The steel 40MnB is produced by 50t EAF-LF(VD) process at Special Steel Plant

Laiwu Steel.Results showed that with insuring refining slag basicity 3.0～5.5

feeding Al wire

then feeding silicon-calcium wire in LF refining end phase

skimming and 50 Pa VD treated for 35~40 min

after VD feeding Al wire and titanium wire

and inserting ferroboron FeB

20

C

0.5

-A cladding of aluminium sheet into liquid steel and soft argon blowing

the yield of boron of ferroboron was 65%~75%

boron content in steel was 0.0018%～0.0025%

and oxygen content and nitrogen content in steel were respectively ≤20×10

-6

and ≤80×10

-6

.