锅炉屏式再热器TP304H管裂纹分析

由于热偏差和蒸汽流量偏差等原因,HG-1025/18.2型锅炉屏式再热器右下方管壁温度较高,内壁氧化皮的剥落进一步提高了管壁温度。运行约3.5万h后,TP304H奥氏体耐热钢制屏式再热器管析出了大量碳化物和σ相,导致管材低周疲劳强度和蠕变强度降低。管材在运行中遭受吹灰蒸汽的热冲击,外壁因此出现热疲劳裂纹,随后内壁金属衍生出蠕变裂纹。

Crack Analysis of Boiler Pendent Reheater Tubes Made of SA213-TP304H Steel

Due to the heat deviation and steam flow deviation, there existed a high tube temperature area at right lower part of pendent reheater in a HG-1025/18.2 type boiler. Exfoliation of oxide scale on inner surface made further improvement on tube temperature. After running about 35,000 hours, the pendent reheater tubes made of SA213-TP304H Austenitic heat-resistant steel precipitated numerous carbides and σ phases, which led to decreasing low cycle fatigue strength and creep strength. Because the pendent reheater tubes were subjected to thermal shock of steam blown by a sootblower during service, the thermal fatigue crack on outside surface was caused, and the creep crack adjacent to inner surface subsequently appeared.