With the deoxidation by adding ferroaluminium and ferrosilicon in EAF tapping and the LF initial refining slag (/%:27.39~37.34 Al

2

O

3

38.42~38.68 CaO，14.20~18.38 SiO

2

8.50~10.72 MgO，0.82~0.89 FeO，0.27~0.33 MnO，0.69~0.74 S，0.66~0.75TiO

2

（CaO）/（SiO

2

）=2.09~2.72

（CaO）/（Al

2

O

3

）=1.04~1.40)

at LF end point the T[O

]

is 0.0012% ~0.001

9%

the T[N] is 0.0043% ~0.0050%

and the [Ti] and [Ca] are respectively 0.002% and 0.006% ~ 0.009%. The analysis on oxide inclusions in bearing steel GCr15 at LF refining end show that the main oxide inclusions in steel are magnesia-alumina spinel (

MgO·

Al

2

O

3

) and calcium oxide-niagnesium-alumina spinel (

CaO·MgO·

Al

2

O

3

) ； the average size of magnesia-alumina spinel is less than 0. 5μm

and as MnS

TiN etc precipitated on them the average size increases； the average size of calcium oxide-inagnesia-alumina is normally more than 2μm and in refining temperature this inclusions are liquid state and easily aggregate and grow up

their size ( 1.39 〜2.12μm) is more than solid status calcium oxide-magnesia-alumina-MnS

so easily removed by floating up and absorbed by refining slag. With decreasing sulfur content in liquid during refining process

the average size of bearing MnS compound inclusions with core of magnesium-alumina and calcium oxide-magnesium-alumina spinel decreases. With suitable decrease of MgO content in refining end slag

optical basicity and viscosity of end slag the amount and average size of inclusions in steel shall be decreased.