1. Processing defects
After the crucible is broken due to such reasons, it usually cracks from the joint and then spreads. It usually splits in the vertical direction. Such problems are easier to find after they occur, because they are so obvious. The main reason for this kind of problem is that the angle of seam transition (usually 105° or 115°) is at the intersection point, and no rounding buffer is used, plus the micro-tearing of the tip of the knife to the body during processing, and The stress of the crucible itself during use causes cracking.
2. Design flaws
For this reason, the performance of the crucible after fracture is generally at the junction of the r part and the upper crucible, which is generally a lateral fracture, and generally the fractures on both sides are low and high in the middle; if they are all split together and then put together, you can obviously find the two ends The spelling interface cannot overlap. The real reason is that after use, the stress in the upper part of the crucible with uniform wall thickness and the lower part of the thickening part are concentrated in this part, causing stress concentration and causing the graphite crucible to break.
3. Improper use
This is mainly during the period of cooling and cooling to dismantle the furnace. When users pull crystals, they will have the idea of shortening the heating time, cooling time and furnace dismantling time, and it is understandable to improve production efficiency. But whether the graphite material can withstand this cooling rate should be considered. When the temperature of graphite material increases, the strength will increase. In other words, when the temperature decreases, the strength will decrease. If the temperature drops too fast, whether the stress caused by the temperature difference between the outer wall and the inner wall exceeds the crucible's range can be considered.
4. Raw material defects
This reason is actually a larger reason. Because the physical properties of graphite crucibles are mainly due to heat conduction and thermal expansion, the crucibles are prone to stress and are not easy to eliminate under the condition of rapid cooling and rapid heating; in addition, during the graphite production process, the shape of graphite, The process of immersion, roasting, graphitization and purification takes a long time, and it is not easy to monitor and test. Although the overall performance is relatively uniform, there are still certain differences between the various parts within the same graphite, which determines that graphite will basically exist Certain problems.
5. Improper transportation, loading, unloading and disassembly
Transportation loading and unloading is mainly in the transportation process, which is related to the packaging of various hot-field manufacturers and logistics companies. But now most of them choose to deliver their own products, and these reasons are gradually decreasing. Assembly and disassembly are mainly in the crystal pulling process, especially for novice assistant workers to dismantle the furnace occasionally.
Graphite crucibles have common features with other graphite products. The selection of graphite crucibles still needs to consider various factors to avoid unnecessary losses!
