JP2006273612A - Method of firing mn-zn-based ferrite core, production method of mn-zn-based ferrite core, and sintering furnace system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method of an Mn-Zn-based ferrite core which can suppress deformation caused by firing of the core which is small in size and has a leg part. <P>SOLUTION: The production method includes: a heating process of heating an Mn-Zn-based ferrite molding having a prescribed core shape up to a prescribed temperature; a holding process succeeding thereto; and a cooling process succeeding thereto. In the heating process, the molding is heated at the heating rate determined on the basis of the oxygen partial pressure (PO<SB>2</SB>) in a firing atmosphere. The heating rate is preferably determined based on the PO<SB>2</SB>in the firing atmosphere and an amount of deformation of the core previously determined relating to the PO<SB>2</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a Mn—Zn ferrite core suitably used for electronic parts such as a transformer, a reactor, and a choke coil, and more particularly to prevention of deformation of the core during sintering.

  As a material used for transformers and reactors, Mn—Zn ferrite is known. Mn—Zn-based ferrite has a higher saturation magnetic flux density than Ni-based ferrite. For this reason, Mn—Zn ferrite is generally used for transformers and choke coils for large currents.

Mn—Zn-based ferrite is usually manufactured through the following steps. Plural kinds of oxide raw material powders are mixed, and the obtained mixed powder is calcined in the air at 800 to 1100 ° C. After pulverizing the obtained calcined powder, a binder is mixed and granulated into granules using, for example, a spray dryer. After this granulated powder is formed into a predetermined shape, it is fired in an atmosphere in which the oxygen partial pressure (PO ₂ ) is controlled to obtain a sintered Mn—Zn-based ferrite.

Mn—Zn-based ferrite is used for actual applications as a core having various shapes. As the shape of this core, there is a so-called U-shaped core or E-shaped core. FIG. 7 shows the appearance of a U-shaped core and FIG. 8 shows the appearance of an E-shaped core. These cores are fired in the state shown in FIGS. In the firing process, for example, a phenomenon is observed in which the leg portion X on which the U-shaped core is suspended is deformed in the direction of the white arrow in FIGS. This phenomenon occurs based on the fact that the sintering density does not increase if PO ₂ is high in the temperature range exceeding about 1100 ° C. in the temperature raising process of firing. In order to solve this problem, conventionally, in order to lower the PO _{2 in} the firing atmosphere in the temperature raising process and to improve the sinterability, a measure for lowering the temperature raising rate has been taken.

Patent Literature 1 and Patent Literature 2 have made the following proposals regarding the rate of temperature rise in firing Mn—Zn ferrite. That is, Patent Document 1 discloses a low loss by setting the temperature rising process from 1000 ° C. to the firing holding temperature in a 2 to 21% PO ₂ atmosphere at a temperature rising rate of 80 to 400 ° C./hr. It discloses that Mn—Zn ferrite can be supplied stably. Patent Document 2 discloses that the temperature raising process from the binder removal end temperature to the holding start temperature is raised at a temperature rising rate of 250 to 400 ° C./hr at an oxygen partial pressure of 1200% or higher and 5% or lower. Thus, it is disclosed that a Mn—Zn ferrite for power supply having high fracture toughness and improved mechanical strength can be obtained.

Japanese Patent Laid-Open No. 10-22113 JP 2000-138117 A

As described above, the deformation of the core at the time of firing was performed by lowering the PO ₂ in the firing atmosphere and slowing the heating rate, but when manufacturing a small U-shaped core or E-shaped core. However, this measure has been insufficient for realizing a uniform atmosphere because of the complicated packaging of fired products. The Mn—Zn-based ferrite spouts about 0.3 wt% of O ₂ (oxygen) in the process of raising the temperature with the spinelization of Mn ₂ O ₃ and Fe ₂ O ₃ . To suppress an increase in PO _2, and control the supplying N ₂ (nitrogen) amounts to the sintering atmosphere, in the entire firing atmosphere, it is difficult to achieve the desired PO _2. In particular, in the case of a core having a shape such as a U-type core or an E-type core, the exhaled oxygen stagnates in the surroundings, and it is difficult to sufficiently replace the atmosphere with nitrogen. Therefore, the oxygen partial pressure varies within the firing atmosphere. As a result, it is not easy to fire a core having a leg portion such as a small E-shaped core or U-shaped core without deformation on an industrial production scale. Patent Document 1 and Patent Document 2 described above do not consider deformation of the core due to firing.

