JPH0217493B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a method for manufacturing a large quartz container in the shape of a hollow cylinder with a curved bottom, and is particularly used for manufacturing semiconductor single crystals. crucible, chiyamba,
This invention relates to a method of manufacturing a large quartz container used as a bell jar.

``Prior Art'' Traditionally, quartz containers have been formed into hollow cylinders by heating one end of a quartz pipe and forming a bottom with a sealed edge in the plastic region. When such a forming method is adopted, as the diameter of the container increases, the amount of compression and energy required to form the bottom become considerably larger than the edge, so the bottom inevitably becomes thinner than the circumference. , resulting in a significant decrease in strength.

Therefore, in order to prevent the wall from becoming thin when forming the bottom, the peripheral edge of the quartz pipe is compressed while being heated and plasticized to reduce its diameter, and a quartz plate is inserted and welded into the reduced diameter opening. We are proposing a quartz container made by molding.

"Problems to be Solved by the Invention" However, in this prior art, the above-mentioned drawback can be solved because there is no need to compress the bottom until it is sealed, but on the contrary, the quartz plate is The welding structure requires skill in welding, which causes problems such as welding position deviation and insufficient strength of the welded part.

For this reason, in the known prior art, a bottom member that has been heat-treated in advance and formed into a curved surface is welded to the end of a hollow cylindrical body that is formed with the same circumferential diameter without reducing the diameter of one end. , has proposed a large quartz container.

However, even in such conventional technology, since the bottom member formed in a curved shape is butted against the end of the hollow cylindrical body and welded, misalignment is likely to occur during welding, and it is difficult to reduce the above-mentioned drawbacks to some extent. is possible, but it does not lead to resolution.

However, if the expansion of the bottom member and the welding of the cylindrical body are performed separately as in the prior art, two heat treatment steps are required.
This not only increases the number of manufacturing steps, but also tends to cause thermal strain between the bulging bottom member and the welding area.

In view of the drawbacks of the prior art, it is an object of the present invention to provide a method of manufacturing a large quartz container that can completely prevent a decrease in strength caused by thinning of the bottom, misalignment during welding, and dimensional distortion.

"Means for Solving Problems" In order to solve these technical problems, the present invention provides a cylinder made of a material with sufficient heat resistance, such as graphite, ceramics, metal, etc., and having a curved bottom. A quartz glass disk and a quartz glass cylinder having the same outer diameter as the disk were successively set in contact with each other so that their outer edges formed the same circumference. For example, by heating the outer edge and the disk surface, the disk is deformed along the curved mold bottom by its own weight and/or by physical external force, and at the same time, both members are brought into thermal contact with each other. We propose a method for manufacturing a large quartz container that has the following essential components.

In this case, the above-mentioned physical external force includes not only the weight of the disk itself but also the negative pressure generated between the quartz glass disk and the bottom of the mold, centrifugal force, etc., or a combination of these. However, it is not necessarily limited to this.

Further, it is preferable to use a heating means capable of heating the cylindrical body or disk made of quartz glass to a plastic state, specifically, a heating means using an arc discharge or a burner.

``Function'' According to this technical means, skill is required because the cylindrical body and the disk are set in the mold and heat-treated to bring them into thermal contact and to bulge the disk. It is possible to manufacture a large quartz container with a predetermined shape without causing any distortion or displacement of the welded portion.

Further, according to the technical means, since the above-mentioned welding and expansion of the disk are performed simultaneously, the heat treatment process is a single step, which greatly reduces the number of manufacturing steps, and at least heats the outer edge and the disk at the same time. Therefore, unlike the prior art, there is no room for thermal strain to occur between the bottom and the welding area.

Furthermore, the present technical means is not formed by compression molding of the periphery, but is formed by bulging the planar bottom of the hollow cylinder under the plastic region, and the extent of the bulge is compared to compression molding. Since the decrease in thickness is so small, the decrease in wall thickness can be almost ignored in terms of strength.

