The research, which was a collaboration between the University of Leicester, Delft University of Technology, Diamond Light Source, University College Dublin and TATA Steel Research UK was recently published in the journal Nature Communications.
The research explores the internal flow behaviour in additive manufacturing of metals and arc welding, focusing on the melt pools that are created during both processes. To do this, 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 X-ray beams.
The X-rays were generated using the synchrotron particle accelerator at Diamond Light Source, the UK’s National facility for synchrotron light. The team selected Beamline I12 for this research due to its specialised 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.
The results revealed 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,” said Professor Hongbiao Dong, who led the research. “The findings will help us design and optimise 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.”
According to the University of Leicester, more than half of global domestic and engineering products contain welded joints, with revenue from welding equipment and consumable markets reached €3.5 billion in Europe in 2017.
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