The metallurgical process flow sheet for U71 Mn heavy rail steel ( % : 0. 66 ~0. 76C

0. 15 ~0. 35Si

1. 10 - 1. 40Mn

≤0.03OP

≤030S) is 100 t converter-LF (VD) -280 mm x 380 mm bloom continuous casting. The [N

]

of each procedure from converter to tundish and effect factors

and the effect nitrogen content on mechanical properties of rail steel have been studied. Results show that with increasing nitrogen content in steel from 54 x 10

-6

to 94 x 10

-6

the fracture toughness of rail decreases from 34. 7 〜38. 1 MPa mi

1/2

to 28. 1 -31.5 MPa ml/2. During LF refining

as recarburizing agent anthracite is used to replace original asphalt coke

it is available to control nitrogen content in steel ≤64 x 10

-6

the average nitrogen content is 50. 9 x 10

-6