サブマージアーク溶接におけるひずみ挙動

Abstract

As a basic research of strain characteristics in automatic arc welding process, which is executed in considerably higher arc current and welding speed than those of manual arc welding, the investigation has been experimentally carried out on submerged arc welding of mild steel plate under different heat inputs (Fig.1 and Table 2). Detailed observation covers the welding thermal cycles, the progress of longitudinal and transverse strains in base metal during welding and cooling as well as the distributions of the longitudinal total, elastic and plastic strains, the transverse shrinkage and the angular distortion after welding. Main results obtained are as follows.The transient mechanical strains of longitudinal and transverse directions occur respectively in tension and compression conversely to each other during the former stage of welding and, afterward, change into compression and tension according to the thermal expansion and shrinkage of the weld zone, which are inferable from the thermal cycles (Figs.3 and 8).From the distributions of longitudinal total strain and transverse shrinkage after welding, it is clear that the welded plate expands longitudinally in its middle and contracts in its outer portions, that is, the half of plate on either side of the weld line deforms into fan-shape, these rotational deformation being re-markable in case of large heat input (Figs.5 and 10). And also, the large heat input reduces the magnitudes of longitudinal plastic shrinkage occurring in the weld zone, extends transversely the region of its occurrence and consequently reduces the inherent shrinkage (Figs.11 and 12). The observed distributions of longi-tudinal residual stress and plastic strain along the transverse center line of welded plate, in case of low heat input, well agree with those theoretically derived (Tables 4 and 5).