TWI834297B - Recycled magnet and waste magnet regeneration method for improving magnetic characteristics the same - Google Patents

Abstract

A recycled magnet and a waste magnet regeneration method for improving magnetic characteristics the same are provided. The method includes following steps: providing a waste magnet; performing a pre-treatment step to the waste magnet; performing a normal temperature hydrogen absorption crushing step and a normal temperature vacuum dehydrogenation step to the waste magnet after the pre-treatment step, so that the waste magnet forms a coarse waste magnet powder; mixing the coarse waste magnet powder that is subjected to a stream grinding step with the auxiliary alloy powder, or mixing the coarse waste magnet powder with the auxiliary alloy powder before the stream grinding step to form a regenerated magnet mixture; performing a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step after an orientation and forming step is performed to the regenerated magnet mixture, and performing a vacuum sintering step and an aging treatment step after the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step, to obtain a recycled magnet.

Description

Regenerated magnets and waste magnet recycling methods to improve magnetic properties

The present invention relates to regenerated magnets and a waste magnet recycling and regeneration method for improving magnetic properties. In particular, it relates to a regenerated magnet used in neodymium iron boron waste magnets and a waste magnet recycling and regeneration method for improving magnetic properties.

With the increasing advancement of science and technology, various types of electronic and electrical equipment often require the use of materials such as magnets. Among them, rare earth magnets are a new star in the world of hard magnetic materials. Their excellent properties enable them to quickly replace old magnets in high-performance applications and inspire people to continue to develop new applications.

NdFeB permanent magnet material is an intermetallic compound formed by rare earth metal elements such as neodymium and iron element. It has excellent magnetic properties and is one of the most important rare earth functional materials. In recent years, the application fields of NdFeB permanent magnet materials have become increasingly widespread, and have expanded from the original defense and military industries such as aviation, aerospace, navigation, and weapons to instruments, meters, energy, transportation, medical equipment, electronic power, communications, and other more advanced fields. For a wide range of civilian high-tech fields.

The production of NdFeB magnets accounts for about 25% of the total demand for rare earths. As applications continue to increase, the demand for rare earths increases year by year. Since the rare earth mining and refining process has a huge impact on the environment, how can NdFeB magnets be properly manufactured? The recycling of waste materials will contribute to the sustainable development of NdFeB magnets, reduce resource consumption, and thus reduce environmental harm.

Generally speaking, NdFeB magnet scrap recycling directly adds a small amount of alloy to make new magnets. The recycling of NdFeB magnets is the lowest carbon emission method, and the cost of recycling and remanufacturing is also the lowest. However, nitrides, oxides, and carbides will continue to be produced during the magnet remanufacturing process. After multiple cycles of regeneration, nitrides, oxides, and carbides will continue to accumulate in the regenerated magnet, causing the magnet's properties to decrease.

Furthermore, when regenerating magnets made from waste magnets using known regeneration methods, the regenerated magnets at various points in the same blank have a problem of insufficient magnetic uniformity.

Therefore, it is necessary to provide a waste magnet recovery and regeneration method that regenerates magnets and improves magnetic properties to solve the problems existing in conventional technologies.

One purpose of the present invention is to provide a waste magnet recycling and regeneration method for regenerating magnets and improving magnetic properties, aiming to overcome the continuous generation of oxides during the process of remanufacturing magnets, and the oxides will continue to accumulate in the regenerated magnets after multiple cycles of regeneration. Causes the problem of reduced magnet properties to ensure the properties of regenerated magnets.

Another object of the present invention is to provide a waste magnet recycling and regeneration method for regenerating magnets and improving magnetic properties, so that the magnet properties of the regenerated magnets at each point of the same blank after the waste magnets are regenerated are uniform.

In order to achieve the above purpose, the present invention provides a method for recycling and regenerating waste magnets with improved magnetic properties, which includes the following steps: providing a waste magnet; performing a pre-treatment step on the waste magnet; and treating the waste magnet after the pre-treatment step. Carry out a normal temperature hydrogen absorption crushing step and a normal temperature vacuum dehydrogenation step to form a waste magnet coarse powder from the waste magnet; perform an air flow crushing step to the waste magnet coarse powder and then mix it with an auxiliary alloy powder, or mix the waste magnet powder with an auxiliary alloy powder. The coarse magnet powder and an auxiliary alloy powder are mixed and then subjected to an airflow pulverization step to form a regenerated magnet mixture, wherein the weight ratio of the regenerated magnet main alloy powder and the auxiliary alloy powder is between 90:10 and 99.5:0.5. Proportional mixing; after performing an alignment forming step on the regenerated magnet mixture, performing a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step, and after the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step A vacuum sintering step and an aging treatment step are performed to obtain a regenerated magnet.