  The present invention has been made based on such a technical problem, and provides a method for manufacturing a Mn—Zn ferrite core that is small and can suppress deformation during firing of a core having legs. With the goal.

The present inventors have found that even when the firing atmosphere is the same, the amount of deformation of the legs changes depending on the rate of temperature rise. Furthermore, even if PO ₂ is the same, the amount of deformation of the leg portion can be reduced as the heating rate in the firing process is increased. This indicates that the amount of deformation of the legs can be suppressed by adopting a temperature rising rate that takes into account the increase in PO ₂ assumed in the firing furnace. That is, the present invention includes a temperature raising process for raising the temperature of a Mn—Zn ferrite molded body having a predetermined core shape to a predetermined temperature, a holding process following the temperature raising process, and a temperature lowering process following the holding process. In the temperature raising process, the above problem is solved by a method for firing a Mn—Zn ferrite core that is heated at a rate of temperature rise determined based on the oxygen partial pressure (PO ₂ ) in the firing atmosphere.

In the present invention, the rate of temperature rise can be determined based on PO ₂ in the firing atmosphere and the deformation amount of the core shape obtained in advance for the PO ₂ . Here, the deformation amount of the core after firing can be suppressed by determining the temperature increase rate at which the deformation amount of the core shape obtained in advance is minimized. Moreover, it is preferable that the temperature increase rate at which the deformation amount of the core shape is minimized is determined based on the deformation amount of the core shape caused by firing in a nitrogen (N ₂ ) atmosphere. In this way, it is possible to suppress to a small N ₂ atmosphere firing the same deformation amount of the deformation amount.
The temperature increase rate according to the present invention need not be performed throughout the temperature increase process. This is because there is a temperature range that does not affect the deformation. In view of this, in the present invention, it is sufficient to raise the temperature range of 1000 to 1300 ° C. at a rate of temperature determined based on PO ₂ in the firing atmosphere.

The present invention also includes a molded body manufacturing process for manufacturing a Mn—Zn-based ferrite molded body having a predetermined core shape, and a firing process for firing the molded body. The above problem can also be solved by a method for producing a Mn—Zn ferrite core, characterized in that the temperature is raised at a rate of temperature rise corresponding to a change in oxygen partial pressure (PO ₂ ).
In this manufacturing method, the rate of temperature rise can be set assuming PO ₂ in the firing atmosphere, but by detecting PO ₂ in the firing atmosphere and setting it based on the detection result, a more appropriate rise It can be fired at a temperature rate. At this time, a relationship between the deformation amount of the core shape corresponding to the predetermined PO ₂ and the temperature rising rate is obtained in advance, and the temperature rising rate is determined by comparing the relationship with the change in PO _{2 in} the firing atmosphere. Can do.

The present invention provides the following sintering furnace system for performing the above-described firing method. This sintering furnace system detects the oxygen partial pressure (PO ₂ ) in the sintering furnace body, the heating source disposed in the sintering furnace body, and the sintering furnace body. And a control unit that controls the heating temperature of the heating source based on the detected PO ₂ . In this sintering furnace system, the control of the heating source is stored by associating and storing the temperature rise rate at which the deformation amount of the body to be fired at the predetermined PO ₂ is minimized and the predetermined PO ₂ , and is detected by a sensor. It is preferable to carry out based on the relationship between PO ₂ , the stored deformation amount and the temperature rising rate.

