and inclusion content in steel was proposed by analysis on relation between T[O
]
and stable oxide inclusion content in liquid casing pipe steel 37Mn5 at 1 540 ~ 1 580 ℃ during 100 t LF refining and effect of slag basicity on active oxygen in steel in steel-slag equilibrium state. The thermodynamic calculation and test results showed that [Al
]
s was 0.03%-0.04% and refining slag basicity was 3 with (CaO)/(Al
2
O
3
) =3~3.5
the oxygen content in steel 37Mn5 decreased to 10 x 10
-6
no heavy-series inclusion occurred in pipe products
and fine-series inclusion rating A + B + C + D ≤ 5 to meet the requirement of service.