TWI686356B - 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

Method for manufacturing modified ferrite magnetic powder and magnet

The invention relates to a method for manufacturing magnetic powder and magnet, in particular to a method for manufacturing modified ferrite magnetic powder and a method for manufacturing modified ferrite magnetic powder.

In recent years, with the miniaturization, weight reduction, and high performance of electronic components, permanent magnet ferrite magnets composed of oxides have also been required to have high magnetic characteristics. As an index of the magnetic characteristics of the permanent ferrite magnet, the residual magnetization (B _r ) and the coercive magnetic force ( _i H _c ) are generally used as indexes. In order to achieve the characteristics of high remanence and high coercive force, the composition of elemental components in permanent magnet ferrite magnets has been under discussion.

In addition, in addition to the high remanence and high coercive force of permanent ferrite magnets, the squareness (Sauareness ratio) should also be as high as possible (squareness: when 90% of B _r , its magnetic field value ( H _k ) relative to _i H _c . That is, if H _k / _i H _{c is} high, the demagnetization caused by the external magnetic field and temperature changes will be relatively small, which also represents the magnetic field alignment of the magnet itself Higher, so you can get more stable magnetic characteristics. In addition, another indicator for the production of permanent ferrite magnets is to reduce the occurrence of cracks in the embryo of the magnet after the magnetic field is formed or the magnet during the sintering process. The probability of defects occurs to further improve the yield of permanent ferrite magnets. However, the existing manufacturing methods of permanent ferrite magnets cannot 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 magnets to solve the problems existing in conventional technology.

An object of the present invention is to provide a method for manufacturing ferrite magnetic powder and magnet, which utilizes a combination of specific coarse pulverization steps and fine pulverization steps 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 formation of non-magnetic phases in the ferrite magnet that are not conducive to magnetic properties, and can increase the yield of the ferrite magnet, thereby reducing production costs.

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

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

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

In one embodiment of the present invention, a molecular formula system of the pretreatment (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, in the step of providing the mixture, the method further includes: providing an additive, wherein the additive includes at least one of calcium carbonate, silicon oxide, phosphorus pentoxide, and boron oxide.

In one embodiment of the present invention, the additive includes calcium carbonate and silicon oxide, and based on a total weight of the mixture of 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight; Between 0.2 and 0.8 parts by weight.

In one embodiment of the present invention, the additive includes calcium carbonate, silicon oxide, phosphorus pentoxide, and boron oxide, and based on the total weight of the mixture as 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight Between; the silicon oxide system is between 0.2 and 0.8 parts by weight; the phosphorus pentoxide system is greater than zero and less than or equal to 0.1 parts by weight; and the boron oxide system 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 the calcination step, a dehydration step is further included, wherein the moisture content of the mixture after the dehydration step is 18 % To 24%.

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

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 passed through any of the above embodiments The modified ferrite magnetic powder is manufactured by a method of performing a magnetic field alignment molding step on the ferrite magnetic powder to form a embryo body, wherein an alignment magnetic field strength of the magnetic field alignment molding step is between 1.3 and 1.7 Between Tesla, a molding pressure is between 3 and 4 tons/cm 2, and a molding time is between 90 and 110 seconds; and a sintering step is performed to the embryo body between 1220 A temperature between 1240°C and continuous sintering for 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 comprehensible, the preferred embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings, which will be described in detail below. Furthermore, the terms of direction mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inner, outer, side, surrounding, center, horizontal, horizontal, vertical, longitudinal, axial, The radial direction, the uppermost layer or the lowermost layer, etc., are only the directions referring to the attached drawings. Therefore, the directional terminology is used to illustrate and understand the present invention, not to limit the present invention.

Referring to FIG. 1, a method 10 for manufacturing modified ferrite magnetic powder according to an embodiment of the present invention mainly includes the following steps 11 to 14: providing a mixture in which the mixture includes iron oxide powder and a strontium compound (step 11); performing a calcination step, the mixture is maintained at a temperature between 1260 and 1300°C for 50 to 70 minutes to form a pre-treatment (step 12); the pre-treatment is subjected to a coarse crushing Step to form a plurality of coarsely crushed particles, wherein an average particle size of the coarsely crushed particles is between 1.5 and 2.0 microns (step 13); and a fine crushing step is performed on the coarsely crushed particles, to The modified ferrite magnetic powder is obtained, and an average particle size of the modified ferrite magnetic powder is between 0.65 and 0.75 micrometers, wherein the fine pulverizing step includes a diameter of between 0.25 and 0.33 inches. The grinding beads are 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 embodiment will be described in detail one by one below.

