Sources and Effects of Growth Rate Fluctuations in Ripples formation during Weld Metal Solidification

This paper is primarily concerned with isolating factors responsible for and influence on growth rate flucturations inherent in weld metal solidification. These factors&their interactions are discussed with respect to their role(s) in producing micro-structural features such as "traverse solutebanding" and "porosity banding" and the formation of weld surface ripples. Growth rate fluctuations are attributed to the cyclic variation in the thickness of the solid-liquid transition region (the diffuse interface).

A simple heat flow analysis of the effect of a varying thickness interface on heat transfer is discussed. A mechanism for weld surface ripple formation is proposed based on the interaction of growth rate fluctuations and surface tension effects of the weld pool surface. The variations in ripples developed under steady state (during welding) and terminal (arc and spot welds) conditions of slidifactions are discussed.