环焊接头强度对高应变海洋管道轴向承载能力的影响

Influence of strength of girth welded joints on axial bearing capacity of high strain submarine pipeline

基于应变设计的油气输送管道,环焊接头的强度对管道轴向变形能力起着至关重要的作用。以OD559×31.8 mm L485高应变海洋管道环缝为研究对象,采用有限元方法和数字图像相关法(DIC)拉伸试验及宽板拉伸试验,研究了GMAW环焊接头不同区域的强度变化对管道轴向承载能力的影响。结果表明,随焊缝金属强度的升高,管道轴向极限载荷和轴向平均应变增大,失效位置由焊缝向热影响区和母材转移;根焊金属占比小,热影响区很窄,高强匹配时根焊金属和热影响区强度对管道轴向极限载荷和轴向平均应变影响较小;在轴向载荷下,低强匹配环焊接头的母材、热影响区和焊缝的轴向应力和轴向应变分布极不均匀。受母材的拘束作用和焊缝金属自身的形变强化,低强匹配焊接接头的抗拉强度高于全焊缝金属,但变形和屈服主要集中在焊缝区域,容易导致管道环焊缝断裂失效。

For oil and gas pipeline based on strain design,strength of girth welded joints plays an important role in the axial deformation capacity.Finite element method,digital image correlation(DIC)tensile test and wide plate tensile test were used to study influence of strength changes in different regions of GMAW girth welded joints on the axial bearing capacity of high strain submarine pipeline with size of OD559×31.8 mm and grade of L485.The results showed that with the increase of strength of weld metal,the axial limit load and axial mean strain increased,and the failure position shifted from weld to heat affected zone(HAZ)and base metal.Due to small proportion of root welding metal and narrow HAZ,strength of root weld and HAZ had little influence on the axial ultimate load and axial average strain of pipeline in the case of overmatching.Under axial load,distribution of axial stress and axial strain in base metal,HAZ and undermatched weld was very uneven.Due to restraint effect of base metal and deformation strengthening of weld metal itself,tensile strength of undermatched welded joints was higher than that of all-weld metal,but deformation and yield were mainly concentrated in the weld,which easily led to failure of girth weld of pipeline.