In one embodiment of the present invention, the high-temperature vacuum dehydrogenation step includes the following steps: making a blank made of the regenerated magnet mixture, raising the blank to a first predetermined temperature at room temperature and then performing a vacuum evacuation. The dehydrogenation step is to maintain the temperature at the first predetermined temperature for a first temperature holding time, wherein the first predetermined temperature is 200°C to 350°C and the temperature holding time is more than 10 minutes.

In an embodiment of the present invention, the predetermined temperature is 250°C to 300°C and the temperature holding time is more than 30 minutes.

In one embodiment of the present invention, the argon partial pressure hydrogenation step includes the following steps: after the high-temperature vacuum dehydrogenation step, stop vacuuming and inject argon gas to reach an argon partial pressure, wherein the argon partial pressure The pressure is 0.1 to 0.98 atmospheres; continue to heat up to 360 to 440°C and inject hydrogen, where the hydrogen injection amount is 0.001 to 0.3 mol/kg of blank weight; and heat up to the second predetermined temperature and maintain the temperature for a second holding time , wherein the second predetermined temperature is 560 to 600°C and the second temperature holding time is more than 10 minutes.

In one embodiment of the present invention, the argon partial pressure is 0.7 to 0.9 atmospheres, the hydrogen injection amount is 0.01 to 0.1 mol/kg blank weight, and the second predetermined temperature is 580 to 590°C and the second holding time is 0.01 to 0.1 mol/kg blank weight. Warming time is more than 30 minutes.

In one embodiment of the present invention, mixing the waste magnet coarse powder with an auxiliary alloy powder and then performing the airflow crushing step further includes: adding 0.02 to 0.3 wt% based on the weight percentage of the total powder amount being 100wt%. Organic additives.

In one embodiment of the present invention, the vacuum degree of the room temperature vacuum dehydrogenation step is less than 1000 Pascals.

In an embodiment of the present invention, the vacuum degree of the normal temperature vacuum dehydrogenation step is 100 Pascal or less.

In one embodiment of the present invention, the composition of the auxiliary alloy powder is Ra(Co,Fe)b(Cu,Al,Ga)c, where R includes lanthanum, cerium, indium, neodymium, gallium, phosphorus, dysprosium, and The mixture thereof, wherein the weight percentage of the auxiliary alloy powder is 100, a is between 70wt% and 99.8wt, b is between 0.1wt% and 30wt%, and c is between 0.1wt% and 30wt%.

The present invention also provides a regenerated magnet manufactured by the waste magnet recycling and regeneration method for improving magnetic properties as described above, in which the maximum magnetic energy product (BHmax) of several regenerated magnets made from the same blank is 41.66 MGOe or more. The intrinsic coercive force value between the regenerated magnets is 18.18 kOe or more, and the difference (△iHc) between the regenerated magnets is less than 2.5%.

The waste magnet recycling and regeneration method of the present invention that improves magnetic properties adds a normal temperature hydrogen absorption crushing step and a normal temperature vacuum dehydrogenation step before the air flow crushing step, and implements a normal temperature vacuum dehydrogenation step and a normal temperature vacuum dehydrogenation step after the normal temperature hydrogen absorption crushing step. The hydrogen in part of the powder can be removed in advance. The advantage is that it can avoid the hydrogen overflow in the subsequent process and cause the blank to break. After the blank enters the sintering furnace, the vacuum speed can be accelerated and the sintering time can be shortened. Furthermore, after the blank enters the sintering furnace, vacuum dehydration is performed at 200°C to 350°C. The advantage is that the organic additives on the surface of the magnetic powder can be vaporized and the hydrogen overflowing from the powder can assist in rapid vacuum removal, allowing the organic additives to be vaporized. The residual amount of additives is low, and the oxygen content of the sintered blank can be reduced when this reaction is carried out in a vacuum compared to an argon partial pressure atmosphere. In addition, after the vacuum dehydrogenation step, the sintering furnace is stopped to evacuate, argon gas is injected, and an appropriate amount of hydrogen is added. The advantage is that the amount of hydrogen reduction reaction inside and outside the blank is similar, which can reduce the distance between the magnet located in the center of the blank and the distance between the magnet located in the center of the blank. The difference in the intrinsic coercivity value (Hcj) of the magnet at the corner of the embryo.

In order to make the above and other objects, features, and advantages of the present invention more apparent and understandable, preferred embodiments of the present invention will be described in detail below along with the accompanying drawings. Furthermore, the directional terms mentioned in the present invention include, for example, up, down, top, bottom, front, back, left, right, inside, outside, side, peripheral, central, horizontal, transverse, vertical, longitudinal, axial, Radial, uppermost or lowermost, etc., are only directions with reference to the attached drawings. Therefore, the directional terms used are to illustrate and understand the present invention, but not to limit the present invention.

