某风电厂铁塔用紧固高强螺栓在使用一个月后于螺纹处出现多根断裂现象。通过宏观检验、化学成分分析、力学性能试验、金相检验、断口分析等方法对螺栓断裂原因进行了分析。结果表明：失效高强螺栓螺纹处表面全脱碳层深度超标，且脱碳层深度极不均匀，在全脱碳层最大深度处容易产生应力集中，并造成螺栓表面部分区域的强度和抗疲劳性能下降，无法承受设计载荷，从而导致高强螺栓在此处出现应力裂纹并最终发生疲劳断裂失效。

The high strength bolts used for tower fastening in a wind power plant, appeared multiple fracture phenomena at the thread position after a month's use. By means of macro examination, chemical composition analysis, mechanical property test, metallographic examination, fracture analysis and so on, the fracture reasons of the bolts were analyzed. The results show that the surface total decarburization layer depth of the failure high strength bolts at the thread position exceeded the standard requirement, and at the same time the decarburization layer depth was very uneven. Stress concentration easily formed at the deepest total decarburization position, and the decarburization also caused the decrease of strength and fatigue property of the bolts at local positions and made the bolts not bear the design load. So stress cracks appeared here and resulted in the final fatigue fracture failure of the high strength bolts.