The production flowsheet for steel GCrl5 is 90 t converter-LF-VD-250mm x280mm bloom casting-rolling process. With adding aluminium to deoxidize during converter tapping and refining by high basicity slag [/% : 55 〜 58CaO

3 ~ l0MgO

12~ 16SiO

2

16~24A1

2

O

3

≤ 1 (MnO + FeO)

]

the T[ 0

]

after feeding Al in LF process is 14 x 10

-6

and the T[O

]

at end of LF refining is 10 x 10

-6

. With using SEM (scanning electron microscope) and EDS ( energy dispersive spectroscope) to study the composition distribution of unqualified large DS series inclusions in rod products

it is found that at the center of inclusion the main composition is compound oxide CaO-MgO-Al

2

O

3

outside is wrapped by a small amount of CaS

in this oxides the A1

2

O

3

content is up to about 65% with even distribution

the CaO content is about 20% and the MgO content is about 15%. Statistics analysis results show that after VD vacuum treatment the number o£ diameter more than 13μm  large inclusions per mm

2

increases to 7

after soft stirring that decreases to 2. 1

arid in rod products the one of three large inclusions come from ladle slag.