TWI835100B - Magnet and method of fabricating the same - Google Patents

Abstract

A magnet and a method of fabricating the same are provided, including a first fine milling step and a second fine milling step, in which a rotational speed of a classifying wheel in the second fine milling step is higher than a rotational speed of a classifying wheel in the first fine milling step, and a milling pressure in the second fine milling step is lower than a milling pressure in the first fine milling step. The powder distribution and the powder morphology of the magnet are improved by adding the second fine milling step after the first fine milling step, thereby improving the magnetic properties of the magnet. Moreover, a required density of green compact which is pressed and formed is further limited, so the magnet is not broken during the production process and can be easily formed.

Description

Magnet and its manufacturing method

The present disclosure relates to magnetic materials and manufacturing methods thereof, and in particular to a magnet and manufacturing methods thereof.

In recent years, as electronic components have become smaller, lighter, and higher in performance, magnets are increasingly required to have higher magnetic properties. As indicators of the magnetic properties of magnets, the maximum magnetic energy product (BH _max ) and intrinsic coercive force ( _i H _c ) are generally used as indicators. For a long time, in order to achieve high maximum magnetic energy product and high intrinsic coercive force characteristics, the elemental composition and manufacturing process of magnets have been continuously discussed and studied.

Generally, in the manufacturing process of NdFeB magnets, a NdFeB alloy material is first subjected to hydrogen crushing and fine grinding (such as jet mill), and then magnetic field alignment, sintering and heat treatment are performed to form the magnet. The product, wherein the hydrogen fragmentation includes a hydrogen absorption step and a dehydrogenation step. However, the magnetic properties of the magnets produced by the aforementioned manufacturing process are still insufficient and therefore still need to be improved. Therefore, it is necessary to provide a magnet and a manufacturing method thereof to solve the problems existing in the conventional technology.

An object of the present disclosure is to provide a magnet and a manufacturing method thereof. The main feature is to add a secondary fine grinding step to improve the powder distribution and powder morphology of the magnet, thereby improving the magnetic properties of the magnet; in addition, it is further limited In order to press the required density of the green embryo, the magnet will not crack during the production process.

To achieve the above purpose, the present disclosure provides a method for manufacturing magnets, which includes the following steps: S101: Provide a NdFeB alloy material; S102: Perform a hydrogen crushing step on the NdFeB alloy material to obtain a hydrogen crushing step Powder, wherein the hydrogen crushing step includes a hydrogen absorption step and does not implement any dehydrogenation step; S103: Perform a first fine crushing step on the hydrogen crushed powder to form a first alloy powder, wherein the first fine crushing The step is to pulverize the hydrogen crushed powder under a first classifying wheel speed and a first pulverizing pressure; S104: Perform a second fine pulverizing step on the first alloy powder to form a second alloy powder, wherein the The second fine crushing step is to crush the first alloy powder under a second classifying wheel speed and a second crushing pressure. The second classifying wheel speed is higher than the first classifying wheel speed, and the second crushing pressure is low. At the first crushing pressure, and the D90/D10 ratio of the particle size distribution of the second alloy powder is smaller than the D90/D10 ratio of the particle size distribution of the first alloy powder; S105: Apply a magnetic field to the second alloy powder Alignment forming step, the magnetic field alignment forming step includes pressing the second alloy powder into a green embryo, wherein the density of the green embryo is greater than 3.8 g/cm ³ and less than or equal to 4.4 g/cm ³ ; and S106: The green embryo according to A dehydrogenation step, a sintering step and a heat treatment step are performed in sequence.

In an embodiment of the present disclosure, the D50 of the particle size distribution of the first alloy powder or the second alloy powder may be between 2 microns and 6 microns.

In an embodiment of the present disclosure, the grinding time of the second fine grinding step may be between 1 minute and 30 minutes.

In an embodiment of the present disclosure, the first fine grinding step and the second fine grinding step may be carried out by using an airflow grinder.

In an embodiment of the present disclosure, the first classifying wheel rotation speed may be between 9000 rpm and 10000 rpm, and the first crushing pressure may be between 0.5 MPa and 0.7 MPa.

In an embodiment of the present disclosure, the second classifying wheel rotation speed may be between 20,000 rpm and 24,000 rpm, and the second crushing pressure may be between 0.4 MPa and 0.5 MPa.

