采用光学显微镜、扫描电镜和X-射线能谱仪,对热煨弯管过程中外弧拉伸区出现的横向裂纹进行了研究。管线钢具有针状铁素体(AF)和粒状贝氏体(GB)组织,弯管工艺对弯曲段整体和局部的力学性能无明显影响;铸坯加热过程中Cu的富集弱化晶界强度,弯管过程中外弧拉伸区产生最大的拉伸应变,一起导致了裂纹产生。 The transverse cracks occurred in the outer arc stretching zone during hot simmering were studied by optical microscope, scanning electron microscopy and X-ray energy dispersive spectroscopy. The pipeline steel has acicular ferrite (AF) and granular bainite (GB) structure. The bending process has no obvious effect on the overall and local mechanical properties of the curved section. The enrichment of Cu in the slab heating weakens the grain boundary strength During the bending process, the maximum tensile strain is generated in the outer arc stretching zone, which leads to the crack generation.