Melting method of low-expansion quartz glass

Abstract

The invention relates to a melting method of low-expansion quartz glass, and belongs to the technical field of low-expansion quartz glass production. According to the melting method of the low-expansion quartz glass, a mode of overlapping the crucibles for multiple times is adopted, the problem that the production and use requirements of large-size products cannot be met in an existing production method of the low-expansion quartz glass is solved, and the melting method is particularly suitable for the production and use requirements of the large-size low-expansion quartz glass.

Description

Technical Field

[0001] The invention relates to a melting method of low-expansion quartz glass, belonging to the technical field of low-expansion quartz glass production. Background Art

[0002] Common melting methods for low expansion glass include the vertical method and the crucible method. The vertical method is to deposit the raw materials onto the target surface through a burner, and rely on the edge temperature difference to cool and shape. Since the blank shaping during the melting process relies on the temperature difference, resulting in a large temperature difference on the material surface, the stress and thermal expansion (CTE) uniformity of the finished product is poor, and high-quality products tend to use the crucible method. The existing crucible method, such as the invention patent application with application publication number CN117645406A, discloses a method and a production device for low expansion coefficient quartz glass ingots, which deposits the raw materials onto a given crucible through a burner, relies on rotation and free flow to fill the crucible, and relies on the crucible to control the shaping. Since the shaping process does not rely on the temperature difference, the material surface temperature is higher and the overall temperature difference is smaller.

[0003] Although the existing crucible method for producing low-expansion quartz glass meets the use needs to a certain extent, it is necessary to ensure that the target surface at the bottom of the crucible is kept within the range of the burner jet column when it is working. If it is higher than this height, it will affect the discharge of flying materials and heat in the furnace, resulting in material accumulation on the top of the furnace. When the melting time is long, it accumulates into large blocks and drips into the blank, affecting the quality of the blank. However, if it is lower than this height, the height of the melted blank is limited and cannot meet the needs of large-sized products.

[0004] Therefore, it is necessary to develop a new melting method to solve the above problems existing in the existing low expansion quartz glass production method. Summary of the invention

[0005] The purpose of the present invention is to provide a melting method for low-expansion quartz glass to solve the problem that the existing low-expansion quartz glass production method cannot meet the production and use requirements of large-scale products.

[0006] The technical solution of the present invention is: A method for melting low expansion quartz glass, characterized in that: the method for melting low expansion quartz glass comprises the following steps: 1. First, a single crucible is transported to the inside of the furnace through a lifting and rotating mechanism; then the hydrogen-oxygen burner is ignited; the hydrogen-oxygen burner ejects the raw material gas, and at this time, the raw material gas melts at the focus of the hydrogen-oxygen flame to form a jet material column and is deposited in the crucible and deposited in the crucible at a temperature of 1830-1850°C to form a quartz glass body, thereby obtaining the first finished quartz glass ingot.

[0007] 2. The surface temperature of the first finished quartz glass ingot is controlled at 1830-1850° C. by adjusting the gas volume and the exhaust volume; then, the temperature is reduced to 850° C. at a cooling rate of 50° C. / h by controlling the hydrogen-oxygen flame of the hydrogen-oxygen burner and the exhaust system, and the temperature is kept constant for 10 hours, and then the hydrogen-oxygen burner 2 is closed, and the temperature is naturally cooled to form the first rough ingot; in the process of closing the hydrogen-oxygen burner in the said step, the hydrogen-oxygen burners from the center to the edge are gradually stopped.

[0008] 3. After the first ingot cools down to room temperature, the lifting and rotating mechanism drives the crucible and the first ingot to drop out of the furnace. Then the first ingot is taken out and the impurities dropped from the furnace top when the fire is stopped are removed by cutting or grinding the surface of the ingot. After the processing is completed, the blank is immersed in an acid pool containing 10% hydrofluoric acid for 1 hour, rinsed twice with deionized water and dried, the surface is wrapped with dust-free plastic film, and the film is removed after being transferred to the crucible to obtain the processed blank.

[0009] 4. Place a second crucible on top of the crucible in step 1; then place the blank processed in step 3 into the stacked crucibles; then lift and rotate the mechanism 7 to slowly raise the crucible and the processed blank to the outer flame of the oxyhydrogen burner 2 for flame throwing, so as to create a smooth raw material deposition surface with suitable temperature and improve the deposition rate.

[0010] 5. When the temperature of the lump surface rises to 1850-1880℃, the lifting and rotating mechanism quickly rises at 500mm / h to within the injection range of 150-200mm of the oxyhydrogen burner 2, and the normal melting gas volume is restored. The ratio of hydrogen and oxygen is ≥2, and the escaped hydrogen is used to ensure that the overall melting temperature of the furnace 1 rises; after the lump surface temperature rises to 1850-1880℃, the material is started to be unloaded, and the material amount is gradually increased to a stable amount over time.