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

In an embodiment, in step 11 of providing the mixture, an additive may be 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. The weight percentages involved are based on the total weight of the mixture being 100 parts by weight. In one embodiment, the additive may be added to the ball mill during the crushing step.

Calcium carbonate is an element used to promote grain growth. In the present invention, the amount of calcium carbonate added is, for example, between 0.5 and 1.5 parts by weight. When the amount of calcium carbonate added is too large (eg, more than 1.5 parts by weight), the subsequent During the sintering step performed to form a ferrite magnet, excessive grain growth occurs, resulting in a reduction in coercive force. On the other hand, when the amount of calcium carbonate added is too small (for example, less than 0.5 parts by weight), the phenomenon of grain growth will be excessively suppressed, which in turn leads to insufficient increase in the orientation that occurs simultaneously with grain growth, which ultimately leads to residual Magnetic (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 too little silicon oxide is added (for example, less than 0.2 parts by weight), excessive grain growth occurs during the sintering stage, resulting in a decrease in coercive force. When too much silicon oxide is added (for example, greater than 0.8 parts by weight), the grain growth in the sintering stage will be excessively eliminated, resulting in insufficient improvement of the orientation that occurs concurrently with the grain growth, and ultimately resulting in residual magnetization (B _r ) decline.

The addition of phosphorus pentoxide can increase the squareness (H _k / _i H _c ), remanence (B _r ) and coercive force ( _i H _c ). The added amount of phosphorus pentoxide in the present invention may 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 producing a sintered magnet composed of permanent ferrite magnets and at the same time increase the residual magnetization (B _r ) and the coercive force ( _i H _c ). Oxidation in the present invention The added amount of boron 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 of 100 parts by weight, the calcium carbonate is between 0.5 and 1.5 parts by weight; and the silica is 0.2 to 0.5 parts by weight. 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 of 100 parts by weight, the 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 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: performing a calcination step, and maintaining the mixture at a temperature of 1260 to 1300°C for 50 to 70 minutes to form A pre-treatment. In this step 12, the calcination step is mainly used to make the mixture react at a high temperature to perform the pretreatment to conform to the molecular formula of the strontium ferrite magnetic powder. In one embodiment, a molecular formula of the pretreatment system is SrO. nFe ₂ O ₃ , where n is between 5 and 6. In another embodiment, an atmosphere during the calcination step includes 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 can help the permanent ferrite magnet made of the modified ferrite magnetic powder to obtain a higher remanence (B _r ) , Coercive force ( _i H _c ) and squareness (H _k / _i H _c ). In one 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 system (Sr ²⁺ _1-x La ³⁺ _x ) O of the pretreatment formed after the calcination step of the mixture. 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 the elements La and Co replace Sr and Fe, respectively Satisfied electrical neutrality conditions. In a specific example, x may be between 0.15 and 0.16, for example. In one embodiment, the cobalt compound can 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, a dehydration step is further included, 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: performing a coarse pulverization step on the pretreatment to form a plurality of coarsely pulverized particles, wherein one of the coarsely pulverized particles The average particle size is between 1.5 and 2.0 microns. In this step 13, the pretreated product is crushed to a smaller average particle size compared to the conventional technology. For example, the coarse pulverization step of the conventional technology is to pulverize the pre-treatment to an average particle size of about 2.6 microns, while the present invention pulverizes to an average particle size between 1.5 and 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 reason will be described in the following paragraphs.

The manufacturing method 10 of the modified ferrite magnetic powder according to an embodiment of the present invention is the final step 14: performing a fine pulverization step on the coarsely crushed particles to obtain the modified ferrite magnetic powder, and the modified ferrite magnetic powder Has an average particle size between 0.65 and 0.75 microns, wherein the fine pulverization step includes performing a wet grinding between 17 and 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 conventional technique, the coarsely crushed particles can be subjected to a fine grinding step using larger size grinding beads, and the time required for the fine grinding step can be reduced, thereby removing or reducing the fine grinding The fine particles with a particle size greater than 0 and less than or equal to 0.05 microns are produced in step 14.

