Melting method for reducing microbubbles on inner surface layer of quartz crucible

Abstract

The invention relates to the technical field of quartz crucibles, and particularly discloses a melting method for reducing microbubbles on the inner surface layer of a quartz crucible. The arc vacuum melting in the melting method disclosed by the invention comprises the following steps of: rising a heat shielding plate to a position which is 350-450mm away from the upper edge of a mold, and melting the inner surface of a crucible for 45-75s by utilizing a high current which is more than 5000A; then moving down the heat shielding plate, keeping the current unchanged, and melting; the heat shielding plate is lifted, the current is adjusted to be 2200-2500 A, and a transparent layer is formed through vacuum melting; stable melting: adjusting the current to be more than 5000A, and performing high-temperature evaporation; then, the current is adjusted to be reduced to 1800-2200 A, and low-temperature melting is conducted for 120-240 s; and repeating stable melting to obtain the quartz crucible to be demoulded. By means of the technical scheme, the number of microbubbles of the prepared quartz crucible is obviously reduced, the compression strength of the crucible is greatly improved, and the service life of the crucible is greatly prolonged.

Description

Technical Field

[0001] This application relates to the technical field of quartz crucibles, and specifically relates to a melting method for reducing microbubbles on the inner surface layer of quartz crucibles. Background Technique

[0002] A quartz crucible is a vessel made of high-purity quartz sand. This material has the advantages of high purity, strong heat resistance, high dimensional accuracy, good heat preservation, etc., and has various technical characteristics and wide applications.

[0003] Quartz crucibles are widely used in the photovoltaic industry to contain molten silicon and form silicon ingots, and are important containers for refining crystalline silicon. In the semiconductor industry, quartz crucibles are also used to grow semiconductor single crystals for manufacturing integrated circuits and microelectronic devices, etc. With the rapid development of the photovoltaic and semiconductor industries, the demand for quartz crucibles is increasing continuously. As a vessel with high technical content, quartz crucibles play an important role in the photovoltaic and semiconductor industries.

[0004] In the production process of quartz crucibles, the quartz sand forms the shape and size of the crucible through specific forming methods (such as extrusion forming or injection molding), and then is formed through high-temperature melting. At present, one of the defects in quartz crucible melting is that the number of microbubbles is abnormally large. Microbubbles will cause the quartz crucible to expand and rupture during the crystal pulling process, thus affecting the crystal pulling quality, reducing the single output of the pulled silicon rod and the service life of the quartz crucible. Summary of the Invention

[0005] In order to solve the above technical problems, this application provides a melting method for reducing microbubbles on the inner surface layer of quartz crucibles.

[0006] This application provides a melting method for reducing microbubbles on the inner surface layer of quartz crucibles, which specifically includes the following steps in sequence: batching, cloth laying, forming rod forming, arc vacuum melting, and demolding to obtain a quartz crucible blank; The specific steps of the arc vacuum melting are as follows: Surface layer vacuum melting: Raise the heat shield to a position 350 - 450 mm away from the upper edge of the mold, start arc ignition at a high position, and use a high current of more than 5000 A to melt the inner surface of the crucible for 45 - 75 s; then move the heat shield downward to a position 140 - 160 mm away from the upper edge of the mold, keep the high current of more than 5000 A unchanged, and melt for 100 - 140 s to enable the inner surface layer of the crucible to be vacuum melted and fully sealed, with a vacuum degree greater than -0.09 Mpa; Middle layer vacuum melting: Raise the heat shield to a position 350 - 450 mm away from the upper edge of the mold, adjust the current to 2200 A - 2500 A, and melt for 10 min - 12 min to slowly melt in a vacuum to form a transparent layer; Stable melting: Adjust the current to above 5000 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 120 - 180 s; then adjust the current to drop to 1800 - 2200 A, and perform low-temperature melting on the crucible for 120 - 240 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0007] In the technical solution provided by this application, during the preliminary surface layer vacuum melting process, starting the arc at a high position can effectively reduce the melting influence caused by spraying materials, such as the generation of defective conditions like small bubbles and bubble bands; during the middle layer vacuum melting process, since the proportion of the middle layer materials with a particle size ≥ 300 μm is much larger than that of the inner layer materials with a particle size ≥ 300 μm, the middle layer materials are coarser in particle size relative to the inner layer materials, that is, the generation of interstitial bubbles between the particle sizes is more serious. It is necessary to select a lower current for melting for an appropriate time to fully evacuate the microbubbles in the transparent layer, which can effectively reduce the number of microbubbles; during the stable melting process, first use a high current to perform high-temperature evaporation on the inner surface of the quartz crucible, which can further effectively remove microbubbles and impurities, etc. The time of this high-temperature evaporation cannot be too long to prevent the viscosity of the molten quartz sand in the molten state after melting from decreasing due to continuous high temperature, resulting in the inner surface layer raw materials sliding down from the upper opening, thus causing the lack of the transparent layer formed by the inner layer quartz sand at the upper opening. Then use a lower current for low-temperature melting and repeat the stable melting step once, which can further improve the performance of the quartz crucible.

