JPH0859261A - Production of worked silica glass product - Google Patents

Abstract

PURPOSE: To provide a method for producing a worked silica glass product capable of readily and optionally preparing a perforated worked silica glass product ranging from a small to a large calibers. CONSTITUTION: This method for producing a worked silica glass product is to insert one or plural inner tubes 2, extending a circular or a polygonal cross- sectional shape in the axial direction and made of silica glass into a hollow outer silica glass tube 1 extending an optional cross-sectional shape in the axial direction, prepare a material to be heated, then fill silica powder in at least a part of a gap between the outer tube 1 and the inner tubes 2 in the material to be heated, subsequently thermally melt the material to be heated in the axial direction while controlling the pressure in at least a part between the outer tube 1 and the inner tubes 2 of the material to be heated according to a ring-shaped zone heating method and integrate the outer tube 1 with the inner tubes 2. Thereby, a perforated tube containing one or plural small holes present in the rod is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an invention capable of easily and inexpensively manufacturing a silica glass processed product having a predetermined size by using silica glass as a raw material, for example, an insulating tube for thermocouples and various sensors. The present invention relates to an invention of a silica glass processed product used as a protection tube, a crater of a glass burner, a bubbler tube, a physics and chemistry equipment member, a heat treatment jig material also serving as a gas pipe, a semiconductor heat treatment jig member, and the like.

[0002]

2. Description of the Related Art Conventionally, a silica glass jig having high chemical stability and heat resistance has been used as a semiconductor jig incorporated in a heat treatment apparatus for wafers. All of these require high-purity, high-dimensional accuracy, low-cost manufacturing methods with no quality variations. The burner for processing these jigs or the burner for producing synthetic quartz by the oxyhydrogen flame hydrolysis method is also formed of silica glass, but such a burner blows gas into a large-diameter outer tube. Although a plurality of inner pipes forming the mouth are inserted, it is difficult to weld the inner pipe to the outer pipe airtightly and accurately through the spacing member.

On the other hand, in recent years, in a sensor for detecting temperature, gas concentration, etc. in a high temperature atmosphere, a multi-hole silica glass rod having a large number of axial holes bored in the axial direction is provided in order to improve insulation and heat resistance. Although a sensor device in which the sensor is inserted has been developed, in such a multi-hole silica glass rod for a sensor, in order to prevent noise of a detection signal from the sensor, high purity and high dimensional accuracy without contamination of impurities are provided. Need a rod.

Conventionally, in order to manufacture a multi-hole silica glass tube for such an application, a method of preparing several tubes and then welding and integrating them has been adopted. Therefore, the cost was high.

A bubbling cleaning device used for cleaning silicon wafers and various other members for semiconductor heat treatment jigs, and for bubbling a raw material liquid when manufacturing soot-like synthetic silica glass from a high-purity liquid raw material. In the bubbling vaporizer used, a large diameter outer tube with many inner tubes inserted and a bubbler tube with many small holes perforated by machining a silica glass bar have been developed. However, in such a bubbler tube, the small hole must be formed by welding or machining, and these methods inevitably have the following problems.

[0006]

That is, in the method by machining, a silica glass processed product is manufactured from agglomerated silica glass by cutting, laser processing or the like. However, in this method, since the silica glass is a brittle material, Not only cracks and breaks due to shearing by cutting tend to occur, but also contamination from cutting jigs and the like occurs. Furthermore, the cutting process has a limit on the drill length, and in particular, a long multi-hole silica glass cannot be produced. In addition, in the case of multi-hole silica glass, not only multi-hole silica glass having a fine hole size cannot be produced, but also multi-hole silica glass having various sizes and shapes cannot be continuously produced.

[0007] In order to eliminate such drawbacks, a processing method by a hot molding method or a hot press molding has been proposed. That is, there is also a method of filling silica powder in a mold made of carbon or the like, or putting a lump, and producing a silica glass processed product of a predetermined shape by heat molding or heat pressure molding, but with such a molding method Dimension control cannot be performed accurately. In the case of processed multi-hole silica glass, various dimensions,
Not only is it impossible to continuously form shaped multi-hole silica glass, but problems such as contamination from the furnace occur.