  As described above, according to the present invention, it is possible to suppress deformation during firing of a small Mn—Zn ferrite core having legs.

Hereinafter, the present invention will be described based on embodiments.
Each raw material powder of high purity Fe ₂ O ₃ , Mn ₃ O ₄ , ZnO was weighed so as to be 54 mol% Fe ₂ O ₃ -36 mol% MnO-10 mol% ZnO, mixed by a ball mill, and then the mixed powder was 800- After calcining in the air at 1100 ° C., 80 ppm of SiO ₂ , 800 ppm of CaCO ₃ and 250 ppm of Nb ₂ O ₅ were added as auxiliary components to the calcined powder obtained and pulverized with a ball mill. Polyvinyl alcohol was added as a binder to the pulverized powder and granulated by a spray dryer. Thereafter, a core molded body of a U-shaped core and an E-shaped core was prepared so that the density difference of each part was 0.05 g / cm ³ or less.

The obtained molded body was fired under the following conditions.
Temperature rising rate: normal temperature to 1000 ° C .... 300 ° C./hr
1000-1300 ° C ... 30 ° C / hr,
100 ° C./hr,
300 ° C / hr
Firing atmosphere: normal temperature to 1000 ° C. (temperature rise) ... nitrogen (N ₂ , oxygen partial pressure (PO ₂ = 0%)),
1000-1300 ° C. (temperature increase) ... nitrogen (N ₂ , oxygen partial pressure (PO ₂ = 0%)),
Oxygen partial pressure (PO ₂ ) = 1%,
Oxygen partial pressure (PO ₂ ) = 5%,
Atmosphere (oxygen partial pressure (PO ₂ ) = 21%)
1300 ° C. (holding): partial pressure of oxygen (PO ₂ ) = 2%
Holding temperature, time: 1300 ° C, 5 hr

The deformation amount of the U-shaped core and the E-shaped core made of the obtained sintered body was measured. FIG. 1 shows the relationship between the rate of temperature rise and the amount of deformation of the leg in the U-shaped core, and FIG. 2 shows the relationship between the rate of temperature rise and the amount of deformation of the leg in the E-type core. Note that the deformation amount of the U-shaped core was obtained by L1b-L1a in FIG. Further, the deformation amount of the E-type core was obtained by L2b-L2a in FIG.
As shown in FIGS. 1 and 2, it can be seen that the amount of deformation of the core due to firing in an N ₂ atmosphere is the smallest, and the amount of deformation increases as PO ₂ increases. It can also be seen that the deformation amount of the core decreases as the rate of temperature increase increases during the temperature increase process at 1000 to 1300 ° C.

The relationship between the firing atmosphere, the heating rate and the amount of deformation of the legs is as described above. However, FIGS. 1 and 2 show the heating rate even in a firing atmosphere having, for example, about 5% PO _2. This suggests that by increasing the speed, the deformation of the leg can be suppressed to the same extent as in the case of firing in the N ₂ atmosphere.

FIG. 3 shows the relationship between the rate of temperature increase and the amount of deformation when the U-shaped cores produced based on FIG. 1 are fired in the atmosphere of N ₂ , PO ₂ = 1%, PO ₂ = 5%, respectively. It is a graph to show. This graph specifically shows that the deformation of the leg portion can be suppressed equivalent to the case of firing in the N ₂ atmosphere. That is, when firing in an atmosphere of PO ₂ = 5%, a diagram showing the relationship between the rate of temperature rise and the amount of deformation when firing in an N ₂ atmosphere (temperature rise rate-deformation amount diagram), and PO ₂ = By making the temperature rise rate corresponding to the intersection of the temperature rise rate-deformation amount diagram when fired in a 5% atmosphere, the deformation amount should be equal to the deformation amount when fired in an N ₂ atmosphere. Can do. The same applies to PO ₂ other than PO ₂ = 5%.

