JP6164892B2 - Method for producing hexagonal ferrite magnetic powder - Google Patents

Description

  The present invention relates to a hexagonal ferrite magnetic powder suitable for high-density magnetic recording media, a production method for obtaining a molded body of a hexagonal ferrite magnetic powder, and a molded body of a hexagonal ferrite magnetic powder.

  In order to further increase the density of the coating type magnetic recording medium, fine magnetic powder is required. Conventionally used metal magnetic powder is a magnetic powder having excellent magnetic properties such as high saturation magnetization and large coercive force. However, as it becomes finer, it has become difficult to maintain both its magnetic properties for a long period of time (weather resistance) and to achieve excellent magnetic properties.

  In addition, the recent improvement in characteristics of magnetic heads (particularly reproducing heads) has made it possible to sufficiently use magnetic powders that do not have saturation magnetization as high as that of metal magnetic powders.

  Against this background of technology, ferrite-type magnetic powders that have been used only for specific applications due to their low saturation magnetization, but excellent stability of magnetic properties, especially hexagonal ferrite magnetic powders, It has attracted attention as a magnetic powder for high density magnetic recording media.

  In addition, in the process of studying hexagonal ferrite magnetic powder suitable for high-density magnetic recording, to obtain hexagonal ferrite magnetic powder that has fine and high magnetic properties and can be suitably used for high-density magnetic recording media. Has been found to be preferred to use the glass crystallization method.

  Here, the glass crystallization method will be briefly described. First, a ferrite component, which is a magnetic material, and a glass forming component (also referred to as a “non-magnetic component”) are melted at a high temperature. When cooled from the molten state and solidified, it becomes a precursor which is an amorphous body (glass body). The precursor is then heat treated. By performing heat treatment, hexagonal ferrite magnetic powder is precipitated in the precursor. The precipitated hexagonal ferrite magnetic powder can be obtained by separating the precursor glass by removing it with an acid or the like.

  The hexagonal ferrite magnetic powder here becomes the material of the high-density magnetic recording medium. When the glass crystallization method is used, hexagonal ferrite is crystal-grown in a high-temperature glass body, so that the crystal growth is easy to control, and in particular, it is easy to grow the crystal in the C-axis direction. There is an advantage that ferrite can be obtained.

  Furthermore, in order to obtain hexagonal ferrite having excellent magnetic properties, methods for improving the composition and the like are known. For example, Patent Literature 1 discloses at least a hexagonal ferrite forming raw material and a tetravalent element (M4) of 0.004 to 0.045 atoms with respect to one iron (Fe) atom contained in the hexagonal ferrite forming raw material. A method for producing a hexagonal ferrite magnetic powder comprising mixing one material, melting the obtained raw material mixture, rapidly cooling it to an amorphous body, and then heat-treating the amorphous body to precipitate hexagonal ferrite Is disclosed.

  As a method for improving the productivity of the amorphous body, for example, there is a method disclosed in Patent Document 2. When trying to obtain an amorphous body with high productivity by batch processing, it is efficient to process by melting as much raw material as possible. Therefore, Patent Document 2 describes a method in which after the first raw material is melted and the volume is reduced, the heat-resistant container (crucible) is taken out of the furnace, and the raw material is additionally added thereto to increase the melting amount per batch. ing.

  The batch process is a process performed by dividing the production amount into a certain division and making it a production unit in one batch (also referred to as one lot). The advantage of this treatment is that the desired composition can be easily obtained because the blending of raw materials and the like can be adjusted within one batch. However, if the composition is different from the desired one, the batch is discarded or reprocessed because it cannot be used in the next step.

  In batch processing, when a high-frequency melting furnace is used to melt the raw material, the furnace temperature can be quickly adjusted by adjusting the amount of current flowing through the coil, so the furnace is cooled and added. This is easy, and there is a report used when producing hexagonal ferrite (Patent Document 1).

