Decarburization of Steel to Ultra-low-carbon Levels by Vacuum Levitation

Vacuum levitation experiments were carried out on approx1 g steel samples initially containing from 35-2000 ppm (mass) carbon, from 40-3300 ppm (mass) sulfur and from 200-800 ppm (mass) oxygen at temperatures in the range 1550-1850 deg C and at vacuums of 20 and 40 Pa. It was found that the rate of decarburization was proportional to the carbon content of the samples. The overall carbon mass transfer coefficient was approx1.6x10 exp -5 m/s and was seen to increase slightly with decreasing chamber pressure. Chemical reaction control was not suggested since the decarburization rate was insensitive to initial sulfur content and the variation associated with levitation temperature due to variation in the initial sample mass.