The bottom blowing argon is carried out in commercial production of 40 heats 120t BOF steelmaking process

at blowing 15% the C content in metal is 4.0% with slag ingredient (/%) ： 21.2FeO

2.6A1

2

O

3

5.3MnO

31.2CaO

11.2MgO

23.7SiO

2

3.2P

2

O

5

and basicity 1.3

and at end blowing the C content in liquid is 0.1% with slag ingredient (/%) : 14.5FeO

2.0Al

2

O

3

3.9MnO

49.5CaO

8.0MgO

13.5SiO

2

2.2P

2

O

5

and basicity 3.4. The effect of slag foaming level on removal of nitrogen in BOF liquid

is studied by gas and composition analysis and optical microscope

and the mechanism of secondary removal of nitrogen in slag is discussed. The analysis results show that in earlier blowing period the removal of nitrogen in BOF metal is weaker

the removal of nitrogen is concentrated in 15%~80% blowing process

in last period of BOF blowing the liquid has some nitrogen increment. As the metal droplets exist in slag

the slag foaming level is better and the retained time of CO in slag is longer to increase the change of collision between CO bubbles and metal droplets

the effect of secondary removal of nitrogen is obvious. With N content in charging metal being 53 x 10

-6

with regard to heats with better slag foaming level the BOF end N content average in liquid is 13.7 x 10

-6

and the average removal rate of nitrogen reaches 74.2%

while to heats with lower foaming level the BOF end N content average in liquid is 25.2 x 10

-6

and the average removal rate of nitrogen in liquid is only 52.5%.