JPH0677039A - Method of manufacturing mn-zn ferrite sintered body - Google Patents

Abstract

PURPOSE:To manufacture a large sized and high density sintered bodies by a method wherein Mn-Zn ferrite raw material mixed particles are filled up and molded in a metallic mold internally lined with rubber while vertically vibrating the metallic mold and after being cold hydrostatically pressurized to be sintered at atmospheric pressure for performing hot hydrostatically pressuring step. CONSTITUTION:Mn-Zn ferrite raw material mixed particles comprising the mixed particles of Fe2O3, MnO and ZnO are thrown into a metallic mold internally1ined with rubber to be filled up and molded while vertically vibrating the metallic mold. Next, the molded bodies after being cold hydrostatically pressurized are to be sintered at atmospheric pressure for performing hot hydrostatically pressurizing step. Through these procedures, even large sized high density sintered bodies developing the least cracking defect can be made of previously processed material. Resultantly, the larger sized in higher density sintered bodies can be manufactured without decreasing the yield due to the development of cracking defect, etc., when the former sintered bodies are hot hydrostatically pressurized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high density and large size Mn-Z.
The present invention relates to a method for producing an n-ferrite sintered body.

[0002]

2. Description of the Related Art Conventionally, there are roughly two types of methods for producing a Mn-Zn ferrite sintered body, a dry method and a wet method, and the form of powder to be molded has been various. In this, the powder that has been calcinated and then pulverized is granulated and directly filled in the mold.
A method of pressurizing and molding is widely used. In the case of this method, since the raw material powder is used for calcination, expansion and contraction during secondary firing are small, and a sintered body with high dimensional accuracy can be obtained. If a hot isostatic press (HIP) is applied, a high density of 98% or more can be realized.

[0003]

However, since the powder pulverized after calcination has a very poor fluidity, it is usually necessary to mix an organic compound binder such as a PVA solution to improve the moldability. Therefore, an operation (degreasing) of evaporating the organic compound is required at the time of the secondary firing, and if this operation is not performed successfully, there is a drawback that carbon components remain in the sintered body or voids are generated. In particular, when an attempt was made to increase the size of the sintered body, this tendency became remarkable, and it was difficult to obtain a homogeneous and high-density sintered body.

Further, when the powder crushed after the above-mentioned calcination is directly filled and pressed in a mold for molding, a difference in pressure distribution in the pressing surface is inevitable, and cracks occur in the molded body. There is a drawback that the density becomes non-uniform. In particular, this tendency becomes remarkable when the shape of the mold becomes large, so that it is difficult to produce a large-sized molded body.

Furthermore, when a sintered body made of the powder pulverized after the above-mentioned calcination is subjected to hot isostatic pressing (HIP), the yield of HIP tends to decrease as the shape of the sintered body increases. . In particular, cracks and cracks are the main factors that reduce the yield, and if the cracks suddenly occur a few hours after pressing, it was as dangerous as the rupture of the pressure vessel. Therefore, the present invention has been proposed in view of the above circumstances, and an object thereof is to provide a method for producing a large-sized and high-density sintered body in the production of a Mn-Zn ferrite sintered body.

[0006]

In order to achieve the above object, the present invention provides a Mn-Zn ferrite raw material mixed powder comprising a mixed powder of Fe ₂ O ₃ , MnO and ZnO,
It is put into a mold with rubber adhered inside, filled and molded while vertically vibrating the mold, cold isostatic pressing is performed, and then the molded body is sintered under normal pressure to obtain an appropriate thickness. After processing, it is characterized by hot isostatic pressing.

[0007]

Function: That is, as a pre-process, Fe having excellent fluidity is used.
A mixed powder of ₂ O ₃ , MnO, and ZnO is directly charged into a mold having a rubber adhered to the inside thereof to be filled / molded, cold isostatically pressed, and then sintered under normal pressure. As a result, it is possible to obtain a high-density sintered body that is a pretreatment product and has few cracks / cracks or defects even if it is large, and as a result, when this is hot isostatically pressed, the yield will be increased due to cracks / cracks. It is possible to obtain a large-sized sintered body of higher density without lowering the temperature.

[0008]

The method of producing a Mn-Zn ferrite sintered body according to the present invention will be described below with reference to its examples. First, MnO 22 mol%, Fe ₂ O ₃
The raw materials were weighed so that the mol content was 55 mol% and ZnO was 23 mol%, and the average particle diameter was 0.5 to 0.6 μm in a ball mill.
Milled to a particle size of 2 μm or less. And
The crushed powder is dried with a drier and the water content is 0.2 to 0.
It was set to be 4%.

Next, an inner diameter of 110 mm and a depth of 580 mm in which the dry powder (raw material mixed powder) is closely adhered to rubber
2 kg was put into the columnar mold, and the mold was vertically vibrated for 2 minutes to fill and mold. Subsequently, the molded body together with the rubber was taken out from the mold, and after cold isostatic pressing was performed at 98 MPa, the temperature was raised in a N ₂ atmosphere and sintered at 1350 ° C. in the atmosphere. Furthermore, after slowly cooling to room temperature, it was taken out, the cylindrical sintered body was cut into slices having a diameter of 70 mm, a thickness of 8 mm, and a weight of 200 g, and hot isostatic pressing was performed at 1250 ° C. and 98 MPa.

The sintered body thus obtained was mirror-polished and the pores were observed. Further, the density of the sintered body was examined with the density of Mn-Zn ferrite single crystal having the same composition ratio as 1.
In addition, for comparison, a raw material mixed powder having the same composition ratio was pre-baked and granulated through a sieve of 48 mesh or less using a PVA solution, and 220 g of the granulated material was mechanically pressed with a mold having an inner diameter of 70 mm and degreased Then, it was fired under the same conditions as those of the present invention, and was similarly hot isostatically pressed at 1250 ° C. and 98 MPa. Table 1 shows a comparison between the Mn-Zn ferrite sintered bodies obtained in the present invention and the comparative examples in terms of relative density, residual pores of 1 μm or more, and cracking / cracking incidence.

[0011]

[Table 1]

As is clear from Table 1, the Mn-Zn ferrite sintered body obtained by the method according to the present invention has a high density, a small number of huge pores, and a low cracking / cracking rate.

[0013]

As described above, according to the manufacturing method of the present invention, the Mn-Zn ferrite raw material mixed powder is used in the mold in which the rubber is adhered to the upper and lower sides by utilizing its good fluidity. After filling and molding while vibrating and cold isostatic pressing, the compact is sintered under normal pressure and hot isostatic pressing (HIP). As a result, it is possible to manufacture a large-sized and uniform large-sized Mn-Zn ferrite sintered body without requiring a post-process such as calcination and degreasing, and without lowering the yield by HIP treatment. ing.

Claims (1)

[Claims] 1. A Mn—Zn ferrite raw material mixed powder, which is a mixed powder of Fe ₂ O ₃ , MnO and ZnO, is put into a mold having a rubber adhered inside, and the mold is vertically vibrated and filled. A method for producing a Mn-Zn ferrite sintered body, which comprises performing hot isostatic pressing on a compact that has been molded and subjected to cold isostatic pressing and then sintered under normal pressure.