CN105219937B - Method for producing neodymium iron boron rare earth permanent magnet material - Google Patents
Method for producing neodymium iron boron rare earth permanent magnet material Download PDFInfo
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- CN105219937B CN105219937B CN201410286944.XA CN201410286944A CN105219937B CN 105219937 B CN105219937 B CN 105219937B CN 201410286944 A CN201410286944 A CN 201410286944A CN 105219937 B CN105219937 B CN 105219937B
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Abstract
The invention provides a method for producing a neodymium iron boron rare earth permanent magnet material. The method for producing the neodymium iron boron rare earth permanent magnet material comprises the following steps: preparing a sintered neodymium iron boron blank, and machining the sintered neodymium iron boron blank; carrying out heat treatment on the sintered neodymium iron boron blank under vacuum; and slowly cooling the sintered neodymium iron boron blank subjected to heat treatment to room temperature under vacuum. The temperature for carrying out heat treatment on the sintered neodymium iron boron blank under vacuum is 250-450 ℃, and the heat preservation time is 0.5-3.5 hours. And slowly cooling the sintered neodymium iron boron blank subjected to heat treatment to room temperature under vacuum, and naturally cooling the sintered neodymium iron boron blank under vacuum, or cooling the sintered neodymium iron boron blank subjected to heat treatment at a cooling speed of 50-100 ℃/h at a controlled temperature.
Description
Technical Field
The invention relates to a method for producing a neodymium iron boron rare earth permanent magnet material, which can eliminate the surface residual stress of the permanent magnet material and improve the mechanical property of the neodymium iron boron rare earth permanent magnet material.
Background
As an important functional material, the rare earth permanent magnet material has generally poor mechanical properties, so that the rare earth permanent magnet is easy to crack and drop slag in the processing process. The method greatly reduces the finished product rate and the processing precision of the magnet, increases the processing cost of the magnet, and limits the application of the magnet in the high-precision instrument industry.
Meanwhile, the rare earth permanent magnet material has poor obdurability and correspondingly poor shock resistance and impact resistance, so that the application of the material in occasions with higher requirements on shock resistance and impact resistance is limited, for example, in the fields of aeronautical instruments, high-speed motors and the like.
How to improve the toughness of rare earth permanent magnetic materials has become an urgent important issue. At present, most researchers select a mode of adding elements such as Ti, Al, Nb, Ag and the like during smelting or between grains to improve the wettability between a grain boundary phase and grains of the material so as to enhance the bonding strength between the grain boundary phase and the grains and achieve the purpose of improving the mechanical property of the neodymium iron boron permanent magnet alloy.
However, the neodymium iron boron rare earth permanent magnet material is processed and sliced in the production process, and the surface of the cut product is subjected to post-treatment such as grinding, chamfering and the like, and the treatment can generate a large amount of heat on the surface of the product. Although the lubricating liquid and the cooling liquid are protected in the treatment process, the phenomena of quenching and uneven cooling are inevitable, the microstructure of the surface of a product is changed, and the generation of surface residual stress is accompanied. Therefore, in the subsequent processes of barrel plating, carrying, dumping and the like, the phenomenon of edge knocking and corner dropping is probably caused in a large amount by slight collision of products, so that the yield of finished products is greatly reduced, the loss is caused to enterprises, the production cost is increased along with the product, and the serious waste is caused to the originally deficient rare earth resources.
In addition, in the use process of the magnet product, the surface residual stress of the magnet product can also become potential hidden danger, and the personal and property safety of the consumers is threatened. Therefore, it is necessary to eliminate the residual stress on the surface of the magnet product and improve the mechanical properties thereof.
Disclosure of Invention
The invention aims to provide a method for producing a neodymium iron boron rare earth permanent magnet material, which is used for treating a sintered neodymium iron boron blank after machining treatment, so that the mechanical property of the neodymium iron boron rare earth permanent magnet material is improved.
The method for producing the neodymium iron boron rare earth permanent magnet material comprises the following steps: preparing a sintered neodymium iron boron blank, and machining the sintered neodymium iron boron blank; carrying out heat treatment on the sintered neodymium iron boron blank under vacuum; and slowly cooling the sintered neodymium iron boron blank subjected to heat treatment to room temperature under vacuum.
The temperature of the sintered neodymium iron boron blank is 250-450 ℃ when the sintered neodymium iron boron blank is subjected to heat treatment under vacuum, and is preferably 350-450 ℃.
