Quenching Model Based On Multiphase Fluid Dynamics

A fully-coupled model of quenching by submerging for steel workpieces is presented. The model includes cooling of the piece due to piece-to-bath heat transfer calculations by solving the multiphase problem of an evaporable fluid, corresponding metallurgical transformations and subsequent stresses generation. The heat transfer model takes into account different boiling stages, from film boiling at very high surface temperatures, to single-phase convection at temperatures below saturation. The evolution and activation of each heat transfer mechanism depend on the dynamics of the vapor-liquid multiphase system of the quenching bath. The multiphase flow was modeled using the drift-flux mixture model, including an equation of conservation of energy of the liquid phase, and solved with a finite element method. The dependence of heat transfer rates on flow parameters such as velocity and vapor fraction is highlighted. As a result, complex cooling patterns, that cannot be recovered by current methodologies based on heat transfer coefficient calculations, are obtained and consequently, calculation of metallurgical transformations and stress analysis can be predicted more accurately.