In view of the above technical problems, the present invention provides a processed silica glass product from a silica powder raw material.
An object of the present invention is to provide a method for producing a processed silica glass product having high dimensional accuracy without chipping or cracking. Another object of the present invention is a method for producing a processed silica glass product, in particular, in the case of a multi-hole silica glass processed product, the inner surface of the hole is not roughened, has no scratches, etc., and can be continuously produced. To provide. It is another object of the present invention to provide a method for producing a processed silica glass product, which maintains high purity like raw materials without contamination of impurities in the production process.

Another object of the present invention is to extend axially from a long-hole multi-hole silica glass, a plate having a thickness of several mm to a rod having a length of 10 m and a fiber having a length of several 10 m. It is an object of the present invention to provide a method for producing a silica glass processed product, which can arbitrarily generate an arbitrary profile shape if it has an existing shape.

Another object of the present invention is to provide a method for producing a processed silica glass product capable of easily and arbitrarily producing a processed product of a multi-hole silica glass having a small diameter to a large diameter. Another object of the present invention is, for example, an insulating tube for a thermocouple, a protective tube for various sensors, a crater of a glass burner, a bubbler tube, a physics and chemistry equipment member, a heat treatment jig material also serving as a gas pipe, a semiconductor heat treatment jig member. An object of the present invention is to provide a manufacturing method capable of easily and inexpensively manufacturing a processed silica glass product applied as the above.

[0011]

The invention according to claim 1 is applied to a silica glass processed product (hereinafter referred to as a multi-hole tube) in which one or a plurality of small holes are present in a rod. Where, in the hollow silica glass outer tube with an arbitrary cross-sectional shape extending in the axial direction, one or more silica glass inner tubes with a circular or polygonal cross-sectional shape extending in the axial direction are inserted into a tubular shape. After creating the object to be heated, at least a part of the gap between the outer tube and the inner tube in the object to be heated is filled with silica powder, and then at least one portion between the outer tube and the inner tube of the object to be heated is filled. First, the outer tube and the inner tube are integrated by heating and melting the body to be heated along the axial direction from the tip side by a ring zone zone heating method while controlling the pressure of the part. It is a feature of.

In this case, in order to manufacture a multi-hole tube, the silica powder is filled into the portion of the body to be heated, which is to be filled with silica glass, uniformly in the gap between the outer tube and the inner tube. The second feature is that the outer tube and the inner tube are integrated without a gap by the zone heating.

In this case, the inside of the inner pipe for forming the pipe or the passage is maintained under an open positive pressure, that is, at least one end is kept in an open state under normal pressure or under pressure, while silica powder is filled. The outer tube and the inner tube are preferably melted by heating while being kept under reduced pressure to be integrated. This is the third feature.

In this case, after the powdery material containing amorphous silica powder as a main component is filled from the tip of the gap between the outer tube and the inner tube of the object to be heated, quartz powder or other crystalline silica powder is mainly added. It is preferable that the powdery material as a component is filled and the particle diameter of the crystalline silica is preferably in the range of 10 to 1000 μm, and the content ratio of fine particles of less than 10 μm is 0.1 wt% or less.

The reason for specifying the silica powder in this way is as follows. When amorphous silica powder is uniformly filled in the portion where the silica glass is uniformly filled and zone melting is performed, such amorphous silica powder has no so-called melting point and gradually softens from around 1600 ° C. Since it melts, a deposition gas or the like from the silica powder is caught and a silica glass body in which bubbles remain is formed.

On the other hand, crystalline silica powder such as crystal powder is 1730
Since it has a melting point at ℃, it can be melted all at once by heating it to 1730 ℃ or more, and it is possible to suppress the generation of bubbles in the molten glass as much as possible, but crystalline silica powder such as crystal powder is α type at 573 ℃. To a β-type transition point, the tube is rapidly expanded by the transition from α-type to β-type of the crystal powder inside the tubular heated object before the viscosity of the tubular heated object decreases at the start of heating. The object to be heated is destroyed.