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

On the contrary, the method for manufacturing modified ferrite magnetic powder according to 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 pulverization, but also because the average particle size is between The coarsely crushed particles of 1.5 to 2.0 microns start the fine crushing step, so a shorter fine crushing time (for example, about 17 to 20 hours or more) is used, so the number of fine particles with a particle size greater than 0 and less than or equal to 0.05 microns is more To reduce.

It should be mentioned here that, generally speaking, the smaller the average particle size of the modified ferrite magnetic powder, the better the magnetic characteristics. However, the portion of the modified ferrite magnetic powder having an excessively small particle size (that is, the above-mentioned fine particles) is detrimental to the magnetic properties and molding yield. Specifically, the modified ferrite magnetic powder with a particle size that is too small is likely to generate a non-magnetic phase in the subsequent sintering step, which is detrimental to the magnetic properties. On the other hand, in the subsequent magnetic field alignment molding step, a mold is usually used 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 magnetic powder flows out when pressurized. However, the excessively small part of the modified ferrite magnetic powder will block the small holes during the pressurization process, resulting in a greater pressure to complete the magnetic field alignment molding step, resulting in a larger stress in the embryo body. Cracks or defects after sintering. Therefore, the coarse grinding step and the fine grinding step with the above specific parameters can further reduce or avoid the above-mentioned problems.

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 Example of the modified ferrite magnetic powder manufacturing method (step 21); the modified ferrite magnetic powder is subjected to a magnetic field alignment forming step to form a embryo, wherein the magnetic field alignment forming step of an alignment magnetic field The strength is between 1.3 and 1.7 Tesla, a molding pressure is between 3 and 4 tons/cm 2, and a molding time is between 90 and 110 seconds (step 22); and a In the sintering step, the green body is continuously sintered at a temperature between 1220 and 1240°C for 50 to 70 minutes to prepare the ferrite magnet (step 23).

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

A method 20 for manufacturing a modified ferrite magnet according to an embodiment of the present invention is first step 21: providing a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is modified iron according to any of the embodiments 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-described method 10 for producing modified ferrite magnetic powder.

A method 20 for manufacturing a modified ferrite magnet according to an embodiment of the present invention is followed by step 22: performing a magnetic field alignment forming step on the modified ferrite magnetic powder to form a embryo, wherein the magnetic field alignment forming step The alignment magnetic field strength is between 1.3 and 1.7 Tesla, a molding pressure is between 3 and 4 tons/cm 2, and a molding time is between 90 and 110 seconds. In this step 22, the forming pressure and the aligning magnetic field are mainly provided to form the modified ferrite magnetic powder into a predetermined shape and have a predetermined magnetic field direction. It should be mentioned here that since the modified ferrite magnetic powder produced by the manufacturing method 10 of modified ferrite magnetic powder can be molded into a embryo body using a lower molding time, and has a higher Yield.

The manufacturing method 20 of the modified ferrite magnet according to an embodiment of the present invention is finally step 23: performing a sintering step, and continuously sintering the embryo body at a temperature between 1220 and 1240°C for 50 to 70 minutes To produce the ferrite magnet. In this step 23, a ferrite magnet is prepared by mainly removing the moisture in the embryo body through a sintering step.

It should be mentioned here that, since the method 20 for manufacturing modified ferrite magnets according to embodiments of the present invention uses the modified ferrite magnetic powder produced by the method for manufacturing modified ferrite magnetic powders according to embodiments of the present invention, Among these modified ferrite powders, the particle size is too small. 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.

It should be mentioned here that, generally speaking, the smaller the average particle size of the modified ferrite magnetic powder, the better the magnetic characteristics. However, the portion of the modified ferrite magnetic powder having an excessively small particle size (that is, the above-mentioned fine particles) is detrimental to the magnetic properties and molding yield. Specifically, the modified ferrite magnetic powder with a particle size that is too small is likely to generate a non-magnetic phase in the subsequent sintering step, which is detrimental to the magnetic properties. On the other hand, in the subsequent magnetic field alignment molding step, a mold is usually used 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 magnetic powder flows out when pressurized. However, the excessively small part of the modified ferrite magnetic powder will block the small holes during the pressurization process, resulting in a greater pressure to complete the magnetic field alignment molding step, resulting in a larger stress in the embryo body. Cracks or defects after sintering. Therefore, the coarse grinding step and the fine grinding step with the above specific parameters can further reduce or avoid the above-mentioned problems.

