On Continuous Casting Modeling (5) - Strand Behavior
Strand Behavior
The structure and integrity of the cast product are strongly influenced by the thermo-mechanical environment created by the strand cooling and containment systems. Strand practices and designs affect productivity (casting speed limits, metallurgical length, machine availability, product
dispatch), structure (solidification, columnar to equiaxed transition, cooling rates) and quality (cracking, porosity, segregation, bulging)
Examples of how mathematical modeling has contributed to caster strand
performance are showed below.
Controllable Parameters
Strand Practices and Machine Designs
Cooling systems; hydraulic,
air/mist; control zones
Secondary cooling patterns; temperature profiles
Machine design; radius, length, bending/unbending
Containment; roll diameters, roll spacings
Roll gap profile/taper
Machine alignment
Electromagnetic stirring
Soft reduction
Casting speed
Superheat
Torch cutter; slitting
Modeling Contributions
Solidification and heat transfer; surface and internal temperature
fields, shell thickness; fraction solid; metallurgical length
Spray heat transfer coefficients (by inverse calculation)
Strand bulging between rolls; bulging over several rolls;
Strains in the solidifying shell; squeezing and bulging effects of roll
misalignment/bending
Interdendritic segregation; spot-like segregation
Kinetics of nucleation, erosion, columnar/equiaxed growth
Fluid motion in residual liquid
Application Benefits
Diagnostics; location of source of defects and cracks; S-print
interpretation
Secondary cooling control
Crater end point control; location and design of soft reduction units
and F-EMS
Cooling patterns for crack sensitive grades
Optimized reheat furnace times
Stop and slow cast practices
Reduced roll deflections and bearing loads
Reduced subsolidus cracking
Roll spacing design; narrow face containment
Machine maintenance standards
Unbending roll designs[4o]; reduced cracking
Guidelines for steelmaking chemistry
Guidelines for control of cast structures; superheat, speed, cooling
intensity stirring
Designs of final EMS
Standard practices for product quality; reduced inspection and
conditioning; hot despatch; computer-based quality tracking
References
[1] J.K. Brimacombe and A.W.Cramb: Steelmaking, casting and modelling.
Proc. 10th PTD Conf., ISS, Toronto, April 1992
[246] ASM: Modeling in Welding, Hot Deformation and Casting. 1997. ISBN
0-87170-616-4. Ed. By L. Kalsson.
[247] J. Herbertson and P. Austin: The Application of Mathematical Models for
Optimisation of Continuous Casting. Modeling of Casting, Welding and Advanced Solidification Processes - VI. Proceedings. TMS 1993. ISBN 0-87339-209-4.
