Bruker Biospin Ag

René Fluekiger

Vital Abaecherli

Daniel M Eckert

A method for producing a superconductive element, in particular a multifilament wire, starting from a composite () 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&#xb0; C. and 750&#xb0; 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&#xb0; C. and 750&#xb0; C. at or above recrystallization temperature of the bronze matrix.

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&#xb0; C. and 750&#xb0; 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 a temperature treatment (='intermediate annealing'), 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 cold working preceded by an intermediate annealing between 520&#xb0; C. and 750&#xb0; C., i.e. above the normal Cu&#x2014;Sn recrystallization temperature, and by a fast cooling within less than 30 s to 100&#xb0; C. or below (='Rapid Intermediate Quenching' [RIQ]).

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Plan-les-Ouates, Switzerland

René Fluekiger