Arc electrode device for producing quartz crucible, arc furnace, and method for producing quartz crucible

Abstract

The application relates to an arc electrode device for producing a quartz crucible, which comprises an electrode beam composed of three or more graphite electrodes, and the graphite electrodes are connected in sequence by straight graphite electrode segments, graphite curved segments and graphite connecting segments, so that each graphite electrode is in L shape. In the application, the graphite electrodes are changed from straight electrodes into special electrode shapes with outward bending by connecting the graphite curved segments and the graphite connecting segments at the ends of the straight graphite electrodes, so that the high-temperature arc area contour generated after the electrodes are ignited is changed from an elongated shape mainly radiating to the bottom wall of the crucible into a flat shape close to the straight wall of the crucible. Compared with the prior art, the heat radiated to the bottom wall of the crucible by the high-temperature arc can be appropriately reduced, the heat radiated to the straight wall of the crucible is increased, the problems of the r angle being too thick and the bubble belt are relieved, the compensation difference caused by graphite consumption is solved, and the quality stability of the crucible is improved. The application is especially suitable for producing large-size quartz crucibles.

Description

Technical Field

[0001] This invention relates to the field of quartz crucible production technology, specifically to an electric arc electrode device, an electric arc furnace, and a method for producing quartz crucibles. Background Technology

[0002] Silicon single crystals are primarily produced using the Czochralski (CZ) method. In this method, polycrystalline silicon is placed in a quartz crucible and heated to a molten silicon melt. A pull rod lowers a seed crystal into contact with the molten silicon, and the seed crystal is then slowly pulled upwards to form a silicon single crystal rod. The quartz crucible typically has a double-layer structure: an inner wall that is transparent and bubble-free, and an outer wall that is opaque with a higher bubble content. Because the inner wall is in contact with the molten silicon, if bubbles are present, they will rupture due to erosion by the polycrystalline silicon melt at high temperatures. If the ruptured fragments dissolve in the molten silicon, it will affect the yield and quality of the silicon single crystal. As the only material in contact with the silicon solution, the bubble content of the quartz crucible's inner wall, the purity of the quartz crucible, and its high-temperature deformation resistance are all important factors. Figure 1 The diagram shows a quartz crucible, which includes an inner transparent layer 1 and an outer non-transparent layer 2. The transparent layer 1 is in direct contact with the molten silicon. The transparent layer 1 includes a straight wall portion H, an arc-shaped transition surface L (called the r-angle), and a bottom surface W.

[0003] Quartz crucibles are generally made using the vacuum arc method, such as... Figure 2 As shown, the process includes: pouring high-purity quartz sand raw material into a graphite mold or metal mold; uniformly molding the quartz sand raw material onto the inner surface of the mold using a molding device; then melting the quartz sand at a high temperature above 3000℃ using a high-temperature electric arc furnace (generally a three-phase electric arc furnace with 3 graphite electrodes, 6 graphite electrodes, or, as in the applicant's prior patent CN114671599B, ​​2N+1 graphite electrodes, etc.); and finally, rapidly cooling to form a quartz (glass) crucible. In the process of making quartz crucibles using the vacuum electric arc method, the arc temperature and the heat that the crucible can come into contact with have a significant impact on the quality of the crucible, such as the content of bubbles on the inner wall, purity, resistance to high-temperature deformation, and degree of vitrification. Currently, the graphite electrodes in electric arc furnaces are all straight. To improve the purity of the inner wall of the crucible and reduce the number of bubbles, it is necessary to volatilize as many impurities and gas-liquid inclusions in the quartz sand as possible. Therefore, during the melting process, the arc electrode needs to be continuously moved. Typically, starting from the arc ignition point, it melts the crucible opening and upper wall for 1-3 minutes at a position 100-200 mm above the crucible (measured from the bottom of the electrode). Then, it gradually moves downwards to melt the straight wall section H, pausing for 2-5 minutes at each new position. Finally, it moves inside the crucible to melt the r-angle and bottom surface W. Existing electric arc furnaces for crucible melting have the following problems:

[0004] (1) With the use of electric arc furnaces, graphite electrodes will be consumed and shortened, thus requiring compensatory reduction in electrode length. Furthermore, after the graphite electrodes shorten, the arc coverage area will change when the electrodes are opened at the same angle. Therefore, it is necessary to compensate by changing the electrode opening angle or the illumination current while also considering the stability of the arc. In actual operation, it is difficult to accurately compensate for the shortening of graphite electrodes, leading to vacuum quality differences (called compensation differences) between crucibles produced from the same type of quartz sand raw material. These differences are difficult to eliminate, resulting in unstable quality for each batch of crucibles.

