*Review* **A Review of the Boiling Curve with Reference to Steel Quenching**

**Manuel de J. Barrena-Rodríguez 1,2, Francisco A. Acosta-González 3,\* and María M. Téllez-Rosas <sup>1</sup>**


**Abstract:** This review presents an analysis and discussion about heat transfer phenomena during quenching solid steel from high temperatures. It is shown a description of the boiling curve and the most used methods to characterize heat transfer when using liquid quenchants. The present work points out and criticizes important aspects that are frequently poorly attended in the technical literature about determination and use of the boiling curve and/or the respective heat transfer coefficient for modeling solid phase transformations in metals. Points to review include: effect of initial workpiece temperature on the boiling curve, fluid velocity specification to correlate with heat flux, and the importance of coupling between heat conduction in the workpiece and convection boiling to determine the wall heat flux. Finally, research opportunities in this field are suggested to improve current knowledge and extend quenching modeling accuracy to complex workpieces.

**Keywords:** boiling curve; quenching severity; boiling and quenching heat transfer; metal quenching heat flow
