Quartz glass ingot and method and apparatus for manufacturing same

Abstract

The invention relates to a quartz glass ingot and a method and apparatus for manufacturing the same. A method and apparatus for manufacturing a quartz glass ingot having a large cross-sectional area by continuous flame melting wherein on-line crack-free cutting of the ingot is ensured by utilizing the internal heat of the ingot to balance the internal temperature with the surface temperature while passing through one or more annealing chambers, thus, controllable cooling to a temperature at which the ingot can be cut by a water-cooled saw is ensured.

Description

[0001] This application is a divisional application of the invention patent application filed on November 25, 2019, with application number 201911167922.0 and entitled "Quartz Glass Ingot and Method and Apparatus for Manufacturing the Ingot". Technical Field

[0002] In a first aspect, the present invention relates to a method for the continuous manufacture of quartz glass ingots. In a second aspect, the present invention relates to an apparatus for manufacturing quartz glass ingots used in the claimed method, and in a third aspect, the present invention relates to a quartz glass ingot prepared according to the claimed method. Background Technology

[0003] Methods and equipment for the continuous production of quartz glass ingots are known from the prior art. These methods are not suitable for the continuous production of large quartz glass ingots that are cut into smaller segments after extrusion. Specifically:

[0004] US 3,764,286 discloses a method for forming rods and tubes by melting quartz in an electrically heated refractory metal crucible and drawing it out from a die in the furnace bottom. The resulting ingots extruded from the die are cooled with ambient air and then cut on-line to suitable lengths. Because the extruded ingots have relatively small dimensions and relatively small cross-sectional areas, the cutting step is not critical.

[0005] CN 102875007 discloses a quartz furnace for the continuous manufacturing of solid ingots. Rods with a diameter up to 180 mm are prepared by extruding molten quartz from an electrically heated refractory metal crucible and then cutting them. Again, due to the small ingot diameter, there are no limitations or problems in the cutting process for the extruded rods.

[0006] Large-diameter fused quartz ingots have also been produced using electromelting in batch processes, see, for example, US 2009 / 0100871 A, which describes melting a bed of quartz powder in a refractory-lined crucible to obtain glass ingots with a diameter of 1700 mm and a height of 620 mm. This method suffers from several limitations. It has been shown that it is difficult to ensure the complete removal of all gases bound to the quartz grains (i.e., trapped within or between quartz particles), and it is difficult to ensure that the glass does not flow during melting, meaning that any localized impurities have no opportunity to mix. Therefore, the quality of quartz glass produced by this method is limited by the presence of bubbles and inclusions, which are unacceptable for the most critical applications. Furthermore, the productivity of this multi-stage batch process is limited by its involvement of loading, preheating, melting, and subsequent cooling, and attempts to reduce cycle time risk producing lower-quality products.

[0007] US 7,305,852 discloses a method for flame melting quartz glass in a rotating crucible or refractory vessel. Even if the method is intended to produce quartz glass ingots with large diameters, it is equivalent to the classic batch process, which does not require ingots to be cut online.

[0008] CN 101148311 discloses a method for continuous flame melting of quartz using an oxyhydrogen flame, simultaneously extracting ingots and performing inline cutting. The applied melting rate is relatively low (1.2 to 1.8 kg / h), and the maximum size of the resulting ingot is 300 mm in diameter for a single burner. Even after the ingots are subsequently cut inline, there is no indication of any problems with the cutting process, specifically any problems caused by cracks forming in the cut sections of the ingot.

[0009] Flame melting avoids some of the disadvantages mentioned above. Therefore, a typical flame melting process is a variation of the Verneuil process, in which quartz powder is passed through an oxyhydrogen flame and impacts the molten end surface of an ingot rotating about a horizontal or vertical axis, and is slowly pulled out of the hot zone as it moves away from the high-temperature region (e.g., US 4,368,846).

[0010] KR 2018 / 004353 discloses a method for hydrogen-oxygen melting of quartz powder in a crucible to form a large-diameter melt. In this method, the crucible is static and, in order to achieve a longer ingot length, the crucible bottom is lowered during operation so that the extruded glass cools and solidifies below the crucible, and the ingot thus formed is contained in an adiabatic chamber. Although the extruded ingot can thus be annealed in this chamber at the end of the furnace run (by gradually cooling the glass in the crucible and the glass suspended below), the method is still a batch process and is technically complex.

[0011] US 2,398,952 discloses an apparatus for the continuous production of quartz glass products, wherein the apparatus includes a refractory chamber with a die opening at the bottom and components for vertically drawing out softened quartz glass lumps via a die to provide ingots.

[0012] US 3,212,871 discloses an electrically heated tank furnace for melting glass, wherein the furnace comprises: a tubular melting crucible surrounded by a heating wire; a drawing nozzle located at the lower end of the crucible for continuously drawing the melt within the crucible into a quartz glass tube; and a component for introducing a protective gas into the melt above the interior of the crucible, wherein the crucible wall above and near the top surface of the melt is provided with a plurality of holes leading to the outside of the crucible as outlet channels for the gas, thereby preventing vapors detached from the surface of the melt from rising within the crucible, instead being carried away by the flow of the protective gas and escaping to the outside of the crucible through the holes.

