Multi-Scale simulation of heat treatment of hot-work tool steels
This project aims at realistic prediction of the evolution of the microstructure, residual stresses and distortion during the entire heat treatment cycle including tempering by means of FE-modeling and simulation.Copyright: ICMEaix
The increasing demand on energy and material efficiency has introduced the concepts of light weight construction to the automotive industry. The motivation to reduce the weight by replacing steel with large aluminium-die casting structural parts challenges the tool makers to optimize the performance of their die casting molds. Large dimensions require higher casting temperatures so higher thermal stresses arise during operation. Besides, the strength and creep resistance of the tool steel is lowered at the operation temperatures, leading to premature failure of the casting mold. Thus, the trends in the operating conditions have to be taken into account during conception, design and manufacturing, including the heat treatment that has a vital impact on the mechanical properties and functionality of the mold. A quantitative description of the distortion and the residual stress state after the heat treatment enables to decrease the post-machining efforts and to predict the component’s service life.
An ICME-type simulation approach was developed to quantitatively describe the heat treatment outcome in terms of distortion and residual stresses. The thermo-physical and mechanical material response is considered by coupling thermodynamic-based precipitation simulations in MatCalc with the Finite Element Method FEM in Abaqus. A comprehensive FORTRAN code was programmed, linking several sub models including the effects of interacting physical events arising on the micro- and macroscopic scales. Phase transformations are modeled based on continuous Time-Temperature-Transformation CCT diagrams. Strength, strain hardening and further thermo-physical properties are modeled according to temperature and microstructure changes. Precipitation simulations are carried out in MatCalc for different tempering temperatures, delivering decisive parameters to simulate the stress relaxation during the tempering stage. Finally, the complete process is simulated after setting thermal (heat transfer) and mechanical boundary conditions in Abaqus. The final output of the simulation includes space-resolved microstructure, yield strength, residua stress and shape change (distortion) of the mold.
Institute for Materials Applications in Mechanical Engineering IWM,
RWTH Aachen University
|Kind & Co Edelstahlwerk GmbH & Co. KG||Bielsteiner Straße 24‑130,
- Eser, A.; Bezold, A.; Broeckmann, C.; Schruff, I.; Greeb, T. (2014): Tempering-Simulation of a thick-walled Workpiece made of X40CrMoV5-1 Steel. In: HTM 69 (3), S. 127–137. DOI: 10.3139/105.110225.
- Eser, A.; Broeckmann, C.; Simsir, C.: Multiscale modeling of tempering of AISI H13 hot-work-tool steel – Part 1: Prediction of microstruture evolution and coupling with mechanical properties; Computational Material Science; 113 (2015) S. 280-291
- Eser, A.; Broeckmann, C.; Simsir, C.: Multiscale modeling of tempering of AISI H13 hot-work-tool steel – Part 2: Coupling predicted mechanical properties with FEM simulations; Computational Material Science; 113 (2016) S. 292-300