TW202041468A - Method of fabricating modified ferrite magnetic powder and ferrite magnet - Google Patents

Abstract

A method of fabricating a modified ferrite magnetic powder and a method of fabricating a ferrite magnet are provided. The method of fabricating the modified ferrite magnetic powder includes steps of: providing a mixture containing iron oxide powder and a telluride; performing a calcination step of heating the mixture at a temperature between 1260 and 1300°C for 50-70 minutes to form a pre-processed object; performing a coarse pulverization step to form a plurality of coarsely-pulverized particles having an average particle diameter between 1.5 and 2.0 micrometers; and performing a fine pulverization step to obtain the modified ferrite magnetic powder, the modified ferrite magnetic powder having an average particle diameter between 0.65 and 0.75 micrometers, wherein the fine pulverization step includes: performing a wet milling step for 17 to 20 hours by a plurality of grinding beads having a diameter of between 0.25 and 0.33 inches.

Description

Modified ferrite magnetic powder and manufacturing method of magnet

The present invention relates to a manufacturing method of magnetic powder and magnet, and more particularly to a manufacturing method of modified ferrite magnetic powder and a manufacturing method of modified ferrite magnet.

In recent years, with the reduction in size, weight, and performance of electronic components, permanent ferrite magnets made of oxides are also required to have high magnetic properties. As an indicator of the magnetic properties of permanent ferrite magnets, remanence (B _r ) and coercive force ( _i H _c ) are generally used as indicators. In order to achieve the characteristics of high remanence and high coercivity, the composition of elements in permanent ferrite magnets has been discussed.

In addition, in addition to high remanence and high coercivity, permanent magnet ferrite magnets must have a Sauareness ratio as high as possible (rectangularity is: at 90% of B _r , the magnetic field value ( The ratio of H _k ) to _i H _c . That is, if H _k / _i H _{c is} high, the demagnetization (Demagnetization) caused by the external magnetic field and temperature changes will be relatively small, which also represents the magnetic field orientation of the magnet itself It is higher, so more stable magnetic characteristics can be obtained. In addition, another indicator for the production of permanent ferrite magnets is to reduce the occurrence of cracks in the green embryo after the magnet is formed in the magnetic field or the magnet during the sintering process. The probability of occurrence of defects can further improve the yield rate of permanent ferrite magnets in mass production. However, the existing manufacturing methods of permanent ferrite magnets cannot simultaneously meet the above requirements for magnetic properties and mass production yield.

Therefore, it is necessary to provide a method for manufacturing modified ferrite magnetic powder and magnet to solve the problems existing in the conventional technology.

One object of the present invention is to provide a method for manufacturing ferrite magnetic powder and magnets, which utilizes a combination of a specific coarse crushing step and a fine crushing step to remove or reduce fine particles with a particle size greater than 0 and less than or equal to 0.05 microns. Particles to avoid or reduce the generation of non-magnetic phases that are not conducive to magnetic properties in the ferrite magnet, and can increase the yield of the ferrite magnet, thereby reducing production costs.

In order to achieve the above objective, the present invention provides a method for manufacturing modified ferrite magnetic powder, which includes the steps of: providing a mixture, wherein the mixture includes an iron oxide powder and a strontium compound; and performing a calcination step to use the mixture Hold the temperature between 1260 and 1300°C for between 50 and 70 minutes to form a pre-treatment object; perform a coarse crushing step on the pre-treatment object to form a plurality of coarsely crushed particles, wherein the coarse An average particle size of the pulverized particles is between 1.5 to 2.0 microns; and a fine pulverization step is performed on the coarsely pulverized particles to obtain the modified ferrite magnetic powder, and an average particle size of the modified ferrite magnetic powder The diameter is between 0.65 and 0.75 microns, and the fine pulverization step includes a wet grinding step for 17 to 20 hours with a plurality of grinding beads having a diameter between 0.25 and 0.33 inches.

In an embodiment of the present invention, a molecular formula of the pretreatment is SrO. nFe ₂ O ₃ , where n is between 5 and 6.

In an embodiment of the present invention, the mixture further includes at least one of a cobalt compound and a lanthanide compound.

