Effect of quaternary basicity on softening–melting behavior of primary slag based on magnesium flux pellet

Abstract

It is generally accepted that the softening–melting properties of ferrous burden play a vital role in optimizing the shape and position of cohesive zone. The effect of quaternary basicity and atmosphere on softening, melting and permeation temperatures of primary slag based on magnesium flux pellet was investigated by visualization method. The mechanisms were analyzed utilizing thermodynamic calculation, X-ray diffraction analysis and electron probe microanalysis. The results indicated that the softening and melting temperatures of oxide samples increased by approximately 120 °C with increasing quaternary basicity from 0.3 to 1.2 owing to the formation of slag phases with high melting point and solid Fe. Meanwhile, the difference between softening and melting temperatures decreased from 21 to 11 °C. The permeation temperature was not affected by the quaternary basicity and fluctuated around a level of 1250 °C, given that the permeation temperature depends on the wettability between slag and coke bed. On the other hand, as the ratios of CO/CO₂ varied from 3/7 to 7/3, there were no significant differences in either the softening or melting temperatures, whereas the permeation temperature was increased from 1239 to 1271 °C since the reduction of FeO-bearing phases to solid Fe could decrease the wettability between slag and coke bed.