| 摘要 |
PURPOSE:To perform a laser beam machining without having the adverse effect due to the plasma generation by scanning a laser beam by reducing the output of a laser machining part, removing the plasma generating substance on the surface with its burning and scanning it by increasing the output by the same laser beam. CONSTITUTION:A laser beam head 4 is set at the upper part of the weld zone 3 where the respective end part 1a, 2a of zinc plated steel plates, 1, 2 are overlapped and the scanning by a layer light of lower output than an ordinary laser beam machining time is performed. In this stage the zinc plating on the surface of the zinc plated steel plate 1 is removed with its burning and the plating removed part 3' exposing the steel plate of the base metal is formed on the weld zone 3. The scanning by the laser light of higher output than that at the pre-machining stage is performed by the same laser beam head 4 for the plating removed part 3' formed by the pre-machining treatment. The plasma generation by the laser light projection is thus restrained remarkably and a sure and good welding is obtd. |
