KR20200090037A - Method for preparing ferrite sintered magnet - Google Patents

Abstract

A method of manufacturing a ferrite sintered magnet according to one embodiment of the present invention includes the steps of: manufacturing magnetic powder by calcining and pulverizing a mixture containing iron oxide and a metal compound; manufacturing a pellet by adding a binder resin to the magnetic powder and kneading; and manufacturing a molded body by injection molding the pellet, wherein the binder resin contains PEC (polyethylene carbonate) and the step of manufacturing the molded body includes applying a magnetic field to the pellet. Therefore, an additional surface treatment process can be omitted to save cost and time.

Description

Manufacturing method of ferrite sintered magnet {METHOD FOR PREPARING FERRITE SINTERED MAGNET}

The present invention relates to a method for manufacturing a ferrite sintered magnet and a ferrite sintered magnet. More specifically, the present invention relates to a method for manufacturing a ferrite sintered magnet including an injection molding step and a ferrite sintered magnet produced by the method.

Ferrite, a magnetic material, is divided into soft ferrite and hard ferrite.

Among them, the soft ferrite material is a material that is easily changed according to the direction and size of the magnetic field, is isotropic, and is used for TVs, communication transformers, and the like.

On the other hand, hard ferrite (Hard ferrite) is a composition of AO · nFe ₂ O ₃ (A: divalent metal ion, Sr or Ba) has a hexagonal structure magneto-plumbite (M) type crystal structure, material As the material whose magnetic properties are not easily changed according to the direction and size of the magnetic field, it is anisotropic, and is usually used as a material for permanent magnets such as motors for automobiles and rotating machines for electric appliances.

Among the magnetic materials of the magneto-plum bite type crystal structure, strontium ferrite (hereinafter referred to as "Sr ferrite") having a composition of SrFe ₁₂ O ₁₉ is typical.

Typical magnetic properties of magnetic materials include residual magnetic flux density (Br), intrinsic coercive force (Hcj), maximum magnetic energy ((BH) _max ), and squareness ratio (Hk/Hcj), among which residual magnetic flux density (Br) Is proportional to the composition's magnetic spin moment sum, saturation magnetization (M _S ), density and orientation.

In the manufacture of hard ferrite, particularly Sr ferrite, efforts have been made to change the composition of the magnetic material in order to improve the magnetic properties as described above. Representatively, attempts have been made to improve magnetic performance by substituting a part of strontium (Sr) and iron (Fe) using lanthanum (La) and cobalt (Co), and introducing lanthanum by introducing calcium (Ca) into a magnetic material. Attempts have been made to facilitate the substitution of La).

On the other hand, unlike the improvement of magnetic properties, the need for a magnet with a high degree of freedom in molding is also increasing, among which, the ceramic injection molding (CIM) method has a degree of freedom in molding in the manufacture of ferrite sintered magnets. It has an excellent advantage. However, in the ceramic injection molding method, a surfactant and a silane coupling agent have been used to increase the degree of dispersion of magnetic particles. However, in this case, an additional process called a surface treatment agent attaching process occurs, which has the disadvantage of increasing cost and time, and the residue of the surface treatment agent may remain on the sintered magnet and affect magnetic performance.

The problem to be solved by the embodiments of the present invention is to solve the problems as described above, omitting an additional surface treatment process to save cost and time, removing the residue of the ferrite sintered magnet, and the degree of orientation, etc. It is to improve magnetic properties.

A method of manufacturing a ferrite sintered magnet according to an embodiment of the present invention includes the steps of calcining and pulverizing a mixture containing iron oxide and a metal compound to prepare a magnetic powder; Preparing a pellet by adding a binder resin to the magnetic powder and kneading; And manufacturing a molded body by injection molding the pellet, wherein the binder resin includes polyethylene carbonate (PEC), and the manufacturing of the molded body includes applying a magnetic field to the pellet.

The molded body may include anisotropic hard ferrite.

The metal compound may include at least one of strontium carbonate (SrCO ₃ ) and barium carbonate (BaCO ₃ ).

The molded body may include a hard ferrite having a magneto-plumbite (M) crystal structure.

The mixture further includes at least one of cobalt oxide, lanthanum oxide (La ₂ O ₃ ), calcium carbonate (CaCO ₃ ), and silica (SiO ₂ ), and the cobalt oxide comprises at least one of CoO and Co ₃ O ₄ It can contain.

