The gear steel 20CrMnTi with narrow hardenability band is produced by hot metal desulphurizing-120 t BOF-LF-200 mm x 200 mm billet casting-hot rolling process at Long Products General Plant

Wuhan Iron and Steel. Production results show that with the process measures including using BOF catch carbon practice to control end [C

]

≥ 0.08%

adding 0.8 kg/t aluminium during tapping for pre-deoxidizing

than argon blowing and feeding aluminium wire 150 m in ladle

during LF refining feeding 0.4 kg/t aluminium wire and controlling refining slag basicity 3.0-4.0

microadjusting alloying element content and argon shielding long nozzle casting process

the results of analysis of 122 heats gear steel 20CrMnTi are (/% ) 0.19-0.21C

0.22-0.31Si

0.85-1.04Mn

1.01-1.19Cr

0.04-0.09Ti

0.02-0.06Cu

≤ 24 X 10

-6

[O

]

and ≤ 55

x 10

-6

[N

]

; the rating of porosity and segregation ≤ l.0 and the rating of grain size ≥ 9.0; and the width of hardenability band △HRC of products ≤ 5.9 to meet the requirement of standard.