[0008] Preferably, the specific steps of the surface layer vacuum melting are: Raise the heat shield to a position 380 - 420 mm away from the upper edge of the mold, start the arc at a high position, and melt the inner surface of the crucible for 50 - 70 s with a high current having a current parameter of 5200 - 5700 A; then move the heat shield downward to a position 145 - 155 mm away from the upper edge of the mold, keep the high current unchanged, and melt for 110 - 130 s to perform vacuum melting on the inner surface layer of the crucible and fully seal it, with a vacuum degree greater than -0.09 Mpa.

[0009] Preferably, the specific steps of the middle layer vacuum melting are: Raise the heat shield to a position 380 - 420 mm away from the upper edge of the mold, adjust the current to 2300 A - 2400 A, and melt for 10 min - 12 min to slowly melt under vacuum to form a transparent layer; Preferably, the specific steps of the stable melting are: Adjust the current to 5200 - 5700 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 140 - 160 s; then adjust the current to drop to 1900 - 2100 A, and perform low-temperature melting on the crucible for 160 - 200 s.

[0010] Preferably, during the arc vacuum melting process, the rotation speed of the mold is 60 - 70 rpm.

[0011] Preferably, during the arc vacuum melting process, the rotation speed of the mold is 61 - 65 rpm.

[0012] During the arc vacuum melting process of this application, by controlling the rotation speed of the mold within the above range, the quartz sand forming material can be vacuum melted under the optimal centrifugal force, avoiding the loss or outward throwing of raw materials due to too small or too large centrifugal force. Furthermore, the heat - receiving uniformity of the raw material melting can be effectively improved, thereby preventing the defect of an increase in the number of micro - bubbles, and at the same time ensuring that the pressure - bearing strength and service life of the quartz crucible are effectively improved.

[0013] Preferably, the ingredients of the quartz crucible are composed of the following components by weight: 17 - 21 parts of inner - layer material, 46 - 50 parts of middle - layer material, and 47 - 53 parts of outer - layer material; The inner - layer material is composed of quartz sand with a particle size <50μm, quartz sand with a particle size of 50 - 100μm, quartz sand with a particle size of 100 - 200μm, quartz sand with a particle size of 200 - 300μm, and quartz sand with a particle size >300μm in a weight ratio of 10 - 12:25 - 35:55 - 65:15 - 20:0.5 - 1; The middle - layer material is composed of quartz sand with a particle size <100μm, quartz sand with a particle size of 100 - 200μm, quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size >500μm in a weight ratio of 20 - 25:50 - 60:40 - 50:10 - 20:2 - 5:0.5 - 1; The outer - layer material is composed of quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size >500μm in a weight ratio of 30 - 35:15 - 20:2 - 6:0.5 - 1.

[0014] Through experimental analysis, it can be known that when the ingredients of the quartz crucible are accurately selected as the above - mentioned scheme in this application, the comprehensive performance of the quartz crucible can be further improved; the quartz sand in the inner - layer material has a relatively small particle size and high purity, which can reduce the content of tiny bubbles in the transparent layer. The quartz sand in the middle - layer material and the outer - layer material has a relatively large particle size and low purity, which can reduce the raw material cost while ensuring the product quality, and at the same time improve the comprehensive performance of the quartz crucible.

[0015] Preferably, the size of the quartz crucible blank is 36 inches.