As used herein, reference to a numerical range of a variable is intended to mean that the variable is equal to any value within the range. Therefore, for a variable that is not continuous, the variable is equal to any integer value within the range of values, including the endpoints of the range. Similarly, for a variable that is continuous, the variable is equal to any real value within the range of values, including the endpoints of the range. As an example, and not as a limitation, a variable described as having a value between 0-2 takes on the values of 0, 1, or 2 if the variable itself is discontinuous; whereas if the variable itself is continuous, it takes on the values of 0.0, 0.1, A value of 0.01, 0.001, or any other real value ≥0 and ≤2.

Unless there is a special restriction on the article, "a" and "the" can refer to single or plural persons. The numbers used in the steps are only used to mark the steps for ease of explanation, but are not used to limit the order and implementation manner. Furthermore, the words "include", "include", "have", "contain", etc. used in this article are all open terms, which mean including but not limited to.

Referring to Figure 1, an embodiment of the present invention proposes a waste magnet recycling and regeneration method that improves magnetic properties, including the following steps: (S100) providing a waste magnet; (S200) performing a pre-processing step on the waste magnet; (S300) The waste magnet after the pre-treatment step is subjected to a normal temperature hydrogen absorption crushing step and a normal temperature vacuum dehydrogenation step, so that the waste magnet forms a waste magnet coarse powder; (S400) the waste magnet coarse powder is subjected to an airflow pulverization step and then mixed with an auxiliary alloy powder, or the waste magnet coarse powder and an auxiliary alloy powder are mixed and then subjected to an airflow pulverization step to form a regenerated magnet mixture, wherein the regenerated magnet main alloy powder and the auxiliary alloy powder are by weight Mix in a ratio between 90:10 and 99.5:0.5; (S500) After performing an alignment forming step on the regenerated magnet mixture, perform a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step, and After the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step, a vacuum sintering step and an aging treatment step are performed to obtain a regenerated magnet.

It should be noted that the alloy composition of the waste magnet in the embodiment of the present invention is (Nd-Pr) ₃₁ Dy _1.5 Co _1.2 Cu _0.15 Al _0.45 B _0.98 Fe _bal as an example. A person of ordinary skill in the technical field to which the present invention belongs can change the alloy composition of the waste magnet according to needs. In other words, the present invention is applicable to the regeneration of rare earth magnets of various compositions.

In this embodiment, the pretreatment step includes the following steps: performing a demagnetization step on the waste magnet; performing an organic removal step on the waste magnet; performing a surface cleaning step on the waste magnet; and performing a surface cleaning step on the waste magnet. Part of the plating removal step.

Optionally, after the pre-treatment step, the waste magnet is subjected to a mechanical crushing step. The mechanical crushing step, for example, crushes the waste magnet into particles smaller than 5.6 mm.

Optionally, after the mechanical crushing step, the waste magnet is subjected to a normal temperature hydrogen crushing step, so that the waste magnet is crushed into smaller particles. Compared with the known hydrogen crushing step, after the hydrogen crushing step proposed by the present invention, a normal temperature vacuum dehydrogenation step is also performed. Optionally, the normal temperature hydrogen crushing step is to allow the waste magnet to absorb hydrogen at room temperature for more than 2 hours. Optionally, the vacuum degree of the normal temperature vacuum dehydrogenation step is less than 1000 Pascals. Preferably, the vacuum degree of the normal temperature vacuum dehydrogenation step is less than 100 Pascals.

It should be noted that the room temperature referred to in this article is a temperature that does not require additional heat source heating, for example, the temperature is 10°C to 35°C.

In some embodiments, after the normal temperature hydrogen absorption crushing step and the normal temperature vacuum dehydrogenation step, the hydrogen crushed waste magnet is sieved through a mesh #28 mesh so that the electroplating layer remains on the screen, and then remove the electroplating layer remaining on the screen. Next, the waste magnet coarse powder that has passed through the No. 28 mesh screen is subjected to the airflow crushing step. In this embodiment, the diameter of the classifying wheel used in the airflow crushing step is 130 mm, the rotating speed of the classifying wheel is 3600 RPM, and the crushing pressure is 0.7MPa.

It should be noted that the coarse waste magnet powder can be mixed with an auxiliary alloy powder after the air flow pulverization step, or the coarse waste magnet powder and the auxiliary alloy powder can be mixed before the air flow pulverization step is performed to form a Regenerated magnet mixture, wherein the regenerated magnet main alloy powder and the auxiliary alloy powder are mixed in a weight ratio between 90:10 and 99.5:0.5. It should be understood that the mixing ratio of the recycled magnet main alloy powder and the auxiliary alloy powder can also be adjusted according to the requirements of the final product.

