Graphite piece for two-piece set

Abstract

The graphite piece comprises an upper cone, a middle body and a lower cone which are sequentially arranged from top to bottom, the middle body is a cylinder, an upper through hole is formed in the center of the upper cone and used for installing a silicon core, a lower through hole is formed in the center of the lower cone and used for being communicated with a graphite clamping seat, and the upper through hole is communicated with the lower through hole. The taper of the upper cone is larger than that of the lower cone, and the height of the upper cone is smaller than that of the lower cone. According to the scheme, the graphite piece is designed into a vertically asymmetric structure, the height of the upper cone is smaller than that of the lower cone, the taper of the upper cone is increased, the silicon core holding force is large, the loading force is enhanced, and the silicon core toppling resistance is enhanced; according to the improvement of the scheme, on the premise that the height and other dimensions of the original reduction furnace are not adjusted, the effective length of the silicon core is increased by reducing the height of the graphite piece, and then the effective length of the generated silicon rod is increased.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production process control, in particular to a graphite piece used in a two-piece set. Background Art

[0002] Polysilicon is the main raw material for silicon wafers in solar panels, especially electronic grade polysilicon, which has a purity requirement of 99.9999999%-99.9999999999% (collectively referred to as nine nines to twelve nines). The modified Siemens reduction process is to convert trisilicon into pure silicon, which is the most critical step in determining the purity of polysilicon. During the reduction process, the silicon core is installed in the reduction furnace using a graphite assembly. Graphite assemblies are generally divided into two types, three-piece sets and two-piece sets. This solution is part of the two-piece set.

[0003] The original design used a graphite head in the device for connecting and fixing the silicon core in the polysilicon reduction furnace with patent number 202020535417.9. The graphite head is a symmetrical structure with the upper cone used to install the silicon core. This structure has the following problems: the overall height of the graphite head is high, the height of the upper cone is high, and it occupies a large space in the furnace. The processing consumes a lot of silicon material, and the upper cone has low strength to hold the silicon core, resulting in a high risk of the silicon core tipping over. Figure 7 , 8 . Summary of the invention

[0004] In view of the above defects, the utility model proposes a graphite part for a two-piece set, comprising an upper cone, an intermediate body, and a lower cone arranged from top to bottom in sequence, the intermediate body is a cylinder, an upper through hole is opened at the center of the upper cone for installing a silicon core, a lower through hole is opened at the center of the lower cone for connecting with a graphite seat, the upper through hole and the lower through hole are connected, the taper of the upper cone is greater than the taper of the lower cone, and the height of the upper cone is less than the height of the lower cone.

[0005] This scheme designs the graphite parts into an asymmetric structure up and down, the height of the upper cone is less than the lower cone, the taper of the upper cone is increased, the holding force on the silicon core is large, the load force is enhanced, and the ability to resist the tipping of the silicon core is enhanced. The height of the upper cone is reduced, saving space in the reduction furnace and processing raw materials. Compared with the original design, the height of the upper cone is consistent with the height of the lower cone, which is 42mm. The height of the upper cone after improvement is 20mm, which is reduced by 22mm. For the 40-pair rod reduction furnace, 22mm of space is saved in the height space. After adopting this scheme, the length of the silicon core can be lengthened by 22mm, and the highest installation point position in the original furnace body can still be maintained unchanged. After reduction, the length of each silicon rod can be increased by 22mm. Compared with the original 3m silicon core and 3m silicon rod, the output length of each silicon rod increases by 0.022 meters, and the silicon rod output rate increases by 0.022 / 2=1.1%. 40 pairs of rods will increase the output by 0.022 meters*40*2=1.76 meters. Therefore, the improvement of this scheme is to increase the effective length of the silicon core by lowering the height of the graphite parts without adjusting the original reduction furnace height and other dimensions, thereby increasing the effective length of the generated silicon rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 , 2 Schematic diagram of the structure of graphite parts.

[0007] Figure 3 This is a schematic diagram of the installation of graphite parts, graphite cassettes, and silicon cores.

[0008] Figure 4 Schematic diagram of the three states of silicon core installation: normal installation, tilted position 1, and tilted position 2.

