Influence of the Weld Pool Geometry on Solidification Crack Formation

Abstract

Numerous externally loaded as well as self-restraint hot cracking test procedures have been developed over the years to evaluate soldidification crack phenomena. But the interpretation and the subsequent transfer of test results towards component weldments has still to be regarded as a decisive challenge. Some progress has been achieved by hypothesizing crack / no crack criteria referring to uniform and uniaxial loading of the solidification front during welding. But, as the present results show, solidification cracking significantly depends on the geometry of the solidification front, which has so far not been considered in the respective criteria. In this contribution, the position of solidification cracks is correlated with the positiondependent strain rates along the solidification front and with the positiondependent curvature of the weld pool. Especially at positions of high curvature, an increased rate of shrinkage can be predicted on the basis of a geometrical Rate of Feeding (ROF) Rate of Shrinkage (ROS) model, corresponding to the measured positions of the solidification cracks. The assumption of position-dependent strain and strain rates along the solidification front during Varestraint-Testing has been confirmed by means of numerical simulations.