| 摘要 |
PROBLEM TO BE SOLVED: To improve critical current density and productivity of a large-sized product by baking a metal base body and superconductor to be composed mainly of a Bi2Sr2CaCu2Ox superconducting phase in at least two primary and secondary stages of isothermal heat treatment, and performing cold plastic working between two stages. SOLUTION: A superconductor composed mainly of a Bi 2212 superconducting phase, and a metal base body such as silver or a silver alloy of satisfactory machinability are compounded. Primary baking temperature is 700-900 deg.C, and secondary baking is performed at 800-900 deg.C in a chemically stable range of the superconducting phase. Oxygen partial pressure in the atmosphere of primary and secondary baking is set at 0.1-10 air pressure and can be made constant. It is suitable to make both baking time 10 minutes or longer. This heat treatment facilitates attainment of temperature uniformity of a large-sized wire as compared to the method of atmospheric change of gradual cooling from a partially fused state, and the characteristics of the wire is further improved by cold plastic working. Critical current density is further improved by gradual cooling treatment at 1-10 deg.C/h after secondary baking. |
