(NSF) Study of Transient Flow Structures in the Continuous Casting of Steel (1998-2001)

B.G. Thomas, S.P Vanka, L. Zhang, S. Sivaramakrishnan, S. Subramanian, H. Bai, T. Shi, Q. Yuan, B. Zhao, D. Creech, P. Dauby, M. Assar, R. O'Malley

National Science Foundation DMI 98-00274, Continuous Casting Consortium

National Science Foundation Support:

DMI 98-00274
Jan. 1998 - Jan. 2001

Industry Support

LTV Steel Corporation

As a member of the Continuous Casting Consortium, LTV contributed an annual fee towards research in the area of mathematical modelling of continuous casting of steel. A Part of the CCC membership fees is used as industrial matching funds for this NSF project. LTV also provided access and personnel support to the PIV and water modeling facilities at Cleveland, OH research center. LTV researchers also provided valuable industrial perspective and research needs in this area.

AK Steel Company

AK Steel, as a member of the Continuous Casting Consortium, has provided funding, advice on the project, access to lab facilities in their research lab in Middletown, OH, provided plant data, collaborated on the project (resulting in coauthored publications), and participated in researcher exchanges, both by sending researchers for visits to UIUC and by accepting students to work in their lab for short times.

The following companies provided Financial Support (CCC membership), In-kind Support, Facilities (water models and plant measurements), and Research direction:

Plant observations have found that many serious quality problems are directly associated with the flow pattern in the mold. Previous studies have generated understanding mainly through numerical simulations using time-averaged turbulence models. However, many problems are intermittent and the essential transient nature of the flow may be important to their formation. To obtain further understanding of these important transient turbulence processes, this project developed and applied computational models to directly compute the evolution and dynamics of the large-scale turbulence structures. Accurate numerical schemes and parallel computers are used to solve the governing fluid flow equations using a Large Eddy Simulation (LES) approach. The insights into how costly defects form are being used to find improvements in design and operating conditions in continuous casting that can avoid them.

Summary of Activities Click here for full Activities PDF (173KB)

Activities on this project began with development of computational models of steady and transient models of flow in the continuous casting nozzle and mold. The relative accuracy of these models is investigated through extensive comparison with laboratory measurements in water models, including particle image velocimetry, and with plant measurements conducted on continuous casting machines at the supporting steel companies. Next, extensive steady simulations are conducted to characterize multiphase fluid flow through the nozzle as a function of nozzle geometry and casting conditions. With the help of fundamental studies of bubble formation, the nozzle model is further applied to optimize argon injection to suggest guidelines to avoid nozzle clogging and to measure it using a "clogging index". Fully transient models of flow in the caster using Large Eddy Simulation are developed, evaluated, and applied to simulate flow in the mold. Then, the accuracy and relative advantages of the different models of fluid flow are compared with flow measurements in both water models and operating casters. Next, the models are applied to simulate three different phenomena associated with fluid flow in the mold: inclusion transport, heat transfer, and multiphase flow due to argon bubble injection. Guidelines are developed to predict optimal gas flow rates that should assist in designing better mold flow patterns to improve steel quality.

In addition to working on the research projects (and communicating the results through publishing book chapters, journal articles, conference presentations, online electronic articles and animations on two websites), semi-annual day-long meetings were held with industry representatives from the steel-related companies in the Continuous Casting Consortium (usually about 10 researchers from 7 different companies) to discuss the results of the individual projects, and to obtain feedback to benefit the students. Finally, the results from this work are incorporated into the short course to the steel industry (Brimacombe Continuous Casting Course, in Vancouver, Canada) which is presented annually by a team of 5 instructors including the PI of this project.

Summary of Findings Click here for full Findings text PDF (112 KB)
Click here for full Findings Figures PDF (2.23 MB)

Several different computational models of turbulent fluid flow and heat transfer have been developed to simulate flow phenomena in the nozzle and mold regions of the continuous casting of steel slabs. The models have been calibrated, validated, and tested quantitatively through comparisons with water model experiments, steel plant trials, and metallographic measurements at LTV Steel and several other steel companies who are cosponsoring this research. Next, this work has revealed many specific insights into multiphase flow through nozzles, which are important to designing nozzle geometry to avoid clogging andflow-related problems in the mold, which may generate defects in thefinal steel product. Contributions in three different areas include:

1) characterizing flow conditions exiting a typical slide-gate nozzleas a function of casting conditions,

2) developing a clogging index toreveal when clogging has occurred and

3) providing guidelines tooptimize argon injection to avoid clogging due to air aspiration in
the nozzle.

