Inclusion Characterization of Titanium Stabilized Ultra Low Carbon Steels: Impact of Oxygen Activity before Deoxidation

Lyons, C.; Kaushik, Pallava

doi:10.1002/srin.201100163

Cited by 14 publications

(12 citation statements)

References 10 publications

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“…Ti-aluminate inclusions aggregate and become larger from the RH furnace to the tundish. Thus, the distribution of the size of the inclusions from samples of the ladle or the tundish is not a function of deoxidation practice [25]. The average size of the ti-aluminate inclusions increases with increasing the levels of Ti in ULC steel stabilized with titanium [25].…”

Section: Characteristics Of the Principal Identified Inclusionsmentioning

confidence: 95%

CARACTERIZAÇÃO DE INCLUSÕES NÃO METÁLICAS EM UM AÇO ULTRA BAIXO CARBONO ESTABILIZADO AO Ti E DESOXIDADO AO Al

Leão¹,

Filho²,

Ferreira³

et al. 2017

ABM Proceedings

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The present work is based on the characterization of nonmetallic inclusions in Ti stabilized ultra-low carbon steel, produced in a large steel mill. Due to a large incidence of submersed valve clogging in a continuous casting, the study is important in order to know the characteristics of the inclusions which are causing the problem. Total of 24 heats were sampled in the tundish and manually analyzed with a scanning electron microscope. The results revealed that 98.65% of the 3183 inclusions analyzed were solid in steelmaking temperature and 66.54% were alumina. The solid inclusions of alumina have low wettability for the iron bath, showing a high tendency of agglomeration in the submersed valves, affecting the castability. It has been concluded from the results and literature that some alternative measures such as the application of the treatment with calcium, precautions to avoid steel re-oxidation and the total or partial replacement of the pre-deoxidized element; would reduce the obstruction problem.

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Section: Characteristics Of the Principal Identified Inclusionsmentioning

confidence: 95%

CARACTERIZAÇÃO DE INCLUSÕES NÃO METÁLICAS EM UM AÇO ULTRA BAIXO CARBONO ESTABILIZADO AO Ti E DESOXIDADO AO Al

Leão¹,

Filho²,

Ferreira³

et al. 2017

ABM Proceedings

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“…2 indicates that the heat treatment of the processed heats in terms of the chemical reheating leads to a significant deterioration of steel cleanliness through the increase of concentration of Al2O3 inclusions in heat, mainly during the oxygen blowing for the reheating [8]. Although this finding is a common feature of most of the available research work on this topic, opinions and findings concerning the overall final level of steel cleanliness with a consequent impact on its castability and quality of the final processed material differ [9][10][11][12][13]. …”

Section: Introductionmentioning

confidence: 92%

Influence of Chemical Reheating at Rh Degasser on Cleanliness of if Steel Grades

Molnár¹,

Tréfa²,

Hertneky³

et al. 2016

Acta Metall Slovaca

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Production practices of IF (interstitial free) steel grades intended for the most qualitatively demanding automotive applications calls for their continuous optimization. Precise control of steelmaking operation conditions leads to a minimization of clogging issues during their casting, but is also related to surface quality imperfections of finished material. With the aim to study the impact of RH degasser practices on cleanliness of the IF steel grades, the influence of heat chemical reheating was verified. While detailed analyses confirmed overall worse results and a higher presence of specific nonmetallic particles on steel samples collected from such treated heats, the limited reheating practice did not seem detrimental. Key words: RH degasser, chemical reheating, IF steel, steel cleanliness IntroductionIn general, it can be said that to date, there have only been a few research papers published regarding the impact of chemical reheating on the cleanliness of heats processed at an RH (RH-OB) degasser. This technological operation represents one way of feeding the oxygen into the liquid steel. As well, depending on a number of other process parameters, it can strongly affect the degree of its cleanliness, casting conditions and consequently, the quality results of the final processed material. Fig. 1 characterizes the typical temperature increase related to the amount of oxygen blown at the RH degassing station with steel grades deoxidized only by aluminum, or by a combination of aluminum and silicon. It is evident that the processed steel grades deoxidized only by aluminum have particularly at high volume of oxygen blown, higher efficiency of the chemical reheating process [1 -4]. In this regard, the greatest attention should be paid to the conditions of formation and to the ways of minimizing the occurrence of mainly small alumina inclusions (under 10µm). Besides this, the area of concern is often focused also on other complex types of inclusions, in particular based on Titanium, whereas in view of its alloying, these steel grades exhibit the negative impact thereof on the conditions of removing inclusions from the molten steel and related issues during their casting [5 -7]. Fig. 2 indicates that the heat treatment of the processed heats in terms of the chemical reheating leads to a significant deterioration of steel cleanliness through the increase of concentration of Al2O3 inclusions in heat, mainly during the oxygen blowing for the reheating [8]. Although this finding is a common feature of most of the available research work on this topic, opinions and findings concerning the overall final level of steel cleanliness

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“…In addition, differences in plant configurations, Al deoxidation and FeTi addition practices as well as the design of the fluid flow control system of the casting machine also have a significant influence on clogging (eg. [2]). This complexity of possible influencing parameters may contribute to the widely spread and partly inconsistent research findings on the clogging of Ti-stabilized ULC steel; a comprehensive overview of the state of knowledge was recently published by Dorrer et al [3].…”

Section: Introductionmentioning

confidence: 99%

The Role of FeTi Addition to Micro-inclusions in the Production of ULC Steel Grades via the RH Process Route

Bernhard

Dorrer

Michelic

et al. 2019

Berg Huettenmaenn Monatsh

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In the production of ULC steel grades via the RH process route, Al is added first for deoxidation after the end of decarburization and FeTi follows after a certain period of separation of alumina particles and the related reduction of the total oxygen content. The FeTi addition is well known to cause clogging problems in the following casting process. The analysis of plant data by voestalpine Stahl in Linz indicates an increasing clogging tendency with a higher Ti/Al ratio in the steel. Automated SEM/EDS investigations on lollipop samples show the existence of a newly nucleated Ti-containing alumina particle population after the FeTi addition. These particles are comparably smaller than the alumina particles and, even if thermodynamically unstable, they still exist as a large population of small particles in samples taken from the tundish. The addition of Al and FeTi into a molten steel sample with controlled initial oxygen activity for varying Ti/Al ratios was simulated in laboratory scale afterwards. Just like in the plant, a new population of small Ti-containing alumina particles nucleates, with the size and number depending on the Ti/Al ratio in the melt. Laboratory experiments and plant observations are in consistence with each other and indicate-for the underlying process route and process parameters-some countermeasures for the better control of clogging.

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Inclusion Characterization of Titanium Stabilized Ultra Low Carbon Steels: Impact of Oxygen Activity before Deoxidation

Cited by 14 publications

References 10 publications

CARACTERIZAÇÃO DE INCLUSÕES NÃO METÁLICAS EM UM AÇO ULTRA BAIXO CARBONO ESTABILIZADO AO Ti E DESOXIDADO AO Al

CARACTERIZAÇÃO DE INCLUSÕES NÃO METÁLICAS EM UM AÇO ULTRA BAIXO CARBONO ESTABILIZADO AO Ti E DESOXIDADO AO Al

Influence of Chemical Reheating at Rh Degasser on Cleanliness of if Steel Grades

The Role of FeTi Addition to Micro-inclusions in the Production of ULC Steel Grades via the RH Process Route

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