The injection molding may be ceramic injection molding (CIM).

The PEC may be added in a weight percent (wt.%) of 5 to 20 compared to the magnetic powder.

The manufacturing of the molded body may include maintaining the pellet at a temperature of 100°C to 200°C.

A heat removal step of removing the binder resin by heat-treating the molded body may be further included.

The binder removal step may include removing the PEC in the form of CO ₂ by heat treating the molded body at a temperature of 300°C to 350°C.

According to embodiments of the present invention, in the injection molding step, by adding a binder resin containing PEC (Poly Ethylene Carbonate, polyethylene carbonate), it is possible to manufacture a ferrite sintered magnet of high orientation, as well as a separate surface Since no treatment process is required, cost and time can be saved, and there is no residue left to prevent deterioration of magnetic performance.

1 is a photograph of a molded body during the manufacturing process of the Sr ferrite sintered magnet according to Comparative Example 6.
2 is a photograph of the sintered body during the manufacturing process of the Sr ferrite sintered magnet according to Comparative Example 6.

Hereinafter, various embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. The present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included instead of excluding other components unless specifically stated to the contrary.

A method of manufacturing a ferrite sintered magnet according to an embodiment of the present invention comprises the steps of: calcining and pulverizing a mixture containing iron oxide and a metal compound to prepare a magnetic powder; Preparing a pellet by adding a binder resin to the magnetic powder and kneading; And manufacturing a molded body by injection molding the pellet. The binder resin includes polyethylene carbonate (PEC), and the step of manufacturing the molded body includes applying a magnetic field to the pellet. The molded body may include anisotropic hard ferrite.

The metal compound includes at least one of strontium carbonate (SrCO ₃ ) and barium carbonate (BaCO ₃ ), and particularly preferably includes strontium carbonate (SrCO ₃ ). As a raw material, since it contains at least one of strontium carbonate (SrCO ₃ ) and barium carbonate (BaCO ₃ ), the ferrite sintered magnet of this embodiment is hard ferrite, and the composition is AO·nFe ₂ O ₃ (A : Divalent metal ion, Sr or Ba).

In addition, hard ferrite forms a magneto-plumbite (M) crystal structure of hexagonal structure, and unlike soft ferrite, anisotropic magnet, it improves magnetic performance by improving orientation of magnetic particles and improving magnetic orientation It is important to do. Polyethylene carbonate (PEC) included in the binder resin is added to improve orientation, and details will be described later.

Hereinafter, each step will be described in detail.

First, the step of preparing the magnetic powder is a step of calcining and pulverizing the mixture, and a compounding step for preparing the mixture may be performed before calcining.

The compounding step is a step of preparing a mixture for plasticization. First, the raw materials are weighed and mixed in a predetermined ratio. Attrition mill (Attrition Mill), ball mill (Ball-Mill), turbula mixer (Turbula mixer) or Spex mill, etc. for about 1 to 20 hours, mixing and grinding at the same time. As a raw material, the mixture may include iron compounds such as iron oxide and metal compounds as mentioned above, and may be in the form of a powder or a slurry in which mixed powder is dispersed in a solvent.

As an iron compound such as iron oxide, a compound such as carbonate, hydroxide or nitrate, which becomes an oxide by oxidation or firing, may be included. The iron oxide may include iron (III) oxide (Fe ₂ O ₃ ).

Further, the mixture may further include at least one of cobalt oxide, lanthanum oxide (La ₂ O ₃ ), calcium carbonate (CaCO ₃ ), and silica (SiO ₂ ). Cobalt oxide preferably contains at least one of CoO and Co ₃ O ₄ , and more preferably contains Co ₃ O ₄ .

Cobalt oxide is added to replace a part of the iron element site with a cobalt element in a ferrite sintered magnet having a magneto-plumbite (M) type crystal structure, and the saturation magnetization of the ferrite sintered magnet may be improved due to the substitution. Can. In addition to cobalt oxide, an oxide of manganese (Mn) or nickel (Ni) can be added.

