In a new study published in the journal ‘Scientific Reports’, the project team from the UK’s University of Leicester Department of Engineering, has proposed that solidification cracks grow by linking micro-porosities in the meshing zone in the solidifying weld pool. Importantly, this is the first time that researchers have observed solidification cracking in steel and sheds new light on why the alloy may crack during the process.
‘Welding is the most economical and effective way to join metals permanently and it is a vital component of our manufacturing economy,’ commented Professor Hong Dong from Leicester and one of the authors of the study. ‘It is estimated that more than 50 % of global domestic and engineering products contain welded joints. In Europe, the welding industry has traditionally supported a diverse set of companies across the shipbuilding, pipeline, automotive, aerospace, defence and construction sectors. Solidification/hot cracking is the most common failure mode during metal processing, such as welding, casting and metal additive manufacturing (metal 3D printing).’
The team obtained their results by using synchrotron X-ray beamline at the European Synchrotron Radiation Facility (ESRF) for three days in Grenoble, France, to observe the crack formation in real time. Through the modern advances in synchrotron X-ray and imaging techniques, the team was also able to see through metals, providing detailed analysis of the alloy. During the experiments, a total of twenty seven samples were tested, taken from three steel variants and tested at three different strain rates. Each test was then repeated three times to demonstrate repeatability between tests.
Although no official data exists on the revenue of the EU welding industry due to the diverse applications of the welds, it is estimated that over 50 % of global domestic and engineering products contain welded joints, and welding equipment and consumable markets reached EUR 3.5 billion in Europe in 2007. Alongside the industrial importance of the sector, weaknesses in welded parts can have disastrous effects, including putting lives at risk, as well as serious economic repercussions due to damages and insurance payouts for faulty products. They can also cause environmental catastrophes such as pollution if imperfectly welded parts are used in environmentally-sensitive areas, such as the ocean.
The MINTWELD project officially ended in August 2013 and pioneered new ways of making welding simpler, safer and more economical by using new technologies and state-of-the-art computer modelling techniques. The results of this latest study mark another important contribution to the team’s innovative solutions to increase the overall efficiency of steel welding and open up new markets for the European steel welding industry.