The composition of macro inclusion in 20MnTiB steel and 45 steel melting by 70 t EAF-LF-CC flow sheet at Egang and ingredient of mold powder and refractory material for concasting process have been analyzed
and it is obtained that the macro inclusion of steel is a composite inclusion which mainly consists of Al
2
O
3
MgO
CaO
Na
2
O and SiO
2
. With improving technology measures including white refining time ≥10 min
controllingAl
s
./Al
t
≥85%
after feoding Ca- Si wire soft argon stirring time ≥7 min
controlling immersion depth of ladle nozzle ≥200 mm and immersion depth of im- mersion nozzle 80~130 mm
and using quality refractory materials
the qualified steel rate for macro inclusion examination increased to 99.77%~100% from original 90.96%~95.31%.