GB1190638A - Manufacture of Composite Metal Products. - Google Patents

Abstract

1,190,638. Making composite plates; welding by fusion. RICHARD THOMAS & BALDWINS Ltd., and INTERNATIONAL COMBUSTION (HOLDINGS) Ltd. 11 Dec., 1968 [28 Sept., 1967], No. 44290/67. Headings B3A and B3R. In producing a corrosion-resistant stainless steel clad mild steel sheet or strip, for large containers or refrigerator body linings, one or more surfaces of a cleaned (e.g. ground or grit blasted) and flat (e.g. milled or ground) billet, slab or plate of mild steel of 0À1% max. carbon is overlaid, by deposition by fusion welding, with austenitic or ferritic stainless steel of 0À08% max. carbon, the fusion welding being so effected and controlled that the dilution, by the mild steel, of the deposited stainless steel (or the first layer thereof if deposited in several layers) does not exceed 15%, and preferably 10%; after removal of welding flux and, e.g. by grinding, surface protuberances, the overlaid billet is soaked and hot-rolled (the temperature not falling below 900‹ C.) to composite sheet or strip; and the latter is descaled, e.g. by pickling, cold-rolled to desired thickness and then annealed at, say, 1080‹ C. for 1 to 10 minutes. Anti-scale paint may be applied before annealing. The rolling and annealing conditions are those appropriate to the stainless steel. The low carbon content of the stainless and mild steels and the stainless steel dilution limit prevents the carbon content of interface martensite from exceeding 0À15% and, hence, the bond from disrupting during working. The dilution limit also guards against the possibility of composition change in the stainless steel extending to its surface after rolling. The extent of the dilution is dependent upon control of welding voltage and speed. The welding may be carried out by M.I.G., T.I.G., manual arc, hot-wire plasma, or wire- or, as preferred, strip-electrode submerged-arc process. Successive weld beads are applied sideby-side over the base length. The weld bead should be flat-topped and 45-degree edged, and re-entrant edges allowing slag trapping and excessive bead overlap should be avoided. To achieve cladding of a given specification, the stainless steel being deposited (at least in the first layer where several layers applied) should be richer in alloy elements, e.g. chromium, and/or chromium may be added to the flux. In an example, by using an austenitic stainless steel containing 22% Cr, 11% Ni, 0À04% C, with a flux containing 1À5% Cr, the cladding produced contained 19À5% Cr, 10À25% Ni. Other stainless steel claddings include those containing Mo and those stabilized by Nb. The Specification includes examples of arc voltage, current, strip electrode size, welding speed, layer and slab thickness, and soaking and rolling and annealing temperatures.