GB643816A - Improvements in or relating to the welding of seams in metallic tubing - Google Patents

Abstract

643,816. Electric welding. GENERAL ELECTRIC CO., Ltd., BAKER, W. F., and SPENCER, J. R. April 15, 1948, No. 10517. [Class 83 (iv)] In welding a seam in tubing &c. a line contact or line contacts in series is or are formed between the opposing faces of the seam within the thickness of the parts, either by shaping one or both faces of the seam or by placing a conducting wire between the faces, and inducing in the parts a high-frequency welding current which flows across the seam through the line contact or contacts. The welding current is induced by passing the tubing through a high-frequency induction heating coil 2 and pressure rolls 5 may be used to force the faces of the seam together, or the differential expansion due to the concentration of the heating from the induced current on the outer skin of the tubing may be relied on for this purpose. The line contact between the seams may be produced by having a tapered projection 6 on one or both faces or by placing a wire 3 between the two faces, which may then be slightly concave in order to grip the wire. The wire may be heated to near its melting point, as it is fed between the faces, by current supplied through a guide roll 4 and the rolls 5. The projections 6 are so placed radially that, after welding, no ridge is left on the inside of the seam and, if there is a projection on each face, they may abut or may overlap slightly so that a mechanical pressure, acting in a radial direction, is caused between the faces, the tubing being slightly unsymmetrical until after it is welded.