the oxygen supplementation amount is between 0-30 ppm;

[0023] S4. Put the fine powder particles into a tank protected by inert gas, add agents and stir to form powder.

[0024] Embodiment 4: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, the green sheets are first vacuum-packed and then water isostatically pressed, and then the vacuum packaging is removed and the green sheets are placed in a sintering basin at intervals. The specific process is as follows: the green sheets are first packed in vacuum packaging bags and packaged with a vacuum packaging machine, and then the packaged green sheets are subjected to water isostatic pressing and sent to a nitrogen protection glove box with an oxygen content of less than 0.02%, and the film is stripped, and the green sheets are taken out of the vacuum packaging bags, and then the green sheets are placed in a sintering basin at intervals, with a gap of 50mm-80mm left between adjacent green sheets.

[0025] In order to verify the effect of the method for improving the performance consistency of NdFeB low-boron high-gallium formula products of the present invention, 8 batches of NdFeB low-boron high-gallium formula products with brand 52H were prepared by using the method for improving the performance consistency of NdFeB low-boron high-gallium formula products of the present invention, a method using a traditional sintering process (the difference from the method for improving the performance consistency of NdFeB low-boron high-gallium formula products of the present invention is that the insulation time of the temperature platform of 730°C-770°C during the sintering process is 3h), and a method using the sintering process disclosed in an existing patent (Chinese patent with authorization announcement number CN213833747U) (the difference from the method for improving the performance consistency of NdFeB low-boron high-gallium formula products of the present invention is that the sintering process adopts the sintering process disclosed in the existing patent), and the performance data comparison is shown in Table 1.

[0026] Table 1 52H performance data comparison

[0027]

[0028]

[0029] In Table 1, Group A represents 8 batches of NdFeB low-boron high-gallium formula products with a brand name of 52H prepared by the method of the present invention for improving the performance consistency of NdFeB low-boron high-gallium formula products, Group B represents 8 batches of NdFeB low-boron high-gallium formula products with a brand name of 52H prepared by the traditional sintering process, and Group C represents 8 batches of NdFeB low-boron high-gallium formula products with a brand name of 52H prepared by the sintering process disclosed in the existing patent.

[0030] From the data in Table 1, we can see that in group A, H cJ The maximum value is 18.77, the minimum value is 18.07, H cJ The range is 0.7. In group B, H cJ The maximum value is 18.57, the minimum value is 17.18, H cJ The range is 1.43. In group C, H cJ The maximum value is 18.46, the minimum value is 17.33, HcJ The range of H in group A is 1.13. cJ The standard deviation of H in group B is 0.262. cJ The standard deviation of H in group C is 0.447. cJ The standard deviation of Br is 0.482; in group A, the maximum value of Br is 14.25, the minimum value is 14.05, and the range of Br is 0.2. In group B, the maximum value of Br is 14.44, the minimum value is 14.08, and the range of Br is 0.36. In group C, the maximum value of Br is 13.97, the minimum value is 13.31, and the range of Br is 0.66. The standard deviation of Br in group A is 0.07, the standard deviation of Br in group B is 0.127, and the standard deviation of Br in group C is 0.268; in group A, the maximum value of squareness is 97.5, the minimum value is 96.2, and the range of squareness is 1.3; in group B, the maximum value of squareness is 98, the minimum value is 95.1, and the range of squareness is 2.9; in group C, the maximum value of squareness is 96.5, the minimum value is 94.3, and the range of squareness is 2.2; the standard deviation of squareness of group A is 0.444, the standard deviation of squareness of group B is 0.916, and the standard deviation of squareness of group C is 0.815.

[0031] Analysis of the data in Table 1 shows that the H cJ The range of Br and squareness is significantly smaller than that of H in groups B and C. cJ , Br and squareness, H of group A cJ The standard deviations of H, Br and squareness are also significantly smaller than those of groups B and C. cJ Compared with the method using the traditional sintering process and the method using the sintering process disclosed in the existing patent, the method of improving the performance consistency of the NdFeB low-boron high-gallium formula product of the present invention is cJ There is a significant improvement, and H cJ The standard deviations of Br and squareness were significantly reduced, and the consistency was significantly improved.

[0032] In summary, the method of improving the performance consistency of NdFeB low-boron and high-gallium formula products of the present invention improves the sintering process and adopts an appropriate amount of extending the insulation time of the temperature platform of 730℃-770℃ for 2-5h to replace the existing solution of increasing the third-level aging. On the basis of ensuring high magnetic properties, the sintering time can be reduced by 5-10h, thereby significantly improving the performance consistency of NdFeB low-boron and high-gallium formula products while avoiding a significant increase in sintering time and a significant decrease in production efficiency.

Claims

1. A method for improving the performance consistency of NdFeB low-boron high-gallium formula products, first preparing powder, pressing the powder into a compact, then vacuum packaging the compact and then subjecting it to water isostatic pressing, then removing the vacuum packaging and placing it in a sintering basin at intervals and sending it into a sintering furnace for sintering, characterized in that The specific sintering process is: first heat the sintering furnace to 730-770℃, keep it at the temperature platform of 730℃-770℃ for 5-8h, then heat the sintering furnace to 910℃-950℃, and keep it for 1-2h, then heat the sintering furnace to 1050℃-1080℃, keep it for 3-5h, then cool the sintering furnace to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat to 880℃-920℃ and keep it for 2-4h, wherein the heating time is greater than 2h, then cool to a temperature below 100℃, wherein the cooling time is greater than 2.5h, then continue to heat to 400℃-550℃ and keep it for 4-6h, wherein the heating time is greater than 2h, then cool to a temperature below 30℃, wherein the cooling time is greater than 2.5h, at this time, a NdFeB low-boron high-gallium formula product is obtained.

2. A method for improving the performance consistency of NdFeB low-boron high-gallium formula products according to claim 1, characterized in that The sintering basin is sent into the sintering furnace in a nitrogen-protected manner.

3. A method for improving the performance consistency of NdFeB low-boron high-gallium formula products according to claim 1, characterized in that The powder is prepared by the following process: S1. The raw materials of the NdFeB low-boron and high-gallium formula products are melted into alloy liquid by a vacuum induction furnace, and the alloy liquid is cast into casting sheets by a rapid solidification and sheet throwing technology, and then preliminarily crushed to obtain casting sheet fragments; S2. Crushing the cast sheet fragments by hydrogen to form coarse powder to obtain coarse powder particles with a diameter of 3.5-5 mm, and placing them in a tank protected by inert gas to prevent the coarse powder particles from contacting oxygen; S3, transferring the coarse powder particles protected by inert gas to a jet mill for grinding to obtain fine powder particles with a particle size (D50) of 3.6 μm-4.0 μm. During the grinding process, oxygen is supplemented according to the process requirements, and the oxygen supplementation amount is between 0-30 ppm; S4. Put the fine powder particles into a tank protected by inert gas, add agents and stir to form powder.

4. A method for improving the performance consistency of NdFeB low-boron high-gallium formula products according to claim 2, characterized in that The specific process of vacuum packaging the green sheets and then subjecting them to water isostatic pressing, and then removing the vacuum packaging and placing them in a sintering basin at intervals is as follows: first, the green sheets are packaged in vacuum packaging bags and sealed with a vacuum packaging machine, and then the sealed green sheets are subjected to water isostatic pressing and sent to a nitrogen protection glove box with an oxygen content of less than 0.02%, and the film is stripped, and the green sheets are taken out of the vacuum packaging bags, and then the green sheets are spaced apart and placed in a sintering basin, wherein a gap of 50mm-80mm is left between two adjacent green sheets.

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