| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a boom having small twist or deformation in a tube body, and to provide a boom welding method wherein generation of the deformation is small. <P>SOLUTION: In this boom, a plurality of steel plates 1, 2 are welded to form a cross-sectionally tubular tube body, and reinforcing plates 3-6 are installed onto the surface of the tube body. Junction portions between the tube body and the reinforcing plates are welded by hybrid welding H comprising arc welding a1 and laser welding R. The junction part between the tube body and the reinforcing plate is molten by the arc welding a1, a molten metal amount of a filler material is added to a molten metal amount of a base material, and next, when performing heating by the laser welding R, the molten metal is molten in the depth direction of the junction part, so that the reinforcing plate can be certainly joined by the welding. Furthermore, because the laser welding R has small heat input, the twist or the deformation is hardly generated in the boom after the welding. Accordingly, because a size difference between multistage booms in a multistage nesting type boom can be reduced, a sectional size of the boom on the tip side is increased to improve rigidity. <P>COPYRIGHT: (C)2013,JPO&INPIT |
