The Composition and Morphology Evolution of Oxide Inclusions in Ti-bearing Ultra Low-carbon Steel Melt Refined in the RH Process

During the continuous casting of Ti-stabilized ULC/IF steel grades clogging of the submerged entry nozzle (SEN) is frequently observed. A new statistical evaluation indicates that increasing Ti/Al-ratios in these steels lead to an increase in the occurrence of clogging and its intensity. Investigations of samples of two TiULC heats, taken at the RH-degasser, show a remarkable increase of inclusions due to FeTi-addition. The presence of Ti-bearing alumina particles contrary to the thermodynamical expectations, indicate that their formation takes place as a consequence of FeTi-addition. Laboratoryscale experiments confirm the formation of alumina inclusions containing traces of Ti. Their size is found to be significantly smaller compared to pure alumina inclusions. Rising numbers of small inclusions within the steel are suspected to accelerate the buildup of clogging deposits. Two mechanisms are proposed to explain the formation of these particles. On the one hand ferrotitanium acts as a source of oxygen, resulting in the formation of new inclusions during dissolution. On the other hand, the modification of preexisting deoxidation products in regions with high Ti-contents may play a role.

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“…The number of particles per area is then calculated by Equation

V = \frac{Δ O_{FeTi}}{{true(O true)}_{{Al}_{2} {normalO}_{3}}} \cdot \frac{ρ_{Fe}}{ρ_{{Al}_{2} {normalO}_{3}}}

N_{V} = \frac{6 \cdot V}{π \cdot {\bar{d}}^{3}}

N_{a} = \frac{N_{V} \cdot π \cdot \bar{d}}{Z}

…”

Section: Resultsmentioning

confidence: 99%

Study on the Influence of FeTi‐Addition on the Inclusion Population in Ti‐Stabilized ULC Steels and Its Consequences for SEN‐Clogging

Dorrer

Michelic

Bernhard

et al. 2019

steel research int.

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“…x/3 Al2O3 (s) + Ti = TiOx (s) + 2x/3 Al .......... (7) Al2O3 (s) + m Ti = Al2-nTimO3(s) + nAl.......... (8) It was also assumed that the elemental species like Al and Ti were in the dissolved state because of the partial melting inside the FeTi35 as can be seen from Fig. 12(c).…”

Section: Inclusion Evolutionmentioning

confidence: 99%

“…On an industrial scale also, clusters of Al-Ti-O inclusions after the addition of FeTi to Al-killed steel at the end of RH treatment have been reported. 8) The addition sequence of Al and Ti has been studied in detail 9) to analyze its influence on inclusion behavior. It was observed that irrespective of the addition time of Al or Ti, the final chemistry of the inclusions was alumina.…”

Section: Introductionmentioning

confidence: 99%

Inclusion Formation and Interfacial Reactions between FeTi Alloys and Liquid Steel at an Early Stage

2013

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Titanium is usually added to the liquid steel in the form of ferroalloys with varying Ti concentrations. These titanium sources also contain Al, Ca and O as the main impurities. In the present work, three different titanium sources, namely, pure Ti and two commercially produced Ti alloys i.e. FeTi70 and FeTi35 are studied. The Ti or FeTi was brought in contact with the liquid iron using the suction method, for a predetermined time and quenched. The reaction zone between the liquid Fe and the titanium source was subjected to microstructural investigation. The high Ti concentration region obtained in a pure Ti-Fe reaction couple, the inclusion formation in liquid iron after coming in contact with FeTi70 and the evolution of existing inclusions in FeTi35 after coming in contact with liquid iron have been studied. The present study has helped in understanding the influence of impurities from the Ti source on the dissolution behavior and the inclusion formation. On the basis of this study, it can be concluded that the Ti rich regions formed after the introduction of pure Ti could modify the existing alumina inclusions in liquid steel, the impurities in FeTi70 contribute to the inclusion formation depending upon the availability of O while FeTi35 introduces inclusions to the liquid steel.

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“…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%

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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The Composition and Morphology Evolution of Oxide Inclusions in Ti-bearing Ultra Low-carbon Steel Melt Refined in the RH Process

Cited by 49 publications

References 18 publications

Study on the Influence of FeTi‐Addition on the Inclusion Population in Ti‐Stabilized ULC Steels and Its Consequences for SEN‐Clogging

Study on the Influence of FeTi‐Addition on the Inclusion Population in Ti‐Stabilized ULC Steels and Its Consequences for SEN‐Clogging

Inclusion Formation and Interfacial Reactions between FeTi Alloys and Liquid Steel at an Early Stage

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

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