Model of heat transfer during quenching in sodium polyacrylate solutions

Abstract

A model is proposed to describe heat transfer during the later stages of a quench in sodium polyacrylate solutions. These quenchants exhibit characteristics similar to those of an oil quench, with a maximum rate of heat transfer at temperatures much higher than that normally obtained from aqueous quenchants. This is associated with a pronounced range of temperature (400–100°C) where the surface heat transfer coefficient is very low and the surface of the component is covered with a viscous slurry laden with almost stationary bubbles. The present work demonstrates that the heat transfer during this stage of the quench may be explained in terms of a heat conduction model, with heat flow through the vapour layer similar to that found during the vapour blanket stage at the start of the quench. Thus, in both instances the vapour acts as a layer of insulation, in contrast to the nucleate boiling stage, where rapid heat flow is associated with the release of individual bubbles.

MST/2065