[0013] The internet paper "Available dimensions chemical purity - typical traceelements and OH content in quartz-glass (ppm by weight oxide)" proposes the preparation of large-diameter ingots using a continuous flame melting method, but does not disclose how to cut these ingots without causing severe cracking. Specifically, this internet paper does not disclose that the ingots can be cut online.

[0014] WO 2007 / 107709 A discloses ingots with a fairly large diameter, but such ingots are produced as single ingots of finite length, deposited directly with minimal use of containers, i.e., deposited at the top of a self-supporting ingot. Such ingots are not produced continuously by stretching softened glass in a crucible and through a mold.

[0015] WO 00 / 03955 A discloses a method for pulling a synthesized molten silica ingot from a crucible (optionally a rotary crucible). The ingots produced by this method are substantially small in cross-sectional area. According to the method, the refractory chamber of the apparatus used has a die opening at its bottom, through which a softened quartz glass agglomerate is pulled vertically. After being pulled from the die, the agglomerate passes through a chamber below the crucible, constructed of, for example, an insulating material. However, this arrangement of the apparatus according to the prior art references fails to achieve controlled cooling of the ingot because the length of the insulating bricks constituting the chamber is too short to complete the annealing step of the quartz material. Furthermore, the insulating bricks being located directly below the crucible indicates that their function is not to cool the quartz ingot in a controlled manner, but rather to support the hot crucible. Therefore, the ingot thus produced can only be naturally cooled to a point where it can be cut by radiation and convection. For continuous ingot production (especially large ingots), the simple natural cooling proposed in the prior art references is unacceptable.

[0016] In summary, none of these disclosures disclose a continuous manufacturing method for large-diameter ingots (e.g., those with a diameter greater than 350 mm) or a crack-free inline cutting method for such ingots. Summary of the Invention

[0017] Starting from this existing technology, the objective is to provide a method for manufacturing quartz glass ingots that can be prepared without the aforementioned disadvantages.

[0018] Specifically, the objective is to provide a method for manufacturing quartz glass ingots that can be continuously prepared and cut.

[0019] More specifically, the objective is to provide a method for manufacturing quartz glass ingots that can be continuously prepared and cut and have a large outer diameter.

[0020] More specifically, the objective is to provide a method for manufacturing quartz glass ingots that can be continuously prepared and cut without cracking and have a large outer diameter.

[0021] Furthermore, the objective is to provide an apparatus capable of continuously manufacturing and cutting quartz glass ingots without cracking, wherein the quartz glass ingots have a large diameter. This apparatus should be suitable for performing the claimed method.

[0022] The basic idea behind addressing these goals is to implement online self-annealing using the internal heat of the ingots prepared by extrusion.

[0023] Accordingly, the present invention relates in a first aspect to a method for the continuous production of quartz glass ingots, the method comprising the following process steps:

[0024] a. Provide softened quartz glass material in the crucible or refractory jar;

[0025] b. Softened quartz glass lumps are vertically drawn through a mold to provide quartz glass ingots; and

[0026] c. Cut the quartz glass ingot into a specific length on a wire.

[0027] The method is characterized in that the quartz glass ingot is cooled after extrusion in step b until the temperature of the outer surface of the ingot is within the strain point range of the softened quartz glass material, and then the quartz glass ingot is insulated.

[0028] Accordingly, it has been found that in-line annealing of the extruded and pre-cooled quartz glass ingot can effectively reduce the residual stress of the ingot, the in-line annealing being provided by the ingot's internal heat. The in-line annealing step reduces the residual stress of the ingot, making it possible for the cut ingot segments to be free of cracks or at least have fewer cracks when the quartz glass ingot is cut using a continuous method.

[0029] Accordingly, one embodiment relates to a method for the continuous production of quartz glass ingots, the method comprising the following process steps:

[0030] a. Provide softened quartz glass material in the crucible or refractory jar;

[0031] b. Softened quartz glass lumps are vertically drawn through a mold to provide quartz glass ingots; and

[0032] c. Cut the quartz glass ingot into specific lengths using a wire cutter.

[0033] The quartz glass ingot is characterized by being online annealed after extrusion in step b and before online cutting in step c.

[0034] This online annealing is preferably accomplished by cooling the quartz glass ingot until the temperature of the outer surface of the ingot is within the strain point range of the softened quartz glass material, and then insulating the quartz glass ingot.

[0035] In this article, annealing refers to the method of slowly cooling a hot glass object after it has been formed in order to reduce residual internal stresses introduced during manufacturing.

[0036] According to this disclosure, the residual stress in the prepared ingot can be reduced to minimize the risk of ingot crack initiation, and specifically, once a crack begins to appear, it can continuously propagate along the descending ingot. Thus, the claimed method does not require extremely slow cooling of the ingot and avoids cutting the ingot at a considerable distance below the furnace, a distance impossible to achieve without increasing the height of the building in which the method is implemented.

