PURPOSE: To prolong the life of a work coil by avoiding a discharge phenomenon based on the intervention of magnetic powder in a space between an induction heating coil (work coil) and a tube.
CONSTITUTION: A metallic band plate is fed in the longitudinal direction and as granular body 3 is supplied into the tube as far as a welding point along the tube 1 leaving a void, the metallic band plate is formed into a tubular shape and high frequency induction welding is performed by an induction coil 7 enclosing the tube with a gap to the tube to edge surfaces facing each other in the opening extending along the longitudinal direction. In this manufacturing process, magnetic powder stuck on the outer peripheral surface of the tube 1 on the upstream side of this induction heating coil 7 is removed.
HASHIMOTO HARUJI
ONO TORU
