Carbothermal reduction of mill scales formed on steel billets during continuous casting

S. M.Espinoza Suarez, L. E. Borja-Castro, M. I. Valerio-Cuadros, A. Bustamante Domínguez, H. A. Cabrera-Tinoco, E. Huaman, R. A. Valencia-Bedregal, Xiaoli Zhao, Youyun Zhang, Deliang Zhang, C. H.W. Barnes, L. De Los Santos Valladares

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6 Scopus citations


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.

Original languageEnglish (US)
Article number29
JournalHyperfine Interactions
Issue number1
StatePublished - Dec 2021
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the Incorporación de Investigadores Program from the CONCYTEC – FONDECYT- UNMSM (Contract No. 12 -2019 – FONDECYT – BM – INC. INV.).

Publisher Copyright:
© 2021, The Author(s).


  • Carbothermal reduction
  • Continuous casting process
  • Mill scales
  • Mossbauer spectroscopy
  • Steel billets
  • Steel industry
  • X-ray diffraction


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