Manufacturers regularly employ finite-element (FE) process modeling tools for the simulation of heat treatment applications, such as quenching. These tools may utilize thermal, mechanical and microstructural calculations in the analysis of part distortion and residual stresses. Heat treatment modeling workflows are challenged by the requirement for user-provided heat transfer boundary conditions, which vary based on part geometry and process parameters. Representative Heat Transfer Coefficients (HTCs) are typically reversed-engineered using experimental thermocouple data, thermal simulations and inverse optimization methods. This paper will present ‘state of the art’ developments integrating computational fluid dynamics (CFD) capabilities into the heat treat modeling environment of the DEFORM system. It will describe how CFD and thermal modeling of a quench medium is being coupled with deformation and heat transfer modeling of a part through the use of CFD-calculated, local heat transfer boundary conditions. Studies verifying the implemented CFD methods against published literature will be summarized. Application examples will show how residual stress and distortion in parts, during single-part or batch gas quenching, is made possible by coupled CFD and thermo-mechanical process modeling tools.

For over two decades, heat treat modeling has progressed from an academic concept to a mature production tool. This presentation will discuss many barriers that have been mitigated with a wide range of developments. Early limitations included solver speed and robustness, material data, specialized heating and the requirement to include microstructure development models over a series of dissimilar operations and processes. Solver improvements ranging from parallel processing to specialized iteration methods allow models with millions of elements to run on a personal computer. Additional degrees of freedom have greatly improved solution accuracy. Meshing techniques allow users to identify critical regions for a finer mesh, such as the surface of gear teeth that will be carburized. Rotational (and other) symmetry is frequently used to further refine many models. Driven by the demand for modeling data, sources for quality material properties have increased over the years. Additionally, tools to approximate required data based on chemistry are available and maturing. Radiant, convective, electrical resistance and induction heating effects are incorporated into heat treat simulation systems. Integrated simulation systems also include large deformation behavior to capture the effects of forging, coining or other mechanical processes on the microstructure. A vision of the future will include the use of Design of Experiments (DOE) and optimization in heat treat simulation. How companies will model the entire process chain to build a more accurate fatigue model for the part in service will be discussed. In terms of TRL (technology readiness level), heat treat simulation was in the 2 – 3 range in the 1990’s. Today it is in the 7 – 8 range and moving quickly.