[0016] In the second aspect, this application provides a quartz crucible prepared by using the above - mentioned melting process.

[0017] In the third aspect, this application provides an application of a quartz crucible in the refining of crystalline silicon.

[0018] In summary, the technical solution of the present application has the following effects: In the arc vacuum melting technical solution provided by the present application, by continuously changing the distance between the heat shield and the upper edge of the mold and the melting current and time, the raw materials in the crucible can be uniformly heated, reducing the generation of microbubbles and impurities in the quartz crucible. As a result, the number of microbubbles in the quartz crucible is significantly reduced, and the pressure resistance and service life of the crucible are greatly improved.

[0019] In the technical solution of the present application, by screening suitable ingredients and performing arc vacuum melting at a suitable mold rotation speed, and then cooperating with the corresponding arc vacuum melting, the performance of the quartz crucible is further improved. Specific Embodiments

[0020] The present application will be further described in detail below in conjunction with examples, comparative examples, and performance detection tests. These examples should not be construed as limiting the scope claimed by the present application. Examples

[0021] Example 1 Example 1 provides a quartz crucible and a melting method for reducing microbubbles on the inner surface layer of the quartz crucible.

[0022] The preparation method of the quartz crucible in this example is as follows: (1) Ingredients: The quartz sand raw materials are specifically 19 kg of inner layer material, 48 kg of middle layer material, and 50 kg of outer layer material; the raw materials in different positions are divided into barrels for packaging; The inner layer material consists of quartz sand with a particle size <50μm, quartz sand with a particle size of 50 - 100μm, quartz sand with a particle size of 100 - 200μm, quartz sand with a particle size of 200 - 300μm, and quartz sand with a particle size >300μm in a weight ratio of 11:30:60:17:0.8; the middle layer material consists of quartz sand with a particle size <100μm, quartz sand with a particle size of 100 - 200μm, quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size >500μm in a weight ratio of 22:55:45:15:3:0.8; The outer layer material consists of quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size >500μm in a weight ratio of 32:17:4:0.8.

[0023] The prepared raw material formula is loaded into barrels numbered 1-9 according to the middle layer, inner layer and outer layer raw materials. Barrel No. 1 uses straight-wall outer layer material, barrels No. 2 and 3 use straight-wall outer layer material, barrels No. 4 and 5 use straight-wall middle layer material, barrel No. 6 uses straight-wall inner layer material, barrel No. 7 uses bottom outer layer material, barrel No. 8 uses bottom middle layer material, and barrel No. 9 uses bottom inner layer material.

[0024] (2) Fabric: Use a fabric shovel to spread the raw materials evenly on the inner wall of the mold according to the barrel number.

[0025] (3) Molding rod molding: Use the planned outer, middle and inner molding rods to flatten and shape the outer, middle and inner raw materials respectively, and perform rotation molding at a speed of 63 rpm. The centrifugal force generated by the rotation of the mold is used to shape the quartz sand into a crucible blank.

[0026] (4) Arc vacuum melting: Surface vacuum melting: Raise the heat shield to a distance of 400 mm from the upper edge of the mold, start the arc at a high position, and melt the inner surface of the crucible with a high current of 5500 A for 60 seconds; then move the heat shield downward to a distance of 150 mm from the upper edge of the mold, maintain the high current of 5500 A unchanged, and melt for 120 seconds to vacuum melt the inner surface of the crucible and fully seal it, with a vacuum degree greater than -0.09 MPa; Middle layer vacuum melting: Since the proportion of the middle layer material with a particle size of ≥300μm is much larger than that of the inner layer material with a particle size of ≥300μm, the middle layer material is coarser than the inner layer material, that is, the bubbles between the particles are more serious. Raise the heat shield to a distance of 400mm from the upper edge of the mold, adjust the current to 2300A, melt for 11 minutes, and slowly melt in vacuum to form a transparent layer, so that the microbubbles in the transparent layer are fully extracted, which can effectively reduce the number of microbubbles; Stable melting: Adjust the current to 5500A and evaporate the inner surface of the quartz crucible (microbubbles and impurities, etc.) at high temperature for 150 seconds. The time should not be too long to prevent the continued high temperature from reducing the viscosity of the molten quartz sand, causing the inner surface material to slide down from the upper mouth, resulting in the lack of the transparent layer formed by the inner quartz sand at the upper mouth. Then adjust the current to 2000A and melt the crucible at low temperature for 180 seconds. Repeat the stable melting step once to obtain a quartz crucible to be demolded.