In an embodiment of the present disclosure, the D90/D10 ratio of the particle size distribution of the first alloy powder may be between 4.9 and 5.1, and the D90/D10 ratio of the particle size distribution of the second alloy powder may be between Between 4.5 and 4.7.

In an embodiment of the present disclosure, based on the total weight of the NdFeB alloy material being 100 wt%, the composition of the NdFeB alloy material is (Nd,Pr) _a Co _b Cu _c Al _d Ga _e B _f Fe _bal , where 28.0 wt%≤a≤33.0 wt%, 0.5 wt%＜b≤ 1.5 wt%, 0 wt%≤c≤0.2 wt%, 0 wt%≤d≤0.2 wt%, 0.2 wt%＜e≤ 0.5 wt% and 0.9 wt%≤f≤1.1 wt%.

In an embodiment of the present disclosure, the composition of the NdFeB alloy material is (Nd,Pr) _29.9 Co _0.9 Cu _0.09 Al _0.07 Ga _0.32 B _0.92 Fe _bal .

In one embodiment of the present disclosure, the hydrogen absorption step in the hydrogen crushing step is to place the NdFeB alloy material in a hydrogen environment for 1 to 7 hours, and the hydrogen absorption pressure is between 1.5 kgf/cm ² and 2.5 kgf/cm ² .

In an embodiment of the present disclosure, step S103 further includes adding a lubricant to the hydrogen crushed powder to form a mixture before the first fine grinding step, wherein the total weight of the neodymium iron boron alloy material is 100 wt. In terms of %, the content of the lubricant may be between 0.01 wt% and 0.1 wt%.

In an embodiment of the present disclosure, step S104 further includes reducing the speed of the classifying wheel to between 2500 rpm and 3500 rpm to collect the second alloy powder.

In one embodiment of the present disclosure, the dehydrogenation step in step S106 is to place the green embryo in an argon environment and heat it from room temperature to between 550°C and 600°C for dehydrogenation, where the heating rate is less than minute 2°C, and the argon partial pressure of the argon environment is between 0.8 atm and 1.0 atm.

In an embodiment of the present disclosure, after the dehydrogenation step, the sintering step is to continue heating to between 950°C and 1050°C with a vacuum degree between 10 ^-5 torr and 10 ^-4 torr. The dehydrogenated green embryo is vacuum sintered at a temperature of 2 to 7 hours to form a rough embryo.

In an embodiment of the present disclosure, after performing the sintering step, the heat treatment step is to heat-treat the rough embryo at a vacuum degree between 10 ^-5 torr to 10 ^-4 torr for 1 hour to 5 hours, and Heat treatment is performed between 450°C and 550°C to produce the magnet as described in the present disclosure.

In order to achieve the above object, the present disclosure provides a magnet, which is made by the magnet manufacturing method as described in any of the above embodiments, and the BH _max of the magnet is greater than 52 MGOe, and the iHc is greater than 15.4 kOe.

In one embodiment of the present disclosure, the carbon content of the magnet is between 500 ppm and 600 ppm.

In an embodiment of the present disclosure, the oxygen content of the magnet is between 1200 ppm and 1400 ppm.

In an embodiment of the present disclosure, the nitrogen content of the magnet is between 40 ppm and 60 ppm.

Continuing, the magnet manufacturing method provided by the present disclosure mainly improves the powder of the magnet by adding a second fine grinding step after the first fine grinding step (i.e., the above-mentioned second fine grinding step). distribution and powder morphology, thereby improving the magnetic properties of the magnet, wherein the speed of the classifying wheel in the second fine grinding step (i.e., the second classifying wheel speed) needs to be higher than the speed of the classifying wheel in the first fine grinding step (i.e., the rotation speed of the first classifying wheel), and the crushing pressure in the second fine crushing step (ie, the second crushing pressure) needs to be lower than the crushing pressure in the first fine crushing step (ie, the first crushing pressure) ; In addition, the required density of the pressed green embryo is further limited, so the magnet will not crack during the production process and is easy to form.

In order to make the above and other objects, features, and advantages of the present disclosure more obvious and understandable, preferred embodiments of the present disclosure will be described in detail below along with the accompanying drawings. Furthermore, the directional terms mentioned in this disclosure include up, down, top, bottom, front, back, left, right, inside, outside, side, around, center, 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 explain and understand the present disclosure, but not to limit the present disclosure.

