EFFECT OF PLATE ORIENTATION ON QUENCHING CHARACTERISTICS

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.