  In this way, in order to obtain hexagonal ferrite with excellent magnetic properties, finding a new composition and improving productivity, we adopted an increase in throughput and a more efficient heating method in batch processing. It was known to do.

JP 2006-5299 A JP 2012-25598 A

  In the market of high-density magnetic recording media, the demand for high characteristics and a stable supply amount is naturally strong. To that end, it is urgent to supply hexagonal ferrite magnetic powder with stable characteristics. Even if a new composition is found in order to improve the magnetic properties, various tests are required to produce a product that can be stably supplied, and a long time and cost are required.

  On the other hand, hexagonal ferrite magnetic powder is a high-quality magnetic powder even with an existing composition. However, when an industrial production method is attempted, fluctuation (variation) occurs in the magnetic properties of the magnetic powder obtained even with almost the same raw material composition. Industrially, it is necessary to supply magnetic powder having stable quality (magnetic characteristics) in which fluctuation (variation) in magnetic characteristics is suppressed.

  Accordingly, there has been a demand for the development of a stable quality (magnetic property) magnetic powder and a production method capable of supplying it even with an existing composition in a stable hexagonal ferrite magnetic powder with high properties.

  The present invention has been conceived in view of the above problems. In the production of hexagonal ferrite magnetic powder, the composition is set in advance, and raw materials of various elements are blended with the composition as a target. As these various elements, iron, barium, and boron are mainly used, and a composition ratio that expresses their composition in terms of molar ratio is set in advance. If it is an industrial composition, the magnetic powder can be manufactured substantially according to the composition ratio.

  However, even from the same raw material, the composition ratio deviation, which is a comparison difference between the batches of the magnetic powder, may occur extremely small. The present inventors have found that even this very small compositional deviation causes a variation in the overall magnetic characteristics, and as a result is an impeding factor for providing a hexagonal ferrite magnetic powder having stable characteristics.

  Furthermore, the magnetic characteristics of the hexagonal ferrite magnetic powder have been found to be important to reduce the deviation of the composition ratio of boric acid in the glass raw material that hardly remains when used as the magnetic powder.

As a result of intensive studies, the present inventors have found the following means. That is, the method for producing hexagonal ferrite magnetic powder according to the present invention is as follows.
A step of weighing the ferrite raw material and the glass raw material and the additive substance;
A mixing step of mixing the ferrite raw material and the glass raw material and the additive substance using a mixer with a plurality of blades to obtain a mixed raw material powder;
A molding step of forming the mixed raw material powder into a molded body using a pan pelletizer;
A drying step of drying the molded body at 200 ° C. or higher to obtain a dried molded body;
A melting step of melting the dried molded body to form a molten metal;
A cooling step of obtaining a precursor by cooling the molten metal;
Heat treating the precursor to precipitate ferrite to obtain a ferrite-containing precursor;
It includes a glass removing step of removing a glass component from the ferrite-containing precursor .

In the method for producing hexagonal ferrite magnetic powder , the forming step includes adding water to the magnetic material.

In the method for producing hexagonal ferrite magnetic powder , the ferrite raw material is iron oxide powder and barium compound powder, and the glass raw material powder is boric acid powder and barium compound powder.

Further, in the method for producing hexagonal ferrite magnetic powder according to the present invention , the compact includes a total content of ferrite raw material, glass raw material, and additive substance of 98% by mass or more , and the diameter or maximum length of the compact is It is characterized by being 1 mm or more.

  By using the molded body according to the present invention for the production of hexagonal ferrite magnetic powder, even with an existing composition, magnetic powder with stable quality (magnetic properties) can be obtained and supplied to the market.

  Hereinafter, the method for producing the hexagonal ferrite magnetic powder of the present invention will be described. However, the following embodiment is an embodiment of the present invention and is not limited to the following embodiment. The following embodiments can be modified without departing from the spirit of the present invention.

