MANUFACTURE OF JOINT FOR BRANCH PIPE

PURPOSE:To thicken a flange part and to increase the height of the flange part as well by pulling out a conical or semi-spherical mandrel from the inside of a base pipe after thickening the base pipe and piercing a circular hole and forming the flange having an opening part. CONSTITUTION:The coil 9 for high frequency induction heating and a transformer 10 are set up at the branch pipe forming part of the base pipe 1 of a forming article, and at the pipe end part a stationary jig 7 and pressure jig 8 are arranged. The coil 9 is moved with pressurizing by passing a current and heating a heating part 11, and a thickening part 12 is formed on the base pipe. Then, after piercing a circular prepared hole 2 on the base pipe 1 thickened partially the base pipe 1 is fixed by a clamp 3 and the prepared hole part 2 is subjected to a burring with a conical mandrel 4. The mandrel 4 is pulled out via a rod 5 by a press, etc., a flange part 6 is formed and the forming of a branch pipe is performed. Consequently the branch pipe joint having less thickness reduction at the flange part 6 and higher flange part height can be manufactured.