- University of Sheffield engineers have developed a new way of making lightweight, high strength steel that can be easily adapted to mass manufacturing
- New way of making steel could help car manufacturers who are looking to use lightweight, high strength steel to make their vehicles lighter and more sustainable
- Sheffield method uses copper - an element previously cast aside by the steel industry because of the detrimental effects it can have on certain types of steel
A new breakthrough in steel manufacturing that could also help to lower CO₂ emissions from the car industry, has been made by engineers at the University of Sheffield.
In the study, published in the journal Nature, a team led by Professor Mark Rainforth and Dr Junheng Gao from the University’s Department of Materials Science and Engineering has developed a completely new way of making lightweight, high strength steel that can be easily adapted for mass manufacturing.
The team’s research has shown how ultra-fine grained steel can be made to deliver world leading mechanical properties. The technique can produce steel with a strength of nearly 2GPa - for example a 1cm diameter wire capable of holding a weight of 15 tonnes. It can also produce steel with an elongation of 45 per cent - this means the steel would be ductile enough to be able to be formed into complex shapes.
The secret behind this success is the inclusion of copper - an element which is traditionally avoided in steel production because of the detrimental effects it can have on the properties of particular types of steel.
Copper is increasingly being found in recycled steels because much of it is made using recycled cars and other engineered items that contain electrical wiring. With steelmakers looking to use more recycled materials in their production process to become more sustainable, copper is now being seen as unavoidable by the industry.
To overcome the issue, the Sheffield team has developed a new way to use copper in the manufacturing process to produce a world leading quality of steel. To do this, they needed to understand how the copper atoms distribute themselves within the steel matrix.
Advanced imaging by co-authors at the U.S. National Institute of Standards and Technology (NIST) showed that when the steel is heat treated during processing, the copper precipitates rapidly within the crystal grains of steel, rather than at the grain boundaries. This restricts the growth of grains in the material’s microstructure, leaving an ultrafine-grained microstructure which imparts the high strength and superior ductility, but also enhances its thermal stability.
The combination of these properties makes this steel particularly appealing to automotive manufacturers, as they are looking to include lightweight components to make their vehicles more sustainable.
The average car contains 900kg of steel, so any way of reducing this will improve the performance of the vehicle in terms of its environmental impact.
The benefit of using high strength steels is that less material can be used in the vehicle, and so the total weight of components is reduced for the same level of performance.
Professor Mark Rainforth, Professor of Materials Science and Engineering at the University of Sheffield, said: “Copper is typically seen as an element to avoid by steelmakers as it can have a negative impact on certain types of steel. However, what we’ve managed to do here at Sheffield is develop a completely new technique that is able to harness copper in a positive way in order to produce a truly world leading quality of steel. This steel is high strength and incredibly lightweight, meaning it can be used to manufacture vehicles that are better for the environment.”
The research paper, Facile route to bulk ultrafine-grain steels for high strength and ductility, is published in Nature. To access the paper, visit: https://www-nature-com.sheffield.idm.oclc.org/articles/s41586-021-03246-3
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