高强管线钢土壤环境应力腐蚀裂纹尖端非稳态电化学行为与机理

This proposal is focusing on the significant demand of service security of pipeline materials for China's oil and gas storage and transportation constructions. The laboratory simulation methods will be introduced to investigation the electrochemistry in cracking-tip and the crack propagation mechanism of stress corrosion cracking (SCC) of X70 and X80 pipeline steels in typical high pH, near neutral and acidic soil environments in China. The main goal of this project is to demonstrate the key role of the non-steady state electrochemical processes during the SCC occurrence and propagation, and its synergistic effect with the high stress and strain state status,ion concentration and acidification in cracking-tip environments, and to theorize and quantize the contribution of these factors on crack tip electrochemical and crack propagation mechanism. A SCC growth rate prediction model will be established based on the non-steady electrochemical theory in combination with the kinetics of electrode processes, the theory of fracture mechanics and the metal theory, for the two kinds of steel in the soil media in China. The achievement of this proposal will not only directly serve for major oil/gas transportation projects in China, but also for the academic development of corrosion protection theory and techniques, so as to further improve the research ability in this field.

本课题针对我国油气储运工程中对管线材料服役安全性能的重大需求，拟采用试验室模拟方法对X70和X80钢在我国典型的高pH、近中性和酸性土壤环境中的应力腐蚀(SCC)裂尖电化学和裂纹扩展机理开展研究，将围绕非稳态电化学过程在SCC扩展过程中的关键作用及其与裂尖高应力应变状态、离子浓聚及酸化等因素的协同效应，量化解析这些因素在裂尖电化学机理及裂纹扩展过程中的作用，结合电极过程动力学、断裂力学理论和金属学理论，建立两种钢在土壤介质中的SCC扩展速率理论预测模型。本课研究不仅为我国重大工程实际直接服务，而且为学科发展提供创新思路，进一步提升我国相关领域的研究水平。

本课题针对我国油气储运工程中对管线材料服役安全性能的重大需求，围绕X70钢在近中性pH值环境中的应力腐蚀行为与机理，对其裂纹扩展行为进行了研究，探讨了溶液pH值、Cl-浓度、阴极电位、交流干扰、塑性变形及氢等因素对其电化学和应力腐蚀行为的影响，并采用电偶腐蚀的研究方法对应力腐蚀裂纹尖端阳极溶解过程进行了模拟，最后对管线钢近中性pH环境中应力腐蚀裂尖非稳态电化学过程进行了分析。建立了成熟的裂尖非稳态电化学、裂尖高应力应变条件、离子浓聚和介质酸化特征的实验室测试方法和手段，建立综合的裂纹尖端非稳态电化学模拟测试方法，最终提出了综合裂尖新鲜金属表面、裂尖介质环境、裂尖高应变、氢富集等因素的裂尖阳极溶解理论计算公式，为高强度管线钢应力腐蚀防护方法和措施的完善提供了科学依据，为我国重大工程提供了重要技术支撑，具有重要的科学意义和实用价值。