Modeling of inclusion growth and dissolution in the weld pool

The composition, size distribution, and number density-of oxide inclusions in weld metal are critical factors in determining weldment properties. A co mputational model has been developed to understand these factors, consideri ng fluid flow and the temperature field in the weld pool during submerged a re (SA) welding of low-alloy steels. The equations of conservation of mass, momentum, and energy are solved in three dimensions to calculate the veloc ity and temperature fields in the weld pool. The loci and corresponding the rmal cycles of thousands of pride inclusions are numerically calculated in the weld pool. The inclusions undergo considerable recirculatory motion and experience strong temperature gyrations. The temperature-time history and the computed time-temperature-transformation (TTT) behavior of inclusions w ere then used to understand the growth and dissolution of oxide inclusions in the weld pool. The statistically meaningful characteristics of inclusion behavior in the weld pool, such as the residence time, number of temperatu re peaks, etc., were calculated for several thousand inclusions. The calcul ated trends agree with experimental observations and indicate that the incl usion formation can be described by combining thermodynamics and kinetics w ith the fundamentals of transport phenomena.