Using a Two-Phase Columnar Solidification Model to Study the Principle of Mechanical Soft Reduction in Slab Casting
- PDF / 1,395,057 Bytes
- 20 Pages / 593.972 x 792 pts Page_size
- 89 Downloads / 185 Views
CHANICAL soft reduction (MSR) has been shown in industrial practice to reduce centerline/axial segregation in slab and bloom castings[1–10]; however, control of the MSR process remains a trial and error process in plant operations. Empirical knowledge (Figure 1) has shown that satisfactory MSR efficiency can be achieved when MSR is positioned correctly on the strand and carried out with the appropriate reduction intensity. The MSR position is usually determined in terms of the solid fraction of the strand core (i.e., the casting centerline)—the solid fraction at the start cent cent fs; Start and at the end position fs; End of MSR. The reduction intensity is usually defined by the reduction rate, which is the reduction amount ðeÞ divided by the length of the reduction segment ðlSR Þ. When the MSR is
MENGHUAI WU, Associate Professor and Chair for Simulation and Modeling of Metallurgical Processes, Christian Doppler Laboratory for Advanced Process Simulation of Solidification and Melting, University of Leoben, A-8700 Leoben, Austria. Contact e-mail: [email protected] JOSEF DOMITNER, PhD Student, and ANDREAS LUDWIG, Professor and Chair for Simulation and Modeling of Metallurgical Processes, are with the Christian Doppler Laboratory for Multiphase Modeling of Metallurgical Processes, University of Leoben. Manuscript submitted April 5, 2011. Article published online October 19, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
performed too early, too late, or too intensely, the risk of crack formation and growth increases. According to Thome and Karste,[3] the optimum MSR is defined by the minimum intensity of reduction that is necessary to compensate shrinkage during solidification without creating internal cracks. Implementation of the aforementioned empirical knowledge in industry process is not straightforward. However, depending on the casting format and steel grade, the suggested MSR position can differ significantly h i hfrom icase to case (e.g., between 0.2 [11,12] cent fs; Start and 0.9 fcent s; End for higher carbon steel, [13,14] between 0.2 and 0.7 for low carbon steel, or between 0.37 and 0.51 for a medium steel).[15] Optimum reduction rates achieved in each case were also surprisingly different (e.g., between 1.8 and 6.6 mm/m[11,14] or 0.72 and 4.7 mm/m[11,15]). Given the discrepancy in optimum MSR position and reduction rate, future investigation into the MSR process is warranted to understand and improve the practical implementation of the process in industry. Use of computational models to investigate macrosegregation in slab casting caused by bulging (mechanical shell deformation) was pioneered by Miyazawa and Schwerdtfeger in the early 1980s.[16] Despite the model simplicity, the limited computational resources available at that time, when only a small section of slab between one roll pair could be simulated, the model was the first to reveal the main mechanism of centerline macrosegregation in the slab casting. Although solidification VOLUME 43A, MARCH 2012—945
II.
MODEL DESCRIPTIONS
A. Colu
Data Loading...
