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针对厚规格X80管线钢,采用SEM、EBSD、TEM等方法,研究了不同超快冷终冷温度下厚规格管线钢显微组织演变规律及强韧化机制,并进一步给出了最佳超快冷工艺参数。结果表明,在相同控轧条件下,随着超快速冷却温度由650℃降低至350℃,显微组织经历了由AF+QF+GB+DP向AF+GB的转变,沿厚度方向组织均匀性得到改善,有效晶粒尺寸减小,铁素体板条亚结构细化;当超快速冷却温度为350℃时,沿厚度方向组织均匀性最优,有效晶粒尺寸及板条亚结构尺寸最小,分别为3.83μm及300~900 nm间,材料的主要强化机制为细晶强化与相变强化的综合强化,此时实验钢综合力学性能最优,拉伸、冲击力学性能均满足ASTM A370标准;实验钢轧后超快速冷却最佳工艺参数为:810℃精轧+超快冷至350~400℃+层流冷却至320~360℃+卷取。
For the thick gauge X80 pipeline steel, the microstructure evolution rules and strengthening and toughening mechanism of thick gauge pipeline steel at different ultra-rapid cooling and final cooling temperatures were studied by means of SEM, EBSD and TEM, and the best ultra-fast Cold process parameters. The results show that the microstructure undergoes the transformation from AF + QF + GB + DP to AF + GB with the ultra-rapid cooling temperature from 650 ℃ to 350 ℃ under the same controlled rolling and rolling conditions. When the ultra-rapid cooling temperature is 350 ℃, the microstructure is uniform in the thickness direction, and the effective grain size and the minimum size of the slat substructure are obtained , Respectively 3.83μm and 300 ~ 900 nm, the main strengthening mechanism of the material for the comprehensive strengthening of fine grain strengthening and phase transformation strengthening, the experimental steel at the best mechanical properties, tensile and impact mechanical properties to meet the ASTM A370 standards The optimum technological parameters of super-rapid cooling after experimental steel rolling are: 810 ℃ finish rolling + ultra-fast cooling to 350 ~ 400 ℃ + laminar cooling to 320 ~ 360 ℃ + coiling.