Nb微合金化对热轧700 MPa超高强耐候钢组织和性能的影响

试验超高强耐候钢(/%:0.062～0.065C、0.29～0.30Si、1.23～1.27Mn、0.49～0.52Cr、0.19～0.20Ni、0.29～0.31Cu、0～0.20Mo、0.035～0.060Nb)由50kg真空感应炉熔炼,在实验室锻成60mm×60 mm方坯并热轧成4 mm板材,末道次温度880℃,水冷至600℃炉冷。用光学显微镜、扫描电镜、透射电镜和万能拉伸试验机研究了Nb和Nb-Mo微合金化对该钢组织和力学性能的影响。试验结果表明,0.060%Nb钢较0.035%Nb钢晶粒更细,强度提高～70 MPa,但伸长率相同;与未加Mo的0.035%Nb和0.060%Nb钢相比,0.035%Nb-O.20%Mo钢M/A相明显增加,并出现大量贝氏体组织,抗拉强度增加,但屈强比和伸长率降低。

Effect of Nb microalloying on Structure and Properties of Hot-Rolled 700 MPa Super-High Strength Weathering Steel

The test super-high strength weathering steel(/%:0.062～0.065C,0.29～0.30Si,1.23～1.27Mn, 0.49～0.52Cr,0.19～0.20Ni,0.29～0.31Cu,0～0.20Mo,0.035～0.060Nb) is melted by a 50 kg vacuum induction furnace,forged to 60 mm×60 mm billet,then hot rolled to 4 mm plate in laboratory by finishing rolling pass at 880℃, water cooling to 600℃,furnace cooling.The effet of Nb and Nb-Mo microalloying on structure and mechanical properties of steel are studied by optical,scanning electron and transmission electron microscope,and universal tensile testion machine. Test results show that as compared with 0.035%Nb steel the grain size of 0.060%Nb steel is more finer,the strength increases by～70 MPa,but the elongation is the same as that of 0.035 Nb steel;as compared with non added Mo steel(0.035Nb steel and 0.060%Nb steel) the M/A phases in 0.035%Nb-0.20%Mo steel increase obviously and bainite structure occurs in steel led to increase of tensile strength and decrease of yield-strength ratio and elongation of steel.