Advertisement

Journal of Thermal Analysis and Calorimetry

, Volume 133, Issue 1, pp 271–277 | Cite as

Study on fluoride evaporation from casting powders

  • Elena Brandaleze
  • Marcelo Valentini
  • Leandro Santini
  • Edgardo Benavidez
Article
  • 64 Downloads

Abstract

Casting powders are commonly used in continuous casting of steels. The chemical composition of these powders is based on various oxides, carbonaceous materials and fluoride compounds. The purpose of fluorite (CaF2) addition is to control viscosity, fluidity temperature and cuspidine crystallization during casting. Unfortunately, fluoride compounds are lost in the vapour phase during the casting operations, due to the high vapour pressure of these compounds. In view of the environmental problems associated with the evaporation of fluoride from the casting powders, a kinetic study on the fluoride evaporation was carried out. Three commercial casting powders with different fluoride contents (between 2.6 and 10.6 mass%) were selected in this study. Powders characterization includes the melting behaviour determined by hot stage microscopy, the physical properties such as viscosity estimated by Fact Sage 7.1 and surface tension calculated on the base of contact angle measurements. The crystallization tendency of the samples was determined by microscopy observations on samples quenched from 1300 °C. The emission study includes thermal analysis (DTA–TG) tests. The different phases present in the system were predicted through thermodynamic simulation. The gaseous species predicted were: NaF, KF, (NaF)2, NaAlF4, KAlF4 and SiF4. It was possible to establish that the fluoride gases emissions occur when the samples present liquid phases. The type of fluoride gas is determined by the chemical composition of the casting powders, while the percentage of emissions depends on both the viscosity and surface tension of liquids.

Keywords

Continuous casting Casting powders Thermal analysis Kinetics Fluorine emissions 

Notes

Acknowledgements

The authors wish to thank Universidad Tecnológica Nacional (Argentina) for the financial support provided to this project.

References

  1. 1.
    Brandaleze E, Di Gresia G, Santini L, Martín A, Benavidez E. Mould fluxes in the steel continuous casting process. In: Srinivasan M, editor. Science and technology of casting processes. Rijeka: InTech; 2012. p. 205–33.Google Scholar
  2. 2.
    Persson M, Sheetharaman S, Seetharaman S. Kinetic study of fluoride evaporation from slags. ISIJ Int. 2007;47:1711–7.CrossRefGoogle Scholar
  3. 3.
    Zhou L, Wang W, Zhou K. Viscosity and crystallization behavior of F-free mold flux for casting medium carbon steels. ISIJ Int. 2015;55:1916–24.CrossRefGoogle Scholar
  4. 4.
    Van Ende MA, Jung IH. Development of a thermodynamic database for mold flux and application to the continuous casting process. ISIJ Int. 2014;54:489–95.CrossRefGoogle Scholar
  5. 5.
    Sasaki Y, Urata H, Ishii K. Structural analysis of molten Na2O–NaF–SiO2 system by Raman spectroscopy and molecular dynamics simulation. ISIJ Int. 2003;43:1897–903.CrossRefGoogle Scholar
  6. 6.
    Tian Y, Shuguang G, Shibing S. Effect of Al2O3 on surface tension of the SiO2–Al2O3–RO–R2O glass system. Key Eng Mater. 2014;633:322–5.CrossRefGoogle Scholar
  7. 7.
    Wang L, Zhang J, Sasaki Y, Otrovski O, Zhang C. Stability of fluorine-free CaO–SiO2–Al2O3–B2O3–Na2O mold fluxes. Metall Mater Trans B. 2017;2:322–5.Google Scholar
  8. 8.
    Mills K. The estimation of slag properties. Short Course. Southern African Pyrometallurgy 2011. Department of Materials, Imperial College. 2011.Google Scholar
  9. 9.
    Yung HI. Overview of the applications of thermodynamic databases to steelmaking process. CALPHAD Comput Coupling Phase Diagr Thermochem. 2010;34:332–62.CrossRefGoogle Scholar
  10. 10.
    Bale CW, et al. FactSage thermochemical software and databases 2010–2016. CALPHAD Comput Coupling Phase Diagr Thermochem. 2016;54:35–53.CrossRefGoogle Scholar
  11. 11.
    Cardarelli F. Materials handbook. 2nd ed. Berlin: Springer; 2008. p. 1110–7.Google Scholar
  12. 12.
    Mills KC, Karagadde S, Lee PD, Yuan L, Shahbazian F. Calculation of physical properties for use in models of continuous casting process-part 1: mould slags. ISIJ Int. 2016;56:264–73.CrossRefGoogle Scholar
  13. 13.
    Saleem S, Vynnicky M, Fredriksson H. The influence of peritectic reaction/transformation on crack susceptibility in the continuous casting of steels. Metall Mater Trans B. 2017;48B:1625–35.CrossRefGoogle Scholar
  14. 14.
    Mizuno H, Esaka H, Shinozuka K, Tamura M. Analysis of the crystallization of mold flux for continuous casting of steel. ISIJ Int. 2008;48:277–85.CrossRefGoogle Scholar
  15. 15.
    Zhou L, Wang W, Wey J, Zhou K. Melting and heat transfer behavior of fluorine-free mold fluxes for casting medium carbon steels. ISIJ Int. 2015;55:821–9.CrossRefGoogle Scholar
  16. 16.
    Zhang ZT, Sridhar S, Cho JW. An investigation of the evaporation of B2O3 and Na2O in F-free mold slags. ISIJ Int. 2011;51:80–7.CrossRefGoogle Scholar
  17. 17.
    Sinouh H, Bih L, Manoun B, Lazor P. Thermal analysis and crystallization of the glasses inside the BaO–SrO–TiO2–NaPO3 system. J Therm Anal Calorim. 2017;128:883–90.CrossRefGoogle Scholar
  18. 18.
    Praveen J, Danewalia SS, Singh K. Influence of thermal stability on dielectric properties of SiO2–K2O–CaO–MgO glasses. J Therm Anal Calorim. 2017;128:745–54.CrossRefGoogle Scholar

Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2018

Authors and Affiliations

  1. 1.Department of Metallurgy and Center DEYTEMA, Facultad Regional San NicolásUniversidad Tecnológica NacionalSan NicolásArgentina

Personalised recommendations