采用宏观观察、化学成分分析、力学性能测试、金相检验及断口分析等方法对某2 MW风电机组塔筒基础环35CrMo钢高强螺栓的断裂原因进行分析。结果表明：断裂螺栓表面碳含量远低于标准要求；螺纹表面存在明显的脱碳层组织，且螺栓表面显微硬度不符合标准要求；螺纹牙根表面脱碳严重，导致螺栓表面硬度和力学性能降低，并在螺纹根部引起较大的组织应力集中，使应力集中位置的螺纹牙根部脱碳层的晶界弱化区萌生微裂纹，内部夹杂物含量过高促进了裂纹扩展，最终导致螺栓疲劳断裂。建议加强对高强螺栓材料的性能和制造质量的监督检验。

The fracture causes of 35CrMo steel high strength bolts in the tower foundation ring of a 2 MW wind turbine were studied by means of macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination and fracture analysis. The results show that the carbon content on the surface of the fracture bolt was far below the standard requirement; there was an obvious decarburization layer on the thread surface, and the micro-hardness of the bolt surface did not meet the standard requirements.The serious decarburization on the root surface of the thread tooth led to the decrease of the surface hardness and mechanical properties of the bolt, and led to a large concentration of organizational stress at the root of the thread, which caused the initiation of microcracks in the grain boundary weakening zone of the decarburization layer at the root of the thread tooth at the stress concentration position. The excessive content of internal inclusions promoted the crack propagation, and finally led to the fatigue fracture of the bolt. It was suggested to strengthen the supervision and inspection of the performance and manufacturing quality of high strength bolt materials.