Nb(C,N)纳米析出相对X80管线钢深海应力腐蚀的影响规律及机理研究

At resent, the pipeline steels with high strength for transporting oil and natural gas in deep ocean are preduced by the technology of microalloying united with controlling rolling and cooling, and through the mechanism of precipitation strengthening and thinning crystal grain by nanoscaled microalloy carbides or nitrides. The stress corrosion cracking (SCC) is the primary type of the high stress pipeline failure. But so far, there are few reports on the mechanism of the effect of nanoscaled compounds precipitation of microalloys on SCC of the high strength pipeline steels in deep ocean. This project plan to research X80 steel strengthened and toughened by nanoscaled Nb(C,N) precipitation particles. In the condition of deep ocean with the multi-coupling of stress, high hydrostatic pressure, oxygen concentration, temperature, salt concentration, etc., the effects of quantity, size and distribution of the nanoscaled precipitated particles on the adsorption, diffusion and trapping process of hydrogen, and the critical cracking stress of SCC will be reseached by utilizing simulated ocean environment, electrochemistry, mechanics, electron microscope, numerical calculation simulation and so on. The comprehensive corrosion mechanism will be revealed, and the optimized criterion on microstructure and anti-corrosion performance for evaluating and selecting pipeline materials for using in deep ocean will be provided.

目前利用微合金化和控轧控冷技术，通过微合金元素的碳/氮化合物的纳米析出强化及细化晶粒作用生产高强度管线钢，用于建造高性能的深海油气输送管线。应力腐蚀开裂是高压油气管线破坏的主要形式之一，而高强度管线钢中微合金化合物纳米析出相对深海环境下应力腐蚀的影响规律及机理的研究鲜有报道。本项目拟以含有纳米尺度的Nb(C,N)化合物析出强韧化相的X80级高强度管线钢为研究对象，通过模拟海洋环境，利用电化学、力学、电子显微分析、数字计算模拟等方法，研究在深海状态的应力、高静水压力、溶氧量、温度、盐度等耦合条件下，高强管线钢中微合金元素纳米尺度化合物析出相的数量、尺寸和分布对应力腐蚀时氢的吸附和扩散、氢的陷阱作用以及钢发生应力腐蚀开裂的临界应力等的影响，揭示其作用规律和机理，为深海管线钢的材料评价和选择，在耐蚀性能方面提供更细致更优化的微观参考指标。

本项目针对我国高性能深海油气输送管线建造中对管线钢材料评价和选择的重大需求，以含有纳米尺度的Nb(C,N)化合物析出强韧化相的X80级高强度管线钢为研究对象，通过模拟海洋环境，利用电化学、力学、电子显微分析等方法，研究了在深海状态的应力、高静水压力、溶氧量、温度、盐度等耦合条件下，高强管线钢中微合金元素纳米尺度化合物析出相的数量、尺寸和分布对氢的吸附和扩散、氢的陷阱作用以及钢发生应力腐蚀开裂的行为与机理的影响。得到了不同分布状态的Nb(C,N)纳米析出相对氢致开裂行为以及在深海耦合环境下钢的电化学腐蚀和应力腐蚀行为的影响规律和机理。本项目为深海管线钢的材料评价和选择，在耐蚀性能方面提供了更细致更优化的微观参考指标，具有重要的科学意义和实用价值。