CN117602815A - Powder rod heating vitrification device and method - Google Patents

Abstract

The invention provides a powder rod heating vitrification device and method, comprising a rod feeding device, a glass muffle tube and a heating furnace body arranged in the glass muffle tube, wherein the upper end of the heating furnace body is connected through a hanging piece, the hanging piece is clamped by an up-down moving mechanism, the upper end of the powder rod and the upper end of the hanging piece extend out of a sealing cover plate arranged at the upper end of the glass muffle tube and are in sealing arrangement through a sealing part, an induction heating coil is arranged at the periphery of the glass muffle tube corresponding to the heating body, and the induction heating coil can move up and down relative to the glass muffle tube. The heating induction coil and the heating body can synchronously move and also can independently move, so that the problems that a hot zone cannot be finely controlled during powder rod sintering, and the powder rod cannot be burned thoroughly or the shoulder is elongated after sintering are well solved, the control of the hot zone range is very accurate, and the sintering quality of a silicon dioxide powder rod target rod end is obviously improved. Thus, a high purity glass body can be produced.

Description

Powder rod heating vitrification device and method

Technical Field

The invention belongs to the optical fiber manufacturing technology, and particularly relates to a powder rod heating vitrification device and method.

Background

Due to the needs of the optical fiber and semiconductor industry, it is becoming increasingly important to develop equipment capable of producing high purity quartz glass bodies. Many methods of making the above products have been published.

For example: the silica powder rod (hereinafter referred to as powder rod) is obtained by VAD or OVD process, then the temperature is raised to about 1200 ℃ under sealed environment, chlorine is introduced to purify the powder rod, and finally the powder rod is sintered into quartz glass body when the temperature is raised to about 1500 ℃.

The main description here is a sintering device for converting a powder rod into a quartz glass body.

Publication EP-A-170,249 describes a sintering furnace. The vertical tubular furnace comprises a cylindrical muffle tube, wherein fused quartz is arranged at two ends of an alumina material used in the middle of the muffle tube, and the muffle tube is manufactured by welding through a special high-temperature process. At the periphery of the alumina glass is a heating unit, which heats by conduction and radiation. The powder rod is purified inside the muffle tube by raising or lowering it through a central hot zone in a chlorine-and helium-containing gas. Finally, the powder rod is progressively sintered by slowly passing through a hot zone at a rate of a few centimeters per minute, which is higher than the purification temperature.

EP-A-170,249 describes such a muffle furnace suggesting that alumina is a suitable material for the muffle tube, which can withstand high temperatures above 1500 ℃, but if the furnace temperature falls below 500 ℃, the alumina muffle tube will crack, which requires the furnace to maintain a safe temperature above 800 ℃ for a long period of time, which does not meet the current energy-saving and consumption-reducing large environment; the alumina muffle tube in the high-temperature environment cannot sinter the powder rod under the condition of near vacuum, and the glass body sintered under the relative pressure contains more bubbles, and the bubbles are formed by air originally sealed among powder particles. The glass rod produced from such a muffle tube requires a long high temperature anneal to eliminate these bubbles within the rod. The sintering furnace has the defect that the vitrification process at the shoulder reducing position of the powder rod is not controlled finely enough, and the two conditions of over-sintering and insufficient sintering often occur at the shoulder reducing position of the powder rod.

A vacuum sintering furnace is described in Japanese published patent CN-1035990C of China application. The vacuum furnace consists of a front cavity and a furnace body. The front cavity is a metal shell, is arranged above the furnace body, and is connected with the furnace body through a gate valve; the furnace body is innermost is the muffle tube that high-purity carbon was made, and the outside of muffle tube surrounds the heater, and the heater periphery is graphite thermal-insulated shell, and graphite thermal-insulated shell skin is the metal cavity.