In an embodiment of the present invention, a molecular formula of the pretreatment is (Sr ²⁺ _1-x La ³⁺ _x )O. n(Fe ³⁺ _12-y Co ²⁺ _y ) ₂ O ₃ , where n is between 7 and 9, and x=2ny.

In an embodiment of the present invention, the step of providing the mixture further includes: providing an additive, wherein the additive includes at least one of calcium carbonate, silicon oxide, phosphorus pentoxide, and boron oxide.

In an embodiment of the present invention, the additive includes calcium carbonate and silica, and based on a total weight of the mixture as 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight; and the silica-based medium Between 0.2 to 0.8 parts by weight.

In an embodiment of the present invention, the additive includes calcium carbonate, silicon oxide, phosphorus pentoxide, and boron oxide, and based on a total weight of the mixture as 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight. Between; silicon oxide is between 0.2 to 0.8 parts by weight; phosphorus pentoxide is greater than zero and less than or equal to 0.1 parts by weight; and boron oxide is greater than zero and less than or equal to 1 part by weight.

In an embodiment of the present invention, after the step of providing the mixture and before performing the calcination step, it further comprises a step of dehydrating the mixture, wherein the moisture content of the mixture after the dehydration step is 18 Between% and 24%.

In an embodiment of the present invention, an atmosphere of the calcination step contains 5% oxygen.

In order to achieve the above objective, the present invention provides a method for manufacturing a modified ferrite magnet, which includes the steps of: providing a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is obtained by the method described in any of the above embodiments The modified ferrite magnetic powder is manufactured by the manufacturing method; the ferrite magnetic powder is subjected to a magnetic field alignment forming step to form a green body, wherein an alignment magnetic field intensity of the magnetic field alignment forming step is between 1.3 to 1.7 Between Tesla, a molding pressure is between 3 to 4 tons/cm², and a molding time is between 90 and 110 seconds; and a sintering step is performed, and the green body is set to be between 1220 Continuous sintering at a temperature between 1240°C and 50 to 70 minutes to produce a ferrite magnet.

In order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following will specifically cite the preferred embodiments of the present invention, together with the accompanying drawings, and describe in detail as follows. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, surrounding, center, horizontal, horizontal, vertical, vertical, axial, The radial direction, the uppermost layer or the lowermost layer, etc., are only the direction of reference to the attached drawings. Therefore, the directional terms used are used to describe and understand the present invention, rather than to limit the present invention.

Referring to Figure 1, the manufacturing method 10 of modified ferrite magnetic powder according to an embodiment of the present invention mainly includes the following steps 11 to 14: providing a mixture, wherein the mixture includes iron oxide powder and a strontium compound (step 11); Carry out a calcination step, hold the mixture at a temperature of 1260 to 1300°C for 50 to 70 minutes to form a pre-treatment product (step 12); perform a coarse pulverization of the pre-treatment product Step to form a plurality of coarsely pulverized particles, wherein an average particle size of the coarsely pulverized particles is between 1.5 to 2.0 microns (step 13); and a fine pulverization step is performed on the coarsely pulverized particles to The modified ferrite magnetic powder is obtained, and the modified ferrite magnetic powder has an average particle size between 0.65 and 0.75 microns, wherein the finely pulverizing step includes having a diameter between 0.25 and 0.33 inches. Each grinding bead is subjected to a wet grinding step (step 14) for between 17 and 20 hours. In the present invention, the implementation details and principles of the above steps of the embodiments will be described in detail below one by one.

The manufacturing method 10 of modified ferrite magnetic powder according to an embodiment of the present invention first includes step 11: providing a mixture, wherein the mixture includes iron oxide powder and a strontium compound. In this step 11, the iron oxide powder can be, for example, a commercially available product, or a by-product produced in a steel manufacturing process. For example, the iron rust generated on the surface of the iron needs to be removed when the steel is hot processed. It can be used as the source of the iron oxide powder. In one embodiment, the strontium compound may include strontium carbonate, for example. It is worth mentioning that the provided mixture is mainly used to generate strontium ferrite magnetic powder.

In one embodiment, in step 11 of providing the mixture, an additive may be further provided, wherein the additive includes calcium carbonate (CaCO ₃ ), silicon oxide (SiO ₂ ), phosphorus pentoxide (P ₂ O ₅ ), and At least one of boron oxide (B ₂ O ₃ ). The effects of various additives are described below, and the weight percentages involved are based on the total weight of the mixture as 100 parts by weight. In one embodiment, the additive may be added to the ball mill in the pulverizing step.

