THE STRUCTURAL EFFECT ON THE KINETICS OF ACID LEACHING REFINING OF FE-SI ALLOYS

The kinetics of refinement of Fe-Si alloys by acid leaching is affecte d by their structural state. Two different phase constitutions were st udied to access this effect: an industrial alloy with a low Al/Ca rati o and a laboratory-prepared alloy with a high Al content. The first co ntains silicon, FeSi2 (tet.), FeSi2 (orth.), beyond a quaternary phase Fe-Al-Si-Ca (Caalsifer), CaAl2Si1.5, CaSi2, Al-Fe-Si as minor phases. The precipitation of Al-Fe-Si phases is induced in the second by the high Al/Ca ratio. In a previous study, leaching experiments by a two-s tep procedure have shown that Ca-Al-Si, Caalsifer and Al-Fe-Si phases are more soluble. The Cracking Shrinking Model (CSM) was applied to ex plain the behaviour of the industrial alloy. In the present study, it is shown that the same model applies to the kinetics of dissolution of the laboratory-prepared alloy and also, that an adequate control of F e/Al vs. Si/Ca ratios may improve the attainable refining yield.