GB653668A - Method of making metal tubing - Google Patents

Abstract

653,668. Making compound tubes. ARMCO INTERNATIONAL CORPORATION. June 10, 1948, No. 15722. [Classes 83 (ii) and 83 (iv)] Angular bending; brazing.-In a continuous process for making seamed tubes by forming and brazing one or more coated strips, lubricant applied for the forming process is decomposed during brazing and removed in the form or gaseous hydrocarbon by introducing hydrogen into the tube before it reaches the brazing zone. One at least of the strips is of copper nickel alloy and one at least of the faces to be united is copper-coated. The strip stock 15, Fig. 1, is passed through a lubricating bath 16 to forming rolls 17 intermediate of which hydrogen, preferably wetted by water vapour, is introduced into the tube through a hollow mandrel 30 or other conduit before the tube is closed over the mandrel by the final set of forming rolls. The tube then passes between electrodes 20, 21, 22 and rollers 24 where it is heated rapidly to a brazing temperature in the range between 1225‹ and 1300‹ C. before it finally passes through a cooler 25. A tube may be rolled from a single strip preferably of an alloy substantially the same as that known under the Registered Trade Mark " Monel." The strip is rolled through 720 degrees to form a two-ply tube 1, 2, Fig. 2, with bevelled edges 4, 5 seated against an offset 3 in the middle of the strip Alternatively the tube may be rolled from two strips to form an inner ply 10, Fig. 3, of coppernickel alloy with a butt seam 11 and an outer ply 12 of a ferrous metal preferably having a scarfed seam 13.