针对某厂少量HRB500热轧带肋钢筋断后伸长率偏低,而且断口上存在肉眼可见白斑的问题，采用扫描电子显微镜(SEM)和高分辨扫描电子显微镜(HRSEM)、X射线能谱仪(EDS)对HRB500热轧带肋钢筋的显微组织、断口形貌和夹杂物进行了分析。结果表明:该钢筋中存在大量非金属夹杂物，其中硬且大尺寸的非金属夹杂物是造成拉伸断口上出现白斑的根源，也是引起钢筋断后伸长率偏低的主要原因;另钢筋显微组织中存在较多的贝氏体也降低了钢筋的塑性和韧性。

Aiming at the problem of the percentage elongation after fracture of a small amount of HRB500 hot-rolled ribbed bars being lower and existing visible flakes on the fracture surface, the microstructure, fracture morphology and inclusions of the HRB500 hot-rolled ribbed bars were analyzed by scanning electron microscope (SEM), high resolution scanning electron microscope (HRSEM) and X-ray energy dispersive spectrometer (EDS) respectively. The results show that there were a large amount of non-metallic inclusions in material of the steel bars, and the hard and large size inclusions were the root for the flakes on the fracture surface and the main reason for the lower percentage elongation after fracture of the HRB500 hot-rolled ribbed bars. At the same time, the more bainite in the microstructure also reduced the plasticity and toughness of the steel bars.