CN111562280B - Method for testing carbon content distribution of NdFeB blank - Google Patents
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- CN111562280B CN111562280B CN202010336847.2A CN202010336847A CN111562280B CN 111562280 B CN111562280 B CN 111562280B CN 202010336847 A CN202010336847 A CN 202010336847A CN 111562280 B CN111562280 B CN 111562280B
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Abstract
The invention discloses a testing method for carbon content distribution of a neodymium iron boron blank, and relates to the technical field of neodymium iron boron component analysis. Therefore, the defect that the conventional high-frequency infrared absorption method only aims at random sampling area test and cannot reflect the overall carbon content distribution of the neodymium iron boron blank from top to bottom can be avoided, and an effective characterization means is provided for optimizing the demolding process of neodymium iron boron, controlling the carbon content of the neodymium iron boron blank and improving the uniformity of a final neodymium iron boron product. The test method also has the advantages of controllable quantity of the test surfaces as required, visual and visible test results of the carbon content distribution condition and the like.
Description
Technical Field
The invention relates to the technical field of neodymium iron boron component analysis, in particular to a method for testing carbon content distribution of a neodymium iron boron blank.
Background
The neodymium-iron-boron magnetic material has wide application field, has high requirements on the comprehensive performance, and not only has high coercive force and magnetic energy product, but also has high corrosion resistance and low weightlessness. In the production process of high-performance products, the control of impurity elements is important, wherein the carbon content is the impurity element which is inevitably brought in the use of a release agent in the molding process of sintered NdFeB, and the impurity element has great influence on the performance of the products. The release agent formula contains various carbon-containing substances, the release agent is sprayed into the die, the release agent slowly permeates into the die from the surface of the neodymium iron boron blank, and under the action of gravity, more release agent exists on the lower surface of the neodymium iron boron blank, so that the carbon content is unevenly distributed. After demolding, the neodymium iron boron blank is cut into different sizes according to the requirements of customers, and the uniformity of the distribution of the carbon content of the neodymium iron boron blank can lead to the fact that the consistency of the final product can not be ensured. The carbon content is increased, a carbon-rich phase is formed in a neodymium-rich phase of the magnet, so that the neodymium-rich phase and even a main phase of a local tissue are damaged, and the intrinsic coercivity of the neodymium-iron-boron magnet is reduced; the destructive action loosens the matrix and also reduces the corrosion resistance. The application range of NdFeB is greatly restricted due to the reduction of the product performance, and the service life of related components is influenced.
The existing traditional testing methods such as neodymium iron boron industry standard and the like mainly comprise a high-frequency infrared absorption method for measuring carbon, and after a sample is crushed mechanically, the test is only carried out on a random sampling area, so that the overall carbon content distribution condition of neodymium iron boron blanks with uneven carbon content from top to bottom cannot be reflected. In order to optimize the demolding process of the neodymium iron boron, not only the demolding effect of the product is ensured, but also the carbon content of the neodymium iron boron blank is reduced, the uniformity of the product is improved, and the balance point of the demolding process and the carbon content is sought, so that the searching of a testing method of the carbon content distribution is particularly important.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a testing method for the carbon content distribution of the NdFeB blank, which has the advantages of controllable number of testing surfaces as required, visual testing results and the like.
The technical problems of the invention are realized by the following technical scheme:
a testing method for carbon content distribution of NdFeB blanks comprises the following steps:
firstly, selecting a piece of demolded neodymium iron boron blank which is rectangular, and removing greasy dirt and impurities on the surface;
step two, the neodymium iron boron blank subjected to the step one is placed in an oven for low-temperature drying;
dividing the neodymium iron boron blank subjected to the second step into a plurality of layers of test surfaces, wherein each layer of test surface is a rectangular test surface, sequentially making digital marks of the plurality of layers of test surfaces according to the sequence from top to bottom, taking the pressed surface of the neodymium iron boron blank as a 1 st test surface, and taking the lower surface of the neodymium iron boron blank as the lowest layer, namely an nth test surface, and taking the nearest n test surface as an n-1 th test surface;
step four, starting the NdFeB blank obtained in the step three from the 1 st test surface, and sequentially completing the carbon content test from top to bottom to the n-1 st test surface:
(1) firstly, measuring the height from the 1 st test surface to the lower surface, selecting 5 test points on the 1 st test surface, and taking the average value of the carbon content results of the 5 test points;
(2) immersing the 1 st test surface subjected to the carbon content test in a nitric acid solution downwards, and etching and digesting the 1 st test surface to a digital mark of the 2 nd test surface;
(3) washing the NdFeB blank subjected to the treatment in the step (2) by deionized water, and polishing a test surface in the step (2) to make the test surface flat;
(4) washing the NdFeB blank subjected to the treatment in the step (3) with acetone or absolute ethyl alcohol and drying at a low temperature;
(5) measuring the height from the 2 nd test surface to the lower surface of the NdFeB blank subjected to the treatment in the step (4);
step five, repeating the operation processes of the steps (1) - (5) in the step four, and sequentially carrying out the carbon content test of the next test surface until the carbon content test of the n-1 test surface is completed;
step six, turning over the NdFeB blank subjected to the step five and directly testing the carbon content of an nth test surface, firstly selecting 5 test points on the nth test surface, and then taking the average value of the carbon content results of the 5 test points;
step seven, according to the carbon content test results of all the test surfaces obtained in the step five and the step six, a distribution curve graph of the carbon content in the NdFeB blank along with the change of the height is made;
and step eight, directly observing the carbon content distribution in the NdFeB blank according to the distribution curve graph obtained in the step seven.
