GB684381A - - Google Patents

Abstract

684,381. Making metal tubes. BUNDY TUBING CO. March 15, 1951, No. 6229/51. Classes 83 (ii) and 83 (iv). [Also in Group XXVIII] In a continuous method of making a metal tube, strip stock is bent into tubular form, the overlapping or abutting edges are tackwelded, brazing metal is applied and the tube passed through a heating zone to braze the seam between the welds. Strip 1 is drawn by feed rolls 31 from a reel 2 through tube-forming rolls 3 and the seam is tack-welded between roller electrodes 10, 11. Brazing metal in the form of a wire 13 is applied to the seam from a reel 14 by a metallizing gun 15 which sprays molten metal on to the seam. The tube then passes through a resistance heating furnace 20 to braze the seam and finally passes through a jacketed cooler 28. Non-oxidizing gas is fed through a pipe 26 to the furnace and to the interior of the tube through a pipe 34 at the forming rolls 3. In modifications of the apparatus a strip of brazing metal is fed directly to the seam from a reel and may be tack-welded by a roller or fusion-welded by an electrode to locate it on the tube before entering the furnace. The strip of brazing metal may alternatively be fed inside the tube at the forming rolls 3 so that in addition to brazing the joint it forms an internal coating to the tube. In a further modification the brazing metal is in powdered form mixed with a mineral oil and is fed as a paste to the seam.