[0027] (5) Demolding: Keep the melting mold speed at 63 rpm, allow the crucible blank to cool naturally, and then demold it under the action of high-pressure airflow and knocking vibration; After checking that the quartz crucible has no defects such as cracks, bubbles, and black spots, sandblasting and cutting operations are carried out; further testing of various indicators of the quartz crucible is carried out, and if qualified, cleaning, drying, packaging, etc. are carried out to obtain a 36-inch quartz crucible finished product (specific specifications are height, outer diameter, and thickness).

[0028] Example 2-5 Examples 2-5 respectively provide a quartz crucible and a melting method for reducing micro-bubbles on the inner surface layer of the quartz crucible.

[0029] The differences between the above examples and Example 1 are as follows: the batching is different, as shown below.

[0030] In Example 2: the inner layer material consists of quartz sand with a particle size <50μm, quartz sand with a particle size of 50-100μm, quartz sand with a particle size of 100-200μm, quartz sand with a particle size of 200-300μm, and quartz sand with a particle size >300μm, with a weight ratio of 10:35:55:20:0.5; The middle layer material consists of quartz sand with a particle size <100μm, quartz sand with a particle size of 100-200μm, quartz sand with a particle size of 200-300μm, quartz sand with a particle size of 300-400μm, quartz sand with a particle size of 400-500μm, and quartz sand with a particle size >500μm, with a weight ratio of 20:60:40:20:2:1; The outer layer material consists of quartz sand with a particle size of 200-300μm, quartz sand with a particle size of 300-400μm, quartz sand with a particle size of 400-500μm, and quartz sand with a particle size >500μm, with a weight ratio of 30:20:2:0.5.

[0031] In Example 3: the inner layer material consists of quartz sand with a particle size <50μm, quartz sand with a particle size of 50-100μm, quartz sand with a particle size of 100-200μm, quartz sand with a particle size of 200-300μm, and quartz sand with a particle size >300μm, with a weight ratio of 12:25:65:15:1; The middle layer material consists of quartz sand with a particle size <100μm, quartz sand with a particle size of 100-200μm, quartz sand with a particle size of 200-300μm, quartz sand with a particle size of 300-400μm, quartz sand with a particle size of 400-500μm, and quartz sand with a particle size >500μm, with a weight ratio of 25:50:50:10:5:0.5; The outer layer material consists of quartz sand with a particle size of 200-300μm, quartz sand with a particle size of 300-400μm, quartz sand with a particle size of 400-500μm, and quartz sand with a particle size >500μm, with a weight ratio of 35:15:6:1.

[0032] In Example 4: the inner layer material consists of quartz sand with a particle size <50μm, quartz sand with a particle size of 50-100μm, quartz sand with a particle size of 100-200μm, quartz sand with a particle size of 200-300μm, and quartz sand with a particle size >300μm, with a weight ratio of 8:40:50:25:0.1; The middle layer material is composed of quartz sands with particle sizes < 100μm, 100 - 200μm, 200 - 300μm, 300 - 400μm, 400 - 500μm, and > 500μm in a weight ratio of 15:65:35:25:8:0.1; The outer layer material is composed of quartz sands with particle sizes 200 - 300μm, 300 - 400μm, 400 - 500μm, and > 500μm in a weight ratio of 25:25:1:2.

[0033] In Example 5: The inner layer material is composed of quartz sands with particle sizes < 50μm, 50 - 100μm, 100 - 200μm, 200 - 300μm, and > 300μm in a weight ratio of 15:20:70:10:2; The middle layer material is composed of quartz sands with particle sizes < 100μm, 100 - 200μm, 200 - 300μm, 300 - 400μm, 400 - 500μm, and > 500μm in a weight ratio of 30:40:60:5:1:3; The outer layer material is composed of quartz sands with particle sizes 200 - 300μm, 300 - 400μm, 400 - 500μm, and > 500μm in a weight ratio of 40:10:10:0.1.

[0034] In the above - mentioned examples, other process parameters are the same as those in Example 1.