In the first step, the neodymium iron boron blank is prepared by sintering and demolding after being pressed and molded in the neodymium iron boron production process.
And in the first step, removing greasy dirt and impurities on the surface of the NdFeB blank by using acetone or absolute ethyl alcohol.
And in the second step, the low-temperature drying temperature is 80-100 ℃ and the time is 10-30 min so as to remove the acetone or the absolute ethyl alcohol.
And in the third step, the pressed surface is the upper surface during pressing and forming in the production of the neodymium iron boron blank.
The carbon content test of each layer of test surface adopts wavelength dispersion type X-ray fluorescence spectrometer (WDX) test, the instrument is equipped with a special crystal for carbon measurement, and nondestructive test is carried out on the test surface.
The 5 test points comprise 1 test point arranged at the intersection point of two diagonals of the rectangular test surface and 4 test points arranged at four midpoint positions of four diagonals respectively connected with the intersection point.
In the fourth step, the nitric acid solution is prepared from concentrated nitric acid and deionized water according to the volume ratio of 1:1, and the depth of the nitric acid solution cannot exceed the digital mark of the next test surface.
And in the fourth step, the residual nitric acid solution is washed by deionized water, and then the test surface is polished by a metallographic polishing machine.
Compared with the prior art, the method has the advantages that the problem of uneven carbon content distribution on the surface and in the inside of the neodymium iron boron blank due to the use of the release agent in the neodymium iron boron production process is considered, the neodymium iron boron blank is uniformly divided into n layers of test surfaces in the vertical direction of the pressing surface, the next test surface is obtained after layer-by-layer testing and nitric acid etching digestion, the non-destructive carbon measurement is carried out on each layer of test surface by adopting WDX through a 5-point test method, and the heights of the layer-by-layer test surface and the lower surface are measured simultaneously, so that the distribution relation between the carbon content and the height of the neodymium iron boron blank is obtained. Therefore, the defect that the conventional high-frequency infrared absorption method only aims at random sampling area test and cannot reflect the overall carbon content distribution of the neodymium iron boron blank from top to bottom can be avoided, and an effective characterization means is provided for optimizing the demolding process of neodymium iron boron, controlling the carbon content of the neodymium iron boron blank and improving the uniformity of a final neodymium iron boron product. The method for testing the carbon content distribution of the NdFeB blank has the advantages of controllable quantity of the test surfaces as required, visual and visible test results of the carbon content distribution condition and the like.
Drawings
Fig. 1 is a schematic structural diagram of a neodymium iron boron blank divided into n layers according to the vertical direction of a pressing surface.
Fig. 2 is a top view of fig. 1 (schematic view of a structure of 5 test point positions).
Fig. 3 is a graph of carbon content distribution versus height for neodymium iron boron billets.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the drawings.
As shown in figures 1-3, 1 is a pressed surface, 2 is a lower surface and 3 is a test point.
