Method of making a gas-tight connection between a corrugated high

Abstract

A gas-tight connection is achieved by fusion bonding a flanged end portion of a thin walled, corrugated metallic tube onto a flanged interior surface of a metallic sleeve whose interior surface includes helical threads that correspond to the helical corrugations on the outer surface of the metallic tube. The method disclosed comprises screwing the sleeve onto the tube to a position and orientation whereat the flanged interior surface of the sleeve faces, but is longitudinally separated from, the end portion of the tube to which it is to be bonded. The end portion of the tube is then decorrugated and expanded; a clamping tool is coaxially positioned about such end portion of the tube, a forming mandrel is axially positioned within such end portion, and the clamping tool is tightly closed so as to flange such end portion in a manner to parallel the flanged interior surface of the sleeve. The clamping tool and forming mandrel are removed and the sleeve is screwed toward the end portion of the tube so that such parallel flanged elements engage each other. The thin walled tube is then fusion welded onto the flanged interior surface of the sleeve, by the application of a welding arc or flame to the interior surface of the flanged end portion of the tube, the sleeve in of itself acting as a heat sink.