Optionally, the composition of the auxiliary alloy powder is Ra(Co,Fe)b(Cu,Al,Ga)c, where R includes lanthanum, cerium, phosphonium, neodymium, gallium, phosphorus, dysprosium, and mixtures thereof, where Based on the weight percentage wt% of the auxiliary alloy powder being 100, a is between 70wt% and 99.8wt, b is between 0.1wt% and 30wt%, and c is between 0.1wt% and 30wt%. It should be understood that the composition of the auxiliary alloy powder can be adjusted according to the requirements of the final product.

In one embodiment, when the regenerated magnet main alloy powder and the auxiliary alloy powder are mixed, an organic additive can be added, wherein the organic additive is a hydrocarbon or ester additive, based on the weight percentage of the total powder amount of 100wt%. , the added amount of the organic additive is 0.02 to 0.3wt%.

Then, optionally, the regenerated magnet mixture is processed into a regenerated magnet blank, and an alignment step is performed on the regenerated magnet blank.

The regenerated magnet blank after the alignment step undergoes a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step. The high-temperature vacuum dehydrogenation step includes the following steps: using the regenerated magnet blank made from the regenerated magnet mixture, raising the regenerated magnet blank to a first predetermined temperature at room temperature and then performing a vacuum dehydrogenation step; And the temperature is maintained at the first predetermined temperature for a first temperature holding time, wherein the first predetermined temperature is 200°C to 350°C and the temperature holding time is more than 10 minutes. Preferably, the predetermined temperature is 250°C to 300°C and the temperature holding time is more than 30 minutes. In one embodiment, the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step are performed in a sintering furnace. It should be noted that after the regenerated magnet blank is put into the sintering furnace and vacuumed and dehydrogenated at 200°C-350°C, the organic additives on the surface of the magnetic powder can be vaporized and can overflow from the powder and be vacuumed with the assistance of hydrogen. Rapid removal results in low residual amounts of organic additives. This stage of the reaction is carried out under vacuum. Compared with the known technology, which only allows the blank to be sintered in an atmosphere of partial pressure of argon, the oxygen content of the sintered regenerated magnet blank can be reduced. It is worth mentioning that the setting of the first predetermined temperature is related to the boiling point of the organic additive, and the general range is between 200 and 350°C.

After the high-temperature vacuum dehydrogenation step is completed, the argon partial pressure hydrogenation step is performed. In one embodiment, the vacuum of the sintering furnace is stopped, argon gas is injected, and an appropriate amount of hydrogen gas is added. Optionally, the argon partial pressure hydrogenation step includes the following steps: after the high temperature vacuum dehydrogenation step, stop vacuuming and inject argon gas to reach an argon partial pressure, wherein the argon partial pressure is 0.1 to 0.98 Atmospheric pressure; continue to inject hydrogen when the temperature reaches 360 to 440°C, in which the hydrogen injection amount is 0.001 to 0.3 mol/kg of blank weight; and heat up to the second predetermined temperature and maintain the temperature for a second temperature holding time, in which the first The second predetermined temperature is 560 to 600°C and the second temperature holding time is more than 10 minutes. Preferably, the argon partial pressure is 0.7 to 0.9 atmospheres, the hydrogen injection amount is 0.01 to 0.1 mol/kg blank weight, and the second predetermined temperature is 580 to 590°C and the second temperature holding time is 30 minutes or more. It should be noted that adding argon gas and adding an appropriate amount of hydrogen can make the amount of hydrogen reduction reaction inside and outside the blank similar, which can reduce the intrinsic coercive force value (Hcj) of the magnet located in the center of the blank and the magnet located in the corner of the blank. ) difference.

After the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step, a vacuum sintering step and an aging treatment step are performed to obtain a regenerated magnet. In one embodiment, a vacuum evacuation step is performed after the high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step.