However, by setting the bottom wall thickness to be larger than the circumferential side wall thickness to the extent that it corresponds to the wall thickness reduction, the above drawbacks can be completely eliminated.

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to FIGS. 1 to 2B. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. It's nothing more than that.

In FIG. 1, reference numeral 1 denotes a mold made of a material with sufficient heat resistance, such as graphite, ceramics, metal, etc., and is connected to a central axis C-
It is made rotatable around C', and a small hole 1a is bored in the center of the bottom of its inner wall surface, and is connected to a suction pump (not shown) via a suction pipe 2.

The inner wall surface of the mold 1 has the same shape as the quartz container after molding, that is, the upper part is open, and the inner diameter of the inner wall surface is approximately equal to or slightly larger than the outer diameter of the cylindrical body 3 before molding, which will be described later. The bottom portion 11 is formed in a concave curved shape, and the inner wall surface is smoothed to such an extent that the bottom space below the bottom portion can be substantially sealed by setting a disk 4, which will be described later.

The cylindrical body 3 is formed by cutting a pipe-shaped quartz glass tube having an outer diameter slightly smaller than the inner diameter of the mold 1 into a predetermined length, and its lower end side is formed into a planar shape cooperating with the axis. Note that the lower end side 31 may be formed into a gate-shaped cross section as shown in FIG.
As shown in Figures A and B and Figure 3, it is preferable to form the cross section into a wedge shape with the outer periphery as the apex.

The disk 4 is formed to have the same diameter as the outer diameter of the cylindrical body 3, and its wall thickness is set to be the same as or slightly larger than the thickness of the cylindrical body 3.

Next, a method for manufacturing a large quartz container using mold 1 will be described.

First, the cylindrical body 3 and the disc 4 are arranged inside the mold 1 so that the disc 4 is located on the bottom side, and are brought into contact with each other so that the outer edges of both members form the same circumference. Set.

Next, the inner peripheral surface of the cylindrical body 3 and the upper surface of the disk 4 are heated to 1800° C. by heating means 6 using arc discharge or a burner.
Heating is performed at the above heating temperature to bring both of them into a plastic state, thereby bringing them into thermal contact.

At the same time as the heating or after reaching a plastic state, the suction pump is driven as the mold 1 rotates to exhaust the gas in the space between the disc 4 and the mold bottom 11, and the disc 4 is moved downward. The bottom space A is placed under negative pressure, and at the same time as or before and after the thermal contact with the cylindrical body 3, the disk 4 is moved downward along the mold bottom 11 using the atmospheric pressure existing above the disk 4 as an external force. This results in bulging deformation.

Also, the cylindrical body 3 is heated while being in close contact with the inner wall surface of the mold 1 due to the centrifugal force acting in the radial direction of the cylindrical body 3 due to the rotation of the mold 1, either simultaneously with the thermal contact with the disk 4 or before and after. Correct dimensional distortions that occurred during processing.

As a result, as shown in the right direction of the arrow in FIG. 1, the cylindrical body 3 and the disk 4 are integrally welded, and the disk 4 bulges out in a curved shape along the shape of the mold bottom 11, and the mold A quartz container with the same shape as the inner wall surface can be formed.

In addition, even if you do not use a suction pump as mentioned above,
It is also possible to bulge the disc 4 downward by utilizing the effect of gravity due to the own weight of the plasticized disc 4.

The bottom wall thickness of the quartz container formed in this way is slightly reduced because it is formed by bulging the disk 4 under the plastic region, but the strength is You can almost ignore it.

For example, using a hollow cylinder 3 with an outer diameter of 300 mm, an inner diameter of 290 mm, and a wall thickness of 5 mm, and a disk with an outer diameter of 300 mm and a wall thickness of 5 mm, the distance L from the lower end of the cylinder 3 to the bottom of the mold
(See Figure 1) In other words, when the bulge height is set to about 30 mm, the amount of decrease in the wall thickness of the disk 4 is only about 2%, which can be almost ignored in terms of strength.

