A PROCESS FOR JOINING OF TUBES OF (BI,PB) -2223 OXIDE HIGH TEMPERATURE SUPERCONDUCTORS USING MODIFIED SUPERCONDUCTING PASTE

摘要

The present invention provides a method for joining tube superconductor tubes, which are formed of (Bi, Pb) -2223 oxide superconductors. The (Bi, Pb) -2223 oxide superconductors of the superconducting tubes, which are oppositely joined to each other, are clubbed together on a common bush. A method of joining oxide superconducting tubes formed from cold isostatic pressing, which comprises a step of preparing oxide superconducting tubes having end faces to be joined, a step of polishing inner/outer surfaces of both end portions and both end faces of these tubes for exposing a fresh surface, a step of applying superconducting paste on the said polished end faces/inner surfaces, a step of clubbing these tubes together on a common bush, a step of close pressing the said coated end faces together, a step of coating the joined end portions with the superconducting paste to form a joint, a step of wrapping the said coated end portions with a perforated silver sheet followed by a step of sintering the joint portion and the tubes in air for 100 to 150 hours and at temperatures in the range from 830° C to 850°C. According to the invention, the superconducting paste is obtained by mixing (Bi, Pb) -2223 powder in lignin powder and boiled organic linseed oil. In the joint obtained according to this method, it is possible to stably carry more than 91% of the transport current of the high temperature superconducting tubes. A method of joining together oxide superconductors whereby, when joining the oxide superconductors by use of a bush made of an oxide superconducting material, the modified superconducting paste is applied in a region inner surface/outer surface, where a transmission path of electric current flowing between oxide superconductors component tubes as joined together is not obstructed by rendering at least portions of butting surfaces/tube -bush interface of the oxide superconducting tubes to be joined together into polished end faces/surfaces, thereby improving the superconductivity of the joined superconductors.