电站锅炉用HR3C钢管表面裂纹临界尺寸

以供货态和650℃(外管壁温度)服役18644 h的HR3C钢炉管为对象,采用实验及模型计算相结合的方法,获得HR3C钢管表面裂纹失稳扩展的临界尺寸,用于定量化评估服役HR3C钢管的可靠性。结果表明,供货态和服役态HR3C钢炉管室温及650℃时的K_IC值分别为16.06、2.38 MPa·m^1/2,以及7.92、1.21 MPa·m^1/2。基于K-判据法,推算出供货态及在蒸气压力为5.72 MPa、650℃下服役18644 h的规格为Ф60 mm×4 mm的HR3C钢管表面裂纹失稳扩展的临界尺寸分别为0.67、0.09 mm。最后,结合显微结构及断口分析,确定了服役态HR3C钢管临界裂纹尺寸减小及服役早期失效的原因。

Critical surface crack size of HR3C steel tube for power station boiler

The critical sizes of crack instability propagation on the surface of the as-received HR3 C steel tubes and that after servicing at 650℃(outer wall temperature)for 18644 h were deduced via a method combining experiment with model calculation,in order to quantitatively evaluate the reliability of the in-service HR3 C steel tubes.The results show that the K_IC values of the as-received and the in-service HR3 C steel tubes at room temperature and 650℃are 16.06 and 2.38 MPa·m^1/2,and 7.92 and 1.21 MPa·m^1/2,respectively.Based on the K-criterion method,the critical surface crack sizes of the as-received HR3 C steel tubes and that after servicing at 5.72 MPa(steam pressure)and 650℃for 18644 h are calculated to be 0.67 and 0.09 mm,respectively.Finally,the reason of the reduction of the critical surface crack size and even early failure of the in-service HR3 C steel tube is determined by the microstructure observations and fracture analysis.