The manufacturing method of the magnet disclosed in the present disclosure improves the powder distribution and powder morphology of the magnet by adding a second fine grinding step after the first fine grinding step, thereby improving the magnetic properties of the magnet. The second fine grinding step The rotating speed of the classifying wheel in the step needs to be higher than the rotating speed of the classifying wheel in the first fine crushing step, and the crushing pressure in the second fine crushing step needs to be lower than the crushing pressure in the first fine crushing step; in addition, the compression is further limited to The required density of the green embryo, so the magnet will not crack during the production process and is easy to shape.

Please refer to Figure 1. Figure 1 is a step flow chart of a magnet manufacturing method according to an embodiment of the present disclosure. In some embodiments, as shown in step S101, a NdFeB alloy material (for example, a NdFeB alloy scraper) is provided. Specifically, based on the total weight of the NdFeB alloy material being 100 wt%, the NdFeB alloy material is The composition of boron alloy material is (Nd,Pr) _a Co _b Cu _c Al _d Ga _e B _f Fe _bal , where 28.0 wt%≤a≤33.0 wt%, 0.5 wt%＜b≤ 1.5 wt%, 0 wt %≤ c≤0.2 wt%, 0 wt%≤d≤0.2 wt%, 0.2 wt%<e≤0.5 wt%, and 0.9 wt%≤f≤1.1 wt%. In some embodiments, a includes, but is not limited to, 28.0 wt%, 29.0 wt%, 30.0 wt%, 31.0 wt%, 32.0 wt%, 33.0 wt%, or any value therebetween. In some embodiments, b includes, but is not limited to, 0.5 wt%, 0.7 wt%, 0.9 wt%, 1.1 wt%, 1.3 wt%, 1.5 wt%, or any value therebetween. In some embodiments, c includes, but is not limited to, 0 wt%, 0.04 wt%, 0.08 wt%, 0.12 wt%, 0.16 wt%, 0.2 wt%, or any value in between. In some embodiments, d includes, but is not limited to, 0 wt%, 0.04 wt%, 0.08 wt%, 0.12 wt%, 0.16 wt%, 0.2 wt%, or any value in between. In some embodiments, e includes, but is not limited to, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or any value in between. In some embodiments, f includes, but is not limited to, 0.9 wt%, 0.94 wt%, 0.98 wt%, 1.02 wt%, 1.06 wt%, 1.1 wt%, or any value in between. In some embodiments, the composition of the NdFeB alloy material is preferably (Nd,Pr) _29.9 Co _0.9 Cu _0.09 Al _0.07 Ga _0.32 B _0.92 Fe _bal .

In addition, it should be noted that the bal referred to here is a commonly used term in general alloy composition, and is mainly used to balance the alloy composition to 100%. Taking the NdFeB alloy material of the present disclosure as an example, in the composition of the NdFeB alloy material, the weight of all elements except Fe is 32.2 wt%, so the bal of Fe here refers to 67.8 wt%. Similarly, if the weight of all elements except Fe is 30 wt%, then the bal of Fe here refers to 70 wt%.

Please continue to refer to Figure 1. As shown in step S102, the NdFeB alloy material is subjected to a hydrogen crushing step to obtain hydrogen crushed powder. The hydrogen crushing step includes a hydrogen absorption step, and no dehydrogenation step is performed in this step. In some embodiments, the hydrogen crushing step is performed in a hydrogen environment for 1 hour to 7 hours, and the hydrogen absorption pressure is between 1.5 kgf/cm ² and 2.5 kgf/cm ² . Specifically, the present disclosure uses a pressure of 1.5 kgf/cm ² to 2.5 kgf/cm ² to absorb hydrogen and crush it, without performing an additional dehydrogenation step. In the conventional technology, additional vacuuming and heating to 500°C are performed. Dehydrogenation is carried out between 600 ℃ and 600 ℃.

In some embodiments, the hydrogen absorption pressure of the hydrogen crushing step includes, but is not limited to, 1.5 kgf/cm ² , 2.0 kgf/cm ² , 2.5 kgf/cm ² or any value between these values. In some embodiments, the implementation time of the hydrogen crushing step includes, but is not limited to, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or any value between these values. As mentioned above, because the hydrogen crushed powder carries hydrogen, the hydrogen it carries is beneficial to reducing the carbon and nitrogen combined with the rare earth elements in the subsequent sintering step, so that the rare earth elements can be easily sintered.