[0005] (2) Currently, all electrodes are straight electrodes with their ends pointing downwards. The principle of discharge at the electrode ends is that the heat from the electric arc during the arc melting process is mainly concentrated downwards. The high-temperature zone of the electric arc is mainly radiated towards the bottom wall of the crucible, which is elongated in shape. This makes the bottom wall of the crucible more concentrated in heat, and since the bottom wall is far from the open end of the crucible, the heat is well contained. This results in the bottom wall temperature being too high and the viscosity of the quartz melt decreasing. Under the action of centrifugal force (the mold frame drives the crucible mold to rotate during production), the quartz melt accumulates at the r-angle, causing the r-angle to be too thick and the formation of a bubble band (the bubbles cannot be discharged in time). At the same time, the straight wall is not heated enough, resulting in poor vacuum quality. During the CZ pull single crystal rod process, the rupture of bubbles on the surface of the crucible allows small quartz particles to enter the crystal pulling interface, leading to dislocations and breakage of the silicon rod.

[0006] Furthermore, in existing crucible manufacturing processes, the production quality of quartz crucibles is typically improved only by adjusting the current. However, in actual production, it has been found that adjusting the current alone has a very limited effect on improving the quality of quartz crucibles. Moreover, once the production equipment is built, the current capacity of its components is limited, making it difficult to produce larger crucibles with higher current to ensure melting quality. Modifying the hardware and rebuilding the equipment is also extremely costly. With industry development, crucible sizes are increasing, from the current 37 inches to 40-42 inches. Although using six electrodes can increase the arc range, in practice, it has been found that six electrodes still cannot improve the vacuum quality of the r-angle and the straight wall section H. A crucial indicator of vacuum quality is the bubble content on the inner wall (the lower the bubble content, the better the vacuum quality of the straight wall). The bubble content in the inner layer of the crucible is a core quality characteristic and a significant challenge and technical bottleneck in the industry. Because this technological bottleneck remains unresolved, quartz crucibles currently produced frequently experience bubble cracking at the r-angle and the H-section of the straight wall during CZ crystal pulling (typically, the vacuum quality at the bottom of the crucible > r > straight wall), severely impacting normal crystal pulling and silicon wafer performance. Therefore, existing electric arc furnaces cannot meet the requirements for high vacuum quality and long lifespan for large-size (≥37 inches) crucibles. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present application provides an electric arc electrode device for producing quartz crucibles, which comprises an electrode beam composed of three or more graphite electrodes, and the shape and structure of the existing graphite electrodes are improved to expand the arc range of the electric arc, so that the r-angle and straight wall of the crucible can be completely melted and homogenized during the production of the quartz crucible, the surface layer vacuum quality of the r-angle and straight wall of the inner layer of the crucible is improved, and the bubble content is reduced.

[0009] The present application is particularly suitable for producing large-size (≥37 inches) crucibles, improving the yield of crystal pulling and the whole bar rate, and prolonging the service life of the crucible.

[0010] (II) Technical solutions

[0011] In order to achieve the above-mentioned purpose, the main technical solutions adopted by the present application include:

[0012] In a first aspect, the present application provides an electric arc electrode device for producing quartz crucibles, which comprises an electrode beam composed of three or more graphite electrodes, and the graphite electrodes are sequentially connected by a straight graphite electrode segment, a graphite bending segment and a graphite connecting segment, so that each graphite electrode assumes an L shape; before starting the arc, the ends of the straight graphite electrode segments of each graphite electrode are brought together and kept at a distance from each other, and after starting the arc, each graphite electrode is moved away from each other so that the electrode beam assumes an open shape.

[0013] According to a preferred embodiment of the present application, the graphite bending segment comprises a vertical connecting segment and a horizontal connecting segment, the vertical connecting segment and the horizontal connecting segment are connected with a rounded corner, the vertical connecting segment is detachably connected with the end of the straight graphite electrode segment; the horizontal connecting segment is detachably connected with the graphite connecting segment and forms a horizontal outward expansion segment; the included angle between the horizontal outward expansion segment and the straight graphite electrode segment is 80-160 degrees; or:

[0014] The graphite bending segment is a graphite coupling with an angle, the angle is 80-160 degrees; the two ends of the graphite coupling have hollow portions, the inner threads are arranged in the hollow portions, the inner thread at the upper end of the graphite coupling is screwed with the bolt column formed at the end of the straight graphite electrode segment, and the inner thread at the lower end of the graphite coupling is screwed with the bolt column formed at the end of the graphite connecting segment.

[0015] According to a preferred embodiment of the present application, the straight graphite electrode segment and the vertical connecting segment are combined by threads, and the horizontal connecting segment and the graphite connecting segment are combined by threads.

[0016] According to a preferred embodiment of the present application, the length of the graphite connecting segment is 50-60 mm, which is a fixed length.

