Abstract: For the manufacture of heat exchanger tubes having a metal strip (tangential surface) welded to the surface of the tube, the metal strip is fastened to the surface of the tube by through-welding with welding current of alternating value.

Abstract: A metal wire or rod is passed between two rolls one inside the other but with offset axes. The larger outer roll which may be ring-shaped has a smooth inside contact surface. The smaller internal roll has a smooth outside contact surface. Together, these two eccentrically disposed surfaces form a long converging throat between them through which the wire or rod is passed as it is being rolled into a strip. The opposing, smooth surfaces have a separation at the closest point which is less than 1/3 the diameter of the metal wire or rod to be fed between them. The distance between the point where the wire first contacts the opposing, smooth contact surfaces of the converging throat and the closest point of separation between the opposing surfaces is preferred to be at least four times the original diameter "D" of the wire or rod being fed therethrough.

Abstract: An improved construction of an extrusion press for producing an extruded tube is disclosed, the press including a billet chamber and a ram adapted to drive a billet through the billet chamber, a sizing means comprising an annular die, and a mandrel for sizing the wall thickness of the tube. The improved construction including a mandrel support means attached to and concentrically extending from the front face of the mandrel for maintaining continuous coaxial alignment of the mandrel with the die, prior to and during the extrusion operation.