Modeling the Quenching and Annealing Process of Massive Hot-Work Tool Steel Components

Vacuum technology is the preferred choice for the heat treatment of die-casting dies. Finite element (FE) simulations were used to optimize the heat treatment process which leads to improved material properties, lower residual stresses and lower cracking probability. The thermo-mechanical model contains martensitic and bainitic phase transformations, the formulation of transformation induced plasticity and an inverse optimization routine to adjust the thermal boundary conditions of the vacuum furnace. The quenching simulation was calibrated by laboratory tests and validated by industrial heat treatments of large test geometries performing residual stress measurements. Additionally, the hardness evolution during annealing was modeled using a precipitation kinetics model of a hot-work tool steel grade which can be combined with the FE simulation. A large testing program including many combinations of annealing times and temperatures was conducted to calibrate the model.