The sizing nozzle jacket is a component of the sizing nozzle, which is usually made of refractory materials or heat-resistant alloy steel. It plays the role of protecting and fixing the sizing nozzle core and adapting the installation structure. The following is a detailed introduction from many aspects:
Refractory jacket: Like the high-aluminum jacket, the sizing nozzle core (such as zircon-zirconia composite core) is sealed with a high-temperature fire mud layer, and the fire mud is used to fill the gap and provide a certain bonding force to combine the two into a whole. For example, the mosaic sizing nozzle, the main jacket made of high-aluminum material wraps the zirconium nozzle core, which is low in cost, but attention should be paid to the bonding problem between the core and the jacket, otherwise the core is easy to fall off.
Heat-resistant alloy steel jacket: The jacket of some quick-change nozzles is made of heat-resistant alloy steel, which has good toughness and is connected to the nozzle zirconium core through the fire mud layer. Because the inner wall of the steel jacket is relatively smooth, the disintegration of the zirconium core is better than that of the refractory jacket, which is convenient for replacing the zirconium core and can be recycled many times, reducing costs and solid waste.
Structure: It usually consists of a sizing water inlet, a quick-change water inlet and a quick-change mechanism. The quick-change water inlet generally has a tubular water inlet zirconium core, and its molten steel inlet is a trumpet-shaped structure with a large top and a small bottom. From the trumpet-shaped structure to the molten steel outflow end, the molten steel flow channel is a cylindrical structure. In order to facilitate replacement and reuse, there is also a water inlet circulation jacket, which is mostly made of heat-resistant alloy steel. The water inlet zirconium core is set in its axial through hole, and the two are sealed and connected by a fire mud layer.
Working principle: The sizing nozzle quick replacement device has a nozzle moving slideway, and the nozzle and spare nozzle in the working state are both positioned in the slideway. When the nozzle needs to be replaced, the spare nozzle is pushed from the spare position to the working position through a hydraulic drive device, a lever principle or manpower, etc., to replace the eroded old nozzle, so that the new nozzle is connected to the upper nozzle in the seat brick, and the molten steel flows into the casting mold through the new nozzle, thereby realizing the rapid replacement of the sizing nozzle during the continuous casting process.
In the high temperature of continuous casting and the erosion and erosion of molten steel, it protects the internal sizing nozzle core, reduces the direct impact and chemical erosion of molten steel and slag on the core, and prolongs the overall service life of the sizing nozzle. For example, when the tundish is cast, the molten steel flows out of the nozzle, and the jacket bears part of the thermal stress and erosion, and the structure of the protective core is stable.
Provide an installation foundation for the sizing nozzle, so that it can be accurately installed in the designated position of the tundish and other equipment, ensuring that the nozzle and other components (such as the upper nozzle) are precisely matched, so that the molten steel flows according to the predetermined path and flow rate. For example, some jackets are designed with specific shapes (such as the upper positioning section is a cuboid/cylinder, and the lower fixed section is a step/truncal table), which is convenient for positioning and fixing in the tundish, ensuring that the upper and lower nozzles are aligned when the molten steel is cast, and the flow rate is stable.
Jackets of different materials assist in optimizing the performance of the sizing nozzle. For example, the heat-resistant alloy steel jacket, with a thermal expansion coefficient that matches the zirconium core of the nozzle, can reduce the internal stress caused by the large expansion difference between the two when the temperature changes, and reduce the risk of nozzle cracking; the thermal conductivity and other characteristics of the refractory jacket will also affect the overall heat transfer and thermal stability of the sizing nozzle.
