Abstract
Nb-Zr alloys containing 25, 50 and 70 at%Zr were fabricated into long fine wires. The most suitable lubrication for the drawing was coating of the wires with a layer of graphite or MoS2. The layer was formed by smearing colloidal solutions of these lubricants and subsequent drying up at 120°∼150°C in hot blasts. The friction coefficients between the wires and the WC drawing dies were measured by the separate die method. The friction coefficients during the continuous drawing were 0.07∼0.08 for graphite coating and 0.05 for the additional coating of MoS2. These values were a few tens of percent larger than those measured by the reciprocal friction testing machine. The die angle which minimized the drawing force was between 18° and 20°. The drawing forces which were calculated by formula (3) of this paper were in good agreement with the observed values. The influences of the intermediate annealing temperatures and the reduction of drawing upon mechanical and superconducting properties of the wires were also investigated. The wire annealed between 700°C and 850°C and then drawn about 96% showed the highest superconducting current capacity.