[0017] According to the preferred embodiment of the present application, the angle of the straight graphite electrode segment is adjustable; the angle between the straight graphite electrode segment and the vertical line is between 40 degrees and 0 degree.

[0018] According to the preferred embodiment of the present application, the graphite bent segment comprises a set of graphite bent segments with different lengths, which are used for disassembly and replacement according to the size of the quartz crucible to be prepared; the lengths of the lateral connecting segments of the graphite bent segments in the set are distributed between 5 mm and 150 mm.

[0019] According to the preferred embodiment of the present application, the top end of the straight graphite electrode segment is connected with the copper electrode; the upper end of the copper electrode is connected with the power supply, and the lower end of the copper electrode has a bolt column which is connected with the upper segment of the internal thread of the first graphite coupling; the upper end of the straight graphite electrode segment is formed with a bolt column which is connected with the lower segment of the internal thread of the second graphite coupling; graphite pair wires are screwed in the first graphite coupling and the second graphite coupling; the graphite pair wires are provided with external threads which are screwed in the lower segment of the internal thread of the first graphite coupling and the upper segment of the internal thread of the second graphite coupling, so as to achieve mechanical connection and electrical connection between the copper electrode and the upper end of the straight graphite electrode segment; an inclined annular gasket is sleeved outside the graphite pair wires, and the inclined annular gasket is located between the first graphite coupling and the second graphite coupling, and the inner diameter of the inclined annular gasket is larger than the outer diameter of the graphite pair wires.

[0020] By using the inclined annular gasket, the second graphite coupling can be rotated relative to the graphite pair wires while maintaining the tight connection between the second graphite coupling and the graphite pair wires, and then the straight graphite electrode segment is rotated by rotating the second graphite coupling, so as to adjust the orientation of the graphite bent segment and make the graphite connecting segment face the outside of the crucible, and the graphite electrodes of the electrode bundle are uniformly distributed relative to the circumference of the crucible mold.

[0021] In the second aspect, the present application provides an electric arc furnace for producing a quartz crucible, which comprises the electric arc electrode device.

[0022] Preferably, the electric arc furnace further comprises a graphite or metal mold and a mold support frame; in addition, the electric arc furnace further comprises a rotating driving mechanism and a vacuum pumping system; the mold support frame drives the graphite or metal mold to rotate;

[0023] The graphite connecting segments connected with the graphite electrodes of the electrode bundle are uniformly distributed relative to the circumference of the crucible mold.

[0024] In the third aspect, the present application further provides a method for producing a large-size quartz crucible, which adopts the electric arc furnace to melt the crucible; preferably, the large-size quartz crucible refers to a quartz crucible with a size of ≥37 inches.

[0025] Preferably, the angle of the straight graphite electrode segment is adjustable; the angle between the straight graphite electrode segment and the vertical line is between 40 degrees and 0 degrees, and the angle is adjusted according to the size of the quartz crucible to be prepared and the condition of ensuring arc stability.

[0026] (Three) the beneficial effects of the present application

[0027] (1) In the present application, the graphite electrode is changed from a straight electrode to a special-shaped electrode with outward bending by connecting a graphite bending segment and a graphite connecting segment at the end of the graphite straight electrode, so that the high-temperature arc area profile generated after the electrode is arcing is changed from an elongated shape mainly radiating to the bottom wall of the crucible to a flat shape close to the straight wall of the crucible. Compared with the prior art, the heat radiated to the bottom wall of the crucible can be appropriately reduced, the heat radiated to the straight wall of the crucible can be increased, the accumulation of the bottom wall to the r angle due to excessive temperature and small viscosity of the quartz melt under the action of centrifugal force can be reduced, the r angle can be prevented from being too thick, and the formation of a bubble zone can be prevented. At the same time, the vacuum quality of the straight wall of the crucible is improved, the bubble content of the surface layer of the straight wall part is reduced, the crystal pulling yield of the CZ method is improved, the breakage rate is reduced, and the crystal bar quality is improved.

[0028] (2) During the process of generating high-temperature arc by discharging the graphite electrode, part of the graphite is gradually oxidized to cause the loss of the graphite electrode. Since the arc is mainly based on the end discharge principle, the loss mainly occurs at the end of the electrode. In the present application, the graphite connecting segment is detachably connected to the graphite bending segment, and the graphite bending segment is detachably connected to the straight graphite electrode segment. Therefore, after one or two quartz crucibles are produced each time, the old graphite connecting segment is detached, a new graphite connecting segment is replaced, and the electrode is consistent with the initial arcing, thereby solving the problem of compensation difference and making the production quality of the crucible more stable.

