METHOD OF CORRECTING METAL TUBE AND CORRECTING PRESS METAL DIE

摘要

The forming recesses (1, 3) of a lower die (2) and an upper die (4) are formed to have a semi-oval profile so as to provide a forming space S almost oval in section with the dies closed. The parting line L between the lower die (2) and the upper die (4) is deviated as much as h from the major axis b of the forming space S toward the upper die (4) side, and the opening width of the forming recess (1) of the lower die (2) is set to be slightly larger than the opening width of the forming recess (3) of the upper die (4). A metal bent tube is plastic-deformed into an almost oval shape in section by closing the dies while being compressed in a peripheral direction by the lower and upper dies (2,4) to eliminate spring-back caused by bending, whereby the buckling and pinching toward the outer side of the tube wall is prevented by the expanded portion (2a) of the lower die (2) and buckling toward the inner side of the tube wall is prevented by a step difference formed by the difference in opening width between the lower die (2) and the upper die (4).