Problems and solutions in the use of submerged entry nozzle

 

After summarizing the actual operating experience, the main reasons for the problems in the use of the submerged entry nozzle and the solutions were found.

Specifically in:
1) Fracture before or during the process of pouring steel at the nozzle. The submerged entry nozzle is about 1 meter long but only fixed by the upper part, so it is mechanically damaged during transportation, hard objects collide with the nozzle during installation, unstable or falling too fast when lifting the intermediate tank, and the impact on the nozzle during the pouring process causes the root fracture. In order to prevent the nozzle from breaking, mechanical collision should be avoided as much as possible during transportation and installation, and the problem should be stopped in time, and a layer of rubber pad should be placed on the intermediate tank seat frame to make the crane take off and land smoothly.
2) The slag line is eroded too quickly. After continuous casting of 7 to 8 furnaces, the slag line of the nozzle, especially the edge of the zirconium zone, was severely corroded and even fractured. Therefore, it is necessary to improve the corrosion resistance and hot and cold strength of the zirconium zone and the transition zone; increase the length of the zirconium zone from 160mm to 210mm, and modify the relative position of the zirconium zone, so that the problem of excessive corrosion of the slag line can be solved solve.
3) Steel seepage at the junction of the separation ring and the nozzle. After continuous pouring of 7 to 8 furnaces, most of the intermediate tanks have molten steel seepage at the junction between the separating ring and the nozzle, and the pouring should be terminated in severe cases. Since the overall submerged entry nozzle is longer and the conical surface at the junction of the nozzle and the separating ring is short, the lower part of the junction cannot squeeze the fire mud tightly. After the fire mud dries, it is easy to produce gaps and reduce the fixing force of the nozzle; In addition, it contains carbon. The product cannot be well combined with the fire clay used, and the spray paint on the upper edge dries and cracks along the outer edge of the nozzle. Based on the above reasons, the original high-aluminum fire clay was changed to aluminum-chromium fire clay. The upper outer edge of the nozzle was first coated with a layer of low cement castable that is easy to combine with the nozzle, and then a layer of paint. At the same time, careful operation is basically eliminated. The problem of pouring due to steel infiltration is solved.

4) Failure of pouring opening caused by nozzle installation. In the case of normal pouring operation, the stopper cannot be opened automatically, resulting in pouring failure. This is mainly due to the cold steel at the junction of the nozzle and the stopper rod, which bonds the nozzle and the stopper rod. In response to this phenomenon, increase the length of the nozzle and require a positive tolerance when making the separation ring. The installation of the nozzle must ensure that the immersion depth and the upper edge of the nozzle are 10-15mm above the surface of the bottom working layer of the tank. The temperature of the baking tank must reach 1050~1100℃. The phenomenon of cold steel in the nozzle is fundamentally solved.

Wanhao is a manufacturer who is specialized in designing various kinds of furnace and making refractory products for electric furnace, ladle, tundish, blast furnace, AOD furnace, IF furnace, etc.

Article Source:Problems and solutions in the use of submerged entry nozzle

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