However, to solve this problem, the wall thickness of the disk 4 may be set to be approximately 2 to 3% larger than the wall thickness of the cylinder 3 in response to the reduction in the wall thickness, and the inner diameter of the mold 1 may be set to be 2 to 3% larger than the wall thickness of the cylinder 3. The diameter of the cylindrical body 3, which is formed to be slightly larger than the warp diameter and is in a plastic state due to the action of centrifugal force, is slightly expanded, and the diameter of the cylindrical body 3 is expanded to correspond to the amount of thinning caused by the bulging deformation of the disk 4. It is also possible to slightly reduce the wall thickness and make the wall thicknesses of both 3 and 4 uniform.

Furthermore, since the disk 4 and the cylindrical body 3 are in uniform contact with each other in the circumferential direction, it is possible to weld them easily and uniformly. By forming the contacting end surface 32 of the cylindrical body into a wedge-shaped cross section with the outer periphery as the apex, welding becomes easier, and more preferably, as shown in FIG. By interposing the welding ring 5 made of quartz glass in the triangular recessed portion, the welding becomes easier.

According to this embodiment, the above-described effects of the present invention can be smoothly achieved, and since almost the entire area of the inner peripheral side of the cylindrical body 3 and the upper surface of the disk 4 is heated,
Thermal strain and dimensional strain can be removed over the entire area.

That is, according to this embodiment, the disk 4 and the cylindrical body 3
By heating the entire mold 1 and rotating the mold 1 around the central axis C-C' of the cylindrical body 3 during heating, thermal strain and dimensional strain can be removed.
Furthermore, it becomes possible to manufacture a large quartz container in the shape of a hollow cylinder without causing any unevenness in the welded area.

``Effects of the Invention'' As described above, according to the present invention, since the disk 4 and the cylindrical body 3 are welded while they are set in a mold, there is no possibility of misalignment of the welding part, and the skill level is also reduced. There's nothing I need.

Further, according to the present invention, since the welding and the expansion of the disk 4 are performed at the same time, a single heat treatment process is required, which greatly reduces the number of manufacturing steps and prevents thermal strain from occurring between the bottom of the container and the welded area. There's nothing to do.

Furthermore, according to the present invention, the flat bottom of the hollow cylindrical body 3 is formed by bulging below the plastic region, rather than by compression molding of the peripheral edge, and the extent of the bulge is determined by compression molding. Even if the diameter of the container is increased, the bottom side will hardly become thinner, making it possible to provide a quartz container with no problem in terms of strength.

It has various effects such as

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a quartz container according to an embodiment of the present invention showing the state before and after molding, FIG. 2A and FIG.
Figure B is a central vertical cross-sectional view showing the cross-sectional shapes of a cylindrical body and a disk forming a quartz container.

Claims (1)

[Scope of Claims] 1. Inside a cylindrical mold with a curved bottom, a quartz glass disk and a quartz glass cylindrical body having the same outer diameter as the disk are sequentially placed at each other's outer edges. are set in contact with each other so that they form the same circumference, and then by heating, the discs are deformed along the bottom of the curved mold by their own weight and/or physical external force, and at the same time, both discs are heated. A method for manufacturing a large quartz container characterized by heat-sealing components together. 2. The method for manufacturing a large quartz container according to claim 1, wherein the physical external force is a negative pressure generated between a disk set inside the mold and the bottom of the mold. 3. The heating means for heating the disk and the cylindrical body,
The method for manufacturing a large quartz container according to claim 1 or 2, wherein the heating means is arc discharge or a burner. 4. Claims 1 to 3, characterized in that while heating the disk and cylinder, the mold is rotated about the central axis of the cylinder during heating. A method for manufacturing a large quartz container according to any one of the items. 5. The method for manufacturing a large quartz container according to any one of claims 1 to 4, wherein the end surface of the cylindrical body in contact with the disk is formed into a wedge-shaped cross section with the outer periphery as the apex.