Next, please refer to step S103, the hydrogen crushed powder is subjected to a first fine grinding step to form a first alloy powder, wherein the first fine grinding step is to use airflow grinding under a first classifying wheel speed and a first grinding pressure. The hydrogen crushing powder is pulverized by a machine. In some embodiments, the D50 of the particle size distribution of the first alloy powder is between 2 microns and 6 microns. In some embodiments, the D90/D10 ratio of the particle size distribution of the first alloy powder is between 4.9 and 5.1. It should be noted that the first alloy powder has a particle size distribution with D10, D50, and D90 values, where D10, D50, and D90 refer to the cumulative particle size distribution number of the first alloy powder, and D10 indicates that the particle size distribution number reaches The particle size corresponding to 10%, its physical meaning is that particles smaller than it account for 10%; D50 represents the particle size corresponding to when the particle size distribution number reaches 50%, its physical meaning is that particles smaller than it account for 50% %; and D90 represents the particle size corresponding to when the cumulative particle size distribution number reaches 90%. Its physical meaning is that 90% of the particles have a particle size smaller than it. In some embodiments, the D50 of the particle size distribution of the first alloy powder includes, but is not limited to, 2 microns, 2.5 microns, 3 microns, 3.5 microns, 4 microns, 4.5 microns, 5 microns, 5.5 microns, 6 microns, or the like. Any value in between. Continuing from the above, D90/D10 can be expressed as the concentration of particle size distribution. When D90/D10 is smaller, the particle size distribution is more uniform, and vice versa. In some embodiments, the D90/D10 ratio of the particle size distribution of the first alloy powder includes, but is not limited to, 4.9, 4.95, 5.0, 5.05, 5.1, or any value between these values. In some embodiments, the D90/D10 ratio of the particle size distribution of the first alloy powder is preferably between 4.9 and 5.0, and is optimally 4.94.

In some embodiments, the first fine grinding step is performed in a nitrogen environment at a classifying wheel speed of between 9000 rpm and 10000 rpm (i.e., the first classifying wheel speed) and between 0.5 MPa and 0.7 MPa. The pressure (ie, the first crushing pressure) crushes the hydrogen crushing powder. In some embodiments, the classification wheel speed in the first fine grinding step includes, but is not limited to, 9000 rpm, 9100 rpm, 9200 rpm, 9300 rpm, 9400 rpm, 9500 rpm, 9600 rpm, 9700 rpm, 9800 rpm, 9900 rpm rpm, 10000 rpm, or anything in between. In some embodiments, the rotation speed of the classifying wheel in the first fine grinding step is preferably 9500 rpm. In some embodiments, the nitrogen pressure of the first fine grinding step (ie, the first grinding pressure) includes, but is not limited to, 0.5 MPa, 0.6 MPa, 0.7 MPa, or any value between these values. In some embodiments, the nitrogen pressure in the first fine grinding step is preferably 0.6 MPa.

In some embodiments, step S103 further includes adding lubricant to the hydrogen crushing powder to form a mixture before the first fine crushing step. In some embodiments, the total weight of the NdFeB alloy material is based on 100 wt%, and the content of the lubricant is between 0.01 wt% and 0.1 wt%. In some embodiments, the lubricant content includes, but is not limited to, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt %, 0.1 wt%, or anything in between. In some embodiments, the lubricant content is preferably 0.1 wt%. In some embodiments, the lubricant may include stearates, or common powder metallurgy lubricants may be used.

It should be noted that the first fine grinding step uses a lower classification wheel speed and a higher grinding pressure (compared to the second fine grinding step) to cause the hydrogen-crushed powders to collide with each other, thus refining the hydrogen-crushed powders. Moreover, when obtaining the first alloy powder, the first alloy powder is obtained in a continuous discharging manner.

