EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Welding is a permanent assembly process aiming at ensuring material continuity. However, during the solidification stage, several types of defect may develop. Hot cracking is one of the most common defects observed. The hot cracking occurs usually at the end of the solidification stage when the solid fraction is over 0.9. In this domain, the permeability decreases and the deformations in the mushy domain are no longer fed by liquid flow promoting the appearance of hot cracking.

In order to better understand hot cracking development and predict its occurrence, a thermo-mechanical simulation of gas tungsten arc welding process is achieved. In this simulation, based on a finite element resolution, the temperature field is firstly compared and validated regarding simulation and experimental results. A reliable solution of heat conservation equation is provided. In addition, the parameters associated to thermal source and heat transfer coefficients are calibrated in the same approach. Secondly, a strain-based solid mechanics criterion of hot cracking is applied to predict the occurrence of hot cracking phenomenon. This criterion named WYSO (Won-Yeo-Seol-Oh) is based on the cumulated strain in the plane perpendicular to the dendritic growth direction usually associated to the temperature gradient direction. The WYSO criterion indicates that a risk of hot cracking occurs when the cumulated strain in this perpendicular plane exceeds an estimated critical strain.

A comparison of hot cracking prediction with experimental results obtained in a test campaign on stainless steel AISI 321 is proposed, demonstrating the ability of WYSO criterion to predict the occurrence of hot cracking.