Prediction of deoxidation and inclusion precipitation in semikilled steel

Abstract

A generalized thermodynamic calculation procedure for the prediction of oxide inclusion precipitation of desired compositions for Mn-Si-Al deoxidation has been developed. The procedure directly uses established ternary iso-activity diagrams in the MnO-SiO 2 -Al 2 O 3 system, and does not assume any slag model. The thermodynamic data required for calculation, such as deoxidation constants, interaction coefficients, and activity vs composition relations in the oxide phase, reported in the literature, were examined and the ones considered to be most satisfactory were accepted. On the basis of the computed results for inclusions in the spessartite phase field of the MnO-SiO 2 -Al 2 O 3 system, discussions have been presented on the applicability of the regular solution model as well as an empirical model reported in the literature. Some predictions for plain carbon steels have also been included.

A Phenomenological Investigation on the Control of Oxides at the Interface Using an Electrochemical Cell

“…To maintain a clean interface without oxide inclusions and also to decompose already exiting oxide inclusions, the oxygen concentration at the interface must be maintained below the thermodynamic equilibrium oxygen concentration dependent upon the specific deoxidizer such as Al or Ti. According to many previous researches, [14][15][16][17][18][19][20][21][22] the maximum value of soluble oxygen con- centration without oxide precipitation is below 6 ppm. Thus in the present work, the interfacial oxygen concentration of less than 3 ppm with an external direct current of 0.1 A should inhibit and decompose oxides.…”

“…[14][15][16][17][18][19][20][21][22] However, recent work by Suito et al [23][24][25] suggest the existence of a super-saturation phenomenon required for aluminum oxide formation in molten steel at 1 873 K and defined the ratio between the super-saturation concentration and the equilibrium concentration as the critical super-saturation ratio. Due to the necessity of an excess driving potential, aluminum oxide formation in the bulk Fe-Al-O alloy is somewhat difficult even though the bulk oxygen is above the thermodynamic equilibrium concentration.…”

Investigation on the Decomposition of Al2O3 Using an Electrochemical Method

“…The interaction coefficients of the dissolved elements in liquid steel have been previously calculated in the literature. [20][21][22] Table 2 shows the values of the interaction coefficients of aluminum and oxygen in liquid Fe-Al-O used in this study as a function of temperature.…”

Castability of Mn–Si Killed Low Carbon Wire Rod Steel

“…7) Details of thermodynamic model and calculation procedure have been reported elsewhere. 5) Results of thermodynamic predictions are shown in the form of inclusion precipitation diagram in Fig. 4.…”