Through extensive comparisons of steady and transient models,particle-image velocimetry measurements in water models, and plantmeasurements, all taken under similar conditions, this work hasquantified how simple K-e flow models can reasonably predicttime-averaged multiphase flow of molten steel under the conditions ofinterest. Provided that the inlet conditions are accurate, large-eddysimulations of transient flow can further reveal important transient flow structures and accurately predict time-dependent signals, such as RMS velocity, at least for single phase flow. Further application of this model to inclusion transport has revealed its ability to matchthe distribution and flotation removal of inclusion particles in thetransient flow field with water model measurements, both qualitatively and quantitatively. In addition to the inlet velocity and direction the turbulence and swirl at the inlet ports has been shown to be very important to both the fluid flow and inclusion motion.

Secondly, transient LES simulations of impinging jets are performed and applied to predict heat transfer to the surface. This is important for theprediction of shell thinning and breakouts. The angle of jetimpingement against the narrow face also appears to have an important influence on the fraction of inclusion particles transported down deepinto the caster, where they may become entrapped to form defects.

Thirdly, steady, multiphase flow computations are compared with flow patterns observed in both a 0.4-scale water model and an operatingsteel caster with argon gas injection. For the same conditions, the water model and steel caster produced very different flow behavior.The computational model was able to match the measured flow patterns in both systems. The model is extended to predict the flow pattern as a function of operating conditions, which can be used as guidelines tooptimize gas injection practice in the real process.

In addition to its contributions to the continuous casting of steel, this work has demonstrated the potential of computational flow modeling to match real industrial processes. Moreover, computationalmodels are shown to be as accurate or better than water models, especially when complex related phenomena such as particle motion and multiphase flow are involved. The models will be further improved and applied in the current NSF project.

NSF Publications Describing This Work

Thomas, B.G. and S.P. Vanka, “Study of Transient Flow Structures in the Continuous Casting of Steel,” Proceedings of the 1999 NSF Design and Manufacturing Grantees Conference, Long Beach, CA, Jan. 1999. Click here for a PDF version (198KB)

Thomas, B.G. and S.P. Vanka, “Study of Transient Flow Structures in the Continuous Casting of Steel,”
Proceedings of the 2000 NSF Design and Manufacturing Grantees Conference, Vancouver, Canada, Jan. 3-6,
2000; NSF, Washington, D.C., 14 pp., 2000. Click here for a PDF version (638 KB)

Vanka, S.P. and B.G. Thomas, “Study of Transient Flow Structures in the Continuous Casting of Steel,”
Proceedings of the NSF Design and Manufacturing Grantees Conference, Tampa, FL, Jan. 7-10, 2001; NSF,
Washington, D.C., 14 pp., 2001. Click here for a PDF version (498 KB)

Miki, Y. and B.G. Thomas, “Modeling of Inclusion Removal in a Tundish,” Metallurgical and Materials
Transactions B, 30B:4, 639-654, 1999. Click here for a PDF version (944 KB)

Stone, D.T. and B.G. Thomas, “Measurement and Modeling of Heat Transfer Across Interfacial Mold
Flux Layers,” Canadian Metallurgical Quarterly, 38:5, 363-375, 1999. [Best Paper Award, 2000, Canadian
Institute of Mining and Metallurgy]. Click here for a PDF version (1.14 MB)

Bai, H. and B.G. Thomas, “Turbulent Flow of Liquid Steel and Argon Bubbles in Slide-Gate Tundish Nozzles, Part I, Model Development and Validation,” Metallurgical and Materials Transactions B, 32B:2, 253-267, 2001. Click here for a PDF version (1.26 MB)

Bai, H. and B.G. Thomas, “Turbulent Flow of Liquid Steel and Argon Bubbles in Slide-Gate Tundish Nozzles, Part II, Effect of Operation Conditions and Nozzle Design,” Metallurgical and Materials Transactions B, 32B:2, 269-284, 2001. Click here for a PDF version (1.94 MB)

