TY - THES

T1 - Optimization of heat transfer model used in the continuous casting of stainless steel

AU - Wahib, Muhammad

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - The continuous casting process is a crucial step-in stainless-steel production that involves the solidification of molten steel into continuous slabs or blooms. This casting process involves transferring of molten steel from a tundish to a water-cooled mold, where solidification starts. As the solidifying strand exits the mold, it is supported by rotating rollers in the secondary cooling zone. Water and air mist is continuously sprayed to achieve complete solidification. After complete solidification, the slabs are cut and sent for further processing. The efficient control of heat transfer is crucial to optimize the casting process, preventing casting defects and enhancing production efficiency. A key challenge in continuous casting is preventing breakout of the liquid metal, which occurs when the solid shell is too thin, leading to rupture and spilling of liquid metal. The shell thickness depends on the heat transfer behaviour during solidification. This thesis is performed in collaboration with the stainless-steel company Aperam and focuses on optimizing the heat transfer model used in continuous casting of stainless steel. The heat transfer model is influenced by the thermodynamic properties of steel including heat capacities, solidification enthalpy, and heat transfer coefficients. The primary objective is to provide Aperam with accurate thermodynamic inputs for steel grade 304L and 316L, enabling a thorough understanding of the model¿s dependence on these values. For this Thermo-Calc and IDS databases are used to collect different thermophysical parameters. Additionally, a CFD heat transfer and solidification model is developed considering the Aperam continuous casting plant conditions, and respective heat transfer coefficients (HTCs) are calculated for the mold and the secondary cooling region. These inputs are used to predict the temperature and solidification profiles at different sets of casting speeds and superheat values for both steel grades in the DYNACS and CFD model. Further these models¿ temperature results are compared with the real temperature data acquired from a pyrometer at the continuous caster. The findings of this study highlighted the importance of accurate thermophysical parameters and heat transfer conditions. Further, the parametric study investigated the role of individual thermophysical parameters on the temperature and solidification profiles and helped to predict the behaviour of steel grades under varying process conditions such as casting speeds and superheat values. This study provides Aperam a valuable insight into the relationship between the thermophysical parameters and solidification profiles. This knowledge will enable the company to optimize the process conditions, such as casting speed, maximizing the production efficiency, and minimizing the risk of breakout defects.

AB - The continuous casting process is a crucial step-in stainless-steel production that involves the solidification of molten steel into continuous slabs or blooms. This casting process involves transferring of molten steel from a tundish to a water-cooled mold, where solidification starts. As the solidifying strand exits the mold, it is supported by rotating rollers in the secondary cooling zone. Water and air mist is continuously sprayed to achieve complete solidification. After complete solidification, the slabs are cut and sent for further processing. The efficient control of heat transfer is crucial to optimize the casting process, preventing casting defects and enhancing production efficiency. A key challenge in continuous casting is preventing breakout of the liquid metal, which occurs when the solid shell is too thin, leading to rupture and spilling of liquid metal. The shell thickness depends on the heat transfer behaviour during solidification. This thesis is performed in collaboration with the stainless-steel company Aperam and focuses on optimizing the heat transfer model used in continuous casting of stainless steel. The heat transfer model is influenced by the thermodynamic properties of steel including heat capacities, solidification enthalpy, and heat transfer coefficients. The primary objective is to provide Aperam with accurate thermodynamic inputs for steel grade 304L and 316L, enabling a thorough understanding of the model¿s dependence on these values. For this Thermo-Calc and IDS databases are used to collect different thermophysical parameters. Additionally, a CFD heat transfer and solidification model is developed considering the Aperam continuous casting plant conditions, and respective heat transfer coefficients (HTCs) are calculated for the mold and the secondary cooling region. These inputs are used to predict the temperature and solidification profiles at different sets of casting speeds and superheat values for both steel grades in the DYNACS and CFD model. Further these models¿ temperature results are compared with the real temperature data acquired from a pyrometer at the continuous caster. The findings of this study highlighted the importance of accurate thermophysical parameters and heat transfer conditions. Further, the parametric study investigated the role of individual thermophysical parameters on the temperature and solidification profiles and helped to predict the behaviour of steel grades under varying process conditions such as casting speeds and superheat values. This study provides Aperam a valuable insight into the relationship between the thermophysical parameters and solidification profiles. This knowledge will enable the company to optimize the process conditions, such as casting speed, maximizing the production efficiency, and minimizing the risk of breakout defects.

KW - continuous casting

KW - stainless steel

KW - heat transfer

KW - solidification

KW - breakout

KW - thermodynamic properties

KW - CFD modeling

KW - casting speed

KW - superheat

KW - pyrometer

KW - thermo-calc

KW - IDS

KW - production efficiency

KW - Stranggussverfahren

KW - Edelstahl

KW - Wärmeübertragung

KW - Erstarrung

KW - Ausbruch

KW - Thermodynamische Eigenschaften

KW - Thermo-Calc und IDS-Datenbanken

KW - CFD-Modellierung

KW - Gießgeschwindigkeit und Überhitzung

KW - DYNACS

KW - Pyrometer

KW - Produktionseffizienz

U2 - 10.34901/mul.pub.2024.074

DO - 10.34901/mul.pub.2024.074

M3 - Master's Thesis

ER -