Preparation method of ultrahigh-strength automobile steel

The invention relates to the technical field of metal materials, in particular to a preparation method of ultrahigh-strength automobile steel. The method comprises the steps that molten steel is smelted, the fluctuation range of chemical components of the molten steel in the smelting process is controlled, then continuous casting is conducted, and a casting blank is obtained; the casting blank is subjected to first heating, rough rolling, edge heating compensation operation after rolling and finish rolling, and a hot-rolled plate is obtained; carrying out laminar cooling on the hot-rolled plate by adopting edge shielding operation, and then coiling; carrying out first heat preservation on the coiled hot-rolled plate, and then carrying out cold rolling to obtain cold-rolled strip steel; and the cold-rolled strip steel is continuously annealed, and the ultrahigh-strength automobile steel is obtained. Wherein the continuous annealing comprises the following steps: heating the cold-rolled strip steel in stages, a