Arc welding and additive manufacturing are hugely important for creating large metal components relatively inexpensively and quickly. New research by a team at the University of Leicester, Delft University of Technology, Diamond Light Source, University College Dublin, and TATA Steel Research UK has shown how to optimize this process to improve efficiency and cost. A paper detailing the findings was recently published in Nature Communications. The research explores the internal flow behavior in additive manufacturing of metals and arc welding — the most widely used welding process in modern manufacturing. It focused on examining the melt pools that are created during the welding process.
To do so, the team inserted small tungsten and tantalum particles into the melt pool. Due to their high melting points, the particles remained solid in the melt pool long enough for them to be tracked using intense beams of x-rays. These x-rays were generated using the synchrotron particle accelerator at Diamond Light Source, which is the UK’s national facility for synchrotron light. Beamline I12 was selected for this research due to its specialized high-energy, high-speed imaging capability at thousands of frames per second.
Using Beamline I12, the researchers were able to create high-speed movies showing how surface tension affects the shape of the welding melt pool and its associated speed and patterns of flow. The results showed, for the first time, that the melt flow behavior is similar to that previously only seen via computer simulations.
Anton Kidess, a PhD student at Delft University of Technology, developed new particle tracking algorithms that allowed for the visualization of the reported flow patterns in the weld pools. Together with Delft professors Ian Richardson and Chris Kleijn, he provided the theoretical explanations for and interpretations of the impact of trace chemical components on surface tension variations in the weld pool, which were shown to radically influence the flow patterns.
The results reveal that arc welding can be optimized by controlling the flow of the melt pool and changing the associated active elements on the surface.
“Understanding what happens to the liquid in melt pools during welding and metal-based additive manufacturing remains a challenge,” says Professor Hongbiao Dong from the University of Leicester. The findings will help us design and optimize the welding and additive manufacturing processes to make components with improved properties at a reduced cost. “Welding is the most economical and effective way to join metals permanently and is a vital component of our manufacturing economy.”
It is estimated that more than 50 percent of global domestic and engineering products contain welded joints. In Europe, the welding industry has traditionally supported a diverse set of companies. Revenue from welding equipment and consumable markets reached €3.5 billion ($4 billion) in Europe in 2017.
The results will help with the future designing and optimization of the welding and additive manufacturing process.
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