A Study on the Mechanical characteristics of Galvanized steel by using Hybrid Welding(Pulsed Nd:YAG Laser+TIG)

Abstract

Hybrid welding process has been taken a technical attraction due to its superiorities such as deep penetration, gap bridging ability, high speed, automation compared with other conventional methods. Galvanized steel is a promising material for long service life and superior corrosion resistance capability, namely, at least 3~6 times than that of Zn-coated steel. Therefore, this study has tried to prepared the hybrid welded (pulsed Nd:YAG laser+TIG)Joints of Galvanized steel as a new substitute process for conventional welding of lightweight parts. For clarifying the mechanical phenomena of thermal elasto-plastic behavior on the hybrid welded joints, we carried out two-dimensional thermal elasto-plastic analysis on them. Firstly, a two-dimensional heat conduction and thermal elasto-plastic programs were developed by an iso-parametric finite element method. Secondly, from the results analyzed by the developed programs, thermal, mechanical characteristics and their production mechanism on hybrid welded joints were clarified. Moreover, effects of the parameters of hybrid welding condition(gap between laser beam and arc, height of electrode, welding current, welding speed, etc.) on the temperature distribution, welding residual stresses and plastic strain of hybrid welded joints were evaluated. These results suggested sound hybrid welded joints of Galvanized steel would be obtained by optimizing the welding conditions, indicating that the penetration of 70~80% was reasonable compared to full penetration.