PURPOSE: To simply and easily produce a desired vacuum heat-insulated double pipe by subjecting the pipe to a vacuum heating treatment in a vacuum heating furnace so that solder is melted and penetrated to the soldering surfaces under vacuum evacuation and degassing by heating from the material surface in the pipe.
CONSTITUTION: A base end fitting 4 is preliminarily welded at the ends of an outside pipe 2 and an inside pipe 3. On the other hand, the joint part between a terminal fitting 5 and the outside pipe 2' and the joint part between a step fitting 6 and outside pipes 2, 2' are welded as well. Plural annular grooves 5a are formed at about 5mm intervals to the inside circumferential surface to be used as the brazing surface for the fitting 5 and the inside pipe 3. The solder is placed to the grooves 5a. The spacing of the outside circumferential surface of the fitting 5 to be used as the brazing surface of the fitting 5 is set at 0.25W0.35mm. The double pipe is thereafter laid horizontally in the vacuum heating furnace and is subjected to the vacuum heating to penetrate the solder to the brazing surfaces.
SUZUKI TSUNEO
WAKE HIDEYUKI
SAWADA ISAMU
Next Patent: HEAT TRANSMISSION BINDING METHOD BETWEEN HEAT TRANSMISSION MEMBERS