Surface Ripple in Electron-Beam Welding Solidification

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Abstract
The occurrence of ripples on the workpiece surface after solidification in electron-beam welding or melting is experimentally and analytically investigated. The maximum accelerating voltage and welding current of the electron-beam welder are 60 kV and 50 mA, respectively, while the workpieces are Al 1100 and SS 304. The average pitches and amplitudes of surface ripples are measured for different beam powers and welding speeds. Using a scale analysis to account for heat transfer and fluid flow induced by a negative temperature-dependent surface tension gradient in the molten pool the variations of ripples with dimensionless beam power, Marangoni, Peclet, Prandtl, Stefan, and Biot numbers are found for the first time. The predicted results show good agreement with experimental data.