| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a boom capable of promoting the weight reduction and rigidity increase of the boom, and to provide a method of welding the boom reduced in the number of working steps. <P>SOLUTION: In the boom formed by welding a plurality of steel plates into a cylindrical sectional shape, abutting joined parts of respective edges of the steel plates 1, 2 are welded by hybrid welding H constituted of a welding method A using a filler material and laser beam welding R. If the abutting joined parts of the steel plates are fused by the welding method using the filler material to add a molten metal amount of the filler material to a molten metal amount of a base metal and then heated by the laser beam welding, the molten metal may penetrate in a depth direction of the abutting joined parts and thereby even the abutting joined parts having large joint gaps can be surely joined by welding. In addition, since the laser beam welding method has small amount of a heat input, torsion and strain hardly occur in the boom after welded. Thus, since a dimensional difference among respective stages of the booms in the multistage nested boom is reduced, the sectional size of the boom on the leading end side can be increased to increase rigidity. <P>COPYRIGHT: (C)2013,JPO&INPIT |
