Abstract: The production flow sheet for developed 20 mm low-cost niobium-titanium-boron microalloying low carbon steel plate (/% : 0. 06C, 0. 40Si, 1. 60Mn, 0. 010P, 0. 005S, 0. 050Nb, 0. 012Ti, 0. 002B) is 130 t top and bottom combined blown converter-LF-RH-250 mm slab casting-4300 mill rolling-direct quenching-tempering process. With end rolling ≥ 900 °C, >20 °C./s direct quenching and tempering at 500 ℃ the tensile strength R_m of the 20 mm steel plate is 855 MPa, yield strength R_p 0.2771 MPa, elongation A 16%   impact energy A_KV2 at 0 °C 217 〜238 J and impact energy 4KV2 at -40 °C 137 〜181 J. Tempered structure of the steel is fine bainite lath with width 0. 5 ~ 1. 0μm and there are lots of dispersed 30 ~90 nm Nb + Ti carbo-nitride precipitates.

Key words:  , 800 MPa HSLA Steel, Niobium-Titanium-Boron Microalloying, Steel Plate, Direct Quenching, Tempering, Bainite

摘要： 开发的20 mm低成本铌钛硼微合金化低碳钢板(/%:0.06C、0.40Si、1.60Mn、0.010P、0.005S、0.050Nb、0.012Ti、0.002B)的生产流程为130 t顶底复吹转炉-LF-RH-250 mm板坯连铸-4300轧机轧制-直接淬火-回火工艺。通过终轧≥900℃,以≥20℃/s冷却速度直接淬火,500℃回火,20 mm钢板抗拉强度R_m为855 MPa,屈服强度R_p 0.2771 MPa,延长率A 16%,0℃冲击功A_kv2 217～238J, -40℃ A_kv2 137～181J。该钢的回火组织为细小的贝氏体板条,宽度为0.5～1.0μm,并有较多弥散分布的30～90 nm Nb+Ti碳氮化物析出。

关键词: 800 MPa低合金高强钢, 铌-钛-硼微合金化, 钢板, 直接淬火, 回火, 贝氏体