Homogenizing annealing stepped cooling process for aluminum alloy cast ingot

The invention relates to a homogenizing annealing stepped cooling process for an aluminum alloy cast ingot, and relates to the field of aluminum alloy casting. The homogenizing annealing stepped cooling process for the aluminum alloy cast ingot comprises the steps of (1) heating the cast aluminum alloy cast ingot from room temperature to 560 DEG C in 6 hours, and conducting heat preservation for 10 hours; (2) adopting the cooling process to cool the aluminum alloy cast ingot subjected to heat preservation for 10 hours in the step (1) to 440-460 DEG C at a cooling speed of 190-200 DEG C/h; (3) adopting the cooling process to cool the aluminum alloy cast ingot obtained in the step (2) to 150-160 DEG C at a cooling speed of 240-260 DEG C/h; and (4) adopting the cooling process to cool the aluminum alloy cast ingot obtained in the step (3) to room temperature at a cooling speed of 110-120 DEG C/h. According to the homogenizing annealing stepped cooling process for the aluminum alloy cast ingot, when the aluminum