Publish Time: 2024-03-12 Origin: Site
The submerged entry nozzle (SEN) plays a pivotal role in the continuous casting process of steel, acting as a critical conduit that directs molten steel from the ladle into the tundish or mold. Despite its significance in achieving a stable and controlled flow of steel, ensuring the quality of the final product, SEN operations are fraught with challenges. These issues not only impact the efficiency of the casting process but also affect the quality of steel produced. This article delves into the primary problems associated with SEN operations, exploring their causes, consequences, and potential solutions.
One of the foremost issues plaguing SEN operations is the susceptibility of the nozzle to mechanical damage and fractures. Given its construction, the SEN is a fragile component, about 1 meter in length, and is only secured at the top. This design makes it particularly prone to breakage during transportation, installation, or even throughout the casting process. Collisions with hard objects, improper handling, and the impact of the pouring process itself can lead to fractures at the root of the nozzle.
To mitigate these risks, several precautions must be taken. Firstly, minimizing mechanical collisions during transportation and installation is paramount. This can be achieved by adopting careful handling procedures and using protective measures such as rubber padding on intermediate tank seat frames. These steps help ensure a smoother operation of the crane, reducing the likelihood of impacts that could cause damage to the SEN.
Another significant challenge is the rapid erosion of the slag line on the SEN, particularly in the zirconium zone. After continuous casting of several heats, the slag line and the edge of the zirconium zone undergo severe corrosion, leading to potential fractures. This erosion compromises the integrity of the SEN, affecting the quality of the steel being cast.
Addressing this issue involves enhancing the corrosion resistance and thermal strength of the materials used in the SEN, specifically around the zirconium and transition zones. Increasing the length of the zirconium zone and adjusting its position relative to the rest of the nozzle can also contribute to solving this problem. These adjustments ensure a more durable slag line capable of withstanding the harsh conditions of continuous casting.
The junction between the separating ring and the SEN is a critical point prone to molten steel seepage, especially after the continuous pouring of multiple heats. This seepage is largely due to the inability of the junction's design to tightly compress the refractory mud, leading to gaps and reduced nozzle fixation. The presence of carbon in the products used for sealing further complicates the issue, as it does not bond well with the fire clay, leading to cracks and eventual seepage.
To counteract this problem, switching from high-aluminum fire clay to aluminum-chromium fire clay is recommended to improve the seal. Additionally, applying a layer of low cement castable that bonds effectively with the SEN, followed by a compatible layer of paint, can significantly reduce the risk of steel infiltration. These measures, combined with careful operation, effectively address the issue of steel seepage.
The challenges faced in the operations of submerged entry nozzles are diverse and impact the efficiency and quality of the continuous casting process. From mechanical damage to rapid erosion and seepage issues, each problem requires a nuanced understanding and strategic approach to mitigate. By implementing the recommended solutions—ranging from improved handling and protective measures to material enhancements and design adjustments—the integrity and functionality of the SEN can be preserved, ensuring a smoother, more reliable casting process. As the steel industry continues to evolve, so too must the technologies and methodologies employed in every step of the manufacturing process, with SEN operations being no exception.