The filling speed in gravity casting refers to the flow rate of the melt entering the cavity through the gate in unit time. The filling speed of common aluminum alloy melts is 0.4~0.6 m/s. When the melt is filling, there is an oxide film at the front end. A reasonable filling speed can ensure the smoothness of the melt flow and the integrity of the oxide film, that is, no oxide slag will be formed due to turbulent flow [28]. When the filling speed of the melt is too high, the melt will break through the oxide film on the surface, causing the oxide film to crack and roll back, forming oxide slag inclusions, which has a great impact on the final mechanical properties of the casting, especially the fatigue performance of important castings. When the filling speed of the melt is too small, the heat loss of the melt itself is large, the solidification proceeds early, and the cavity cannot be filled completely.