Defining the Adequacy of Direct Harden Water Quench Systems

Developing heat treat systems and control plans that produce consistent direct harden (quench and temper) results with a high percent martensite and the corresponding proper mechanical properties is challenging for large components or large batch sizes.  In this study, large section bars of typically water quenched alloy grades were austenitized and quenched under controlled flow conditions.  Various carbon and alloy contents were studied.   The bars were examined by macroetching slices to reveal spotty hardening.  Hardness profiles were also taken on the various alloy bars.  The tests allowed for some key insights into defining the adequacy of direct harden water quench systems, including the idea of agitation thresholds required to prevent soft spots (spotty hardening).