某钢网架厂房中的高强螺栓在使用过程中出现早期断裂现象。采用宏观检验、化学成分分析、硬度测试、扫描电镜及能谱分析等方法，对螺栓断裂的原因进行了分析。结果表明：该高强螺栓断裂主要是由于其内部存在冶金缺陷及热处理工艺不当；在承载力作用下，存在较多夹渣缺陷的螺栓心部产生应力集中并萌生裂纹，同时不良的调质热处理组织增加了螺栓的脆性，从而导致了螺栓的快速脆性断裂。最后提出了相应的预防措施。

A high-strength bolt for steel grid structure fractured early during use. Base on macroscopic inspection, chemical composition analysis, hardness testing, scanning electron microscope and spectrum analysis and so on, the fracture reasons of the bolt were analyzed. The results show that:the fracture of the bolt was mainly caused by the presence of metallurgical defects and inadequate heat treatment technology; under the action of the load, the stress concentration was produced in the center of the bolt with a large number of slag inclusions, then crack source appeared in the region of the stress concentration; meanwhile, the poor tempering heat treatment structure increased the brittleness of the bolt, and ultimately resulted in the rapid brittleness fracture of the bolt. Finally the corresponding preventive measures were put forward.