| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a quality hollow prismatic metal tube free of bending or twisting from a hollow cylindrical welding metal tube. SOLUTION: A hollow cylindrical metal tube 13 which is prepared by butting and welding both ends of a metal strip 11 is made pass through a roller die 14 which is formed by disposing facing two pairs of rollers in a cross shape. The hollow cylindrical metal tube 13 is pressed toward the center from a sideway 4 direction to be molded into a hollow prismatic metal tube 15 without causing a surface reduction. The metal tube 15 immediately after molding is further inserted through a roller-type straightening device 16 to correct bending or twisting of the metal tube 15 generated in the molding process. COPYRIGHT: (C)2007,JPO&INPIT
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