Quantitative Modeling of Motion, Temperature Gyrations, and Growth of Inclusions in the Weld Pool

摘要

The velocity and temperature fields, the shape andsize of the fusion zone, and the motion of the inclusions werecalculated through the solution of the equations of conservation ofmass, momentum and energy in three dimensions for variouswelding conditions. The loci and the temperature gyrationsexperienced by a large number of inclusions were calculatednumerically to seek a statistically meaningful residence timedistribution of the inclusions and the number and intensities of thetemperature cycles experienced by these particles. Finally, both thegrowth and dissolution of the inclusions were considered tocalculate their size distribution.The inclusions experienced considerable recirculatory motionand strong temperature gyrations along their paths in the weld pool.The temperature versus time plots for most of the inclusionparticles displayed several temperature peaks. However, aboutone-third of the particles experienced continuous cooling behavior.The average number of the temperature peaks in the time-temperature plots and the average residence time of inclusions inthe weld pool changed significantly with welding conditions. Thecomputed time-temperature-transformation diagrams of theinclusions showed that the temperature gyrations affected thegrowth rates and the size distributions of the inclusions. Goodagreement between the computed and the measured inclusion sizedistributions indicates that important aspects of weld metalstructure can be understood from the fundamentals of transportphenomena and kinetics.