In an example of a heated vitrification of such a vacuum sintering furnace described in CN-1035990C, it is mentioned that a powder rod is first placed in a front cavity, the front cavity is evacuated to a near vacuum state, and then a gate valve between the front cavity and a furnace body is opened (the furnace body is always in a near vacuum state); the powder rod is lowered into the furnace body through the connecting rod, the furnace body is heated in stages, so that the powder rod is firstly densified and contracted, and finally vitrification is completed through integral sintering. The inner part of the glass rod body sintered by the vacuum furnace contains almost no bubbles. It is known from the description of the vacuum furnace in this patent that such a vacuum sintering furnace is not suitable for dehydrating powder rods by introducing chlorine into the furnace body. Hypochlorous acid generated by dehydration can lead to the oxidation of carbon materials to be intensified, and can generate corrosion effects on a metal shell of a vacuum furnace, a metal vacuum pipeline and a vacuum pump rotor, and the phenomena have great influence on manufacturing high-purity glass rods. And the sintering furnace is also not fine enough in temperature control on the diameter-changing position of the shoulder part of the powder rod, and two conditions of over-sintering or insufficient sintering often occur on the diameter-changing position of the shoulder part of the powder rod.

It is known from the vacuum sintering furnace described in CN-1035990C that if a larger size powder rod is to be sintered, the vacuum furnace must be designed with a larger furnace body, and then a large amount of high purity graphite material is used to completely surround the powder rod and to sinter it integrally; larger sizes of graphite insulation are also required to encapsulate the hot zone to ensure that the metal shell does not overheat. The design of using graphite materials in large quantities is extremely expensive and causes great trouble for maintenance and replacement of later-stage graphite pieces.

Published U.S. patent WO 93-2341 mentions a powder rod sintering apparatus. It is composed of three units of pretreatment furnace A, sintering furnace B and cooling chamber C. Pretreatment furnace A structure: the innermost layer is a hollow cylindrical tube (called as graphite tube for short) composed of high-purity graphite tubes with the size larger than that of the powder rod; the outer layer of the graphite tube is a heat insulator made of high-purity graphite felt; the outer layer of the heat insulator is a fused quartz tube, which is also a vacuum shell; the outermost layer is a water-cooled coil induction coil which surrounds the entire fused silica tube. The pretreatment furnace is used for dewatering or doping the powder rod after heating. The sintering furnace B and the pretreatment furnace A are separated by a gate valve, and the gate valve is closed when the pretreatment furnace A dehydrates or dopes the powder rod.

The structure of the sintering furnace B is substantially the same as the pretreatment furnace a, except that the length of the sintering furnace B is only a fraction of that of the pretreatment furnace a, and the size is not provided in the patent, and only the sintering furnace B is described as a short hot zone. The temperature of the sintering furnace B is raised after dehydration or doping of the pretreatment furnace A is finished, then a gate valve is opened, a vacuum pump system pumps up the A, B, C units to a state close to vacuum, and then a powder rod is driven by a connecting rod to slowly descend and rotates to be vitrified through the sintering furnace B.

The cooling chamber C is arranged below the sintering furnace B, a water-cooling metal flange is arranged between the cooling chamber C and the sintering furnace B, and the powder rod is vitrified and then directly enters the cooling chamber C for cooling. The cooling chamber C has a simple design, the outermost layer being a water-cooled metal chamber, the inner face being an inner chamber made of high purity graphite, between which a thermal insulation layer is again provided by means of a graphite felt.

The design of the patent is very special, and the temperature of the furnace body can be raised and lowered at will at normal temperature and high temperature; the powder rod can be dehydrated and doped, and can be sintered and vitrified in a vacuum environment. It still has the disadvantages: 1. the patent mentions that the furnace body gate valve, the metal flange and the water-cooling shaft are made of alloy which is sufficiently corrosion-resistant, and the furnace body gate valve, the metal flange and the water-cooling shaft are protected by heat insulation, radiation shielding, water cooling and the like, otherwise, the problems of water seepage, corrosion and the like can occur, and the product quality is affected. 2. The three units of the equipment A, B, C are at least two powder rod lengths and at least two powder rod lengths, so that the equipment A, B, C is large in requirement on high-purity graphite pieces, expensive in price and complicated in maintenance and replacement of the graphite pieces. 3. The sintering furnace is also not fine enough in temperature control at the reducing position of the shoulder of the powder rod.

