The effect of position on the face of a steel plate on the quenching p
rocess during cooling from a typical austenitisation temperature has b
een examined. In addition, the effect of plate orientation on the quen
ching mechanism has been investigated. The most significant effect of
these parameters on the quenching process relates to the length of the
vapour blanket stage, which is very sensitive to position on the surf
ace of the specimen. This has considerable importance in relation to t
he production of unhardened regions. A markedly different mechanism of
heat transfer during nucleate boiling at different positions on the f
ace did not give rise to corresponding differences in the surface heat
transfer coefficients at this stage in the quench. The investigation
of heat transfer in the surface of the plate has been supported by sti
ll photographs that clearly show the different processes at different
positions;and orientations of the plate. In particular they show viole
nt disruption of the surrounding quenchant as large packets of vapour
are nucleated in quick succession on the underside of a horizontal pla
te.