Manufacture of resistance welded tube

TLDR: In this article, an induced current is generated on the open pipe 1 inserted into a work coil 52 for heating by applying a current of prescribed frequency to the coil 52 by the first heating power source 51.

Abstract: PURPOSE: To suppress the quantity of a bead discharged and to improve machinability of the bead and to improve working efficiency by heating both side edge parts of an open pipe up to the temperature above the Curie point by a first heating power source. CONSTITUTION: An induced current is generated on the open pipe 1 inserted into a work coil 52 for heating by applying a current of prescribed frequency to the coil 52 by the first heating power source 51. The vicinities of both side edge parts 1a and 1a of the open pipe 1 are preheated up to the temperature above the Curie point by the induced current. The current is then applied to a work coil 62 for welding by a second heating source 61 and both side edge parts 1a and 1a are heated up to the temperature above the sufficient melting temperature. Both edges 1a and 1a are then subjected to butt welding between squeeze rolls 3 and 3 to obtain the title resistance welded tube. By this method, the quantity of the bead discharged is suppressed and machinability of the bead is improved and working efficiency is improved. COPYRIGHT: (C)1990,JPO&Japio