US Patent 11040387 Method for blow molding metal containers

A method is disclosed for pressure forming a metal preform including shock annealing of the preform and subsequently preheating the preform prior to pressure forming. Shock annealing may be carried out as differential shock annealing in which different regions of the preform are annealed to different degrees. Preheating may be carried out by differentially preheating, optionally shock preheating, different regions of the preform for preheating at least those regions of the preform which will be subject to elevated expansion during pressure forming. Shock annealing by induction heating can lower energy consumption, reduce processing times and allow for larger expansion of the preform.