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Scientists finally managed to observe solidification cracking in real time

Posted February 1, 2017

Welding is incredibly important for many industries around the world. It is a strong, durable and relatively easy way of joining two metal parts together. However, welding is a demanding skill or result of complex programming of manufacturing robots. There is one problem – solidification cracking occurs quite frequently and only now scientists from the University of Leicester can explain why.

Welding is the best way to connect two metal elements, but it has one common drawback – solidification cracking. Image credit: U.S. Department of Defense via Wikimedia, Public Domain

Solidification cracking is a welding defect, which occurs when a weld cools down. Metals shrink when their temperature drops and so welders have to be aware of that. However, solidification cracking happens anyway and usually right in the middle of the weld metal, making it structurally weak. Furthermore, this defect usually occurs in steal, which is extremely important alloy for industries around the world. In fact, most of the cars, especially their safety structure, are built from this alloy, which means that solidification cracking can cause major problems in their longevity and reliability. Steal is also very important in construction and welding is pretty much unavoidable when working with steal parts.

3D ex situ reconstruction and characterisation of weld solidification. Image credit: University of Leicester

Therefore, solving the problem of solidification cracking is very important, but impossible without understanding how it happens. Scientists managed to take a better look at the mechanism behind this issue and noticed that a crack develops by linking micro-porosities in the meshing zone in the solidifying weld pool. It is said that scientists managed to observe solidification cracking in such detail for the first time and they managed to achieve that only by using complex advanced technology. Synchrotron X-ray beamline at the European Synchrotron Radiation Facility was used and it allowed scientists to see the crack developing in real time, which is what led to the results of this study.

Welding really is the most important method of creating strong structures from metal. One might think that in the new era of composite plastics it is going to lose its positions and will become redundant. However, it is still very important and is likely to be in the foreseeable future. Hong Dong, lead author of the study, said: “Solidification/hot cracking is the most common failure mode during metal processing, such as welding, casting and metal additive manufacturing (metal 3D printing)”.

Now that scientists know how it occurs they can try coming up with ways to avoid it. It would benefit such sectors as shipbuilding, pipeline, automotive, aerospace, defence and construction, which means goal of crack-free welds is really worth pursuing.


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