Disclosure of Invention

The invention aims to provide a powder rod heating vitrification device and method capable of improving the temperature of a split shoulder reducing area and the sintering quality.

The invention is realized in the following way:

the invention provides a powder rod heating vitrification device which comprises a rod feeding device, a glass muffle tube and a heating furnace body arranged in the glass muffle tube, wherein the upper end of the powder rod is clamped by the rod feeding device, the rod feeding device is used for realizing up-and-down movement and rotation of the powder rod in the heating furnace body, a process air inlet is arranged at the bottom of the glass muffle tube, and an air outlet is arranged at the upper part of the glass muffle tube.

According to the technical scheme, the heating furnace body comprises a heating body arranged in a furnace shell, a peripheral heat insulation layer is arranged on the periphery of the heating body, an upper heat insulation layer and a lower heat insulation layer are respectively arranged at the upper end and the lower end of the heating body, and the hanging piece is connected with the furnace shell through a furnace body connecting plate.

According to the technical scheme, the thickness of the heating element is as follows: 4mm-8mm; the height is 500-600mm; the induction coil height was 400mm.

According to the technical scheme, the infrared temperature measuring probe is arranged outside the heating body, and the temperature measuring hole is arranged in the heating body corresponding to the infrared temperature measuring probe.

According to the technical scheme, the thickness of the peripheral heat insulation layer is 50mm to 70mm, and the thicknesses of the upper heat insulation layer and the lower heat insulation layer are respectively as follows: 55mm to 75mm.

According to the technical scheme, the distance between the heating element, the heat insulation layer and the glass muffle tube is as follows: 10-20mm.

According to the technical scheme, the heating element is made of pure graphite material, the peripheral heat insulation layer is a graphite soft felt, and the upper heat insulation felt and the lower heat insulation felt are both graphite hard felt.

According to the technical scheme, send excellent device to link to each other through bearing the weight of couple and bearing the support including bearing the weight of couple, the upper end of powder stick, it can realize the reciprocating and the rotation of powder stick, the upper end of bearing the weight of the couple is connected the connective bar, the connective bar wears out outside the sealed apron and links to each other with bearing the weight of the support, it can realize the reciprocating of powder stick to bear the weight of the support.

A powder rod heating vitrification method is characterized in that,

step one, providing the powder rod heating vitrification device;

step two, controlling the heating body to move to the lower cone part of the powder rod, starting to introduce process gas, and closing a pipeline valve leading to the vacuum pump when the process gas is introduced for pretreatment;

step three, the induction heating coil starts to heat a heating body, the temperature measuring probe feeds back the temperature in the furnace, the sealing part seals the furnace body, the induction heating coil and the heating body synchronously move upwards, and the powder rod is preprocessed;

and step four, after the pretreatment is finished, the induction heating coil and the heating body return to the initial positions, the temperature is raised to the set temperature, the vacuum pipeline valve of the exhaust port is opened, the valve of the waste gas pipeline is closed, the glass muffle tube is pumped to a vacuum state, the movement of the heating body is repeated, and the sintering of the powder rod is started.

The beneficial effects of the invention are as follows: the invention provides

The invention has the beneficial effects that:

1. the heating induction coil and the heating body can synchronously move and also can independently move, so that the problems that a hot zone cannot be finely controlled during powder rod sintering, and the powder rod is not burned or is elongated after shoulder sintering are well solved. When the powder rod is sintered into tail sound, the heating body stops moving at the shoulder position of the powder rod, and the induction coil continues to move upwards slowly, so that the high-temperature heat-insulating material is used for narrowing the heating body, the powder rod can be thoroughly burnt out, the target rod cannot be heated and lengthened, the hot area range is controlled very accurately, the sintering quality of the target rod end of the silicon dioxide powder rod is improved obviously, and therefore, the high-purity glass body can be prepared.

