Title: Sound emission phenomena analysis at boundary layer during steel quenching

Authors: Franc Ravnik; Janez Grum

Addresses: Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia ' Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia

Abstract: Mechanical properties after quenching, such as residual stresses and hardenability depend on optimum parameters of a quenching process chosen, and monitoring of the process itself. In order to control the hardening process, one should be able to monitor the quenching process in real time. The paper treats an experimental setup comprising detection of sound emission together with some results obtained in the course of quenching process. Due to heat transfer from a specimen to a quenching medium, film boiling and nucleate boiling occur around a heated specimen, which strongly affects sound-pressure signals emitted from the surface. Sound-pressure signals are shown in 3D diagrams. The analysis of sound-emission signals are connected with wettings cinematics and can provide useful information that confirms differences occurring in quenching with different quenching media, different specimen's shapes and under different quenching conditions. They can give useful information and confirm the differences caused by different quenching conditions.

Keywords: sound emission; acoustic spectrography; cooling rate; polymeric water solutions; sound pressure level; vapour film; boundary layer; steel quenching; hardening; heat transfer; film boiling; nucleate boiling.

DOI: 10.1504/IJMMP.2016.079150

International Journal of Microstructure and Materials Properties, 2016 Vol.11 No.3/4, pp.247 - 261

Received: 29 Dec 2015
Accepted: 17 Feb 2016
Published online: 14 Sep 2016 *

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