Several examples and comparative examples are given below to illustrate the method for manufacturing modified ferrite magnetic powder according to the embodiment of the invention and the method for manufacturing modified ferrite magnetic powder according to the embodiment of the invention. It does have the aforementioned 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 compounded with the basic composition of SrO·nFe ₂ O ₃ (n=5.9), while adding 4.9wt% After mixing the trace additive La ₂ O ₃ and water, it was mixed with a commercial ball mill (Ball Mill) with a weight ratio of 1:5 for 2 hours and then discharged to obtain a mixture in the state of slurry. The diameter of the steel ball was 3/16 Inch chrome-free bearing steel balls. Next, the above mixture was dehydrated with a commercially available air filter, and the water content of the dehydrated mixture was 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 holding time is 30 to 40 minutes, and the moisture content of the mixture after drying is less than 2%. Thereafter, the mixture was placed in a commercial rotary kiln calcined to form a pretreatment composition, the calcination temperature is 1280 ± 20 ^o C, the calcination time was one hour, and calcined to about 5% of the oxygen content in the rotary kiln.

The processed material before being calcined by the rotary kiln is sent to a cooling barrel through a slide pipe connected to the rotary kiln for cooling. When the temperature of the pretreated product drops below 90 ^o C, the coarse crushing step is carried out by a Roller Mill equipped with a cyclone collector air separation function, so that the average particle size of the coarsely crushed particles is about The narrow unimodal particle size distribution of 1.5 microns.

After that, based on the total weight of the above mixture as 100 parts by weight, each composition is added again, 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 were transferred} to a ball mill, and the ball mill (Ball Mill) with a ball weight ratio of 1:12, wet grinding for 17 hours to further perform a fine grinding step to make the modified iron The average particle size of the ferrite magnetic powder is between 0.75 microns, and the steel ball is a chrome-free bearing steel ball with a diameter of 7/25 inches.

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

Finally, a sintering step is performed, and the green body is continuously sintered 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 substantially the same as Example 1, except that the difference is the average particle size of coarsely pulverized particles, additive ratio, fine pulverization time, size and modification of grinding beads used The particle size of the ferrite magnetic powder is different, as shown in Table 1 below.

Table I

Next, use commercially available instruments (Chinese Academy of Metrological Sciences NIM-2000

Next, using a commercially available instrument (Chinese Academy of Metrological Sciences NIM-2000 BH Loop Tracer) to measure various magnetic properties of each of the 20 ferrite magnets in each of the Examples and Comparative Examples, and the average value is calculated. In Table 2 below.

Table II

According to Japan's TDK FB9B, the median values of their 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, as can be seen from Table 2 above, Comparative Examples 2 to 6 did not meet the median requirement of the Japanese TDK FB9B specification, and all of Examples 1 to 5 and Comparative Example 1 met the median requirement of the Japanese TDK FB9B specification.

However, the molding times of Comparative Examples 1 to 6 are not only higher than those of Examples 1 to 5, but also the molding yields of Comparative Examples 1 to 6 are lower than those of Examples 1 to 5. For general industry considerations, the molding time needs to be less than 120 seconds, and the yield must be more than 75% to be a qualified 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 are positively correlated with the molding time, it can be seen that the content of fine particles in Examples 1 to 5 is less than that of Comparative Examples 1 to 6. The content of particles.

On the other hand, please refer to Comparative Example 1 and Examples 2 to 5, even under the premise of using a composition with a relatively low 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 magnets produced by the method also meet the median requirements of the Japanese TDK FB9B specifications. That is to say, Comparative Example 1 can actually achieve the median requirement of the Japanese TDK FB9B specification by adding more cobalt oxide content. Because the cobalt element is a precious element, not only is the output scarce, but also the price is high. Therefore, the method for manufacturing the modified ferrite magnet according to 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 grinding step. However, since it needs to grind the coarsely crushed particles from 2.6 microns to 0.75 microns, it takes longer time. There are many fine particles, so it can not effectively reduce the molding time and improve the yield. In addition, for Comparative Example 6, it is a fine grinding step of coarsely pulverized particles of 1.5 microns using 5/32 inch grinding beads. Due to the smaller size of the 5/32 inch grinding beads, more fine particles are also produced, so it is impossible to effectively reduce the molding time and improve the yield. It can be seen that the method for manufacturing the modified ferrite magnetic powder and the method for manufacturing the modified ferrite magnet according to the embodiments of the present invention need to have both the parameters of the coarse grinding step and the fine grinding step in order to achieve the desired effect of the present invention .