Calcium carbonate is an element used to promote the growth of crystal grains. In the present invention, the amount of calcium carbonate added is, for example, between 0.5 to 1.5 parts by weight. When the amount of calcium carbonate added is too much (for example, greater than 1.5 parts by weight), subsequent In the sintering step for forming the ferrite magnet, excessive crystal grain growth occurs, resulting in a decrease in coercivity. On the other hand, when the added amount of calcium carbonate is too small (for example, less than 0.5 parts by weight), the phenomenon of crystal grain growth will be excessively suppressed, which in turn leads to insufficient increase in orientation that occurs at the same time as crystal grain growth, and ultimately leads to residual Magnetism (B _r ) is low.

The addition of silicon oxide is used to eliminate grain growth during sintering. The amount of silicon oxide added in the present invention is, for example, between 0.2 and 0.8 parts by weight. When the added silicon oxide is too small (for example, less than 0.2 parts by weight), excessive grain growth will occur during the sintering stage, resulting in a decrease in coercivity. When too much silicon oxide is added (for example, more than 0.8 parts by weight), the grain growth in the sintering stage will be excessively eliminated, resulting in insufficient orientation improvement that occurs at the same time as the grain growth, and ultimately resulting in remanence (B _r ) decline.

The addition of phosphorus pentoxide can increase squareness (H _k / _i H _c ), remanence (B _r ) and coercivity ( _i H _c ). The addition amount of phosphorus pentoxide in the present invention can be, for example, greater than zero and less than or equal to 0.1 parts by weight. If it is not within the aforementioned range, the aforementioned magnetic properties cannot be improved.

The addition of boron oxide is to reduce the sintering temperature when sintered magnets made of permanent ferrite magnets are made, and at the same time to increase the remanence (B _r ) and coercivity ( _i H _c ). The oxidation in the present invention The amount of boron added is, for example, greater than zero and less than or equal to 1 part by weight. If it is not within the aforementioned range, the aforementioned magnetic properties cannot be improved.

In one embodiment, the additive includes calcium carbonate and silica, and based on a total weight of the mixture being 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight; and the silica is between 0.2 and Between 0.8 parts by weight. In another embodiment, the additive includes calcium carbonate, silicon oxide, phosphorus pentoxide, and boron oxide, and based on a total weight of the mixture as 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight. ; Silicon oxide is between 0.2 to 0.8 parts by weight; phosphorus pentoxide is greater than zero and less than or equal to 0.1 parts by weight; and boron oxide is greater than zero and less than or equal to 1 part by weight.

The manufacturing method 10 of modified ferrite magnetic powder according to an embodiment of the present invention is followed by step 12: a calcination step is performed, and the mixture is held at a temperature between 1260 and 1300°C for between 50 and 70 minutes to form One pretreatment. In this step 12, the calcination step is mainly used to make the mixture react at a high temperature to make the pre-treatment product conform to the molecular formula of the strontium ferrite magnetic powder. In one embodiment, a molecular formula of the pretreatment is SrO. nFe ₂ O ₃ , where n is between 5 and 6. In another embodiment, an atmosphere during the calcination step contains 5% oxygen.

In one embodiment, the mixture may further include at least one of a cobalt compound and a lanthanide compound. Specifically, the cobalt element in the cobalt compound or the lanthanum element in the lanthanide compound helps the permanent ferrite magnet made of modified ferrite powder to obtain higher remanence (B _r ) , Coercivity ( _i H _c ) and rectangularity (H _k / _i H _c ). In an example, the cobalt compound is, for example, cobalt oxide (Co ₃ O ₄ ). In another example, the lanthanide is, for example, lanthanum oxide (La ₂ O ₃ ). In this embodiment, a molecular formula of the pre-treatment product formed after the mixture is calcined is (Sr ²⁺ _1-x La ³⁺ _x )O. n(Fe ³⁺ _12-y Co ²⁺ _y ) ₂ O ₃ , where n is between 7 and 9, and x=2ny, where x=2ny is required when La and Co elements replace Sr and Fe respectively Meet the electrical neutrality conditions. In a specific example, x may be between 0.15 and 0.16, for example. In one embodiment, the cobalt compound may be added in the pulverization step described later.