[0037] This disclosure applies to the manufacture of quartz glass ingots having any outer diameter. However, quartz glass ingots with an outer diameter exceeding 350 mm are prone to cracking during the cutting process, and therefore, this disclosure is particularly applicable to the manufacture of quartz glass ingots with an outer diameter exceeding 350 mm, especially exceeding 400 mm, even more especially exceeding 450 mm, and most especially exceeding 500 mm.

[0038] First aspect of the invention

[0039] - Continuous method for manufacturing quartz glass ingots -

[0040] The method of the present invention is described in more detail below:

[0041] Step a.: Provide softened quartz glass material in a crucible or refractory flask.

[0042] In process step a., softened quartz glass lumps are provided as starting material in a crucible or refractory jar.

[0043] Therefore, a refractory vessel or crucible is typically provided in the furnace, which allows for heating and containment of quartz glass lumps. Starting materials are typically fed into the refractory vessel or crucible as a silicon source, said silicon source being selected from the group consisting of silica, quartz powder, and at least one silicon-containing precursor.

[0044] In the case of silica or quartz powder, the starting source is crystalline quartz or amorphous silica powder. The powder may be of natural or synthetic origin.

[0045] In the case of silicon-containing precursors, the starting material is typically a halogen-free silicon precursor, specifically a siloxane compound, such as octamethylcyclotetrasiloxane. This silicon-containing precursor is converted into a stream of silica micron-sized particles in a flame and deposited on the melt surface. Such methods are described, for example, in US 6,763,682.

[0046] In one embodiment, quartz powder supplemented by a silicon-containing precursor stream can be used.

[0047] The silicon source can be doped by adding at least one additional component (specifically, by adding at least one oxide compound). In the case of preparing a doped quartz glass ingot, the addition of one or more additional components is necessary.

[0048] The silicon source is typically fed into the refractory jar or crucible from above and can also be fed through a burner into the refractory jar or crucible. Therefore, the burner is preferably located in the furnace top. The method may also include alternative methods of introducing the starting material into the refractory jar or crucible.

[0049] Burners are typically filled with at least one combustible gas and oxygen, wherein the combustible gas may be selected from the group consisting of hydrogen, natural gas or hydrocarbon gases, especially propane, and mixtures thereof.

[0050] By feeding a silicon source through a burner into a crucible or refractory vessel, the silicon source is heated by the burner en route and reaches the surface of the melt, where it melts into glass. Furthermore, the burner sprays one or more clusters of flame downwards onto the surface of the molten silicon source, which helps to melt the starting material.

[0051] If it is necessary to form opaque quartz glass, the powder can be doped by adding solid or liquid gas-forming agents, but the powder is usually undoped and has high purity when necessary to provide bubble-free fused quartz glass ingots.

[0052] The temperature of the melt surface and / or furnace wall can be measured using an optical pyrometer, and the interior of the furnace can be observed, for example, through the vent.

[0053] Step b.: Vertically pull out the softened quartz glass mass through a mold to provide a quartz glass ingot.

[0054] In the next step b, molten silica is extruded substantially vertically from the furnace through a die-shaped orifice, which is typically located in the furnace bottom and thus on the opposite side of the burner, thereby producing a quartz glass ingot.

[0055] Molten silica extruded from a furnace through a die in a crucible or refractory vessel solidifies on its outer surface after cooling, thus producing a quartz glass ingot.

[0056] The external dimensions and form of the ingot are defined by the external shape of the die hole located in the furnace bottom.

[0057] Typically, in step b, the outer diameter of the extruded quartz glass ingot is greater than 350 mm, more preferably greater than 400 mm, further preferably greater than 450 mm, and most preferably greater than 500 mm.

[0058] After molten silica is extruded through a die to produce quartz glass ingots, the ingots are cooled by radiation and / or convection of ambient air. Alternatively, the ingots can be cooled by radiation and / or convection of inert and / or reducing gases.

[0059] In addition to this normal cooling, it can also enhance the cooling process of the quartz glass ingot after it has been removed from the mold of the crucible or refractory jar.

[0060] Drawing air upwards around the ejected ingot can be used to promote cooling of the quartz glass ingot. Another possible way to cool the ingot is to direct a high-speed flow of cooling gas or water droplets towards the ingot.

[0061] This enhanced active precooling enables the surface temperature of the quartz glass ingot to drop to between 900 and 1150°C, more preferably 925 to 1075°C, and most preferably 950 to 1050°C within a short distance. These temperatures represent the preferred lower limit of the surface temperature achievable before the ingot enters the annealing chamber. Achieving such temperatures in the pre-annealing stage allows for a reduction in the overall distance between the mold and the cutting station, but is not essential to the method.

[0062] As mentioned above, the method requires cooling the quartz glass ingot after it has been extruded from the crucible or refractory jar in step b. until the temperature of the outer surface of the ingot is within the strain point range of the softened quartz glass material, and then insulating the quartz glass ingot.

[0063] As explained further below, the ingot is usually pulled vertically from the crucible or refractory crucible, which requires that the ingot also be vertically annealed on the line after demolding.

