The pilot production flow sheet for developed weathering steel S355J2W (/% : 0.06 ~ 0. 10C

0.20 ~ 0.40Si

1.00-1. 30Mn

≤0.008S

≤0.020P

0.25 〜0.40Cu

0.30 ~ 0. 55Cr

0.10 〜0. 30Ni

0. 020 ~ 0. 040Nb

0. 020 ~ 0. 050Alt) is hot metal-120 t top and bottom combined blown converter-LF-250 mm x2 000 mm slab CC-≤16 mm plate rolling process. With using the process measures including controlling converter end [ C

]

≤0.05% and [P

]

≤0. 015%

in refining ( FeO) + ( MnO)≤1. 5%

( SiO

2

) ≤15%

refining slag basicity ≥3. 0

[Al

]

s

≥0.025% and feeding calcium wire according to Ca/Al = 0. 06 〜0. 12

in casting using special-purpose mold

shielding flux for weathering steel [main ingredient/%: 34.0CaO

28.0SiO

2

4.6Al

2

O

3

≤

6 ( Li

2

O+ B

2

O

3

)

]

controlling breakdown temperature 1 010 ~ 1 060℃

the aluminium content in ≤16 mm finished plate of weathering steel is 0. 025% ~0. 035%

the average oxygen content in steel is 21 x 10

-6

and the average nitrogen content in steel is 31 x 10

-6

the size of nonmetallic inclusions in steel normally ≤14μm

and each metallurgy quality index meets the requirement of standard.