FORMATION OF HOLLOW PIPE

PURPOSE:To improve workability and to simplify equipment by using a shape memory alloy for a packing material, bulging said material at the temp. below the transformation temp. and restoring the original fixed shape at the temp. above the transformation temp. CONSTITUTION:A packing material 10 is formed to a solid circular cylindrical shape at an ordinary temp. above the transformation temp. and is made into the fixed shape fitting into a cylindrical blank pipe 11. The material 10 in the fixed shape state at an ordinary temp. is inserted and packed into the pipe 11 and the assembly is housed into dies 12. The dies 12 have the shape to form a projection on one side of the pipe and are cooled to the transformation temp. or below so that the assembly is subjected to cold bulging. The assembly is rested at an ordinary temp. above the transformation temp. after the bulging and the material 10 restores the original fixed shape that said material memorizes. The material 10 restoring the fixed shape is extruded and discharged from the pipe 11 and the pipe 11 is formed as a hollow pipe having a projection.