Still referring to Figure 1, as shown in step S104, a second fine pulverizing step is performed on the first alloy powder to form a second alloy powder, wherein the second fine pulverizing step is a combination of a second classifying wheel speed and a first The first alloy powder is pulverized using a jet pulverizer under two pulverizing pressures. The rotational speed of the second grading wheel needs to be higher than the rotational speed of the first grading wheel. The second pulverizing pressure needs to be lower than the first pulverizing pressure, and the second pulverizing pressure needs to be lower than the first pulverizing pressure. The D90/D10 ratio of the particle size distribution of the second alloy powder is smaller than the D90/D10 ratio of the particle size distribution of the first alloy powder. In some embodiments, the D50 of the particle size distribution of the second alloy powder is between 2 microns and 6 microns. In some embodiments, the D90/D10 ratio of the particle size distribution of the second alloy powder is between 4.5 and 4.7. It should be noted that the second alloy powder has a particle size distribution with D10, D50, and D90 values. The meanings of D10, D50, D90, and D90/D10 have been described in the previous paragraphs, so they are not discussed here. Again. In some embodiments, the D50 of the particle size distribution of the second alloy powder includes, but is not limited to, 2 microns, 2.1 microns, 2.3 microns, 2.5 microns, 2.7 microns, 2.9 microns, 3.1 microns, 3.3 microns, 3.5 microns, 3.7 Micron, 3.9 micron, 4.1 micron, 4.3 micron, 4.5 micron, 4.7 micron, 4.9 micron, 5.1 micron, 5.3 micron, 5.7 micron, 5.9 micron, 6 micron or any value in between. In some embodiments, the D50 of the particle size distribution of the second alloy powder is preferably between about 3.7 microns and about 5.9 microns. In some embodiments, the D90/D10 ratio of the particle size distribution of the second alloy powder includes, but is not limited to, 4.5, 4.55, 4.6, 4.65, 4.7, or any value between these values. In some embodiments, the D90/D10 ratio of the particle size distribution of the second alloy powder is preferably between 4.6 and 4.7, and is optimally 4.66. It can be seen from this that after the first alloy powder is subjected to the second fine grinding step, the particle size distribution of the second alloy powder obtained is more concentrated than that of the first alloy powder.

In some embodiments, the second fine grinding step is performed in a nitrogen atmosphere at a classifying wheel speed between 20,000 rpm and 24,000 rpm (ie, a second classifying wheel speed) and between 0.4 MPa and 0.5 MPa. The crushing pressure (i.e., the second crushing pressure) crushes the first alloy powder for 1 to 30 minutes, and reduces the classification wheel speed to between 2500 rpm and 3500 rpm to collect the second alloy powder. In some embodiments, the rotation speed of the classifying wheel in the second fine grinding step includes, but is not limited to, 20,000 rpm, 21,000 rpm, 22,000 rpm, 23,000 rpm, 24,000 rpm, or any value between these values. In some embodiments, the rotation speed of the classifying wheel in the second fine grinding step is preferably 22,000 rpm. In some embodiments, the nitrogen pressure of the second fine grinding step (ie, the second grinding pressure) includes, but is not limited to, 0.4 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, 0.44 MPa, 0.45 MPa, 0.46 MPa, 0.47 MPa, 0.48 MPa, 0.49 MPa, 0.5 MPa, or any value in between. In some embodiments, the nitrogen pressure in the second fine grinding step is preferably 0.45 MPa. In some embodiments, the implementation time in the second fine grinding step includes, but is not limited to, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes or any value between these values. . In some embodiments, the implementation time in the second fine grinding step is preferably 10 minutes. In some embodiments, the speed of the classification wheel after the second fine grinding step is reduced includes, but is not limited to, 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2900 rpm, 3000 rpm, 3100 rpm, 3200 rpm, 3300 rpm, 3400 rpm, 3500 rpm, or anything in between. In some embodiments, the reduced rotation speed of the second fine grinding step is preferably 3000 rpm. Specifically, the second fine grinding step of step S104 is performed in the classification wheel. After the rotation speed is reduced, the second alloy powder that meets the particle size will be discharged from the classification wheel and collected. Specifically, step S104 controls the nitrogen pressure and implementation time, so as to avoid over-refining the second alloy powder, which would make subsequent magnetic field alignment difficult to form.

In addition, it should be noted that the difference between the second fine grinding step and the first fine grinding step is that the second fine grinding step uses a higher classification wheel speed than the first fine grinding step and a lower speed than the first fine grinding step. The crushing pressure causes the first alloy powders to grind each other, which can reduce the edges and corners of the first alloy powder, thus obtaining a smoother second alloy powder. Moreover, when obtaining the second alloy powder, the second alloy powder is obtained in a batch discharging manner, that is, the rotation speed of the classifying wheel is reduced as described above to obtain the second alloy powder that meets the particle size. Accordingly, after grinding the second alloy powder, reducing its edges and corners can make the subsequent magnetic field alignment step easier.

