主蒸汽母管裂纹原因分析与处理

CAUSE ANALYSIS AND TREATMENT OF CRACKS IN MAIN STEAM PIPE

通过梳理、总结近几年主蒸汽管道产生裂纹的部位及整改措施,并借助理化检验、电镜观察等技术手段做进一步分析,确认主蒸汽母管裂纹为再热裂纹,产生原因是由于管道在焊接过程中线能量较大,热影响区粗晶区晶粒严重长大,在随后的热处理过程中,由于回火温度不足,致使热影响区硬度偏高,且主蒸汽母管长期运行在再热裂纹敏感温度范围区间,在应力集中的部位发生了再热裂纹开裂。针对上述原因,在后续检修过程中采取了有针对性措施加以处理,消除了安全隐患。

The location of cracks in the main steam pipe and the corrective actions taken in recent years were reviewed and summarized,and further analysis was carried out with the help of such technical means as physical and chemical inspection and electron microscope. It was confirmed that the cracks in the main steam pipe is reheat crack. The high heat input of pipes during welding led to the serious grain growth in coarse grain heat affected zone, the insufficient tempering temperature resulted in relatively high hardness in the heat affected zone during the subsequent heat treatment,and the main steam pipe was operated within the range of reheat crack sensitivity temperature for a long period of time,so reheat cracks occurred in stress concentration areas. To solve these problems, some targeted measures were taken during the follow-up maintenance to eliminate safety hidden troubles.