On the other hand, when the part of the iron element site is replaced as described above, the balance of the ionic sintering of the ferrite sintered magnet may be broken, and thus deterioration of magnetic properties may occur in the ferrite sintered magnet. Lanthanum oxide (La ₂ O ₃ ) is a rare earth oxide added to solve this, and the lanthanum element of the added lanthanum oxide (La ₂ O ₃ ) is replaced by a part of the strontium element or barium element site of the ferrite sintered magnet to compensate for charge compensation. Through this, the problem of deterioration of the magnetic properties as described above can be solved. In addition to lanthanum oxide (La ₂ O ₃ ), oxides of neodynium (Nd) or praseodymium (Pr) can be added.

On the other hand, silica (SiO ₂ ) and calcium carbonate (CaCO ₃ ) are sintering aids, and can control the sintering phenomenon in a subsequent sintering step. Silica (SiO ₂ ) can be added to improve the coercive force of the ferrite sintered magnet by inhibiting the growth of grains, and calcium carbonate (CaCO ₃ ) is added to improve grain orientation by promoting grain growth and proceeding with grain growth. Can be. That is, it is important to mix silica (SiO ₂ ) and calcium carbonate (CaCO ₃ ) in a balanced manner in order to control the degree of grain growth.

In addition, boric acid (H ₃ BO ₃ ) can be added to the mixture to promote the ferritic reaction in plasticity and to uniformize the growth of the particles.

Subsequently, the calcination, by heating the mixture mixed through the compounding step at a temperature of 1100°C to 1300°C, accelerates the ferrite reaction of the mixture, and thus has a magneto-plumbite (M) crystal structure. It is the process of making. Normally, the calcination proceeds in an oxidizing atmosphere in the air. The calcination time at the calcination temperature is preferably 0.1 to 5 hours, more preferably 0.5 to 3 hours.

The pulverization is a step of pulverizing ferrite particles obtained through calcination to prepare pulverized powder. In the embodiment of the present invention, the pulverization step is pulverized in two stages: a coarse pulverizing step and a fine pulverizing step. Further, in other embodiments, the grinding step may be performed in one step.

Since the ferrite particles are usually granular or bulky, it is preferable to first perform a coarse crushing process. In the coarse pulverizing step, pulverization is performed by dry using a dry vibrating mill, a dry ball mill, or the like to obtain a coarsely pulverized powder.

In the fine grinding step, the coarsely pulverized powder obtained by the coarse grinding step is wet-pulverized using a wet attritor, a ball mill, a jet mill or the like to obtain a fine grinding powder. The pulverization time is, for example, preferably 30 minutes to 10 hours when using a wet attritor, and preferably 5 to 50 hours when using a ball mill. It is preferable to adjust these times suitably according to each grinding method.

In the coarse or fine grinding process, at least one of silica (SiO ₂ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ) and barium carbonate (BaCO ₃ ) is added as an additive to improve sinterability and magnetic properties. Can. In addition, in order to promote the substitution effect during sintering and control the growth of magnetic particles, lanthanum oxide (La ₂ O ₃ ), zinc oxide (ZnO), cobalt oxide (CoO, Co ₃ O ₄ ), etc. Can be added.

A magnetic powder may be prepared through the above-described process, followed by adding a binder resin to the magnetic powder and kneading to prepare pellets, followed by injection molding the pellets under a magnetic field to prepare a molded body.

Specifically, the magnetic powder after drying is kneaded with a binder resin, waxes, lubricants, plasticizers, sublimable compounds, and the like to prepare pellets using a pelletizer or the like. Kneading is performed, for example, with a kneader or the like. As the pelletizer, for example, a twin-screw single-screw extruder is used.

Thereafter, the pellet is injection molded in a mold using an injection molding apparatus. The injection molding apparatus may be a molding apparatus using ceramic injection molding (CIM). The pellet is heated and melted in an extruder at a temperature of 100°C to 200°C, and then injected into a mold. The temperature of the mold may be 20°C to 80°C. The molding pressure may be 0.1 ton/cm 2 to 0.5 ton/cm 2.

At this time, a magnetic field of 5 to 15 kOe may be applied to the mold. Since the ferrite sintered magnet of this embodiment is hard ferrite, the orientation of particles is important because it is anisotropic, unlike soft ferrite. Therefore, by applying the magnetic field as described above to the pellets in the step of manufacturing the molded body, the orientation of the magnetic particles is achieved.

