The effects of leaching on the mineral phases in argon-oxygen decarburization of stainless-steel slag

The major mineral compositions of an original argon-oxygen decarburization (AOD) slag, a natural leaching residue, an acid-leaching residue and an alkaline leaching residue were analyzed using X-ray diffraction.The volume percentages and microstructures of the main phases in the original slag and the leaching residues were observed using mineral microscopy.The results show that the main phases in the AOD slag were dicalcium silicate (C2S), merwinite (C3MS2), pyroxene and rankinite; the volume percentages of the main mineral phases during leaching were changed.In the natural leaching residue and acid-leaching residue, the amount of C2S decreased, and the contents of rankinite, pyroxene and C3MS2 increased compared with those in the original slag.In the alkaline leaching residue, the change in the volume percentages of the major mineral phases was very small.In the original slag, C2S mainly existed as fine-grained aggregates and columns with relatively coarse grain sizes.In the neutral leaching residue and acid-leaching residue, C2S had short columnar and fine acicular shapes and a small particle size.The particle sizes of the other mineral phases in the neutral and acid-leaching residues, such as C3MS2, rankinite, and pyroxene, increased.The morphology and volume percentage of the minerals in the alkaline leaching residue were similar to those in the original residue.It was concluded that the main cause of the above phenomena was the hydration of C2S and the insolubility of rankinite in water, which resulted in the formation of C3MS2.