X90螺旋埋弧焊管焊缝横向裂纹分析

为了提高X90螺旋埋弧焊管的焊缝质量，推动其工程服役的快速发展，对X90螺旋埋弧焊管的焊接接头以及焊缝横向裂纹进行了金相分析，并对横向裂纹的产生原因进行了分析与讨论。焊缝横向裂纹显微形貌和能谱检验结果表明，在焊接工艺不稳定情况下，制管工序中焊缝承受的多种拉应力叠加后作用于焊缝内残留焊剂部位，导致该部位的拉应力超越材料强度极限引发裂纹萌生和扩展；横向裂纹在纵向截面上起源于焊缝中的残留焊剂，由内焊缝向外焊缝扩展，而其在水平截面上由焊缝向母材扩展；随着远离起裂源点，裂纹断口形貌呈现由准解离断裂向解离断口渐变，整体表现出脆性断裂特征。

Analysis on Transverse Crack in Weld of X90 SAWH Pipe

In order to increase the weld quality of X90 SAWH pipe, and promote the rapid development of engineering service, in this article, it conducted metallographic analysis for X90 SAWH pipe welded joint and the transverse crack in weld, furthermore, the causes of transverse crack were analyzed and discussed. The results of weld transverse crack microstructure and energy spectrum test results showed that, in the case of welding process was not stable, the superposition of a variety of tensile stress in pipe-making process acted on weld residual flux, which caused the tensile stress exceeded material strength limit, led to crack initiation and extension; the transverse crack originated from residual flux in longitudinal section from inner weld to outer weld, while it extended from weld zone to base metal in horizontal section;the morphology of cracks showed brittle fracture character, which transformed form quasi-cleavage to cleavage as long with the increasing distance from crack source.