Study of calcium cored wire injection in an industrial steel ladle

Abstract : In order to improve the castability of some steel grades, calcium is added to the liquid steel to modify and control the nature of oxide and sulphide inclusions present in the steel. As a result of the treatment with calcium solid inclusions that provoke clogging of the casting nozzles are converted into liquid ones that do not clog the nozzles. Cored wire injection has matured as one of the leading technologies to perform calcium additions since it offers a higher calcium recovery than other methods and its operation is simple and inexpensive. This work, divided into two main axes, clarifies the mechanisms of dissolution of the cored wire during its injection, the dissolution and transport of calcium once it has been released into the steel ladle, and the chemical modification of inclusions by this element. The first axis revolves around DissolFil, a numerical model describing the thermal phenomena occurring during the process of injection of a cored wire into a liquid steel bath. In parallel, an experimental study of immersion of cored wires into quiescent steel baths that was carried out with the aim of validating the model. The simulation results put into evidence the importance of the wire injection velocity as the operating parameter that needs to be tailored as a function of the wire design and steel bath superheat in order to optimize the release depth of calcium in the steel ladle. The second axis comprises a model of dissolution and transport of calcium in the steel ladle and inclusion modification, coupling fluid-dynamics and thermodynamics by using the Ansys Fluent (fluid-dynamics) and CEQCSI (thermodynamics) calculation codes. The model was validated with data from steel samples obtained in dedicated industrial trials. We highlight boundary layer mass transfer from calcium bubbles into the liquid steel as the dominant calcium dissolution mechanism. Furthermore, the global modification of solid inclusions into liquid ones depends strongly on the mixing and homogenization in the ladle and the steel chemical composition.
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https://hal.univ-lorraine.fr/tel-02131520
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Submitted on : Thursday, May 16, 2019 - 1:08:34 PM
Last modification on : Wednesday, September 4, 2019 - 2:06:04 PM

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  • HAL Id : tel-02131520, version 1

Citation

Edgar Ivan Castro Cedeño. Study of calcium cored wire injection in an industrial steel ladle. Materials Science [cond-mat.mtrl-sci]. Université de Lorraine, 2019. English. ⟨NNT : 2019LORR0019⟩. ⟨tel-02131520⟩

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