GB1223404A - Method of joining clad material and joint - Google Patents

Abstract

1,223,404. Welding by fusion. NOOTER CORP. 20 Jan., 1969, No. 3237/69. Heading B3R. In a welded butt joint between two pieces A, B of corrosion-resistant clad material, in the fabrication of vessels, containers, shells, heads, nozzles, pipes &c., wherein each piece comprises a top layer 1 of corrosion resistant metal such as tantalum, columbium, tungsten, molybdenum, of at least 0À030 inch thickness, an intermediate layer 2 of copper of 0À050 to 0À070 inch thickness, and a base metal 3, e.g. steel, firstly, the top and intermediate layers 1, 2 and a top skimming of the base metal of each of the pieces are cut back at least 0À25 inch, as by planing, grinding or notching and peeling, to form new edges 8; secondly the base metals, after inverting, Fig. 3, are notched at 75 degrees, by flame cutting or grinding, leaving lands 10, and conventionally welded together by one or more passes 13; thirdly the space between the edges 8 is filled, as by silver filler, or, as shown, a copper strip 22 and approx. 0À125 inch wide silver fills 18, 19, the strip 22 and fills 18, 19 being smoothed flush with the topmost surfaces 4, as by grinding or wire brushing; and, finally, a strip 23, of the same material as that of the top layers and overlapping the latter at each side at least 0À25 inch, is welded at its edges 25 to the top layers. The copper intermediate layer is provided for heat dissipation to avoid destruction, during welding, of the clad material, the layer 1 and the base metal having widely differing melting points. In welding the base metals at 13, the lands 10 are positioned 3/32 to 1/8 inch apart and tacked at 6 to 12 inch intervals before making the passes 13. Undisturbed regions 21 of the base metals prevent the heat from the fills 18, 19 from damaging the weld passes 13. Prior to welding-on the strip 23, purge holes 24 are drilled through the passes 13 and the copper strip 22, and the top surfaces 4 are wire brushed and cleaned with a solvent such as alcohol. The edges 25 are then sealed with masking tape and oxidation preventing gas is fed under the strip 23 through the purge holes. The masking tape is removed just prior to welding the edges 25. The purge holes may be used to test the welds, as by soapy solution, dye penetrant, or helium, the latter being sniffed with a helium mass spectrometer. The strip 23 is preferably at least 0À60 inch thick; if thinner, the edges thereof should be turned up to form a flange for welding.