Abstract
A novel study to characterise electric arc furnace (EAF) slags in the production of duplex stainless steel at the process temperatures was performed. The investigation is focused on determining the microstructural evolution of the EAF slag during and at the end of the refining period. In this regard, slag sampling was done at three stages from seven EAF duplex stainless steel heats (21·5–22·5 wt‐%Cr, 1·6–5·7 wt‐%Ni and 0·3–3·2 wt‐%Mo). More specifically, the samples were collected before FeSi addition, after FeSi injection and just before tapping. Collected samples were analysed by light optical microscopy and SEM energy dispersive X‐ray spectroscopy to characterise the high temperature microstructure of the slag phases. In addition, X‐ray diffraction analysis was used to verify the petrographical results. It was observed that at all process stages, the duplex steel slag contains molten oxides, magnesiochromite spinels and metallic droplets. However, before the FeSi addition, the slag also contains calcium chromite crystals. In this stage, the slag has a high viscosity, which drops to lower level after FeSi injection. Furthermore, depending on the basicity, the slag may contain other solid phases such as perovskite and calcium silicate.
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