JP2855378B2 - Manufacturing method of soft ferrite powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a soft ferrite powder by a spray roasting method.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a composite oxide using a spray roasting method, a method of directly spraying a mixed aqueous solution of a compound such as a metal chloride or a nitrate into a combustion flame and subjecting the mixture to pyrolysis combustion is known. Are known. However, the resulting oxide usually contains 0.4 to 2.0% by weight of chlorine. These residual chlorines are liberated when the core is fired in the ferrite production process , and have harmful effects such as accelerating corrosion and deterioration of equipment such as a firing furnace and causing abnormal ferrite grain growth. Therefore, various proposals have been made on the reduction. In particular, JP-A-2-271923 is known. This known example is a method for producing a raw material oxide for ferrite which enables removal of harmful chlorine and maintains a particle size in a range suitable for press molding. And then oxidatively roasted to form a mixture of oxides, and heating the mixed oxide to a temperature range of 600 to 1000 ° C. to reduce the residual chlorine amount to 500 mmp or less and to reduce the particle size. Is adjusted to 0.5 to 1.3 μm, which is optimal for press molding, to improve the molding density.

[0003]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 2-271923, when a chlorine-based gas at a high temperature and a high concentration is present, heating using a Ni, Cr-based heat-resistant and corrosion-resistant material is performed. In the furnace, Ni and Cr in the material react with chlorine and Ni and Cr are picked up in the powder of the product, which causes quality problems, and the furnace body is severely corroded, and there are problems in running cost and maintenance. And the like.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes such disadvantages of the prior art and utilizes the fact that most of the chlorine contained in the roasted powder can be removed by low-temperature heating. And a method of reducing chlorine corrosion by independently performing crystal grain size control heating. The point is that the metal chlorides constituting the ferrite are mixed, and the raw material oxide for ferrite obtained by spray roasting is heated in a temperature range of 400 ° C. to 600 ° C. to perform primary dechlorination. After the treatment, continue to 600 ℃ ~ 100
A method for producing a soft ferrite powder characterized by performing a two-stage heat treatment of heating at 0 ° C. to control crystal grains and perform secondary dechlorination.

[0005]

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the relationship between the heating temperature of the oxide mixture and the chlorine concentration. That is, the oxide mixture is heated to 400 ° C.
Heat treatment in the temperature range of ~ 1000 ° C
It shows the change in the residual chlorine concentration after holding for one minute. According to this, the chlorine concentration containing 0.4-2.0% decreases to 0.05-0.12% when heated to 600 ° C., and particularly when it exceeds 800 ° C., the target chlorine concentration of 0 It can be seen that the level is as extremely low as 0.05% or less. Next, FIG. 2 also shows the heating temperature of the oxide mixture and N
It is a figure which shows the relationship between the heavy metal content of i, Cr, and chlorine concentration. From this figure, it can be seen that the chlorine concentration is 400
° C, and suddenly decreases to 0.05% at 800 ° C.
It can be seen that at 1000 ° C., it is reduced to 0.05% or less. On the other hand, the content of heavy metals such as Ni and Cr is 4
The temperature rapidly increases from 00 ° C. to 800 ° C., and particularly at 800 ° C., Ni, about 430 ppm, and Cr show extremely high values of about 800 ppm. This means that when the oxide mixture is heat treated at a time to a temperature range of 600 ° C. to 1000 ° C., the chlorine concentration can be reduced to 0.05% or less, but Ni and Cr increase. Therefore, a core having high characteristics cannot be produced from the obtained recovered powder. The reason why Ni and Cr increase when the high temperature treatment is performed is as follows. For example, when a rotary kiln lined with a Ni, Cr heat-resistant and corrosion-resistant material is used, the Ni and C are increased.
Under conditions where the r-based heat-resistant and corrosion-resistant material is at a high temperature and chlorine and hydrogen chloride remain, it is considered that the lining of the furnace is corroded and Ni and Cr are generated from the surface. It has been found that this phenomenon is particularly likely to occur under high temperature conditions with a high chlorine content, and that the rate of actual occurrence is extremely high. In such a state, the furnace body is greatly corroded, which is extremely problematic in terms of maintenance and running costs.

