电梯用高强度螺钉断裂分析

某电梯用高强度螺钉在安装2个月后出现批量断裂现象,利用直读光谱仪、氮氢氧联合测定仪、光学显微镜、扫描电子显微镜等对螺钉断裂原因进行了分析。结果表明:该批螺钉由于镀锌后除氢不及时导致其本身氢含量较高和螺钉冷拔后未进行车削导致其在镀锌前表面就已存在大量的微小缺陷,是导致该批螺钉安装后发生断裂的两个主要原因;这些微小缺陷充当了氢陷阱并造成应力集中,在螺钉所受的静拉应力作用下,氢在缺陷处不断富集,最终导致螺钉发生氢致延迟脆性断裂。

Fracture Analysis on High Strength Screws for Elevator

A batch of high strength screws used in elevator fractured after assembling for two months, and the fracture reason was analyzed by using photoelectric direct reading spectrometer, N, H, O joint tester, optical microscopy and scanning election microscopy. The results show that not in time dehydrogenation after galvanization resulted in the high hydrogen content in the screws, and no turning process after cold drawing resulted in the formation of a large number of small defects on the surface of the screws before galvanization. They were the two main reasons for the fracture of this batch of high strength screws. These small defects acted as hydrogen traps and caused stress concentration. With the enrichment of hydrogen in the defects and under the load of static pulling stress, the high strength screws happened hydrogen-induced delayed brittle fracture finally.