多因素耦合作用下膨胀管用新型超细晶中锰TRIP钢相变机制及H2S/CO2腐蚀行为研究

The expandable tubular technology is a significant innovation in the current industry of petroleum and gas engineering. As the oil drilling environment is getting worse, the research and selection of the expandable tubular materials become the main technical bottleneck for its application and development. This project intends to prepare the novel ultrafine-grained medium manganese TRIP steels based on microalloying technology and ultrafast thermal processing in view of the requirement of the expandable tubular which services under extreme environment. The mechanism of transformation induced plasticity is investigated using HEXRD and in-situ TEM techniques under multifactor coupling including downhole temperature, expansion rate and expansion variable, and the martensitic phase transformation model of the medium manganese TRIP steel is constructed during dynamic deformation process at a certain temperature. In this present project, a detained investigation on the dynamic strain aging mechanism and its effect on the martensitic phase transformation behavior of the medium manganese TRIP steel is conducted using 3DAP, first-principles and internal friction technique. The strain hardening behavior and mechanical response characteristics of this steel are investigated during actual expansion process. Furthermore, the corrosion behavior of the designed steel under the environment of H2S/CO2 is studied before and after tube expansion, and the damage mechanism is investigated as well. The correlation is established among alloying composition, processing parameters, microstructures and material performance. The results can improve transformation induced plasticity theory and corrosion mechanism of advanced high strength steel and extend its application in the oil drilling field, and this work will also provide the important scientific reference and theoretical guidance for the expandable tubular materials.

膨胀管是石油天然气工程领域内的重大革新技术，随着钻采环境不断恶化，膨胀管选材成为制约其发展的主要瓶颈。针对极端环境下膨胀管用钢的特点，本项目拟采用微合金化技术与超快速退火工艺设计与制备膨胀管用新型超细晶中锰TRIP钢。利用HEXRD及原位TEM方法探究井下温度-膨胀速率-膨胀率等多因素耦合作用下新型中锰TRIP钢相变效应与增塑机制，构建动态温变形条件下的相变动力学模型。基于第一性原理并结合3DAP及内耗试验揭示中锰TRIP钢动态应变时效机制及对相变效应的影响，明确其实际膨胀过程中的应变硬化行为及力学响应。在此基础上，研究膨胀前后新型中锰TRIP钢H2S/CO2腐蚀性能与腐蚀机理，阐明实验钢腐蚀力学损伤行为，解析合金成分-退火工艺-组织结构-力学性能之间的构效关系。预期研究成果可进一步完善先进高强钢的相变与腐蚀理论，拓展其在石油钻采等领域的应用，为我国膨胀管用钢的开发提供理论基础和科学依据。

膨胀管是石油天然气工程领域内的重大革新技术，随着石油钻采环境不断恶化，高强高塑性膨胀管的选材成为制约其发展的主要瓶颈。本项目基于微合金化技术，并结合轧制与临界退火工艺设计和制备了新型异质结构中锰钢。利用原位EBSD、FIB+3DAP以及球差电镜等先进测试技术，研究了异质结构中锰钢在形变速率（膨胀速率）与形变量（膨胀率）等多因素耦合作用下的相变行为。基于混合强化原理预测了新型异质结构中锰钢的强化行为，揭示了其形变过程中的强化机制，阐明了异质结构诱导（HDI）应力强化、位错强化、细晶强化、析出强化及相变强化等不同强化手段的贡献比例。结果表明，在适当的预应变下（<15%），中锰钢屈服强度与抗拉强度随预应变的增加而显著提高，且仍能保持优异塑性；随着应变速率增加，中锰钢强塑积先增大后降低，在准静态形变条件下，增加形变速率对提升中锰钢的强塑性有利。深入研究表明，对于新型异质结构中锰钢，HDI强化与细晶强化对提高其强度起主导作用；异质结构引发的应力应变配分促使奥氏体在较大应变范围内持续发生相变，对提高中锰钢塑性至关重要，最终建立了实验钢微合金成分-退火工艺-组织结构-力学性能之间的构效关系。在此基础上，研究了异质结构中锰钢的腐蚀性能与腐蚀机理，探究微合金元素添加对其腐蚀行为的影响。结果表明，钢中添加微量稀土Ce在一定程度上提高了中锰钢的耐腐蚀性能，而V的添加对腐蚀性能不利，表面沉积Al/AlN薄膜可显著提升其耐腐蚀性能（提高近2倍）。最终通过轧制与退火工艺的优化，所构筑的异质结构中锰钢的屈服强度大于1000MPa，抗拉强度达1300MPa，同时延伸率高达55%，强塑积接近70GPa﹒%级别。项目研究成果进一步完善高强钢相变与腐蚀理论，拓展其在石油钻采等领域的应用，并为我国膨胀管用钢的开发提供理论基础和科学依据。

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