Simulation of phase transformations during heat treatment

The QForm – Heat Treatment Module is a joint project between "QuantorForm" and GMT mbH Berlin, and is a continuation of work carried out with them on the QForm-Microstructure Module. The basis of phase transitions simulation is the usage of interpolated S-shaped curves for carbon and alloy steels. This takes into account the effect of alloying elements that shift the curves depending on the content of these elements, as shown schematically in Figure 1.

During the simulation of heat treatment, such as hardening, for each forged or rolled part the cooling rate shall be calculated and determined by the content of the phases. After completion of the simulation for all points the percentage of the phases in the finished product (ferrite, pearlite, bainite, martensite) are calculated. In addition the properties of steel after heat treatment, such as hardness, tensile strength, etc. (Fig. 2) shall also be calulated. The distribution of the content of the phases in accordance to the forged piece volume provides information for calculation of the internal stresses and possible distortion caused by the volume change during martensitic transformation. Calculation of thermal and residual stresses shall be performed by using the module QForm-thermoelasticity.

The QForm-Heat Treatment module might be used for simulation of thermo-mechanical treatment (TMT), ie, heat treatment, combined with the deformation, which must first be calculated by thrr simulation of the process of forging, pressing or rolling. The QForm- Heat Treatment Module can also be used separately to simulate only heat treatment. In this case, it is sufficient to have a geometric model of the part in the form of a STEP or IGES file from any CAD system, which will then be automatically converted into a finite element representation using the module QShape. In both cases, the calculation starts from austenitizing the temperature and continues until achieving room temperature with the given conditions on the surface of the body heating conditions. Within this the heat treatment can be carried out in several stages with time at certain temperatures.