Abstract:The experimental study shows that the pull-in of the broad faces (rolling faces) of the EMC large aluminum alloy slabs mainly forms during the solidification process. The thermal bending moment caused by the thermal gradient of the solidified shell along the broad faces is the main reason for the formation of pull-in. The tangential forces resulted from the change of the solidification front curvature push the liquid metal of the solidification front from the hot section to the cold end and compensate the contraction of the cold end, thus form the irreversible deformation. Based on these mechanisms, the Tm-BD software system that can design the opening of molds was programmed. As an example, the straightness of the 1 300 mm×480 mm slab with the using mold opening was calculated. The agreement of the calculated and measured results provides the basis to optimize the mold design with or without opening.

Key words: straightness; solidification process; thermal bending moment; tangential push force