Therefore, according to the present invention, since the powdery body containing the amorphous silica powder having no transition point as a main component is present on the tip side which is first zone-heated, the transition from α type to β type is caused. While preventing the breakage of the existing tube, the viscosity of the hollow tube decreases due to the preheating of the heat zone above it, and the crystalline silica powder in that part undergoes a rapid expansion due to the transition from α type to β type. However, crystalline silica powder such as crystal powder is filled only in the area where the breakage of the tube can be prevented. Incidentally, the filling width of the amorphous silica powder needs to be larger than the heat zone (uniform heating width) of the zone heating means, but if it is too large, the substantial bubble-free area decreases and the productivity becomes low. In order to reduce, it is preferably less than 20% of the total filling amount of powder.

The crystalline silica powder is crystalline silica powder selected from natural quartz powder, synthetic quartz powder and synthetic cristobalite powder and has a particle size of 10 to 1000 μm, preferably 20 to 500 μm, more preferably 50 to 50 μm. Within the range of 200 μm, the content ratio of fine particles of less than 10 μm is 0.1 w
It must be t% or less. Kashidashi, the particle size is 1
If it is less than 0 μm, even if a vacuum is applied, a pressure loss occurs, so that it is not possible to apply a vacuum to the inside of the filling area, and even if the zone melts, it becomes difficult for the bubbles to escape, and the fused silica glass contains a large amount of bubbles. In addition, the heat insulating effect makes it difficult to uniformly heat and melt the central portion of the tubular object. If the particle size is 1000 μm or more, it will not be possible to eliminate the generation of bubbles due to the fact that the particles do not become uniform during melting, and similarly, even if quartz powder is used, the voids between the particles are wide.

Further, the silica powder is charged by first filling the lower end of the powder filling area of the tubular heated object with the amorphous silica powder and then with the mixed powder of the amorphous silica powder and the crystalline silica powder. Finally, it is preferable to fill the crystalline silica powder.

When producing a high-purity rod, it may not be possible to use the natural crystalline silica powder as described above. In such a case, it is preferable that the high-purity synthetic amorphous silica powder is heat-treated in advance in a hydrogen-containing atmosphere or a helium-containing atmosphere and then filled. As a result, even if a residual gas consisting of hydrogen or helium is present during the zone melting, these are occluded / doped in the molten glass during the melting, and it is possible to prevent the generation of bubbles, and a high-purity amorphous material like synthetic silica glass. Even if the silica powder is used, a substantially glass-free silica glass rod can be manufactured.

Further, as the above-mentioned silica powder, silica powder prepared by previously mixing metal or metal element compound powder may be used. In this case, it is preferable that the reduced pressure atmosphere in the powder-filled area during heating and melting is set to a vacuum of 1 KPa or less so that gas entrapment and expansion can be prevented.

The multi-hole bar silica rod of the present invention is
It is applied as an insulating tube for thermocouples, a protective tube for sensors, a sealing member, a glass burner crater, a bubbler tube, a member for physics and chemistry equipment, and a member for semiconductor heat treatment jigs.

[0023]

EXAMPLES Examples of the present invention will now be illustratively described in detail. However, unless otherwise specified, the materials, shapes, analysis values, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto but are merely illustrative examples. .

