The effect of internal contact pressure on thermal contact conductance during coil cooling

Coil cooling process is an important step in production of certain steel grades. Phase transformations for dual phase steels and precipitations for precipitation hardened steels occur mainly during the coil cooling. Generally, a coil goes through a coil conveyance chain before arriving at the final cooling storage at a steel plant. This conveyance chain contains various thermal contacts with different types of conveyors. Ambient temperatures and weather conditions may also change considerably. Those variables are relatively easy to measure and define in a simulation model whereas internal stresses and contact pressure inside the coil are very challenging to measure in industrial scale process. Thermal conductance between adjacent strip revolutions is dependent of contact pressure. In addition, thermal conductance is influenced by the combined thermal conductivity of steel and oxide layer of contact interfaces as well as thickness profile. In this paper the internal contact pressure between strip revolutions due to strip coiling and gravity are solved and considered when defining thermal conductance. Heat transfer is computed using FE-model, and GAPCON subroutine in Abaqus is utilized to calculate thermal contact conductance, taking into consideration the contact pressure between the strip revolutions. Also, the whole coil conveyance chain commencing from downcoiler mandrel to coil field cooling is implemented.