Numerical simulation of modification of non-metallic inclusions by calcium treatment in the argon-stirred ladle

Abstract

Nowadays, depending on the steel grade, Ca treatment with the aim of modifying the morphology and melting temperature of non-metallic inclusions is performed in the secondary steelmaking process. The addition of calcium to steel melts rises a technological challenge because at steelmaking temperatures Ca has the tendency to vaporize from the ladle. Efforts are actively pursued in developing solutions that increase Ca yield and improve repeatability of results from treatment to treatment. This work presents a two-phase Euler-Euler flow model of a steel ladle with gas stirring through bottom porous plugs. The model considers that before gas exits through the ladle top, some Ca is transferred from the gas to the liquid steel. The yield is thus defined as the ratio between the Ca transferred to the steel and the total calcium injected into the ladle. The fluid-dynamic calculations are coupled with ArcelorMittal thermodynamic software CEQCSI to get the evolution of the local concentration of dissolved species and non-metallic inclusions assuming local thermodynamic equilibrium. Industrial trials have been performed at one of ArcelorMittal’s facilities with the aim of obtaining data to validate the model. Samples of steel were taken before, during, and after the Ca injection treatment. The total Ca content and the inclusion populations in the steel samples can be compared against the results given by the model, as well as the measured and calculated Ca yield.

Investigating Chemical Heterogeneity in Inclusion Populations: A Multivariate Population Balance Model Study in Gas-Stirred Ladles

“…This type of work, led by KTH in Stockholm and the University of Urbana–Champaign, was considered a benchmark in this field in the early 2000s. Later on and thanks to the increase in computational power, PBMs have been coupled with CFD to track the size distribution of NMIs. ,− In 2014, Rimbert et al developed a reduced-order multicomponent PBM to track the NMI population of titanium aluminates in liquid steel. The authors considered nucleation–growth, aggregation, and removal as the fundamental mechanisms of the process and accounted for different chemical components because of the coupling with thermodynamic databases.…”

Evolution behaviour and modification mechanism of inclusions in NM500 wear-resistant steel with calcium treatment

“…Mg dissolved in molten steel will further react with Al 2 O 3 inclusions in steel to form MgO•Al 2 O 3 inclusions. The reaction is expressed in Equation (19), and the corresponding Gibbs free energy is shown as Equation ( 20) [44]. In addition, MgO and Al 2 O 3 in slag or lining can also react to form MgO•Al 2 O 3 inclusions theoretically.…”

“…According to Table 1, thermodynamic calculation and SEM-EDS analysis are widely used to study the formation and modification mechanism of inclusions in different steel grades, the evolution law of compositions, sizes, numbers and morphology characteristics of the different inclusions after calcium treatment in different steel grades [1][2][3]6,8,10,[12][13][14][21][22][23][24][25][26], and the optimization and improvement of calcium treatment process [4,5,9,20,29], as well as the mechanism reducing nozzle nodulation and the degree of tundish stopper erosion with calcium treatment [27,28]. The modification and local concentration of inclusions, rate-controlling step of inclusion modification and change of inclusion compositions with different reaction times in calcium treatment steel can be studied in combination with numerical simulation and kinetic models [7,11,[15][16][17][18][19].…”