First, the procedure for manufacturing a multi-hole bar-shaped double-bore tube for a thermocouple will be described with reference to FIGS. (1) Preparation of outer tube made of silica glass, substantially tubular body (hereinafter referred to as inner tube), etc. As shown in FIG. 2, a silica glass outer tube 1 having a diameter of 40 mm, a wall thickness of 1.5 mm, and a length of 1.2 m, and Two inner tubes 2 made of silica glass having a diameter of 15 mm, a wall thickness of 1.5 mm, and a length of 1 m to be inserted thereinto were prepared. Also, diameter 40m
m, a disk-shaped silica glass plate (bottom plate 3) with a machining dimensional accuracy of ± 0.1 mm in which two holes 3a having a diameter of 15 mm are symmetrically formed in the center, and a gas vent hole 5a is formed in the center with the same outer diameter. Silica glass plate (gas vent cover plate 5) and diameter of 37
mm, and two holes 6b having a diameter of 15 mm were symmetrically formed in the center, and one silica glass plate (middle plate 6) provided with gas vent holes 6a on both upper and lower sides was prepared.

(2) Processing of the outer pipe and the inner pipe As shown in FIG. 1 (A), each inner pipe 2 to be inserted inside
One end 2a of the inner tube 2 is sealed, and
After the side b is fitted into the hole 3a of the bottom plate 3, the bottom plate 3 is welded with the open end 2b open.

Next, as shown in FIG. 1 (B), after the intermediate plate 6 is attached near the closed end on the sealing end side of the inner tube 2, FIG.
As shown in FIG. 3, the inner plate 6 is inserted into the outer tube 1 from the mounting side, and the periphery of the bottom plate 3 located on the terminal side thereof and the end of the outer tube 1 are hermetically welded and fixed. Finally, as shown in FIG. 1D, the gas vent cover plate 5 is airtightly welded and fixed to the upper end of the outer tube 1. As a result, the inner tube 2 end 2a in the outer tube 1 is sealed, and the other end 2b side of the inner tube 2 is opened on the bottom plate 3 of the outer tube 1. Therefore, the inner tube 2 can be maintained under a positive pressure even when the pressure reduction process is performed through the gas vent hole 5a of the lid plate 5.

(3) Thermal strain removal treatment of the heated body 10 The heated body 10 formed as described above is heated by a heater 105.
Heat treatment is performed at 0 ° C for 10 hours to remove thermal strain, and then the object to be heated is immersed in a 10 wt% hydrogen fluoride aqueous solution for 10 minutes to wash and remove microcracks, and then dried in a clean atmosphere. I did.

(4) Preparation of main raw material silica powder and heat purification treatment The silica powder is selected from natural quartz, synthetic quartz, synthetic cristobalite and synthetic silica glass.
The heating purification treatment is performed in an atmosphere containing chlorine gas, hydrogen chloride gas, etc. When the amorphous silica powder is used, the heating purification treatment is preferably performed in a hydrogen containing atmosphere or a helium containing atmosphere. The particle size of silica powder is 10 to 1000μ.
m is preferred. Below this, a large amount of bubbles are contained in the fused silica glass body 3. If the amount is higher than this, it will not be uniform when melted, and likewise bubbles will be hard to escape.

Therefore, in this embodiment, as the main raw material crystalline silica powder, natural quartz powder was adjusted to have a particle size in the range of 50 to 500 μm and less than 10 μm to 0.1 wt% or less.
If necessary, in order to increase heat resistance and the like, metal element compound powder and the like may be mixed after the purification treatment, in which case the concentration of the specific doping element of the silica glass rod after production is 0.1 to 5 wt. It is preferable to set the mixing ratio of the dope powder and the main raw material silica powder so as to be 100%.

(5) Preparation of Synthetic Silica Glass Powder A synthetic silica glass powder produced by the sol-gel method has a particle size of 50 to 50.
It was adjusted to 500 μm.

(6) Filling and filling of silica glass powder into the heated body When crystalline silica is used as the main raw material silica powder, synthetic silica glass powder 7a is put into the lower end of the non-heated body, and then gradually. Add powder with a high ratio of crystal powder such as crystal powder to. The filling length of the silica glass powder 7a at the lower end must be larger than the soaking length of the heater 8 used for melting. The reason for this is that when silica glass powder 7a is not put in the tip portion but crystal powder 7b is suddenly put in and the temperature is raised by the heater 8, it rapidly expands at the α-type β-type transition temperature of the crystal and the outer tube Because it destroys 1. If all of the main raw material powder is amorphous silica glass,
The silica glass powder 7 of the same type may be sequentially filled from the tip.

