Patent GB-368605-A (GB)
Title: Welding process
IPC: B23K5/00
Filed: 1931-05-22
Abstract: 368,605. Uniting by fusion. LINDE AIR PRODUCTS CO., 30, East 42nd Street, New York, U.S.A. May 22, 1931, No. 15141. Convention date, July 3, 1930. [Class 83 (iv).] Structural members, such as plates, pipe sections, rolled or pressed shapes made of iron, low or medium carbon steel or steel of low alloy content such as silico-manganese steel or steels containing up to about 1À5 per cent of manganese, are welded by carburizing the contiguous edges of the members and applying high temperature heat, either produced other than electrically, such as by an oxyacetylene flame, or produced by a neutral oxyacetylene flame or electric arc in combination with an independent acetylene flame, so as to melt the carburized portions at a lower temperature than the melting point of the members, and uniting the carburized portions. The joint may be formed by bringing the superficially molten surfaces into direct contact or may consist of a lap joint, or a butt joint in which a V-groove of 90‹ or preferably 60‹ is filled with molten metal from a filler rod or from the walls of the groove. The carbon may be applied in the form of a paste or compound or graphite block or an oxyacetylene flame using excess acetylene may be used, which further provides a reducing atmosphere. The flame is stated to be suitable when it wets the members a short distance, e.g. ¢ " for a #" plate, in advance of the puddle, due to the absorption of carbon by the parts when heated to white heat and the consequent lowering of the melting point of the surfaces. Oxide is also removed by this wetting process. Such a flame has an intermediate feathery cone from one to three times the length of the inner cone. The proportion of oxygen to acetylene may be 97 to 100 parts by volume. Too much excess of acetylene is indicated by sparking at the puddle. The filler rod may be arranged vertically or inclined away from the flame, which may be directed, chiefly against the end of the filler rod, either horizontally or at an angle of 30‹ in a direction opposite to that of the welding movement. The flame may be moved longitudinally a short distance backwards and forwards during welding. Welding may also be effected by a number of independently adjusted heating devices. Thus the filler rod and puddle may be heated by an electric arc or oxyacetylene burner with normal supply or with moderate excess acetylene and the parts to be carburized by an oxyacetylene burner with excess acetylene or a pure acetylene burner. The work, filler rod or both may be pre-heated. In one form a multiple tip burner is used one tip using ordinary oxyacetylene or excess acetylene for melting the filler rod and the other excess acetylene. In another form heat from an excess acetylene flame may be deflected so as to impinge on the filler rod. The filler rod may contain from 0À05 to 0À5 per cent of carbon, 0À5 to 1À75 per cent of manganese, and 0À2 to 1À5 per cent of silicon. When welding #" steel plate with a single excess acetylene flame the rod may contain 0À11 to 0À2 per cent of carbon, 0À9 to 1À15 per cent of manganese, 0À32 to 0À42 per cent of silicon. With independently adjusted flames or groups of flames the rod may be of nearly pure iron or of steel containing less than 0À1 per cent of carbon. The carbon content of the joint is stated to be at least as high as that in the members to be joined. Also the structure of the base metal is stated to have been changed by heating beyond the recrystallization point to a depth not more than about ¢ or <1>/3 of the depth to which it is effected in ordinary oxyacetylene welding. Further this effect is stated to be shallower towards the bottom of the V-groove.