Reoxidation of Al-Ti Containing Steels by CaO-Al2O3-MgO-SiO2 Slag

Park, Dong-Chul; Jung, In‐Ho; Rhee, Peter Chang Hee; Lee, Hae-Geon

doi:10.2355/isijinternational.44.1669

Cited by 73 publications

(62 citation statements)

References 12 publications

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“…The Ti-rich and Al-rich phases are encapsulated in a thin but continuous shell of pure Al2O3. Similar complex inclusions were also reported by Park et al 4) and Doo et al 5) from a sample taken at the RH-OB degasser after Ti addition, where they were believed to be in liquid state (at least inner side). The overall chemical composition (Ti#) of the inner side of the inclusion is about 0.66-0.76 as defined above, Ti/(Ti+Al/2), which is in good agreement with the present results.…”

Section: Existence Of Liquid Ti-al-o Oxide Inclusionssupporting

confidence: 85%

“…For this reason, the interaction between existing NMI in liquid steel and the various installations is in the center of attention for secondary refining process. Recently, details of the inclusion formation of Ti-alloyed Al-killed steel grades [1][2][3][4][5] and its physical and chemical development during reoxidation are receiving considerable attention. From these studies, it is being recognized that inclusions in the Al-Ti-Fe-O system may react sensitively on the details of the secondary steelmaking treatment, such as the oxygen balance achieved.…”

Section: Introductionmentioning

confidence: 99%

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Inclusion Population Evolution in Ti-alloyed Al-killed Steel during Secondary Steelmaking Process

et al. 2012

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This paper presents a new approach towards the evolution of non-metallic inclusion (NMI) populations in Ti-alloyed Al-killed steels, based on an extensive inclusion analysis campaign at Tata Steel Europe, IJmuiden Works. Automated SEM techniques were used to characterize the inclusion populations in 120 steel samples taken from nine heats out of two casting series of this steel grade. As NMI in Ti-alloyed Alkilled steels are overwhelmingly dominated by chemically simple Al2O3, most of the process relevant information lies in the analysis of particle size distribution during the secondary steelmaking process. The population density function (PDF) concept was applied, for the first time, to the characterization of inclusion size distributions sampled from secondary steelmaking practice. Two size distribution forms predominate in the entire dataset: i) Lognormal size distributions associated with active nucleation and growth of alumina (deoxidation and reoxidation), indicating net transfer of matter between NMI and solutes in liquid steel and ii) Power-law size distributions, associated with an inclusion population in chemical equilibrium with the melt and subject to collision/breakup processes controlling the distributions. Based on inclusion PDF observations, it is found that the size distribution of alumina inclusions suspended in steel melt, after equilibration and effective float out of large inclusions, tends to approach a Reference Distribution of powerlaw type function (f(r) = a ⋅ r -3.5 ) that appears to be a fundamental feature of the alumina-steel system. This Reference Distribution can guide efforts to improve and engineer inclusion populations for a better controlled steel product.KEY WORDS: non-metallic inclusion; inclusion population density function; inclusion size distribution; secondary steelmaking.

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Section: Existence Of Liquid Ti-al-o Oxide Inclusionssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Inclusion Population Evolution in Ti-alloyed Al-killed Steel during Secondary Steelmaking Process

et al. 2012

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“…(Thermodynamic calculations using FactSage 6) show that neither Mn nor Si form oxide inclusions under their experimental conditions). Park et al 34) also observed Al-Ti-O inclusions during reoxidation experiments on Alkilled and Ti-bearing steel at 1 600°C. In their study, twolayered inclusions of an unknown Al-Ti-O phase covering a core Al 2 O 3 solid were frequently observed.…”

Section: Al 2 O 3 -Ti 2 O 3 Binary Systemmentioning

confidence: 90%

Thermodynamic Modeling of the Al2O3–Ti2O3–TiO2 System and Its Applications to the Fe–Al–Ti–O Inclusion Diagram

Jung

Eriksson

et al. 2009

ISIJ Int.

