Formation of Titanium Carbonitride from Hot Metal
Yun Li, Yongquan Li, Richard J. Fruehan
Studies on the formation of TiC and Ti(C, N) from hot metal were preformed to determine the conditions required for the formation of a protective layer rich in titanium carbonitride on the refractories in the blast furnace hearth. In situ observations of the formation of TiC and Ti(C, N) from carbon-saturated iron containing 0.07 to 1.3 mass% titanium were made at 1 673 to 1 873 K using a confocal scanning laser microscope equipped with an infrared image furnace. In order to measure the activity coefficient of titanium, the solubility of titanium in carbon-saturated iron was measured and found to be 1.3, 1.0, and 0.3 mass% at temperatures of 1798, 1772, and 1670 K, respectively. The activity coefficient of titanium in carbon-saturated iron is expressed as logfTi=–5.41+6890/T. Based on the results the conditions for Ti(C, N) formation and the amount of TiO2 addition to a blast furnace were calculated. At 1 773 K and 1.0 atm of nitrogen, the minimum titanium in hot metal to form Ti(C, N) was determined to be 0.2 mass%. Under typical blast furnace operation conditions, a titanium load of 3.6–5.2kg TiO2/tHM is required. It was conclude that in situ observation using confocal scanning laser microscope provided us a unique and reliable technique to study thermodynamic of some molten metal systems.