Control and Design of the Steel Continuous Casting Process Based on Advanced Numerical Models
Abstract
:1. Introduction
2. The Process of Steel Continuous Casting as an Object of Numerical Modelling
- Turbulent flow of liquid steel through a complex geometry area—a submerged entry nozzle (SEN) or a shroud—caused by convection
- Heat transfer within the liquid steel area
- Heat transfer in the mould between the forming shell and the mould wall
- Heat flow through the layer of solid and liquid slag
- Formation of thermal stress
- Shrinkage of the solidifying shell, related to transitions occurring during the steel solidification process
- Thermal effect accompanying the solidification phenomenon
- Mechanical impact of the mould walls on the solidifying strand
- The process of an air gap formation between the mould wall and the solidifying strand
- The formation of crystals within the solidification zone accompanied by element segregation effects
- Formation of surface defects
- Heat transfer within the liquid core area (conduction and convection)
- Heat conduction in the solidified shell layer
- Thermal effect accompanying the solidification phenomenon
- Multi-stage heat transfer resulting from the strand cooling by the nozzle system, related to the number of spray zones and the applied cooling type
- Shrinkage of the solidifying strand, related to transitions occurring during the steel solidification process
- Formation of individual solidification zones (zone of dendritic crystals and zone of equiaxed crystals)
- Formation of stress related to the contact of rolls with the strand, and the possibility of bulging between the continuous casting machine rolls
3. Development of the Numerical Model for the Continuous Casting of Steel Process
3.1. Strategy of the Boundary Conditions Calculation
- The first-type boundary condition, when the surface temperature at the edge of the domain is specified.
- The second-type boundary condition, when the heat flux density transferred to the environment at the edge of the domain is specified.
- The third-type boundary condition, when the method of heat transfer at the edge of the domain expressed numerically by the heat transfer coefficient, and the ambient temperature are determined.
- The mould outer side
- The contact of the solidifying strand face with the inner side of the mould
- The surface of the liquid steel meniscus
- The secondary cooling zone (divided into a set number of spray zones)
3.2. Material-Related Parameters
3.3. Inverse Modeling
4. Sensitivity Analysis
- What factors cause the biggest changes in the metallurgical length of the strand and the shell thickness under the mould?
- Are there any factors whose influence on the above mentioned parameters is negligible?
- Are there any interactions, which enhance or suppress the variability caused by individual factors?
- Technological process parameters: strand casting speed and cooling intensity in individual zones of the continuous casting machine.
- Parameters characteristic of the properties of the material cast:
- chemical composition of the steel cast, (%)
- initial temperature of the steel cast (in the tundish), (K)
- liquidus temperature of the steel cast, (K)
- solidus temperature of the steel cast, (K)
- viscosity of the steel cast as a function of temperature, (mP)
- specific heat of the steel cast as a function of temperature, (J·kg−1·K−1)
- melting heat of the steel, (J·kg−1)
- steel density as a function of temperature (kg·m−3)
- thermal conductivity, (W·m−1·K−1)
- HTC in the mould
- HTC in the secondary cooling zone
- Steel specific heat as a function of temperature cp(T)
5. Evaluation of Possibilities for Using Numerical Models in Order to Design or Modify the Existing Technology
5.1. Development of the Cooling Program for a New Steel Grade
- The simulation of the casting process for various strand withdrawal speeds, taking into account the technical parameters of the continuous casting machine without changing the values of the cooling parameters.
- The assessment of the impact of a speed change on changes of basic parameters of the strand cast i.e., the metallurgical length, shell thickness under the mould, and the value of the strand surface temperature at the reference points.
- The estimation of the necessary change in values of heat transfer coefficients in the individual cooling zones of the continuous casting machine allowing the assumed metallurgical length and shell thickness under the mould to be achieved for the changed casting speed.
- The conversion of new heat transfer coefficients to water consumption in individual secondary cooling zones.
- The experimental check of the correctness of the calculated temperature of the strand surface at the selected reference points.
5.2. Method of Selection of Cooling Parameters
6. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
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Number of the HTC Model | Type of the HTC Model | Average or Maximum Value of the HTC [W·m−2·K−1] |
---|---|---|
1 | The average value of the HTC | HTC = 1200 |
2 | The average value of the HTC | HTC = 1300 |
3 | The average value of the HTC | HTC = 1500 |
4 | Two values of the HTC | HTC = 1163 for z ≤ 0.6 m HTC = 1395.6 for z > 0.6 m |
5 | A linear values of the HTC | HTC = 800–2000 |
6 | A linear values of the HTC | HTC = 600–1500 |
7 | The values of the HTC as a function | HTCmax = 1300 |
8 | The values of the HTC as a function | HTCmax = 2500 |
9 | The values of the HTC as a function | HTCmax = 2000 |
10 | The values of the HTC as a function | HTCmax = 1300 |
11 | The values of the HTC as a function | HTCmax = 3097 |
12 | The values of the HTC as a function | HTCmax = 1600 |
Number of the HTC Model | Thickness of the Shell after Leaving the Mould, cm | Temperature, °C |
---|---|---|
1 | 2 | 836 |
2 | 2.3 | 812 |
3 | 2.75 | 772 |
4 | 2.27 | 833 |
5 | 2.38 | 900 |
6 | 1.94 | 956 |
7 | 1.98 | 976 |
8 | 1.92 | 1050 |
9 | 1.86 | 1090 |
10 | 1.82 | 1099 |
11 | 2.51 | 874 |
12 | 2.52 | 938 |
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Miłkowska-Piszczek, K.; Falkus, J. Control and Design of the Steel Continuous Casting Process Based on Advanced Numerical Models. Metals 2018, 8, 591. https://doi.org/10.3390/met8080591
Miłkowska-Piszczek K, Falkus J. Control and Design of the Steel Continuous Casting Process Based on Advanced Numerical Models. Metals. 2018; 8(8):591. https://doi.org/10.3390/met8080591
Chicago/Turabian StyleMiłkowska-Piszczek, Katarzyna, and Jan Falkus. 2018. "Control and Design of the Steel Continuous Casting Process Based on Advanced Numerical Models" Metals 8, no. 8: 591. https://doi.org/10.3390/met8080591