Therefore, in this embodiment, as shown in FIGS. 3 (A) and 3 (B), 50 g of synthetic silica glass is first introduced from the gas vent hole 5a of the cover plate 5 through the notch 6a of the intermediate plate 6. Powder 7a is charged, then 50 g of mixed powder 7a ₁ of natural crystal: synthetic silica glass = 1: 2 (weight ratio), and further mixed powder 7a of natural crystal: synthetic silica glass = 1: 1. 50 g of ₂ was added, and further 50 g of mixed powder 7a ₃ of natural crystal: synthetic silica glass = 2: 1 was added.
Finally, 500 g of natural crystal powder 7b was filled. As a result, the synthetic silica glass powder layer 7a is 6 cm, and the mixed powder 7a is
₁ , the layers of the mixed powder 7a ₂ and the mixed powder 7a ₃ are 6 cm, respectively, and the cumulative total of these layers is the soaking length (5 cm) of the heater 8.
I was able to make it bigger.

(7) Melt transparent vitrification using heater 8 Next, as shown in FIG.
After the area inside the inner tube 2 and the outer tube 1 filled with silica powder is evacuated to 10 Torr or less from the (cylindrical portion), the heated body 10 including the inner tube 2 and the outer tube 1 is slowly moved. While being inserted into the heater 8 from above the heater 8, the feeding speed into the heater 8 and the drawing speed of the silica glass melted by the heater 8 are controlled to perform zone melting and wire drawing to form a transparent rod-shaped member. Obtain the double-hore tube 9.

At this time, since the internal pressure of the inner tube 2 inserted into the outer tube 1 is open to the atmosphere or positive pressure, it is larger than that in the powdery material filling region under reduced pressure, and the hole of the inner tube 2 melts. Will never close. Further, since the positive pressure is released, the internal pressure of the inner tube 2 does not increase unnecessarily even by heating, and the heating and melting are performed while maintaining the accurate dimensional accuracy.
The diameter of the bore tube 9 is 1 / the diameter of the heated body 10.
It is preferable that the number is 2 or less. In the present embodiment, by adjusting the feed rate of the heated body 10 into the heater 8 and the pulling rate of the vitrified double-hore tube 9, a large number of outer diameter φ10 mm and inner diameter φ3 mm can be obtained. A double-bore tube for a thermocouple was prepared.

(8) Evaluation of physical properties The double-bore tube 9 manufactured as described above has 10 bubbles.
The total area of bubbles present at 0 cm ³ was 0.88 mm ² . (However, the measuring method is DIN 58927 (1970)
Follow This is the applicant's product for use in semiconductor jigs:
It is at the same level as Heralux-E, and it can be said that substantially no bubbles are generated. Next, the dimensional accuracy of each of the double bore pipes 9 manufactured as described above has an outer diameter of 10 m.
m, inner diameter 3 mm, outer diameter radial runout tolerance ± 0.1 (mm) outer diameter radial full runout tolerance ± 0.2 (mm), inner diameter radial runout tolerance ± 0.03 ( mm) and the inner circumference radial direction runout tolerance of ± 0.06 (mm), which enables accurate machining. Further, the surface condition was very smooth without scratches.

In the impurity analysis, Table 1 shows the natural crystal powder before melting and the impurity concentration after melting and transparent vitrification.

[0037]

[Table 1]

From this table, it is understood that the high purity of the raw material powder is well preserved even after vitrification. Incidentally, Li, M
g and Ti are measured by ICP mass spectrometry, and Na, K and C
A, Cr, Fe, Ni, and Cu were measured by a graphite furnace heating atomic absorption spectrometry.