FIG. 3 is a graph showing the relationship between the secondary heating temperature, the chlorine concentration and the heavy metal content of Ni and Cr according to the present invention. According to this, as primary heating, from 400 ° C. to 6 ° C.
By heating at a low temperature of 00 ° C., the chloride concentration of 0.4% to 2.0%, which is usually contained, is 0.1 to 0.1%.
Reduced to 15%. As a result, 600 ° C ~ 100
Even if it is heated to 0 ° C., the effect of chlorine, hydrogen chloride, etc. on Ni, Cr-based heat-resistant and corrosion-resistant materials is extremely large because chloride is already removed by primary heating (hereinafter referred to as dechlorination). As shown in FIG. 3, the residual chloride content can reach the target level of 0.05% or less as shown in FIG.
The r content is also reduced to about 100 ppm or less, and this value can be maintained. That is, even under a high temperature condition, the heating is performed after most of the dechlorination has already been performed by the primary heating.
The effect on r-based heat-resistant and corrosion-resistant materials is extremely small. Therefore, the pickup from Ni, Cr-based heat-resistant and corrosion-resistant materials does not occur, and the Ni and Cr content in the product powder is kept at an extremely low level. Can be. In addition, since the raw material oxide for ferrite roasted from metal chloride has a fine particle size,
Heat treatment is performed to control the crystal grain size.
At that time, it was found that even if the two-stage heating according to the present invention was performed, the crystal grain size did not change in either the single heating or the double heating. Therefore, the crystal grain size control can be performed simultaneously with the second dechlorination at 600 ° C. to 1000 ° C.

[0007]

EXAMPLE After mixing aqueous solutions of FeCl ₂ , MnCl ₂ and ZnCl _{2 at} a predetermined molar ratio, the mixture was spray-roasted at 800 ° C. The residual chloride amount of the obtained oxide was 1.0%. Next, this oxide is granulated by a granulator, and is then dried in an air stream at a temperature range of 400 ° C. to 600 ° C. using a rotary kiln lined with a heat-resistant and corrosion-resistant Ni, Cr-based material.
The amount of residual chloride after heating for 0 minutes changed to 0.12%. Next, the primary dechlorinated oxide is heated again in a second stage for 10 minutes in an air stream using a rotary kiln similar to the above, and after heating from 600 ° C. to 1000 ° C., the residual oxide remains. The chlorine content was 0.05%, the Ni and Cr concentrations were 80 ppm and 90 ppm, respectively, and the average particle size was adjusted in the range of 0.5 μm to 1.2 μm.
These powders were granulated and formed into a toroidal core. This molded body is sintered at a temperature of 1150 ° C to 1250 ° C,
Sintering was performed in a nitrogen atmosphere containing oxygen for 3 hours. As a result of measuring and evaluating the iron loss of the sintered core at 100 KHZ and 200 mT, a very excellent value was obtained. On the other hand, as in the conventional case, the ternary composite oxide under the same
Using a rotary kiln lined with an i, Cr-based heat-resistant and corrosion-resistant material and heating it from 600 ° C to 1000 ° C as a result of one-step heating, the chlorine concentration certainly becomes 0.05% or less.
Ni and Cr concentrations are 400 ppm and 800 ppm, respectively.
And an extremely high content. The composite oxide was similarly granulated and formed into a toroidal core, and the magnetic properties of the sintered core were evaluated by measuring the iron loss at 100 KHZ and 200 mT. As a result, this value was extremely high. Was extremely inferior to the present invention.

[0008]

As described above, by subjecting a mixed oxide obtained by spray roasting to a mixed chloride of the main metal elements constituting ferrite to the treatment of the present invention, the residual chlorine content harmful to the subsequent process is reduced. Can be efficiently reduced to the target level. At the same time, despite the heating furnace lined with Ni, Cr based heat and corrosion resistant materials, Ni, Cr
Can achieve the target level of about 100 ppm or less, and the crystal grain size of the recovered powder can be controlled. As a result, a ferrite core having extremely excellent magnetic properties can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a heating temperature of an oxide mixture and a chlorine concentration;

FIG. 2 is a diagram showing the relationship between the heating temperature of the oxide mixture, the content of heavy metals such as Ni and Cr, and the concentration of chlorine,

FIG. 3 shows the secondary heating temperature, chlorine concentration and N according to the present invention.
It is a figure which shows the relationship with the heavy metal content of i and Cr.

Continued on the front page (72) Inventor Yoshitaka Yamana 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Inside the Kimitsu Works (72) Inventor Shoichi Nagata 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Inside Kimitsu Works (72) Inventor Takehiko Okubo 7-1-14 Ginza, Chuo-ku, Tokyo Inside Chemi-Rite Industry Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C01G 49/00-49 / 08

Claims (1)

(57) [Claims] 1. Chloride of metal element constituting ferrite
The solution was mixed and then the ferrite raw material oxide obtained by spraying roasting, heating in the temperature range of 400 ° C. to 600 ° C., subjected to primary de-chlorine treatment, continued 6
A method for producing a soft ferrite powder, comprising heating at 00 ° C to 1000 ° C and performing a two-step heat treatment for controlling crystal grains and performing secondary dechlorination.