As described above, the present invention proposes that the temperature is increased at a temperature increase rate determined based on PO ₂ in the firing atmosphere, and in particular, PO ₂ in the firing atmosphere and the PO ₂ are obtained in advance. Based on the deformation amount of the core shape, a temperature increase rate at which the deformation amount is minimized can be selected.

The present invention suppresses the deformation amount in the sintering process of, for example, the leg portion of the core based on the temperature increase rate-deformation amount diagram shown above, and includes the following several forms.
As shown in FIG. 4, a predetermined temperature range, for example, a temperature range of 1000 to 1300 ° C., can be heated at a constant temperature increase rate determined based on the intersection of the temperature increase rate-deformation amount diagram. . This form can be adopted when the amount of O ₂ discharged from the molded body in the temperature rising process can be grasped in advance. For example, when it is assumed that PO _{2 in} the firing atmosphere is 1% due to O ₂ discharged from the molded body in the temperature rising process, based on the temperature increase rate-deformation amount diagram shown in FIG. The temperature increase rate in the temperature range is set to 300 ° C./hr.

In addition, the amount of O ₂ discharged from the molded body in the process of temperature rise may vary. Therefore, the temperature rise time and the PO ₂ fluctuation of the firing atmosphere due to the discharged O ₂ can be grasped in advance, and the temperature rise speed corresponding to the fluctuating PO ₂ can be set. That is, as shown in FIG. 5, in the temperature rising process at 1000 to 1300 ° C., the temperature rising rate is changed from V1 to V2 with the passage of time, thereby applying a temperature rising rate more appropriate for deformation suppression. be able to.

In the above, based on PO ₂ in the firing atmosphere that has been grasped in advance, the rate of temperature rise in the temperature raising process of firing is determined. However, in addition to fluctuations in the amount of O ₂ discharged from the compact, PO ₂ in the firing atmosphere varies due to various factors in an industrial production environment. Therefore, the present invention includes detecting PO ₂ in the firing atmosphere and changing the temperature rising rate based on the detection result. For example, when the detected PO ₂ is 1%, the temperature increase rate-deformation amount diagram in the case of firing in the N ₂ atmosphere shown in FIG. 3 and the rise in the case of firing in the atmosphere of PO ₂ = 1%. A temperature increase rate corresponding to the intersection of the temperature rate and deformation amount diagram is adopted. Thereafter, when the detected PO ₂ changes to 5%, the temperature rise rate-deformation amount diagram in the case of firing in the N ₂ atmosphere shown in FIG. 3 and the case of firing in the atmosphere of PO ₂ = 5% A temperature increase rate corresponding to the intersection of the temperature increase rate and the deformation amount diagram is adopted. In the example of FIG. 3, the temperature increase rate is increased by about 50 ° C./hr after PO ₂ = 1% becomes PO ₂ = 5%.

One example of a sintering furnace for carrying out the above sintering method will be described with reference to FIG.
FIG. 6 is a block diagram (plan view) showing the configuration of the sintering furnace system 10 that can change the temperature rising rate based on the detected PO ₂ . As shown in FIG. 6, the sintering furnace system 10 includes a sintering furnace body 1 and a plurality of heating sources 2 disposed in the sintering furnace body 1. As the heating source 2, known means such as a flame burner and an electric heater can be appropriately used. The molded body is placed on the tray 5 in the sintering furnace body 1 and fired while moving in the direction of the arrow in FIG. In the sintering furnace system 10, a plurality of PO ₂ sensors 3 are arranged in the sintering furnace body 1, and this PO ₂ sensor detects PO ₂ in the sintering furnace body 1. The sintering furnace system 10 includes a control unit 4. This control unit 4 is a characteristic part of the sintering furnace system 10.

