Producing Superplastic Tubular Tee-Joints by Thermoforming

A new process to produce tubular tee-joints from straight lengths of superplastic tubes is presented. The process is achieved by holding one straight superplastic tube inside a split-die composed of two cylindrical cavities perpendicular to each other; thus making-up the required tee-shaped cavity. By applying pressure inside the superplastic tube at the appropriate temperature, only the lateral bulging of a small portion of the tube wall is allowed. After trimming the bulged zone, the tee-joint is realised by butt-welding of a second straight tube along the trimmed contour.