Experimental and simulation studies of layer casting on industrial-scale Al-4.5 wt Pct Cu ingot: Effect, defect, and optimization

Abstract

Macrosegregation is an inevitable defect in large ingots, which intensifies with the increase in ingot size and directly affects the performance of the final product. Though the previously proposed layer casting (LC) process has been successfully conducted to alleviate the macrosegregation in the additively casted laboratory-size ingots, due to macrosegregation showing strong sensitivities to the ingot size, it is still doubtful whether this new approach could still work as expected in actual industrial-scale ingots. In this research, we have studied the effects of LC on macrosegregation and the utilization rate in Φ240 mm× 690 mm Al-4.5 wt pct Cu ingots. The experiment results show that the macrosegregation index is significantly reduced and the utilization rate is greatly improved in the industrial-scale ingot using LC approach. Different from the laboratory-size LC ingots, incomplete fusion defects are found at the interlayer in the current LC ingots, which are caused by insufficient remelting at the edge of the ingot and the oxide film formed on the surface of the previous layer. Periodic negative segregation is formed at the bottom of the multi-layers, which is attributed to the extra nucleation induced by the multi-pouring process. Subsequently, an optimised design is proposed to reduce incomplete fusion defects, and the efficiency is confirmed by the simulated results. This study provides a possible technique approach for promoting the homogenization level of large ingots.