The heat preservation time when the sintered neodymium iron boron blank is subjected to heat treatment in vacuum is preferably 0.5-3.5 hours.
The sintered neodymium iron boron blank after the heat treatment is slowly cooled to the room temperature under the vacuum, the natural cooling is carried out under the vacuum, and the temperature control cooling can also be carried out on the sintered neodymium iron boron blank after the heat treatment at the cooling speed of 50-100 ℃/h.
According to the method for producing the neodymium iron boron rare earth permanent magnet material, the processed sample is subjected to heat treatment before entering the electroplating process, so that residual stress generated on the sample in each processing link can be well eliminated, and the mechanical property of the neodymium iron boron rare earth permanent magnet material is improved.
Drawings
Fig. 1 is a diagram showing the appearance of a test piece after a tumbling impact test, with the heat-treated test piece on the left and the non-heat-treated test piece on the right.
Fig. 2 is a graph showing the weight loss rate of samples treated by different heat treatment processes after the tumbling impact test.
Fig. 3 is a graph of an optimal heat treatment process in accordance with an embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
Firstly, the neodymium iron boron permanent magnet material, for example, the sintered neodymium iron boron blank is cut and polished by conventional machining, and then is prepared into 10 × 10 × 10mm3Size standard sample.
Then, the sample is wrapped by a sheet iron and put into a material box, and heat treatment is carried out in a vacuum sintering furnace. The heat treatment temperature is 250-450 ℃, preferably 350-450 ℃, and the heat preservation time is 0.5-3.5 hours.
Finally, slowly cooling to room temperature. Slow cooling means that after heating and heat preservation, the mixture is not rapidly cooled in the air, airflow, water, oil or solid cooling medium, but the heating is stopped under the condition of keeping vacuum, and the mixture is slowly cooled to the room temperature. The method has the characteristics that the cooling speed is high at the high temperature in the initial stage, the temperature reduction speed is reduced along with the reduction of the temperature in the furnace, and compared with a temperature control cooling method, the method is more reasonable and saves energy. However, if the heat preservation effect of the equipment is not good, or the cooling speed is too fast due to other reasons, for example, the average cooling speed is more than or equal to 100 ℃/h, the cooling speed of 50-100 ℃/h can also be selected to carry out temperature-controlled cooling on the material.
Because the sample is cooled from the sintering temperature to the room temperature (25 ℃) by adopting slow cooling means, the residual stress on the surface of the sample is obviously eliminated and improved.
Samples prepared by processing the same batch of briquettes in the same manner were divided into 16 groups, one group was not heat-treated as a comparative group, and the remaining 15 groups were vacuum-heat-treated under 15 conditions of five sintering temperatures of 250 ℃, 300 ℃, 350 ℃, 400 ℃ and 450 ℃ and three heat-retention times of 2 hours, 2.5 hours and 3 hours, respectively.
Then 30 specimens were selected from each group and weighed, and placed in a cylindrical blender having an internal space of D123.5X 180mm, the rotational speed of the blender was set at 300rpm, and the working time was 30 min. And taking out the samples after the mixer finishes working, cleaning up the samples, weighing, calculating the weight loss rate of the same group of samples before and after the rolling impact test, and simultaneously comparing the samples among groups.
The data show that the heat treatment at different temperatures and different heat preservation times improves the rolling impact weight loss rate of the sample to different degrees, wherein the weight loss rate of the sample subjected to the heat treatment at 350 ℃, 400 ℃ and 450 ℃ is improved obviously, the difference between the weight loss rate of the sample and the weight loss rate of the sample is small, and the influence of the heat preservation time on the weight loss rate of the sample is not very obvious.
Therefore, the conditions of 400 ℃, heat preservation for 2 hours and slow cooling are selected as the optimal heat treatment process. The weight loss rate of the sample subjected to the heat treatment by the process after the rolling impact test is 0.22 percent, which is 0.43 percent lower than the weight loss rate of the sample subjected to the heat treatment without the heat treatment, which is 0.65 percent. The improvement is also quite evident from the appearance, as shown in fig. 1.
Examples
Firstly, the blank block of the neodymium iron boron rare earth permanent magnet material which is produced by the inventor according to the conventional process and is not magnetized is prepared into 10 multiplied by 10mm by two processes of inner circle cutting and double-end grinding3The standard sample of (4), the dimensional deviation is controlled within. + -. 0.1 mm.
