| 摘要 |
PURPOSE:To improve a working efficiency by bulging a heating part by applying the load in a compression direction with locally heating a blank pipe by a high frequency coil and continuously transferring it to the succeeding crest forming by repeating at a specific pitch the operation cooling it by a coolant. CONSTITUTION:A blank pipe 1 is set between a pair of rams 2a, 2b to position a high frequency coil 3. The pipe 1 is heated by impressing a high frequency current on the high frequency coil 3 and the heating part is gradually bulged by applying a compression load by descending the ram 2a simultaneously. Thereafter, the impressing of a high frequency current and the descent of the ram 2a are stopped and the bulging part is cooled by injecting a coolant from the exhaust nozzle 4 of the high frequency coil 3 immediately after to form a crest 5 with its bulging. Thereafter, said motion is repeated by moving the position of the high frequency coil 3 at a specified pitch to obtain the flare tube having the necessary number of crests. With this method, the thermal effect on a formed crest can be constrained less.
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