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研究了铌微合金化试验钢控冷过程空冷弛豫温度对其组织和力学性能的影响,结合金相、电镜观察以及XRD技术分析了弛豫过程铁素体组织的演变、基体中的应变诱导析出行为以及组织中的残余奥氏体量变化。结果表明,轧后采用弛豫+超快冷的控冷工艺可以得到含有铁素体、贝氏体和残余奥氏体的多相组织,弛豫终止温度显著影响铁素体晶粒尺寸、铁素体量以及铁素体基体上的沉淀析出量。随着弛豫终止温度的降低,试验钢的屈服强度和抗拉强度呈降低趋势,而屈强比均保持在0.7左右的较低水平。当弛豫终止温度为720℃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30.750 GPa.%的最大值。
The effect of air cooling relaxation temperature on the microstructure and mechanical properties of niobium microalloyed steel during controlled cooling process was studied. The evolution of ferrite structure during relaxation and the strain induced in the matrix were analyzed by metallography, electron microscope observation and XRD techniques. Precipitation behavior and changes in retained austenite volume in the organization. The results show that the multi-phase structure containing ferrite, bainite and retained austenite can be obtained by controlled cooling with relaxation and ultra-rapid cooling after rolling. The relaxation termination temperature significantly affects the ferrite grain size. The iron The amount of ferrite and the volume of precipitation on the ferrite matrix. With the decrease of relaxation temperature, the yield strength and tensile strength of the test steel decreased, while the yield strength of the test steel remained at a low level of about 0.7. When the relaxation relaxation temperature is 720 ℃, the tensile strength, elongation and ductility of the test steel reach the maximum values of 820 MPa, 37.5% and 30.750 GPa.%, Respectively.