Patent ID: 8661869

Claim:
A method of stretch-forming, comprising: (a) providing an elongated metallic workpiece having a preselected cross-sectional profile; (b) providing a die having a working face with a profile adapted to receive and form the elongated metallic workpiece, the working face being complementary to the cross-sectional profile, wherein at least the working face comprises a thermally insulated material; (c) providing a resistance heater for electric resistance heating the workpiece to a working temperature; (d) providing movement elements engaging the workpiece for moving the die and a workpiece relative to each other to elongate and bend workpiece against the working face; (e) providing a radiant heater for applying radiant heat to one or more predetermined portions of the workpiece to increase the plastic elongation of the workpiece at the one or more predetermined portions; (f) resistance heating the workpiece to a working temperature by passing electrical current therethrough; (g) forming the workpiece against the working face by causing the workpiece and the die to move relative to each other while the workpiece is at the working temperature, thereby causing plastic elongation and bending of the workpiece and shaping the workpiece into a preselected final form; and (h) at one or more predetermined positions of the workpiece in relation to the die, applying radiant heat to one or more predetermined portions of the workpiece to increase the plastic elongation of the workpiece at the one or more predetermined portions.