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裂纹尖端张开位移(CTOD)作为评定海洋工程用钢断裂韧性的重要指标,已广泛应用于现代工业中.根据BS7448:part4标准,采用多式样法对海底管线钢X70进行低温韧度试验,分别建立了焊缝和热影响区的CTOD-R阻力曲线,从而确定了焊缝和热影响区的CTOD启裂值.考虑到铺设之后的安全性问题,采用较小的焊缝CTOD启裂值为参考依据.以此为基础,分别采用SINTAP标准中的一级评定和三级评定对其埋藏裂纹进行安全评估(ECA)考虑铺设环境和残余应力影响,分别得出在铺设条件下的一级评定和三级评定埋藏裂纹容许尺寸.以试验数据为依托,以BS7448和SINTAP规范为理论指导,为海底管线铺设工程中的焊接缺陷验收和拒收提供了依据,为海底管线钢质量的优劣提供参考.
The crack tip open displacement (CTOD) has been widely used in modern industry as an important index to evaluate the fracture toughness of marine engineering steel.According to BS7448: part4 standard, multi-style method was used to test the low temperature toughness of submarine pipeline steel X70 The CTOD-R resistance curve of the weld and heat affected zone was established to determine the CTOD crack initiation value of the weld and the HAZ. Considering the safety problems after laying, the smaller CTOD crack initiation value Based on this, the safety assessment of burial cracks (ECA) was carried out by using the first grade and the third grade respectively in SINTAP standard to consider the influence of laying environment and residual stress to obtain the first grade assessment under laying conditions And three levels to assess the allowable size of buried crack.Based on the experimental data, with the guidance of BS7448 and SINTAP, it provides the basis for acceptance and rejection of welding defects in the submarine pipeline laying project, providing the quality of submarine pipeline steel reference.