Maximierung der randnahen Druckeigenspannung von Stählen mit Hilfe einer Hochgeschwindigkeits Abschreckanlage

Abstract

The technical progress has the demand of parts, which withstand longer higher loads. This is fulfilled either by an improvement of the material or through an optimization of the manufacturing process. These optimizations are chosen to improve specific properties which enhance the life spans of parts. A classical process of improving the life span is the case hardening. Among other things, the case hardening generates compressive residual stresses near the surface. This compressive residual stresses improves the fatigue strength. By hardening parts with high quenching velocities a great martensitic phase occurs near the surface, before the phase transformation begins in the core. The martensitic transformation expands first the surface than the core, which leads to compressive stresses. The great martensitic phase proportion on the surface withstand the resulting tensile stresses due to the phase transformation in the core and after the quenching remains compressive residual stresses at the surface. The knowledge of the necessary quenching parameters to generate compressive residual stresses at the surface exists only for single parts and materials. The goal of this work is to generalize this knowledge with simulation studies. This objective was realized with a newly developed high velocity water quenching machine. With experiments were verified the nearly correctness of the simulation studies. And with this simulations the influence of different material properties were evaluated. In the last part of this work, the improvement of the life strength due to the high compression was confirmed.