The oxygen

nitrogen and inclusion content in liquid steel at converter blowing end point

after added de- oxidizer and alloying at tapping of converter

ladle argon stirred

tundish

and in billet of steel Q235A(0. 14%～0.22% C

0.30%~0.65%Mn)melting by 80 t top and bottom combined blown converter-ladle argon stirring - concasting flow sheet have been examined and analyzed. Results showed that end point oxygen content in steel was 350×10

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after added deoxidizer and alloying the oxygen content decreased by 42%

with ladle argon stiring the oxygen content was further de- creased and finally the average oxygen content in billet was ≤25×10

-6

the nitrogen content in steel increased from 20× 10

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at converter end point to 40×10

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in billet; the inclusion content decreased

by about 50% by adding deoxidizer

al- loying and argon stiring

and the inclusion content in billet was ≤45×10

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the size of most inclusions was ≤10 μm

and maximum inclusion was 20 μm.