A testing method for carbon content distribution of NdFeB blanks comprises the following steps:
firstly, selecting a rectangular neodymium iron boron blank after demoulding, removing greasy dirt and impurities on the surface by using acetone or absolute ethyl alcohol, wherein the neodymium iron boron blank is prepared by sintering and demoulding after compression molding in a neodymium iron boron production process;
step two, the neodymium iron boron blank subjected to the step one is placed in an oven to be dried at a low temperature of 80-100 ℃ for 10-30 min so as to remove acetone or absolute ethyl alcohol;
dividing the neodymium iron boron blank subjected to the second step into a plurality of layers of test surfaces according to the average shown in fig. 1, wherein each layer of test surface is a rectangular test surface, the digital marks of the plurality of layers of test surfaces are sequentially made according to the vertical sequence from top to bottom, the pressed surface 1 of the neodymium iron boron blank is used as a 1 st test surface, the lowest layer is the lower surface 2 of the neodymium iron boron, namely an nth test surface, and the test surface closest to the nth test surface is an n-1 th test surface; wherein, the pressing surface 1 is the upper surface during pressing and forming in the production of neodymium iron boron blanks;
step four, starting the NdFeB blank obtained in the step three from the 1 st test surface, and sequentially completing the carbon content test from top to bottom to the n-1 st test surface:
(1) firstly, measuring the height from the 1 st test surface to the lower surface 2 by using a vernier caliper, selecting 5 test points 3 on the 1 st test surface, and taking the average value of the carbon content results of the 5 test points 3;
(2) immersing the 1 st test surface subjected to the carbon content test in a nitric acid solution downwards, and etching and digesting the 1 st test surface to a digital mark of the 2 nd test surface;
(3) washing the neodymium iron boron blank subjected to the treatment in the step (2) with deionized water to remove residual nitric acid solution, and polishing a 2 nd test surface by a metallographic polishing machine to be flat;
(4) washing the NdFeB blank subjected to the treatment in the step (3) with acetone or absolute ethyl alcohol and drying at a low temperature;
(5) measuring the height from the 2 nd test surface of the NdFeB blank subjected to the treatment (4) to the lower surface 2 by adopting a vernier caliper;
step five, repeating the operation processes of the steps (1) - (5) in the step four, sequentially carrying out the carbon content test of the next test surface until the carbon content test of the n-1 test surface is completed,
step six, turning over the NdFeB blank subjected to the step five and directly testing the carbon content of an nth test surface, firstly selecting 5 test points 3 on the nth test surface, and then taking the average value of the carbon content results of the 5 test points 3;
step seven, according to the carbon content test results of all the test surfaces obtained in the step five and the step six, a distribution curve graph of the carbon content in the neodymium iron boron blank along with the change of the height is made as shown in fig. 3;
and step eight, directly observing the carbon content distribution in the NdFeB blank according to the distribution curve graph obtained in the step seven.
Meanwhile, in the test step, the carbon content of each layer of test surface is tested by adopting a wavelength dispersion type X-ray fluorescence spectrometer (WDX), and the instrument is provided with a special crystal for carbon measurement to perform nondestructive test on the test surface.
The 5 test points 3 are shown in fig. 2, and include 1 test point 3 arranged at the intersection point of two diagonals of the rectangular test surface, and 4 test points 3 arranged at four midpoint positions of four diagonals respectively connected with the intersection point.
In addition, in the fourth step, the nitric acid solution is prepared from concentrated nitric acid and deionized water according to the volume ratio of 1:1, and the depth of the nitric acid solution cannot exceed the digital mark of the next test surface.
The invention is further illustrated by the following three specific examples:
example 1
Selecting a piece of demolded neodymium iron boron blank, removing greasy dirt and impurities on the surface by using acetone, and then placing the neodymium iron boron blank in an oven for low-temperature drying at 80 ℃ for 20min to remove the acetone on the surface; the method comprises the steps of taking a pressed surface 1 of a neodymium iron boron blank as a 1 st test surface, dividing the neodymium iron boron blank into 5 layers averagely according to test requirements, sequentially making 1-5 numerical marks on the side surface according to the sequence from top to bottom, wherein the lowest layer is a lower surface 2 of the neodymium iron boron, namely the 5 th test surface, and the test surface closest to the 5 th test surface is a 4 th test surface; measuring the height from the 1 st test surface to the lower surface 2 by adopting a vernier caliper; sequentially testing the carbon content from a 1 st test surface by adopting a wavelength dispersion type X-ray fluorescence spectrometer (WDX), firstly taking 5 test points on the 1 st test surface, measuring the carbon content result of the 1 st test surface, taking the average value of the test points, then immersing the 1 st test surface downwards into a nitric acid solution, wherein the depth of the solution cannot exceed the digital mark of a 2 nd test surface, etching and resolving the solution to the digital mark of the 2 nd test surface, cleaning the test surface by deionized water to remove residual nitric acid, polishing the 2 nd test surface by a metallographic polishing machine to level the test surface, cleaning the polished neodymium iron boron blank by acetone and drying the polished neodymium iron boron blank at 80 ℃ for 20min, and finally measuring the height from the 2 nd test surface to the lower surface 2; in this way, the carbon content test of the 3 rd test surface and the 4 th test surface can be sequentially carried out by repeating the operation process, and the carbon content test of the 5 th test surface is that after the carbon content test of the 4 th test surface is completed, the NdFeB blank is turned over to directly carry out the carbon content test of the 5 th test surface, or 5 test points 3 are selected on the 5 th test surface, and then the carbon content results of the 5 test points are averaged; finally, a distribution curve graph of the carbon content in the NdFeB blank along with the change of the height can be made.