Please refer to step S105, a magnetic field alignment forming step is performed on the second alloy powder. The magnetic field alignment forming step includes pressing the second alloy powder into a green embryo. In some embodiments, the density of the green embryo is greater than 3.8 g/cm ³ and less than or equal to 4.4 g/cm ³ . In some embodiments, the density of the green embryo includes, but is not limited to, 3.9 g/cm ³ , 4.0 g/cm ³ , 4.1 g/cm ³ , 4.2 g/cm ³ , 4.3 g/cm ³ , 4.4 g/cm ³ , or any value in the range from above 3.8 g/ ^cm3 to below 4.4 g/ ^cm3 . In some embodiments, the density of the green embryo is preferably between 4.0 g/cm ³ and 4.2 g/cm ³ , and is optimally 4.1 g/cm ³ . It should be noted that because the second alloy powder has been ground through the second fine grinding step, a higher density must be used when pressing it into a green embryo. When the density of the green embryo is less than or equal to 3.8 g/ ^cm3 , the strength is low. It is easy to break and cannot be formed; however, when the density is greater than 4.4 g/cm ³ , it will be difficult to perform the subsequent magnetic field alignment forming step. It should be noted that the density referred to here refers to the density of the pressed green embryo, not the density of the subsequently formed magnet. In addition, the magnetic field alignment forming step can be performed with reference to the magnetic field alignment forming step in the general magnet processing step, and will not be described again here.

Please refer to step S106. The green embryo is subjected to a dehydrogenation step, a sintering step and a heat treatment step in sequence. After the magnetic field alignment forming step is completed, the green embryo will be subjected to a dehydrogenation step to dehydrogenate. The dehydrogenation described here refers to the removal of hydrogen absorbed in the hydrogen crushing step. In some embodiments, the dehydrogenation step is to place the green embryo in an argon atmosphere and heat it from room temperature to between 550°C and 600°C to dehydrogenate, where the heating rate is less than 2°C per minute, and the argon atmosphere is The partial pressure of gas is between 0.8 atm and 1.0 atm. Specifically, heating from room temperature to between 550°C and 600°C is the temperature range in which hydrogen autogenous embryos are detached, and heating is done at a slow rate to between 550°C and 600°C. In detail, the heating time between 550 ℃ and 600 ℃ needs to be more than 360 minutes. If the heating is too fast, the structure of the green embryo will be damaged and cracked. In some embodiments, the heating temperature for dehydrogenation includes, but is not limited to, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or any value between these values. In some embodiments, the heating temperature for dehydrogenation is preferably 580°C. In some embodiments, the argon atmosphere pressure includes, but is not limited to, 0.8 atm, 0.9 atm, 1.0 atm, or any value in between. In some embodiments, the partial pressure of argon in the dehydrogenation step is preferably 0.9 atm. In some embodiments, the heating rate for dehydrogenation is preferably 1.3°C per minute. In some embodiments, the heating time for dehydrogenation is preferably 450 minutes. It should be noted that the partial pressure of argon gas in the dehydrogenation step means that argon gas is introduced to maintain the pressure in a specific range, and then the gas supply is stopped and the pressure is maintained to perform the hydrogen removal step. Also, the dehydrogenation step has a lower heating rate, which reduces or avoids product breakage.

After the dehydrogenation step is completed, the sintering step is continued, which is performed by vacuum sintering, with a vacuum degree between 10 ^-5 torr and 10 ^-4 torr, and continuous heating to a temperature between 950 ℃ and 1050 ℃. After dehydrogenation, the green embryo is vacuum sintered for 2 to 7 hours to form a rough embryo. In some embodiments, the sintering step is performed at temperatures including, but not limited to, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, or Any value in between. In some embodiments, the sintering step is performed at a temperature preferably between 1000°C and 1030°C.

After the sintering step is completed, the heat treatment step continues. In some embodiments, the heat treatment step is to heat the rough embryo at a vacuum degree between 10 ^-5 torr and 10 ^-4 torr for 1 hour to 5 hours, and at a temperature between 450°C and 550°C to A magnet is made as described in the present disclosure. In some embodiments, the vacuum level of the heat treatment includes, but is not limited to, 1x10 ^-5 torr, 5x10 ^-5 torr, 1x10 ^-4 torr, or any value in between. In some embodiments, the heat treatment time includes, but is not limited to, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or any value in between. In some embodiments, the heat treatment temperature includes, but is not limited to, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or the like. any value in between. In some embodiments, the heat treatment temperature is preferably between 470°C and 500°C. Specifically, the heat treatment step continues the vacuum degree of the sintering step, lowering the ambient temperature to make sintering more complete, and the magnet structure to be stronger and more stable.