The binder resin includes polyethylene carbonate (PEC). Conventionally, surfactants and silane coupling agents have been used to increase the dispersion degree of particles. However, in this case, an additional process called a surface treatment agent attachment process has a disadvantage in that cost and time are increased, and a residue of the surface treatment agent remains in the sintered magnet and may affect magnetic performance. On the other hand, the manufacturing method of the ferrite sintered magnet according to an embodiment of the present invention can reduce the manufacturing cost and time by omitting the existing surface treatment process by introducing PEC into the binder resin.

In addition, due to the polarity characteristics of the added PEC, PEC has a high affinity with the magnetic powder and inhibits the formation of hydrogen bonds between the magnetic powder. At the same time, due to the steric hindrance effect of PEC, it is difficult to access magnetic powders to each other, thereby reducing the cohesion of magnetic powders. In conclusion, the added PEC can improve the dispersibility of the magnetic powder.

Since magnetic powders having excellent dispersibility can be uniformly moved in response to a magnetic field in a subsequent molding process, a molded body having a high degree of orientation can be obtained.

As described above, unlike isotropic soft ferrite, in anisotropic hard ferrite, it is important to improve magnetic performance by improving the orientation of magnetic particles, and PEC added to the binder resin is used for magnetic particles. The degree of orientation can be improved, which can lead to an improvement in magnetic performance, especially residual magnetic flux density (Br). Moreover, it is a great advantage that this effect can be achieved only by adding PEC without a conventional surface treatment process.

In addition, PEC may be added in a weight percent (wt.%) of 5 to 20 compared to the magnetic powder. When PEC is added in an amount of less than 5 wt.%, the dispersion effect of the magnetic powder is lowered and agglomerated powders are formed, resulting in insufficient orientation, and thus there is a problem that the magnetic performance of the ferrite sintered magnet cannot be improved. When the PEC is added in excess of 20 wt.%, a large number of pores may be generated in the binder removal process described below due to the PEC more than necessary, and thus cracks may be formed in the molded body and the sintered body.

In the case of the step of manufacturing a molded body by injection molding the pellet under a magnetic field, it is important to control the temperature for controlling the viscosity of the binder resin in order to improve the orientation of the magnetic powders.

When the viscosity of the binder resin is high, the flowability of the magnetic powders is poor, and it is difficult to exhibit excellent orientation even under a magnetic field. The polyolefin-based binder resin containing PEC tends to have a lower viscosity as temperature increases. Specifically, during injection molding, the temperature of the pellets inside the injection molding machine is preferably 100°C to 200°C, as mentioned above. When the temperature is less than 100°C, the viscosity of the binder resin is not sufficiently low, and thus the fluidity of the magnetic powder is lowered under the magnetic field, and thus it is difficult to sufficiently improve the degree of orientation. When the temperature exceeds 200°C, the polyolefin-based binder resin containing PEC begins to decompose, so that molding is not completely performed during injection and cracks may occur in the molded body.

Thereafter, a debinder step of removing the binder resin by heat-treating the molded body may be continued.

Specifically, the molded body may be heated to a temperature of 300°C to 350°C to completely remove the added PEC in CO ₂ form. PEC decomposes at 220°C and completely changes to CO ₂ at 280°C. Unlike the case of using a conventional surfactant and a silane coupling agent, there is no fear of impairing magnetic performance because no residue remains.

Thereafter, a sintering step of sintering the molded body may be followed.

In performing the sintering step, in the sintering process, the magnetic properties of the ferrite sintered magnet can be enhanced by controlling the sintering conditions such as the heating rate, the maximum temperature, the maximum temperature holding time and the cooling rate. Specifically, the heating rate is preferably 1°C/min to 10°C/min, and the sintering maximum temperature and the maximum temperature holding time are preferably sintered at 1,150°C to 1,250°C for 30 minutes to 2 hours, and cooling time 1 It is preferable to cool to ℃/min to 10°C/min.

Next, a method of manufacturing a ferrite sintered magnet according to the present invention will be described through specific examples and comparative examples.

Example 1

A slurry was prepared by mixing 87 wt% of iron(III) oxide (Fe ₂ O ₃ ) and 13 wt% of strontium carbonate (SrCO ₃ ) with water while grinding for 2 hours using a ball mill. To the slurry, 0.1 wt% of silica (SiO ₂ ) and 0.1 wt% of boric acid (H ₃ BO ₃ ) relative to the input powder are added to prepare a mixture.