In one embodiment, after step 11 of providing the mixture and before performing the calcination step 12, it further comprises a dehydration step of the mixture, wherein the moisture content of the mixture after the dehydration step is between 18% and Between 24%.

The manufacturing method 10 of modified ferrite magnetic powder according to an embodiment of the present invention is followed by step 13: a coarse crushing step is performed on the pre-processed object to form a plurality of coarsely crushed particles, wherein one of the coarsely crushed particles The average particle size is between 1.5 and 2.0 microns. In this step 13, compared with the conventional technology, the pre-processed product is crushed to a smaller average particle size. For example, the coarse pulverization step of the conventional technology is to pulverize the pre-processed product to an average particle size of about 2.6 microns, while the present invention pulverizes the product to an average particle size of 1.5 to 2.0 microns, which will help reduce Or remove the fine particles with a particle size greater than 0 and less than or equal to 0.05 microns generated in the subsequent fine pulverization step 14. The detailed reasons will be described in the following paragraphs.

The manufacturing method 10 of modified ferrite magnetic powder according to an embodiment of the present invention is finally step 14: performing a fine pulverization step on the coarsely pulverized particles to obtain the modified ferrite magnetic powder, and the modified ferrite magnetic powder An average particle size of is between 0.65 and 0.75 microns, wherein the fine pulverization step includes a wet grinding process for 17 to 20 hours with a plurality of grinding beads having a diameter between 0.25 and 0.33 inches step. In this step 14, compared with the prior art, the coarsely pulverized particles can be finely pulverized using grinding beads with a larger size, and the time required for the fine pulverization step can be reduced, thereby removing or reducing The fine particles produced in step 14 have a particle size greater than 0 and less than or equal to 0.05 microns.

Specifically, in the prior art, grinding beads with a smaller size (for example, 5/32 inches (about 0.156 inches)) are used for fine pulverization. In the case of smaller grinding beads, These coarsely pulverized particles are easily pulverized into fine particles with a particle size greater than 0 and less than or equal to 0.05 microns. In addition, since the conventional technology starts grinding from coarsely pulverized particles with a larger average size, longer fine pulverization is required Time (for example, about 25 hours or more), so the number of fine particles will increase.

On the contrary, the manufacturing method of modified ferrite magnetic powder of the embodiment of the present invention not only uses grinding beads with a larger size (for example, 0.25 to 0.33 inches) for fine grinding, but also because the average particle size is between Coarsely pulverized particles of 1.5 to 2.0 microns begin to undergo a fine pulverization step, so a shorter time for fine pulverization (for example, about 17 to 20 hours or more) is used, so the number of fine particles whose particle size is greater than 0 and less than or equal to 0.05 microns To reduce.

What I want to mention here is that, generally speaking, the smaller the average particle size of the modified ferrite powder, the better the magnetic properties. However, the too small part of the modified ferrite magnetic powder (that is, the above-mentioned fine particles) is harmful to the magnetic properties and molding yield. Specifically, the modified ferrite magnetic powder with an excessively small particle size is likely to produce a non-magnetic phase in the subsequent sintering step, which is harmful to the magnetic properties. On the other hand, a mold is usually used in the subsequent magnetic field alignment forming step to form the modified ferrite magnetic powder into a predetermined shape. The mold is usually provided with a plurality of small holes, so that the water in the modified ferrite powder can flow out when pressurized. However, the too small part of the modified ferrite magnetic powder will block the small holes during the pressurization process, resulting in the need for greater pressure to complete the magnetic field alignment forming step, resulting in the formation of greater stress in the embryo body. Cracks or defects after sintering. Therefore, through the coarse crushing step and the fine crushing step of the above-mentioned specific parameters, the above-mentioned problems can be reduced or avoided.

