| 摘要 |
PURPOSE: To uniformly disperse remaining Nb cores after heat treatment so as to prevent attenuation and the like in a permanent current by altering a cross sectional area ratio according to a position of a Nb wire from the center in a secondary stack material in a bronze processing method. CONSTITUTION: A primary stack material constructed of a group of wire materials, in which plural primary stack materials are bound, and the heat treatment of the secondary stack materials is executed after a wire drawing processing so as to be turned into a Nb3 Sn superconductive wire material. In the secondary stack material, a cross sectional area ratio t(ri) of a Nb wire buried in the primary stack material separated from the center by a distance ri is constructed according to expressions I, II, III. By this constitution, a degree of dispersion of remaining Nb cores is unified, although a Sn quantity on the circumference is varied on the basis of the distance ri, and a breakage rate in a Nb3 Sn filament is suppressed low, so that deterioration in a critical current density Jc or a (n) value can be prevented. (In the expressions, r1 >r2 , an inferior out/in means an outermost/innermost side from the center. SNB(r) and SBZ(r) mean cross sectional areas of a Nb wire and a Cu-Sn group alloy part in the primary stack material positioned in the (r) position). |
