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采用TMCP热轧及轧后两阶段控制冷却技术,在试验室制备了含Mo成分的X80级抗大变形管线钢,并利用扫描电镜和透射电镜等分析方法研究了不同冷却条件对组织与性能的影响.结果表明,采用两阶段控制冷却工艺的含Mo成分X80抗大变形管线钢为铁素体-贝氏体双相组织;随加速冷却中开冷温度降低,组织中铁素体含量增加,试样强度降低,屈强比降低,均匀伸长率提高;随加速冷却中终冷温度降低,贝氏体中M/A含量减少,尺寸更细小,分布更分散,试样强度变化不大但均匀伸长率显著提升.分析表明,当铁素体含量一定时,均匀伸长率与贝氏体中M/A密切相关,细小且均匀分布的M/A可提高加工硬化速率,推迟颈缩发生,使均匀伸长率升高.当加速冷却中开冷温度为690℃、终冷温度为450℃时,组织中铁素体的体积分数约为23%、晶粒尺寸约为5μm,M/A岛尺寸约为1μm,组织均匀性良好,试样得到最优的强度塑性匹配.
Using TMCP hot rolling and post-rolling two-stage controlled cooling technology, X80 grade large strain pipeline steel with Mo content was prepared in the laboratory. The effects of different cooling conditions on microstructure and properties were studied by using scanning electron microscopy and transmission electron microscopy. .The results show that the X80 steel pipe containing Mo, which is controlled by the two-stage controlled cooling process, is a ferrite-bainite dual-phase structure. With the decrease of the cooling temperature in the accelerated cooling, the content of ferrite in the structure increases The strength decreases, the yield ratio decreases and the uniform elongation increases. With the decrease of the final cold temperature in accelerated cooling, the content of M / A in bainite decreases, the size is smaller and the distribution is more dispersed. The results show that when the content of ferrite is constant, the uniform elongation is closely related to the M / A ratio in bainite. The small and uniform distribution of M / A can increase the work hardening rate and delay the occurrence of necking , So that the uniform elongation increases.If the cooling temperature is 690 ℃ and the final cooling temperature is 450 ℃, the volume fraction of ferrite in the microstructure is about 23% and the grain size is about 5μm, the M / A Island size of about 1μm, good tissue uniformity, the sample is the most Strength and plasticity matching.