J. Bentsman, B.G. Thomas, B. Petrus, X. Zhou, V. Natarajan, and R. O'Malley

National Science Foundation CMMI 09-00138, Continuous Casting Consortium

National Science Foundation Support

CMMI 09-00138
8/1/2009 to 7/31/2012
NSF Program Director: Suhada Jayasuriya, (703) 292-7014
NSF Grants Official: Andrea R. Kline, (703) 292-4820

Industry Support and Partnerships

Nucor Steel, Decatur, Alabama

Nucor Steel is the GOALI Industry partner of this project. They have committed plant personnel and resources to conduct substantial research and control model implementation work at their plant, committing resources of at least $100,000 to this project.

Cinvestav

Cinvestav has covered the costs of the laboratory experiments, using funds from other grants from the Mexican government and the Mexican steel industry, who are also interested in this work.

Continuous Casting Consortium

The Continuous Casting Consortium provided partial matching funds to the project.

Delavan Spraying Technologies and ArcellorMittal USA at Riverdale

Both of these companies covered the costs of putting new nozzles and state-of-the-art optical pyrometers into service, and oversaw running of the other plant trials.

Project Summary

Background

Continuous casting produces 96% of steel in the U.S. In the previous work, using a conceptually novel spatiotemporal software sensor of the shell temperature and thickness in the spray zone based on a nonlinear complex casting model, the PIs developed the first closed-loop spray cooling control system for thin-slab continuous casting. This system, CONONLINE, is currently operating in real time in shadow mode at Nucor Steel in Decatur, Alabama. Moving it to production would permit Nucor to change the current heuristic spray cooling control practice to the one based on surface temperature setpoints directly linked to product quality. However, this system has been found to have a number of fundamental shortcomings. The first is inadequate control setting. The system has been designed to satisfy the surface temperature tracking objective. One of the key insights of the previous research is that the latter, being essentially a 1D surface-based strategy, accounts mostly for the surface cracks and fundamentally lacks the capability to target two central problems: internal cracks and whale formation. The second is nonuniform quality of the temperature estimates throughout the spray zone. Measurement of the mold heat removal rate provides accurate surface temperature estimate only at the mold exit. In the rest of the spray zone, the observer has no measurement–based update, accumulating the observation error with the increasing distance from the mold exit. The third is insufficient model accuracy. The phenomena governing heat transfer are complex, involving water-air-mist interaction, droplet formation, impact patterns, multiphase fluid flow, film boiling, and transient hysteretic effects, not yet investigated in this system. To address the problems described above, this work proposes the paradigm shift in the continuous casting control: a spray cooling control for the simultaneous whale and crack prevention.




Objectives

It is proposed to attain this paradigm shift by pursuing the following objectives:

1) to create a methodology for the design of the closed-loop controllers capable of tracking and disturbance rejection in parabolic systems with moving boundaries; on its basis design and prove in an industrial setting the closed-loop spray cooling control system that attains the 2D strand cross-section temperature profile tracking objective under disturbances and model uncertainty.

2) to create a methodology for hybrid observer design capable of significantly reducing the temperature estimate nonuniformity throughout the spray zone by integrating the software model-based predictions with the online spray zone temperature measurements from the state-of-the-art optical pyrometers to enforce the discrete-continuous observation of the 2D strand cross-section temperature profile.

3) to gain new insights into fundamental heat transfer behavior during spray cooling by integrating results from new laboratory measurements targeted plant experiments, production data, and model predictions. Through careful analysis of system parameters and their update validation at multiple levels, parlay these insights into process model upgrades to dramatically increase model prediction accuracy.

Scientific Contributions and Intellectual Merit

An intellectual merit of this work is in making a dramatic departure from the current spray practice by targeting a closed-loop spray cooling control for the simultaneous whale and crack prevention, aiming at creation of the hybrid controller and observer design methodologies capable of attaining the new objective, proving the resulting system in an industrial setting, and fundamentally enhancing control-oriented analytical and computational models of the thin-slab casting process through deeper investigation of the spray cooling physics.

