Authors: Kyozo Arimoto
Addresses: Arimotech Ltd., 4-3-2-701 Habucho, Kishiwada, Osaka, 596-0825, Japan
Abstract: The appearance of lower hardness at the surface than at the core in steels after through hardening is known as 'inverse quench-hardening'. Pioneering work was performed in the 1970s by devising a simple test method where cylindrical specimens were cooled by air and sodium chloride solution sequentially. The hardening mechanism in the same specimens as the pioneering work was examined using a finite element simulation method. However, it has not been completed for lack of experimental quenching cooling curves for the comparisons. In this study, the same experiments as those of the pioneering work were conducted to explain the origin of the phenomenon thoroughly. Experimental cooling curves showed a temperature rise due to recalescence as predicted by the simulation. The inverse quench-hardening phenomenon was also found in the measured and simulated hardness distributions of the specimens. Finally, the origin of the phenomenon was discussed based on results obtained from this study and literature.
Keywords: heat treatment; simulation; recalescence; inverse quench hardening; steel quenching; cooling curves; temperature; hardness distribution.
International Journal of Microstructure and Materials Properties, 2016 Vol.11 No.3/4, pp.214 - 228
Received: 04 Jun 2015
Accepted: 07 Dec 2015
Published online: 14 Sep 2016 *