Simulation of Shell Hardening of Unalloyed Steel Cylinders Due to High Speed Quenching

Kobasko et. al. have primarily shown that rapid water quenching can create compressive residual stresses near the surface and hereby a significant increase of the fatigue-limit results (Intensive Quenching). Such processes result in an increase of hardness. Depending on steel grade, dimensions of the component and quenching intensity through hardening or only shell hardening will result. In this work shell hardening processes were investigated in a more detailed manner for cylinders made out of two different unalloyed steels.

The goal of the work was the finding of general requirements to reach on one hand a sufficient surface hardness paired with a non through hardened hardening profile. On the other hand compressive residual stresses in the near surface area should be produced as high as possible to receive huge live time cycles of the heat treated work pieces. Because of the large amount of experimental work, which is necessary to determine these general requirements simulations were performed to support the experiments.

The simulations studies were carried out with the finite element simulation software SYSWELD. Simulations will be compared with the attended experimental work in which cylinders made out of C35 and C56E2 were quenched with heat transfer coefficients in the range of 20000 to 50000 W/m²K. The comparison will extend over results for microstructure, residual stresses and hardness. The experiments as well as the simulations shows, that compressive stresses of 1200 MPa in the surface near area can be achieved.

Keywords: high speed quenching, shell hardening, compressive stresses, unalloyed steel