Abstract: Through experimental detection methods of macro inspection, chemical composition analyzing , mechanic performance testing , micro metallog raphy analyzing and X ray diffraction, the blow out reasons of low - temperature superheatertube were analyzed in the process of boiler operation. The results show that the fracture of a broken tube is a kind of expansion form and a typical ductile fracture, and has instantaneous overheat blow out characteristic under the high temperature. Structure sizes of super heater tubes and inside resistance coefficients as well as imbalance thermal lo ads will result in the rmal deviation. The difference of heated area be tween tubes is very small, so the thermal deviation mainly results from inhomog eneous endo therm and flux . Throughverifying , the reexist strong bonding force oxide attached on inside and outside wall of low - temperature superheater tubes, and ashes are deposited be tween tubes, which result in producing thermal deviation. Once tube wall is overheated, oxidation corrosion rate is not only accelerated , but also the tube performance is rapidly deteriorated. At the same time , low - temperature super heater keeps on running under the high temperature for long time , micro structure appears globular car bide configuration , and bearing capacity of materials at high temperature declines.When tube wall strength can not bear inner steam pressure in the tube , blowout of low - temperature tube occurs.

Key words: Low - temperature supe rheater , Analysis , Blowout

摘要： 　通过宏观检查, 化学成分分析, 机械性能测试, 金相检验和X 射线衍射等试验检测方法, 对锅炉运行过程中低温段过热器管爆裂原因进行了分析。结果表明, 爆管断口为胀开式爆口, 为典型的塑性断口, 具有高温瞬时过热爆管特征。过热器管子结构尺寸、内部阻力系数及热负荷不均匀, 将会产生热偏差。但由于管子之间的受热面积差异很小, 过热器的热偏差主要由于吸热不均匀和流量不均匀造成。经检验, 低温过热器管内、外壁附着结力较强的氧化物, 管间积灰, 导致热偏差产生。一旦管壁过热不仅加速氧化腐蚀速率, 且急剧恶化管材性能。同时,低温过热器长期高温运行, 组织已出现珠光体球化现象, 管材高温承载能力降低。当管壁强度无法承受管内蒸汽压力时, 导致低温过热器管爆裂。

关键词: 　低温过热器, 　分析, 　爆裂