Reporter 451, 8 May 2000
Materials scientists at the University have developed a radical new method of recycling steel - offering a means of turning dumped fizzy drinks cans into a valuable industrial resource, with environmental benefits.
The method is cheaper than conventional treatments, requires no pre-sorting of scrap and may even produce a stronger material. It also offers significant benefits in reducing toxic waste outputs.
Professor Bob Cochrane and Drs Andy Watson and Animesh Jha have enlisted the technology transfer company, University of Leeds Innovations, to develop the patented process through pilot studies in collaboration with industry.
In normal steel recycling, tin and copper impurities tend to accumulate and cause defects in the finished product, unless they are removed by expensive and environmentally unfriendly chemical or electrochemical methods - currently facing global ‘green’ pressures.
The Leeds team found that the controlled addition of aluminium to the molten steel forms alloys with the tin or copper, rendering both harmless. Initial studies show that the presence of aluminium increases the hardness and mechanical strength of the steel.
Professor Cochrane, holder of the British Steel chair in metallurgy, said one obvious source for the alloying agent would be the vast numbers of aluminium cans which are currently recycled separately from steel cans.
"Why go to the trouble of separating them when they contain the very ingredient we want to add? An obvious extension of our process would be to charge mixed loads of scrap, saving on sorting costs," he said.
He suggested that countries without an indigenous steel industry would benefit if a combination of tin-plate, aluminium and domestic incinerator scrap could be used to produce a ‘master alloy’ to produce a higher-quality recycled steel.
Of the UK’s annual steel production, 18.5m tonnes, 40 percent is already recycled. But the annual global output of 793m tonnes hints at the size of the potential market.
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