PURPOSE: To enable the non-oxidation welding with less welding defects even the alcohol concentration being low by performing the welding by sealing the welding zone of an electric welded pipe with the deaerated water including alcohol.
CONSTITUTION: The shielding liquid 2 containing ≥1% liquid showing no oxidation even with its vaporization such as alcohol, with deaeration treatment as well is contained inside a shielding liquid tank 1. The welding is performed by locating the weld heating part 6 of an electric welded pipe therein with feeding this liquid 2 into a shield tank 7. The oxidation of the weld heating part 6 is therefore prevented with being sealed by the shielding liquid. In this case, the number of defects can be reduced to 1/3W1/4 in the past even in case of the alcohol concentration being 1% and the number of defects can be made zero almost in case of more then 10%. Consequently the cost in reduced and the risk of ignition can be reduced as well.
SUZUKI SEIJI
TAKAMURA TOSHIHIRO