Example 2
Selecting a piece of demolded neodymium iron boron blank, removing greasy dirt and impurities on the surface by using acetone, and then placing the neodymium iron boron blank in an oven for low-temperature drying at 90 ℃ for 10min to remove the acetone on the surface; the method comprises the steps of taking a pressed surface 1 of a neodymium iron boron blank as a 1 st test surface, dividing the neodymium iron boron blank into 6 layers averagely according to test requirements, sequentially making 1-6 numerical marks on the side surface according to the sequence from top to bottom, wherein the lowest layer is a lower surface 2 of the neodymium iron boron, namely the 6 th test surface, and the test surface closest to the 6 th test surface is a 5 th test surface; measuring the height from the 1 st test surface to the lower surface 2 by adopting a vernier caliper; sequentially testing the carbon content from a 1 st test surface by adopting a wavelength dispersion type X-ray fluorescence spectrometer (WDX), firstly taking 5 test points on the 1 st test surface, measuring the carbon content result of the 1 st test surface, taking the average value of the test points, then immersing the 1 st test surface downwards into a nitric acid solution, wherein the depth of the solution cannot exceed the digital mark of a 2 nd test surface, etching and resolving the solution to the digital mark of the 2 nd test surface, cleaning the test surface by deionized water to remove residual nitric acid, polishing the 2 nd test surface by a metallographic polishing machine to level the test surface, cleaning the polished neodymium iron boron blank by acetone and drying the polished neodymium iron boron blank at 90 ℃ for 10min, and finally measuring the height from the 2 nd test surface to the lower surface 2; in this way, the carbon content test of the 3 rd, 4 th and 5 th test surfaces can be sequentially carried out by repeating the operation process, and the carbon content test of the 6 th test surface is that after the carbon content test of the 5 th test surface is completed, the NdFeB blank is turned over to directly carry out the carbon content test of the 6 th test surface, or 5 test points 3 are selected on the 6 th test surface, and then the carbon content results of the 5 test points are averaged; finally, a distribution curve graph of the carbon content in the NdFeB blank along with the change of the height can be made.
Example 3
Selecting a rectangular neodymium iron boron blank after demolding, removing oil stains and impurities on the surface by using absolute ethyl alcohol, and then placing the blank in an oven for low-temperature drying at 100 ℃ for 30min to remove the absolute ethyl alcohol on the surface; the method comprises the steps of taking a pressed surface 1 of a neodymium iron boron blank as a 1 st test surface, dividing the neodymium iron boron blank into 7 layers on average according to test requirements, sequentially making 1-7 numerical marks on the side surface according to the sequence from top to bottom, wherein the lowest layer is a lower surface 2 of the neodymium iron boron, namely the 7 th test surface, and the test surface closest to the 7 th test surface is a 6 th test surface; measuring the height from the 1 st test surface to the lower surface 2 by adopting a vernier caliper; sequentially testing the carbon content from a 1 st test surface by adopting a wavelength dispersion type X-ray fluorescence spectrometer (WDX), firstly taking 5 test points on the 1 st test surface, measuring the carbon content result of the 1 st test surface, taking the average value of the test points, then immersing the 1 st test surface downwards into a nitric acid solution, wherein the depth of the solution cannot exceed the digital mark of a 2 nd test surface, etching and resolving the solution to the digital mark of the 2 nd test surface, cleaning the solution by deionized water to remove residual nitric acid, polishing the 2 nd test surface by a metallographic polishing machine to level the 2 nd test surface, cleaning the polished neodymium iron boron blank by absolute ethyl alcohol and drying the polished neodymium iron boron blank at 100 ℃ for 30min, and finally measuring the height from the 2 nd test surface to the lower surface 2; in this way, the carbon content test of the 3 rd, 4 th, 5 th and 6 th test surfaces can be sequentially carried out by repeating the operation process, the carbon content test of the 7 th test surface is that after the carbon content test of the 6 th test surface is completed, the NdFeB blank is turned over to directly carry out the carbon content test of the 7 th test surface, or 5 test points 3 are selected on the 7 th test surface, and then the carbon content results of the 5 test points are averaged; finally, a distribution curve graph of the carbon content in the NdFeB blank along with the change of the height can be made.
