| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent opening defect of a penetration bead and blowhole of a weld zone without shielding a back surface of a base metal with inert gas by controlling the laser power piercing the base metal of the laser welding to form the penetration with a single pass to less than a certain value. SOLUTION: On a surface side of a base metal 4 to be welded, a shield nozzle 2 is arranged which sprays the shield gas coaxially with a laser beam 1, whose focus is set at the surface of the base metal 4, and controls the atmosphere on the surface side of the weld zone by means of a gas flow 3. When the back side of the weld zone is not shielded with the inert gas or the welding is done while stopping the plasma removing gas flow 8 against a side gas nozzle 9, the opening defect does not occur and the blowhole rarely occurs if the signal pass piercing welding is done under such condition that the laser power Pt (kW) after the base metal is pierced will be Pt<3.0, regardless of the output of the laser beam 1 and welding speed.</p> |