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a database of model parameters has been prepared. The Modified Quasichemical Model was employed for the molten oxide phase. The thermodynamic modeling predicts the existence of a liquid oxide Al 2 O 3 -Ti 2 O 3 -TiO 2 phase at secondary steelmaking conditions. The database was used to calculate the inclusion diagram for Al-Ti deoxidation at 1 600°C.KEY WORDS: thermodynamic modeling; Al 2 O 3 -Ti 2 O 3 -TiO 2 , Al-Ti deoxidation, inclusion; FactSage.and Ti 3ϩ ions are distributed as independent particles in the liquid solution, not as ion pairs.) The following short-range ordering quasichemical reactions are taken into account: , and (A-B) represents a second-nearest-neighbor A-B pair. The Gibbs energies of this reaction Dg AB are the model parameters, which can be expanded as empirical functions of composition. The Gibbs energies and all second-nearest-neighbor "coordination numbers" of the three liquid components used in the model are the same as in previous studies. 11,12) That is, the coordination number of Ti 3ϩ is identical to that of Al 3ϩ , which is 3/4 that of Ti 4ϩ . Optimized model parameters for the Ti 2 O 3 -TiO 2 binary liquid phase were recently reported, 12) while optimized parameters for the Al 2 O 3 -TiO 2 and Al 2 O 3 -Ti 2 O 3 binary liquids are reported in the present study. The properties of the ternary slag solution are estimated from the optimized binary model parameters using an asymmetric "Toop-like" 13) approximation with TiO 2 as the "asymmetric component". No additional adjustable ternary model parameters are used for the liquid phase. The optimized model parameters are listed in The corundum phase is an Al 2 O 3 -rich solid solution, with a trigonal structure based on the hcp oxygen-packing scheme which dissolves a small amount of Ti 2 O 3 . The ilmenite phase is a Ti 2 O 3 -rich solid solution, with a hexagonal structure, which dissolves a limited amount of Al 2 O 3 . In the absence of any experimental data, it is assumed that TiO 2 is stable only to a negligible extent in both phases.The molar Gibbs energies of the corundum and ilmenite phases are modeled as ideal ionic substitutional Henrian solutions by the following expressions: Kang et al. 12) in order to reproduce the experimental solubility data over a wide range of temperatures. The thermodynamic model of Kang et al. 12) is adopted in the present study with no modification. D. Stoichiometric CompoundsThe Gibbs energy functions of several Magnéli phases (Ti n O 2nϪ1 , nՆ4) and Ti 3 O 5 are taken from the previous studies 11,12) with no modification. The Gibbs energies of Al 2 TiO 5 (tialite) and Al 4 TiO 8 are evaluated in the present study. In the absence of any experimental evidence to the contrary, all of these phases are assumed to be stoichiometric compounds. 12) reoptimized the model parameters of the liquid oxide and rutile phases in order to reproduce the phase diagram more accurately. The details of the thermodynamic modeling and model parameters can be found in the previous study. Critical Evaluation and12) Iso...

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“…This evolution is believed to be due to the selective oxidation sequence of element during the experiments. [20][21][22] Since the original steel contains around 400 ppm [Al] and 700 ppm [Ti], oxygen supplied from the gunning material preferably reacts with [Al] to form Al 2 O 3 (as shown in Fig. 6).…”

Section: Qualitative Assessment Of Inclusion Evolutionmentioning

confidence: 99%

Interaction between Steel and Distinct Gunning Materials in the Tundish

et al. 2014

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Gunning materials are used as a dispensable protective layer to extend the tundish life. Their use however, affects the steel cleanliness by introducing steel reoxidation and exogenous inclusions. In the present work, the interaction between molten steel and three types of refractory, i.e. MgO, Al2O3, and MgO + 2MgO·SiO2 based gunning materials (GM) have been investigated. Compared to MgO and MgO + 2MgO·SiO2 GM, the Al2O3 GM exhibited better infiltration resistance to molten steel. The two phase MgO + 2MgO·SiO2 GM was found to be less prone to steel infiltration than single-phase MgO GM. The compositional evolution of steel influenced by gunning material was experimentally measured and also predicted with thermodynamic equilibrium calculations. The steel cleanliness in terms of inclusion size, number density, area fraction and morphology was measured and evaluated. Although large Al2O3/AlTiOX inclusions were formed through the erosion of Al2O3 GM, the use of Al2O3 GM resulted in an improved steel cleanliness due to its lower content of reducible compounds compared to that of MgO and MgO + 2MgO·SiO2 GM.

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Reoxidation of Al-Ti Containing Steels by CaO-Al2O3-MgO-SiO2 Slag

Cited by 73 publications

References 12 publications

Inclusion Population Evolution in Ti-alloyed Al-killed Steel during Secondary Steelmaking Process

Inclusion Population Evolution in Ti-alloyed Al-killed Steel during Secondary Steelmaking Process

Thermodynamic Modeling of the Al2O3–Ti2O3–TiO2 System and Its Applications to the Fe–Al–Ti–O Inclusion Diagram

Interaction between Steel and Distinct Gunning Materials in the Tundish

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