QUANTITATIVE MODELING OF MOTION, TEMPERATURE GYRATIONS, AND GROWTH OFINCLUSIONS IN WELD POOL

The velocity and temperature fields, the shape and size of the fusion zone, and the motion of the inclusions were calculated by the solution of equations of conservation of mass, momentum, and energy in three d imensions for various welding conditions. The loci and the temperature gyrations experienced by a large number of inclusions were calculated numerically to seek a statistically meaningful residence time distrib ution of the inclusion and the number of intensities of the temperatur e cycles experienced by these particles. Finally, both the growth and dissolution of the inclusions were considered to calculate their size distribution. The inclusions experienced considerable recirculatory mo tion and strong temperature gyrations along their paths in the weld po ol. The temperature-time plots for most of the inclusion particles dis played several temperature peaks. However, about one-third of the part icles experienced continuous cooling behaviour. The average number of the temperature peaks in the time-temperature plots and the average re sidence time of inclusions in the weld pool changed significantly with welding conditions. The calculated temperature-time-transformation di agrams of the inclusions showed that the temperature gyrations affecte d the growth rates and the size distributions of the inclusions. Good agreement between the calculated and measured inclusion size distribut ions indicates that important aspects of weld metal structure can be u nderstood from the fundamentals of transport phenomena and kinetics.