Abstract: The production flowsheet for V-Nb-Ti microalloying S355NL large size seamless tube for low-temperature structure (/% ： 0.14~0.15C, 0.29~0.30Si, 1.35〜1.37Mn, ≤0.014P, ≤0.005S, 0.02~0.03Nb, 0.06~0.07V, 0.010~0.020Ti, 0.39~0.41 C_eq) is 100t EAF-LF-VD-feeding Ca wire-φ400 mm round bloom casting- 3-roll mill trainnormalizing treatment at 940 °C for 30 min, air cooling. The statistic results of 16 heats and batches show that with the process measures including adding silicon -manganese and fenrrosilico-aluminium alloy in tapping of EAF, using CaO-SiO₂- Al₂O₃ slag series and whole process argon blowing in LF refining, VD treating for 20~25 min, using long nozzle and argon blowing in casting process, the object quality and properties of steel tube are constant with uniform structure and fine grains, and the each property index meets or exceeds the technical requirement of standard and the purchaser, i. e. yield strength R_eH 380~435 MPa, tensile strength R_m 522~605 MPa, elongation A 24%~29% and impact energy at -50℃ 132~237 J.

Key words: 100t EAF-LF-VD-Round Bloom CC Flowsheet, φ406 mm x 15 mm S355NL Steel Tube, -50℃, V-Nb-Ti Microalloying, Normalizing Treatment

摘要： V-Nb-Ti微合金化S355NL大口径低温结构用无缝管（/%:0.14~0.15C，0.29~0.30Si，1.35~1.37Mn，≤0.014P，≤0.005S，0.02~0.03Nb，0.06~0.07V，0.010~0.020Ti，C_eq 0.39~0.41）的生产流程为100t EAF-LF-VD-喂Ca线-φ400 mm圆坯连铸-3辊连轧机组-940℃ 30 min空冷正火处理。16炉批统计结果表明,通过EAF出钢加硅锰、硅铝铁合金,LF采用CaO-SiO₂-Al₂O₃渣系，全程吹氩，VD处理20~25 min，连铸长水口和吹氩等工艺措施,钢管的实物质量和性能稳定，组织均匀，晶粒细小，各项性能达到或超过了标准和用户的技术要求：屈服强度R_eH380~435 MPa，抗拉强度R_m522~605 MPa，伸长率A 24%~29%，-50℃冲击功132~237 J。

关键词: 100t EAF-LF-VD-圆坯 CC 流程, φ406 mm x 15 mm S355NL 钢管, -50℃, V-Nb-Ti 微合金化, 正火处理