Abstract: The characteristics of rim cracks and inclusions in the wheel were analyzed,it was shown that the type of fatigue cracks was caused by the aggregated large-size inclusions in the steel.These inclusions originated from the aggregated attachments on the inner wall of the nozzle. In the casting process, the endogenous inclusions in the molten steel aggregated and adhered on the inner wall of the nozzle, the inclusions would fall off randomly and remained in the billets during solidification.These large inclusions were distributed at the position of 20-40 mm from the surface of the continuous casting billet, which were distributed in the wheel rim area after wheel rolling, located at 10-20 mm below the tread. The sizes of inclusions generally exceeded 500 μm, and the main composition was calcium aluminate. For the process optimization of calcium treatment and electromagnetic stirring and shielding casting in the overall process of continuous casting, the aggregation and attachment of inclusions on the inner wall of nozzle have been effectively controlled. The stability of continuous casting and the wheel quality have been significantly improved. The total number of large-sized inclusions was reduced by more than 76 % and the number of inclusions larger than 1 mm was greatly reduced to 8 % from 35 %.

Key words: fatigue cracks, aggregated inclusion, nozzle clogging, shielding casting