Abstract
Undercutting restricts the upper limit of welding speed in submerged arc welding. However, the process of undercutting has been incompletely known because of the difficulty in process observation. Accordingly, a X-ray observing apparatus and a decantation techniuqe were applied to quantitative investigation of the process of undercutting. This investigation aimed to understand dominant controlling factors for the occurrence of undercutting.
The results were as follows;
(1) Two variables mainly affect the occurrence of undercutting One is a displacement of molten metal (Xm) and the other is a solidification point along a toe of weld pool (Xs). When the molten metal is displaced more than the solidification point (Xm>Xs), the undercutting occurs.
(2) A distribution of arc heat source mainly influences the solidification point. The distribution in crossing to welding direction gives the worst influence.
(3) It seems that the dynamic component of arc pressure gives motivating force for molten metal to displace, and that the static component affects little.
