PURPOSE: To eliminate an usual heat treatment by cooling a bent part from the inside after bending a heated pipe.
CONSTITUTION: A rotary arm 5 is turned to a position adjacent to an induction heating coil A and fixes a pipe 17 by a fixing head 6. The pipe 17 is heated locally via an induction heating device 4 and pressed to drive it via a driving head 3 in an arrow direction A in such state that the arm 5 moves to a position where pipe- bending work of 90° is completed. In this case, bending process is performed by a guidance of the head 6 while the pipe 17 is softened by heating. Ant at the time when the pipe 17 is bent at distances S1, S2 away from the ends of the coil 4A and at high temperature, a bending process is performed while quenching the pipe 17 from the inside by a cooling medium 9. As a result, compressive stress is generated in the inside of the pipe and tensile stress in the outside, so that heat treatment to relief residual stress in fabrication is omitted.
SHIMIZU TASUKU
KOIKE AKIMASA
YONEMURA HIDEO
HASEGAWA KUNIO
