Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Metallurgical Engineering

The accumulation of tramp elements (Cu, Pb, Ni, Sn and Sb) in steel as a result of excessive use of scrap will affect the mechanical properties of steel as reduction of hot ductility, failure at bending test and hot shortness of steel during casting, reheating and rolling process. A survey was done to estimate how far is the problem of residual elements appearing in Egyptian steel, and the effect of its presence on steel manufacturing and its mechanical properties including impact toughness, ductility, bendability and hot ductility. The aim of this work is to study how to avoid the hot shortness problem caused by copper, by adding nickel, silicon and nickel plus silicon to form solid solution or intermetallic compounds which have higher melting points. Studying the effect of Tempcore process on hot shortness, which prevents the diffusion of tramp elements (Cu, Pb and Sb) forming low melting point compounds at grain boundaries. Study the effect of sulphur on copper precipitation and copper hot shortness. The results showed that Tempcore process forms supersaturated solid solution of copper in ferrite and uniform fine Cu precipitates which improve the ductility. The addition of nickel, silicon and nickel plus silicon mitigates the negative effect of copper on hot ductility. Finally, the results showed that the presence of copper as a tramp element will increase the ductile brittle transition temperature

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