[0064] Therefore, within the aforementioned method, it is crucial to provide a vertical facility for online annealing of the descending ingot. However, this is not a simple matter, especially in a plant setting, where it is not simply a matter of increasing the distance between the furnace and the cutting position and then unloading the large fused quartz ingot. Therefore, it is necessary to cool the ingot and balance the temperature distribution (and thus the stress distribution) throughout the ingot, and to achieve these objectives within a limited vertical height.

[0065] To achieve online annealing of the ingot, the ingot is preferably passed through one or more annealing chambers, which allow the ingot to be cooled in a controlled manner so that the axial and radial temperature gradients within the glass are gradually reduced, while the overall temperature of the ingot is reduced under well-controlled conditions.

[0066] The online annealing of the ingot is preferably carried out in one or more annealing chambers made of lightweight insulating material. In these annealing chambers, the ingot is gradually cooled under conditions where the radial temperature gradient within the glass is significantly reduced.

[0067] In the annealing chamber provided by the lightweight insulating material, the cooling method includes convective heat dissipation to ambient air and rising through the chamber.

[0068] Options for chamber design, airflow, and insulation properties can be selected by those skilled in the art and supplemented by appropriate computer simulations.

[0069] The ingot passes through the annealing chamber, preferably at a surface temperature of less than 600°C, more preferably less than 550°C, and most preferably less than 500°C.

[0070] After this online annealing and further gradual cooling as the ingot descends to the horizontal plane of the cutting station, the ingot center temperature is still slightly higher than the surface temperature, but the tensile stress on the ingot surface is reduced to preferably less than 5 MPa, more preferably less than 4 MPa, and most preferably less than 2 MPa.

[0071] As explained above, before online annealing in the annealing chamber, the ingot that has been ejected from the mold can be cooled until the external temperature is within the strain point range.

[0072] The strain point of the quartz glass material used is when the glass viscosity is 10. 14.5 The temperature at which the viscosity can be easily measured by technicians in the field is also known as the viscosity measurement temperature.

[0073] Commonly used quartz glass material (viscosity is 10) 14.5 The strain point of the ingot is approximately 1080°C. For this type of material, the temperature of the outer surface of the ingot at the time of entry into the annealing chamber may be between 900 and 1150°C (T0). s ), or even slightly higher. At this point, the decrease in ingot (T) c The core temperature will be significantly higher.

[0074] When the ingot passes through an annealing chamber made of, for example, a lightweight insulating material to prevent further heat loss from the surface, the internal temperature of the ingot is balanced with the external surface temperature.

[0075] The optimal length of the annealing chamber makes T c With T s The differences between them are small, but it is desirable that the surface temperature be further reduced to a value that allows for cutting with a water-cooled saw when the ingot arrives at the cutting station.

[0076] Adjusting T as described above c With T SUnder the condition of the difference, the residual stress and elastic stress are both sufficiently reduced, and the ingot can be cut without cracking or with a low and acceptable risk of cracking.

[0077] Step c.: Cut the quartz glass ingot into specific lengths on a wire.

[0078] The cutting station is located near the mold used to pull the quartz glass ingot from the crucible or refractory jar and is spaced apart from the mold along the quartz glass ingot. The distance between the cutter and the mold depends on the height of the building, but is usually in the range of 2.75 to 3.5 meters.

[0079] The temperature of the outer surface of the ingot in the cutting zone can be measured using any suitable method (e.g., optical pyrometers and / or thermocouples). However, the temperature at the ingot center can only be estimated through computer simulation.

[0080] In step b), the quartz glass ingot extruded through the die extends downwards from the die orifice, passing through the pre-cooling zone and the annealing chamber, as outlined above. This cools the quartz glass ingot to the aforementioned temperature distribution.

[0081] During downward movement, the quartz glass ingot is supported by specific conveying members. In a preferred embodiment, these conveying members for supporting the quartz glass ingot are two or more clamps mounted on a bracket, wherein the clamps mounted on the bracket are adapted to move downward from the die orifice at a speed that tracks the molten silica extruded from the die orifice. In the method of the present invention, at least two clamps are required to allow for reciprocating motion of the clamps. At least two clamps need to be in constant contact with the ingot to maintain straightness, and typically one or more clamps are required to allow for support of the ingot during ingot cutting.

[0082] The clamps mounted on the bracket and the quartz glass ingot preferably move downward at a predefined speed so as to keep the softened quartz glass mass in the furnace (i.e., crucible or refractory flask) at a substantially constant horizontal level.

[0083] The cutting and removal of the cut ingot segments (cutting ingot segments) should preferably be carried out online to achieve a continuous process.

[0084] For this reason, the quartz glass ingot is pulled downwards until it reaches a first predefined position. At this first predefined position, the quartz glass ingot reaches the bottom support, where the ingot section needs to be cut off. The portion of the quartz glass ingot to be cut off is preferably still supported by one of several clamps.

