A billet is a bar made from crude steel which surface contains scales which are rich in iron oxides. This study presents the carbothermal reduction of the scales formed in steel billets. The process included the reaction of the iron oxides contents with carbon (in ratio 5:1) and annealing in a tubular furnace under argon atmosphere. The occurred reactions are discussed using thermodynamic calculations and thermal analysis which indicate a three-stage reduction process Fe3O4 ➔ FeO ➔ Fe3C ➔α-Fe with intermediate reactions at the interval temperature 960 and 1300 °C. The X-ray diffraction confirms the reduction to α-Fe with minor presence of unreacted C, magnetite and wustite. Mössbauer spectroscopy analysis was performed at room temperature where a typical sextet corresponding to the dominant α-Fe is shown as well as wustite, magnetite and cementite to a lesser extent. The magnetization measurements confirm the ferromagnetic state corresponding to the α-Fe.

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In the last decades, the demand for steel has increased exponentially generating tons of waste impacting the environment. The most common waste in steelmaking process are slags which are produced during the rolling process of steel billets. This situation has encouraged the scientific community in finding environmentally possible ways to take advantage of this slags. In this work, we present the structural and magnetic properties of solid state recycled Q235 steel chips obtained by powder metallurgy and extrusion process from oxide scales of billets. The characterization of the recycled Q235 chips was performed by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. The X-ray diffraction reveals α-Fe as the predominant crystallographic phase and non-stoichiometric wüstite in minor amount. The Mössbauer spectrum revealed a sextet associated to α-Fe phase with a hyperfine magnetic field B hf ~ 33 T and two doublets associated with Fe 2+ and Fe 3+ from the non-stoichiometric wüstite. Magnetic measurements show a ferromagnetic behavior because the presence of α-Fe which is the predominant phase and hysteresis is also observed under low applied fields.