The evolution of inclusions in the refining process of EH36 steel produced by the route of "120 t BOF-LF- RH-260 mm slab CC” has been researched. Through sampling and testing of each working procedure in situ

in combination with inclusions thermodynamic calculation

the variations of inclusion types and size are analyzed. It is found that the number density of inclusions in steel gradually decreases

but the number density of >5

μm

large particle inclusions gradually increases during the refining process of MLF—>RH—>tundish". The main types of large particle inclusions are MnO- SiO

2

series oxide and CaO Al

2

O

3

series calcium aluminate

such as 3 CaO·Al

2

O

3

12CaO ·Al

2

O

3

and CaO・Al

2

O

3

. During the refining process

CaO · 6Al

2

O

3

and CaO ·2Al

2

O

3

are formed first when the Ca content in steel is low

and the main inclusions of 12CaO

7Al

2

O

3

3CaO

Al

2

O

3

are formed with Ca content increasing in steel.