Study of the behaviour of mould powders for continuous casting by using the heating microscope

Mold powders, initially fly ash based, were introduced about 40 years ago in the steel continuous casting process. Nowadays, also synthetic powders consisting of mixtures of various minerals are used. The aims of the powders, when added to the free surface of the liquid steel in the mold, can be summarized as follows: thermal isolation of the steel surface, in order to prevent its solidification; protection of the steel surface from the oxidation; lubrication and heat transfer control between the mold wall and the solid steel shell; absorption of non-metallic inclusions coming from the steel. The purpose of this work is to characterize the thermal behavior of some mold powders for continuous casting when they are subjected to different heating cycles: heating rate of 30 deg. C/min up to the sample fusion; heating rate of 80 deg. C/min up to the sample fusion; instantaneous or 'flash' heating, which allows to heat the sample in few seconds. On the basis of predetermined time or temperature intervals applied, this study yielded to different results, like the melting temperature, the presence of crystallizations, and the phenomena that occur in the material.