Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet
Abstract
:1. Introduction
2. Experimental Procedures
2.1. Research Object and Analysis Areas
2.2. Characterization of Segregation Degree
2.3. Determination of CET Position
2.4. Statistical Correlation
3. Results and Discussion
3.1. Quantitative Correlation between Solidification Structure and Central Segregation
3.1.1. Fluctuation Correlation
3.1.2. Hysteretic Correlation
3.2. Effect of Casting Speed on the Solidification Structure Fluctuation
3.3. Formation Mechanism and Control Strategy of Central Segregation
4. Conclusions
- (1)
- During the CC process, the casting speed will influence the uniformity of the CET position by affecting the fluid flow in the billet. Under lower casting speed, the velocity gradient of molten steel along the casting direction is larger, and the flow is unstable. In this case, the distribution of the dendrites transported by the fluid flow will be also unstable, leading to the more serious fluctuation of the CET position. Under higher casting speed, the velocity gradient is smaller, thus the dendrite distribution driven by the liquid flow is more uniform, leading to a more stable distribution of CET position.
- (2)
- The formation mechanism of central segregation along the casting direction obtained from this research includes two aspects. First, during the CC process, solute elements are enriched at the solid–liquid interface and distributed in the equiaxed zone after CET. At this time, the fluctuation of the equiaxed crystal zone width will affect the distribution of the enriched solute in the billet and cause the fluctuation of the central segregation. Second, at the end of solidification, there is a pumping effect from the endpoint of solidification to the hysteretic solute-enriched liquid phase and finally forms the central V-shaped segregation in the central area.
- (3)
- During the CC process, the equiaxed crystal zone width or columnar crystal length should be kept stable to improve the quality uniformity. At the same time, the central segregation is mainly affected by the equiaxed crystal zone width at the hysteretic position. Thus, control measures applied before the equiaxed crystal zone is completely formed will be meaningful. Combined with the more stable solidification structure, the V-shaped segregation defect on the vertical section of the billet can be reduced.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Sample | Superheat, °C | Casting Speed, m/min | Specific Water Amount, L/kg |
---|---|---|---|
No. 1 | 42 | 1.8 | 0.68 |
No. 2 | 40 | 2.1 | 0.68 |
Billet No. 1 | Billet No. 2 | ||||
---|---|---|---|---|---|
Hyteresis Numbers | Pearson Correlation Coefficient | Significance Level α | Hyteresis Numbers | Pearson Correlation Coefficient | Significace Level α |
0 | −0.068 | 0.803 | 0 | −0.199 | 0.460 |
1 | −0.319 | 0.247 | 1 | −0.190 | 0.497 |
2 | −0.485 | 0.079 | 2 | −0.495 | 0.072 |
3 | −0.458 | 0.116 | 3 | 0.181 | 0.555 |
4 | −0.220 | 0.492 | 4 | 0.254 | 0.425 |
5 | 0.219 | 0.518 | 5 | 0.175 | 0.607 |
6 | 0.592 | 0.071 | 6 | 0.540 | 0.107 |
7 | 0.673 | 0.047 | 7 | −0.257 | 0.505 |
8 | 0.619 | 0.102 | 8 | 0.443 | 0.271 |
Sample | Average Central Segregation Area Ratio, % | Average Equiaxed Crystal Zone Width, mm |
---|---|---|
No. 1 | 35.11 | 96.83 |
No. 2 | 44.50 | 105.88 |
Billet No. 1 | Billet No. 2 | ||
---|---|---|---|
Average hysteretic angle, ° | 89.67 | Average hysteretic angle, ° | 103.90 |
Average V-shaped segregation angle, ° | 94.33 | Average V-shaped segregation angle, ° | 102.67 |
Relative error, % | 4.95 | Relative error, % | 1.20 |
Characteristics Parameters | Billet No. 1 | Billet No. 2 | |
---|---|---|---|
Casting speed, m/min | 1.8 | 2.1 | |
Variation coefficient of central segregation area ratio | 0.1599 | 0.0772 | |
Variation coefficient of columnar crystal length | Inner arc side | 0.1192 | 0.0701 |
Outer arc side | 0.1206 | 0.0493 | |
Average columnar crystal length/mm | Inner arc side | 38.75 | 36.46 |
Outer arc side | 30.10 | 25.71 |
Parameters | Values |
---|---|
Model Length, m | 0.9 |
Model Width, m | 0.16 |
Submerged Depth, m | 0.11 |
Density, kg/m3 | 7020 |
Viscosity, Pa × s | 0.0067 |
Samples | Velocity Discrepancy, m/s | Distance Corresponding to Velocity Discrepancy, m | Velocity Gradient, s−1 |
---|---|---|---|
Billet No. 1 | 0.418 | 0.567 | 0.737 |
Billet No. 2 | 0.520 | 0.790 | 0.658 |
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Guo, D.; Hou, Z.; Peng, Z.; Liu, Q.; Cao, J. Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet. Metals 2021, 11, 452. https://doi.org/10.3390/met11030452
Guo D, Hou Z, Peng Z, Liu Q, Cao J. Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet. Metals. 2021; 11(3):452. https://doi.org/10.3390/met11030452
Chicago/Turabian StyleGuo, Dongwei, Zibing Hou, Zhiqiang Peng, Qian Liu, and Jianghai Cao. 2021. "Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet" Metals 11, no. 3: 452. https://doi.org/10.3390/met11030452