Visualization and Optimization of Shielding Gas Flows in Arc Welding
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GMA welding is one of the most frequently applied welding techniques in industry. Particularly the joining of aluminium, high alloyed steels or titanium requires a cover of shielding gas in order to provide a low PPM concentration of oxygen. The result of the welding process depends essentially on the chemical and thermophysical properties of the process gas used. Consequently, it is necessary to be able to describe and to analyse its flow with respect to various influencing variables. However, it is very difficult to realize this during arc welding processes; a poor access is predominant due to the covered areas inside the welding torch and temperatures of up to 20 000 K cause the strong radiation of the arc and electromagnetic fields. This paper deals with experimental and numerical methods for visualization and quantification of process gas flows in arc welding and gives examples for their technical applications. Unlike previous work, the described methods consider the arc as a dynamic element which determinates the gas flow. Advanced Particle Image Velocimetry (PIV) and Schlieren measurement were used for characterization of the flow field in the direct vicinity of the arc in GTA and GMA welding. Furthermore, a numerical model including magneto-hydrodynamics and turbulence models was used for a detailed visualization of the flow in the free jet and in the hidden interior of the torch. It is based on a commercial CFD code which allows to model complex 3-D geometries of torch and workpiece design. Mixing effects and turbulence model were validated by oxygen measurements in the gas shield.
IIW-Thesaurus keywordsArc Physics Arc Welding Electric arcs Flow GMA welding GMMA welding GTA welding Impurities MAG welding Measurement Measuring instruments MIG welding Outdoor environment Oxides Oxygen Photography Research and development Shielding gases Simulating Torches
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