2. According to the product requirement, the invention can introduce chloridizing or fluorizing gas under normal pressure or reduced pressure to pretreat the silicon dioxide powder rod, and can sinter the silicon dioxide powder rod under normal pressure or reduced pressure, and the whole process of pretreat and sinter is not polluted by any impurity

3. Because the sealing means is a big test under the high temperature condition, the process gas inlet, the process gas outlet and the vacuum exhaust port are far away from the heating area, so that the sealing is easy, and the structural design is simpler and more reliable.

4. The invention uses a small amount of high-purity graphite material, greatly saves the cost of high-purity graphite spare parts and is simple and convenient to maintain.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a side sectional view of a powder rod heating vitrification device provided in an embodiment of the present invention.

Fig. 2 is a side sectional view of a heating furnace body according to an embodiment of the present invention.

Fig. 3 and fig. 4 are schematic diagrams of a structure for thoroughly burning out a powder rod according to an embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present invention, it should be noted that, directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or those that are conventionally put in use of the product of the application, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific direction, be configured and operated in a specific direction, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal," "vertical," "overhang," and the like do not denote a requirement that the component be absolutely horizontal or overhang, but rather may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

The features and capabilities of the present invention are described in further detail below in connection with the examples.

As shown in fig. 1 and 2, this embodiment provides a powder rod heating and vitrification device, which includes a rod feeding device, a glass muffle tube 7, and a heating furnace body 8 disposed inside the glass muffle tube 7, wherein the height of the glass muffle tube 7 is preferably more than twice that of a powder rod. The upper end of the powder rod 6 is clamped by a rod feeding device, the rod feeding device is used for realizing the up-and-down movement and rotation of the powder rod in the heating furnace body, a process air inlet 18 is arranged at the bottom of the glass muffle tube, an air outlet 17 is arranged at the upper part of the glass muffle tube, the upper end of the heating furnace body 8 is connected by a hanging piece, the upper end of the hanging piece is clamped by a vertical movement mechanism 1, the up-and-down movement of the heating furnace body can be realized, a sealing cover plate 3 is arranged at the upper part of the glass muffle tube 7, and the target rod and the hanging frame penetrate through the outside of the sealing cover plate 3 and are configured by a sealing part 4. An induction heating coil 10 is arranged at the periphery of the glass muffle tube 7 corresponding to the heating body, and the induction heating coil 10 can move up and down relative to the glass muffle tube 7. The induction heating coil 10 can be fixed on a screw rod so as to realize up-and-down movement, and the induction heating coil 10 and the heating furnace body where the heating furnace body 14 is positioned can move independently or synchronously under the control of a program, so that the temperature required by the process can be provided. An infrared temperature measuring probe 9 is arranged outside the heating furnace body 8, and a temperature measuring hole is arranged in the heating body corresponding to the infrared temperature measuring probe. After one infrared temperature measurement, the furnace temperature can be controlled by power in the follow-up process, so that the furnace temperature can be more stable.

In this example, send excellent device to include and bear couple 5 and bear support 2, the upper end of powder stick 6 links to each other through bearing couple 5, and it can realize the reciprocates and the rotation of powder stick, the upper end of bearing couple 5 is connected the connective bar, the connective bar wears out sealing member and links to each other with bearing support 2 outward, bear support 2 can realize the reciprocate of powder stick.

In order to ensure that the heating furnace body 8 heats the powder rod and avoid the glass muffle tube 7 from being deformed due to heat, the heating furnace body 8 is designed to be heat-insulating, as shown in fig. 2, the heating furnace body 8 comprises a heating body 14 arranged in a lower furnace shell 13, the heating coil 10 heats the heating body 14, and the heating body 14 conducts heat to the powder rod. The periphery of the heating body 14 is provided with a peripheral heat insulation layer 15, the upper and lower ends of the heating body are respectively provided with an upper heat insulation layer 12 and a lower heat insulation layer 16, and the lower furnace shell 13 is connected with the upper furnace shell of the furnace body connecting plate 11. Wherein the furnace shell 13 is made of high-purity quartz or ceramic material, and the hanging frame is made of silicon carbide or other ceramic materials.