Bai, H. and B.G. Thomas, “Effects of Clogging, Argon Injection, and Continuous Casting Conditions on Flow and Air Aspiration in Submerged Entry Nozzles,” Metallurgical and Materials Transactions B, 32B:4, 707-722, 2001. Click here for a PDF version (990 KB)

Thomas, B.G., Q. Yuan, S. Sivaramakrishnan, T. Shi, S.P. Vanka, and M.B. Assar, “Comparison of Four Methods to Evaluate Fluid Velocities in a Continuous Slab Casting Mold,” Iron Steel Institute Japan (ISIJ) International, 41:10, 1262-1271, 2001. Click here for a PDF version (776 KB)

Thomas, B.G. and L. Zhang, “Review: Mathematical Modeling of Fluid Flow in Continuous Casting,” Iron Steel Institute Japan (ISIJ) International, 41:10, 1181-1193, 2001. Click here for a PDF version (1.33 MB)

Bai, H. and B.G. Thomas, “Bubble Formation during Horizontal Gas Injection into Downward-Flowing
Liquid,” Metallurgical and Materials Transactions B, 32B:6, 1143-1159, 2001. Click here for a PDF version (784 KB)

Yuan, Q., S. Sivaramakrishnan, S.P. Vanka, and B.G. Thomas, “Computational and Experimental Study
of Turbulent Flow in a 0.4-Scale Water Model of a Continuous Steel Caster,” Metallurgical and Materials
Transactions B, 35B:5, 967-982, 2004. Click here for a PDF version (2.23 MB)

Thomas, B.G. “Casting Process Simulation and Visualization: A JOM-e Perspective,” Journal of Metals, 54:1, 20-21, Jan. 2002; also in (http://www.tms.org/pubs/journals/JOM/0201/Thomas/Thomas-0201-commentary.html). Click here for a PDF version (256 KB)

Thomas, B.G., Q. Yuan, S. Sivaramakrishnan, and S.P. Vanka, "Transient Fluid Flow in the Continuous Steel-slab Casting Mold", JOM-e, (Journal of Metals - electronic edition), 54:1, Jan. 2002, www.tms.org/jom.html (http://www.tms.org/pubs/journals/JOM/0201/Thomas/Thomas-0201.html). Click here for a PDF version (997 KB)

Thomas, B.G. and S.P. Vanka, “Study of Transient Flow Structures in the Continuous Casting of Steel,” Proceedings of the 1999 NSF Design and Manufacturing Grantees Conference, Long Beach, CA, Jan. 1999. Click here for a PDF version (199 KB)

Creech, D. and B.G. Thomas, “3-D Turbulent Multiphase Modeling of Molten Steel Flow and Heat Transfer in a Continuous Slab Caster,” CFX User Meeting, Wilmington, DE, Oct. 1, 1998. Click here for a PDF version (197 KB)

Bai, H., "Argon Bubble Behavior in Tundish Nozzles During Continuous Casting of Steel Slabs (Summary of work to April 1999)" , bibl. Continuous Casting Consortium Report, University of Illinois, August 19, 1999, (1999). Report

Subramanian, S., B.G. Thomas, and S.P. Vanka, “Heat Transfer from an Impinging Steel Jet Using LESModels,” Continuous Casting Consortium Report, UIUC, Aug. 19, 1999.

Sivaramakrishnan, S., B.G. Thomas, and S.P. Vanka, “Investigation of Transient Turbulent Flow in a Water Model using LES Calculations and PIV Experiments,” Continuous Casting Consortium Report, UIUC, Aug. 5, 1999.

Thomas, B.G., "Mathematical Models of Continuous Casting of Steel Slabs" , bibl. Annual Report to Continuous Casting Consortium, University of Illinois, August 19, 1999, (1999). Report

Thomas, B.G., "Mathematical Models of Continuous Casting of Steel Slabs" , bibl. Annual Report to Continuous Casting Consortium, University of Illinois, August 21, 1998, (1998). Report

Thomas, B.G. and S.P. Vanka, “Study of Transient Flow Structures in the Continuous Casting of Steel,” Proceedings of the 2000 NSF Design and Manufacturing Grantees Conference, Vancouver, Canada, Jan. 3-6, 2000; NSF, Washington, D.C., 14 pp., 2000. Click here for a PDF version (655 KB)