[0029] (3) In the present application, the bending connecting part of the graphite straight electrode is provided as two detachable segments, i.e., the graphite bending segment and the graphite connecting segment. After the electrode is lost, the graphite connecting segment is directly replaced, and the whole bending connecting part does not need to be scrapped, so the electrode cost can be saved.

[0030] (4) In the preferred embodiment, the top end of the straight graphite electrode segment is connected with a copper electrode, and the copper electrode is connected with a power supply. The copper electrode and the straight graphite electrode segment are connected through two graphite collars and graphite wires. A beveled ring gasket is installed at the position where the two graphite collars meet, so as to adjust the orientation of the graphite bending segment connected to the end of the straight graphite electrode segment, make the horizontal connecting segment of the graphite bending segment face the outside of the crucible, and make the graphite bending segments of multiple graphite electrodes uniformly distributed relative to the circumference of the crucible mold, so as to ensure the uniformity and stability of the arc. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Fig. 1 is a schematic view of the structure of a quartz crucible.

[0032] Figure 2 Fig. 2 is a schematic view of the process of melting a quartz crucible using straight graphite electrodes of the prior art.

[0033] Figure 3 Fig. 3 is a schematic view of a quartz crucible with thick r-angles and bubble bands prepared by the prior art.

[0034] Figure 4 Fig. 4 is a schematic view of the melting of a quartz crucible using the arc electrode device of the present application.

[0035] Figure 5 Fig. 5 is a schematic view of the graphite bent section in one embodiment.

[0036] Figure 6 Fig. 6 is a schematic view of the opening angle of the straight graphite electrode section and the included angle between the lateral outwardly expanding section and the straight graphite electrode section in the present application.

[0037] Figure 7 Fig. 7 is a schematic view of the graphite bent section in another embodiment of the present application.

[0038] Figure 8 Fig. 8 is a schematic view of the installation of an inclined annular gasket at the position where the two graphite collars meet in the preferred embodiment of the present application.

[0039] Figure 9 Fig. 9 is a schematic view of the graphite connecting section connecting the ends of the three graphite electrodes of the present application dividing the circumference of the crucible mold into three 120-degree sectors. DETAILED DESCRIPTION

[0040] In order to better explain the present application and facilitate understanding, the present application is described in detail below by specific embodiments with reference to the accompanying drawings.

[0041] As Figure 2The diagram illustrates a conventional method for producing quartz crucibles using high-temperature electric arc melting. In this method, three straight graphite electrodes 3 are inserted into the crucible mold, where a high-temperature electric arc generated by end discharge melts the quartz raw material S. The melting temperature is typically above 3000℃. During melting, the mold support 4 is driven, causing the graphite or metal mold to rotate rapidly. In the first half of the melting process, a vacuum system is used to create a vacuum inside the crucible to ensure vacuum quality and form a highly transparent inner wall. Afterward, the vacuum system is turned off, and melting continues to obtain a non-transparent outer wall. As the straight graphite electrodes 3 are worn down during the release of the high-temperature electric arc, their positions need to be adjusted, moving downwards. Furthermore, because the straight graphite electrodes 3 become shorter, even when opened at the same angle, the distance between the electrode ends changes. Therefore, the current needs to be adjusted appropriately to compensate for the difference in wear to some extent. However, this adjustment is somewhat random and inaccurate, leading to unstable crucible quality. Furthermore, after the straight graphite electrode 3 initiates its arc, the high-temperature arc region is elongated, primarily radiating to the bottom wall of the crucible. This results in excessively high temperatures at the bottom wall, where the quartz melt has low viscosity and easily flows to the r-angle position under centrifugal force. This leads to excessive thickness at that position and the formation of a ring of bubbles (e.g., Figure 3 (As shown). At the same time, since the straight graphite electrode 3 is located in the center of the crucible, the heat obtained by the straight wall of the crucible is insufficient. The straight wall is also closer to the open end, resulting in poor heat retention. This leads to poor melting effect in the straight wall, and a higher level of bubbles and impurities on the surface of the straight wall (insufficient heat leads to incomplete melting, and impurities are difficult to vaporize or disperse in the form of ash).

[0042] like Figure 4 As shown, this invention, based on existing technology, obtains an outwardly curved irregular electrode shape by changing the shape of a straight graphite electrode. The graphite electrode 10 is formed by sequentially connecting a straight graphite electrode segment 101, a graphite bending segment 102, and a graphite connecting segment 103, making each graphite electrode 10 generally L-shaped. Before arc initiation, the ends of the straight graphite electrode segments 101 of each graphite electrode 10 are close together and maintain a small distance to facilitate rapid arc initiation between the graphite electrodes 10. After arc initiation, the graphite electrodes 10 are separated by a certain distance, causing the electrode bundle to open, thereby meeting the requirements for melting large-size quartz crucibles. Figure 4 As shown, the high-temperature arc region generated by the graphite electrode 10 has a flat outline, and the boundary of the high-temperature arc region is closer to the straight wall of the crucible, which reduces the heat radiated to the bottom wall of the crucible. Preferably, the lengths of the straight graphite electrode segment 101 and the graphite connecting segment 103 are fixed.

