Application Example: Kinetics of Steel Refining in a Ladle Furnace
This in-depth example shows how to set up a full kinetic simulation of steel refining in a ladle furnace using the Process Metallurgy Module in Thermo-Calc. The Process Metallurgy Module uses the Effective Equilibrium Reaction Zone model (EERZ) to simulate the kinetics of the process.
Ladle furnace process
Effective Equilibrium Reaction Zone model (EERZ)
Process Metallurgy Module
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This example includes a video, which shows you how to set up the kinetic simulation in the Process Metallurgy Module.
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This in-depth example includes:
A description of the kinetic model used in the Process Metallurgy Module
An explanation of how to set up a kinetic simulation in the Process Metallurgy Module
After steelmaking, which is mostly performed in a basic oxygen furnace (BOF) or electric arc furnace (EAF), steel is usually tapped into a ladle where certain additions are made (deoxidation agents, slag formers, certain alloying elements) and then transferred to the ladle furnace (LF). The LF fulfils many purposes in the steel refining process, the most important being:
Temperature control / heating by an electrical arc.
Mixing by Ar or N2 bubbling through porous plugs in the bottom of the ladle to achieve homogeneous temperature and composition throughout the ladle.
Removal of unwanted non-metallic phases / inclusions such as corundum (Al2O3), liquid oxide inclusions, spinel, on so on, by flotation, aided by Ar or N2 bubbling.
Modification / engineering of non-metallic inclusions so that they are not detrimental for the downstream processing and/or the final product.
Removal of unwanted volatile elements such as Pb, Zn, Sn, and so on. Due to their high vapor pressure, these elements are enriched in the rising Ar or N2 bubbles. After the gas escapes out of the ladle and cools, they condense, forming copious amounts of dust.
Removal of unwanted elements such as sulphur by liquid steel / slag reactions.
Lowering of the dissolved gas content. In the LF this is mainly achieved through chemical reactions. For direct removal of dissolved gas, vacuum degassing (VD) is usually required.
Alloying and trimming of the steel to achieve the exact alloy composition required by the specification of the steel that is to be produced.
The reactions taking place in a LF are a complex interplay between equilibrium thermodynamics that define the direction of chemical reactions, and kinetics that define how fast the equilibrium state is approached.
About this Example
In this example, a full kinetic simulation of the ladle furnace refining process schematically shown in the image below is set up using Thermo-Calc’s Process Metallurgy Module. The simulation is based on an LF process described in a publication by Graham and Irons , and the results of the simulation are compared to their experimentally determined steel, slag and inclusion composition as a function of processing time.
An overview of the ladle furnace process that is simulated in this example. Each ladle represents one time-step in the process when additions are made or heat or cooling is applied to refine the steel.