  In the present invention, the “aggregated state” means a state in which the surfaces of the particles are joined to form an aggregate of two or more particles, or the surfaces of the particles are simply brought close to each other without contact. A state in which two or more particles are aggregated.

  In the following embodiments, the measurement means used in each example is as follows.

  The elemental composition in the precursor (amorphous) was measured by an ICP emission analysis method using ICP (Inductively Coupled Plasma: product name: 720-ES) manufactured by Agilent Technologies.

  The BET specific surface area was determined by the BET method using 4 Sorb US manufactured by Yuasa Ionics Co., Ltd.

  The particle size of the molded body was measured using calipers, and the average value of 50 average particle sizes was used.

  The average value obtained by measuring three samples (n = 3) under the same conditions using a heat-drying moisture meter MX-50 manufactured by A & D Co., Ltd. was used as the moisture value of the molded body.

  The manufacturing method of the hexagonal ferrite magnetic powder and the manufacturing method of the molded body of the raw material for the hexagonal ferrite magnetic powder according to the present invention will be described in the case of barium ferrite.

  First, a raw material to be a magnetic material is weighed. The raw material includes a ferrite raw material to be a magnetic powder, a glass raw material necessary for forming an amorphous body, and an additive material added to the magnetic powder. The additive substance is not included in the final magnetic powder, but includes an additive added to affect precipitation of ferrite particles in the glass.

Specifically, as a ferrite raw material, elements that constitute ferrite such as Fe ₂ O ₃ (iron oxide, HRT made by Tetgen), BaCO ₃ (barium carbonate, made by Nippon Solvay / industrial use) and the like are preferably used. Ferrite raw material powders that are each in powder form are desirable. The powdery average particle size may be about 1 to 1000 μm. These raw materials can be used as a single or a mixture of plural kinds.

  As the glass raw material, boric acid (manufactured by US Borax / ordinary product), barium carbonate and the like are preferably used. The glass raw material is used for crystallizing and precipitating ferrite melted in the melting step described later in glass. The glass raw material is preferably a powdery glass raw material powder.

  The average particle size of the powdery glass raw material may be about 1 to 1000 μm. After the ferrite particles are deposited, they become unnecessary and are removed. Therefore, a material that can be melted in an acid solution or the like in which ferrite particles do not melt is preferable. As will be shown later, the ratio of boron in the glass greatly affects the magnetic properties of the precipitated ferrite.

Additives include Bi ₂ O ₃ (bismuth oxide, manufactured by Sakai Shogyo / Industrial), Nb ₂ O ₅ (Niobium oxide, manufactured by Mitsui Mining & Mining / Industrial), CoO (Cobalt oxide, manufactured by Wako Pure Chemicals / Reagent) ZnO (Zinc oxide, manufactured by Hakusui Tech / Industrial), Nd ₂ O ₃ (Neodymium oxide, manufactured by Shin-Etsu Chemical / Industrial), and the like. These substances are contained in a molar ratio of several percent or less.

  The ferrite raw material powder, the glass raw material powder, and the additive substance are weighed to a predetermined amount. This can be called a weighing process.

  Next, these raw materials are mixed with a mixer. A mixed raw material powder is obtained by this process. In the mixed raw material powder, the mixing step is desirably performed so that the raw material powders are mixed in a powder form, and any of the raw material powders is not unevenly distributed.

  It is desirable that the mixing step be performed in air and at room temperature. In the mixing step, a commercially available blender or mixer can be suitably used as the mixer.

  In order to stabilize the composition ratio of the precursor, it is necessary to reduce the moisture in the raw material and the carbonic acid in the barium carbonate, and to keep the composition ratio of the mixed raw material powder charged into the melting furnace constant during the charging. It was considered important. In order to keep the composition ratio of the mixed raw material powder charged into the melting furnace constant during charging, the mixed raw material powder mixed well is formed into pellets and the like, and the molded body is charged into the melting furnace. It came to the conclusion that it is good to do.

