JPH0633951B2 - High temperature heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention improves the product quality by lowering the gas partial pressure of carbon and carbon compounds in a high-temperature heating furnace and, at the same time, suppressing the fine carbon powder from floating. More specifically, regarding a high temperature heating furnace that can be used, the carbon structural material of the high temperature heating furnace in which the furnace core is constructed of the carbon structural material is SiO 2.
The present invention relates to a high temperature heating furnace which is characterized by reacting with a gas and converting its surface into SiC.

(Prior Art) Conventionally, most parts of a high-temperature heating furnace that are exposed to high temperatures are made of graphite. In addition, the method of use was to provide a molded product, which is a processed product such as carbon fiber, as a heat insulating material, and arrange a container such as a graphite sleeve and a graphite heat shield plate inside the furnace core.

However, if carbon structural materials are used in the parts of the furnace that are exposed to high temperatures of 1000 ° C or higher, carbon vapor in the furnace atmosphere,
Gases such as CO ₂ and CO, carbon fine powder, etc. are mixed and permeate and diffuse into a product in a high temperature heating furnace or cause a reaction, which has a drawback that the product quality is significantly adversely affected. .

Further, carbon has a drawback that it is easily oxidized in refractory materials and that the strength deterioration due to oxidation rapidly progresses.

(Problems to be Solved by the Invention) In view of these conventional drawbacks, the present invention aims to eliminate and solve the drawbacks of the prior art by reacting a carbon structural member of a conventional high temperature heating furnace with SiO gas. , By converting the surface layer to SiC to impart oxidation resistance to the carbon structural material, lower the gas partial pressure of carbon and carbon compounds in the furnace atmosphere, eliminate the floating of carbon fine powder, and (EN) A clean high-temperature heating furnace capable of stably producing high-quality products by preventing carburization and reaction with carbon.

(Means and Actions for Solving Problems) In the present invention, the CVD method and the conversion method are the main methods for converting the surface of the carbon structural material into SiC.

Among these, when SiC is deposited on the surface of carbon by the CVD method, the adhesive strength between the carbon and the SiC film is not sufficiently strong, and a difference in thermal expansion occurs due to heat cycle, and the SiC layer is easily peeled off. There is.

On the other hand, the conversion method uses SiO gas at 1950 ° C to 2000 ° C.
And react with the carbon structural material to remove the surface layer of the carbon substrate by S
This is a method of converting to iC, and since the SiC layer is a conversion of the carbon base material itself, the bond between both structures is extremely strong and the surface layer is not peeled off by the heat cycle.

In addition, compared to ceramic members such as SiC sintered bodies, which are very difficult to perform complex precision machining, the conversion method makes it possible to perform complex precision machining easily at the stage of graphite that is soft and easy to process, and the subsequent conversion of SiC causes Also, since the shape of graphite is maintained as it is and there is almost no dimensional change, there is an advantage that any shape can be easily created without requiring post-processing. From batch furnace to semi-continuous furnace,
It refers to a continuous furnace, and can also be applied to a hot press or a hot isostatic press (HIP).

Further, the carbon structural material is composed of a reactor core of a high temperature heating furnace such as a reaction vessel, a sleeve, a heat shield plate and a sample support.

In addition, the furnace core portion referred to in the present invention is a portion exposed to a high temperature in a high temperature heating furnace, and in FIG. 1 which is an example of a resistance heating type high temperature heating furnace, (1), (2), (3 ), (4) and (5), and in FIG. 2 which is an example of an induction heating type high temperature heating furnace,
Refers to (1), (2) and (5).

Regarding the conversion of these furnace core parts to SiC, it is also possible to convert the whole of each part to SiC, or it is possible to partially mask so that the SiO gas does not hit and leave the carbon surface only at that part. . Similarly, the carbon fiber used as the heat insulating material can be subjected to conversion treatment to convert the surface thereof into SiC, thereby obtaining an effect of preventing oxidation and preventing falling off.

On the other hand, the material of the carbon substrate of the present invention is not limited, but isotropic graphite material is preferably used.

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

(Embodiment) FIG. 1 is a vertical sectional view of a resistance heating type high temperature heating furnace according to an embodiment of the present invention. In this drawing, the furnace core is composed of a high temperature heating container (1), a support (2), a heating element (3), a sleeve (4) and a heat shield plate (5). These high temperature heating vessels
(1), support (2), heating element (3), sleeve (4), heat shield
After processing (5) with isotropic graphite material, conversion treatment (powder mixed with silica powder and silicon powder at a weight ratio of 2: 1 in an Ar atmosphere at 2000 ° C. for 60 minutes) is performed,
The surface layer was converted to SiC. The Al ₂ O ₃ compact was pressure-sintered at 1700 ° C. using a resistance heating type high-temperature heating furnace including the furnace core member thus obtained as shown in FIG.
As a result of analyzing this sample, carbon was not detected at all.

On the other hand, A obtained under the same conditions using a resistance heating high temperature heating furnace having the same size as the furnace shown in FIG. 1 and comprising a graphite core member
As a result of analysis of the 1 ₂ O ₃ sintered body, 0.2% was found in the surface layer.
Carbon was detected. In addition, the entire sample turned gray.

FIG. 2 is a vertical sectional view of an induction heating type high temperature heating furnace which is another embodiment of the present invention. The furnace core is composed of a high temperature heating container (1), a support (2) and a heat shield plate (5). After the high temperature heating container (1), the support (2) and the heat shield plate (5) were processed with an isotropic graphite material, conversion treatment was performed to convert the surface layer into SiC. The Si ₃ N ₄ compact was pressure-sintered at 1850 ° C. using an induction heating type high temperature heating furnace as shown in FIG. 2, which is composed of the furnace core member thus obtained. As a result of analyzing this sintered body, carbon was not detected at all.

On the other hand, Si obtained under the same conditions by using an induction heating type high temperature heating furnace having the same size as the furnace shown in FIG.
As a result of analyzing the ₃ N ₄ sintered body, 0.09% of carbon was detected.

(Effects of the Invention) As is clear from the above description, the high temperature heating furnace of the present invention does not create a carbon atmosphere, so that carbon is prevented from being mixed into the sintered material and a high quality product is stably produced. It is an industrially useful one that has made it possible.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a resistance heating type high temperature heating furnace constructed by a member whose core is converted to SiC, and FIG. 2 is an induction heating high temperature constructed by a member whose core is converted to SiC. It is a longitudinal cross-sectional view showing a heating furnace. Here, (1) is a high temperature heating container, (2) is a support, (3) is a resistance heating element, (4) is a sleeve, (5) is a heat shield, (6) is a heat insulating material, and (7) is Induction coils are shown respectively.

Claims (1)

[Claims] 1. A high temperature heating furnace in which a furnace core is constructed of a carbon structural material, wherein the carbon structural material in the high temperature heating furnace is reacted with SiO gas and the surface thereof is converted into SiC. And high temperature heating furnace.