对比“高温大变形+超快冷”工艺和传统TMCP工艺，研究了80℃/s超快冷条件下的X70管线钢显微组织演变规律、相变动力学和强韧化机制。结果表明，高温大变形后进行超快冷使晶粒细化，试验钢位错密度提高，析出物弥散细小，改善了试验钢的综合性能。另外，随着终冷温度的降低，韧脆转变温度先降后升，过高终冷温度生成的退化珠光体和过低终冷温度生成的碳化物都弱化了材料的韧性，最终的优化工艺参数为：终轧温度930℃，终冷温度600℃，轧后超快速冷却速度80℃/s。
The microstructural evolution, phase transformation kinetics and strengthening and toughening mechanism of X70 pipeline steel rolled by process of high temperature large deformation and ultra fast cooling were investigated in comparison with traditional TMCP process. It is showed that comprehensive mechanical properties of the tested steel are improved by means of refining grain, increasing dislocation density and refining precipitation in the process of high temperature large deformation and ultra fast cooling. In addition, ductile-brittle transition temperature firstly decreases and then increases with decreasing of finish cooling temperature. Degenerated pearlite resulting from higher finish cooling temperature and carbide from lower finish cooling temperature weaken toughness of the tested steel and optimal specification parameters are as follows: finish rolling temperature being 930℃, finish cooling temperature 600℃ and cooling rate 80℃/s.
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