  If the raw material powder is in a mixed state, it is in a powder state and does not have a certain shape. When put into a melting furnace in a powder state, the raw powder flies by the hot air that blows up, and a material with a low specific gravity cannot be added to the melting furnace, resulting in a composition ratio deviation. Therefore, the raw material powders are aggregated to form a molded body. This is called a molding process. It can be said that the molded body is a mixture of mixed raw material powders. The amount here can be freely set according to the size and density of the molded body. That is, it is possible to set optimum conditions that minimize the composition ratio deviation in accordance with the material components and the specifications of the apparatus.

  A binder or water may be added as a bonding agent to the bonding between the raw material powders in the aggregation state. In addition, the raw material powder may be compacted without using a bonding agent, and bonded with pressure to form a molded body. Desirably, the raw material powder is bonded and molded using a bonding agent. This is because the molding cost is low and the size and shape can be easily set. As an apparatus for forming a molded body, a pelletizer, a press molding machine, or the like can be suitably used.

  Specifically, granulation with a pan pelletizer is exemplified. The pan pelletizer is an apparatus that can granulate a spherical shaped body by putting a mixed raw material into a container that is inclined and rotated, and spraying the liquid onto the container. In particular, it is a granulation method that does not require pressure.

  The forming process is performed by putting the mixed raw material powder in a pan pelletizer and rolling it on the pan while adding the liquid. By adding powder and liquid in appropriate amounts, the powder is shaped into granules and granulated, and the conditions such as the angle are adjusted so as to overflow from the pan pelletizer when it reaches the desired diameter. Here, it has the function of joining each raw material powder.

  The liquid used in the present invention is water. The purpose of this is to granulate with water, so that part of boric acid dissolves in water and blends with other raw materials. In addition, as described above, boric acid water and barium carbonate react to generate carbon dioxide gas. Moreover, since it is not press processing, it can dry well to the inside. This is called a drying process.

  The water is preferably pure water and may be mixed with a chemical that promotes bonding. Further, the molding temperature is set to be equal to or lower than the melting point of each raw material so as not to be fused. This is because the composition ratio is unevenly distributed in the molded body.

  The granulated body which is a molded body is spherical and preferably has an outer diameter of φ1 mm or more and φ50 mm or less. The size is set according to the apparatus and the amount of melting in the next melting step. In the case of a size of φ1 mm or less, there is a possibility that the variation of the composition ratio is warped and increased depending on the mixing state of each raw material. On the other hand, if the molded body is larger than φ50 mm, it takes time to dry to the center and handling becomes difficult. In addition, when it is not spherical, the maximum length should just be 1 mm or more in the outer dimension of a molded object.

  The molded body having a predetermined size is dried at a temperature of 200 ° C. or higher (drying step). By drying, not only the added water but also the decomposition and dehydration of boric acid itself can be promoted, and the generation of steam during melting can be suppressed. The moisture contained in the dried molded body after drying is preferably 2% by mass or less, that is, a molded body in which the total content of ferrite raw materials, glass raw materials, and additive substances is 98% by mass or more. If it is 2% by mass or more, it may be affected by the generation of steam when it is put into the melting furnace in the next melting step. The drying time is not particularly limited as long as the water content is 2% by mass or less, but is preferably 200 ° C. or more and 14 hours or more.

  Removing the water (including crystallization water) in the raw material before putting it into the melting furnace by passing through a drying step of drying at a temperature of 200 ° C. or higher after being processed into a molded body while applying water to the raw material. Can do. Furthermore, boric acid, which is a glass raw material, partially dissolves in water, and the boric acid water and barium carbonate cause a neutralization reaction to generate carbon dioxide during the molding process. Can be removed.

  Therefore, when it is put into the melting furnace, the generation of bubbles due to water vapor or carbon dioxide gas is suppressed, and volatilization of boron is suppressed. As a result, the boron content is stable, and even when hexagonal ferrite magnetic powder having the same composition is manufactured, deviations in composition and characteristics due to so-called lot differences can be suppressed.

