To reduce defective welding due to solidifcation cracks and to obtain a laser beam welded tube without any roll flaws by providing a pair of left and right squeeze rolls butting to the part to be welded and a pair of left and right top pressure rolls respectively arranging at least a pair in font and back of a laser torch, positioning the middle point of the distance between both rotating axial centers in the upstream side more than the axial center of the laser torch including the axial center and pressing the part to be welded from the upper side.
After the time point passed the center of the separated distance L between the rotating axial center of a pair of upstream side top pressure rolls 5 and the rotating axial center of a pair of the downstream side top pressure rolls 5, both edge end surfaces H' are deformed in the direction approaching mutually and successively by the pressing and restraining action with the downstream side top pressure rolls 5. When two pairs of top pressure rolls 5, 5 arranged so that the middle point of the distance L between both rotating axial points is positioned in the welding point WP or the upstream side more than the weld pint and fusion welding is executed, both edge end surfaces H' are not separated each other.
MATSUHIRO KATSUYUKI
INABA HIROTSUGU
ETO SHIGEHIDE
HIKITA TOSHIHIRO