Sivaramakrishnan, S., B.G. Thomas, and S.P. Vanka, “Large Eddy Simulation of Turbulent Flow in Continuous Casting of Steel,” Materials Processing in the Computer Age III, Nashville, TN, March 12-16, 2000; V. Voller and H. Henein, eds., The Minerals, Metals, and Materials Society Annual Meeting, Nashville, TN, The Minerals, Metals, and Materials Society, Warrendale, PA, 189-198, March 12-16, 2000. Click here for a PDF version (427 KB)

Bai, H. and B.G. Thomas, “Two Phase Flow in Tundish Nozzles during Continuous Casting of Steel,” Materials Processing in the Computer Age III, Nashville, TN, March 12-16, 2000; V. Voller and H. Henein, eds., The Minerals, Metals, and Materials Society Annual Meeting, Nashville, TN, The Minerals, Metals, and Materials Society, Warrendale, PA, 85-99, March 12-16, 2000. Click here for a PDF version (588 KB)

Sivaramakrishnan, S., H. Bai, B.G. Thomas, S.P. Vanka, P. Dauby, and M. Assar, “Transient Flow Structures in Continuous Cast Steel,” Proceedings of the 59th Ironmaking Conference, Pittsburgh, PA, March 26-29, 2000; 59, 541–557, Iron and Steel Society, Warrendale, PA, 2000. Click here for a PDf version (2.15 MB)

Bai, H. and B. G. Thomas, “Effect of Clogging, Argon Injection and Casting Conditions on Flow Rate and Air Aspiration in Submerged Entry Nozzles,” Proceedings of the 59th Ironmaking Conference, Pittsburgh, PA, March 26-29, 2000; 83, 183-197, Iron and Steel Society, Warrendale, PA, 2000. Click here for a PDF version (1.46 MB)

Thomas, B.G., R. O'Malley, T. Shi, Y. Meng, D. Creech, and D. Stone, “Validation of Fluid Flow and Solidification Simulation of a Continuous Thin Slab Caster,” Modeling of Casting, Welding, and Advanced Solidification Processes - IX, Aachen, Germany, Aug. 20-25, 2000; P. Sahm, ed., Shaker Verlag, 769-776, Aachen, Germany, 2000. Click here for a PDF version (293 KB)

Thomas, B.G., “The Importance of Numerical Simulations for Further Improvements of the Continuous Casting Process,” 8th International Continuous Casting Conference, Voest Alpine I., Linz, Austria, 7.1-7.11, June 5–7, 2000. Click here for a PDF version (896 KB)

Thomas, B.G., "Mathematical Models of Continuous Casting of Steel Slabs" , bibl. Annual Report to Continuous Casting Consortium, University of Illinois, September 25, 2000. , (2000). Report

Vanka, S.P. and B.G. Thomas, “Study of Transient Flow Structures in the Continuous Casting of Steel,” Proceedings of the NSF Design and Manufacturing Grantees Conference, Tampa, FL, Jan. 7-10, 2001; NSF, Washington, D.C., 14 pp., 2001. Click here for a PDF version (498 KB)

Thomas, B.G., “Continuous Casting: Complex Models,” The Encyclopedia of Materials: Science and Technology, K. H. J. Buschow, R. Cahn, M. Flemings, B. Ilschner, E. J. Kramer, S. Mahajan, eds. (J. Dantzig, subject ed.), Elsevier Science Ltd., Oxford, United Kingdom, Vol. 2, 1599-1609, 2001 Click here for a PDF version (896 KB)

Thomas, B.G., “Continuous Casting of Steel,” Chapter 15 in Modeling for Casting and Solidification Processing,” O. Yu, ed., Marcel Dekker, New York, NY, 499-540, 2001. Click here for a PDF version (2.55 MB)

Thomas, B.G., “Continuous Casting,” The Encyclopedia of Materials: Science and Technology, K. H. J. Buschow, R. Cahn, M. Flemings, B. Ilschner, E. J. Kramer, and S. Mahajan, eds. (D. Apelian, subject ed.), Elsevier Science Ltd., Oxford, United Kingdom, Vol. 2, 1595-1599, 2001 Click here for a PDF version (96 KB)