Another embodiment of the present invention provides a method 20 for manufacturing a modified ferrite magnet, which includes steps 21 to 23: providing a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is implemented as described above The modified ferrite magnetic powder of the example is manufactured by the manufacturing method (step 21); a magnetic field alignment molding step is performed on the modified ferrite magnetic powder to form an embryo body, wherein an alignment magnetic field in the magnetic field alignment molding step The strength is between 1.3 and 1.7 Tesla, a molding pressure is between 3 and 4 tons/cm², and a molding time is between 90 and 110 seconds (step 22); and In the sintering step, the green body is continuously sintered at a temperature between 1220 and 1240° C. for 50 to 70 minutes to obtain the ferrite magnet (step 23).

In the present invention, the implementation details and principles of the above steps of the embodiments will be described in detail below one by one.

The manufacturing method 20 of a modified ferrite magnet according to an embodiment of the present invention first includes step 21: providing a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is the modified iron of any embodiment described above Made by the manufacturing method of ferrite magnetic powder. In this step 21, the modified ferrite magnetic powder is produced by the above-mentioned method 10 for producing modified ferrite magnetic powder.

The manufacturing method 20 of the modified ferrite magnet according to an embodiment of the present invention is followed by step 22: performing a magnetic field alignment molding step on the modified ferrite magnetic powder to form a green body, wherein a step of the magnetic field alignment molding step The intensity of the alignment magnetic field is between 1.3 and 1.7 Tesla, a molding pressure is between 3 and 4 tons/cm², and a molding time is between 90 and 110 seconds. In this step 22, it is mainly to provide a molding pressure and an aligning magnetic field, so that the modified ferrite magnetic powder is molded into a predetermined shape and has a predetermined magnetic field direction. What I want to mention here is that the modified ferrite magnetic powder produced by the manufacturing method 10 of modified ferrite magnetic powder can be molded into an embryo body with a relatively short molding time and has a higher The yield rate.

The final step 23 of the manufacturing method 20 of the modified ferrite magnet of an embodiment of the present invention is a sintering step, and the green body is continuously sintered at a temperature between 1220 and 1240°C for 50 to 70 minutes , To make the ferrite magnet. In this step 23, a sintering step is mainly used to remove water in the embryo body to obtain a ferrite magnet.

What I want to mention here is that since the manufacturing method 20 of the modified ferrite magnet of the embodiment of the present invention uses the modified ferrite magnetic powder produced by the method of manufacturing the modified ferrite magnetic powder of the embodiment of the present invention, Among them, the modified ferrite magnetic powder has a small part with too small particle size. Therefore, the non-magnetic phase is not easily generated in the sintering step, and the clogging problem is not easily generated in the magnetic field alignment molding step, so the magnetic properties and yield can be improved.

What I want to mention here is that, generally speaking, the smaller the average particle size of the modified ferrite magnetic powder, the better the magnetic properties. However, the too small part of the modified ferrite magnetic powder (that is, the above-mentioned fine particles) is harmful to the magnetic properties and molding yield. Specifically, the modified ferrite magnetic powder with an excessively small particle size is likely to produce a non-magnetic phase in the subsequent sintering step, which is harmful to the magnetic properties. On the other hand, a mold is usually used in the subsequent magnetic field alignment forming step to form the modified ferrite magnetic powder into a predetermined shape. The mold is usually provided with a plurality of small holes, so that the water in the modified ferrite powder can flow out when pressurized. However, the too small part of the modified ferrite magnetic powder will block the small holes during the pressurization process, resulting in the need for greater pressure to complete the magnetic field alignment forming step, resulting in the formation of greater stress in the embryo body. Cracks or defects after sintering. Therefore, through the coarse crushing step and the fine crushing step of the above-mentioned specific parameters, the above-mentioned problems can be reduced or avoided.

Here are several examples and comparative examples to illustrate the method of manufacturing modified ferrite magnetic powder in the embodiment of the present invention and the method of manufacturing modified ferrite magnet of the embodiment of the present invention. It does have the above-mentioned effects.

Example 1

First, the main raw material iron oxide powder (Fe ₂ O ₃ ) and another main raw material strontium carbonate (SrCO ₃ ) are blended with the basic composition of SrO·nFe ₂ O ₃ (n=5.9), and 4.9wt% of After the trace additive La ₂ O ₃ and water are mixed, the mixture is mixed and milled with a commercially available ball mill (Ball Mill) with a weight ratio of 1:5 for 2 hours, and then the material is discharged to obtain a mixture in a slurry state. The steel ball is 3/16 in diameter. Inch chromium-free bearing steel balls. Next, the above-mentioned mixture is dehydrated with a commercially available air filter press, and the moisture content of the dehydrated mixture is about 21±3%.

