Geometry of laser spot welds from dimensionless numbers

Recent computer calculations of heat transfer and fluid flow in welding wer e intended to provide useful insight about weldment geometry for certain sp ecific welding conditions and alloys joined. However, no generally applicab le correlation for the joining of all materials under various welding condi tions was sought in previous work. To address this difficulty, computer mod els of fluid flow and heat transfer were used for the prediction of weld po ol geometry in materials with diverse properties, such as gallium, pure alu minum, aluminum alloy 5182, pure iron, steel, titanium, and sodium nitrate under various welding conditions. From the results, a generally applicable relationship was developed between Peclet (Pe) and Marangoni (Ma) numbers. For a given material, Ma and Pe increased with the increase in laser power and decrease in beam radius. For materials with high Prandtl number (Pr), s uch as sodium nitrate, the Pe and Ma were high, and heat was transported pr imarily by convection within the weld pool. The resulting welds were shallo w and wide. For low Pr number materials, like aluminum, the Pe and Ma were low in most cases, and low Pe made the weld pool deep and narrow. The cross -sectional areas of stationary and low speed welds could be correlated with welding conditions and material properties using dimensionless numbers pro posed in this article.