某铁路道岔转辙机的连杆使用不到3a发生了断裂，采用宏观形貌观察、化学成分分析、金相检验、断口分析及硬度测试等方法对其断裂原因进行了分析。结果表明：其断裂性质为高周疲劳断裂；连杆裂纹起源于连杆直径变化位置的应力集中处，该处未经感应淬火处理，且材料中非金属夹杂物含量较高，并存在组织偏析等缺陷，从而使其疲劳强度下降，在交变应力作用下，裂纹扩展，最后导致连杆发生高周疲劳断裂。
A railway turnout switch connecting rod braked after using for less than 3 years, the fracture reasons were analyzed by means of macrograph observing, chemical composition analyzing, metallography examinating, fracture analyzing and hardness testing. The results show that the fracture characteristic was high cycle fatigue fracture. The connecting rodr s cracks originated from stress concentration position, where the connecting rod＇s diameter changed and did not treated by induction quenching, and the content of non-metallic inclusions was fair high and the microstructure segregation was found, so that the fatigue strength of the connecting rod decreased. The fatigue cracks extended and caused the connecting rod happening high cycle fatigue fracture under the action of alternating stress.
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