Next, please refer to Figures 2A and 2B. Figure 2A shows a schematic diagram of the magnet distribution after recycling the NdFeB magnet waste and directly adding a small amount of alloy to make a new magnet blank 10 and then sintering it. Figure 2B shows a schematic diagram of the magnet distribution of the NdFeB magnet. A schematic exploded view of the magnet distribution after boron magnet waste recycling is directly added with a small amount of alloy to make a new magnet blank 10 and then sintered. Table 1 below shows the magnetic characteristics analysis of the magnets that were sintered after recycling NdFeB magnet waste and directly adding a small amount of alloy to make new magnet blanks (without using the method of the present invention). Magnet 101 is located at magnet blank 10 in Figure 1 On the left side of the center, the magnet 102 is located in the center of the magnet blank 10 in Figure 1 , the magnet 103 is located in the corner of the magnet blank 10 in Figure 1 , and the magnet 104 is located in the middle of the outer side of the magnet blank 10 in Figure 1 . According to the analysis results, there is a significant difference in the intrinsic coercive force Hcj value of the magnet 102 located in the center of the blank and the magnet 103 located in the corner of the blank (the difference is 6.2%). [Table 1] Test piece Residual magnetism Br (kGs) Intrinsic coercivity Hcj (kOe) Maximum magnetic energy product (BH)max (MGOe) BHH (sum of BHmax+iHc) Demagnetization curve rectangularity Hk/Hcj Density(g/cc) Magnet 101 14.57 15.47 52.26 67.73 0.967 7.572 Magnet 102 14.59 16.04 52.46 68.5 0.980 7.568 Magnet 103 14.57 15.05 52.01 67.06 0.960 7.578 Magnet 104 14.61 15.68 52.53 68.21 0.948 7.585

Several examples and comparative examples will be listed below to illustrate the detailed process differences between the method of the present invention and the comparative examples. It should be noted that the embodiments listed here are only intended to illustrate the present invention by way of example and are not intended to limit the scope of rights of the present invention. The scope of rights of the present invention should be based on the scope of the attached patent application.

Refer to Table 2, which shows the detailed process conditions of Comparative Example 1, Comparative Example 2, Example 1 and Example 2. Comparative Example 1, Comparative Example 2, Example 1 and Example 2 use waste magnets with the same alloy composition ((Nd-Pr) ₃₁ Dy _1.5 Co _1.2 Cu _0.15 Al _0.45 B _0.98 Fe _bal . Comparative Example 1 is used for comparison. Example 2, Example 1 and Example 2 regenerated waste magnet. Comparative Example 2 goes through the steps of the regeneration method in Table 1, but does not perform the above-mentioned normal temperature hydrogen absorption crushing step, normal temperature vacuum dehydrogenation step, high temperature vacuum dehydrogenation step and Regenerated magnets produced by the argon partial pressure hydrogenation step. In addition to the same steps as the waste magnet recovery and regeneration method for improving magnetic properties in Comparative Example 2, Examples 3 and 4 additionally carry out the above-mentioned normal temperature hydrogen absorption crushing step, The regenerated magnet is made from the normal temperature vacuum dehydrogenation step, the high temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step. In addition, the normal temperature hydrogen absorption crushing step and the normal temperature vacuum dehydrogenation step of Example 3 are to absorb hydrogen at room temperature for 2 hours. , and dehydrogenate at room temperature to a vacuum degree of 60 Pascal; the high-temperature vacuum dehydrogenation step is to heat to 300°C under vacuum and hold the temperature for 40 minutes; and the high-temperature vacuum dehydrogenation step of Example 4 is to heat to 270°C under vacuum. And keep the temperature for 60 minutes. The normal temperature hydrogen absorption crushing step and the normal temperature vacuum dehydrogenation step of Example 3 are to absorb hydrogen at room temperature for 2 hours, and dehydrogenate at room temperature to a vacuum degree of 60 Pascal; the argon partial pressure hydrogenation step Set the argon partial pressure to 0.8 atmospheres, add hydrogen after heating to 400°C, and add hydrogen in an amount of 0.015 mol/kg of blank, continue to heat to 590°C and maintain the temperature for 60 minutes; the argon partial pressure in Example 4 is added In the hydrogen step, the partial pressure of argon is set to 0.7 atmosphere. After heating to 400°C, hydrogen is added. The amount of hydrogen added is 0.05 mol/kg of blank, and the heating is continued to 590°C and maintained for 60 minutes. [Table 2] Comparative example 1 Comparative example 2 Example 1 Example 2 Process sequence Waste magnet prior art Regeneration method using the present invention 1 Regeneration method 2 using the present invention Waste magnet alloy composition (Nd-Pr)31Dy1.5Co1.2Cu0.15Al0.45B0.98Febal (wt%) Waste magnet pre-treatment Demagnetization, organic matter removal, surface cleaning, partial plating layer removal mechanical crushing Crushed waste magnets to less than 5.6 mm Hydrogen fragmentation Absorb hydrogen at room temperature for 2 hours without dehydrogenation Absorb hydrogen at room temperature for 2 hours, and dehydrogenate at room temperature to a vacuum degree of 60 Pascals Screening and separation of electroplated layers Pass through the mesh #28 screen and remove the electroplating layer on the screen. jet crushing The diameter of the classifying wheel is 130 mm, the rotating speed of the classifying wheel is 3600RPM, and the crushing pressure is 0.7 MPa. Auxiliary alloy powder mixing (Nd _0.8 Pr _0.5 ) ₉₀ (Fe _0.5 Co _0.5 ) ₈ Ga ₂ (wt%) Mixing ratio 97.5:2.5wt% (waste magnet powder: auxiliary alloy powder) Additive mix Ester additive 0.1wt% Magnetic field forming blank size 60x50x40 (alignment direction) Magnetic field forming density 4.0 4.0 4.0 High temperature vacuum dehydrogenation step The high-temperature vacuum dehydrogenation step and the argon partial pressure hydrogenation step are not used. Only argon gas is introduced to a partial pressure of 0.9 atmospheres and the temperature is maintained at 590°C for 60 minutes. Vacuum 300℃ for 40 minutes Vacuum 270℃ for 60 minutes Argon partial pressure hydrogenation step The argon partial pressure is 0.8 atmosphere and the blank is kept at 590°C for 60 minutes at 400°C with a hydrogen addition of 0.015 mol/kg. The argon partial pressure is 0.7 atmosphere and the blank is kept at 590°C for 60 minutes at 400°C with a hydrogen addition of 0.05 mol/kg. sintering Vacuum sintering 1040℃*5 hours aging treatment Vacuum aging: 900℃*2 hours, cool to room temperature +490℃*3 hours, cool to room temperature

