Two types of slivers are clearly identified on cold rolled sheet: alumina clusters and mold slag droplets. Both oxides inclusions are trapped in the first millimeters of the solidified shell in the upper part of the mould due to the variations of different parameters such as superheat in the tundish, mold slag properties, mold and nozzle geometry, casting speed. These defects are formed in the CC machine but only observed on the final product by automatic surface inspection system. Lanthanum tracing helps to determine the origin of the alumina clusters, de-oxidation or re-oxidation, during continuous casting. The distribution in the width of the slab of the two types of slivers is observed to be different. Various industrial results are discussed: 1. an increase of the slab thickness leads to the reduction of slivers index as the steel flow is modified, 2. an increase of the mold slag viscosity leads to a decrease of the slivers index, 3. a modification of the oscillation mode has a little effect on the quality index.
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