Abstract：Interrelations between oxygen content of gear steel and non-metallic inclusions, and transformations conditions for non-metallic inclusions were calculated using the thermodynamic calculation software Factsage. It is found that the components of non-metallic inclusions with higher plasticity in ultra-low-oxygen gear steel should be composed by SiO2 0%~10%, Al2O3 22%~55%, CaO 42%~60%, and MgO 5%~10%, aluminum content would being about 0.020%, calcium content would being more than 0.7×10-6, and oxygen content would being about 0.0005% in molten steel when the reaction between the inclusion and liquid steel arrived in equilibrium. If the compositions of fining slag with CaO>40%, Al2O3≤37%，MgO10%，(%CaO +% MgO)/%SiO2=10, and SiO2 content as low as possible were selected, Al2O3 and MgO • Al2O3 in molten steel can transform into calcium aluminates with low melting point. The results above have been verified in industrial trials.
2011, Vol. 46 