[0011] 6. After melting step 4 normally until the crucible is full, repeat steps 1, 2, 3 and 4, and so on. Repeat this process three to four times to obtain large-sized low-expansion quartz glass products. If the process is repeated more than five times, excessive stress and crystal cracking may occur.

[0012] The advantages of the present invention are: The low-expansion quartz glass melting method adopts a method of stacking crucibles multiple times, which solves the problem that the existing low-expansion quartz glass production method cannot meet the production and use requirements of large-size products, and is particularly suitable for the production and use requirements of large-size low-expansion quartz glass. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the first deposition of the present invention; Figure 2 This is a schematic diagram of the second deposition structure of the present invention; Figure 3 It is a schematic diagram of the multiple deposition structure of the present invention.

[0014] In the figure: 1. furnace; 2. hydrogen-oxygen burner; 3. crucible; 4. injection column; 5. flame; 6. deposition surface; 7. lifting and rotating mechanism. DETAILED DESCRIPTION

[0015] The melting method of the low expansion quartz glass comprises the following steps: 1. First, a single crucible 3 is transported to the interior of the furnace 1 by the lifting and rotating mechanism 7; then the hydrogen-oxygen burner 2 is ignited; the hydrogen-oxygen burner 2 ejects the raw material gas, and at this time, the raw material gas melts at the focus of the hydrogen-oxygen flame to form a jet material column 4 and is deposited in the crucible at a temperature of 1830-1850° C. to form a quartz glass body, thereby obtaining the first finished quartz glass ingot; It is a one-step molding process, where the raw materials are directly hydrolyzed to form silicon dioxide / titanium dioxide nanoparticles, which are then aggregated to form glass. The deposition temperature needs to be controlled at 1830-1850°C. The height of the crucible is between 50-70mm.

[0016] 2. Control the lump surface temperature of the first finished quartz glass ingot at 1830-1850℃ by adjusting the gas volume and exhaust volume (the lump surface temperature is controlled by adjusting the gas volume and exhaust volume, the gas volume adjustment can control the total combustion heat, and the exhaust volume can control the exhaust heat); then, control the hydrogen-oxygen flame of the hydrogen-oxygen burner 2 and the exhaust system to reduce the lump surface temperature to 850℃ at a cooling rate of 50℃ / h, keep the temperature constant for 10h, and then gradually turn off the hydrogen-oxygen burner 2 from the center to the edge, and naturally cool down to form the first rough ingot. The purpose of releasing internal stress during the constant temperature process in this step is to prevent the rough crystal cracking from affecting the next melting; The purpose of gradually stopping the firing of the oxyhydrogen burners 2 from the center to the edge during the process of shutting down the oxyhydrogen burners 2 is that during the process of lowering the lump surface temperature, the temperature gradually decreases from the center to the edge. By gradually stopping the firing of the oxyhydrogen burners 2 from the center to the edge during the process of shutting down the oxyhydrogen burners 2, the lump surface temperature is ensured to decrease evenly during the cooling process.

[0017] 3. After the first rough ingot is cooled to room temperature, the lifting and rotating mechanism 7 drives the crucible 3 and the first rough ingot to descend out of the furnace 1, and then the first rough ingot is taken out and the impurities dropped from the furnace top during the shutdown are removed by cutting or grinding the surface of the rough ingot. After the processing is completed, the rough ingot is immersed in an acid pool containing 10% hydrofluoric acid for 1 hour, rinsed twice with deionized water, and dried, and the surface is wrapped with a dust-free plastic film; The purpose of using hydrofluoric acid treatment is to remove metal impurities introduced during the processing and prevent crystallization.

[0018] 4. Place a second crucible on top of the crucible 3 in step 1; then place the blank with the film removed after processing in step 3 into the stacked crucible 3; then lift and rotate the crucible 3 together with the processed blank to the outer flame of the oxyhydrogen burner 2 for flame throwing, so as to create a smooth raw material deposition surface with suitable temperature and improve the deposition rate; In order to prevent the lump surface from cracking due to sudden temperature rise due to rising too fast, it must rise slowly to the specified height (outer flame) at a speed of 20mm / h; during the process, the ratio of hydrogen and oxygen must be less than 2 to ensure that the deposition surface is in an oxidizing environment. If the ratio of hydrogen and oxygen is ≥2, that is, in a reducing environment, the titanium on the surface of the docking layer will change from tetravalent to trivalent, showing a blue stratification.

