Abstract: The 30~40 mm medium plate of HQ590DB ultra-low carbon bainitic steel - 0.05C- 1.5Mn-0.04Nb- 0.02Ti-≤0.0002B has been pilot-produced by 180 t converter- RH - LF (Ca treated)- concasting slab:230(300)mmx1650mm×6000 mm-4300 mill controlled rolling and cooling process. [H] in concasting slab was 1.7×10-⁶,[O] 21 ×10~⁶ and[N]29×10-6.With controlled finishing rolling temperature between 800 and 850 ℃ and cooling temperature between 590 and 630 ℃, the structure of ferrite + lath bainite was obtained, the tensile strength σ_b of plate was 650～690 MPa, yield strength σ_0.2 490~590 MPa, elongation δ₅ 20%, and the plate has excellent formability.

摘要： 采用 18 0t转炉 RH LF(Ca处理 ) 连铸坯 (mm) :2 30 (30 0 )× 16 5 0× 6 0 0 0 4 30 0轧机控轧控冷工艺试制了HQ5 90DB超低碳贝氏体钢 (% ) :0 0 5C ,1 5Mn ,0 0 4Nb ,0 0 2Ti,≤ 0 0 0 0 2B的 30～ 4 0mm中板。连铸坯的 [H]1 7× 10^-6 ,[O]2 1× 10 ^-6,[N]2 9× 10^-6 。终轧温度 80 0～ 85 0℃ ,控制终冷温度 5 90～ 6 30℃ ,获得铁素体+板条状贝氏体组织 ,钢板抗拉强度σ_b6 5 0～ 6 90MPa ,屈服强度σ_0.2 4 90～ 5 90MPa ,延伸率δ₅ 2 0 % ,并具有良好的成形性能。