The control unit 4 has a function of controlling the heating temperature by the heating source 2. The control unit 4, information on PO ₂ detected by the PO ₂ sensor 3 receives the PO ₂ sensor 3. The control unit 4 is, for example PO ₂ shown in FIG. 4 - is provided with a heating rate table. This table, for example, Atsushi Nobori rate shown in FIG. 3 - is determined from the amount of deformation diagrams stores the deformation amount in association with the corresponding PO ₂ heating rate to minimize in the PO _2. The controller 4 can store a PO ₂ -temperature increase rate table as shown in Table 1 for every type of core to be fired. The control unit 4 collates information related to PO ₂ received from the PO ₂ sensor 3 with the PO ₂ -temperature increase rate table, and corresponds to PO ₂ received from the PO ₂ sensor 3, that is, the temperature increase that minimizes the deformation amount. Select speed. The control unit 4 controls the heating temperature of the heating source 2 so that the selected rate of temperature increase is realized. In order to increase the rate of temperature increase, the heating temperature of the specific heating source 2 may be controlled to be high.
As described above, the sintering furnace system 10 according to the present invention detects the PO ₂ in the sintering furnace body 1 and sets the heating rate at which the deformation amount is minimized based on the PO ₂ -heating rate table. can do.

  The present invention is effective for cores having legs, particularly long legs, such as U-shaped cores and E-shaped cores. The U-type core and the E-type core are examples, and the application target of the present invention is not limited to these two. For example, it can be widely applied to a core having a leg portion or a portion corresponding to the leg portion, such as a pot core or a cut core.

Next, the suitable manufacturing method of the Mn-Zn type ferrite core by this invention is demonstrated.
As a raw material for the main component, an oxide or a powder of a compound that becomes an oxide by heating is used. Specifically, Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, ZnO powder, or the like can be used. What is necessary is just to select suitably the average particle diameter of each raw material powder to prepare in the range of 0.1-3 micrometers.
The raw material powder of the main component is wet mixed and then calcined. The calcining temperature may be a predetermined temperature in the range of 800 to 1000 ° C., and the atmosphere may be N ₂ to air. What is necessary is just to select the stable time of calcination suitably in the range of 0.5 to 5 hours. After the calcination, the calcined body is pulverized, for example, to an average particle size of about 0.5 to 2 μm. The raw material for the main component is not limited to the raw material for the main component described above, and a composite oxide powder containing two or more metals may be used. For example, a complex oxide powder containing Fe and Mn can be obtained by oxidizing and baking an aqueous solution containing iron chloride and manganese chloride. This powder and ZnO powder may be mixed and used as a main component material. In such a case, calcining is unnecessary.

In addition to the above main components, subcomponents can be added to the Mn—Zn ferrite core of the present invention. For example, it is possible to use _{SiO 2, CaCO 3, Nb 2} O 5, ZrO 2, Ta 2 O 5, V 2 O 5, GeO 2, In 2 O 5, Ga 2 O 5, SnO 2, TiO 2 , etc. . The raw material powders of these subcomponents are mixed with the main component powder pulverized after calcining. However, after mixing with the raw material powder of the main component, it can be subjected to calcining together with the main component.

  The mixed powder composed of the main component and the subcomponent is granulated into a granule in order to smoothly execute the subsequent molding process. Granulation can be performed using, for example, a spray dryer. A small amount of a suitable binder such as polyvinyl alcohol (PVA) is added to the mixed powder, and this is sprayed and dried with a spray dryer. The particle size of the obtained granules is preferably about 80 to 200 μm.

The obtained granule is formed into a desired shape using, for example, a press having a mold having a predetermined shape, and this formed body is subjected to a firing step.
As shown in FIG. 4, the firing step includes a temperature rising process I for raising the temperature to a predetermined temperature, a holding process II for holding a predetermined temperature for a predetermined time following the temperature raising process, and a temperature lowering process performed after the holding process II. Contains III. The holding temperature in the holding process II may be referred to as a firing temperature.

