LD tapping with slag stopper and adding deoxidizer Si-Fe and Mn-Fe and controlling end [C
]
0.026%~0.030%
RH degassing treatment and alloying added Mn-Fe
LF refining with high basicity slag and feeding Ca wire.Examination results showed that in cast billet of pipeline steel the sulphur content was (10~18)×10
-6
the T[O
]
=30×10
-6
the size of most inclusions ≤40 μm
and the main inclusion was calcium aluminate with few Al
2
O
3
and individual MnS being available to increase the resistance on hydrogen-induced cracking (HIC).