Effect of Bubbling Boiling and Breaking of Steam Film on Heat Transfer Coefficient in Stirring Quenching Process

摘要

Steam film occurring on the boundary layer between quenching steel and quenchant takes large effects on their heat transfer, which often results in uneven microstructure and mechanical properties of quenching steel. 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. The heat transfer coefficients were identified from the measured cooling curves of surface temperature. Effects of stirring on breaking the steam film and improving heat transfer were confirmed.