JPH063054A - Ceramic calcining furnace - Google Patents

Abstract

PURPOSE:To obtain a calcining furnace having a furnace core tube which enables the suppression of reaction with a heavy metal vapor sufficiently to allow practical use. CONSTITUTION:This calcining furnace 1 has a cylindrical furnace core tube 2 to transfer a ceramic material with own rotating action. The furnace core tube 2 has an inner cylinder 3 comprising a high purity and highly dense ceramic material inserted into an outer cylinder 4 comprising a heat resistant metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic calcining furnace used for calcining a dielectric material or a piezoelectric material, which is a raw material for forming electronic parts.

[0002]

2. Description of the Related Art When calcining a ceramic raw material such as a barium titanate-based dielectric material or a lead zirconate titanate-based piezoelectric material, a ceramic calcining furnace called a rotary kiln structure (hereinafter referred to as a calcining furnace) is used. ) Is commonly used. That is, this calcination furnace 10
As shown in a simplified manner in FIG. 4, it is provided with a cylindrical core tube 11 which is arranged with a constant inclination along the longitudinal direction and is rotatably supported. Furnace body 1 arranged to surround the outer periphery
A temperature controllable heater 13 is provided inside the unit 2.

A ceramic raw material (not shown) to be calcined by using the calcining furnace 10 is a core tube 1
1 is charged from one end located upward, and is then calcined by being heated by the heater 12 while being transferred to the other end positioned downward by the rotation operation of the core tube 11 itself. Note that, in FIG. 4, the illustration of the support structure and the rotation drive structure of the core tube 11 is omitted.

[0004]

By the way, in the calcination furnace having the above-mentioned conventional structure, the temperature difference between the end portion and the central portion along the longitudinal direction of the core tube 11 is large, and
Since the core tube 11 is rotationally driven while repeatedly receiving a large heat shock, a core tube 11 made of a material excellent in hot strength characteristics, for example, a ceramic material fired in a porous state is used. The furnace core tube 11 is made of a chamotte or mullite ceramic material having a relatively low purity.

However, when the ceramic raw material is calcined by using such a furnace core tube 11, heavy metal vapor such as lead generated from the ceramic raw material and the ceramic material forming the furnace core tube 11 react violently. As a result, the deterioration of the core tube 11 is accelerated, and as a result, the core tube 11 is damaged in a short period of time. In addition, reaction products such as lead glass, silica, and alumina may be generated due to the reaction between the heavy metal vapor and the core tube 11. As a result, these reaction products are mixed as impurities in the ceramic raw material as a product. However, it may cause quality inconvenience.

When a furnace core tube made of a high-purity and high-density ceramic material is used, it is considered that the reaction between the furnace core tube and the heavy metal vapor does not occur. A furnace core tube made of such a material may not be able to obtain a sufficiently high mechanical strength thermally, and at present it has not yet been put to practical use.

The present invention was devised in view of such inconvenience, and it is a calcining furnace provided with a furnace core tube which can suppress the reaction with heavy metal vapor sufficiently and can be put to practical use. The purpose is to provide.

[0008]

A calcining furnace according to the present invention comprises:
In order to achieve such an object, it is equipped with a cylindrical core tube that transfers the ceramic raw material by its own rotating operation, and this core tube is made of a high purity and high density ceramic material that is heat resistant. It is characterized in that it has a structure of being inserted into an outer cylinder made of metal.

[0009]

According to the above construction, since the inner cylinder forming the furnace core tube is made of high purity and high density ceramic material,
The reaction between the inner cylinder and the heavy metal vapor hardly occurs. And, even if cracks due to the influence of temperature difference or heat shock may occur due to insufficient thermal mechanical strength of this inner cylinder, the longitudinal direction of this inner cylinder Since the periphery along the line is covered with the outer cylinder made of a heat-resistant metal, the calcination of the ceramic raw material can be continued as it is without causing any inconvenience.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view showing a simplified overall structure of a calcining furnace according to this embodiment, FIG. 2 is a perspective view showing a simplified structure of a core tube, and FIG. 3 is a modification of the core tube. It is an exploded perspective view which shows a structure, and the code | symbol 1 in these figures has shown the calcination furnace. In addition, in FIG. 1, FIG.
The same reference numerals are given to the portions that are the same as each other, and description thereof is omitted here.

This calcination furnace 1 is provided with a cylindrical core tube 2 which is arranged with a certain inclination along the longitudinal direction and which transfers the ceramic raw material by its own rotating operation. As shown in FIG. 2, the inner cylinder 3 is inserted into the outer cylinder 4. That is, the inner cylinder 3 that constitutes the furnace core tube 2 is formed as a long, integral tube made of a high-purity and high-density ceramic material, for example, an alumina sintered body having a purity of 99.5% or more. The outer cylinder 4 is formed as a long, integral tube made of a heat-resistant metal such as Inconel. Then, an irregular heat insulating material (not shown) such as a ceramic fiber blanket is packed in the diametrical gap between the inner cylinder 3 and the outer cylinder 4 integrated by these insertions. ing.

Here, the inner cylinder 3 which constitutes the furnace core tube 2
Is not limited to a long integral tube, for example,
It may be integrated by arranging the divided and divided pieces in a continuous manner. Further, the outer cylinder 4 is not limited to the long integral tube, and for example, as shown in FIG. 3, the outer cylinder 4 may be formed in a split shape or a split shape along the longitudinal direction. Alternatively, the inner cylinder 3 may be sandwiched and integrated by connecting them using bolts, nuts and the like.

