PURPOSE: To prevent incomplete penetration and toughness deterioration by welding the position separated by specified dimensional from a center line of a root gap and then, welding a bead passing through thick plates with the position separated in the reverse direction by specified dimensions from the center line as a center in a specified time.
CONSTITUTION: A square butt groove of thick steel plates 1 is subjected to laser beam welding. A bead 4B passing through plate thickness is welded with the position separated by 0.25-1.25mm from the center line of the root gap 5 of the square groove as a center. A bead 4C passing through plate thickness with the position separated by 0.25-1.25mm in the reverse direction from the center line of the root gap 5 as a center is welded in two minutes. Consequently, when two passing through beads 4B and 4C are separated by specified dimensions, the sufficient bead width is obtained, these breads are fused into one mutually and penetration becomes satisfactory. When welding is performed in two minutes, toughness is improved by a preheating effect.
KOYAMA KUNIO
TANABE KOJI