[0043] like Figure 5As shown, the graphite bending section 102 comprises a vertical connecting section 1021 and a horizontal connecting section 1022. The vertical connecting section 1021 and the horizontal connecting section 1022 are connected by a rounded corner, the vertical connecting section 1021 is detachably connected to the end of the straight graphite electrode section 101, preferably by screwing. The horizontal connecting section 1022 is detachably connected to the graphite connecting section 103 and forms a horizontal outwardly expanding section, the detachable connection is by screwing. As the two ends of the graphite bending section 102 form protruding bolts, and the end of the straight graphite electrode section 101 and the end of the graphite connecting section 103 form threaded caps, the straight graphite electrode section 101, the graphite bending section 102 and the graphite connecting section 103 are sequentially screwed together. The horizontal connecting section 1022 of the graphite bending section 102 is connected to the graphite connecting section 103 to form a horizontal outwardly expanding section.

[0044] As shown, Figure 6 The angle β between the horizontal outwardly expanding section and the straight graphite electrode section 101 is 80-160 degrees. The length L2 of the straight graphite electrode section 101 and the vertical connecting section 1021 of the graphite bending section 102 determines the size of the angle β, which even determines the position of the arc discharge. When the angle β is small, the end of the graphite connecting section 103 can be higher than the rounded outer end of the graphite bending section 102, resulting in the tip position of the electrode being the rounded outer end of the graphite bending section 102, and the arc discharge position being the rounded outer end of the graphite bending section 102; when the angle β is large, such as greater than 90 degrees, the end of the graphite connecting section 103 is always lower than the rounded outer end of the graphite bending section 102, resulting in the tip position of the electrode being the end of the graphite connecting section 103, and the arc discharge position being the end of the graphite connecting section 103. Preferably, the angle of the straight graphite electrode section 101 being folded or unfolded is adjustable, and the angle α of the straight graphite electrode section 101 relative to the vertical line changes between 40 degrees and 0 degrees. The discharge position is also related to the angle α. When the angle β is less than 90 degrees, if the angle α is large, the discharge position can also be at the end of the graphite connecting section 103; if the angle α is small, i.e. the straight graphite electrode section 101 is closer to the vertical, the discharge position can be shifted to the rounded outer end of the graphite bending section 102.

[0045] Preferably, the length of the graphite connecting section 103 is 50-60 mm. By detachably connecting the graphite connecting section 103 to the graphite bending section 102, when the graphite electrode 10 is worn out after being used for a period of time, the old graphite connecting section 103 can be removed and replaced with a new graphite connecting section 103 of the initial length, which can solve the problem of compensation difference and make the production quality of the crucible more stable. For example, a new graphite connecting section 103 can be replaced after the production of each quartz crucible. Since the wear of the graphite electrode 10 is relatively fixed after the production of one or two crucibles, the length of the graphite connecting section 103 is also fixed in the present application, thereby reducing the waste of graphite.

[0046] To improve the vacuum quality of the straight wall section of the crucible, the distance L1 between the end of the graphite joint section 103 and the inner wall of the crucible should be minimized as much as possible. This allows the straight wall section of the crucible to receive more heat and homogenize the material, achieving purification, impurity removal, and elimination of gas-liquid inclusions (bubbles) under the action of the vacuum system. To accommodate the preparation of crucibles of different sizes, this invention prepares a collection of graphite bend sections 102 of various specifications with different lengths for disassembly and replacement according to the size of the quartz crucible to be prepared. The length of the transverse connecting section 1022 of the graphite bend sections 102 in the collection can be distributed between 5-150 mm. By disassembling and assembling, graphite bend sections 102 of appropriate length can be replaced to shorten L1.

[0047] like Figure 7 As shown, the shape of the graphite bend section 102 can be as follows: Figures 4-5 In addition to the form shown, it can also be as follows: Figure 7 The structure shown is as follows: the graphite bend segment 102 is a graphite coupling with a β angle. Both ends of the graphite coupling have hollow portions with internal threads. The internal thread at the upper end of the graphite coupling is screwed into a bolt post formed at the end of the straight graphite electrode segment 101, and the internal thread at the lower end of the graphite coupling is screwed into a bolt post formed at the end of the graphite continuation segment 103. Similarly, the β angle is 80-160 degrees, and an appropriate angle can be selected as needed. In this embodiment, the graphite bend segment 102 does not have rounded corners but rather a sharp angle transition.

