JPS6356471B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high temperature processing furnace. More specifically, when carbonizing or graphitizing organic matter where a carbon fiber-reinforced substantially carbonaceous composite material (hereinafter abbreviated as C/C) is used as an internal structural member, or when ceramic The present invention relates to a high-temperature treatment furnace suitably used in the production of.

[Prior Art] It has been known to obtain carbon fibers or graphite fibers by carbonizing or graphitizing organic fibers such as acrylonitrile fibers, rayon fibers, and pitch fibers in a heat treatment furnace.

Such a heat treatment furnace is mainly composed of a core tube portion having a central cavity that serves as a treatment chamber for the fibers to be treated, and an outer wall portion disposed through a heat insulating material or the like.

In such heat treatment furnaces, the insulation is supported by insulating metal, ceramic or conventional carbon material.

Heat-resistant metals have a narrow operating temperature range, and ceramics and ordinary carbon materials have low mechanical properties, especially impact strength and bending strength, making them difficult to handle.

As a result of intensive studies on these problems, the inventors of the present invention found that these problems could be solved by using C/C as a structural member, leading to the present invention.

[Structure of the invention]

That is, the present invention is a high-temperature treatment furnace whose internal structural members are made of a carbon fiber-reinforced, substantially carbonaceous composite material.

Specifically, the internal structural members such as the heat insulating support material, the furnace core cylinder support material, the workpiece support material, etc. are made of a composite material substantially made of carbonaceous or graphite reinforced with carbonaceous or graphite fibers. This is a high temperature heat treatment furnace.

A high-temperature heat treatment furnace using such internal structural members can operate stably for a long period of time, and according to the furnace,
A product structure with stable quality is possible.

In conventional furnaces, for example, in furnaces that use the heat-resistant metal Inconel as a support, the support is exposed to high temperatures due to contraction of the alumina insulation layer, which deforms and bends the support, causing the insulation layer to shift, causing the temperature of the outer wall to increase. The temperature rose abnormally and the operation had to be stopped. For this reason, in the conventional furnace, the operation is usually stopped after two months and repairs are required, but the furnace of the present invention can be operated for six months without any problems, as will be described later.

In the present invention, carbon fibers used as reinforcing materials for C/C include acrylonitrile carbon fibers, pitch carbon fibers, rayon carbon fibers, and graphite fibers obtained by graphitizing these fibers. The forms of reinforcing materials in C/C are woven fabrics, random mats, paper, and laminates thereof.The fibers themselves can be continuous fibers or discontinuous fibers, but discontinuous fibers are used to reduce thermal conductivity. It is preferable to do so. In particular, spun yarn cloth laminates have low thermal conductivity of C/C,
Preferable in terms of machinability.

The fiber volume content (capacity) of the reinforcing fibers in C/C is preferably 10 to 65%. If the content is lower than 10%, mechanical properties such as bending strength will decrease;
If it is higher than 65%, damage such as delamination between layers will occur more frequently in the C/C manufacturing process. Particularly preferably 20 to 55%.

The production of C/C in the present invention involves impregnating carbon fibers or graphite fibers with a thermosetting resin such as phenol, furan, or epoxy, molding and hardening them into a desired shape, and then carbonizing or graphitizing them in an inert atmosphere to create a composite material. shall be. Next, the composite material is impregnated with a thermosetting resin or pitch, and then carbonized or graphitized to make it denser until the required mechanical properties are obtained. This densification process is carried out by the so-called chemical paper deposition (CVD) method, in which carbon is deposited by thermally decomposing hydrocarbon gas onto the composite material held at high temperature or onto carbon fibers or graphite fibers held in a desired shape. You may also do so.

It is preferable to carry out densification until the bulk density of C/C becomes 0.8 to 1.7 g/cm ³ . If it is higher than 1.7 g/cm ³ , the heat conduction of the C/C becomes excessive, and the obtained C/C becomes unsuitable as an internal structural member of a high-temperature treatment furnace. Conversely, if the bulk density is lower than 0.8 g/cm ³ , the mechanical properties will be insufficient.

Further, the C/C used in the present invention is preferably heat-treated at 800 to 2400°C during the manufacturing process. If the heat treatment temperature is low, volatile matter remains in the C/C, reducing the purity of the atmosphere in the high temperature treatment furnace. On the other hand, when subjected to heat treatment at temperatures exceeding 2400°C, graphitization of C/C progresses, resulting in deterioration in strength and increase in thermal conductivity, making it unsuitable for internal structural members.

Among the internal structural members in a high-temperature treatment furnace, the members to which the C/C of the present invention can be particularly suitably utilized include:
Induction heating furnace susceptor or ordinary furnace core tube,
There are heater elements for resistance heating, work supports or crucibles, insulation support materials, etc.