Next, the dehydrated mixture is subjected to a calcination step. Preheat the mixture with a commercially available dryer, where the temperature of the dryer is 300 ± 10 ^o C, the temperature holding time is 30 to 40 minutes, and the moisture content of the mixture after drying is less than 2%. After that, the mixture is calcined in a commercially available rotary kiln to form a pre-processed product. The calcination temperature is 1280±20 ^o C, the calcination time is 1 hour, and the oxygen content in the rotary kiln is about 5%.

The processed material before being calcined in the rotary kiln is sent to the cooling barrel for cooling through the slide pipe connected with the rotary kiln. When the temperature of the pre-processed material drops below 90 ^o C, the coarse pulverization step is carried out by the Matsunaga ball mill (Roller Mill) equipped with the wind separation function of the cyclone collector, so that the average particle size of the coarsely pulverized particles is about Narrow unimodal particle size distribution of 1.5 microns.

After that, based on the total weight of the above-mentioned mixture as 100 parts by weight, each composition was added, including 1.5 parts by weight of Co ₃ O ₄ , 1.0 parts by weight of CaCO ₃ , 0.4 parts by weight of SiO ₂ , and 0.03 parts by weight of P ₂ O ₅ and 0.05 parts by weight of B ₂ O _{3 are put} into a ball mill, and the weight ratio of the balls is 1:12 in the ball mill (Ball Mill), and the wet milling is performed for 17 hours to further carry out a fine pulverization step to make the modified iron The average particle size of the ferrite magnetic powder is about 0.75 microns, and the steel balls are chromium-free bearing steel balls with a diameter of 7/25 inches.

Next, proceed to the (wet) magnetic field alignment molding step. Using a commercially available 25-ton semi-automatic wet magnetic field molding machine, the modified ferrite powder is subjected to magnetic field alignment molding of 20 embryos, and the alignment magnetic field strength is 1.5 For Tesla, the molding pressure is 3.5 tons/cm 2 (Ton/cm ² ), and the molding blank size is Φ26.5 and the thickness is about 13mm. In Example 1, the average wet magnetic field molding time required for forming 20 embryos was 92 seconds, and the average yield of the embryos was 84%.

Finally, a sintering step is performed to continue sintering the green body at a temperature between 1220 and 1240° C. for 60 minutes to obtain the ferrite magnet of Example 1.

Examples 2 to 5 and Comparative Examples 1 to 6

Examples 2 to 5 and Comparative Examples 1 to 6 are roughly the same as Example 1, except that the difference lies in the average particle size of the coarsely pulverized particles, the ratio of additives, the time of fine pulverization, the size of the grinding beads used, and the modification The particle size of ferrite powder is different, as shown in Table 1 below.

Table I Average particle size of coarsely pulverized particles (μm) Mixture or additive ratio (parts by weight) Fine crushing time (hr) Fine grinding beads size (inch) Modified ferrite magnetic powder particle size (micron) Co ₃ O ₄ CaCO ₃ SiO ₂ P ₂ O ₅ B ₂ O ₃ Comparative example 1 2.6 1.5 1.0 0.4 0.03 0.05 25 5/32 0.75 Comparative example 2 2.6 1.2 1.0 0.4 0.03 0.05 25 5/32 0.75 Comparative example 3 2.6 1.2 1.0 0.4 0 0 25 5/32 0.75 Comparative example 4 2.6 1.2 1.0 0.4 0 0 30 5/32 0.65 Comparative example 5 2.6 1.2 1.0 0.4 0.03 0.05 28.5 7/25 0.75 Comparative example 6 1.5 1.2 1.0 0.4 0.03 0.05 14.5 5/32 0.75 Example 1 1.5 1.5 1.0 0.4 0.03 0.05 17 7/25 0.75 Example 2 1.5 1.2 1.0 0.4 0.03 0.05 17 7/25 0.75 Example 3 1.5 1.2 1.0 0.4 0 0 17 7/25 0.75 Example 4 1.5 1.2 1.0 0.4 0 0 20 7/25 0.65 Example 5 2.0 1.2 1.0 0.4 0.03 0.05 20 7/25 0.75

Next, use commercially available instruments (NIM-2000, Chinese Academy of Metrology)

Next, use a commercially available instrument (NIM-2000 BH Loop Tracer of the Chinese Academy of Metrology) to measure the various magnetic properties of each of the 20 ferrite magnets in each embodiment and comparative example, and calculate the average value. In Table II below.