[0035] Examples 6 - 9 Examples 6 - 9 respectively provide a quartz crucible and a melting method for reducing micro - bubbles on the inner surface layer of the quartz crucible.

[0036] The differences between the above - mentioned examples and Example 1 are as follows: The process parameters of arc vacuum melting are different, as shown specifically below.

[0037] In Example 6: Surface vacuum melting: Raise the heat - shield to a distance of 350mm from the upper edge of the mold, start arc ignition at a high position, and melt the inner surface of the crucible for 45s using a high current of 6000A; then move the heat - shield down to a position 160mm from the upper edge of the mold, keep the high current of 6000A unchanged, and melt for 100s to enable surface vacuum melting of the crucible and full sealing treatment, with the vacuum degree greater than - 0.09Mpa; Middle - layer vacuum melting: Raise the heat shield to a position 350 mm away from the upper edge of the mold, adjust the current to 2000 A, and melt for 12 minutes. Slowly melt in a vacuum to form a transparent layer; Stable melting: Adjust the current to 6000 A, perform high - temperature evaporation on the inner surface of the quartz crucible for 120 s; then adjust the current to 2200 A and perform low - temperature melting on the crucible for 120 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0038] In Example 7: Surface - layer vacuum melting: Raise the heat shield to a position 450 mm away from the upper edge of the mold, perform high - voltage arcing, and melt the inner surface of the crucible with a high current of 5000 A for 75 s; then move the heat shield down to a position 140 mm away from the upper edge of the mold, keep the high current of 5000 A unchanged, and melt for 140 s to perform surface - layer vacuum melting of the crucible and fully seal it, with the vacuum degree greater than - 0.09 Mpa; Middle - layer vacuum melting: Raise the heat shield to a position 450 mm away from the upper edge of the mold, adjust the current to 2500 A, and melt for 10 minutes. Slowly melt in a vacuum to form a transparent layer; Stable melting: Adjust the current to 5000 A, perform high - temperature evaporation on the inner surface of the quartz crucible for 180 s; then adjust the current to 1800 A and perform low - temperature melting on the crucible for 240 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0039] In Example 8: Surface - layer vacuum melting: Raise the heat shield to a position 380 mm away from the upper edge of the mold, perform high - voltage arcing, and melt the inner surface of the crucible with a high current of 5200 A for 70 s; then move the heat shield down to a position 145 mm away from the upper edge of the mold, keep the high current of 5200 A unchanged, and melt for 130 s to perform surface - layer vacuum melting of the crucible and fully seal it, with the vacuum degree greater than - 0.09 Mpa; Middle - layer vacuum melting: Raise the heat shield to a position 380 mm away from the upper edge of the mold, adjust the current to 2400 A, and melt for 10 minutes. Slowly melt in a vacuum to form a transparent layer; Stable melting: Adjust the current to 5200 A, perform high - temperature evaporation on the inner surface of the quartz crucible for 160 s; then adjust the current to 1900 A and perform low - temperature melting on the crucible for 200 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0040] In Example 9: Surface vacuum melting: Raise the heat shield to a distance of 420 mm from the upper edge of the mold, start the arc at a high position, and melt the inner surface of the crucible for 50 s with a high current of 5700 A; then move the heat shield downward to a distance of 155 mm from the upper edge of the mold, keep the high current of 5700 A unchanged, and melt for 140 s to perform surface vacuum melting of the crucible and fully seal it, with the vacuum degree greater than -0.09 Mpa; Middle layer vacuum melting: Raise the heat shield to a distance of 420 mm from the upper edge of the mold, adjust the current to 2300 A, and melt for 12 min to slowly melt and form a transparent layer in a vacuum; Stable melting: Adjust the current to 5700 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 140 s; then adjust the current to drop to 2100 A, and perform low-temperature melting on the crucible for 160 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0041] Other process parameters in the above examples are the same as those in Example 1.

[0042] Examples 10 - 11 Examples 10 - 11 respectively provide a quartz crucible and a melting method for reducing microbubbles on the inner surface layer of the quartz crucible.

[0043] The differences between the above examples and Example 1 are as follows: The process parameters of arc vacuum melting are different, as specifically shown below.