Therefore, the ceramic raw material (not shown) to be calcined by using the calcining furnace 1 is also charged from the one end side of the inner tube 3 constituting the furnace core tube 2 which is located upward as in the conventional example. In addition, the core tube 2 is calcinated by the heater 12 while being transferred toward the other end side which is positioned downward by the rotating operation of the core tube 2 itself. In addition,
Even if heavy metal vapor may be generated from the ceramic raw material during this calcination, since the inner cylinder 3 is formed of a high-purity and high-density ceramic raw material, the inner cylinder 3 reacts with the heavy metal vapor. It is almost impossible to do.

By the way, the inventors of the present invention have conducted an investigation on the ceramic raw material that has been calcined by using the furnace core tube 2 having the above structure and the conventional furnace core tube 11, respectively. The contents of this survey will be described.

First, BaCO ₃ , TiO ₂ and PbO were prepared, mixed using a ball mill, and the resulting mixture was dehydrated and dried and granulated to prepare a ceramic raw material for lead-based barium titanate. did. Then, in the furnace core tubes 2 and 11 provided in the calcination furnace 1 according to the present embodiment and the calcination furnace 10 according to the conventional example, 1 kg / g of the ceramic raw material
The ceramic raw material was calcined by heating to 1100 ° C. at a heating rate of 500 ° C./hr or more while quantitatively adding each hr. Next, each of the calcined ceramic raw materials was crushed, a binder was added to each, and the mixture was granulated, followed by molding to prepare a disk-shaped sample having a diameter of 10 mm.

Further, each of the disk-shaped samples thus obtained was sintered at a temperature of 1100 ° C., and impurities contained in each of the disk-shaped samples obtained as a sintered body were measured. As shown in Table 1, it is clear that the amount of impurities is smaller when the furnace core tube 2 according to the present embodiment is used than when the furnace core tube 11 according to the conventional example is used. It was In addition, the product of this example in Table 1 means a product made of a ceramic raw material that is calcined using a calcining furnace 1 equipped with a furnace core tube 2 according to this example,
The conventional product means a product made of a ceramic raw material that is calcined by using a calcining furnace 10 including a furnace core tube 11 according to the conventional example. Further, here, these impurities are those in which the reaction product generated by the reaction between the heavy metal vapor generated along with the calcination of the ceramic raw material and the furnace core tube is mixed in the ceramic raw material.

[0018]

[Table 1]

Further, since pinholes are generated in the sintered body made of the ceramic raw material containing impurities, the pinholes in the sintered body made of the ceramic raw material which are calcined in each of the calcination furnaces 1 and 10. When the number of occurrences of 8 was generated in the sintered body prepared by the conventional example, the number of generated pinholes of 8 pieces / cm ² was found, while the sintering produced by using the calcining furnace 1 according to the present example. 2 pieces / cm ^{2 in the} body
It was confirmed that it would be significantly reduced. Further, in the core tube 11 according to the conventional example, only about 3000 kg of calcination per one can be performed, whereas in the core tube 2 according to the present example, calcination can be performed up to about 30,000 kg, and the life thereof is about 10. It was confirmed that it doubled. When the inner surface state of the inner cylinder 3 constituting the furnace core tube 2 used for calcination of the ceramic raw material was visually inspected, some cracks were found, but despite the occurrence of cracks, In other words, the inner cylinder 3 was supported by the outer cylinder 4 without any inconvenience.

[0020]

As described above, the calcination furnace according to the present invention includes the furnace core tube having a structure in which the inner cylinder made of high-purity and high-density ceramic material is inserted into the outer cylinder made of heat-resistant metal. Therefore, the reaction between the heavy metal vapor generated by the calcination of the ceramic raw material and the inner cylinder is sufficiently suppressed, and the inconvenience in quality due to the mixing of the reaction product does not occur. Further, even if some cracks may occur due to insufficient thermal mechanical strength of the inner cylinder forming the furnace core tube, this inner cylinder is supported by the outer cylinder, and Since it is reinforced, calcination of the ceramic raw material can be continued as it is without causing any inconvenience, and an effect that it can be put to practical use is obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a simplified overall structure of a calcination furnace according to the present embodiment.

FIG. 2 is a perspective view showing a simplified structure of a core tube.

FIG. 3 is an exploded perspective view showing a modified structure of the furnace core tube.

FIG. 4 is a vertical cross-sectional view showing a simplified overall structure of a conventional calcination furnace.

[Explanation of symbols]

 1 Calcination furnace 2 Core tube 3 Inner cylinder 4 Outer cylinder

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[Procedure amendment]

[Submission date] August 31, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

However, when the ceramic raw material is calcined by using such a furnace core tube 11, heavy metal vapor such as lead generated from the ceramic raw material and the ceramic material forming the furnace core tube 11 react violently. As a result, the deterioration of the core tube 11 is accelerated, and as a result, the core tube 11 is damaged in a short period of time. Also, there the reaction product, such as lead glass is produced by the reaction of the heavy metal vapors and the core tube 11, these reaction products, silica,
As a result of inclusion of alumina or the like as an impurity in the ceramic raw material used as a product, quality inconvenience may occur.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

[0018]

[Table 1]

Claims (1)

[Claims] 1. A cylindrical core tube (2) for transferring a ceramic raw material according to its rotation operation is provided, and this core tube (2) is an inner cylinder made of high-purity and high-density ceramic material. (3) is an outer cylinder made of heat-resistant metal (4)
Ceramic calcination furnace characterized by having a structure inserted in.