Referring to Table 3, Table 3 shows the magnetic properties of Comparative Example 1, Comparative Example 2, Example 1 and Example 2. [table 3] Comparative example 1 Comparative example 2 Example 1 Example 2 Waste magnet prior art Regeneration method using the present invention 1 Regeneration method 2 using the present invention C/O/N content C ppm 820 1240 910 880 ppm 1250 2240 1940 1970 ppm 130 70 50 40 Magnetic properties Magnet position number Magnet 102 Magnet 103 Magnet 102 Magnet 103 Magnet 102 Magnet 103 Residual magnetism Br kG 13.16 13.09 13.07 13.14 13.14 13.16 13.14 Maximum magnetic energy product BHmax (MGOe) 41.90 41.33 41.21 41.66 41.68 41.79 41.66 Intrinsic coercivity iHc (kOe) 18.83 18.52 17.40 18.65 18.18 18.72 18.35 △iHc 6.0% 2.5% 1.9% Demagnetization curve rectangularity Hk/Hcj 0.95 0.94 0.94 0.95 0.95 0.96 0.95 BHmax+iHc 60.73 59.85 58.61 60.31 59.86 60.51 60.01 Density(g/cm3) 7.54 7.53 7.53 7.54 7.54 7.55 7.54

Comparative example 1

According to the analysis results, the carbon content in the original waste magnet is 820ppm, the oxygen content is 1250ppm, and the nitrogen content is 130ppm. The maximum magnetic energy product (BHmax) in the magnetic properties is 41.90 MGOe, and the intrinsic coercive force (iHc) is 18.83 kOe, which belongs to N42H The BHH (maximum magnetic energy product (BHmax) + intrinsic coercivity (iHc)) of grade magnets is 60.73.

Comparative example 2

For the regenerated magnet produced in Comparative Example 2, after the blank was put into the sintering furnace, it was heated from room temperature to 590°C for 60 minutes and treated in an atmosphere with an argon partial pressure of 0.9 atmospheres, and then vacuum sintering was started. According to the analysis results, the carbon content of the regenerated magnet made with the previous technology (excluding the normal temperature hydrogen absorption crushing step, normal temperature vacuum dehydrogenation step, high temperature vacuum dehydrogenation step and argon partial pressure hydrogenation step) is 1240ppm, The oxygen content is 2240ppm and the nitrogen content is 70ppm. Except for the decrease in nitrogen content, the other carbon and oxygen contents are significantly higher than that of the original waste magnet. The maximum magnetic energy product (BHmax) in the magnetic properties of the recycled magnet located at the magnet 102 position in the rough embryo ) is 41.33 MGOe, and the intrinsic coercive force (iHc) is 18.52 kOe, but the maximum magnetic energy product (BHmax) in the magnetic properties of the recycled magnet located at position 103 of the magnet in the blank is 41.21 MGOe, and the intrinsic coercive force (iHc) is 41.21 MGOe. iHc) is 17.40 kOe. The maximum magnetic energy product (BHmax) value is quite close, but there is a 6.0% difference in the intrinsic coercive force (iHc) value. The magnetic uniformity of each point in the entire blank is insufficient.

