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采用金相检验、化学分析、力学性能和扫描电镜对某钢厂锅炉顶棚过热器管爆裂原因进行了分析。结果表明,过热器长期过热导致管胀粗、局部减薄,最终形成裂纹。由于裂纹引起泄漏,使回路其余段内冷却工质的流量减小,导致泄漏处的下游发生短时过热爆管,出现大破口。锅炉短期使用的情况下爆管,且显微组织严重球化,证明失效过热器运行时内管壁温度远远超过额定温度318℃,20G钢安全余量不足是导致爆管的主要原因。
The metallurgical test, chemical analysis, mechanical properties and scanning electron microscopy (SEM) were used to analyze the causes of the burst of superheater tubes on the roof of a steel mill boiler. The results show that long-term overheating superheater lead to thick tube expansion, local thinning, the final formation of cracks. Leakage caused by cracks, so that the rest of the circuit cooling fluid flow decreases, leading to leakage at the downstream short burst overheating, a large breach. When the boiler was used for a short time, the tube exploded and the microstructure became spheroidized. It was proved that the tube wall temperature in the operation of the failed superheater far exceeded the rated temperature of 318 ℃. The shortage of safety margin of 20G steel was the main reason for the tube explosion.