Example 2 A double bore tube was prepared in the same manner as in Example 1. (1) Preparation of Outer Tube 1 and Inner Tube 2 Made of Silica Glass As shown in FIG. 5, an inner tube 2 and an outer tube 1 each having a diameter of 40 mm and a wall thickness of 1.5 mm are prepared as in the above embodiment. In the case of this embodiment, the inner tube 2 is made longer than the outer tube 1. Further, as shown in FIG. 5, the bottom plate 3 is the same as that of the above-mentioned embodiment, but the middle plate 6 is not provided and the hole 5b having a diameter of 15 mm is symmetrically formed in the center.
Along with the opening, one degassing lid plate 5 having a degassing hole 5a on the lower side was prepared.

(2) Processing of the silica glass heated body 10 As shown in FIG. 6 (A), after the opening end 2b side of the other end of the inner tube 2 is fitted in the hole of the bottom plate 3, the opening end 2b is formed. Is welded to the bottom plate 3 in the open state. Next, as shown in FIG. 6 (B), after fixing the cover plate 5 to the inner pipe 2 corresponding to the length of the outer pipe 1, the lid plate 5 is inserted into the outer pipe 1 from the mounting side, and the end plate is attached to the end side. The periphery of the positioned bottom plate 3 and the end of the outer tube 1 are air-tightly welded and fixed. Finally, as shown in FIG. 6 (C), the cover plate 5 is airtightly welded and fixed in a state in which the inner pipe 2 is projected on the outer pipe 1. As a result, the inner pipe 2 is projected above the outer pipe 1 from the lid plate 5, and the other end 2b side of the inner pipe 2 is opened on the bottom plate 3 of the outer pipe 1, so that the lid plate 5 Even if the pressure reduction process is performed through the gas vent hole 5a, the inner pipe 2 can be maintained under a positive pressure. After the processing, the thermal strain removal treatment of the silica glass heated body 10 is performed as in the above-described embodiment.

(3) Atmospheric heat treatment of high-purity synthetic silica glass powder Synthetic silica glass powder produced by the sol-gel method has a particle size of 50 to 50.
It was adjusted to 500 μm. Atmosphere of tungsten mesh heater and stainless steel jacket In an electric heating furnace, heat treatment was performed at 800 ° C. for 3 hours in an H ₂ gas atmosphere.

(4) Filling and filling of silica glass powder into the object to be heated 10 Since amorphous silica glass is used as the main raw material powder, silica glass powder 2 of the same type is sequentially filled from the tip. Just do it.

(5) Molten transparent vitrification using heater 8 As shown in FIG. 7, silica powder is filled between the inner tube 2 and the outer tube 1 through the gas vent hole 5a of the flange as in the above-mentioned embodiment. In a state in which the inside of the above area is evacuated to 10 Torr or less and the inner tube 2 is maintained at a higher pressure, for example, a positive pressure,
Zone melting and wire drawing were carried out in the same manner as in the above example,
A transparent rod-shaped double-hore tube 9 is obtained. At this time, the internal pressure of the inner tube 2 inserted inside is larger than that in the powdery material filling region under reduced pressure, and the hole of the inner tube 2 is not closed by melting, so that a predetermined dimensional accuracy can be maintained. Although high-purity synthetic silica was used for the silica powder to be filled, the silica glass heated body 10 and the like, the physical properties of the double bore tube produced were the same as in Example 1, and the results of impurity analysis are shown in Table 2. Shown in.
It can be seen from this table that the high purity of the raw material powder is maintained well even after vitrification.

[0044]

[Table 2]

According to such an embodiment, for example, FIG.
It is also possible to manufacture a multi-hole rod 12 having a large diameter as shown in FIG. The arrangement cross-sectional shape of the inner pipe 2 can be arbitrarily set as shown in (B). Furthermore, since the inner tube 2 is maintained under open positive pressure, it is possible to perform zone heating while maintaining the shape with high accuracy. For example, as shown in (C), fabrication of a square multi-hole rod 13 is made. Is also possible.

Further, by changing the drawing speed, it is possible to manufacture a tapered multi-hole rod.

