Mechanism of the evolution and refinement of the primary Si in A390 alloy was analyzed based on rapid solidification and the heredity theory of liquid structures in A390 alloy billets in the case of the near liquidus semi-continuous casting . Influence of the pouring temperature from 10 ℃ to 100 ℃ above the liquidus on the morphology of the primary Si in A390 alloy was investigated under the conditions of casting velocity 120 mm/min and cooling water flux 0.05 m3/min. The results show that the near liquidus semi-continuous casting process is in favor of uniform nucleation and abnormal growth restraint of the primary Si due to an appropriate match in rate of the nucleation and growth. The morphology and distribution of the primary Si in the alloy can be improved by controlling the casting parameters without adding the refiner and modifier to the melt

showing great significance to the processing simplifying

resource saving and cost reducing.