Table II B _{r b} H _c i H _c ( BH ) _m H _k / _i H _c Molding time Molding yield unit (G) (Oe) (Oe) (MGOe) (%) (second) (%) Comparative example 1 4538 4352 4563 4.93 93.2 132 70 Comparative example 2 4425 4285 4479 4.86 92.8 134 68 Comparative example 3 4378 4236 4412 4.79 90.8 145 62 Comparative example 4 4489 4370 4575 4.88 91.8 174 51 Comparative example 5 4401 4255 4435 4.82 92.0 140 64 Comparative example 6 4389 4251 4430 4.83 92.1 140 66 Example 1 4562 4378 4582 4.98 95.6 92 84 Example 2 4517 4328 4533 4.93 95.1 95 83 Example 3 4505 4313 4525 4.91 94.8 97 81 Example 4 4541 4405 4621 4.96 93.5 105 77 Example 5 4512 4320 4528 4.92 95.0 96 82

According to Japan TDK FB9B, the median values of its specifications are: B _r =4500G; _b H _c =4300Oe; _i H _c =4500Oe; (BH) _max =4.9MGOe. If it is lower than the median value of the above specifications, it means that the ferrite magnet has not reached the commercial standard. Therefore, it can be seen from Table 2 above that Comparative Examples 2 to 6 did not meet the requirements of the median value of the Japanese TDK FB9B specification, while all Examples 1 to 5 and Comparative Example 1 met the requirements of the median value of the Japanese TDK FB9B specification.

However, the molding time of Comparative Examples 1 to 6 is not only higher than that of Examples 1 to 5, but the molding yield of Comparative Examples 1 to 6 is also lower than that of Examples 1 to 5. For general industrial considerations, the molding time must be less than 120 seconds, and the yield rate must be above 75% to qualify as a process. It is also worth mentioning that since the fine particles with a particle size greater than 0 and less than or equal to 0.05 microns have a positive correlation with the molding time, it can be seen that the content of fine particles in Examples 1 to 5 is less than that in Comparative Examples 1 to 6. The content of particles.

On the other hand, referring to Comparative Example 1 and Examples 2 to 5, even under the premise of using a composition with less cobalt oxide content (for example, 1.2 parts by weight), the production of the modified ferrite magnet of the embodiment of the present invention The magnetic properties of the ferrite magnet prepared by the method also meet the requirements of the median value of the Japanese TDK FB9B specification. That is to say, Comparative Example 1 can actually meet the requirements of the Japanese TDK FB9B standard by adding more cobalt oxide content. Because cobalt is a precious element, not only the output is scarce, but the price is also high. Therefore, the manufacturing method of the modified ferrite magnet of the embodiment of the present invention can also effectively reduce the manufacturing cost.

On the other hand, please refer to Comparative Examples 5 and 6. For Comparative Example 5, it uses 7/25 inch grinding beads in the fine pulverization step. However, since the coarsely pulverized particles need to be ground from 2.6 microns to 0.75 microns, it takes a longer time. There are many fine particles, so it cannot effectively reduce the molding time and improve the yield. In addition, for Comparative Example 6, a 5/32-inch grinding bead was used to finely pulverize coarsely pulverized particles of 1.5 microns. Due to the small size of the 5/32-inch grinding beads, more fine particles will be generated, which cannot effectively reduce the molding time and increase the yield. It can be seen that in the manufacturing method of the modified ferrite magnetic powder and the manufacturing method of the modified ferrite magnet of the embodiment of the present invention, the parameters of the coarse crushing step and the fine crushing step need to be possessed at the same time to achieve the desired effect of the present invention. .

To sum up, the manufacturing method of the modified ferrite magnet of the embodiment of the present invention can save the time required for forming, and the yield rate is greater than 75%, and it is good for the remanence, coercivity, rectangular shape of the permanent ferrite magnet The degree and the degree of magnetic field alignment also have a significant improvement effect.