  The dry molded body thus obtained is melted in a melting furnace. This is called a melting step. The melting step is a step of melting the magnetic material. As the melting furnace, any type of melting furnace such as a resistance heating method or a high frequency induction heating method can be used. There is a crucible made of platinum in the melting furnace, and it is heated and maintained at a temperature of 1000 ° C. to 1400 ° C. The dried compact is added to the heated furnace. As a method of addition, the prepared dry molded article may be added at once, or may be added in divided portions depending on the melting state.

  It is desirable to add from the top of the furnace by installing a feeding pipe. Since the raw material is molded, the addition can be easily performed without worrying about powder falling. Further, since the raw material is added into the high-temperature furnace, the temperature of the raw material rises rapidly, but the foaming due to evaporation, volatilization, decomposition, etc. is melted very little. After the dry molded body is added to the furnace, it is melted and reduced in volume when held for a certain time. Therefore, the dry molded body is additionally added again according to the melt level.

  The mixed material that has become a melt is rapidly cooled. This is called a cooling process. Although the method used in the case of rapid cooling is not specifically limited, It is preferable to select the atomizing method. As the normal atomization method, a water atomization method or a gas atomization method is selected, but a method such as a centrifugal force atomization method may be used. In the atomizing method, molten molten metal is sprayed into the air while chipping with an atomizing nozzle, and cooled by forming a lump of several to several tens of microns. Thus, the precursor (amorphous body) formed by cooling is obtained.

  For the treatment after the precursor, the same treatment as that of a conventionally reported method (for example, see JP 2012-238722 A) is performed to obtain barium ferrite magnetic powder.

  By heat-treating the precursor thus obtained, a ferrite-containing precursor in which ferrite is precipitated in the precursor is obtained. This is called “a step of obtaining a ferrite-containing precursor”. In the heat treatment at this time, the precursor may be left standing or may be heat-treated while being rolled.

  The temperature of the heat treatment only needs to be such that ferrite can be formed in the precursor. Specifically, it is 450 ° C. or higher and 750 ° C. or lower, preferably 500 ° C. or higher and 750 ° C. or lower, more preferably 550 ° C. or higher and 700 ° C. or lower. It is. The heat treatment may be performed at a single temperature, that is, heating in a single stage, or may be a so-called multi-stage process performed in several stages at different processing temperatures. The heat treatment time is 30 minutes or longer, preferably 1 hour or longer.

  Next, the glass component is removed from the obtained ferrite-containing precursor to obtain ferrite particles. This is called a glass removal step. At this time, dilute acetic acid diluted to about 10% by mass is preferably used, and the treatment temperature is preferably 50 ° C. or higher. Acetic acid may be boiled or stirred for uniform removal. The pH of acetic acid as the treatment liquid at this time is preferably made acidic at 4.0 or less.

  The ferrite particles are recovered from the slurry in which the glass component is dissolved and the ferrite particles are dispersed using a solid-liquid separator.

  From the ferrite particles obtained by solid-liquid separation, acetic acid and the like adhering to the surface is removed by washing. The adhering component may be removed by washing with pure water or boiling pure water. Further, it is also preferable to perform washing while neutralizing acetic acid adhering during washing with aqueous ammonia, aqueous sodium hydroxide, aqueous potassium hydroxide, or the like. This may be called a cleaning process.

  If it is sodium hydroxide aqueous solution, it is good to set it as 0.01-1.5 mol / L, Preferably it is 0.05-1.2 mol / L, More preferably, it is 0.1-1.0 mol / L. If the concentration is low, there is no cleaning effect, and if the concentration is high, the cleaning effect is saturated and the risk of contamination is increased.

  Thereafter, the cleaning liquid is pure water, and the filtrate is sufficiently washed until the filtrate has a conductivity of 1 mS / m or less, preferably 0.8 mS / m or less.

