There are five main reasons for graphite crucible fracture

Improper use. This is mainly during the period of cooling and demolition. When pulling the crystal, the user will have an idea of shortening the heating time, cooling time and dismantling time. It is understandable to improve the production efficiency. However, whether graphite can withstand this cooling rate has to be considered. Graphite materials will increase in strength when the temperature rises. In other words, when the temperature decreases, the strength will decrease. If the temperature is too fast, whether the stress caused by the temperature difference between the outer wall and the inner wall exceeds the range that the crucible can withstand, this must be considered.

Processing defects. The crucible fracture caused by this kind of reason generally shows that it cracks from the joint and then spreads. Usually split in the vertical direction. It is easier to find such problems after they happen, because they are too obvious. The main reason for this kind of problem is that the transition angle of the seam (usually 105° or 115°) at the intersection is not rounded to buffer, plus the microscopic tear of the tool tip to the crucible body during the processing, and The stress of the crucible itself during use causes cracking.

Improper transportation, handling, assembly and disassembly. Transportation loading and unloading are mainly in the transportation process, which is related to the packaging of various thermal field manufacturers and logistics companies. But now most of them choose to deliver goods by themselves, and such reasons are gradually decreasing. Assembly and disassembly are mainly in the process of pulling crystals, especially for novice assistants to dismantle the furnace occasionally.

Design flaws. Because of this reason, the performance of the crucible after fracture is generally at the junction of the r part and the upper crucible, generally transverse fracture, and generally the fracture on both sides is low and the middle is high; if it is all cracked and then put together, the two ends can be clearly found The joints cannot overlap. The real reason is that after use, the stress of the upper part of the crucible with uniform wall thickness and the gradually thickening part of the lower part is concentrated in this part, causing stress concentration, and finally causing the graphite crucible to break.

Material defects. This reason is actually the biggest reason. Because the physical properties of the graphite crucible itself are mainly caused by heat conduction and thermal expansion, the crucible is prone to stress and is not easy to eliminate when the crucible is rapidly cooled and heated; in addition, in the graphite production process, the compression, The process of impregnation, roasting, graphitization and purification takes a long time and is not easy to monitor and inspect. Although the overall performance is relatively uniform, there are still some differences between the various parts of the same piece of graphite, which determines that graphite will fundamentally exist Certain problems.