Quenching Process Improvement Through Modeling

A recent presentation from Karlsruhe Institute of Technology[1] showed residual stress plots for three variations of a thick wall tube hardening process and experimental evidence that two of the processes resulted in tubes with cracks on the bore while the third process produced crack-free parts. Interested in investigating this in more detail, a study was initiated to investigate additional process variations to better understand the conditions that caused the cracks and to discover quenching conditions that did not cause cracks, while achieving both the desired hardness and residual stress state. With a goal of martensite through the thickness of a 4140 steel tube, and residual compressive stress on the tube bore, a matrix of hardening processes was developed and executed. Results showed that the timing of martensite formation through the thickness had a significant effect on both the in-process stress state and the residual stress state.

[1] Fabian Mühl, Stefan Dietrich, and Volker Schulze, “Internal Quenching: Ideal Heat Treatment for Difficult to Access Component Sections,” IFHTSE Conference, Nagoya, Japan, 2018.