[0085] The cutting station is preferably configured as a saw, more preferably as a water-cooled saw, specifically a heavy-duty water-cooled chainsaw or wire saw. The saw cutting medium is preferably a metal-welded diamond (diamond-tipped saw).

[0086] At the cutting station, the quartz glass ingot is cut circumferentially using a saw. Furthermore, it is preferable that the quartz glass ingot is cooled with an external water spray before being cut at the cutting station.

[0087] After the quartz glass ingot is cut, the cut section of the ingot is sufficiently reduced. This makes it possible to remove and take out the cut ingot section for optional further processing steps.

[0088] Before the cut spindle segment is removed, it is preferable to release the clamps attached to the cut spindle segment.

[0089] After the cut segment of the quartz glass ingot is removed from the second predefined horizontal plane (floor horizontal plane), it is preferable to raise the clamps and bottom bracket of the previous cut segment of the quartz glass ingot to the body of the quartz glass ingot and reattach them to the body of the quartz glass ingot, thereby allowing the descending ingot to continue to be supported until the next cut is required. Attached Figure Description

[0090] Figure 1 An embodiment of a furnace for implementing the method of the present invention is shown.

[0091] Figure 2 A preferred embodiment of the claimed method is shown. Detailed Implementation

[0092] In the following text, refer to Figure 1 and 2 A preferred embodiment of the claimed method is described below:

[0093] The following component symbols are used in these drawings:

[0094] 10 refractory tanks

[0095] 11 furnace chambers

[0096] 12 Furnace Chamber Floor

[0097] 13 Melt

[0098] 14 Burners

[0099] 15 Powder Feed

[0100] 16 exhaust ports

[0101] 17 exhaust channels

[0102] 18-hole die

[0103] 19 ingots

[0104] 20 clamps

[0105] 21 Cutting Station

[0106] 22 support plates

[0107] 23 Refractory Bricks

[0108] 24 chimneys (optional, provide available cooling air)

[0109] 25 pyrometer 1

[0110] 26 pyrometers 2

[0111] 27 pyrometer 3

[0112] 28 pyrometer 4

[0113] Annealing Chamber 1, 29

[0114] 30 Insulation

[0115] 31 Annealing Chamber 2 (Perforated)

[0116] 32 Cooling air (through and within the walls of chamber 2)

[0117] 33. Starting point of annealing section

[0118] End of annealing section 34

[0119] 35 thermocouple 1

[0120] 36 thermocouples 2

[0121] 37 thermocouple 3

[0122] 38 thermocouples 4

[0123] Temperature distribution when 39 enters annealing chamber 1

[0124] Temperature distribution when 40 leaves annealing chamber 2

[0125] An embodiment of a furnace for implementing the method of the present invention is schematically shown in Figure 1 middle.

[0126] The furnace includes a refractory vessel or crucible 10 enclosed within a furnace chamber 11. The refractory vessel may be made of brick, for example, zirconium or yttrium-stabilized zirconium oxide, and contains molten silica melt 13. This innermost layer of refractory brick may be surrounded by one or more layers of insulating material to provide further insulation and reduce heat loss through the furnace walls, said insulating material comprising brick, ceramic fiber, zirconia hollow spheres, or other suitable materials. Common furnace constructions are known to those skilled in the art.

[0127] Combustible gas (e.g., hydrogen, natural gas, propane, or other hydrocarbon gases, or mixtures thereof) and oxygen are supplied to one or more burners 14 located at the furnace top, the burners providing one or more clusters of flames injected downwards onto the surface of the melt. Quartz powder 15 (i.e., crystalline or amorphous silica powder, which may be of natural or synthetic origin) may be added via one or more burners or introduced through alternative components. Optionally, if it is desired to produce a doped quartz glass ingot, the powder may be doped by adding one or more additional components (e.g., in the form of oxides). The powder may be heated en route and reach the surface of the melt 13, where it melts into glass. If it is desired to form opaque quartz glass, the powder may be doped by adding a solid or liquid gas-forming agent, but the powder is typically undoped and, if necessary, has high purity to provide a bubble-free fused quartz ingot.

[0128] Combustion products leave the furnace through outlet 16 and subsequently exit the furnace chamber through exhaust duct 17.

[0129] In another embodiment, the powder feed can be supplemented or replaced with a suitable silicon-containing precursor stream (preferably a halogen-free precursor, such as a siloxane, for example, octamethylcyclotetrasiloxane (OMCT, D4)), which can be converted into a stream of silica micron particles in a flame and deposited on the surface of melt 14 (as described, for example, in US 6,763,682).

[0130] The temperature of the melt surface 13 and / or the furnace wall can be measured using one or more optical pyrometers 25, 26, 27 and 28. The interior of the furnace can be observed through the vent 16.

[0131] The furnace cross-section can be circular, polygonal, or square, but preferably conforms to the shape of the desired ingot product. An orifice 18 is provided at the furnace bottom, acting as a mold and defining the external dimensions of the ingot 19 extruded from it. The mold can contain refractory ceramic materials, such as yttrium-stabilized zirconia or zirconium, or can be made of refractory metals (e.g., tungsten or molybdenum), in which case oxidation resistance can be promoted by appropriately coating the metal surface (e.g., with a coating of metal silicides) or by providing an inert or reducing gas environment.