In summary, the manufacturing method of the magnet of the present disclosure has been described above. The magnets made by the manufacturing method of the magnet of the present disclosure and the magnets made by the conventional technology (ie, comparative examples) will be described below. It is proved that the magnet made by the magnet manufacturing method of the present disclosure does have its technical effect.

Please refer to Table 1 below, which shows a comparison table of manufacturing methods and magnet properties of the present disclosure and comparative examples. Table 1. Comparison of properties between the present disclosure and the comparative example Comparative ratio Disclosure NdFeB alloy material (Nd,Pr) _29.9 Co _0.9 Cu _0.09 Al _0.07 Ga _0.32 B _0.92 Fe _bal Hydrogen fragmentation step absorb hydrogen and dehydrogenate Absorb hydrogen without dehydrogenation The first fine crushing step have have The second fine crushing step without have sintering step Vacuum sintering Argon partial pressure sintering with hydrogen + vacuum sintering Sintering temperature rise rate quick slow First alloy powder particle size distribution First alloy powder particle size distribution D90/D10 4.94 4.94 Second alloy powder particle size distribution Second alloy powder particle size distribution D10 without 1.24 µm D50 without 3.51 µm D90 without 5.78 µm D90/D10 without 4.66 C, O, N component content C content 980 ppm 570 ppm O content 690ppm 1300 ppm N content 130 ppm 49 ppm Magnetic properties Br (remanence) 14.47kg 14.59kg BH _max (maximum magnetic energy product) 51.19 MGOe 52.46 MGOe iHc (intrinsic coercive force) 12.44kOe 16.04kOe H _k /H _cj (rectangularity of demagnetization curve) 0.982 0.980 BH _max +iHc 63.63 68.50

As can be seen from the above table, in terms of particle size distribution, the particle size distribution of the present disclosure is more concentrated than that of the comparative example. This shows that the second alloy powder of the present disclosure is more uniform and is therefore more conducive to magnetic field alignment and can also be used during pressing. Improve the strength of the green embryo. Next, in terms of carbon content, the present disclosure significantly reduces the carbon content of the magnet, thereby also giving the magnet stronger magnetic properties. From the comparison of the magnetic properties, it can be seen that the remanence, maximum magnetic energy product and intrinsic coercive force of the disclosed magnet are all higher than those of the comparative example. In particular, the maximum magnetic energy product and intrinsic coercive force are significantly improved. It can be seen that the present disclosure not only optimizes the magnet manufacturing process, but also produces magnets with better composition content and magnetic properties compared with the comparative example.

Next, please refer to Figures 2 and 3 at the same time. Figure 2 is a scanning electron microscope (SEM) image of the second alloy powder in an embodiment of the present disclosure (scale bar in the figure: 5 µm). Figure 3 is an SEM image of the first alloy powder in a pair of scales of this disclosure (scale bar: 5 µm). Comparing Figures 2 and 3, the second alloy powder in Figure 2 shows uniform particle size, a smoother appearance, and less ultra-fine powder. In contrast, Figure 3 shows the first alloy powder that has only the first fine grinding step. It shows that it has obvious edges and corners, a large difference in particle size, and a lot of ultra-fine powder. It should be noted that when the particle size is uniform and the appearance is smooth, the pressed green embryo has high strength and is not easily broken, and is easier to orient in the magnetic field, and the formed magnetism is stronger and longer-lasting. From this, it can be understood that through the optimization of the magnet manufacturing process, the present disclosure not only improves the physical properties of the magnet, but also greatly improves the magnetic properties, and further proves that the manufacturing method of the magnet and the magnet made by the present disclosure indeed have better performance than The technical efficacy of knowledge technology.

In summary, the manufacturing method of the magnet disclosed in the present disclosure improves the powder distribution and powder morphology of the magnet by adding a second fine grinding step after the first fine grinding step, thereby improving the magnetic properties of the magnet. , wherein the speed of the classifying wheel in the second fine grinding step needs to be higher than the speed of the classifying wheel in the first fine grinding step, and the grinding pressure in the second fine grinding step needs to be lower than the grinding pressure in the first fine grinding step; in addition , the present disclosure further limits the required density of the pressed green embryo, so the magnet will not crack during the manufacturing process and is easy to form.