Thomas, B.G. “Modeling of Continuous Casting,” Chapter 5 in Making, Shaping and Treating of Steel, 11th Edition, Vol. 5, Casting Volume, A. Cramb, ed., AISE Steel Foundation, Pittsburgh, PA, 5.1-5.24, 2003. Click here for a PDF version (3.62 MB)

Thomas, B.G. and H. Bai, “Tundish Nozzle Clogging–Application of Computational Models,” Proceedings of the 18th Process Technology Conference, Baltimore, MA, March 25-28, 2001, 84, 895-912, Iron and Steel Society, Warrendale, PA, 2001. Click here for a PDF version (1.23 MB)

Yuan, Q., S.P. Vanka, and B.G. Thomas, “Large Eddy Simulations of Turbulent Flow and Inclusion Transport in Continuous Casting of Steel,” Proceedings of 2nd International Symposium on Turbulent and Shear Flow Phenomena, Royal Institute of Technology (KTH), Stockholm, Sweden, 2, 519-524, June 27 - 29, 2001. Click here for a PDF version (1.75 MB)

Yuan, Q., T. Shi, B.G. Thomas, and S.P. Vanka, “Simulation of Fluid Flow in the Continuous Casting of Steel,” Computational Modeling of Materials, Minerals and Metals Processing, Seattle, WA, 2002; Cross, Bailey, and Evans, eds., The Minerals, Metals, and Materials Society, Warrendale, PA, 491-500, 2001. Click here for a PDF version (2.78 MB)

“University-Steel Industry Interaction,” R&D in the Steel Industry, 40th Congreso Latinoamericano de Siderurgia (ILAFA 40 Congress Proceedings), Buenos Aires, Sept. 12-15, 1999, Inst. Argentino de Siderurgia, 1999, pp. 65-67 (translated into Spanish). Click here for a PDF version (19 KB)

“Detailed Simulation of Flow in Continuous Casting of Steel Using K-e, LES, and PIV,” International Symposium on Cutting Edge of Computer Simulation of Solidification and Processes, Osaka, Japan, 113-128, Nov. 14-16, 1999. Click here for a PDF version (868 KB)

“Modeling of the Continuous Casting of Steel: Past, Present and Future,” Dr. J. Keith Brimacombe Lecture, 59th Electric Furnace Conference, Phoenix, AZ, 3-30, 2001, Iron and Steel Society, Warrendale, PA, Nov. 11-14, 2001. Click here for a PDF version (2.21 MB)

Shi, T. and B.G. Thomas, “Argon Injection Optimization in Continuous Slab Casting,” Continuous Casting Consortium Report, University of Illinois, Sept. 2001. Click here for a PDF version (3.25 MB)

Thomas, B.G., "Mathematical Models of Continuous Casting of Steel Slabs" , bibl. Annual Report to Continuous Casting Consortium, University of Illinois, October 18, 2001., (2001). Report

Thomas, B.G. and S.P. Vanka, “Study of Transient Flow Structures in the Continuous Casting of Steel,” Proceedings of the NSF Design, Service, Manufacturing and Industrial Innovation Research Conference, San Juan, Puerto Rico, National Science Foundation, Washington, D.C., 22 pp., Jan. 7-10, 2002. Click here for a PDF version (1.07 MB)

Rani, S.L. Vanka, S.P., "Two-way Coupling Effects in a Particle-laden Turbulent Pipe Flow" , bibl. The 54th APS/DFD (American Physical Society/Division of Fluid Dynamics) meeting, San Diego, CA, Nov 18-20, 2001, (2001), "Bulletin American Physical Society, DFD 2001, Abstract JA-3"

Luo, G. Vanka, S.P., "Rayleigh-Benard Convection in a Vertical Cylinder Heated from Below with Nonuniform Temperature" , bibl. The 54th APS/DFD (American Physical Society/Division of Fluid Dynamics) meeting, San Diego, CA, Nov 18-20, 2001, (2001), "Bulletin American Physical Society, DFD 2001, Abstract EG-7"

Winkler, C.M. Vanka, S.P., "Turbulent Particle Dispersion in a Square Duct" , bibl. The 54th APS/DFD (American Physical Society/Division of Fluid Dynamics) meeting, San Diego, CA, Nov 18-20, 2001, (2001), "Bulletin American Physical Society, DFD 2001, Abstract EG-7"