The effect of two processes of calcium treatment: two step process (LF + Ca-Si wire feeding - VD + Ca- Si wire feeding) and one step process (LF - VD + Ca-Si wire feeding) at Xiangsteel on morphology of inclusions and mechanical properties of Nb-Ti microalloying grade E hull steel (0. 10%C) has been studied by thermodynamic calculation on equilibrium of Als - [O
]
and equilibrium of Ca
residual
- Als. Results showed that as S in steel ≤0. 003%
T[O
]
≤15 x 10
-6
and controlled Als in steel 0. 02% 〜0. 04%
after one step process of calcium treatment the W4 pun spherical inclusions in steel were up to 93%