In this example, since the heating element 14 is closest to the powder rod, the heating element 14 is made of high-purity graphite material, and the thickness of the heating element is 5mm (without an external heat insulation layer); the height is 550mm; the induction coil height was 400mm. The peripheral heat insulation layer is a graphite soft felt, and the upper heat insulation felt and the lower heat insulation felt are both graphite hard felts. The thickness of the peripheral heat insulation layer is 60mm, and the thicknesses of the upper heat insulation layer and the lower heat insulation layer are respectively as follows: 60mm.

The embodiment also provides a powder rod heating and vitrification method,

step one, providing the powder rod heating vitrification device; the powder rod 6 is placed on the bearing hook 5, the powder rod is sent into the glass muffle tube 7 by utilizing the bearing bracket 2, and meanwhile, the sealing cover plate 3 is synchronously pressed on the flange surface of the glass muffle tube 7, wherein the sealing cover plate is in concentric circle design, and the heating body frame can be kept motionless when the bearing hook moves up and down.

Step two, after the heating furnace body 8 and the coil support 1 move to the lower cone part of the powder rod, process gas starts to be introduced, the exhaust port is of a three-way structure, and when the process gas is introduced for pretreatment, a pipeline valve leading to a vacuum pump is closed.

And thirdly, heating the heating furnace body 8 by the induction heating coil 10, feeding back the temperature in the furnace by the temperature measuring probe 9, and sealing the furnace body, the coil bracket 1 and the powder rod bearing bracket 2 by the sealing component 4. The induction heating coil 10 and the heating furnace body 8 synchronously move upwards to perform pretreatment on the powder rod;

and step four, after the pretreatment is finished, the induction heating coil 10 and the heating furnace body 8 return to the initial positions, the temperature is raised to 1500 ℃, the vacuum pipeline valve of the exhaust port is opened, the valve of the waste gas pipeline is closed, the fused quartz muffle tube is pumped to a vacuum state, the movement of the heating unit is repeated, and the sintering of the powder rod is started. Because of the protection of the heat insulation material, when the temperature of the heating furnace body 8 is increased to 1500 ℃, the temperature of heat conduction to the glass muffle tube 7 is not more than 500 ℃. When the glass muffle tube 7 is vacuumized, the muffle tube 7 cannot deform.

The beneficial effects of the invention are as follows:

1. it is well known that either VAD or OVD processes require a target rod for their deposition. The greatest effect of the target rod is that the transfer is convenient, and any transfer tool does not need to contact the powder rod. After the powder rod is sintered, a complete target rod can also play a role in other working procedures, such as stretching or wire drawing, so that the production cost is well saved. However, in order to burn out as much of the powder rod shoulder as possible during sintering, the powder rod shoulder is made as deep as possible into the high Wen Reou, which also makes the target rod subjected to high temperatures and makes the target rod elongated and thin, which is dangerous during transportation or in the subsequent process. All three sintering patents described above have the problem that the hot zone cannot be finely controlled during sintering of the powder rod, so that the powder rod is not burned thoroughly or the powder rod stretches after shoulder sintering. The induction heating coil and the heating furnace body can synchronously move or independently move, so that the problem is well solved. When the powder rod is sintered into tail sound, the heating body stops moving at the shoulder position of the powder rod, and the induction coil continues to move upwards slowly, so that the heating body is extended to be a heat-insulating material, and therefore a high-temperature region can be narrowed, the powder rod can be thoroughly burnt, and the target rod cannot be heated and lengthened. See fig. 3 and 4.

2. Highly pure graphite materials are rarely used. Because the silicon dioxide powder rod needs to be dehydrated by chlorine, the high-purity graphite material is somewhat degraded and oxidized by dehydrated products (hypochlorous acid) to generate loss. Compared with other prior art, a large amount of high-purity graphite materials are used in the furnace, the maintenance and replacement of the high-purity graphite materials are troublesome, and the high-purity graphite materials used in the invention are very few. Therefore, in mass production, spare part cost can be greatly saved, and maintenance difficulty can be reduced. In addition, because of the protection of the heat insulation material, when the temperature of the heated body 8 rises to 1500 ℃, the temperature of the heat conduction to the glass muffle tube 7 does not exceed 500 ℃. Muffle tubes are used for introducing fluorinated gases (such as SiF) at high temperature ₄ ) The high-purity quartz muffle tube can not devitrify or crystallize.