[0009] Figure 5 for Figure 4 The figure highlights the comparison of different tilt angles when the silicon core bottom is position 1 and the top of the silicon core bottom is position 2 with the same tilt amplitude.

[0010] Figure 6 Schematic diagram of the effect of silicon core tilt on amplitude.

[0011] Figure 7 , 8 It is a schematic diagram of a conical upper through hole in a graphite head in the prior art.

[0012] In the figure: graphite part 100, graphite cassette 200, silicon core 300, upper cone 10, upper through hole 11, large diameter hole 111, small diameter hole 112, step 113, intermediate body 20, side through hole 21, lower cone 30, lower through hole 31. DETAILED DESCRIPTION

[0013] See also Figure 1-6, a graphite part 100 for a two-piece set, including an upper cone 10, an intermediate body 20, and a lower cone 30 arranged in sequence from top to bottom. The intermediate body 20 is a cylinder. An upper through hole 11 is opened at the central position of the upper cone 10 for installing a silicon core 300. A lower through hole 31 is opened at the central position of the lower cone 30 for communicating with a graphite socket 200. The upper through hole 11 and the lower through hole 31 are communicated. The taper of the upper cone 10 is greater than the taper of the lower cone 30, and the height of the upper cone 10 is less than the height of the lower cone 30 (H upper < H lower). The three-stage cone in this solution is obtained by processing and forming with an integrated machine.

[0014] Furthermore, the depth of the upper through hole 11 is greater than 1 / 2 of the total height of the graphite part. (The total height is H upper + H middle + H lower. With this setting in this solution, the depth of the silicon core inserted into the graphite part is relatively deep, exceeding half of the position of the graphite part. The realization of this solution can only be achieved on the basis of the relatively small height of the upper cone 10. The role of the graphite part is first to stabilize the silicon core. After the silicon core is installed in the graphite part, during the reduction process, due to the influence of the furnace environment and the vibration of the graphite socket, there is a risk of tipping. To avoid tipping, the tipping force of the silicon core mainly relies on the upper cone 10 to offset. The part of the silicon core inserted into the graphite part relies on the wrapping force of the side wall of the upper cone 10 on the side wall of the silicon core to resist the tipping force. Therefore, the upper cone 10 bears a large force. So in the original design, the height of the upper cone 10 is relatively high, at least the same as the height of the lower cone 30, in order to better wrap the silicon core and avoid tipping. Although the height of the upper cone 10 is shortened in this solution, the wrapping force on the silicon core is instead enhanced. With such a design, when a silicon core with a height of about 3 meters is installed in the graphite part, the bottom of the silicon core installed in the graphite part is lower than the geometric center of the graphite part. When the silicon core tips, when the tipping force acts on the graphite part, the force resisting the tilt of the silicon core is not only provided by the upper cone 10. The bottom of the silicon core below the geometric center transmits this tipping force downward to the middle cone and the lower cone 30 until the graphite socket below. The force resisting this tipping is provided by the entire graphite part, which is much greater than the force provided only by the upper cone 10 in the original graphite part; in addition, the upper cone 10 with a larger taper makes the side wall of the upper vertebral body wrapped with the silicon core thicker, enhancing the strength and providing a greater force to resist the tipping of the silicon core and the silicon rod; such as Figure 4 , 5It is shown that, assuming that position 1 is a schematic diagram of the original design in which the silicon core is installed shallowly into the upper through hole 11, and position 2 is a schematic diagram of the present solution in which the silicon core is installed deeply into the upper through hole 11, which is greater than 1 / 2 of the total height of the graphite part. The force analysis of the tilting force at the two installation depths is compared: assuming that the silicon core at a height of 3 meters falls over, and when the tilt amplitude L is the same, angle 2 at position 2 is significantly smaller than angle 1 at position 1, and the risk of falling over is smaller. Moreover, the smaller angle 2 makes the tilting force of the side wall of the upper cone 10 distributed from the top of the upper cone 10 to the height range of position 2, that is, distributed within the height range of H2. The distribution range is larger, and naturally the force shared by the upper cone is smaller, and the risk of the upper cone 10 breaking is smaller. However, angle 1 is greater than angle 2, and the risk of falling over is greater. Moreover, the larger angle 1 makes the tilting force of the side wall of the upper cone 10 distributed from the top of the upper cone 10 to the height range of position 1, that is, distributed within the height range of H1. The distribution range is smaller, and the force shared by the upper cone is greater, and the risk of the upper cone 10 breaking is undoubtedly increased.

