A kinetic model (effective equilibrium reaction zone model) was developed to simulate the decarburization reaction in the Ruhrstahl Heraeus (RH) degassing process. The model assumes that the chemical reactions reach equilibrium in the designated effective reaction volumes near the reaction interfaces. After the RH degassing process was divided into various reaction zones, the effective reaction volumes of each reaction zone were expressed as a function of the process conditions based on the physical descriptions of the reaction mechanisms. The influence of the chemical reaction between the RH slag and the RH steel to the decarburization phenomena was considered for the first time. The calculated C and O profiles by the present model are in good agreement with the industrial operation data for various steel compositions and process conditions. RH slag can serve as an oxygen reservoir to supply O during the RH decarburization process, which induces the observed deviation of the C and O contents from their ideal stoichiometric trajectory. The present model provides an efficient tool to understand the RH degassing process.

No abstract

IN-HO JUNG and MARIE-ALINE VAN ENDEThe CALPHAD-type computational thermodynamic databases have been developed since 1970. Several commercial computational thermodynamic software equipped with comprehensive and accurate thermodynamic databases and fast Gibbs energy minimization routine are widely used in the design of new materials and the optimization of materials processing. In this study, the FactSage software, which is the most frequently accessed software in high temperature materials processing, is briefly overviewed. The current databases and on-going directions of the thermodynamic database development are discussed. Application examples of FactSage thermodynamics databases to steel processing from the iron ore sintering process to the final metallic coating process are presented. Lastly, the most recent and future application of the FactSage thermodynamic databases to virtual steelmaking process simulations for the so-called industry 4.0 (smart factory) is highlighted.

No abstract

[O] is given next to each point.

The ladle furnace (LF) is widely used in the secondary steelmaking process in particular for the de-sulfurization, alloying, and reheating of liquid steel prior to the casting process. The Effective Equilibrium Reaction Zone model using the FactSage macro processing code was applied to develop a kinetic LF process model. The slag/metal interactions, flux additions to slag, various metallic additions to steel, and arcing in the LF process were taken into account to describe the variations of chemistry and temperature of steel and slag. The LF operation data for several steel grades from different plants were accurately described using the present kinetic model.

Non-metallic inclusions have always been the active subject of steelmaking research to improve the steel cleanliness and to develop the so-called oxide metallurgy technology. Inclusions in molten steel form and grow by the sequence of nucleation, chemical and physical growth and removal. Thus, the size distribution of inclusions evolves continuously with time in molten steel, and significant changes in the steel conditions are reflected in the inclusion size distribution as well as in the inclusion chemistry. This study aims to provide a new approach to interpret the inclusion size distributions. The concept of the Population Density Function (PDF) is introduced to objectively represent a given inclusion size distribution. Several possible applications of PDF analysis are presented to demonstrate the advantages of the utilization of the PDF for understanding the inclusion formation mechanism during the steelmaking process. Several ambitious ideas to utilize the PDF for inclusion size control are also presented.

A thermodynamic database for the oxyfluoride system CaO-MgO-Al2O3-SiO2-Na2O-K2O-Li2O-MnOFeO-F has been developed based on the critical evaluation and optimization of all available experimental thermodynamic and phase diagram data. The developed database can be used for phase diagram and equilibrium solidification calculations for multicomponent systems. Such accurate database with high predictability capability assists in understanding the crystallization behavior of mold fluxes. In addition, a kinetic model was developed to simulate the interactions between the mold flux and molten steel using effective equilibrium reaction volumes combined with the thermodynamic database. The kinetic model successfully reproduced the significant Al2O3 accumulation observed when casting high Al steel with CaO-SiO2 based mold flux. Equilibrium solidification calculation performed on the Al2O3-rich mold slag revealed detrimental changes in the solidification temperature, the primary phase and the evolution of the liquid fraction with temperature.KEY WORDS: continuous casting mold flux; thermodynamic database; equilibrium solidification behavior; kinetic model; steel/slag/inclusion reactions.