The technology of thermal welding of the circulation piping of NPPS containing the influence of ultrasound

The role of individual factors of ultrasonic field in creating certain structural changes in the metal depends on the crystallization conditions. In different areas of the crystallizing melt, the effect of any of the ultrasonic field factors may dominate. For example, the dispersion of crystals may occur in the two-phase zone, and the acoustic streams and stirring may be only in the liquid phase. If the reduction of grain size and elimination of the columnar structure are due to the ultrasonic dispersion, the change in phase distribution and the dendritic process of elimination are mainly determined by changes in the temperature gradient in the melt and stirring. The reasons for dispersion are cavitation, viscous friction forces, oscillatory and radiation pressure. An increase in the rate of nucleation of crystallization centers is also associated with these parameters.