Example 1

According to the scrap magnet recovery and regeneration method 1 with improved magnetic properties of the present invention, the normal temperature hydrogen absorption crushing step and the normal temperature vacuum dehydrogenation step are to absorb hydrogen at room temperature for 2 hours, and dehydrogenate at room temperature to a vacuum degree of 60 Pascal; high temperature vacuum dehydrogenation The hydrogen step and the argon partial pressure hydrogenation step are to heat room temperature to 300°C in a vacuum environment. After holding the temperature at 300°C for 40 minutes, the sintering furnace stops vacuuming and injects argon gas to a partial pressure of 0.8 atmospheres, and continues to raise the temperature to 400°C. ℃, hydrogen is injected into the sintering furnace, and the amount of hydrogen injected is controlled to 0.015 mol/kg of blank weight. The temperature is continuously raised to 590°C and maintained for 60 minutes, and then vacuum sintering is started. In Example 1, the carbon content in the regenerated magnet is 910 ppm, the oxygen content is 1940 ppm, and the nitrogen content is 50 ppm. Compared with the previous technology, the carbon, oxygen, and nitrogen contents are significantly reduced. The magnetism of the regenerated magnet located at the position of magnet 102 in the blank is The maximum magnetic energy product (BHmax) in the characteristics is 41.66 MGOe, and the intrinsic coercive force (iHc) is 18.65 kOe. The maximum magnetic energy product (BHmax) in the magnetic characteristics of the recycled magnet located at the magnet 103 position in the blank is 41.68 MGOe. The intrinsic coercive force (iHc) is 18.18 kOe. The maximum magnetic energy product (BHmax) value of the two is quite close. The difference in the intrinsic coercive force (iHc) has been reduced to 2.5%. The magnetism at each point in the entire blank is uniform. Sex is significantly improved.

Example 2

According to the scrap magnet recovery and regeneration method 2 with improved magnetic properties of the present invention, the normal temperature hydrogen absorption crushing step and the normal temperature vacuum dehydrogenation step are to absorb hydrogen at room temperature for 2 hours, and dehydrogenate at room temperature to a vacuum degree of 60 Pascal; high temperature vacuum dehydrogenation The hydrogen step and the argon partial pressure hydrogenation step are: after the blank enters the sintering furnace, the room temperature is heated to 270°C in a vacuum environment, and the temperature is maintained at 270°C for 60 minutes. The sintering furnace stops vacuuming and injects argon partial pressure After reaching 0.7 atmospheric pressure, the temperature continues to rise. When the temperature rises to 400°C, hydrogen is injected into the sintering furnace. The hydrogen injection amount is controlled to 0.05 mol/kg of blank weight. The temperature continues to rise to 590°C and is maintained for 60 minutes. Vacuum sintering then begins. In Example 2, the carbon content in the regenerated magnet is 880 ppm, the oxygen content is 1970 ppm, and the nitrogen content is 40 ppm. Compared with the previous technology, the carbon, oxygen, and nitrogen contents are significantly reduced. The magnet content of the regenerated magnet located at the position of magnet 102 in the blank is The maximum magnetic energy product (BHmax) in the characteristics is 41.79 MGOe, and the intrinsic coercive force (iHc) is 18.72 kOe. The maximum magnetic energy product (BHmax) in the magnetic characteristics of the recycled magnet located at the magnet 103 position in the blank is 41.66 MGOe, and the internal coercive force (iHc) is 18.72 kOe. The intrinsic coercive force (iHc) is 18.35 kOe. The maximum magnetic energy product (BHmax) value of the two is quite close. The difference in the intrinsic coercive force (iHc) has been reduced to 1.9%. The magnetism at each point in the entire blank is uniform. Sex is significantly improved.

According to the examples of the above embodiments, the present invention uses a normal temperature hydrogen crushing step to absorb hydrogen into the waste magnet at room temperature for more than 2 hours, and dehydrogenate at room temperature to a vacuum degree of less than 1000 Pascals (preferably, to less than 100 Pascals). , the embodiment takes 60 Pascal as an example); after the green embryo is put into the sintering furnace, a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step are performed. When the previous technical method is heated from room temperature to 550°C to 600°C, it is in argon. The step of processing in a gas partial pressure atmosphere and then starting vacuum sintering is changed to two stages. In the first stage, the green embryo enters the sintering furnace and is vacuumed and dehydrogenated when the room temperature rises to the range of 200°C to 350°C. In the second stage, the vacuum is stopped and the partial pressure of argon is injected to bring the partial pressure to 0.1 to 0.98 atmospheres. When the temperature continues to rise to 400°C, hydrogen is injected. The amount of hydrogen injected is 0.001 to 0.3 mol/kg of the weight of the blank. Then the temperature continues to rise to 560 to 600°C. The regeneration method of the present invention can further reduce the carbon, oxygen, and nitrogen content in the regenerated magnet blank, and improve the uniformity of the magnetic properties everywhere inside the blank.

