Determination of surface heat-transfer coefficients during quenching of steel plates

Abstract

The experimentally determined relationships between temperature and time in quenched steel plates have been used in conjunction with an explicit finite-difference technique to determine the effect of surface temperature on the magnitude of the surface heat-transfer coefficient in water, polymer, and oil quenchants. In the case of the water quenchant the results obtained were very sensitive to the degree of oxidation of the specimen surface; this effect was associated with the degree of stability of the vapour blanket produced during the early stages of quenching. The polymer quenchant did not possess a clear advantage over water except where the concentration of the latter was as high as 25%. In comparison, the values of the surface heat-transfer coefficients obtainedfrom the oil quenchant were very low; this was associated with a relatively short nucleate boiling stage.