Approaches to increase process efficiency in laser micro welding

In this paper, the influence of focal diameter, feeding rate and thermo-mechanical characteristics of the applied material, represented by its thermal diffusivity, on process efficiency in laser micro welding will be investigated. They all influence the Peclet number which is a significant determinant of heat conduction losses during laser welding. Two different single-mode lasers with high (1,000 W) and low power (40 W) were used with ultra-thin stainless steel foils in thicknesses from 15 to 50 mu m as well as aluminum foils in a thickness of 40 mu m. They were welded in an overlap joint. It could be clarified that different dependencies of heat conduction loss have to be considered related to the Peclet number. Additionally, the choice of the material with its thermo-mechanical characteristics has a great effect on the way in which thermal efficiency can be increased. Furthermore, process efficiency in micro welding is influenced by varying focal diameters. (C) 2013 The Authors. Published by Elsevier B. V. Selection and/or peer review under responsibility of the German Scientific Laser Society (WLT e.V.)