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A crucible is a vessel or melting pot made of highly refractory materials such as clay, graphite, porcelain, etc. It serves as a refractory container and a holding vessel for industrial kilns and furnaces. It is primarily used for the evaporation, concentration, crystallization of solutions, and the burning of solid substances. Depending on the material, the most commonly used types of crucibles in the market include alumina (aluminum oxide) crucibles, zirconia crucibles, silicon carbide crucibles, quartz crucibles, graphite crucibles, and others.
Table of Contents
1.Specific Damage Description of Silicon Carbide Crucibles
In the case, silicon carbide crucibles, made from high-purity silicon carbide SiC, were used in the steelmaking industry furnaces. After usage, cracks and breakage occurred in the waist region of the crucibles.
2.Cause analysis of Silicon Carbide Crucibles
The damage to crucibles commonly falls into two categories: mechanical damage and thermal stress-induced damage. Mechanical damage, while related to the mechanical strength of the crucibles to some extent, is often not realistically reducible by increasing the crucible’s inherent strength, especially if the crucible is not excessively porous. According to the investigation, this batch of silicon carbide crucibles was not an isolated case; crucible breakage occurred in similar positions in crucibles from different batches and regions. This led us to examine the furnace itself.
We found that the internal design of the furnace was a contributing factor. The furnace chamber dimensions were designed to be too small, there were too few and unevenly distributed support points for the crucible, and the airflow for heating the silicon carbide crucible was unevenly distributed. When an object is placed in an uneven temperature field, it is subjected to uneven heating or cooling.
As a result, the object’s surface experiences significant contraction, leading to the development of tensile stress on the surface and compressive stress inside. If the object is brittle (such as silicon carbide crucibles), cracks will form on the tensile surface when the stress exceeds the tensile strength. Over time and through repeated cycles, this can lead to fracture and breakage. In this environment, certain areas of the silicon carbide crucible may be subjected to overheating, causing them to crack.
Additionally, during the preheating phase, a design flaw in the furnace led to excessive negative pressure in the preheating zone of the furnace. Cold air entered the furnace in large quantities from the bottom of the furnace door, resulting in uneven preheating of the upper and lower parts of the silicon carbide crucible. When subjected to rapid temperature increases after preheating, the crucible could not withstand the thermal stress generated, leading to its rupture.
3.Improvement measures
- Optimize Furnace Design: The importance of internal furnace design in steelmaking furnaces cannot be overstated, as it directly impacts the service life and safety of silicon carbide crucibles. The design should consider multiple factors, including temperature distribution, thermal stress, atmospheric conditions, support methods, and material characteristics. This ensures that the crucibles can operate stably in high-temperature environments, preventing issues like cracking.
- Standardize Operations: To prevent mechanical damage to silicon carbide crucibles, it’s essential to standardize on-site operations during both production and assembly. Upgrading the packaging can protect the crucibles from mechanical impacts and collisions.
Conclusion
In conclusion, if a crucible encounters various issues such as breakage during use, it is influenced by multiple factors. Specific investigations and determinations need to be made based on the on-site conditions and the characteristics of the product itself. If you are looking for crucible products, feel free to browse our related products or contact us directly.
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