3. The powder rod can be pretreated or sintered under normal pressure and reduced pressure, cl, siF4, he and other gases can be introduced during pretreatment, and the vitrification of the powder rod can be completed under reduced pressure by introducing the gases during sintering, so that the whole pretreatment and sintering processes are not polluted by any impurity.

Specific application example 1: dewatering

Step 1: after the powder rod enters the quartz glass muffle tube, the induction coil and the graphite heating body at the bottom start to heat up to 1200 ℃.

Step 2: after the temperature of the heating body is raised to 1200 ℃, cl 3L/min and He 3L/min are introduced, and the opening of a valve of a gas outlet is controlled, so that the pressure in the muffle tube is kept at the relative pressure of 2000pa.

Step 3: the induction coil and the graphite heating body synchronously move upwards at the speed of 3mm/min until the shoulder of the powder rod stops.

Step 4: the temperature of the heating element is raised to 1500 ℃, the process gas inlet is closed, and the gas supply is stopped. Vacuum was started and the muffle tube pressure was controlled to <0.5 torr.

Step 5: the induction coil and the graphite heating body synchronously move downwards at the speed of 3mm/min until the lower cone part of the powder rod stops.

Step 6: cooling to room temperature, and providing the glass rod.

The obtained product is transparent and bubble-free, and the hydroxyl content is lower than 0.1ppm. In the actual step 2, the pressure of the muffle tube in the step 2 is controlled to be 100 Torr by controlling the mass of the gas and starting the vacuumizing, so that a good dehydration effect can be achieved.

Specific application example 2: dehydration + fluorine doping

Step 1: after the powder rod enters the quartz glass muffle tube, the induction coil and the graphite heating body at the bottom start to heat up to 1200 ℃.

Step 2: after the temperature of the heating body is raised to 1200 ℃, vacuumizing is started, 50mol% of Cl and 50mol% of He are introduced, and the pressure in the equine fluoride tube is controlled at 100 Torr by controlling the mass of the introduced gas.

Step 3: the induction coil and the graphite heating body synchronously move upwards at the speed of 3mm/min until the shoulder of the powder rod stops.

Step 4: heating the heating element to 1300 ℃, stopping introducing Cl, and starting introducing SiF ₄ 40mol% and 60mol% of He, and the pressure in the equine fluoride tube was controlled at 100 Torr by controlling the mass of the gas introduced.

Step 5: the induction coil and the graphite heating body synchronously move downwards at the speed of 3mm/min until the lower cone part of the powder rod stops.

Step 6: the temperature of the heating body is raised to 1400 ℃, and the air supply of the process air is stopped at the air inlet of the process air. Vacuum was started and the muffle tube pressure was controlled to <0.5 torr.

Step 7: the induction coil and the graphite heating body synchronously move upwards at the speed of 3mm/min until the lower cone part of the powder rod stops.

Step 8: cooling to room temperature, and providing the glass rod.

The obtained product is transparent and bubble-free, the hydroxyl content is lower than 0.1ppm, and the refractive index difference compared with quartz is-0.3%.

Specific application example 3: preparation of a Multi-bubble preform

Step 1: after the powder rod enters the quartz glass muffle tube, the induction coil and the graphite heating body at the bottom start to heat up to 1200 ℃.

Step 2: heating the heating element to 1200 ℃, and introducing N ₂ And controlling the opening of the gas outlet valve to keep the relative pressure in the muffle tube at 3000pa at 10L/min.

Step 3: the induction coil and the graphite heating body synchronously move upwards at the speed of 4mm/min until the shoulder of the powder rod stops.

