The metallurgy flowsheet of tested production steel grades 26CrMo4

30Mn5 and 30Mn6V is 150 t EAF- LF-VD-0210 〜310 mm tube bloom casting. The results of analysis on inclusions in steels steelmaking by 6 heats using original low basicity tundish covering powder and by 15 heats using high basicity tundish covering powder (/% : 9. 2MgO

0. 87Fe

2

O

3

44.03CaO

7. 53SiO

2

18. 68Al

2

O

3

) show that with using original low basicity tundish covering powder

the Al content in liquid from end VD soft stirring to tundish decreases by 5 x 10

-6

~ 35x10

-6

average Al content decreases by 25 x 10

-6

but that with using basicity 6 tundish covering powder decreases by 10 x 10

-6

~ 20 x 10

-6

with using original covering powder the amount of 1 ~ 10μm inclusions in steel sample at 300 mm

2

area increases obviously from VD to tundish and that of > 10 μm  inclusions decreases

but with using basicity 6 tundish covering powder the amount of 1 ~ 10 μm inclusions in steel sample at same area decreases from VD to tundish and that of > 10μm inclusions decreases obviously

it indicates that as compared with original covering powder the basicity 6 tundish covering powder is more suitable for steelmaking of clean steel.