Prediction of Equiaxed Crystal Ratio in Continuously Cast Steel Slab by Simplified Columnar-to-Equiaxed Transition Model

Shibata, Hiromitsu; Itoyama, Seiji; Kishimoto, Yasuo; Takeuchi, Shuji; Sekiguchi, Hiroshi

doi:10.2355/isijinternational.46.921

Cited by 35 publications

(36 citation statements)

References 22 publications

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“…However, this approach is difficult to employ in practice, as it requires the knowledge of several parameters that are not available or can only be computed after the combined thermal and microstructural analysis. 10,11) As shown by Kurz et al,17) however, the nucleation undercooling can be neglected when R is high (i.e., ΔTn ≈0), and the columnar to equiaxed transition occurs when: (11) where n and C depend on the alloy system. 17) Equation (11) can therefore be conveniently used to evaluate the role of relatively small variations in the operating conditions from the base conditions.…”

Section: Resultsmentioning

confidence: 99%

“…10. Of course, as the casting speed is increased, the shell thickness at the exit of the mold is decreased and the metallurgical length is increased, both of which may negatively influence the operational conditions and favor the formation of particular defects such as inner cracks.…”

Section: Resultsmentioning

confidence: 99%

“…To determine R, the solidifying columnar front was set as a fraction of the solid, fs, of 0.3. 10,11) The following relations were used to G and tf: (10) where w is the length of the mesh ahead of the solidification front and ΔT is the thermal gradient along this length. The results of this evaluation are reported in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Modeling Solidification Microstructures of Steel Round Billets Obtained by Continuous Casting

et al. 2011

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The knowledge of the position of the columnar to equaxial transition (CET) is of paramount importance to evaluate the internal quality of continuous casting (CC) products. One way to control the operational CC conditions with the objective of assuring a given quality level is to develop a numerical program able to calculate the local solidification rate (R), the local thermal gradient (G) and the local time of solidification (tf) and to relate these parameters to the CET by means of a predictive model. In the present investigation, the dendritic morphology and the CET transition of three round billets made of a low carbon steel (0.14%C) and produced by CC are characterized, and a computer model is developed to evaluate the R, G and tf-parameters. Referencing the well-known CET transition model developed by Hunt, a simple prediction equation is thus obtained for the steel under study and it is used to propose guidelines for the optimization of the CC operational parameters.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Modeling Solidification Microstructures of Steel Round Billets Obtained by Continuous Casting

et al. 2011

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“…According to the reports from previous researchers, the maximum solid fraction for the mass feeding (solid moving together with liquid) in the mushy zone is roughly to be 0.29-0.35 [9] for high carbon steel and stainless steel. Accordingly, we can assume that the volume shrinkage in the interdendritic areas could be compensated by the liquid steel from the upper stream with solid fraction smaller than around 0.3.…”

Section: Volume Shrinkage Upon Solidificationmentioning

confidence: 99%

“…The equally spaced drilling metal samples were taken from the bloom longitudinal section at the casing direction, as illustrated in Figure 17. The formula to calculate the segregation index is given in Equation (9).…”

Section: Applicationmentioning

confidence: 99%

A study on quantitative evaluation of soft reduction amount for CC bloom by thermo-mechanical FEM model

Liu

Sun

Zhang

et al. 2016

Metall. Res. Technol.

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-Soft reduction has been proved to be the most promising way to minimize center segregation together with the strand center porosity elimination. The negative pressure driven residual melt flow could be balanced by a reasonable reduction amount to compensate the volume shrinkage in the crater mushy zone. The optimum soft reduction amount to bloom casting for given heavy railway steel has been studied in the paper from the point of view of the volume shrinkage compensation. A solidification analysis model was developed to determine the reduction amount based on the local shrinkage in the final solidification stage. The volume shrinkage in the center inter-dendritic region has been quantitatively calculated through the evaluation to the changing melt density. Another thermo-mechanical coupled FEM model was developed to investigate the bloom deformation behavior upon soft reduction operation. The squeezing effect of the soft reduction on the center mushy zone at various solid fractions was revealed quantitatively as well. The results shown that the theoretical soft reduction amount should decrease from 12.2 mm to 4.0 mm corresponding to the solid fraction from 0.3 to 0.9. A new definition for the calculation of the internal soft reduction efficiency was proposed and compared with the conventional one. The nomogram for the determination of optimum soft reduction has been presented for the bloom casting at various center solid fraction. Accordingly, an optimized soft reduction practice was determined for quality high speed railway steel production with clearly improved strand soundness.

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Influence of Calcium Treatment and Electromagnetic Stirring on Ridging in Dual‐Stabilized Ferritic Stainless Steels

Kodukula

Petäjäjärvi

Savolainen

et al. 2020

steel research int.

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Titanium and niobium are added to ferritic stainless steels (FSS) to enhance their surface and mechanical properties. The use of titanium to obtain FSS sheets that are resistant to ridging due to the formation of equiaxed rather than columnar grains during solidification is well established. However, the use of titanium results in clogging the submerged entry nozzle during casting, causing surface defects in cold‐rolled products and overall production losses. To overcome the clogging problem, calcium treatment is conducted in the ladle furnace to transform inclusions into the liquid state. However, this delays the formation of the TiN inclusions which act as nuclei for the equiaxed grains, thereby increasing the fraction of columnar grains in the slabs and susceptibility to ridging in the final cold‐rolled and annealed product. Herein, the effect of calcium treatment and electromagnetic stirring (EMS) on the equiaxed grain ratio and ridging is studied with industrially produced material. The beneficial effect of EMS on grain structure and ridging is largely lost at high calcium contents, but it can be retained, provided the level of calcium is maintained at a sufficiently low, optimum level.

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Prediction of Equiaxed Crystal Ratio in Continuously Cast Steel Slab by Simplified Columnar-to-Equiaxed Transition Model

Cited by 35 publications

References 22 publications

Modeling Solidification Microstructures of Steel Round Billets Obtained by Continuous Casting

Modeling Solidification Microstructures of Steel Round Billets Obtained by Continuous Casting

A study on quantitative evaluation of soft reduction amount for CC bloom by thermo-mechanical FEM model

Influence of Calcium Treatment and Electromagnetic Stirring on Ridging in Dual‐Stabilized Ferritic Stainless Steels

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