Since these members are normally used in a high temperature atmosphere, they are sealed in a non-oxidizing atmosphere such as an inert gas.

Usually, only one end of the heat insulating support material is supported and fixed by the outer wall, so it becomes a so-called cantilever beam. This cantilever beam usually receives a uniformly distributed load by supporting the insulation material, and therefore receives a larger stress as it moves from the tip (free end) to the fixed end.
The shape has been changed to make the fixing part thicker or wider than the tip part, or a reinforcing material is placed on the lower side on a shelf plate having a T-shaped cross section. Although it is preferable to reduce the cross-sectional area of the tip of the support material from the viewpoint of heat insulation efficiency, it tends to become unstable from the viewpoint of supporting the heat insulation material. In consideration of these points, by reducing the density at the tip of the heat insulating material supporting structural member and creating a density gradient toward the fixed end, it is possible to achieve both a heat insulating effect and stable support of the heat insulating material.

〔Example〕

Example 1 Carbon fiber strand with a diameter of 7μ [Toho Veslon
Besphite HTA-12K manufactured by Co., Ltd.] was impregnated with furan resin and the inner diameter was adjusted to a fiber volume content of 55%.
It was inserted into a 12 mm ceramic pipe, heated and cured, and then carbonized at 1000°C in a nitrogen atmosphere to obtain a unidirectional carbon fiber reinforced carbon composite material. A prepreg impregnated with 36% resin content of phenol resin was wrapped around the composite material to an outer diameter of 20 mm around a 3000 filament carbon fiber plain weave cloth [Beshuite Cloth W-3101 manufactured by Toho Bethlon Co., Ltd.].
After heating and curing at 170℃, carbonizing at 1000℃ in a nitrogen atmosphere, and further impregnating with cortar pitch and carbonizing three times, the central part is strengthened in one direction and the outer layer is strengthened in two directions, resulting in a bulk density of 1.6g/cm ³ . A round rod-shaped composite material with a fiber volume content of 53% was obtained.

After laminating a prepreg impregnated with 38% resin content of phenolic resin on carbon fiber mat (fabric weight 250 g/m ² ), it was cured by heating at 170°C to obtain a composite material with a fiber volume content of 45% and a density of 1.2 g/cm ^{3 .} Ta. After carbonizing this composite material at 1000° C. in a nitrogen atmosphere, pitch impregnation and carbonization were performed three times to obtain a flat composite material with a thickness of 10 mm.

3000 filament carbon fiber plain weave cloth (basis weight
200g/m ² ) prepreg impregnated with 35% resin content of phenolic resin is laminated and cured by heating to a thickness of 20mm, a fiber volume content of 50%, and a density of 1.3g/cm ³
A cured product was obtained. After carbonizing this cured product in a nitrogen atmosphere, pitch impregnation and carbonization were repeated five times to obtain a composite material with a thickness of 20 mm and a bulk density of 1.6 g/cm ³ .

One end of the flat composite material with a thickness of 10 mm was fixed to the outer wall of a high-temperature heat treatment furnace, a hole with a diameter of 22 mm was made in this flat plate, and the round bar-shaped composite material was passed through. Cut the male thread to the thickness of 20mm.
Cut a female thread to match this in the composite material,
It was shaped like a nut, and the round bar was fixed thereto. This round rod penetrates the flat felt insulation material and fixes it.
It was used as a fixed support material for the heat insulating material of a high-temperature treatment furnace.

In this high-temperature heat treatment furnace, the furnace core surrounded by insulation material was used as the heat treatment chamber, and it was maintained at 1,600℃ in a nitrogen atmosphere for 6 months, but the insulation material shifted and other problems occurred, which hindered the stable operation of the high-temperature heat treatment furnace. No similar phenomenon was observed.

Claims (1)

[Scope of Claims] 1. A high-temperature treatment furnace whose internal structural members are made of a carbon fiber-reinforced, substantially carbonaceous composite material. 2. The high-temperature treatment furnace according to claim 1, in which a composite material is used as a heat insulating support material. 3. A high-temperature treatment furnace according to claim 1, in which a composite material is used as a cantilever-shaped heat insulating support material. 4. The high temperature treatment furnace according to claim 1, wherein the internal structural member is a composite material having a density of 0.8 to 1.7 g/cm ³ . 5. The high-temperature treatment furnace according to claim 1, wherein the internal structural member is a composite material having a fiber volume content of 20 to 55%. 6. The high-temperature treatment furnace according to claim 1, wherein the internal structural member is a composite material in which the carbon fibers are discontinuous fibers. 7. The high-temperature treatment furnace according to claim 1, wherein the internal structural member is a composite material that is a laminate of carbon fiber fabrics. 8. The high temperature treatment furnace according to claim 7, wherein the carbon fiber fabric is a spun yarn cloth.