Abstract
This work aimed to assess the possibility of stabilising argon oxygen decarburisation (AOD) stainless steel slag with CaO/SiO2 ~ 1.6, by using a secondary alumina by-product (~75 wt% Al2O3, referred herein as SA, found under the name “Valoxy®”) and reduced levels of B2O3. Two groups of samples were synthesised: one reference group with AOD slag and 0.26, 0.16, 0.10 and 0.05 wt% of B2O3 and one with equivalent compositions but to which 5 wt% of SA is added. Experimentally, the slags were produced in a platinum crucible in a resistance furnace, heated with 5 °C/min until 1,640 °C, equilibrated for 1 h, followed by slow cooling to room temperature. The mineralogical composition was analysed by QXRD whereas the micro-hardness was measured through a Vickers indentation test. The microchemistry and morphology were analysed by EPMA–WDS. Analysis indicated that AOD was successfully stabilised by 5 wt% SA and 0.10 wt% B2O3, whereas for 0.05 wt% B2O3, volumetric expansion occurred over time. In terms of mineralogy, the use of SA promoted the formation of spinel instead of gehlenite. Electron microscopy revealed a more dense morphology in the samples with SA when compared to the reference ones. Elemental maps indicated that Cr predominantly participates in the spinel phase. Vickers tests showed a slight increase in hardness in the samples with SA. In conclusion, the addition of SA resulted in substantially different microstructures that appear to be promising in terms of chemical and mechanical stability. However, in terms of volumes the required addition levels for effective stabilisation are substantial compared to B2O3 additions.
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Acknowledgments
The financial support of RVA, France is gratefully acknowledged as well as the active involvement of Mr. H. Epstein. The thermodynamic calculations were performed by E. Nagels, InsPyro NV. The EPMA–WDS work has been feasible due to the support of the Hercules Foundation (Project ZW09-09). Yiannis Pontikes is thankful to the Research Foundation-Flanders for the post-doctoral fellowship.
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Iacobescu, R.I., Malfliet, A., Machiels, L. et al. Stabilisation and Microstructural Modification of Stainless Steel Converter Slag by Addition of an Alumina Rich By-Product. Waste Biomass Valor 5, 343–353 (2014). https://doi.org/10.1007/s12649-013-9287-y
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DOI: https://doi.org/10.1007/s12649-013-9287-y