Effect of Overheating and Oxygen Partial Pressure on Undercooling Degree of Liquid Steel in Contact with Al_2O_3 Substrate

The undercooling behavior of liquid steel on Al_2O_3 substrate at different overheating degrees under different oxygen partial pressures was investigated by sessile drop technique. The results show that under the oxygen partial pressure of 10-23 atm, the degree of undercooling increased from 225 K to 257 K as the overheating degree rose from 10 K to 30 K.Under the oxygen partial pressure of 10-25 atm, overheating had no significant effect on the undercooling degree, which was around 300 K. It illustrates that the increase of inclusions in the liquid steel and the formation of a reaction layer at the interface between steel and substrate will lead to the decrease of undercooling degree as the oxygen partial pressure increases.