In addition, it should be mentioned that the parameters, steps and other disclosures used in the comparative examples of this disclosure are not the prior art claimed by the inventor of this case, but are merely comparative examples used to highlight the characteristics of this case.

Although the present disclosure has been disclosed in terms of preferred embodiments, it is not intended to limit the disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure. Therefore, the disclosure The scope of protection shall be subject to the scope of the patent application attached.

S101-S106: Steps

Figure 1 is a step flow chart of a magnet manufacturing method according to an embodiment of the present disclosure. Figure 2 is a scanning electron microscope (SEM) image of the second alloy powder in an embodiment of the present disclosure (scale bar in the figure: 5 µm). Figure 3 is an SEM image of the first alloy powder in a pair of scales of this disclosure (scale bar: 5 µm).

S101-S106: Steps

Claims (14)

A method for manufacturing magnets, including the following steps: S101: Provide a NdFeB alloy material; S102: Perform a hydrogen crushing step on the NdFeB alloy material to obtain a hydrogen crushed powder, wherein the hydrogen crushing step includes a The hydrogen absorption step does not implement any dehydrogenation step; S103: Perform a first fine grinding step on the hydrogen crushed powder to form a first alloy powder, wherein the first fine grinding step is at a first classification wheel speed The hydrogen-crushed powder is pulverized under a first pulverizing pressure; S104: Perform a second fine pulverizing step on the first alloy powder to form a second alloy powder, wherein the second fine pulverizing step is a first The first alloy powder is pulverized under the rotation speed of the second classifying wheel and a second crushing pressure, the rotation speed of the second classifying wheel is higher than the rotation speed of the first classifying wheel, the second crushing pressure is lower than the first crushing pressure, and the The D90/D10 ratio of the particle size distribution of the second alloy powder is smaller than the D90/D10 ratio of the particle size distribution of the first alloy powder; S105: Perform a magnetic field alignment forming step on the second alloy powder, the magnetic field alignment forming step Including pressing the second alloy powder into a green embryo, wherein the density of the green embryo is greater than 3.8 g/cm ³ and less than or equal to 4.4 g/cm ³ ; and S106: sequentially performing a dehydrogenation step and a sintering step on the green embryo step and a heat treatment step. The method of claim 1, wherein the D50 of the particle size distribution of the first alloy powder or the second alloy powder is between 2 microns and 6 microns. The method of claim 1, wherein the crushing time of the second fine crushing step is between 1 minute and 30 minutes. The method according to claim 1, wherein the first fine grinding step and the second fine grinding step are carried out by using a jet pulverizer. The method of claim 1, wherein the first classifying wheel rotation speed is between 9000 rpm and 10000 rpm, and the first crushing pressure is between 0.5 MPa and 0.7 MPa. The method of claim 1, wherein the second classifying wheel rotation speed is between 20,000 rpm and 24,000 rpm, and the second crushing pressure is between 0.4 MPa and 0.5 MPa. The method of claim 1, wherein the D90/D10 ratio of the particle size distribution of the first alloy powder is between 4.9 and 5.1, and the D90/D10 ratio of the particle size distribution of the second alloy powder is between Between 4.5 and 4.7. The method as described in claim 1, wherein the dehydrogenation step in step S106 is to place the green embryo in an argon environment and heat it from room temperature to between 550°C and 600°C for dehydrogenation, wherein the heating rate is less than 2°C per minute, and the argon partial pressure of the argon environment is between 0.8 atm and 1.0 atm. The method of claim 8, wherein the sintering step is to continue heating to a temperature between 950°C and 1050°C with a vacuum degree between 10 ^-5 torr and 10 ^-4 torr after dehydrogenation. The green embryo is subjected to vacuum sintering for 2 to 7 hours to form a rough embryo. The method as described in claim 9, wherein the heat treatment step is to heat the rough embryo at a vacuum degree between 10 ^-5 torr to 10 ^-4 torr for 1 hour to 5 hours, and at 450 ℃ to 550 ℃ Heat treatment is carried out to make the magnet. A magnet, wherein the magnet is made by the method described in claim 1, and the BH _max of the magnet is greater than 52 MGOe, and the iHc is greater than 15.4 kOe. The magnet according to claim 11, wherein the carbon content of the magnet is between 500 ppm and 600 ppm. The magnet according to claim 11, wherein the oxygen content of the magnet is between 1200 ppm and 1400 ppm. The magnet according to claim 11, wherein the nitrogen content of the magnet is between 40 ppm and 60 ppm.