High carbon silicon-killed steels can experience ladle and tundish nozzle clogging on a regular basis. Causes of the clogging are nonmetallic inclusions and cold liquid steel temperature. Making a liquid inclusion, minimizing the formation of spinels or absorbing a solid particle into the slag is key to preventing clogging problems. To avoid clogging problems, the operator must be aware of the following: If possible, minimize the aluminum level to 0.003 percent. Add calcium or calcium silicon wire or calcium silicon lump to liquefy aluminates. Maintain a Mn/Si ratio greater than 3.4 to one. Minimize white slag treatment time to reduce the formation of magnesium aluminate spinel. Reduce the ladle slag V ratio, and avoid using lime at the ladle furnace. Maintain the temperature measuring equipment and insure that operators follow a uniform temperature measurement protocol. Set up and enforce a practice to perform all of these steps on every silicon-killed low oxygen high carbon heat.
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