The graphite crucible plays a very important role in industrial smelting. Enterprises engaged in graphite crucible processing and the application of graphite crucibles are not difficult to develop. Graphite crucible fracture is a difficult problem to solve. The reasons for graphite crucible fracture can be roughly divided into:
1. Processing defects
The symptoms of crucible breakage caused by this kind of reason are usually cracking from the joints and then spreading. Usually, cracks occur in a vertical direction. This type of problem is easier to detect after it occurs because it is so obvious. The main reason for this kind of problem is that the angle of the seam transition (usually 105° or 115°) is not used at the intersection point, and the rounding buffer is not used. In addition, the microscopic tearing of the crucible body by the tool tip part during the processing process, and the stress of the crucible itself during use, can cause cracks.
2. Design defects
Because of this, the crucible is usually broken at the joint between the lower part and the upper crucible. It is usually a transverse fracture, and the fractures on both sides are generally low, and the middle is high. If they are all cracked and then put together, it will be obvious that the joints at both ends cannot overlap. The real reason is that after use, the stress in the uniform upper part of the crucible wall and the gradually thicker lower part is concentrated in this part, causing stress concentration and causing the graphite crucible to break.
3. Improper use
This is mainly during the cooling and dismantling period. When pulling crystals, users will have the idea of shortening the heating time, cooling time, and furnace disassembly time. It is understandable and understandable to improve production efficiency. But whether the material, like graphite, can withstand this cooling rate needs to be considered. The strength of graphite materials will increase when the temperature increases. In other words, when the temperature decreases, the strength will decrease. If the temperature is cooled too fast, it should be considered whether the stress caused by the temperature difference between the outer wall and the inner wall exceeds the range that the crucible can withstand.
4. Raw material defects
This reason is actually the bigger reason. Because the physical properties of the graphite crucible itself are mainly due to thermal conductivity and thermal expansion, the crucible is prone to stress and is not easy to eliminate when it is rapidly cooled and heated. In addition, during the graphite production process, the pressing, impregnation, roasting, graphitization, and purification processes of graphite take a long time and are not easy to monitor and inspect. Although the overall performance is relatively uniform, there are still certain differences between various parts within the same piece of graphite, which indicates that graphite will fundamentally have certain problems.
5. Improper transportation, loading, and unloading
Transportation, loading, and unloading are mainly during the transportation process. This is related to the packaging of various thermal field manufacturers and also to the logistics company. However, most of them now choose to deliver goods themselves, and these reasons are gradually decreasing. Assembly and disassembly are mainly during the crystal pulling process, and dismantling of the furnace by novice assistants will occasionally occur.
Graphite crucibles have common characteristics with other graphite products. When choosing a graphite crucible, you still need to consider many factors to avoid unnecessary losses!