Interpretation and metallurgical modeling of hot ductility curve for solidification cracking

The aim of this study is to discuss and model the hot ductility curve during solidification in the welding from the metallurgical point of view. The contents in this study are as follows. The transverse Varestraint test was conducted to evaluate the solidification cracking, then the in-situ observation was applied on the Varestraint test in order to obtain the critical strain of solidification cracking occurrence. In addition, the U-type hot cracking test was also carried out for obtaining the critical strain, and the both critical strains were compared. Moreover, the numerical modeling was also performed in order to quantitatively explain the tendency of the relationships between the temperature and the strain. The solidification starting temperature at the non-equilibrium state was estimated based on the K-G-T model. The solidification segregation on the non-equilibrium solidification was calculated based on the mathematical analysis method proposed by T. Matsumiya. In addition, R-D-G model that is firstly suggested by M. Rappaz was used in order to explain the change in the strain depending on the progress in solidification. This paper finally mentioned the possibilities of the prediction of hot ductility curve by numerical simulation. © 2020 Japan Welding Society. All rights reserved.