[0044] In Example 10: During the arc vacuum melting process, the rotation speed of the mold is 55 rpm.

[0045] In Example 11: During the arc vacuum melting process, the rotation speed of the mold is 75 rpm.

[0046] Other process parameters in the above examples are the same as those in Example 1.

[0047] Comparative examples Comparative examples 1 - 3 Comparative examples 1 - 3 respectively provide a quartz crucible and a melting method for reducing microbubbles on the inner surface layer of the quartz crucible.

[0048] The differences between the above comparative examples and Example 1 are specifically as shown below.

[0049] In Comparative Example 1: The process parameters of arc vacuum melting are as follows: Surface vacuum melting: Raise the heat shield to a distance of 300 mm from the upper edge of the mold, initiate an arc at a high position, and melt the inner surface of the crucible for 120 s with a high current of 4200 A; then move the heat shield downward to a distance of 180 mm from the upper edge of the mold, keep the high current of 4200 A unchanged, and melt for 180 s to perform surface vacuum melting of the crucible and fully seal it, with the vacuum degree greater than -0.09 Mpa; Middle layer vacuum melting: Raise the heat shield to a distance of 300 mm from the upper edge of the mold, adjust the current to 2800 A, and melt for 8 min to slowly melt and form a transparent layer in a vacuum; Stable melting: Adjust the current to 4200 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 240 s; then adjust the current to drop to 2400 A and perform low-temperature melting on the crucible for 90 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

[0050] In Comparative Example 2: The process parameters of arc vacuum melting are as follows: Surface vacuum melting: Raise the heat shield to a distance of 600 mm from the upper edge of the mold, initiate an arc at a high position, and melt the inner surface of the crucible for 60 s with a high current of 5500 A; then move the heat shield downward to a distance of 120 mm from the upper edge of the mold, keep the high current of 5500 A unchanged, and melt for 180 s to perform surface vacuum melting of the crucible and fully seal it, with the vacuum degree greater than -0.09 Mpa; Middle layer vacuum melting: Raise the heat shield to a distance of 600 mm from the upper edge of the mold, adjust the current to 1500 A, and melt for 15 min to slowly melt and form a transparent layer in a vacuum; Stable melting: Adjust the current to 5500 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 90 s; then adjust the current to drop to 1500 A and perform low-temperature melting on the crucible for 300 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded In Comparative Example 3: In the process parameters of arc vacuum melting: The stable melting step is not repeated.

[0051] In the above comparative examples, other process parameters are the same as those in Example 1.

[0052] Performance detection test Take the quartz crucibles of Examples 1 - 11 and Comparative Examples 1 - 3 as the detection objects, and test the performance of bulk density, apparent porosity, flexural strength, and compressive strength.

[0053] (1) Number of microbubbles: Use the crucible microbubble quantity measuring instrument to measure the number of microbubbles at different depths (0 mm, 1 mm, 3 mm) at the straight wall, R corner, and bottom position of the crucible respectively, and finally calculate the average value of the measurement values at the straight wall, R corner, and bottom position.

[0054] (2) Compressive strength: Test according to GB / T 5072-2008 "Test Method for Cold Crushing Strength of Refractory Materials".

[0055] (3) Test method for crucible life: Record the final time when the crucible is directly put into the furnace for use.

[0056] Test results: As shown in Table 1.

[0057] Table 1 Performance test results of fused silica crucibles in Examples 1-11 and Comparative Examples 1-3 Combined with Table 1, by comparing the test results of the examples and the comparative examples, compared with the traditional process, using the technical solution of this application, by improving the vacuum melting process, the number of microbubbles in the prepared fused silica crucible is significantly reduced, and the compressive strength and service life of the crucible are greatly improved.