In summary, the method for manufacturing modified ferrite magnets of the embodiments of the present invention can save the time required for molding, and the yields are all greater than 75%, and the residual magnetism, coercive force, rectangular shape of permanent magnet ferrite magnets Degrees and magnetic field alignment also play a significant role in improving.

Although the present invention has been disclosed in preferred embodiments, it is not intended to limit the present invention. Anyone who is familiar with this skill 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 as defined in the scope of the attached patent application.

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

Fig. 1: Flow block diagram of a method for manufacturing modified ferrite magnetic powder according to an embodiment of the invention. Fig. 2: Flow chart of a method for manufacturing a modified ferrite magnet according to an embodiment of the invention.

10: Method

11~14: Steps

Claims (8)

A method for manufacturing modified ferrite magnetic powder, comprising the steps of: providing a mixture, wherein the mixture includes iron oxide powder and a strontium compound; performing a calcination step, and maintaining the mixture at a temperature between 1260 and 1300°C The temperature is between 50 and 70 minutes to form a pre-treated product; the pre-treated product is subjected to a coarse crushing step to form a plurality of coarsely crushed particles, wherein an average particle size of the coarsely crushed particles is between 1.5 to 2.0 microns; and performing a fine crushing step on the coarsely crushed particles to obtain the modified ferrite magnetic powder, the average particle size of the modified ferrite magnetic powder is between 0.65 and 0.75 microns , Wherein the fine pulverization step includes a wet grinding step with multiple grinding beads having a diameter between 0.25 and 0.33 inches for between 17 and 20 hours. As described in the first paragraph of the scope of patent application for the production method of modified ferrite magnetic powder, wherein the molecular formula of the pretreatment is SrO. nFe ₂ O ₃ , where n is between 5 and 6. The method for manufacturing modified ferrite magnetic powder as described in item 1 of the patent application range, wherein the mixture further comprises at least one of a cobalt compound and a lanthanide compound. The method for manufacturing modified ferrite magnetic powder as described in item 3 of the patent application scope, wherein the 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, x is between 0.15 and 0.16, and x=2ny. The method for manufacturing modified ferrite magnetic powder as described in item 1 of the patent application scope, wherein the step of providing the mixture further comprises: providing an additive, wherein the additive comprises calcium carbonate, silicon oxide, and phosphorus pentoxide And at least one of boron oxide. The method for manufacturing modified ferrite magnetic powder as described in item 5 of the patent application scope, wherein the additive contains calcium carbonate and silicon oxide, and the total weight of the mixture is 100 weight In terms of parts, calcium carbonate is between 0.5 and 1.5 parts by weight; and silicon oxide is between 0.2 and 0.8 parts by weight. The method for manufacturing modified ferrite magnetic powder as described in item 5 of the patent application scope, wherein the additive comprises calcium carbonate, silicon oxide, phosphorus pentoxide and boron oxide, and the total weight of the mixture is 100 parts by weight 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. A method for manufacturing modified ferrite magnets, comprising the steps of: providing a modified ferrite magnetic powder, wherein the modified ferrite magnetic powder is modified as described in any of items 1 to 7 of the patent application Manufactured by a method for manufacturing a quality ferrite magnetic powder; performing a magnetic field alignment molding step on the modified ferrite magnetic powder to form a embryo body, wherein an alignment magnetic field strength of the magnetic field alignment molding step is between 1.3 and 1.7 Between Tesla, a molding pressure is between 3 and 4 tons/cm 2, and a molding time is between 90 and 110 seconds; and a sintering step is performed to the embryo body between 1220 A temperature between 1240°C and continuous sintering for 50 to 70 minutes to produce a ferrite magnet.

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