[0132] The glass is extracted at a high viscosity and, upon rapid cooling, its outer surface solidifies almost immediately. The ingot extends downward and is supported by a series of clamps 20 mounted on supports, which can move downward at a rate suitable for the glass flow (i.e., comparable to the powder feed rate), thereby maintaining the melt within the furnace at a constant depth. When each support reaches its lower limit of travel, it releases its grip on the ingot and moves to its upper limit, at which point it re-clamps the ingot. The ingot is always held by two or more sets of clamps, thereby ensuring the ingot's straightness. A cutting station 21 is located at the lower end of the ingot, where it can be cut to a suitable length and then removed for further processing.

[0133] Suitable cutting components include heavy-duty water-cooled chainsaws or wire saws, and the cutting medium can be metal-bonded diamond.

[0134] The ingot immediately below the mold is cooled by radiation and convection of surrounding air (or, where appropriate, inert / reducing gas). Air drawn upwards around the ingot into furnace chamber 11 can be used to promote cooling (cooling air 24), and can be further promoted if needed by jetting high-speed streams of cooling gas, providing water droplets, etc.

[0135] The glass surface temperature in the mold area and the ingot temperature below the mold can be measured using one or more suitable optical pyrometers 25, 26, 27, and 28. If necessary, thermocouples or alternative methods can also be used to measure localized temperatures.

[0136] Cooling of the outer surface of the ingot can be achieved through convection and radiation to the environment, but prior to cutting, additional cooling of the ingot by external water spray from a ring of spray nozzles located around the ingot may be applicable to ensure that the temperature of the outer surface of the ingot is reduced to below approximately 300°C before cutting with a water-cooled saw.

[0137] The method according to one embodiment typically begins by filling the furnace cavity with fused silica fragments and shielding the die orifice with cylindrical fused silica guide blocks, which are then held in the correct position by clamps 20. After the furnace contents begin to melt, silica powder is introduced through one or more burners 14 and the ingot 19 is pulled down while maintaining a substantially constant melt level within the furnace.

[0138] After the quartz glass ingot leaves the crucible or refractory jar 10, it is preferable to perform a cooling step on the ingot, which... Figure 2 The symbol 24 (chimney or pre-cooling area) is shown in the Chinese.

[0139] The ingot passes through the upper annealing chamber 29 and the lower annealing chamber 31. At the starting point 33 of the annealing chamber 30, the ingot is on its outer surface (T). S ) and spindle center (T C There is a temperature distribution 39 between them, and after the end point 34 of the annealing zone 31, the ingot is on the outer surface of the ingot (T S ) and spindle center (T C There is a temperature distribution of 37°C between these two temperatures. The temperature distribution of 36°C is due to T. C With T S The differences between them are large and increase sharply, while in temperature distribution 37, T C With T S The difference between them depends on temperature T C and T S They are much closer to each other and much lower.

[0140] The above method, which includes ingot extrusion, annealing, and repeated intermittent cutting steps, can be carried out for an indefinite period of time, limited only by the requirements of the ingots produced.

[0141] Second aspect of the invention

[0142] - Equipment used in a method for continuous manufacturing of large fused silica ingots -

[0143] In a second aspect, the present invention relates to an apparatus for the continuous production of quartz glass ingots. This apparatus is capable of performing the above-described method and comprises the following components:

[0144] (a) A crucible or refractory jar for providing softened quartz glass lumps, the bottom of which has a die hole;

[0145] (b) A component for vertically drawing out a softened quartz glass mass via a mold to provide a quartz glass ingot;

[0146] (c) Optional components for cooling the quartz glass ingot until the outer surface temperature of the ingot is within the strain point range of the softened quartz glass material; and

[0147] (d) A component used to cut quartz glass ingots into specific lengths on a wire.

[0148] The claimed device is characterized in that it includes components for annealing the ingot before it is cut inline.

[0149] The component used to anneal the quartz glass ingot before online cutting is preferably made of one or more insulating materials, the panels surrounding the ingot with a predetermined gap.

[0150] In addition, the construction of the baffle allows it to function as a chimney that allows cooling air to flow upwards in a controlled manner around the ingot.

[0151] The temperature inside the partition can be monitored by thermocouples, pyrometers or other suitable components.

[0152] The specific design of the partitions and the resulting annealing chamber can be approached empirically or supported by computer simulation.

[0153] The device may include other components and parts mentioned below. The functions of these additional parts become apparent from the description above and are briefly summarized below:

[0154] The claimed equipment includes a crucible or refractory jar, preferably with a burner on top and a die hole at the bottom.

[0155] The starting materials used to manufacture quartz glass ingots are typically supplied to a crucible or refractory vessel via a burner equipped with a supply component for oxygen and combustible gases (e.g., hydrogen, natural gas, hydrocarbon gases such as propane, and any suitable mixture thereof).

[0156] Crucibles or refractory vessels are typically arranged in the enclosed furnace chamber.

