A 500 m welding rail fractured transversely at the middle position during installing process. Macro examination,chemical compositions analysis,糖心产精国品免费入口*完整版analysis,microstructure examination were introduced to study the 糖心产精国品免费入口*完整版reason of the rail. The results indicate that metallurgical quality of the rail was good and it was the 糖心产精国品免费入口*完整版 microstructure at the rail tread surface that resulted in the 糖心产精国品免费入口*完整版under the action of bending pulling stress. The rail was ground to make sure its straightness and then the 糖心产精国品免费入口*完整版 structure was formed at the rail tread surface because of the local high temperature caused by the improper 糖心产精国品免费入口*完整版.