高含硫管道氢致开裂的分形效应及扩展速率计算

氢致开裂是高含硫气田集输管网、长输管网管线钢失效的主要模式之一,为明确管道氢致开裂的机理与过程,对其开裂模式进行了研究。对氢质量浓度在金属裂尖扩展过程中的变化规律进行分析,考虑分形效应的影响,对氢致裂纹的动力学模型进行修正,提出了氢致裂纹扩展的直裂纹-剪切带分形模型:在Gerberich对氢致开裂研究的基础上,基于裂尖的氢化作用与裂纹扩展过程中存在的耦合因素,将断裂过程区的形状与裂纹的扩展长度进行结合,构建了氢致开裂裂纹扩展各阶段分形速率的表达式,得到了更为合理的基于分形效应的氢致开裂数学模型。以材质为16Mn和20钢的天然气管道为例,分别计算了母材与焊缝处的氢致裂纹扩展速率,对比得出两种材料抗H2S的性能,研究结果对于高含硫管道材料的选择具有一定指导意义。

Fractal effect of hydrogen induced crack in high sulfur gathering pipeline and calculation of its propagation rate

Hydrogen induced cracking(HIC) is one of the main failure modes of high-sulfur gas field gathering pipeline network and long-distance pipeline steel. In order to clarify the mechanism and process of pipeline HIC, the cracking mode was studied. The change rule of mass concentration of hydrogen during the propagation of metal crack tip was analyzed, the dynamic model of hydrogen induced crack was corrected with consideration giving to fractal effect, and the straight crackshear band fractal model was proposed for the propagation of hydrogen induced crack. On the basis of Gerberich’s research on HIC, the shape of the fracture process zone and the crack propagation length were combined based on the hydrogenation of crack tip and the coupling factors existing during the crack propagation, the expression of the fractal rate in each stage of the hydrogen induced crack propagation was constructed, and a more reasonable mathematical model of HIC based on the fractal effect was obtained. Taking the natural gas pipeline made of 16 Mn and 20 steel as example, the propagation rate of hydrogen induced crack at the base metal and the weld joint was calculated respectively, and the H2 S resistance of the two materials was obtained by comparison. Therefore, the research results have certain guidance significance for the selection of high-sulfur pipeline materials.