[0157] The refractory vessel or crucible can be made of bricks, such as zirconium or yttrium-stabilized zirconium oxide, and is suitable for containing molten silica. This innermost layer of the refractory brick can be surrounded by one or more layers of insulating material to provide further insulation and reduce heat loss through the furnace wall, said insulating material comprising brick, ceramic fiber, zirconia hollow spheres, or other suitable materials.

[0158] The starting material of the method (e.g., quartz powder) can be added by one or more burners or introduced by alternative components.

[0159] The furnace cross-section can be circular, polygonal, or square, but preferably conforms to the shape of the desired ingot product. An orifice is located at the furnace bottom, acting as a mold and defining the external dimensions of the ingot extruded from it. The mold can contain refractory ceramic materials, such as yttrium-stabilized zirconia or zirconium, or can be made of refractory metals (e.g., tungsten or molybdenum), in which case oxidation resistance can be promoted by appropriately coating the metal surface (e.g., with a coating such as a metal silicide) or by providing an inert or reducing gas environment.

[0160] Additionally, the claimed device includes a movable carriage and clamps that support downward movement of the extruded ingot. The clamps are typically mounted on the carriage. The clamps are configured to hold the extruded ingot and are capable of clamping and releasing the ingot. The claimed device preferably includes at least two clamps for holding the resulting ingot.

[0161] The claimed equipment also includes a spindle cutting station where spindles can be cut to suitable lengths. Cutting components suitable for the claimed equipment include heavy-duty water-cooled chainsaws or wire saws, and the cutting medium can be welded diamond.

[0162] The claimed device may also include components for cooling the outer surface of the quartz glass ingot, such as a water spray that may be arranged above the cutting station (21) of the claimed device.

[0163] Furthermore, the claimed device includes components that directly cool the ingot after it has exited the die. This means that the ingot can be cooled by radiation and convection of surrounding air, flow of inert gas, flow of reducing gas, and water droplets.

[0164] The device may also include an optical pyrometer, a thermocouple, or alternative components for monitoring the temperature of the ingot at different locations.

[0165] Other components of the claimed apparatus become apparent from the detailed description of the claimed methods disclosed above. These embodiments particularly relate to apparatus components for performing the methods described above.

[0166] Therefore, the device preferably includes a component that ensures the spindle center temperature T C With the outer surface temperature T of the ingot S The difference between the components gradually decreases during the adiabatic period due to the decrease in the internal heat of the quartz glass ingot.

[0167] More preferably, the device includes a component that ensures the quartz glass ingot is cooled to a surface temperature between 900°C and 1150°C before adiabatic treatment.

[0168] More preferably, the device includes a component that ensures that the quartz glass ingot is cooled to a surface temperature of less than 250°C before cutting.

[0169] More preferably, the device includes components that ensure the residence time during insulation is 20 to 150 hours.

[0170] More preferably, the device includes a mechanism to ensure an outer surface temperature T S With center temperature T C The difference between the components is less than 40°C after adiabatic treatment.

[0171] More preferably, the device includes a component that ensures that the surface tensile stress of the quartz glass ingot is less than 5 MPa before cutting in step c.

[0172] More preferably, the device ensures that the spacing between the cutting zone and the die hole is less than 4.00 m along the quartz glass ingot that has been removed from the die hole.

[0173] Third aspect of the invention

[0174] - Large quartz glass ingots -

[0175] Finally, the present invention relates to quartz glass ingots prepared according to the above method or using the above equipment, thereby cutting the quartz glass ingots into segments of predefined lengths.

[0176] The claimed quartz glass ingot is characterized by having an outer diameter of more than 350 mm, more preferably more than 450 mm, and most preferably more than 500 mm.

[0177] The claimed quartz glass ingot is further characterized in that the tensile stress of the ingot is preferably less than 5 MPa, more preferably less than 4 MPa, and most preferably less than 2 MPa.

[0178] The claimed characteristic of the quartz glass ingot is that the cross-sectional area of ​​the ingot is preferably greater than 96,000 mm². 2 More preferably, greater than 150,000 mm2 The optimal selection is greater than 180,000 mm. 2 .

[0179] The resulting ingot is preferably composed of glassy silica, especially high-purity transparent fused silica, making it suitable for semiconductor and optical applications.

[0180] The present invention is described in more detail with reference to the following examples:

[0181] The distance between the mold 18 and the furnace floor 12 is 300 mm, and the chimney vent 24 is not opened in this test.

[0182] Below the floor is a 250 mm high space allowing the uppermost clamp 20 to reciprocate, and below that is an upper insulation chamber 30 extending downwards by 500 mm. This section comprises an octagonal plate assembly of Vecoboard RCF1400 and 12 mm thick refractory ceramic fiber panels (Eco Technical Ceramics, Bolton). These panels are supported at a distance of approximately 50 mm relative to the descending ingot, allowing air to flow upwards in the channel between the insulation chamber and the ingot.

