Physical-Chemical Reactions at Welding Arc/Molten Pool Interfaces: FY-1986 Annual Report

摘要

The arc heat source has been shown to have a strong influence on the characteristics of the molten weld pool and resulting weld bead morphology. The existence of nonequilibrium temperature distribution between arc species and the presence of metallic vapor in the arc plasma above the anode have been suggested to have an influence on the current distribution. These two influences have been investigated. A multi-fluid treatment of the arc to discern the impact on the anode current distribution and transport properties by nonequilibrium temperature distribution between electrons and heavy species in the welding arc suggests that nonequilibrium has a pronounced influence on the transport properties. However, the resulting anode current distribution is only slightly perturbed. Results suggest that nonequilibrium between species in the interfacial region of the arc above the anode produces only a second-order influence on the anode current distribution. The presence of small amounts (5-10%) of manganese can significantly enhance the low temperature conductivity of the plasma. This results in broadening of the anode current distribution relative to that found when only argon is present in the arc. Attemps to develop optical and laser diagnostics for the interfacial region above the anode are reported. Results suggest that laser induced fluorescence has considerable merit for determining species distributions in the arc and possibly in the interfacial region. 29 refs., 23 figs., 1 tab. (ERA citation 13:034303)