厚规格X70管线钢落锤撕裂试验性能分析

Analysis of DWTT property of thick X70 pipeline steel

通过金相显微镜、扫描电镜、电子背散射衍射技术对不同工业生产轧制工艺下,不同厚度规格、不同轧制压缩比的X70管线钢的显微组织进行分析,对比其原始奥氏体组织差异,研究了压缩比对原始奥氏体组织的影响。结果表明：轧制过程中大压缩比更有利于细化奥氏体晶粒,提高厚规格X70管线钢低温韧性。但由于精轧过程温度较低无法将变形渗透至中心,因此需进一步借助粗轧过程中的低温阶段进行变形渗透。轧后超快冷冷却可以提高该钢种落锤撕裂试验（DWTT）性能,但不足以弥补前期奥氏体晶粒细化不足而带来的DWTT性能波动。

The microstructures of X70 pipeline steels with different thickness specifications and different rolling reduction ratios were analyzed by metallographic microscope,scanning electron microscope,and electron backscatter diffraction techniques,and the original austenite microstructures were compared.The effect of compression ratio on the original austenite structure was studied.The results show that the large compression ratio in the rolling process is more conducive to refine austenite grains and improve the low-temperature toughness of thick X70 pipeline steel.However,due to the fact that the temperature during the finish rolling process is too low to permeate the center of the deformation,it is necessary to further use the low-temperature stage of the rough rolling process to perform deformation infiltration.Ultra-rapid cold cooling after rolling can improve the DWTT performance of the steel,but it is not sufficient to compensate for the fluctuation of DWTT performance caused by insufficient early austenite grain refinement.