Broader Impact

The present study will exploit and strengthen the existing active collaboration between the University of Illinois (modeling and control), CINVESTAV (spray cooling laboratory measurements), Delavan Spray Technologies (nozzle and pyrometer design), and several key steel manufacturers with industry-wide impact (plant trial runs). In addition to training students for successful careers in applying models, control design tools, and plant experiments to solve problems of practical industrial importance, this research will make specific contributions to benefit steel production in this country. This has tremendous potential benefits for economic viability of the steel industry (from yield loss savings and increased market share, due to fewer defects and lower cost), energy savings (through yield savings and lower reheating costs), and safety (from improved steel quality, and fewer breakouts and whale-defects). In addition, improved understanding of the heat transfer and better model-based control algorithms that can incorporate a variety of sensor types will broadly benefit other manufacturing processes as well.

Publications

Petrus, B., K. Zheng, X. Zhou, B.G. Thomas, and J. Bentsman, “Real-Time Model-Based Spray-Cooling
Control System for Steel Continuous Casting”, Metallurgical and Materials Transactions B, Vol. 42B:2, 87-
103, 2011. http://dx.doi.org/10.1007/s11663-010-9452-7. Click here for a PDF version (1.32 MB)

Petrus, B., J. Bentsman, and B.G. Thomas, "Feedback control of the two-phase Stefan problem, with an
application to the continuous casting of steel," Proceedings of the 49th IEEE Conference on Decision and
Control, pp. 1731-1736, Atlanta, GA, USA, December 15-17, 2010.

Hernández, C.A., X. Zhou, J.R. Guajardo, A.H. Castillejos, F.A. Acosta, and B.G. Thomas, A Novel Steady-
State Technique for Measuring the Heat Extracted by Secondary Cooling Sprays, ”, AISTech 2010,
Pittsburgh, PA, May 3-6, 2010, Assoc. Iron Steel Technology, Warrendale, PA, 81-92, 2010. Click here for a PDF version (2.88 MB)

Xu, K., B.G. Thomas, and R.J. O’Malley, “Equilibrium Model of Precipitation in Microalloyed Steels,
Metallurgical and Materials Transactions A, Vol. 42A, Feb., 2011, pp. 524-539

V. Natarajan and J. Bentsman, “Robust rejection of sinusoids in stable nonlinearly perturbed unmodelled linear systems: theory and application to servo,” Proceedings of the American Control Conference, San Francisco, 2011.

V. Natarajan and J. Bentsman, “Robust periodic reference tracking by stable uncertain infinite-dimensional linear systems,” Proceedings of the American Control Conference, San Francisco, 2011.

Petrus, B., K. Zheng, X. Zhou, B.G. Thomas, J. Bentsman, and R.J. O'Malley, "Implementation of a Real-
Time Model-Based Spray-Cooling Control System for Steel Continuous Casting," in Sensors, Sampling,
and Simulation for Process Control, B.G. Thomas, J.A. Yurko and L. Zhang, eds., John Wiley & Sons,
Hoboken, New Jersey, (TMS Annual Meeting Symposium, San Diego, CA, Feb. 27- Mar. 3, 2011), 2011,
77-84. Click here for a PDF version (475 KB)

Thomas, B.G., J.A. Yurko, and L. Zhang, Sensors, Sampling, and Simulation for Process Control, (Proceedings of TMS Annual Meeting Symposium, held in San Diego, CA, Feb. 27-Mar. 3, 2011), John Wiley & Sons, Hoboken, New Jersey, 166 pages, 2011.

Bentsman, J., B.G. Thomas, B. Petrus, X. Zhou, V. Natarajan, and R.J. O’Malley “Hybrid Control of
Continuous Casting for Whale and Crack Prevention and Resonance Control in Mold Oscillation
System,” Proceedings of 2011 NSF CMMI Engineering Research and Innovation Conference, Atlanta, GE,
Jan. 4-7, 2011, Grant # DMI-0900138, 22p. Click here for a PDF version (1.65 MB)

X. Zhou, "Heat Transfer During Spray Water Cooling Using Steady Experiments," MS Thesis, University of Illinois, 2009.

H. Jasti, "User-Friendly Interface Design and Development for Continuous-Casting Model CON1D," MS Thesis, University of Illinois, 2010

Thomas, B.G., J. Bentsman, and K. Zheng, “Spray Cooling Control System for Continuous Casting of
Metal“, U.S. Provisional Patent Application No. US60/928,043, June 13, 2007; U.S. Non-provisional
patent application No. 12/151/582, filed May 7, 2008.