  The obtained aggregate after the washing treatment can be obtained as a dry powder by subjecting it to a moisture removal treatment under conditions of 100 ° C. or higher in the atmosphere. Then, in order to improve the dispersibility with respect to a binder, you may make a water | moisture content adhere to the dry magnetic powder surface about 0.5-5.0 mass% in the wet environment of about 80% RH.

  Through the above steps, a high-characteristic hexagonal ferrite magnetic powder with little compositional deviation can be obtained. The hexagonal ferrite magnetic powder produced by this production method could have a very small fluctuation of the coercive force Hc, which is a magnetic property, of about 1%. As a result, high-quality magnetic materials can be stably supplied with high quality.

  Examples using the production method of the present invention will be described below.

<Example>
As raw materials, iron oxide (Tetsugen HRT, powder) 35.5 kg, barium carbonate (Nihon Solvay / industrial, powder) 59.7 kg, boric acid (US Borax, powder) 32.5 kg, bismuth oxide (Manufactured by Sakai Shogyo / Industrial) 2.1 kg, Niobium oxide (Mitsui Mining & Mining / Industrial) 0.9 kg, Cobalt oxide (Wako Pure Chemicals / Reagent) 0.2 kg, Zinc oxide (Haksuitec / Industrial) ) 0.6 kg was weighed and mixed with a Mitsui Miike FM mixer to obtain a raw material mixed powder.

  The raw material mixed powder was put into a pan pelletizer and tumbled while spraying water. At this time, the raw material mixed powder is rolled by a pan pelletizer and is repeatedly agglomerated so that the raw material powders are joined to each other while being rolled. The agglomerated state is formed by such agglomeration, and the shape is gradually spheroidized. The molded body that became spherical had an average particle diameter of about φ20 mm, and a molded body having a particle diameter of φ1 to 40 mm was distributed.

  Next, the molded body was dried at 270 ° C. for 14 hours. The moisture content of the molded body after drying was 0.6 wt%. The compact was put into a 1200 ° C. melting furnace using a feeding pipe. The molded body did not fly by the rising airflow from the furnace, and there was little foaming when the molded body melted.

  When the compact was put in a platinum crucible and melted to reduce the bulk, an additional operation of adding the compact was repeated to melt 70 kg of the compact. Thereafter, the temperature was raised to 1400 ° C., and the mixture was completely melted and held with stirring for 60 minutes, whereby the mixture was completely dissolved to form a molten metal.

  The obtained molten metal was discharged from the nozzle and rapidly cooled by a gas atomization method to form an amorphous glass body (precursor). Thereafter, the precursor was heat-treated at 620 ° C. for 1 hour to obtain a ferrite-containing precursor. The ferrite-containing precursor was immersed in 10% by mass acetic acid heated to 60 ° C. and held for 60 minutes to remove the glass component. Thereafter, acetic acid adhering to the surface was removed using pure water to obtain hexagonal ferrite magnetic powder.

  The operation until the hexagonal ferrite magnetic powder was obtained from this raw material weighing was repeated four times. That is, 4 batches were performed using the same raw material. These were designated as Example Sample 1 to Example Sample 4, respectively. The precursor was subjected to composition analysis to evaluate the composition difference between batches. The obtained hexagonal ferrite magnetic powder was evaluated for shape and magnetic properties.

  The following results were obtained for the composition of the precursor. The results are shown in Table 1. The average composition of iron was 23.1% by mass, the standard deviation (σ) was 0.191, and the coefficient of variation (σ / average composition) was 0.84%. Moreover, the average composition in boron was 5.34% by mass, the standard deviation (σ) was 0.045, and the coefficient of variation (σ / average composition) was 0.86%. The average composition of barium was 37.9% by mass, the standard deviation (σ) was 0.332, and the coefficient of variation (σ / average composition) was 0.89%.