[0019] 5. When the temperature of the lump surface rises to 1850-1880℃, the lifting and rotating mechanism 7 quickly rises at 500mm / h to the injection range of the hydrogen-oxygen burner 2 (i.e., the distance from the hydrogen-oxygen burner 2 to the lump surface) within 150-200mm, and restores the normal melting gas volume, the hydrogen-oxygen ratio is ≥2, and the escaped hydrogen is used to ensure that the overall melting temperature of the furnace 1 rises; after the lump surface temperature rises to 1850-1880℃, the material is started to be unloaded, and the material amount gradually increases over time to a stable amount. The reason why the hydrogen-oxygen ratio is ≥2 is partly because the escaped hydrogen is used to increase the overall furnace temperature, so that the overall temperature in the furnace rises, and assists in homogenizing the lump surface temperature.

[0020] 6. After melting step 4 normally until the crucible is full, repeat steps 1, 2, 3 and 4, and so on. Repeat this process three to four times to obtain large-sized low-expansion quartz glass products. If the process is repeated more than five times, excessive stress and crystal cracking may occur.

[0021] The low-expansion quartz glass melting method adopts a method of stacking crucibles multiple times, which solves the problem that the existing low-expansion quartz glass production method cannot meet the production and use requirements of large-size products, and is particularly suitable for the production and use requirements of large-size low-expansion quartz glass.

Claims

1. A method for melting low expansion quartz glass, characterized in that: The method for melting low expansion quartz glass comprises the following steps:

1. First, a single crucible (3) is transported to the interior of a furnace (1) by a lifting and rotating mechanism (7); then, a hydrogen-oxygen burner (2) is ignited; the hydrogen-oxygen burner (2) ejects the raw material gas, and at this time, the raw material gas melts at the focus of the hydrogen-oxygen flame to form a jet material column (4) and is deposited in the crucible at a temperature of 1830-1850° C. to form a quartz glass body, thereby obtaining a first finished quartz glass ingot; 2. The surface temperature of the first finished quartz glass ingot is controlled at 1830-1850° C. by adjusting the gas volume and the exhaust volume; then, the temperature is lowered to 850° C. at a rate of 50° C. / h by controlling the hydrogen-oxygen flame of the hydrogen-oxygen burner (2) and the exhaust system, and the temperature is kept constant for 10 hours, and then the hydrogen-oxygen burner (2) is turned off and the temperature is naturally lowered to form the first rough ingot; 3. After the first rough ingot has cooled to room temperature, the lifting and rotating mechanism (7) drives the crucible (3) and the first rough ingot to descend out of the furnace (1), and then the first rough ingot is taken out and the impurities dropped from the furnace top when the fire is stopped are removed by cutting or grinding the surface of the rough ingot. After the processing is completed, the rough ingot is immersed in an acid bath containing 10% hydrofluoric acid for 1 hour, and then rinsed twice with deionized water and dried, and the surface is wrapped with a dust-free plastic film; 4. Place a second crucible (3) on top of the crucible (3) in step 1; then remove the film from the blank processed in step 3 and place it in the stacked crucible (3); then use the lifting and rotating mechanism (7) to slowly raise the crucible (3) together with the processed blank to the outer flame of the oxyhydrogen burner (2) for flame throwing, thereby creating a smooth raw material deposition surface with a suitable temperature and improving the deposition rate; 5. When the temperature of the lump surface rises to 1850-1880°C, the lifting and rotating mechanism (7) is quickly raised at 500mm / h to the injection range of the hydrogen-oxygen burner (2), and the normal melting gas volume is restored, with the hydrogen-oxygen ratio ≥ 2, and the escaped hydrogen is used to ensure that the overall melting temperature of the furnace (1) rises; after the lump surface temperature rises to 1850-1880°C, the material is started to be discharged, and the material amount is gradually increased over time to a stable material amount; 6. After melting step 5 normally until the crucible is full, repeat steps 1, 2, 3, 4 and 5, and so on, and repeat for multiple times to obtain large-sized low-expansion quartz glass products.

2. The method for melting low expansion quartz glass according to claim 1, characterized in that: In the process of shutting down the hydrogen-oxygen burner (2) in step 2, the hydrogen-oxygen burners (2) from the center to the edge are gradually stopped.

3. The method for melting low expansion quartz glass according to claim 1, characterized in that: The height of the crucible (3) is between 50 and 70 mm.

4. The method for melting low expansion quartz glass according to claim 1, characterized in that: In step 4, the crucible (3) together with the processed blank is slowly raised to the outer flame of the oxyhydrogen burner (2) at a speed of 20 mm / h; during this process, the ratio of hydrogen to oxygen must be less than 2.

5. The method for melting low expansion quartz glass according to claim 1, characterized in that: The spray range of the oxyhydrogen burner (2) refers to the distance between the nozzle of the oxyhydrogen burner (2) and the surface of the lump surface being between 150 and 200 mm.

6. The method for melting low expansion quartz glass according to claim 1, characterized in that: The steps in step 6 can be repeated three to four times.

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