Eliminating a Major Cause of Wire Drawing Breakage in A-15 High-Field Superconductors

70101 The production of high performance A-15 superconductors (niobium-aluminum and niobium-tin), in kilometer lengths with 0.6 to 0.8 mm diameter wire, suffers from frequent wire drawing breakage of the superconductor precursor composite wire, resulting in very low product yields. The breakage, which initially develops below 1.5 mm diameter, is usually caused by non-uniform deformation in the drawing die due to wire misalignment at the die entrance. In turn, this misalignment results from the high bend flexibility of the small wire, coupled with a slight asymmetry of the composite structure. This project will develop a novel apparatus that employs high hydrostatic fluid pressure on the wire to hold it straight as it is guided into the die. In Phase I, at least three different A-15 composite wire designs will be evaluated with the new apparatus. Tests will be conducted without alignment guidance and with relatively short lengths (30 to 50 meters) of Nb-Al and Nb-Sn composite wires. Maximum misalignment limits of 0.75 degrees, using a short span mechanical guide, and 0.35 degrees, using the ¿hydrostatic pressure stiffening¿ concept in a long span guide, are expected. Commercial Applications and Other Benefits as described by the awardee: The new alignment method should enable the fabrication of optimum performance superconductors with high manufacturing yields, leading to lower wire costs in such applications as high energy physics, fusion energy, and magnetic resonance imaging units.