[0183] The lower insulating section 30 is an open area (250 mm high, allowing movement of one of the clamps 20); this is followed by a second insulating chamber 31, 500 mm long, which contains another octagonal assembly made of 1.5 mm thick perforated stainless steel plates with 10 mm diameter holes spaced 13 mm apart (FH Brundle). Again, these plates are mounted approximately 50 mm from the ingot, allowing air to flow inward and upward within these shaped channels, providing gradual and controlled cooling, and preventing sudden temperature changes when the ingot is removed from the upper annealing chamber.

[0184] Thermocouples 32 to 35 are installed at the top and bottom of each of these insulation chambers to monitor the temperature of the inner surface of the insulation chamber.

[0185] Cutting station 21 is located approximately 1.8 meters below the lower end of insulation chamber 31.

[0186] During the continuous production of fused silica ingots with a diameter of 530 mm, the ingots were moved downwards at a rate of 20 mm / h. Under these conditions, thermocouples 32, 33, 34, and 35 on the inner surface of the insulating chamber indicated temperatures >1100°C, 900°C, 750°C, and 430°C, respectively. Thermocouple 32 experienced radiative heating from mods a and d above the chimney region. The ingot surface temperature upon entering the upper annealing chamber was approximately 1100°C, and the ingot surface temperature upon leaving the lower annealing chamber was approximately 520°C. Computer simulations showed a significant reduction in the radial temperature difference Tc-Ts caused by the two annealing chambers, and a corresponding reduction in stress within the ingot.

[0187] In these conditions, the surface temperature of the cutting station is approximately 200°C. Using a saw with a tip inlaid with metal-welded diamond and fed by water at 60°C, the cutting station can repeatedly cut descending ingots into 1000 mm lengths without inducing significant cracking on the ingot surface. Early attempts to cut such large ingots online without the controllable annealing provided by the aforementioned annealing chamber resulted in longitudinal cracks forming in the ingot, and these cracks were found to grow continuously as the ingot descended, rendering the product unacceptable for its intended purpose.

Claims

1. A method for the continuous production of quartz glass ingots having a cross-sectional area of more than 96000 mm 2 2. The method according to claim 1, wherein the quartz glass ingot has a cross-sectional area of more than 120000 mm. a. Provide softened quartz glass material in the crucible or refractory jar; b. The softened quartz glass mass is vertically drawn out via a mold to provide a quartz glass ingot; and c. Cut the quartz glass ingot into specific lengths along a wire. in, Before step c, By drawing air upwards around the ingot as it exits the mold, the quartz glass ingot is first cooled to a surface temperature between 900°C and 1150°C; and The quartz glass ingot is then passed through more than one adiabatic chamber, in which online annealing of the ingot is induced to provide controlled cooling of the ingot. wherein the ingot emerges with a surface temperature of less than 600°C by passing through the at least one thermally insulated chamber, and wherein the ingot has an outer surface temperature T S and a core temperature T C , characterized in that the residence time during the adiabatic period is between 20 hours and 150 hours, wherein the difference between the outer surface temperature T S and the center temperature T C is less than 40°C.

2. The method according to claim 1, characterized in that... The T of the ingot C With T S The difference between them gradually decreases during the adiabatic period due to the internal heat of the decreasing quartz glass ingot.

3. The method according to claim 1 or 2, characterized in that... The quartz glass ingot is cooled to a surface temperature of less than 250°C before cutting.

4. The method according to claim 1 or 2, characterized in that... The surface tensile stress of the quartz glass ingot before cutting in step c. is less than 5 MPa.

5. The method according to claim 1 or 2, characterized in that... The distance between the cutting zone and the die hole along the quartz glass ingot that has been removed from the die hole is less than 4.00 m.

6. A device for performing continuous production of cross-sectional areas greater than 96000 mm² according to any one of claims 1-5. 2 An apparatus for a method of producing quartz glass ingots, the apparatus comprising the following components: (a) A crucible or refractory jar for providing softened quartz glass lumps, the bottom of which has a die hole; (b) A component for vertically drawing out the softened quartz glass mass via a mold to provide a quartz glass ingot; (c) A component used for cutting hollow quartz glass ingots into specific lengths on a wire; (d) The annealed component on the quartz glass ingot line prior to the component (c) cut from the ingot line, and (e) A component that ensures the quartz glass ingot is cooled to a surface temperature between 900°C and 1150°C before insulation. The component used for online annealing provides controlled cooling of the ingot and ensures that the residence time during adiabatic treatment is between 20 and 150 hours, and the outer surface temperature T after adiabatic treatment. S With center temperature T C The difference between them is less than 40°C, wherein the component used for the online annealing is composed of a partition made of one or more insulating materials, the partition surrounding the ingot with a predetermined gap, and wherein the partition is constructed such that it can act as a chimney that allows cooling air to flow upward in a controlled manner around the ingot.

7. The device according to claim 6, characterized in that... The cutting was performed using a saw.

8. A large quartz glass ingot, which can be obtained by the method according to any one of claims 1 to 5.

9. The large quartz glass ingot according to claim 8, characterized in that... The surface tensile stress of the ingot is less than 5 MPa.

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