LASER BEAM WELDING METHOD FOR THIN PLATE

PROBLEM TO BE SOLVED: To simply execute the laser beam welding of an overlapped portion of two thin plates having a space, in particular, a small and irregular space without generating any burn-through. SOLUTION: The laser beam welding is executed twice, including a first laser beam welding in which laser beam is applied in a defocus state with the focal point not being on, an upper plate on the laser beam application side is melted at a part having a space, and recessed to a lower plate side to reduce the space, and at a part without any space, the upper plate and the lower plate are joined with each other so that the melting is not penetrated to the back side of the lower plate for the first time, and a second laser beam welding in which the melting is penetrated to the back side of the lower plate for the second time. COPYRIGHT: (C)2010,JPO&INPIT