Sorption removal of oxygen by refractory materials from iron-nickel melts

Abstract

The refractory lining in which a metal is smelted has a significant effect on the properties of the metal.An equilibrium concentration of oxygen, which depends on the chemical nature of the crucible material, is established in the molten metal when subjected to a long dwell in the crucible [i]. Under actualconditions, the induction crucible furnace with intense electromagnetic perturbation and a relatively large specific interface surface between the metal and lining, which helps to bring the system (metal-lining) rapidly to the thermodynamic equilibrium, is close to this laboratory situation.It was shown [2] that a metal with a small concentration of vanadium, which is active towards oxygen, more quickly establishes equilibrium with the lining and the concentration of oxygen in it on melting than the same metal without vanadium.The concentration of nitrogen is related to the concentration of oxygen in the metal on melting and this is explained by the difference in surface activity of oxygen and nitrogen at the metal-atmosphere and metal-lining interfaces.Oxygen being the more surface-active element is absorbed in the surface layer of metal and occupies the adsorption centers, thus preventing the removal of nitrogen [2].It was shown in [3] that the role of the metal-lining surface is also active in the deoxygenation and doping of the metal.Thus the existing facts indicate that refractory oxides can be used as sorbents for the removal of oxygen from a liquid metal.There is virtually no data in the literature relating to the sorption tendency of refractories.Therefore the aim of the present study was to investigate the oxygen-sorption behavior of periclase and corundum.The specimens of refractory were prepared in the form of substrates 18 mm in diameter and 5 mm thick and as crucibles to contain 0.25 kg of metal.Refractories of different porosity were obtained by selecting the grainy composition of the original refractory powders and by the use of different pressing pressures and firing temperatures.As the original materials we used fused periclase with a 92.50%* concentration of MgO and corundum with an AI20~ concentration of 96.84%; to the masses we added 1.5% of boric acid.In the experiments we also used corundum and periclase single crystals.The open porosity of the periclase refractories was P~ ~ 27%, P2 ~ 23%, and P3 ~ 21%; of the corundum specimens, P~ ~ 26%, P~ ~ 24%, and P~ ~ 20%.The metal for the experiments (the 80N alloy) was melted in an open induction furnace with a 15-kg capacity magnesite crucible by alloying carbonyl iron with electrolytic nickel, grade NI.Forged and turned metal was remelted in a vacuum induction furnace in a corundum crucible.The characteristics of the metal used a=e given in Table i.The turned metal specimens were stored before the experiment in weighing bottles contain ~ ing carbon tetrachloride.The wetting experiments were carried out on the apparatus described in [4] at 1490~ in an argon medium with a 99.997% concentration of the main metal and 0.0003% of oxygen.The argon w...

Distribution of oxygen between molten steel and oxide refractories

“…For example, Turdzhuman et al [12] showed that oxygen migration from the steel into the MgO and AI20s based refractories amounts to 2.10-3-10 -2 %/mln. This value coincides with the diffusional flux (rate) calculated here.…”

“…Based on the residual oxygen content in the steel and the FeO content obtained from the liquidus lines at 1873~ in the FeO-oxide systems, we calculated the actual distribution coefficient of oxygen, and evaluated the sorption ability of the refractory [12] from the ratio The results are shown in Table i.…”