[0048] In some cases, after the graphite bend segment 102 is threaded onto the straight graphite electrode segment 101, the end of the graphite bend segment 102 may not face outwards from the crucible, or although it may face outwards from the crucible, the transverse connecting segments 1022 of the three electrodes may not be evenly distributed within the circumference of the crucible mold. To solve this problem, the present invention preferably includes a mechanism for adjusting the deflection direction of the graphite bend segment 102. For example... Figure 8As shown: the copper electrode 6 and the upper end of the straight graphite electrode segment 101 are fixedly connected and electrically connected through the first graphite coupling 71, the second graphite coupling 72 and the graphite pair wire 73. The upper end of the copper electrode 6 is connected with the power supply, and the lower end of the copper electrode 6 has a bolt column (in this application, the bolt column refers to a connecting segment with external threads), which is connected with the upper segment of the internal threads of the first graphite coupling 71, and the upper end of the straight graphite electrode segment 101 is also formed with a bolt column, which is connected with the lower segment of the internal threads of the second graphite coupling 72; the graphite pair wire 73 is also screwed inside the first graphite coupling 71 and the second graphite coupling 72. The graphite pair wire 73 is provided with external threads, which are screwed in the lower segment of the internal threads of the first graphite coupling 71 (the inner diameter of the lower segment is larger than that of the upper segment) and the upper segment of the internal threads of the second graphite coupling 72 (the inner diameter of the upper segment is larger than that of the lower segment), so that the copper electrode 6 and the upper end of the straight graphite electrode segment 101 of different materials can be mechanically connected and electrically connected.

[0049] As shown: the copper electrode 6 and the upper end of the straight graphite electrode segment 101 are fixedly connected and electrically connected through the first graphite coupling 71, the second graphite coupling 72 and the graphite pair wire 73. The upper end of the copper electrode 6 is connected with the power supply, and the lower end of the copper electrode 6 has a bolt column (in this application, the bolt column refers to a connecting segment with external threads), which is connected with the upper segment of the internal threads of the first graphite coupling 71, and the upper end of the straight graphite electrode segment 101 is also formed with a bolt column, which is connected with the lower segment of the internal threads of the second graphite coupling 72; the graphite pair wire 73 is also screwed inside the first graphite coupling 71 and the second graphite coupling 72. The graphite pair wire 73 is provided with external threads, which are screwed in the lower segment of the internal threads of the first graphite coupling 71 (the inner diameter of the lower segment is larger than that of the upper segment) and the upper segment of the internal threads of the second graphite coupling 72 (the inner diameter of the upper segment is larger than that of the lower segment), so that the copper electrode 6 and the upper end of the straight graphite electrode segment 101 of different materials can be mechanically connected and electrically connected. Figure 9 As shown: the copper electrode 6 and the upper end of the straight graphite electrode segment 101 are fixedly connected and electrically connected through the first graphite coupling 71, the second graphite coupling 72 and the graphite pair wire 73. The upper end of the copper electrode 6 is connected with the power supply, and the lower end of the copper electrode 6 has a bolt column (in this application, the bolt column refers to a connecting segment with external threads), which is connected with the upper segment of the internal threads of the first graphite coupling 71, and the upper end of the straight graphite electrode segment 101 is also formed with a bolt column, which is connected with the lower segment of the internal threads of the second graphite coupling 72; the graphite pair wire 73 is also screwed inside the first graphite coupling 71 and the second graphite coupling 72. The graphite pair wire 73 is provided with external threads, which are screwed in the lower segment of the internal threads of the first graphite coupling 71 (the inner diameter of the lower segment is larger than that of the upper segment) and the upper segment of the internal threads of the second graphite coupling 72 (the inner diameter of the upper segment is larger than that of the lower segment), so that the copper electrode 6 and the upper end of the straight graphite electrode segment 101 of different materials can be mechanically connected and electrically connected.

[0050] It should be noted that Figure 8 The structure is not limited to the embodiment of "the graphite bending segment 102 is a graphite coupling with a β angle", and is applicable to other embodiments. In addition, the number of graphite electrodes is not limited to three, and can be six graphite electrodes, and the end of each graphite electrode has a graphite bending segment 102 and a graphite connecting segment 103 connected in sequence, and the graphite connecting segment 103 evenly divides the circumference of the crucible mold into six 60-degree sectors.

[0051] The characteristics and effects of the application will be described below in combination with application examples of the application. In the following application examples, natural quartz sand with a purity of 99.9% is used to prepare a quartz crucible. In the following examples, the position refers to the position of the lowermost end of the graphite electrode relative to the opening of the crucible mold in the vertical height direction. The horizontal plane of the opening of the crucible mold is taken as the zero point, and the position above the zero point is marked as +, and the position below the zero point is marked as -.