Step 4: heating the heating element to 1450 ℃ and continuously supplying N ₂ The flow rate was kept constant and the relative pressure in the muffle tube was kept at 3000pa.

Step 5: the induction coil and the graphite heating body synchronously move downwards at the speed of 4mm/min until the lower cone part of the powder rod stops.

Step 6: cooling to room temperature, and providing the glass rod.

The obtained glass body is slightly fogged, and after high-temperature drawing, the optical fiber has abundant small bubbles.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Claims (9)

1. The utility model provides a powder stick heating vitrification device, includes send excellent device, glass muffle tube and arranges the inside heating furnace body of glass muffle tube in, and the upper end of powder stick is through sending excellent device centre gripping, send excellent device to be used for realizing that the powder stick reciprocates and rotate in the heating furnace body, is equipped with technology air inlet in glass muffle tube bottom, upper portion and is equipped with the gas vent, its characterized in that, heating furnace body's upper end is connected through the hanger, the hanger passes through the clamping of reciprocates mechanism, the upper end of powder stick, the upper end of hanger stretch out outside the sealed apron that glass muffle tube upper end set up to through sealing component seal arrangement, correspond the heat-generating body at the periphery of glass muffle tube and be equipped with induction heating coil, induction heating coil can reciprocate relatively glass muffle tube.

2. The powder rod heating vitrification device of claim 1, wherein the heating furnace body comprises a heating body arranged in a furnace shell, a peripheral heat insulation layer is arranged on the periphery of the heating body, an upper heat insulation layer and a lower heat insulation layer are respectively arranged at the upper end and the lower end of the heating body, and the hanging piece is connected with the furnace shell through a furnace body connecting plate.

3. The powder rod heating vitrification apparatus as set forth in claim 2, wherein the thickness of the heat generating body is: 4mm-8mm; the height is 500-600mm; the induction coil height was 400mm.

4. The powder rod heating vitrification device as set forth in claim 1 or 2, wherein an infrared temperature probe is provided outside the heating body, and a temperature measuring hole is provided in the heating body corresponding to the infrared temperature probe.

5. The powder rod heating vitrification apparatus of claim 2, wherein the thickness of the peripheral insulating layer is 50mm to 70mm, and the thicknesses of the upper insulating layer and the lower insulating layer are respectively: 55mm to 75mm.

6. The powder rod heating vitrification device of claim 2, wherein the distance between the heating element and the heat insulation layer and the glass muffle tube is: 10-20mm.

7. The powder rod heating vitrification device of claim 2, wherein the heating element is made of pure graphite material, the peripheral heat insulation layer is a graphite soft felt, and the upper heat insulation felt and the lower heat insulation felt are both graphite hard felt.

8. The powder rod heating and vitrification device according to claim 1 or 2, wherein the rod feeding device comprises a bearing hook and a bearing bracket, the upper ends of the powder rods are connected through the bearing hook, the upper ends of the bearing hook can realize up-and-down movement and rotation of the powder rods, the upper ends of the bearing hook are connected with a connecting rod, the connecting rod penetrates out of the sealing cover plate to be connected with the bearing bracket, and the bearing bracket can realize up-and-down movement of the powder rods.

9. A method for vitrification by heating a powder rod is characterized in that,

step one, providing the powder rod heating vitrification device according to any one of claims 1 to 8;

step two, controlling the heating body to move to the lower cone part of the powder rod, starting to introduce process gas, and closing a pipeline valve leading to the vacuum pump when the process gas is introduced for pretreatment;

step three, the induction heating coil starts to heat a heating body, the temperature measuring probe feeds back the temperature in the furnace, the sealing part seals the furnace body, the induction heating coil and the heating body synchronously move upwards, and the powder rod is preprocessed;

and step four, after the pretreatment is finished, the induction heating coil and the heating body return to the initial positions, the temperature is raised to the set temperature, the vacuum pipeline valve of the exhaust port is opened, the valve of the waste gas pipeline is closed, the glass muffle tube is pumped to a vacuum state, the movement of the heating body is repeated, and the sintering of the powder rod is started.