某超临界锅炉TP347HFG奥氏体不锈钢高温过热器发生爆管事故，通过宏观观察、化学成分分析、金相检验及力学性能试验等方法，对该高温过热器管的爆裂原因进行了分析。结果表明：该高温过热器管发生了脆性断裂。由于管屏上部集箱内的节流孔尺寸偏小，与设计图纸不符，导致管道内水介质流量偏小，冷却效果差，管壁长期在超温环境中服役。而该钢长期高温运行会在晶界处析出大量的σ相，此外细小的晶粒也促进了σ相的生成，导致材料快速发生老化，降低了高温强度，最终导致爆管。

The tube burst accident occurred in the TP347HFG austenitic stainless steel high temperature superheater of a supercritical boiler. The causes of the tube burst were analyzed by means of macro observation, chemical composition analysis, metallographic examination and mechanical property test. The results show that brittle fracture occurred in the high temperature superheater tube. Due to the small size of orifice in header at the upper of tube panel, which was inconsistent with design drawing, causing the water medium flow in the tube was too small, the cooling effect was poor, and the tube wall serviced in over temperature environment for a long time. However, the steel precipitated a lot of σ phase at the grain boundary due to long-term high temperature operation, and the fine grains also promoted the formation of σ phase, which led rapid aging of material and reduced the high temperature strength, finally led to tube burst.