通过断口宏观和微观分析、化学成分分析、力学性能试验、金相分析等理化性能试验，对L360M直缝埋弧焊钢管水压爆破试验出现纵向开裂和横向断裂的原因进行了分析。结果表明：钢管纵向开裂和横向断裂主要是由于管体材料韧性较差，钢管材料中铁素体-珠光体带状组织严重则是导致其韧性较差的主要原因，而管材中严重的带状组织与钢中锰含量偏高导致锰偏析有关；建议合理控制锰元素含量，还可以通过降低钢管用板材终轧温度、增加控冷冷却速率、微合金化等措施来降低板材的带状组织级别。

The causes of longitudinal cracking and transversal fracture of a L360M longitudinal submerged arc welding steel pipe during hydraulic burst test were analyzed by macro and micro fracture analysis,chemical composition analysis, mechanical property test, metallographic analysis and other test methods. The results show that the longitudinal cracking and transversal fracture of the steel pipe were mainly caused by the poor toughness of the pipe material which was related to the serious ferrite-pearlite banded structure, and the segregation of element manganese was the main reason for the serious banded structure. Measures such as controlling the element manganese content reasonably, reducing the final rolling temperature, increasing control cooling rate and micro alloying were suggested to reduce the banded structure grade of the steel plate used for making the pipe.