HRB400热轧带肋钢筋脆断原因分析及改进

通过对HRB400热轧带肋钢筋脆断的断口进行化学原位、电镜扫描以及金相组织的检验分析，结果表明：钢筋存在严重的C、P偏析，再加上冬季生产时的轧后冷却速度较快，使钢筋出现大量强度高、塑性低的上贝氏体组织；钢筋局部区域存在的微小裂纹，在受弯的情况下，裂纹处形成应力集中，裂纹会快速扩展；钢筋反复弯曲加工后，降低了钢筋的韧性。这些因素综合作用使得钢筋发生脆断。在此基础上，对钢筋脆断的问题提出了相应的改进措施，HRB400钢筋产品的质量得到了提高，用户使用中基本没有发生脆断的现象。

Cause analysis and improvement of brittle fracture #br# of HRB400 hot rolled ribbed steel bar

The brittle fracture of HRB400 hot rolled ribbed steel bar was inspected and analyzed by the means of chemical in-situ measurement, scanning electron microscopy (SEM) and metallographic structure examination. The results showed that the severe C and P segregation occurred in steel bar. Moreover, due to the rapid cooling rate after rolling in winter, many upper bainite structures with high strength and low plasticity were caused. There were some microcracks in local region of steel bar. In the case of bending, the stress concentration was formed at the cracks, which would expand rapidly. After repeated bending processing, the toughness of steel bar was reduced. These factors resulted in the brittle fracture of steel bar. On this basis, we put forward the corresponding improvement measures to the problem of brittle fracture of steel bar. The quality of HRB400 steel bar products had been improved, the brittle fracture phenomenon of steel bar did not occur in use.