Thermodynamic analysis of X80 pipeline steel after calcium treatment

Based on thermodynamic calculation, analysis the inclusions and thermodynamics of X80 before and after calcium treatment on the sample of a steel production. Results show that the effect of Al2O3 inclusions degeneration is good and S would exist in a dissolved state so that avoids the CaS inclusion precipitation when the omega[Als] is 0.04%, omega[O] is adjusted to 0.7x10(-4)%similar to 18x10(-4)%, omega[Ca] is adjusted to 6x10(-4)%similar to 24x10(-4)%, in the meanwhile control of omega[S] below 0.009% at 1873K; Al2O3 inclusions in steel is effectively modified into calcium aluminate, the number and the size of inclusions were reduced, most of them below 5 mu m, and the shape more regular.