Preparation method of large-size aluminum alloy ingot

The invention discloses a preparation method of a large-size aluminum alloy ingot, relating to a preparation method of aluminum alloy ingots, and the provided preparation method of a large-size aluminum alloy ingot solves the problem of easy cracking during preparing the large-size aluminum alloy ingots by the traditional aluminum alloy ingot preparation method. The method comprises the following steps of: spreading and scattering a NO. flux at the bottom of a smelting furnace; adding aluminum ingots, electrolytic copper, zinc ingots, aluminum-silicon intermediate alloy, aluminum-iron intermediate alloy, aluminum-manganese intermediate alloy, aluminum-chromium intermediate alloy and aluminum-titanium intermediate alloy into the smelting furnace and spreading and scattering a covering agent; heating to ensure that the materials are smelted, sequentially adding a zirconium composite salt and magnesium ingots as well as smelting and refining to obtain an aluminum alloy melt; filtering the aluminum alloy melt and then pouring into a crystallizer; and finally, obtaining the large-size aluminum alloy ingot through casting. The thickness of the ingot prepared by using the method is 500-600mm, the width is 1,600mm, and the length is 1,500-2,500mm. The ingot has no cracks, good surface quality and uniform internal grains, and the yield is not smaller than 65 percent.