大型挖掘机斗杆早期失效与钢的动态断裂特性

EARLY FAILURE OF DIGGER AND DYNAMIC FRACTURE CHARACTERISTICS OF THE STEEL FOR HEAVY EXCAVATOR

结合挖掘机实际生产工况，从材料动态断裂特性的研究入手，对国内两种斗杆用钢的使用情况进行了分析。结果表明：材料在动载下抗脆断能力的高低是决定斗杆寿命的重要因素。１５ＭｎＶ钢的韧－脆转变特征对加载速率十分敏感，在模拟挖掘机缓慢撞击大块岩石工况下，其韧－脆转变温度可由原先静载下的－４０℃升至该动载速率下的－１２℃。如果进一步提高加载速率到冲击试验状态，其韧－脆转变温度可升至２２℃以上。而ＨＱ８０钢对加载速率的敏感性较低，即使在冲击试验状态，其韧－脆转变温度仍可达－４０℃。这两种钢在动载特性方面的差异与斗杆在矿山实际使用寿命的差异情况相吻合。

The dynamic fracture toughness in the 15MnV steel and the HQ80 Steel were investigated, which referred the heavy-duty excavator operating characteristic. It was shown that the service life of digger is dependent on its resistance to embrittle fracture at dynamic loading. The characterization of ductile-brittle transition in the 15MnV steel is sensitive to the loading rate. As the digger of the excavator dashed on a rock, the ductile-brittle transition temperature of the steel could be -12℃ rather than -40℃ at static loading. If we further increaced the loading rate, the ductile-brittle transition temperature could be adove 22℃. The sensitivity of the HQ80 steel to the loading rate is quite low. Its ductile-brittle tansition temperature is about -40℃ as charpy impacted loading rate. This difference of sensitivity of dynamic loading rate between the 15MnV steel and the HQ80 steel is consistent with their service life at the mine.