X65管线钢焊接接头低温韧性及安全评定的研究

Study on the Low-temperature Fracture Toughness and Safety Assessment of X65 Pipeline Welded Joints

研究了API 5LX65海底管线钢焊接接头的力学性能和低温断裂韧度。采用欧共体提出的SINTAP方法 ,对焊趾处含有表面裂纹的X65管线钢焊接接头进行了安全评定。根据ISO标准 (BS7448) ,以裂纹尖端张开位移(CTOD)作为断裂韧度参量 ,测定了管线钢焊接接头 0℃时的断裂韧度。对于热影响区试样 ,对其进行剖面金相显微组织分析 ,判断裂纹尖端是否落在粗晶区 ,确保试验结果的有效性及可靠性。根据全焊缝拉伸试验结果 ,建立了X65管线钢焊接接头焊缝的一级。

The mechanical properties and low-temperature fracture toughness of API 5L X65 offshore pipeline welded joints were studied. Structure Integrity Assessment Procedure (SINTAP) which is internationally the latest and the most influential safety assessment standard was applied to the API 5L X65 pipeline joints with surface flaw (the height and length are respectively 2.2mm and 5mm) at the weld toe. According to the ISO standard BS7448, the fracture toughness of the welded joints were determined with the crack tip opening displacement (CTOD) as parameter at the temperature of 0℃. For the heat affected zone (HAZ) specimens, microstructure analysis was performed to insure that the tip of the crack was located in the coarse grain zone in order to obtain valid and reliable results. The failure lines of analysis level 1 and 3 of the weld were derived from the tensile test results. The results of the assessment show that all assessment points (Lr , Kr) are located within the failure lines of analysis level 1 and 3. So the pipeline structure is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.