Realistic modelling and optimisation of steel section cooling process

Abstract

The cooling process in the manufacture of long steel products generates residual stresses and bending in the section. This initial state, arising from the cooling bed, influences the final residual stresses and bending at the end of the subsequent processes. Owing to the importance of the cooling process, this paper presents realistic modelling and optimisation using computational fluid dynamics (CFD) and finite element analysis. Computational fluid dynamics rendered it possible to accurately overcome two main problems common to previous cooling models: the realistic modelling of the heat transfer coefficient (especially important when modelling outdoor cooling beds because of the implications of forced convection) and the precise view factor modelling of the different section surfaces (useful when modelling a complex section). After decoupled CFD thermo‐analysis, the temperature record of each node in the section was loaded into the finite element stress displacement model. The relevant influence of steel phase transformation was considered applying a combined methodology, involving an ABAQUS user subroutine. Accordingly, accurate residual stresses and bending were obtained. After establishing the models, several strategies were analysed for reducing the residual stresses during the cooling process. Results were successfully validated with experimental data from structural section producers.

Keywords:

• Cooling bed
• Residual stresses
• Phase transformation
• Computational fluid dynamics
• Finite element analysis

The authors would like to thank the Research Fund for Coal and Steel (RFCS) for its financial support for the RFS‐CR‐03012 and RFS‐PR‐06035 projects. We are grateful to Dr Maag, Mr Haasler and Mr Eicke and the rest of the staff at the plant for the valuable experimental data provided. We express appreciation to the ‘Dirección General de Investigación’ at the Spanish Ministry of Science and Technology for the DPI2006‐03060, DPI2006‐14784, DPI‐2006‐02454 and DPI2007‐61090 projects. Last but not least, the authors would like to thank the Autonomous Government of La Rioja for its support through the ‘3° Plan Riojano de I+D+I’.