The metallurgical flowsheet for steel 18CrNiMo7-6 (/%: 0. 17C

0. 57Mn

0. 24Si

0. 012P

0. 003S

1.70Cr

1. 49Ni

0. 28Mo) is 60t EAF-LF-VD-2.1t ingot. The variation of amount

size and ingredient of inclusions in steel after EAF aluminium pre-oxidation

LF aluminium shot and silicon-carbide mix deoxidant diffusion deoxidation (LF initial slag ingredient /%: 57 ~ 60CaO

20. 5 ~ 22. 0Al

2

O

3

9. 9 ~ 11. 3SiO

2

8. 8 ~ 10. 6MgO

0. 7 ~ 1. 1FeO

0. 7 ~ 0.9MnO)

VD and soft blowing has been analyzed by sampling. Results show that during refining process the amount of  inclusions decreases by 16. 67%

the amount of >10μm inclusions decreases by 50% and the ≥30μm inclusions basically are removed from liquid ； during re

fining process the main formed-inclusions are magnesium-aluminium-calcium compound inclusions and CaS

MgS and MnS etc sulfide; the main inclusions in finished products are Mg-Al oxides and main sulfide is MgS with minor MnS and CaS etc sulfide. The further optimized steelmaking process is to control the formation of small and medium size inclusions.