Thermodynamic analysis and evoltion of non-metallic inclusions in the whole production process of 700BL steel

In order to study the effect of calcium treatment on the composition of inclusions in 700BL steel and the precipitation of inclusions during the cooling and solidification, the whole process sampling was conducted to study the evolution of steel components and the morphology and composition distribution of inclusions. Results were compared with thermodynamic calculation results of FactSage. The results show that calcium treatment modified the inclusion from the pure Al₂O₃ to 59.68% Al₂O₃-3.10% MgO-37.22% CaO during the process of refining, and the inclusion was modified the composite inclusions containing titanium after adding titanium. Titanium nitride inclusion was precipitated on a core of calcium aluminate inclusion or directly at the slab and rolling plates, which accounted for more than 50%. Thermodynamic results could reveal measured results in terms of composition. Inclusions were modified from Al₂O₃ and CaO·6 Al₂O₃ to CaO·2 Al₂O₃ and liquid inclusions when the calcium content in the steel increased from 5 ppm to 15 ppm. A large amount of TiN inclusion precipitated rapidly when the steel was cooled to about 1 475 ℃.