FORMING METHOD FOR PRECISION METALLIC TUBE

摘要

PURPOSE:To unify a stress and to reduce the residual stress by applying the shaft compressing force more than the yielding stress of a blank by reducing the inner pressure after setting a work inside the metal die to form an angular metallic tube and bulge-forming the shaft compressing force and inner pressure by synchronizing. CONSTITUTION:A metal die 1 is quadrifidable with the divided lines intersecting each other at right angles and the hole formed along the center shaft has each rectangular side on its cross section forming the shape curving to the center shaft side. A work is inserted into this metal die 1, a pressing rod 2 is applied from both end parts of the work 3 with a shaft compressing force F and a bulging formation is performed by applying an inner pressure P simultaneously. The shaft compressing force is then increased by reducing the friction force between the metal die 1 and work by reducing the inner pressure as far as possible to reduce the residual stress which is after the bulge forming. The enlarging deformation to the outer side due to the secular change can be controlled as well by reversing the residual stress so as to work to the inner side by forming in a flat shape and by pressing from the inner side each side wall recessed to the inner side.