MANUFACTURE OF COMPOSITE PIPE

摘要

PURPOSE:To prevent the release of the vinyl chloride resin applied to the inner peripheral surface of a metal pipe by the oxide film formed at the time of the welding of a metal sheet by directly spraying oxygen-containing inert gas to a weld bead part so that the temp. of the weld bead part becomes lower than the decomposition temp. of the vinyl chloride resin. CONSTITUTION:Inert gas is sprayed to a weld bead part from the nozzle 73 of a gas supply pipe 72 at a position where a vinyl chloride resin B is applied to the inner peripheral surface of a metal pipe 13 so that the temp. of the weld bead part of the metal pipe 13 vinyl chloride resin to prevent the thermal decomposition of the vinyl chloride resin B applied to the weld bead part. Since the weld bead part is cooled to predetermined temp. within a short time, the resin coated part can be allowed to approach a welding position and the resin flow part 62 and core part 63 supported in a cantilevered fashion within an inner resin mold 6 can be shortened and the weld bead part of the metal pipe 13 and the vicinity thereof are exposed to the inert gas atmosphere and the formation of an oxide film at these parts is suppressed. Further, 0.1-5.0vol.% of oxygen is added to the inert gas.