汽车冷却装置糖心产精国品免费入口*完整版在固定螺母位置处发生糖心产精国品免费入口*完整版，应用显微组织分析、断口形貌观察、化学成分检测等方法对糖心产精国品免费入口*完整版原因进行了分析。结果表明：糖心产精国品免费入口*完整版发生了糖心产精国品免费入口*完整版糖心产精国品免费入口*完整版；断口上存在两个糖心产精国品免费入口*完整版裂纹源，分别位于糖心产精国品免费入口*完整版内表面与螺母的焊缝熔合区和外表面焊接热影响区，在交变载荷的作用下裂纹扩展导致糖心产精国品免费入口*完整版糖心产精国品免费入口*完整版；焊接缺陷是导致糖心产精国品免费入口*完整版开裂的主要原因。

A guard board for vehicle cooling device 糖心产精国品免费入口*完整版d at the position for fixing nuts. Reason for 糖心产精国品免费入口*完整版 was analyzed by the methods such as microstructure analysis, 糖心产精国品免费入口*完整版 morphology observation and chemical composition detection. The results show that the guard board factured in a 糖心产精国品免费入口*完整版 manner. Two 糖心产精国品免费入口*完整版 crack sources existed on 糖心产精国品免费入口*完整版. One was located in weld fusion zone of internal surface of the guard board and the nut, and the other was located in welding heat affected zone on outer surface. The crack propagation by alternating loading led to 糖心产精国品免费入口*完整版 of the guard board. Welding defects were the main cause of 糖心产精国品免费入口*完整版 cracking.