Samples prepared from the same batch of briquettes in the same processing mode are divided into 15 groups, and vacuum heat treatment is respectively carried out under 15 conditions formed by combining five sintering temperatures of 250 ℃, 300 ℃, 350 ℃, 400 ℃ and 450 ℃ and three heat preservation times of 2 hours, 2.5 hours and 3 hours. And (3) packing the sample with an iron sheet, putting the packed sample into a material box, and performing heat treatment in a vacuum sintering furnace.
Finally, slow cooling down to room temperature (i.e., 25 ℃).
Then weighing weight m from each 30 samples in each group, then placing the weighed weight m into a cylindrical mixer with internal space of D123.5 multiplied by 180mm, setting the rotating speed of the mixer to be 300rpm, working time to be 30min, taking out the samples after the mixer finishes working, cleaning the samples, weighing the weight m' after the test, calculating the weight loss rate after the rolling impact test according to the following formula, and comparing the weight m between groups.
The weight loss rate is (m-m')/m × 100%
Comparative example
Weighing the same sample as the sample in the embodiment, weighing the sample by weight m, putting the sample into a cylindrical mixer with an internal space of D123.5 multiplied by 180mm, setting the rotating speed of the mixer to be 300rpm, working time to be 30min, taking out the sample after the mixer finishes working, cleaning the sample, weighing the weight m' of the sample after the test, calculating the weight loss rate after the rolling impact test according to the following formula, and comparing the weight loss rate between groups.
The weight loss rate is (m-m')/m × 100%
As shown in fig. 2, compared with the weight loss of the sample without heat treatment process in the comparative example, the weight loss of the sample subjected to heat treatment in the example is improved significantly, and is reduced from the previous 0.65% to 0.22-0.45%, wherein the weight loss of the sample subjected to heat treatment at 350 ℃, 400 ℃ and 450 ℃ is improved relatively better, and the weight loss is 0.22-0.26%, and is basically not much different. In addition, it can be seen from the figure that the influence of the holding time on the weight loss rate of the sample is not very obvious. Therefore, the conditions of heat preservation at 400 ℃ for 2h and slow cooling can be selected as the optimal heat treatment process.
The technical solutions of the present invention have been described in detail through the specific embodiments and examples, but the present invention is not limited thereto. Those skilled in the art can make changes and modifications to the present invention without departing from the purpose of the present invention.
Claims (4)
1. A method for producing a neodymium iron boron rare earth permanent magnet material comprises the following steps:
the method comprises the following steps: preparing a sintered neodymium iron boron blank which is produced according to a conventional process and is not magnetized, and machining the sintered neodymium iron boron blank;
step two: carrying out heat treatment on the sintered neodymium iron boron blank processed in the step one under vacuum, wherein the temperature of the heat treatment is 250-450 ℃, and the heat preservation time is 0.5-3.5 hours;
step three: and slowly cooling the sintered neodymium iron boron blank subjected to heat treatment to room temperature under vacuum.
2. The method for producing the neodymium-iron-boron rare earth permanent magnet material according to claim 1, wherein the temperature of the sintered neodymium-iron-boron blank is 350-450 ℃ when the sintered neodymium-iron-boron blank is subjected to heat treatment under vacuum.
3. The method of claim 1, wherein the sintered nd-fe-b blank after heat treatment is slowly cooled to room temperature under vacuum by natural cooling under vacuum.
4. The method for producing a neodymium-iron-boron rare earth permanent magnet material according to claim 1, characterized in that the sintered neodymium-iron-boron blank after heat treatment is slowly cooled to room temperature under vacuum, and the sintered neodymium-iron-boron blank after heat treatment is cooled at a temperature control speed of 50-100 ℃/h.
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| CN103103442A (en) * | 2013-02-28 | 2013-05-15 | 包头稀土研究院 | Method for preparing neodymium-iron-boron material through main-auxiliary alloy method |
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| CN102039410B (en) * | 2009-10-14 | 2014-03-26 | 三环瓦克华（北京）磁性器件有限公司 | Sintering ageing technology for increasing coercive force of sintered neodymium-iron-boron magnet |
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| CN103103442A (en) * | 2013-02-28 | 2013-05-15 | 包头稀土研究院 | Method for preparing neodymium-iron-boron material through main-auxiliary alloy method |
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| Title |
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| 新型永磁材料的研究;杨金波 等;《中国科学》;20131020;第43卷(第10期);1188-1205 * |
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