Although the present invention has been disclosed in preferred embodiments, it is not intended to limit the present invention. Anyone who is familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope of the attached patent application.

10: method 11~14: Steps 20: Method 21~23: Steps

Figure 1: A flow block diagram of a manufacturing method of modified ferrite powder according to an embodiment of the present invention. Figure 2: A block diagram of a process flow of a manufacturing method of a modified ferrite magnet according to an embodiment of the present invention.

10: method

11~14: Steps

Claims (10)

A manufacturing method of modified ferrite magnetic powder, which comprises the steps: Providing a mixture, wherein the mixture includes iron oxide powder and a strontium compound; Performing a calcination step, holding the mixture at a temperature between 1260 and 1300°C for between 50 and 70 minutes to form a pre-treatment product; Performing a coarse pulverization step on the pretreatment to form a plurality of coarsely pulverized particles, wherein an average particle size of the coarsely pulverized particles is between 1.5 to 2.0 microns; and A fine pulverization step is performed on the coarsely pulverized particles to obtain the modified ferrite magnetic powder. The modified ferrite magnetic powder has an average particle size between 0.65 and 0.75 microns, wherein the fine pulverization step includes A plurality of grinding beads having a diameter between 0.25 and 0.33 inches are subjected to a wet grinding step for between 17 and 20 hours. The manufacturing method of modified ferrite magnetic powder as described in item 1 of the scope of patent application, wherein a molecular formula of the pre-treatment is SrO. nFe ₂ O ₃ , where n is between 5 and 6. According to the manufacturing method of the modified ferrite magnetic powder described in the first item of the patent application, the mixture further contains at least one of a cobalt compound and a lanthanide compound. The manufacturing method of modified ferrite magnetic powder as described in item 3 of the scope of patent application, wherein a molecular formula of the pre-treatment is (Sr ²⁺ _1-x La ³⁺ _x )O. n(Fe ³⁺ _12-y Co ²⁺ _y ) ₂ O ₃ , where n is between 7 and 9, and x=2ny. The manufacturing method of modified ferrite magnetic powder as described in item 1 of the scope of patent application, wherein the step of providing the mixture further includes: providing an additive, wherein the additive includes calcium carbonate, silicon oxide, and phosphorus pentoxide And at least one of boron oxide. The manufacturing method of modified ferrite magnetic powder as described in item 5 of the scope of patent application, wherein the additives include calcium carbonate and silicon oxide, and based on a total weight of the mixture as 100 parts by weight, the calcium carbonate is between 0.5 To 1.5 parts by weight; and the silicon oxide is between 0.2 to 0.8 parts by weight. The manufacturing method of modified ferrite magnetic powder described in item 5 of the scope of patent application, wherein the additives include calcium carbonate, silicon oxide, phosphorus pentoxide and boron oxide, and a total weight of the mixture is 100 parts by weight In total, calcium carbonate is between 0.5 and 1.5 parts by weight; silicon oxide is between 0.2 and 0.8 parts by weight; phosphorus pentoxide is greater than zero and less than or equal to 0.1 parts by weight; and boron oxide is greater than zero and less than Equal to 1 part by weight. The manufacturing method of modified ferrite magnetic powder as described in item 1 of the scope of patent application, wherein after the step of providing the mixture and before the calcination step, it further comprises a dehydration step of the mixture, wherein the dehydration step is performed The moisture content of the latter mixture is between 18% and 24%. According to the manufacturing method of the modified ferrite magnetic powder described in item 1 of the scope of patent application, an atmosphere of the calcination step contains 5% oxygen. A manufacturing method of modified ferrite magnet, which comprises the steps: Provided is a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is produced by the manufacturing method of the modified ferrite magnetic powder as described in any one of items 1 to 9 in the scope of patent application; A magnetic field alignment molding step is performed on the modified ferrite magnetic powder to form an embryo body, wherein an alignment magnetic field intensity of the magnetic field alignment molding step is between 1.3 and 1.7 Tesla, and a molding pressure is between Between 3 and 4 tons/cm², and a molding time between 90 and 110 seconds; and A sintering step is performed to continuously sinter the green body at a temperature between 1220 and 1240° C. for between 50 and 70 minutes to obtain a ferrite magnet.

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