Abstract: Automatic welding apparatus for making uniform welds around the perimeter of a polygonal shape made up of a succession of flats and arcuate corners is described in connection with a tubular hexagonal workpiece which is rotated about its longitudinal axis beneath a welding torch assembly. The distance of the welding electrode above the workpiece is maintained as preselected by automatic voltage control means. The welding electrode is automatically maintained perpendicular to a tangent to the surface of the workpiece and extending in the plane of the weld line by oscillating the welding torch assembly so that its longitudinal axis describes an arc having its center on the longitudinal axis of rotation of the workpiece in synchronization with the rotation of the workpiece. Synchronization is provided by means of an annular cam surface which is rotated in predetermined relation to the workpiece and which controls the oscillation of the welding torch assembly.

Abstract: A process for making tubes, channels and other relatively thin-walled elongated shapes having a unique degree of dimensional accuracy and stability in which the part after being shaped and only approximately sized is mounted on a mandrel having a larger coefficient of thermal expansion than the part. The mandrel and the part are connected at their opposite ends so that expansion of the mandrel first causes elongation and concomitant lateral shrinkage of the part and then lateral expansion of the part so that it is triaxially hot worked to bring it to its final hot size from which the part contracts to its finished size at room temperature. For maximum freedom from residual stresses and dimensional stability thermal sizing is carried out by heating to a temperature at least just above the recrystallization temperature of the part.