The ulra low carbon bainitic steel ULCB570(0.02C- 1.55Mn-0.62Ni-0.53Cu-0.0035B-0.055V-0.019Ti-  0.028Nb was melted by a 50 kg vacuum induction furnace in laboratory

of which the 25 mm finished plate was rolled from forged 80 mm slab with beginning rolling temperature 1150 ℃

finishing temperature 900 ℃ and air cooling. The continuous cooling transformation curves of deforming austenite was measured by a Thermecmaster-Z thermal simulation machine.  The results showed that the structure of steel deformed with cooling rate 0. 1~30 ℃/s was bainite-ferrite + secondary phase (precipitates);the tensile strength on of steel as rolled condition was 595 MPa

impact toughness A

KV

180 J

of which as rolled + 600 ℃ aged condition the tensile strength σ

b

of steel increased to 610 MPa

impact t

oughness A

KV

to 202 J to meet the requirement for properties of 570 MPa steel plate.