Vorhersage des Einsatzhärtungsergebnisses aus dem Aufkohlungsprofil und den Abschreck- und Anlassbedingungen

In the present thesis, the development of the software SimCarb QuenchTemp for computer aided case hardening is described that solves the simulation task, in which way a certain carbon depth distribution obtained by carburizing is transferred to the resulting hardness profile and microstructure composition respectively after quenching and subsequent tempering, depending on the material, workpiece and process. For this purpose, an empirical and a thermophysical model are formulated and implemented.
In the empirical model, Jominy end quench curves are calculated from a formula proposed in the literature by means of the chemical composition and the austenite grain size of the used steel. The evaluation of these end quench curves occurs at the applicable distance from the end face. The workpiece geometry is characterized by a representative cylinder diameter. The cooling capability of the quenchant is described by the Grossman quench severity. For the calculation of the tempering from the quenching hardness, diminution factors depending on the carbon concentration are applied.
in the thermophysical model, a time distribution of the temperature is simulated for the infinitely long solid cylinder during the quenching process. For this purpose, a modified Fourier temperature conduction equation is solved by means of an explicit finite difference method. Temperature dependent coefficients of heat transfer and conduction are used in the simulation. To determine the depth dependent microstructure development and hardness distribution, the relevant cooling curves of the simulated temperature distribution are compared with cooling curves of continuous cooling transformation diagrams. Theses cooling curves are computed beforehand for customary case hardening steels and programmed in SimCarb QuenchTemp. Depending on the quenching hardness, the tempering hardness is calculated from Hollomon-Jaffe parameters in the thermophysical model.