A study on the mechanism of reaction between refractory materials and aluminium deoxidised molten steel

Abstract

The conditions of formation of inclusions in steel during ladle refining in MgO‐C lined ladles have been investigated in laboratory experiments at 1873 K in MgO‐C crucibles with 50 g iron. From both the experimental results as well those of a thermodynamic study conducted in parallel, the following conclusions can be made about the reaction mechanism between the MgO‐C refractory and aluminium deoxidised molten steel: At steelmaking temperature an internal oxidation‐reduction occurs in the MgO‐C refractory. The formation of a thin oxide layer at the interface is due to the reaction between magnesium vapour and aluminium dissolved into the molten steel and the CO(g) generated by the reaction between MgO and C in the crucible walls. The oxide inclusions formed in the steel have been shown mainly to consist of MgO, Al2O3 or mixture of them. Some of the finest inclusions are considered to be formed as secondary inclusions during cooling and solidification of the steel and they are connected only with the diffusion of magnesium from the crucible to the molten steel. The thermodynamic calculations indicate that during vacuum refining, as the pressure decreases, the chemical compatibility of carbon‐bonded magnesia for ladle lining decreases.

Magnesium Non-metallic Inclusions in Non-oriented Electrical Steel Sheets

“…21) This shows that even at a very low external pressure there are thermodynamic conditions under which the reaction of magnesium with molten steel occurs.…”

Corrosion Mechanism of Commercial MgO–C Refractories in Contact with Different Gas Atmospheres

“…The confirmation of a dense layer formation on the surface of the sample was achieved by the observation of the cross section of the sample after the oxidation test. It is interesting to note that the authors observed an increase in the oxidation rate when the oxygen potential pressure changes from 3.7ϫ10 2 Pa to 2.1ϫ10 4 Pa, as illustrated in Fig. 2.…”

“…[1][2][3][4] In MgO-C brick, carbon is also oxidized by magnesia according to the following reaction: The free energy changes for Eqs. (1)-(3) in the temperature range 298-2 000 K can be calculated as follows using standard reference tables 5) : DG 1 ϭϪ615 600ϩ1 118.23TϪRT ln P Mg ϪRT ln P CO .... (4) ...... (5) ......... (6) where p Mg is the partial pressure of Mg, p O2 is the partial pressure of O 2 and p CO is the partial pressure of CO.…”

Interaction between Molten Steel, Alumina Lining Refractory and Slag Phase

“…It is of great importance to investigate the reaction between ling refractory and the molten steel in order to control the generation of the exogenous inclusions from lining refractory. In order to clarify the reaction among steel, slag and lining refractory, theoretical and experimental work have been reported [4][5][6][7]. Brabie investigated the mechanism of the reaction between the MgObased ling refractory and Al killed steel and found that there was a thin oxide layer at the interface due to the reaction between the magnesium vapor and the dissolved aluminum [4].…”