Method of forming a tubular blank into a structural component and die therefor

A method of forming an elongated blank into a structural component having a predetermined outer configuration, said method comprising:

• (a) providing a shape imparting shell formed from a low permeability, rigid material, said shell at least partially in the form of first and a second shell portions, each of which includes an inner surface defining said predetermined shape, an outer support and mounting surface and spaced lateral edges which edges define a parting plane between said two shell portions when said shell portions are brought together to at least partially form said shell;
• (b) providing a first die member with an upper side and a lower side and having a support framework for carrying said first shell portion mounted in said framework by a first cast compression force transmitting material with said laterally spaced edges of said first shell portion facing outwardly from said lower side of said first die member, said first cast material having different physical properties from said rigid material of said first shell portion;
• (c) providing a second die member with an upper side and a lower side and having a support framework for carrying said second shell portion mounted in said framework by a second cast compression force transmitting material with said laterally spaced edges of said second shell portion facing outwardly from said upper side of said second die member, said second cast material having different physical properties from said rigid material of said second shell portion, at least one of said first and second cast materials having a strength and hardness substantially less than said rigid material of at least one of said first and second shell portions;
• (d) placing said blank into said second shell portion in said second die member;
• (e) moving said first die member relative to said second die member to at least partially capture said blank in said shape imparting shell;
• and
• (f) forming said blank into said structural component by heating portions of said blank and forcing a fluid at a high pressure into said blank until said blank at least partially conforms to at least a portion of the inner surfaces of said first and second shell portions to form said structural component, said heating at least partially by induction heating.