Carbon pickup of interstitial free steel from Al2O3-C refractories

Samples of interstitial free (IF) steel were heated in alumina-graphite crucibles with flux cover at 1600degreesC for 120 min in a medium frequency induction furnace. The carbon contents of IF steel samples taken from the molten steel at times 0, 5, 10, 20, 30, 45, 60, 90 and 120 min were examined and the refractories after heating were investigated by electron probe microanalysis (EPMA) with energy dispersive spectroscopy (EDS). The steel carbon content increased rapidly in the first 10 min, and then decreased because of the formation of a decarburising layer on the refractory. This layer separated the molten steel from the bulk refractory and stopped pickup of carbon. At the same time, decarburisation via oxygen through the flux and liquid layer started to reduce the carbon content in the molten steel.