METHOD FOR RELIEVING RESIDUAL STRESS OF METALLIC PIPE

摘要

PURPOSE:To form a pipe having high accuracy with low residual stress by forming the pipe to a prescribed size by bulging in a metallic mold then exerting axial compressive load thereto in the state of exerting a low pressure to the pipe in order to prevent buckling within the same metallic mold. CONSTITUTION:A pipe stock 2 is inserted into the metallic mold 3 and is restrained by a pressurizing rod 4. The axial compressive load F1 is exerted via the rod 4 to the pipe 2 to seal the pressure P in the pipe 2. The pipe is subjected to bulging by maintaining the axial compressive load F1 and the pressure P under prescribed conditions. The axial compressive load F1' is then exerted to the pipe to deform plastically the pipe while the pressure P1 lower than the pressure P exerted to the pipe in the stage of bulging is kept exerted to the pipe. The pipe 2 is plastically defomred uniformly over the entire region in this stage and therefore the residual stress generated prior to the bulging or during the bulging is redistributed and is thereby decreased.