Prozesssimulation der Bauteil-Abschreckung in flüssigen Medien: Zur Analyse des mehrphasigen Strömungs- und Wärmetransports in Siedeprozessen

The quenching process during heat treatment of steel parts is significantly influenced by boiling phenomena. At wall temperatures above the liquid boiling point, the vapour formation and the interaction of the vapour phase with the liquid flow field is determining the local cooling conditions of the workpiece. High temperature gradients can result in an inhomogeneous distribution of the final material properties (e.g. hardness). A multiphase flow and heat transfer model is utilized to simulate the local flow field and the resulting cooling conditions during quenching. The applied bubble-crowding approach is able to investigate the different boiling phases within one single numerical model. Simulation results of the transient cooling of cylindrical specimens in an axial water flow are discussed for various flow velocities and liquid subcoolings and are compared to experimental results. The determined heat transfer coefficients are utilized to calculate the phase transformation and the surface hardness within a material simulation approach, so that the result of the quenching process with respect to the initial liquid flow conditions can be predicted.