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This research executed the stir quenching that generated the circulation convection of the coolant with a motor pump from the pipe set up in the cooling tank bottom part, and did the quenching experiment of Ag and carbon steel SCM420 that evaluated the cooling power. The oil temperature of the coolant was changed from this experiment research in the condition with constant stir speed of the coolant, and the influence that it exerted on cooling the quenching material was observed. It took the dynamic behavior of the appearance of generation and flaking off of the steam film on the surface of the metal when quenching it with a high-speed camera, and the image was achieved, and moreover, the fixed quantity analysis at the flow velocity of the heat flow was done by using the PIV metrology, and making the convection of the steam film and, the coolant visualization was achieved.

In this research, the gas quenching evaluation device was developed to establish the gas quenching technology, and the PIV system of making to visualization of the thermal flow to clarify the heat transfer behavior in the gas cooling was constructed. And, the cooling curve of the test piece on the surface was measured by the quenching experiments by the gas cooling doing by actually using several kinds of gases, and using the thermo-couple, and the cooling power in the gas cooling process was evaluated.

In the quenching process, heat transfer behavior will is very complex due to boiling, generation of the bubble by the boiling in the quenchant, flaking off of steam film in metal surface. In this research, the behavior of steam film in quenching process was investigated with high-speed video camera by visualization method. The behaviors of the boiling bubbles including generation and movement as well as the breaking during stirring quenching process were clarified. The flow velocity fields around the quenching parts at no stirring and stirring quenching with various flow velocities on nozzle were investigated. In order to identify the heat transfer coefficients by using of the measured cooling curves of surface temperature. Effects of stirring and oil temperature on breaking the steam film were confirmed.

In the quenching process, heat transfer behavior will is very complex due to boiling, generation of the bubble by the boiling in the quenchant, flaking off of steam film in metal surface. In this research, the behavior of steam film in quenching process was investigated with high-speed video camera by visualization method. The behaviors of the boiling bubbles including generation and movement as well as the breaking during stirring quenching process were clarified. The flow velocity fields around the quenching parts at no stirring and stirring quenching were investigated. In order to identified the heat transfer coefficients by using of the measured cooling curves of surface temperature. Effects of stirring on breaking the steam film were confirmed.

During quenching process, steam film and boiling bubbles occurring on the boundary layer between quenching steel and quenchant often lead to uneven heat transfer and in turn distortion and heterogonous microstructure in quenching steel. In this paper, experiments of stirring quenching to induce forced conventional flow and to break boiling film are carried out. The formation and movement of boiling bubbles and forced convectional flow are investigated with a high speed camera. Visualization of boiling bubbles and forced flow are performed by PIV-PTV methods. Furthermore, cooling curves of a steel cylinder during quenching are measured and the heat transfer coefficient between quenchant and steel is identified. Finite element simulation is performed to analyze the flow effect on heat transfer. By combining analysis of visualized flow from measurement and simulation, the behaviors of steam film and forced flow are clarified and improvement on heat transfer by stirring is confirmed.