Defects and Properties of Cast Metals: Continuous Casting
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Solidification Committee
Program Organizers: Lang Yuan, University of South Carolina; Brian Thomas, Colorado School of Mines; Peter Lee, University College London; Mark Jolly, Cranfield University; Alex Plotkowski, Oak Ridge National Laboratory; Charles Monroe, University of Alabama Tuscaloosa
Wednesday 2:00 PM
February 26, 2020
Room: 17B
Location: San Diego Convention Ctr
Session Chair: Brian Thomas, Colorado School of Mines; Pavel Ramirez Lopez, Swerim
2:00 PM Invited
Advances on Inspection and Numerical Modelling of Surface Defects During Continuous Casting of Steel: Pavel Ramirez Lopez1; 1SWERIM AB
The European Project SUPPORT-CAST was launched to find optimal casting parameters and cooling rates that improve surface quality of continuously cast products based on advanced monitoring in combination with numerical modelling. Inspection is performed by a series of lasers able to withstand temperatures up to 1400°C while scanning as-cast surfaces with high accuracy, continuously monitoring temperature and capturing high resolution images. This enables detection of defects such as depressions, deep oscillation marks and cracks as well as mapping oxide scale and alignment issues. Moreover, complete slabs/billets can be reconstructed from these scans to create virtual replicas of the products. Additionally, advanced numerical models have been developed to predict the influence of flow and heat transfer on solidification and defects formation. This manuscript introduces the latest developments to implement these systems online and how they are complemented with simulations to support decision-making for improving the quality of cast products.
2:30 PM Invited
Multiphase Flow-related Defects in Continuous Casting of Steel Slabs: Seong-Mook Cho1; Mingyi Liang1; Hamed Olia1; Lipsa Das1; Brian Thomas1; 1Colorado School of Mines
Multiphase flow phenomena greatly affect the quality of continuous cast steel. Instability at the interface between the molten steel and surface slag is caused by jet wobbling, resulting in sudden level drops and slag entrapment into the solidifying shell at the meniscus of the continuous casting mold, causing surface defects. In addition, excessive surface velocity can entrain the surface slag into the steel pool. Furthermore, particles such as argon gas bubbles, alumina inclusions and entrained slag can be transported by unoptimized flow and captured into the solidification front deep in the strand, especially into the inside radius of curved strands, leading to internal defects. This work applies three-dimensional computational fluid dynamics modeling using volume of fluid model (VOF), discrete phase model (DPM), and particle capture models, validated with plant measurements, to quantify the above defect formation mechanisms relevant to multiphase flow phenomena in continuous slab casting.
3:00 PM
Influence of Various Cast Defects in Fe-Al-Cr-Zr Intermetallics on the High Temperature Oxidation Behavior: Rene Putz1; Emir Subašić2; Alexander Gußfeld2; Daniela Zander1; 1RWTH Aachen University; 2Access e.V.
Casted Fe-Al type alloys come into consideration as a substitute material for stainless steels and/or nickel-base alloys in corrosive high temperature environments. Iron aluminides are generally characterized with their low density, good wear resistance and outstanding oxidation behavior. Contrary, low ambient ductility and limited strength at high temperatures have both prevented their commercial implementation. Therefore, several alloying concepts are underway for the elimination of the mentioned drawbacks. The high temperature oxidation resistance is a crucial factor for the component’s life time, which is potentially influenced by various cast defects like porosities, agglomerations and surface defects. To understand the influence of cast defects on the oxidation behavior of Fe-Al-Cr-Zr, specimens were exposed to air at 700 °C for multiple hours. Subsequently, the occurred oxidation phenomena were investigated by optical light microscopy (OLM), x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDX).
3:20 PM Break
3:40 PM
Analysis of Solidification and Thermal-mechanical Behaviors in Continuous Casting: John Lawrence1; Matthew Moore1; Xiang Zhou1; Haibo Ma1; Armin Silaen1; Chenn Zhou1; 1Purdue University Northwest
Continuous casting (CC) is the most utilized steel making process today, but knowledge on the many complex phenomena that occur within the process could be gained. Issues such as transient flow patterns and immoderate amounts of stress can result in defects and even breakouts. With the advancement in computational power, computational fluid dynamics (CFD) can provide significant insights into CC. This work will focus on stress occurring in the solidifying shell as it moves through both primary and secondary cooling. Excessive stress on a thinning portion of the shell is the main catalyst in the case of a breakout so it is important to understand its behavior and overall impact. Utilizing the finite element method in Star CCM+, the fluid-solid interaction between the molten steel and shell will be simulated to understand the causes and influences of stress while the shell is continually solidifying.
4:00 PM Cancelled
Numerical Simulation of Macrosegregation Behavior of Billet During Continuous Casting: Yaoguang Li1; Yanhui Sun1; Xuesong Bai1; Ruimei Chen1; Xinxin Lu1; 1University of Science & Technology Beijing
The three-dimensional numerical model, which coupled turbulent flow, solute transport and heat transfer, was developed to investigate the macrosegregation behavior of high carbon steel billet in the process of continuous casting. The outlet of the model was located where at the end point of solidification to examine the distribution of solute element in entire billet. The momentum equation, energy equation and component transfer equation in multi-component system were solved by ANSYS Fluent software. The results indicated the redistribution of solute at the solid-liquid interface led to the higher C concentration at the solidification front. The sucking which was at final stage of solidification aggravated central segregation of billet. At the end of solidification, the maximum positive segregation occurred at the center of billet, while the minimum negative segregation emerged at 9 mm from the surface of billet. The corresponding segregation degree of C for them were 1.71 and 0.75, respectively.