US Patent 7476280 Method for producing a superconductive element

A method for producing a superconductive element, in particular a multifilament wire, starting from a composite (1) comprising a bronze matrix containing Cu and Sn, in which at least one elongated structure containing Nb or an Nb alloy, in particular NbTa, is embedded, whereby in a first step the composite is extruded at a temperature between 300° C. and 750° C., followed by cold or hot working and annealing steps in which the composite is elongated in parallel to the elongated structure and softened by temperature treatment, followed by a stacking step, in which a multitude of elongated composites from the preceding cold or hot working steps are bundled, the steps of extruding, elongating, annealing and stacking being repeated one or more times, followed by a final elongating process, including intermediate annealing processes, in which the composite is elongated to its final length, the superconductive phase being obtained by a heat treatment including a solid state diffusion reaction is characterized in that at least part of the elongating steps and annealing steps are performed by isothermal hot rolling in a temperature region between 450° C. and 750° C. at or above recrystallization temperature of the bronze matrix.