Estimation of Critical Strain Caused by Solidification Shrinkage during Weld Solidification

MPF (Multi-Phase Field) method was applied for the microstructure formation process of Fe-18%Cr-15%Ni-0.05%C alloy during weld solidification and critical strain rate due to solidification shrinkage in the mushy zone was calculated by RDG (Rappaz-Drezet-Gremaud) model. Estimated critical strain for the solidification cracking was corresponding to the experimental result of trans-varestraint test by adjusting the dendrite coalescence temperature and the vulnerable time. Initiation of solidification cracking was thought to be occurred near the solidification front, about one third of solidification temperature range. This result is corresponding to the previous work of in-situ observation. It is considered that the solidification shrinkage plays an important role for the appearance of solidification cracking. Further understanding of the metallurgical phenomenon in the initiation of welding solidification cracking could be obtained by the quantification of solid connection between dendrites at the vulnerable region.