Relation Between Sound Emission Occurring Quenching and Mechanical Properties of The Steel After Quenching

F. Ravnik, J. Grum:
RELATION BETWEEN SOUND EMISSION OCCURRING QUENCHING AND MECHANICAL PROPERTIES OF THE STEEL AFTER QUENCHING
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New challenges in heat treatment and surface engineering – conference in honour of prof. Božidar Liščić (09 – 12 June 2009, Dubrovnik – Cavtat, Croatia)

ABSTRACT:
Quenching and tempering often represent the final stage in the production of machine components of manufacturing process. Final mechanical properties, such as residual stress and hardness profiles, therefore depend on optimum parameters of a quenching process and monitoring of the process itself.
The paper treats an experimental setup comprising detection of sound emission in the course of quenching process. Due to heat transfer from a specimen’s surface to a quenching medium, film boiling and nucleate boiling occur round a heated specimen, which strongly affects quenching. An investigation of sound emission in the quenching process was carried out with cylindrical specimens made of chrome-molybdenum heat-treatable steel 42CrMo4 quenched in different quenching media. Sound-pressure signals demonstrated by different amplitudes depending on time at different frequencies are shown in 3D diagrams. It has turned out that an analysis of sound-emission signals can provide useful information that confirms differences occurring in quenching with different quenching media, different specimen’s shapes and under different quenching conditions. Analysis of sound emission signals can give useful information and confirm the differences caused by different quenching conditions. Analysis of the quenching results obtained from sound-emission signals during the quenching process can be confirmed by variations of residual stresses and hardness in the cross section. The results lead to the applicability of the new approach to the control of the hardening processes of steels.


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