水冷壁管爆裂原因分析

对爆裂水冷壁管进行了现场取样，经化学成分分析和力学性能测试，水冷壁管材质符合要求。水冷壁结构分析结果显示，爆裂处的水冷壁鳍片宽度比其他位置的鳍片约大2倍，使该处的水冷壁管壁温度高于其他位置的水冷壁管。水冷壁管显微组织分析表明，其珠光体组织出现轻微球化，弱化了晶界结合力。水冷壁在不同工况下壁温存在波动，交变热载荷将使水冷壁管产生膨胀与收缩，导致水冷壁管承受热疲劳作用。因固定水冷壁膜片的拉筋拘束了水冷壁管自由膨胀与收缩，致使应力增大，导致在薄弱位置萌生热疲劳裂纹。裂纹产生后，在应力的作用下将不断扩展并伴随着水冷壁管壁厚减薄，当裂纹扩展至不能承受内压时产生瞬间爆裂。

LEAKAGE CAUSE ANALYSIS OF BOILER WATER-WALL TUBE

Through chemical composition analyzing and mechanical property testing, the results are showed that the water wall tube is accordance with standard. Structure analyzing shows fin breadth is wider 2 times than that of other parts which makes water wall temperature higher than that of other position. Microstructure analyzing shows slight pearlite globalization which makes granular interface weaker. Water wall temperature fluctuates. Changeable thermal load will makes water wall tube expansion and contraction which makes water wall withstand thermal fatigue stress. Because holding parts which supports water wall tube restrain free expansion and contraction, thus stress increases resulting thermal fatigue cracking on weaker position. After crack forms, it continually expands under stress. Inner pressure assists cracking to expand. When cracking expands to the critical water wall tube thickness, tube thickness can not sustain inner pressure so as to explode instantly.