Correlation Between Cold Cracking and Restraint Intensity in Tack Weld

Abstract

If the cold crackings occur in tack weld and remain in the weld grooves, the strength of the welded joint will decrease unexpectedly.
The initiation of this kind of weld crackings is known to be influenced by chemical composition of base plate, diffusible hydrogen concentration at the root of weld bead and the restraint intensity of weld joint. Therefore, it is very important to estimate the restraint intensity of tack weld joint from the view point of avoiding such weld crackings.
This research was performed for the purpose of studying the restraint intensity of tack wled joint and its effect on the weld crackings due to tack weld. The results are summarized as follows.
(1)The concept of the restraint intensity well predicts the condition of the crack initiation within such a small bead length that a heat source of welding can be regarded as an instantaneous one from the aspect of residual stress distribution produced in a tack weld bead.
(2)The correlation between the restraint intensity of the tack weld joint in real structures and various parameters influencing this value was obtained, and based on this relation a testing method for avoiding tack weld crackings in real structures was proposed.