The production process flowsheet of tube bloom for 12Mn4V

37Mn

26CrMo48V etc steels is 150 t EAF- LF-VD-Φ210~310 mm round bloom casting. Due to the factors including argon shielding no-close etc

during 150 t ladle to 26 t tundish process the increment value of nitrogen content in liquid △N fluctuates largely

the largest △N is up to 65 x 10

-6

. With using the measures including improving shroud cleaning implement

increasing mechanical arm counterbalance

improving tight tough touch of ladle flow mouth and shroud

and maintaining argon flow rate 120 L/min and pressure 0.05 MPa

the increment value of nitrogen content in liquid from ladle to tundish is stably less than 5 X 10

-6

and the nitrogen content in casting tube bloom is 30 x 10

-6

~60 x 10

-6

.