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通过热轧试验研究了轧后空冷弛豫时间对铌微合金化热轧TRIP中厚板组织和力学性能的影响,结合光学显微镜、扫描电镜、透射电镜及XRD分析了弛豫过程各组成相的尺寸、含量变化以及铁素体基体上的位错组态和微合金碳氮化物的析出行为。结果表明,采用820℃终轧并弛豫80～120 s后超快冷的工艺可以得到含有铁素体、贝氏体和残留奥氏体的多相组织,弛豫时间显著影响铁素体晶粒尺寸、铁素体量以及铁素体基体上的位错密度和沉淀析出量。随着弛豫时间的延长,试验钢的屈服强度和抗拉强度呈降低趋势。空冷弛豫80 s时,试验钢的抗拉强度、伸长率和强塑积分别达到820 MPa,37.5%和30750 MPa.%的最大值。
The effects of post-rolling air-cooling relaxation time on the microstructure and mechanical properties of TRIP plate in hot-rolled niobium microalloyed steel were studied by means of hot rolling test. The microstructures and mechanical properties of TRIP plate during hot rolling were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and XRD. Size and content, as well as the dislocation configuration on the ferrite matrix and the precipitation behavior of the microalloyed carbonitride. The results show that the multiphase structure containing ferrite, bainite and retained austenite can be obtained by the ultra-rapid cooling after finishing rolling at 820 ℃ and relaxation for 80 ~ 120 s, and the relaxation time significantly affects ferrite crystal Grain size, amount of ferrite, dislocation density on the ferrite matrix, and precipitation amount. With the extension of relaxation time, the yield strength and tensile strength of the test steel decreased. When the air-cooling relaxation is 80 s, the tensile strength, elongation and ductility of the test steel reach the maximum values of 820 MPa, 37.5% and 30750 MPa.%, Respectively.