抄録
Undercut restricts the upper limit of welding speed in submerged arc welding (SAW). The mechanism of formation of undercut has been, however, incompletely known because of the difficulty in process observation. Accordingly, in the present study, a direct observation of the process by X-ray and simulations of the weld puddle phenomena by a heat conduction model and an arc pressure measurement were undertaken. This study aimed to understand the dominant controlling factors of undercut and to develop a new technique for high speed welding.
A quantitative investigation of the process of undercut which restricts the upper limit of welding speed in submerged arc welding was undertaken in an attempt to gain a clear understanding of the dominant factors of this defect and to develop a high speed welding technique.
Two variables mainly affect the occurrence of undercut. One is the displacement of molten metal (Xm) and the other is the solidification point along a weld puddle toe (Xs). When the molten metal is displaced more than the solidification point (Xm>Xs ), undercut occurs.
As a result of these effects, the linearization of an arc heat source by a group of fine electrodes allows a much higher critical travel speed than the conventional arc heat source.