[0015] This solution is suitable for two-piece graphite components, such as Figure 3 As shown, it is completely different from the three-piece graphite assembly. Therefore, the force analysis is only compared with the two-piece model (such as the solution in the background technology).

[0016] Furthermore, the taper of the upper cone 10 is 39-42°. In the figure, α shows half the taper angle, and the taper of the upper cone 10 is twice α.

[0017] Furthermore, the taper of the upper cone 10 is 40-41°.

[0018] Furthermore, the taper of the upper cone 10 is 40.45°. Compared with the upper taper β of 18° in the original design, the taper of the upper cone 10 is twice β, that is, 36°, which is a substantial improvement.

[0019] Furthermore, the upper through hole 11 is a step hole, and the step hole includes a large diameter hole 111 and a small diameter hole 112. The diameter of the large diameter hole is larger than the diameter of the small diameter hole. The large diameter hole 111 and the small diameter hole 112 are both straight holes of equal diameter, and the step 113 of the step hole is a right-angle transition. The silicon core applicable to this scheme also has the characteristics of a small diameter at the end and a large diameter at the top, so that the bottom of the silicon core matches the upper through hole 11. The design of the step hole, firstly, when the silicon core is installed, through the contact at the step 113, personnel can grasp from the outside whether the silicon core is installed in place, avoiding the problem that the insertion depth cannot be intuitively controlled when the conical hole is installed; secondly, the design of the vertical through hole, due to the existence of gravity, the force of the silicon core is vertically downward (only the force in the F2 direction), and the side wall of the silicon core is only in close contact with the side wall of the through hole. Only when it is tilted will it give the side wall of the through hole an inclined force. When the scheme is operating normally, the silicon core will not exert a force on the cone, and compared with the conical upper through hole 11, especially Figure 7The three surfaces M1, M2, and M3 of the middle upper through hole 11, even if there is no tendency to tip over during normal operation, the silicon core will exert a large outward centrifugal force (in the F3 direction) on the side wall of the through hole due to gravity and the existence of the conical surface. The existence of this force not only makes the upper cone 10 subject to a greater risk of cracking, but also causes the silicon core to have the potential energy to shake in the direction of the radius of the conical surface (in the F3 direction). Especially during the reduction process, the air flow disturbance in the furnace can easily cause the silicon core to shake. Thirdly, the existence of this centrifugal force is transmitted to the graphite holder, causing the graphite holder to bear the force from the center to the outside. The radial and front-to-back and left-to-right shaking forces increase the risk of shaking of the graphite cassette holder. Thus, under the same furnace environment, due to the presence of the conical upper through hole 11, the risk of shaking of the silicon core increases, and the shaking silicon core causes shaking of the graphite cassette holder. For a silicon core that is more than 3 meters long, the graphite cassette holder shakes within a range of 0.1°, which is transmitted to the top of the silicon core and increases the shaking range exponentially. The shaking of the silicon core will be transmitted to the graphite cassette holder again, which will cause the graphite cassette holder to shake at a larger angle. The accumulated shaking deviation will only continue to accumulate and increase, eventually causing the risk of furnace failure.

