Method for blow molding metal containers

A method of pressure molding a shaped metal container of a desired shape from a metal preform having a cylindrical body with an open end and a closed end, the method comprising:

• generating an electro-magnetic field;
• shock annealing at least one region of the metal preform by exposing the preform to the electro-magnetic field for inductively heating material of the preform to generate a temperature rise in the material of the preform of at least 120° C./sec to reach an annealing temperature in the range of 65% to 98% of the melting point temperature of the material of the preform;
• subsequently applying and curing a coating on at least one of an interior surface of the preform and an exterior surface of the preform, to create a coated preform;
• differentially preheating the coated preform, wherein the differentially preheating the coated preform comprises sequentially inductively heating first and second regions of the coated preform with an electro-magnetic field by sequentially exposing the first and second regions to the electro-magnetic field by moving at least one or both of the coated preform and the field relative to one another;
• subsequently fluid pressure forming the coated preform in a mold with a mold cavity defining the desired shape by pressurizing the coated preform to expand the coated preform into contact with the mold cavity for imparting the desired shape onto the coated preform, wherein at least one of the first and second regions is subject to elevated three dimensional deformation during the fluid pressure forming;
• removing the resulting molded container in the desired shape from the mold;
• and
• wherein the metal preform is shock annealed prior to insertion into the mold.