Thereafter, the mixture was heated to a temperature of 1250° C. for 1 hour to accelerate the ferrite reaction to prepare a plasticizer.

The plasticizer was obtained by using a dry vibrating mill to obtain a coarsely pulverized powder having an average particle diameter of 4 μm. A coarsely pulverized powder was added to a wet attritor to prepare magnetic powder having an average particle diameter of 0.65 μm.

After the magnetic powder was dried at 100° C. for 10 hours, it was kneaded with a polyolefin-based binder resin containing PEC using a kneader and molded into pellets using a pelletizer. Kneading was performed under conditions of 150°C and 2 hours. PEC was added at 10 wt.% compared to the magnetic powder.

Next, the pellet is injection molded in a mold using an injection molding apparatus using ceramic injection molding. The pellet is heated and melted at a temperature of 160° C. inside the extruder and injected into a mold. The molding pressure was 0.3 ton/cm 2 and the applied magnetic field was set to 10 kOe.

The molded body obtained by injection molding was heated at a temperature of 300°C for 5 hours to perform a binder removal process, and after sintering at 1210°C for 1 hour, a Sr ferrite sintered magnet was obtained using a processing machine.

Example 2

Sr ferrite sintered magnets were prepared in the same manner as in Example 1, except that PEC was added at 5 wt.% compared to the magnetic powder, in the same manner as in Example 1.

Example 3

Sr ferrite sintered magnets were prepared in the same manner as in Example 1, except that PEC was added at 20 wt.% relative to the magnetic powder, in the same manner as in Example 1.

Comparative Example 1

The same raw material as in Example 1 was subjected to the same calcination and grinding as in Example 1 to prepare a magnetic powder.

Thereafter, a silane coupling agent was attached to the magnetic powder by adding 0.3 to 3.0 wt.% of the silane coupling agent to the magnetic powder as a surface treatment agent, and 10 wt.% of the polyolefin-based binder resin compared to the magnetic powder was added to the magnetic powder. Add.

Then, pellets were prepared in the same manner as in Example 1, and injection molding was performed, followed by sintering to obtain a Sr ferrite sintered magnet.

Comparative Example 2

The same raw material as Comparative Example 1 was prepared in the same manner as in Comparative Example 1, except that 10 wt.% of polyethylene compared to the magnetic powder was used as the binder resin, thereby obtaining a Sr ferrite sintered magnet.

Comparative Example 3

Sorbitol was added as a surface treatment agent, and the same raw material as in Comparative Example 1 was prepared in the same manner as in Comparative Example 1, except that 7.5 wt.% of polyacetal compared to the magnetic powder was used as the binder resin. A ferrite sintered magnet was obtained.

Comparative Example 4

The same raw material as in Comparative Example 1 was prepared in the same manner as in Comparative Example 1, except that Mannitol was added as a surface treatment agent and 7.5 wt.% of polyacetal compared to the magnetic powder was used as the binder resin. Sr ferrite sintered magnets were obtained.

Comparative Example 5

The same raw material as in Example 1 was prepared in the same manner as in Example 1, except that PEC was added at 3 wt.% relative to the magnetic powder, thereby preparing a Sr ferrite sintered magnet.

Comparative Example 6

Sr ferrite sintered magnets were prepared in the same manner as in Example 1, except that PEC was added at 25 wt.% relative to the magnetic powder, in the same manner as in Example 1.

Evaluation Example 1: Measurement of magnetic properties

Residual magnetic flux density (Br), coercive force (Hcj), angular ratio (Hk/Hcj) and orientation were measured using a BH tracer to evaluate the magnetic properties of the Sr ferrite sintered magnets of Examples 1 and 4, , Shown in Table 1. Orientation was calculated through the following equation. However, the orientation degree of Example 2, Example 3, Comparative Example 5 and Comparative Example 6 was not measured.