[0020] like Figure 6 As shown, ∠A is the angle change of the silicon core caused by the shaking of the graphite cassette. For the convenience of calculation, it is assumed that ∠A is 30°. When tilted, AC is the right side of the silicon core. Only the right side is used to represent the degree of tilt of the silicon core. ∠C is a right angle, and the length of BC is the amplitude range distance L of the shaking of the top of the silicon core. It is calculated that BC=1.5m; in practice, a graphite cassette shaking angle of 0.1° will cause a larger amplitude of the silicon core. The amplitude range distance of the top of the silicon core BC=sin0.1°*3m=0.0998*3m=0.2994m, which is about 0.3m. During the reduction growth process, the height of the silicon core remains unchanged, the diameter of the silicon rod grows from about 17mm to about 150mm, and the weight reaches 160kg, while the size of the graphite parts and graphite cassettes at the bottom of the silicon rod remain unchanged. The silicon rods in the furnace are very thick and very high, and the graphite cassettes serve as the base, with a small volume and area. The silicon rods are top-heavy. The shaking of this distance is enough to cause the silicon rods to fall over, and then cause the entire furnace of silicon rods to fall over, forming an inverted furnace.

[0021] Furthermore, the diameter of the large-diameter hole is 1-2.5 mm larger than the diameter of the small-diameter hole.

[0022] Furthermore, the diameter φouter of the large-diameter hole is 17 mm±0.05, and the diameter φinner of the small-diameter hole is 15.4 mm±0.05.

[0023] Furthermore, a side through hole 21 is provided on the side wall of the middle cone, and the side through hole 21 is connected to the large diameter hole. Although the lower through hole 31 is connected to the small diameter hole and the large diameter hole, when the silicon core inside the large diameter hole is heated, the heat is discharged along the large diameter hole, the small diameter hole, and the lower through hole. Due to the presence of the step hole, the step surface of the silicon core and the step surface of the step hole form a strong mechanical sealing surface, resulting in the heat generated by the large-diameter silicon core being difficult to be discharged from the lower through hole 31. Therefore, the position of the side through hole 21 is set in this scheme to be connected to the large diameter hole, which is used to discharge the high heat caused by the heating of the silicon core in the large diameter hole and avoid local high heat breakdown. This is different from the original design. In the original design, the side through hole 21 is connected to the middle cone, while the upper cone 10 and the lower cone 30 have no exhaust channel. Therefore, in the original design, the inclined conical step surface where the silicon core at the position of the upper cone 10 contacts the middle cone still has a good mechanical seal, and the high heat of the upper cone 10 cannot be smoothly discharged along the middle cone and the side through hole 21.

[0024] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of this patent.

Claims

1. A graphite part for a two-piece set, characterized in that: It includes an upper cone, an intermediate body, and a lower cone which are arranged in sequence from top to bottom. The intermediate body is a cylinder. An upper through hole is provided at the center of the upper cone for installing a silicon core. A lower through hole is provided at the center of the lower cone for connecting with a graphite cassette. The upper through hole is connected to the lower through hole. The taper of the upper cone is greater than that of the lower cone, and the height of the upper cone is less than that of the lower cone.

2. The graphite component for a two-piece set as claimed in claim 1, characterized in that: The depth of the upper through hole is greater than 1 / 2 of the total height of the graphite piece.

3. The graphite component for a two-piece set as claimed in claim 2, characterized in that: The taper of the upper cone is 39-42°.

4. The graphite component for a two-piece set as claimed in claim 3, characterized in that: The taper of the upper cone is 40-41°.

5. The graphite component for a two-piece set as claimed in claim 4, characterized in that: The taper of the upper cone is 40.45°.

6. The graphite component for a two-piece set as claimed in claim 2, characterized in that: The upper through hole is a stepped hole, which includes a large diameter hole and a small diameter hole. The diameter of the large diameter hole is larger than that of the small diameter hole. Both the large diameter hole and the small diameter hole are straight holes of equal diameter, and the step of the stepped hole is a right-angle transition.

7. The graphite component for a two-piece set as claimed in claim 6, characterized in that: The diameter of the large diameter hole is 1-2.5 mm larger than the diameter of the small diameter hole.

8. The graphite component for a two-piece set as claimed in claim 7, characterized in that: The diameter φ of the large diameter hole is 17mm±0.05 outside, and the diameter φ of the small diameter hole is 15.4mm±0.05 inside.

9. The graphite component for a two-piece set as claimed in claim 6, characterized in that: A side through hole is also provided on the side wall of the middle cone, and the side through hole is communicated with the large diameter hole.

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