2016 Volume 34 Issue 1 Pages 26-34
In this study, the effect of welding conditions on the opening and closing behavior of root gap during butt-welding was systematically investigated through the use of thermal elastic-plastic finite element analysis. The foci of welding conditions were weld heat input per unit weld length and plate thickness, welding speed, plate width and thickness ratio of weld metal to base metal. And then, parameters of dimensionless transverse temperature distribution to width and mechanical melting length behind weld heat source were derived respectively from weld thermal conduction theory for evaluating the root gap behavior during butt-welding. As the results, it has been clarified that the root gap behavior during butt-welding is dependent on the proposed two parameters in both single layer butt-welding and first layer butt-welding of thick plates. Also, the closing behavior of root gap is conceivable in the abstract when both of parameters becomes sufficiently-small, but in reality difficult to occur in single layer butt-welding because elements of weld metal remains unmelted. Meanwhile, the closing behavior of root gap becomes that much easier to occur in first layer butt-welding of thick plates because both parameters are possible to be sufficiently-small. Thus, more detailed understanding of opening and closing behavior during butt-welding, which can explain the cause of the differences in root gap behavior in previous studies, has been obtained.