In the present invention, the heating rate in the heating process is set as described above. The temperature range in which this setting is performed is a temperature range of 1000 to 1300 ° C. or higher, and whether or not to perform the above setting is arbitrary in a temperature range of less than 1000 ° C. or more than 1300 ° C. The reason is as follows.
The temperature at which Fe ₂ O ₃ and Mn ₃ O ₄ are spineled depends on the firing atmosphere. When the firing atmosphere is N ₂ , spinelization is performed at around 850 ° C. and 1000 ° C. However, when the firing atmosphere is air, the temperature of the spinel shifts to a high temperature side of about 100 ° C., and is performed at around 950 ° C. and around 1100 ° C.
With regard to the behavior of shrinkage due to sintering, the shrinkage is the most in the vicinity of 1100 ° C. in either N ₂ atmosphere or air.

The deformation due to the firing is caused by the superiority or inferiority of the sintered density, and the firing does not increase and the deformation occurs in the firing in the air. The reason why the density does not increase by firing in the air is that the spinelization temperature overlaps with the temperature at which large shrinkage occurs, so that closed pores are easily formed in the molded body (sintered body). On the other hand, in the case of firing in an N ₂ atmosphere, since spinelization is almost completed at about 1000 ° C., the temperature closes to 1100 ° C., which is the most contracted, so that closed pores are hardly generated.

According to the study by the present inventors, as described above, in the specific temperature range of the temperature raising process, the higher the temperature raising speed, the more the densification by sintering is promoted, and a high sintered density can be obtained. Table 2 shows a sintered body when the temperature range of 1000 to 1300 ° C. is raised at a rate of temperature increase of 30 ° C./hr, 100 ° C./hr, and 300 ° C./hr in the air under the above-described conditions. Although the relationship between the density and the heating rate is shown, it can be seen that densification is promoted as the heating rate increases. Therefore, in the present invention, in the case of a predetermined PO ₂ atmosphere, the temperature increase rate is selected so that a sintered density equivalent to or close to the sintered density obtained by firing in the N ₂ atmosphere with the least deformation due to firing is obtained. It is. By setting the selected high temperature rising rate, spinelization is completed before reaching the most contracting temperature range, so that closed pores are hardly formed, sinterability is improved, and deformation is suppressed.

  As described above, the temperature rising rate needs to be set in the temperature range of 1000 ° C. or higher according to the present invention. What is necessary is just to set it as the temperature increase rate of 30-600 degrees C / hr in the temperature range below 1000 degreeC. If it is less than 30 ° C./hr, the firing time becomes long, which is disadvantageous for industrial production. If it exceeds 600 ° C./hr, the release of the gas added for the preparation of granules is abruptly released and there is a concern about the occurrence of cracks. Because. A more preferable temperature increase rate in the temperature range below 1000 ° C. is 100 to 500 ° C./hr, and a more preferable temperature increase rate is 100 to 300 ° C./hr.

The firing atmosphere may be N ₂ atmosphere or firing in air up to 1000 ° C. Thereafter, the atmosphere is controlled with PO ₂ , but in reality, the PO ₂ varies in the firing atmosphere. Therefore, in the present invention, in order to cope with this variation in PO ₂ , the temperature rising rate is a temperature rising rate-deformation amount diagram when firing in an N ₂ atmosphere and a temperature rising rate when firing in a predetermined PO ₂ atmosphere. It sets based on a temperature rate-deformation amount diagram. In the firing atmosphere, the region in which the N ₂ atmosphere is maintained does not increase the amount of deformation even when the rate of temperature increase is increased, while the region in which the PO ₂ is high without maintaining the N ₂ atmosphere. The amount of deformation can be reduced by increasing the heating rate.

In this invention, a calcination temperature can be suitably selected from the range of 1200-1450 degreeC. If the temperature is lower than 1200 ° C., the grain growth is not promoted. If the temperature exceeds 1450 ° C., the evaporation of zinc appears remarkably, and the grain grows too much to deteriorate the loss. A more preferable firing temperature is 1250 to 1400 ° C, and a more preferable firing temperature is 1250 to 1350 ° C. The atmosphere at the firing temperature is such that PO ₂ is less than 3%, desirably 2% or less, more desirably 1% or less.

