Environmentally assisted cracking in linepipe steels

抗环境开裂的管线钢显微组织的设计对于建造可靠的输送酸性气体的天然气输送管道是重要的。 氢致开裂（HIC）和应力腐蚀开裂（SCC）现象涉及源自酸性气体的氢与钢中的杂质（例如非金属夹杂物和沉淀物）之间的相互作用。 生产特殊的“酸性服务”钢，这些钢被合金化以减少氢的吸收，并具有高的内部清洁度。 目前对HIC和SCC引发的精确机制的普遍理解限制了钢铁生产商以更高强度或更低成本开发更有效产品的能力。 拟定的项目计划旨在详细了解HIC和SCC初始阶段所涉及的化学/冶金机制。 将测量原生夹杂物和合成夹杂物附近的微电活动，作为夹杂物和基础钢成分的函数。 与此同时，将评估标准HIC/SCC试验中的散装钢行为，并将其与微电流理解相关联，以根据夹杂物统计预测试验结果。 微观尺度和整体行为之间的这种关系将代表该领域的进步，这将为钢生产商在钢包处理操作中进行有针对性的夹杂物工程提供指导，从而改善HIC和SCC性能。 由于在环境辅助HIC和SCC方面提高了钢的质量，加拿大的增值钢材料的生产和应用将得到加强，从而有利于国内制造活动，并降低加拿大能源分配基础设施运营中与腐蚀有关的长期成本。

The design of linepipe steel microstructures that resist environmentally assisted cracking is important for the construction of reliable gas transmission pipelines that carry sour gas. The phenomena of hydrogen induced cracking (HIC) and stress corrosion cracking (SCC) involve interactions between hydrogen originating in the sour gas and impurities in the steel such as non-metallic inclusions and precipitates. Special 'sour service' steels are produced that are alloyed to reduce the absorption o hydrogen and have high internal cleanness. The current general understanding of the precise mechanisms involved in HIC and SCC initiation limit steel producers' ability to develop more effective products at higher strengths or lower cost. The proposed project plan is designed to provide a detailed understanding of the chemical/metallurgical mechanisms involved in the initial stages of HIC and SCC. Micro-galvanic activity in the vicinity of native and synthetic inclusions will be measured as a function of inclusion and base steel composition. At the same time bulk steel behaviour in standard HIC/SCC tests will be assessed and related to the micro-galvanic understanding to predict test results from inclusion statistics. This relationship between micro-scale and bulk behaviour will represent an advancement in the field that will provide guidance to steel producers for targeted inclusion engineering in ladle treatment operations that will improve HIC and SCC performance. As a result of improved steel qualities in respect of environmentally assisted HIC and SCC Canadian production and application of value-added steel materials will be enhanced so as to benefit domestic manufacturing activities as well as to lower long term corrosion related costs in the operation of Canadian energy distribution infrastructure.