The foregoing is merely a specific embodiment of the present invention, and it should be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention. It should also be appreciated that various changes and modifications to the method will occur to those skilled in the art upon reading the teachings of the present invention and, if in the equivalent form, are likewise within the scope of the appended claims.
Claims (8)
1. A method for testing carbon content distribution of NdFeB blanks is characterized by comprising the following steps:
firstly, selecting a piece of demolded neodymium iron boron blank which is rectangular, and removing greasy dirt and impurities on the surface;
step two, the neodymium iron boron blank subjected to the step one is placed in an oven for low-temperature drying;
dividing the neodymium iron boron blank subjected to the second step into a plurality of layers of test surfaces, wherein each layer of test surface is a rectangular test surface, sequentially making digital marks of the plurality of layers of test surfaces according to the sequence from top to bottom, taking a pressing surface (1) of the neodymium iron boron blank as a 1 st test surface, and taking the lower surface (2) of neodymium iron boron as the lowest layer, namely an nth test surface, and taking the test surface closest to the nth test surface as an n-1 th test surface;
step four, starting the NdFeB blank obtained in the step three from the 1 st test surface, and sequentially completing the carbon content test from top to bottom to the n-1 st test surface:
(1) firstly, measuring the height from the 1 st test surface to the lower surface (2), selecting 5 test points (3) on the 1 st test surface, and taking the average value of the carbon content results of the 5 test points (3);
(2) immersing the 1 st test surface subjected to the carbon content test in a nitric acid solution downwards, and etching and digesting the 1 st test surface to a digital mark of the 2 nd test surface;
(3) washing the NdFeB blank subjected to the treatment in the step (2) by deionized water, and polishing a test surface in the step (2) to make the test surface flat;
(4) washing the NdFeB blank subjected to the treatment in the step (3) with acetone or absolute ethyl alcohol and drying at a low temperature;
(5) measuring the height from the 2 nd test surface of the NdFeB blank subjected to the treatment of (4) to the lower surface (2);
step five, repeating the operation processes of the steps (1) - (5) in the step four, and sequentially carrying out the carbon content test of the next test surface until the carbon content test of the n-1 test surface is completed;
step six, turning over the NdFeB blank subjected to the step five and directly testing the carbon content of an nth test surface, firstly selecting 5 test points (3) on the nth test surface, and then taking the average value of the carbon content results of the 5 test points (3);
step seven, according to the carbon content test results of all the test surfaces obtained in the step five and the step six, a distribution curve graph of the carbon content in the NdFeB blank along with the change of the height is made;
step eight, directly observing the carbon content distribution in the NdFeB blank according to the distribution curve graph obtained in the step seven;
the 5 test points (3) comprise 1 test point (3) arranged at the intersection point of two diagonals of the rectangular test surface, and 4 test points (3) arranged at the middle points of four diagonals respectively connected with the intersection point.
2. The method for testing carbon content distribution of a neodymium iron boron blank according to claim 1, wherein in the step one, the neodymium iron boron blank is manufactured by sintering and demolding after being pressed and molded in a neodymium iron boron production process.
3. The method for testing carbon content distribution of neodymium iron boron billets according to claim 1, wherein the step one is characterized in that acetone or absolute ethyl alcohol is used for removing greasy dirt and impurities on the surfaces of the neodymium iron boron billets.
4. The method for testing carbon content distribution of a neodymium iron boron blank according to claim 1, wherein the low-temperature drying temperature in the second step is 80-100 ℃ for 10-30 min to remove acetone or absolute ethyl alcohol.
5. The method for testing carbon content distribution of a neodymium iron boron blank according to claim 1, wherein the pressing surface (1) in the third step is an upper surface of the neodymium iron boron blank during pressing and forming in production.
6. The method for testing the carbon content distribution of the NdFeB blank according to claim 1, wherein the carbon content of each layer of testing surface is tested by a wavelength dispersion type X-ray fluorescence spectrometer WDX, and the instrument is provided with a special crystal for testing carbon, so that the testing surface is subjected to nondestructive testing.
7. The method for testing carbon content distribution of neodymium iron boron billets according to claim 1, wherein in the fourth step, the nitric acid solution is prepared by concentrated nitric acid and deionized water according to a volume ratio of 1:1, and the depth of the nitric acid solution cannot exceed the digital mark of the next testing surface.
8. The method for testing carbon content distribution of neodymium iron boron billets according to claim 1, wherein in the fourth step, deionized water is used for washing away residual nitric acid solution, and a metallographic polishing machine is used for polishing the test surface.
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| JP2790109B2 (en) * | 1996-02-02 | 1998-08-27 | 日本電気株式会社 | Sample preparation method for component analysis from the back side |
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