[0047]

As described above, according to the present invention, when a silica glass processed product is prepared from a silica glass raw material, it is possible to obtain a silica glass processed product with high dimensional accuracy without chipping or cracking. In addition, according to the present invention, it is possible to obtain a processed silica glass product, particularly a multi-hole silica glass processed product, which has no roughness or scratches on the inner surface of the hole and which can be continuously manufactured. I can. According to the present invention, it is possible to obtain a processed silica glass product in which high purity is maintained similarly to the raw material without causing contamination of impurities in the manufacturing process. According to the present invention, a long-length multi-hole silica glass, a plate having a thickness of several mm, a rod having a length of 10 m, or a fiber having a length of several tens of m may have a shape extending in the axial direction. For example, any profile shape can be generated arbitrarily. According to the present invention, a multi-hole silica glass processed product having a small diameter to a large diameter can be easily and arbitrarily prepared. INDUSTRIAL APPLICABILITY According to the present invention, for example, it is used as an insulating tube for thermocouples, a protective tube for various sensors, a crater of a glass burner, a bubbler tube, a member of physics and chemistry equipment, a jig material for heat treatment also serving as a gas pipe, a member for semiconductor industry, etc. It is possible to easily and inexpensively obtain processed silica glass products.

[Brief description of drawings]

1 (A), (B), (C) and (D) show manufacturing steps for manufacturing a heated body from the materials shown in FIG.

FIG. 2 shows materials shown in a silica glass heated object according to an example of the present invention.

FIG. 3 shows a state of charging and filling silica glass powder into a heated body.

FIG. 4 shows a melting transparent vitrification process using a heater.

FIG. 5 shows materials shown in a silica glass heated body according to a second embodiment of the present invention.

6 (A), (B) and (C) show manufacturing steps for manufacturing a heated body from the material shown in FIG.

FIG. 7 shows a transparent vitrification process using a heater.

FIG. 8A shows a large-diameter multi-hole rod manufactured according to the present invention, and FIG. 8B shows various examples of its cross-sectional shape.
(C) is a square multi-hole rod manufactured according to the present invention.

[Explanation of symbols]

 1 Outer Tube 2 Inner Tube 3 Bottom Plate 5 Lid Plate 6 Middle Plate 7 Raw Silica Powder 7a Amorphous Silica Powder 7b Quartz Powder 8 Heater 10 Heated Object

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masanori Suzuki 88 Kawakubo, Kanaya, Tamura-cho, Koriyama-shi, Fukushima Shin-Etsu Quartz Co., Ltd.

Claims (4)

[Claims] 1. A tubular shape in which one or more silica glass inner tubes having a circular or polygonal cross-sectional shape extending in the axial direction are inserted into a hollow silica glass outer tube having an arbitrary cross-sectional shape extending in the axial direction. After creating the object to be heated, at least a part of the gap between the outer tube and the inner tube in the object to be heated is filled with silica powder, and at least a part between the outer tube and the inner tube of the object to be heated is filled. A method for producing a processed silica glass product, characterized in that the body to be heated is melted and integrated along the axial direction by zone heating from the tip side while controlling the pressure. 2. The tip of the object to be heated is controlled under a reduced pressure between the outer tube and the inner tube of the object to be heated filled with the silica powder, or under normal pressure or under pressure inside the inner tube. The method for producing a silica glass processed product according to claim 1, wherein the process is performed by heating from the side along the axial direction by zone heating to melt and stretch and integrate. 3. A powdery material having an amorphous silica powder as a main component is filled from the tip of a gap between the inner tube and the outer tube of the object to be heated, and then quartz powder or other crystalline silica powder is used as a main component. And the crystalline silica has a particle size of 10 to 1
The method for producing a silica glass processed product according to claim 1, wherein the content ratio of fine particles in the range of 000 μm and less than 10 μm is 0.1 wt% or less. 4. The reduced pressure atmosphere in the powdery filling area is 1 KPa.
The method for producing a silica glass processed product according to claim 1, wherein the following vacuum is applied.