<Powder magnetic property evaluation>
Hexagonal ferrite magnetic powder is packed in a φ6 mm plastic container and using a VSM device (VSM-P7-15) manufactured by Toei Kogyo Co., Ltd. with an external magnetic field of 795.8 kA / m (10 kOe) and a coercive force Hc. (KA / m) and saturation magnetization σs (Am ² / kg) were measured.

The magnetic properties were as follows. The results are shown in Table 3. Example Coercive force Hc (kA / m) of each sample is 205, 207, 206, 202, average value (AVE) 205, standard deviation (σ) 2.2, coefficient of variation (σ / average value). 1%. The saturation magnetization σs (Am ² / kg) is 46.2, 46.9, 46.0, 45.4, the average value (AVE) 46.1, the standard deviation (σ) 0.6, and the fluctuation The coefficient (σ / average value) was 1.3%.

  Example BET of the powder of each sample is 74.8, 72.4, 73.0, 70.5, average value (AVE) 72.7, standard deviation (σ) 1.8, coefficient of variation ( (σ / average value) was 2.4%.

<Comparative Example 1>
A hexagonal ferrite magnetic powder was prepared in the same manner as in Example 1 except that the raw materials were mixed and then put into a melting furnace without being molded. The operation from the raw material weighing to obtaining the hexagonal ferrite magnetic powder was repeated three times, and the precursor and the hexagonal ferrite magnetic powder were evaluated in the same manner. Table 2 shows the composition of each element of the precursor.

The magnetic properties were as follows. The results are shown in Table 4. Comparative Examples The coercive force Hc (kA / m) of each sample is 179, 167, 162, the average value (AVE) 169, the standard deviation (σ) 8.9, and the coefficient of variation (σ / average value) 5.2. %Met. The saturation magnetization σs (Am ² / kg) is 44.7, 43.6, 42.3, the average value (AVE) is 43.5, the standard deviation (σ) is 1.20, and the coefficient of variation (σ / The average value was 2.8%.

  Comparative Example The BET of the powder of each sample is 67.9, 73.5, 74.7, average value (AVE) 72.0, standard deviation (σ) 3.6, coefficient of variation (σ / average value) ) 5.0%.

  From this result, it can be seen that the Example has a larger amount of boron that is more volatile than the Comparative Example, and has less variation between batches. Also, the magnetic properties of the magnetic powder are less varied between batches in the examples. It can also be seen from the same BET comparison that the magnetic characteristics are improving. This suggests that an amorphous body could be produced in the composition range according to the composition design in the examples.

  The method for producing hexagonal ferrite magnetic powder of the present invention can be widely used for producing fine powder using a glass crystallization method.

Claims (4)

A step of weighing the ferrite raw material and the glass raw material and the additive substance;
A mixing step of mixing the ferrite raw material and the glass raw material and the additive substance using a mixer with a plurality of blades to obtain a mixed raw material powder;
A molding step of forming the mixed raw material powder into a molded body using a pan pelletizer ;
A drying step of drying the molded body at 200 ° C. or higher to obtain a dried molded body;
A melting step of melting the dried molded body to form a molten metal;
A cooling step of obtaining a precursor by cooling the molten metal;
Heat treating the precursor to precipitate ferrite to obtain a ferrite-containing precursor;
A method for producing a hexagonal ferrite magnetic powder comprising a glass removal step of removing a glass component from the ferrite-containing precursor. The method for producing hexagonal ferrite magnetic powder according to claim 1, wherein in the forming step, water is added to the magnetic material. The hexagonal ferrite magnetic powder according to claim 1 or 2 , wherein the ferrite raw material is iron oxide powder and barium compound powder, and the glass raw material powder is boric acid powder and barium compound powder. the method of production. The compacts, starting ferrite, glass raw materials, the total content of the additive material contains more than 98 wt%, claims 1 to 3 in diameter or maximum length of the formed features is characterized in that at 1mm or more A method for producing a hexagonal ferrite magnetic powder according to claim 1 .