IRON AND IRON-CHROMIUM ALLOY SILICA REACTION STUDIES.
Interim rept. 1 Dec 65-30 Nov 66,
DARTMOUTH COLL HANOVER N H THAYER SCHOOL OF ENGINEERING
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This investigation is concerned with the chemical reactions that occur when iron and iron-chromium alloys, which are the basis for high strength steels, are held in contact with silica. The results show that the addition of chromium to the equilibrium system Fe-Si-C-O causes additional condensed phases to occur. Under reducing conditions, the phase iron-chromium spinel with composition between magnetite FeO.Fe2O3 and chromite FeO.Cr2O3 occurs. High Temperatures, 1550 and 1600C, led to the stability of silicate liquid at reducing conditions due to the melting of the spinel phase. This effect lowers the oxidation potential necessary to completely inhibit metal-silica interaction in the presence of chromium compared to pure iron. The general mechanism of metal transport across the mold-metal interface in silica refractory during the casting process is shown to involve liquid metal oxide formation, penetration and solution of the silica, precipitation of solid, complex oxides and finally the reduction of a portion of this oxide to metal. The beneficial effect of chromium in slowing these reactions is the promotion of solid phase formation, increased viscosity of the silicate liquid, decreased solution rate of silica and decreased rate of supply of catalyst ions to the primary reaction interface.
- Physical Chemistry
- Properties of Metals and Alloys