According to the above embodiment, the present invention also provides a regenerated magnet manufactured by the waste magnet recycling and regeneration method for improving magnetic properties as described above, wherein the maximum magnetic energy product (BHmax) among several regenerated magnets made from the same blank is: 41.66 MGOe or above, the intrinsic coercive force value between the recycled magnets is above 18.18 kOe, and the intrinsic coercive force value difference (△iHc) between the recycled magnets is below 2.5%.

S100～S500: steps 10: Magnet blank 101～104: Magnet

[Fig. 1]: Schematic flow chart of a waste magnet recycling and regeneration method for improving magnetic properties according to an embodiment of the present invention. [Fig. 2A]: A schematic diagram of magnet distribution after recycling waste magnets according to the embodiments and comparative examples of the present invention and using the method of the present invention and known techniques to make new magnet blanks and then sintering them. [Figure 2B]: A schematic exploded view of the distribution of magnets that are sintered after waste magnets are recycled into new magnet blanks using the method of the invention and known techniques according to the embodiments and comparative examples of the present invention.

S100~S500: steps

Claims (10)

A waste magnet recycling and regeneration method that improves magnetic properties includes the following steps: (a) providing a waste magnet; (b) performing a pre-treatment step on the waste magnet; (c) treating the waste magnet after the pre-treatment step Carry out a normal temperature hydrogen absorption crushing step and a normal temperature vacuum dehydrogenation step, so that the waste magnet forms a waste magnet coarse powder; (d) perform an air flow crushing step on the waste magnet coarse powder and then mix it with an auxiliary alloy powder, or The waste magnet coarse powder and an auxiliary alloy powder are mixed and then subjected to an airflow crushing step to form a regenerated magnet mixture, wherein the weight ratio of the regenerated magnet main alloy powder and the auxiliary alloy powder is 90:10 to 99.5:0.5 (e) After performing an alignment forming step on the regenerated magnet mixture, a high-temperature vacuum dehydrogenation step and an argon partial pressure hydrogenation step are performed, and in the high-temperature vacuum dehydrogenation step and the argon gas After the partial pressure hydrogenation step, a vacuum sintering step and an aging treatment step are performed to obtain a regenerated magnet. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the high-temperature vacuum dehydrogenation step includes the following steps: a rough embryo made from the regenerated magnet mixture is raised to a temperature of room temperature. After the first predetermined temperature, a vacuum dehydrogenation step is performed, and the temperature is maintained at the first predetermined temperature for a first temperature holding time, wherein the first predetermined temperature is 200°C to 350°C and the temperature holding time is 10 minutes. above. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 2, wherein the predetermined temperature is 250°C to 300°C and the temperature holding time is more than 30 minutes. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the argon partial pressure hydrogenation step includes the following steps: after the high-temperature vacuum dehydrogenation step, stop vacuuming and inject argon gas to reach an argon gas partial pressure, wherein the argon partial pressure is 0.1 to 0.98 atmospheric pressure; continue to inject hydrogen when the temperature is raised to 360 to 440°C, in which the hydrogen injection amount is 0.001 to 0.3 mol/kg of blank weight; and the temperature is raised to the last second predetermined The temperature is maintained for a second temperature holding time, wherein the second predetermined temperature is 560 to 600°C and the second temperature holding time is more than 10 minutes. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 4, wherein the argon partial pressure is 0.7 to 0.9 atmospheres, the hydrogen injection amount is 0.01 to 0.1 mol/kg blank weight, and the second predetermined temperature The temperature is 580 to 590°C and the second temperature holding time is more than 30 minutes. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the waste magnet coarse powder is mixed with an auxiliary alloy powder and then the airflow crushing step further includes: taking the weight percentage of the total powder amount as 100wt% According to the calculation, add 0.02 to 0.3wt% of an organic additive. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the vacuum degree of the normal temperature vacuum dehydrogenation step is less than 1000 Pascals. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the vacuum degree of the normal temperature vacuum dehydrogenation step is less than 100 Pascals. The waste magnet recycling and regeneration method for improving magnetic properties as described in claim 1, wherein the composition of the auxiliary alloy powder is R _a (Co, Fe) _b (Cu, Al, Ga) _c , where R includes lanthanum, cerium, and chromium , neodymium, gallium, dynamium, dysprosium, and mixtures thereof, wherein based on the weight percentage wt% of the auxiliary alloy powder being 100, a is between 70wt% and 99.8wt, b is between 0.1wt% and 30wt%, c It is between 0.1wt% and 30wt%. A regenerated magnet manufactured by the waste magnet recycling and regeneration method for improving magnetic properties as described in any one of claims 1 to 9, wherein the largest magnet among several regenerated magnets made from the same blank The energy product (BHmax) is above 41.66 MGOe, the intrinsic coercive force value between the recycled magnets is above 18.18 kOe, and the intrinsic coercive force value difference (△iHc) between the recycled magnets is below 2.5%.