Orientation = Br (easy axis) / {Br (easy axis) + Br (hard axis)}

Residual magnetic flux density Br (mT) Coercivity Hcj (Oe) Square ratio Hk/Hcj (%) Orientation Example 1 480.7 3340 94.9 0.55 Example 2 465.1 3350 94.2 - Example 3 473.0 3410 95.1 - Comparative Example 1 472.1 3320 94.1 0.45 Comparative Example 2 464.9 3610 93.8 0.46 Comparative Example 3 451.0 3890 93.1 0.42 Comparative Example 4 440.2 4250 92.8 0.41 Comparative Example 5 461.5 3420 94.3 - Comparative Example 6 471.2 3490 93.8 -

It can be seen that the residual magnetic flux density (Br) of the Sr ferrite sintered magnet of Example 1 shows a higher value than the residual magnetic flux density (Br) of the Sr ferrite sintered magnets of Comparative Examples 1 to 4. This is a result shown by adding a binder resin containing PEC, so that the dispersibility of the magnetic powder is increased and the orientation of the particles is increased. This can be confirmed through the fact that the orientation degree of the Sr ferrite sintered magnet of Example 1 has a higher value than the orientation degree of the Sr ferrite source magnets of Comparative Examples 1 to 4. In addition, when PEC is used as a binder, no residue remains after binder removal, which results in a higher residual magnetic flux density than when a silane coupling agent is used as a surfactant.

On the other hand, when comparing the Sr ferrite sintered magnets of Examples 1 to 3 with the Sr ferrite sintered magnets of Comparative Examples 5 and 6, it was confirmed that the residual magnetic flux density (Br) of the Sr ferrite sintered magnets of Comparative Examples 5 and 6 was lowered. have. The Sr ferrite of Comparative Example 5 is a result of the insufficient amount of PEC and the dispersion effect of the magnetic powder is poor, and the Sr ferrite of Comparative Example 6 has a large number of pores in the debinder process due to the addition of PEC more than necessary. This is because the cracks may occur in the molded body or sintered body.

Evaluation Example 2: Picture of molded body and sintered body

1 is a picture of the molded body during the manufacturing process of the Sr ferrite sintered magnet according to Comparative Example 6, Figure 2 is a picture of the sintered body during the manufacturing process of the Sr ferrite sintered magnet according to Comparative Example 6. As mentioned above, in the Sr ferrite of Comparative Example 6, since more PEC was added than necessary, a large number of pores are generated in the debinder process, and cracks may occur in the molded body or the sintered body, and this can be confirmed through FIGS. 1 and 2.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (10)

Preparing a magnetic powder by calcining and pulverizing a mixture containing iron oxide and a metal compound;
Preparing a pellet by adding a binder resin to the magnetic powder and kneading; And
Including the step of manufacturing a molded body by injection molding the pellets,
The binder resin includes polyethylene carbonate (PEC),
The manufacturing method of the molded body includes the step of applying a magnetic field to the pellet. In claim 1,
The molded body is a method of manufacturing a ferrite sintered magnet containing an anisotropic hard ferrite. In claim 1,
The metal compound is a method of manufacturing a ferrite sintered magnet comprising at least one of strontium carbonate (SrCO ₃ ) and barium carbonate (BaCO ₃ ). In claim 1,
The molded body is a magneto-plumbite (Magneto-plumbite, M) method of manufacturing a ferrite sintered magnet comprising a hard ferrite of a crystal structure. In claim 1,
The mixture further comprises at least one of cobalt oxide, lanthanum oxide (La ₂ O ₃ ), calcium carbonate (CaCO ₃ ) and silica (SiO ₂ ),
The cobalt oxide is a method of manufacturing a ferrite sintered magnet comprising at least one of CoO and Co ₃ O ₄ . In claim 1,
The injection molding is a method of manufacturing a ferrite sintered magnet, which is ceramic injection molding (CIM). In claim 1,
The PEC is a method of manufacturing a ferrite sintered magnet is added in weight percent (wt.%) of 5 to 20 compared to the magnetic powder. In claim 1,
The manufacturing method of the molded body includes the step of maintaining the pellet at a temperature of 100°C to 200°C. In claim 1,
A method of manufacturing a ferrite sintered magnet further comprising a binder removal step of heat-treating the molded body to remove the binder resin. In claim 9,
The binder removal step is a method of manufacturing a ferrite sintered magnet comprising the step of heat-treating the molded body at a temperature of 300 ℃ to 350 ℃, removing the PEC in the form of CO ₂ .

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