Micrograph evidence of meniscus solidification and sub-surface microstructure evolution in continuous-cast ultralow-carbon steels

Sengupta, Joydeep; Shin, Hee Jun; Thomas, Brian G.; Kim, S.-H.

doi:10.1016/j.actamat.2005.10.044

Cited by 60 publications

(40 citation statements)

References 16 publications

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“…This hook formation has been analyzed extensively by Thomas et al [6] and Sengupta and colleagues [7,27] through a model that reconstructs the hook's shape based on micrographs and animations. These micrographs show dendritic growth at both sides of the original meniscus line confirming the immersion and overflow process.…”

Section: Hook Formationmentioning

confidence: 99%

A Unified Mechanism for the Formation of Oscillation Marks

López¹,

Mills

Lee

et al. 2011

Metall Mater Trans B

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Oscillation marks (OMs) are regular, transverse indentations formed on the surface of continuously cast (CC) steel products. OMs are widely considered defects because these are associated with segregation and transverse cracking. A variety of mechanisms for their formation has been proposed (e.g., overflow, folding, and meniscus freezing), whereas different mark types have also been described (e.g., folded, hooks, and depressions). The current work uses numerical modeling to formulate a unified theory for the onset of OMs. The initial formation mechanism is demonstrated to be caused by fluctuations in the metal and slag flow near the meniscus, which in turn causes thermal fluctuations and successive thickening and thinning of the shell, matching the thermal fluctuations observed experimentally in a mold simulator. This multiphysics modeling of the transient shell growth and explicit prediction of OMs morphology was possible for the first time through a model for heat transfer, fluid flow, and solidification coupled with mold oscillation, including the slag phase. Strategies for reducing OMs in the industrial practice fit with the proposed mechanism. Furthermore, the model provides quantitative results regarding the influence of slag infiltration on shell solidification and OM morphology. Control of the precise moment when infiltration occurs during the cycle could lead to enhanced mold powder consumption and decreased OM depth, thereby reducing the probability for transverse cracking and related casting problems.

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Section: Hook Formationmentioning

confidence: 99%

A Unified Mechanism for the Formation of Oscillation Marks

López¹,

Mills

Lee

et al. 2011

Metall Mater Trans B

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“…This is primarily because of the fact that the progressively increasing emphasis on the quality of continuously-cast (CC) products mandates much tighter control of solidification process variables and would require a more precise definition of the relationship between cast microstructure and process parameters. Although some studies to quantify the dendritic morphology in the continuous casting situation have been reported, [19][20][21][22][23][24] information regarding correlation of the cast microstructure, viz. dendrite arm spacings (DASs), with solidification variables and operational parameters in industrial scale, CC high-carbon steel billets/slabs is still very much limited.…”

Section: Introductionmentioning

confidence: 99%

Quantification of the Solidification Microstructure in Continuously-Cast High-Carbon Steel Billets

Ganguly

Choudhary

2009

Metall Mater Trans B

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In this work, an attempt has been made to investigate the relationship between the cast microstructure and solidification variables in industrial scale, continuously-cast (CC) highcarbon steel billets. Toward these, theoretical and experimental studies are undertaken to predict the evolution of dendrite arm spacing (DAS) in the columnar zone of CC billets. Several billet samples collected from the continuous casting shop of Tata Steel are used to characterize the solidification microstructure, and interdendritic arm spacings (both primary and secondary) are measured. Macrostructural examination of the billet samples indicates predominantly columnar structure in all billets. Dendrite arm spacings vary over a wide range indicating nonuniform secondary cooling. A mathematical model is also developed to describe the relationship between dendrite structures and solidification parameters. The model considers the effect of change of volume on solidification and provides a quantitative estimation of variation of DAS as a function of distance from the product surface. Results predicted by the mathematical model are compared with the experimental measurements and good agreement can be observed in this regard, thereby establishing the authenticity of the proposed formulation.

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“…Now-a-days, newer and more sophisticated evaluation techniques are available and have become quite popular. 16,17) However, in the present work, samples for chemical analysis were obtained by the conventional drilling technique where the appropriate drill size was selected on the basis of the average size of segregation spots observed in the S-print. Drill intervals along the billet axis were also decided on basis of observed segregation profiles in the Sprints of the longitudinal section.…”

Section: Methodsmentioning

confidence: 99%