[0052] Application Example 1

[0053] This embodiment provides a high-quality quartz crucible manufacturing method, which is used for manufacturing a quartz crucible with an outer diameter of 37 inches. The vacuum arc method is adopted, and the steps are as follows:

[0054] (1) The 10-500 microns of natural quartz sand with a purity of 99.9% is uniformly distributed in the crucible mold; and the molding device uniformly molds the quartz sand raw material on the inner surface of the mold.

[0055] (2) The molded mold is moved into the arc electrode device;

[0056] (3) The transverse connecting section 1022 (length of 10 mm) of the graphite bending section 102 of the three graphite electrodes 10, and the length of the graphite connecting section 103 is 50 mm, and the β angle is 110 degrees. After starting the arc, the three graphite electrodes 10 are opened, and the α angle changes from 40 degrees to 20 degrees.

[0057] (4) During the melting process, the current of the three graphite electrodes 10 is controlled to be 4000 A, and the vacuum degree is controlled to be -0.093 Mpa to -0.1 Mpa. The walking mode is as follows:

[0058] Step Electrode position Melting time 1 Arc starting point 20s 2 +120 mm 1 min 3 +100 mm 3 min 4 +70 mm 5 min 5 -50 mm 3 min

[0059] (5) After the melting is completed, the quartz crucible is cooled and taken out of the furnace, and the manufacturing of the quartz crucible blank is completed; the quartz crucible blank is sequentially cut, inspected, washed, dried, packaged, and stored.

[0060] Application Example 2

[0061] This embodiment provides a high-quality quartz crucible manufacturing method, which is used for manufacturing a quartz crucible with an outer diameter of 40 inches. The vacuum arc method is adopted, and the steps are as follows:

[0062] (1) The 10-500 microns of natural quartz sand with a purity of 99.9% is uniformly distributed in the crucible mold; and the molding device uniformly molds the quartz sand raw material on the inner surface of the mold.

[0063] (2) The molded mold is moved into the arc electrode device;

[0064] (3) The transverse connecting section 1022 (length of 40 mm) of the graphite bending section 102 of the three graphite electrodes 10, and the length of the graphite connecting section 103 is 50 mm, and the β angle is 105 degrees. After starting the arc, the three graphite electrodes 10 are opened, and the α angle changes from 40 degrees to 25 degrees.

[0065] (4) During the melting process, the current of the three graphite electrodes 10 is controlled to be 4500 A, and the vacuum degree is controlled to be -0.093 Mpa to -0.1 Mpa. The walking mode is as follows:

[0066] Step Electrode position Melting time 1 Arc starting point 20s 2 +120 mm 1 min 3 +100 mm 3 min 4 +70 mm 5 min 5 -50 mm 3 min

[0067] (5) After melting, the quartz crucible is cooled and removed from the furnace, completing the production of the quartz crucible blank; the quartz crucible blank is then cut, inspected, cleaned, dried, packaged and stored.

[0068] Comparative Example 1

[0069] This embodiment uses a traditional electric arc furnace with three straight graphite electrodes to melt a 37-inch quartz crucible. The steps are as follows:

[0070] (1) Evenly distribute 10-500 micrometers of natural quartz sand with a purity of 99.9% in the crucible mold; the molding device evenly molds the quartz sand raw material on the inner surface of the mold.

[0071] (2) The molded mold is moved into the arc electrode device;

[0072] (3) After the three straight graphite electrodes start to arc, they open up, and the α angle changes from 40 degrees to 20 degrees.

[0073] (4) During the melting process, the current of the three straight graphite electrodes is controlled at 4000A, and the vacuum degree is controlled between -0.093Mpa and -0.1Mpa. The positioning method is as follows:

[0074]

[0075]

[0076] (5) After melting, the quartz crucible is cooled and removed from the furnace, completing the production of the quartz crucible blank; the quartz crucible blank is then cut, inspected, cleaned, dried, packaged and stored in the warehouse.

[0077] The inner transparent layer of the aforementioned prepared quartz crucible was analyzed using atomic absorption spectrometry to determine the content of impurity elements on the innermost layer, as shown in the table below:

[0078] Impurity and bubble content (average value of 3 detection points, % refers to area percentage).

[0079] Group Straight wall portion impurities r angle impurities Straight wall portion bubbles r angle bubbles Example 1 16 ppm 23 ppm 0.05％ 0.04％ Example 2 17 ppm 25 ppm 0.08％ 0.06％ Comparative Example 1 25 ppm 34 ppm 2％ 1.5％

[0080] Comparison shows that, compared to Application Examples 1 and 2, Comparative Example 1 has a higher bubble content at the r-angle, forming a bubble band. Simultaneously, the impurity content and bubble content in the straight wall and at the r-angle are also higher. The quartz crucibles produced by Application Examples 1-2 of this invention have better vacuum quality in the straight wall section, and the impurity content and bubble surface area ratio (per 1 cm²) at the r-angle position are also higher. 2The area ratio of the inner bubbles is lower. Thus, it is illustrated that the arc electrode structure and the quartz crucible prepared by the arc furnace have better performance, and the vacuum quality of the straight wall part is improved, and the problems of the r angle thickening and the bubble belt are solved.

