The diagrams of forming MgO ·Al

2

O

3

2MgO·SiO

2

3Al

2

O

3

2SiO

2

and 2MgO·2Al

2

O

3

·5SiO

2

phase predominance area during refining process of stainless steel 316L (/% : 0. 02C

0. 51 Si

1. 15Mn

0. 030P

.001S

16. 77Cr

10. 12Ni

2. 07Mo

0. 040N

0. 006T

i

0. 004Al) in equilibrium condition after deoxidation are obtained by using thermodynamic calculation method

and the thermodynamic conditions for formation and transformation of various inclusions have been studied and analyzed. Results show that at 1 873 K as the solution Al content in liquid is less than 0. 001 % and the solution Mg content is less than 2 x 10

-7

%

it is available to form the better deformable 2MgO·2Al

2

O

3

·5SiO

2

low-melting-point inclusions； as solution Al content in liquid is less than 1. 7 x 10

-4

%

there is no spinel inclusions MgO·Al

2

O

3

formed in liquid ； and the formation area of high-melting-point inclusions 2MgO ·SiO

2

and 3Al

2

O

3

2SiO

2

is largest. Practice results show that the thermodynamic condition for modification treatment on high-melting-point inclusions 2MgO · SiO

2

and 3Al

2

O

3

·2SiO

2

by adding Ca is sufficient

as solution oxygen content in 180 t LF liquid of stainless steel 316L is 0. 002 0%

the refining end［O］ is 0. 001 5% by feeding silicon-calcium wire 2 m/t

and the rating of C-type inclusions in 2mm cold rolled sheet is 0. 5 ~ 1. 0

the main composition of inclusions is CaO·Al

2

O

3

·SiO

2

.