[0058] Although the present invention has been described in detail above with general descriptions and specific embodiments, on the basis of the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. A melting method for reducing micro-bubbles on the inner surface layer of a quartz crucible, characterized in that, Specifically, it includes the following steps in sequence: batching, feeding, forming rod forming, arc vacuum melting, and demolding to obtain a quartz crucible blank; The specific steps of the arc vacuum melting are as follows: Surface vacuum melting: Raise the heat shield to a position 350 - 450 mm away from the upper edge of the mold, initiate an arc at a high position, and melt the inner surface of the crucible for 45 - 75 s using a high current with a current parameter of over 5000 A; then move the heat shield downward to a position 140 - 160 mm away from the upper edge of the mold, keep the high current above 5000 A unchanged, and melt for 100 - 140 s to perform surface vacuum melting of the crucible and fully seal it, with a vacuum degree greater than -0.09 Mpa; Middle layer vacuum melting: Raise the heat shield to a position 350 - 450 mm away from the upper edge of the mold, adjust the current to 2200 A - 2500 A, and melt for 10 min - 12 min to slowly melt and form a transparent layer in a vacuum; Stable melting: Adjust the current to above 5000 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 120 - 180 s; then adjust the current to drop to 1800 - 2200 A and perform low-temperature melting on the crucible for 120 - 240 s; Repeat the stable melting step once to obtain the quartz crucible to be demolded.

2. The melting method for reducing micro-bubbles in the inner surface layer of a quartz crucible according to claim 1, characterized in that, The specific steps of the surface vacuum melting are as follows: Raise the heat shield to a position 380 - 420 mm away from the upper edge of the mold, initiate an arc at a high position, and melt the inner surface of the crucible for 50 - 70 s using a high current with a current parameter of 5200 - 5700 A; then move the heat shield downward to a position 145 - 155 mm away from the upper edge of the mold, keep the high current unchanged, and melt for 110 - 130 s to perform surface vacuum melting of the crucible and fully seal it, with a vacuum degree greater than -0.09 Mpa.

3. The melting method for reducing microbubbles on the inner surface layer of a quartz crucible according to claim 1, characterized in that, The specific steps of the middle layer vacuum melting are as follows: Raise the heat shield to a position 380 - 420 mm away from the upper edge of the mold, adjust the current to 2300 A - 2400 A, and melt for 10 min - 12 min to slowly melt and form a transparent layer in a vacuum.

4. The melting method for reducing micro-bubbles in the inner surface layer of a quartz crucible according to claim 1, characterized in that, The specific steps of the stable melting are as follows: Adjust the current to 5200 - 5700 A, perform high-temperature evaporation on the inner surface of the quartz crucible for 140 - 160 s; then adjust the current to drop to 1900 - 2100 A and perform low-temperature melting on the crucible for 160 - 200 s.

5. The melting method for reducing micro-bubbles on the inner surface layer of a quartz crucible according to claim 1, characterized in that During the arc vacuum melting process, the rotation speed of the mold is 60 - 70 rpm.

6. The melting method for reducing micro-bubbles on the inner surface layer of a quartz crucible according to claim 5, characterized in that, During the arc vacuum melting process, the rotation speed of the mold is 61 - 65 rpm.

7. The melting method for reducing micro-bubbles in the inner surface layer of a quartz crucible according to claim 1, characterized in that, The batching of the quartz crucible consists of the following components by weight: 17 - 21 parts of inner layer material, 46 - 50 parts of middle layer material, and 47 - 53 parts of outer layer material; The inner layer material consists of quartz sand with a particle size <50 μm, quartz sand with a particle size of 50 - 100 μm, quartz sand with a particle size of 100 - 200 μm, quartz sand with a particle size of 200 - 300 μm, and quartz sand with a particle size >300 μm in a weight ratio of 10 - 12:25 - 35:55 - 65:15 - 20:0.5 - 1; The middle layer material is composed of quartz sand with a particle size < 100μm, quartz sand with a particle size of 100 - 200μm, quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size > 500μm, with a weight ratio of 20 - 25:50 - 60:40 - 50:10 - 20:2 - 5:0.5 - 1; The outer layer material is composed of quartz sand with a particle size of 200 - 300μm, quartz sand with a particle size of 300 - 400μm, quartz sand with a particle size of 400 - 500μm, and quartz sand with a particle size > 500μm, with a weight ratio of 30 - 35:15 - 20:2 - 6:0.5 - 1.

8. The melting method for reducing microbubbles on the inner surface layer of a quartz crucible according to claim 1, characterized in that, The size of the quartz crucible blank is 36 inches.

9. A quartz crucible, characterized in that, It is prepared by using the melting process described in any one of claims 1 - 8.

10. Use of the quartz crucible according to claim 9 in the refining of crystalline silicon.

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