[0081] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An arc electrode device for producing a quartz crucible, characterized by comprising: The electrode beam comprises three or more graphite electrodes, which are connected by straight graphite electrode segments, graphite elbow segments and graphite connecting segments, so that each graphite electrode is in L shape; before arcing, the ends of the straight graphite electrode segments of each graphite electrode are close to each other and keep a distance, and after arcing, each graphite electrode is far away from each other so that the electrode beam is in open shape; The angle of the straight graphite electrode segments is adjustable; the angle between the straight graphite electrode segments and the vertical line changes between 40 degrees and 0 degrees; The graphite connecting segments are towards the outside of the crucible, and the graphite connecting segments connected by the ends of the graphite electrodes of the electrode beam are uniformly distributed relative to the circumference of the crucible mold.

2. An arc electrode apparatus for producing a quartz crucible according to claim 1, wherein The lengths of the straight graphite electrode segments and the graphite connecting segments are fixed; The graphite elbow segment comprises a vertical connecting segment and a horizontal connecting segment, which are connected by a round corner, and the end of the vertical connecting segment is detachably connected with the straight graphite electrode segment; the horizontal connecting segment is detachably connected with the graphite connecting segment and forms a horizontal outward expansion segment; the angle between the horizontal outward expansion segment and the straight graphite electrode segment is 80-160 degrees; or The graphite elbow segment is a graphite coupling with an angle, and the angle is 80-160 degrees; the two ends of the graphite coupling have hollow parts, and the inner threads inside the hollow parts are screwed with the bolt columns formed by the ends of the straight graphite electrode segments and the bolt columns formed by the ends of the graphite connecting segments.

3. An arc electrode apparatus for producing a quartz crucible according to claim 2, wherein The straight graphite electrode segments and the vertical connecting segments are combined by threads, and the horizontal connecting segments and the graphite connecting segments are combined by threads.

4. An arc electrode apparatus for producing a quartz crucible according to claim 2, wherein The length of the graphite connecting segment is 50-60 mm, which is a fixed length.

5. An arc electrode apparatus for producing a quartz crucible according to claim 2, wherein The graphite elbow segment comprises a collection of graphite elbow segments with different lengths, which are used for disassembly, replacement and assembly according to the size of the quartz crucible to be prepared; the lengths of the horizontal connecting segments of the graphite elbow segments in the collection are distributed between 5-150 mm.

6. An arc electrode apparatus for producing a quartz crucible according to claim 2, wherein The top end of the straight graphite electrode segment is connected with a copper electrode; the upper end of the copper electrode is connected with a power supply, and the lower end of the copper electrode has a bolt column, which is connected with the upper segment of the inner thread of the first graphite coupling; the upper end of the straight graphite electrode segment has a bolt column, which is connected with the lower segment of the inner thread of the second graphite coupling; graphite pairs are also screwed inside the first graphite coupling and the second graphite coupling; the graphite pairs have outer threads, which are screwed with the lower segment of the inner thread of the first graphite coupling and the upper segment of the inner thread of the second graphite coupling, so that mechanical connection and electrical connection are achieved between the copper electrode and the upper end of the straight graphite electrode segment; an inclined annular gasket is sleeved outside the graphite pairs, and the inclined annular gasket is located between the first graphite coupling and the second graphite coupling, and the inner diameter of the inclined annular gasket is larger than the outer diameter of the graphite pairs.

7. An electric arc furnace for producing quartz crucibles, characterized in that The electric arc furnace comprises the electric arc electrode device.

8. An electric arc furnace for producing quartz crucibles according to claim 7, characterized in that The electric arc furnace further comprises a graphite or metal mold and a mold support frame; the electric arc furnace further comprises a rotating driving mechanism and a vacuum pumping system; the mold support frame drives the graphite or metal mold to rotate. The electric arc furnace comprises the electric arc electrode device.

9. A method of producing a large size quartz crucible, characterized by, The quartz crucible is melted by using the electric arc furnace for producing quartz crucible according to claim 7 or 8; the angle of the converging or diverging of the straight graphite electrode segment is adjustable; the angle between the straight graphite electrode segment and the vertical line is changed between 40 degrees and 0 degrees, and the angle is adjusted according to the size of the quartz crucible to be prepared and the condition of ensuring the stability of the electric arc.

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