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- Title
DETECTION AND PROCESSING OF SOUND SIGNALS IN STEEL QUENCHING.
- Authors
Ravnik, Franc; Grum, Janez
- Abstract
In the production of machine components a manufacturing process often ends with heat treatment such as quenching by tempering. Generation of internal stresses during heat treatment and residual stresses present thereafter frequently result in non-uniform hardness and depth of a quenched layer, which produces distortion of a machine component and generation of residual stresses. The choice of optimum parameters of a quenching process and monitoring of the process itself ensures the achievement of the specified hardness and residual stress at the surface of the machine component. The paper treats an experimental setup comprising detection of acoustic emission in the course of quenching. Due to heat transfer from a specimen to a quenching medium, film boiling and nucleate boiling occur round a heated object, which strongly affects quenching. An investigation of acoustic emission in the quenching process was carried out with cylindrical specimens made of chrome-molybdenum heat-treatment steel 42CrMo4. The cylindrical specimens of two shapes were quenched in five different recommended 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 acoustic-emission signals can provide useful information that confirms differences occurring in quenching with different quenching media and under different quenching conditions. The quenching results obtained from acoustic-emission signals during the quenching process can be confirmed by variations of residual stresses and hardness in the cross section. The results confirm the applicability of the new approach to the control of steel quenching.
- Subjects
ACOUSTIC signal processing; STEEL quenching; ACOUSTIC emission; MANUFACTURING processes; HEAT treatment
- Publication
Journal of Acoustic Emission, 2014, Vol 32, pS165
- ISSN
0730-0050
- Publication type
Article