There is no particular limitation on the composition of the Mn—Zn ferrite targeted by the present invention. It can be widely applied to commonly used or known compositions, and includes at least the composition of Fe ₂ O ₃ : 52 to 54 mol%, Mn ₂ O ₃ : 25 to 35 mol%, and ZnO: the balance. Moreover, the subcomponent mentioned above can be included suitably with respect to this main component.

It is a graph which shows the relationship between the temperature increase rate and deformation amount in a U-shaped core. It is a graph which shows the relationship between the temperature increase rate and deformation amount in an E-type core. It is a graph which shows the relationship between the temperature increase rate and deformation amount in a U-shaped core. It is a figure which shows one example of the temperature rising pattern by this invention. It is a figure which shows the other example of the temperature rising pattern by this invention. It is a block diagram which shows the structure of the sintering furnace by this invention. It is a perspective view which shows a U-shaped core. It is a perspective view which shows an E-type core.

Explanation of symbols

1 ... sintering furnace main body, 2 ... heat source, 3 ... PO ₂ sensor, 4 ... control unit, 5 ... tray, 10 ... sintering furnace system

Claims (10)

A temperature raising process of raising the temperature of the Mn—Zn-based ferrite molded body having a predetermined core shape to a predetermined temperature;
A holding process following the temperature raising process;
A temperature lowering process following the holding process,
A method for firing a Mn—Zn ferrite core, characterized in that, in the temperature raising process, the temperature is raised at a temperature raising rate determined based on an oxygen partial pressure (PO ₂ ) in a firing atmosphere. The heating rate is
_{2. The} method for firing a Mn—Zn ferrite core according to claim 1, which is determined based on PO ₂ in the firing atmosphere and a deformation amount of the core shape obtained in advance for the PO ₂ .   The method for firing a Mn—Zn ferrite core according to claim 2, wherein a heating rate at which the deformation amount of the core shape obtained in advance is minimized. 4. The Mn—Zn system according to claim 3, wherein a temperature increase rate at which the deformation amount of the core shape is minimized is determined based on a deformation amount of the core shape due to firing in a nitrogen (N ₂ ) atmosphere. A method for firing a ferrite core. The temperature range of 1000 to 1300 ° C is increased at a temperature increase rate determined based on PO ₂ in the firing atmosphere. The Mn-Zn-based ferrite core according to any one of claims 1 to 4, Firing method. A molded body manufacturing step of manufacturing a Mn-Zn ferrite molded body having a predetermined core shape;
A firing step of firing the molded body,
A method for producing a Mn—Zn-based ferrite core, characterized in that, in the temperature raising process in the firing step, the temperature is raised at a rate of temperature rise corresponding to a change in oxygen partial pressure (PO ₂ ) in the firing atmosphere. The method for producing a Mn—Zn ferrite core according to claim 6, wherein PO ₂ in the firing atmosphere is detected, and a temperature rising rate is determined based on the detection result. A relationship between the deformation amount of the core shape corresponding to a predetermined PO ₂ and a temperature increase rate is obtained in advance, and the temperature increase rate is determined by comparing the relationship with the change in PO _{2 in} the firing atmosphere. The manufacturing method of the Mn-Zn type ferrite core of Claim 6 or 7. A sintering furnace body;
A heating source disposed in the sintering furnace body;
A sensor disposed in the sintering furnace body and detecting an oxygen partial pressure (PO ₂ ) in the sintering furnace body;
A control unit for controlling the heating temperature of the heating source based on the detected PO ₂ ;
A sintering furnace system comprising: The control of the heating source, in association with a heating rate deformation amount of the fired body is minimized and the predetermined PO ₂ at a given PO _2, and the PO ₂ sensed by the sensor storage The firing furnace system according to claim 9, which is performed based on a relationship between the amount of deformation and the rate of temperature increase.

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