中文摘要：

为了分析炉管在长期高温下的损伤情况，选取20钢、304不锈钢和353MA耐热钢三种常用的炉管材料，分别在它们各自的实际使用条件下运行一段时间后取样，利用扫描电子显微镜分析新旧材料的金相组织．研究结果表明，三种炉管在各自的工况下，经长期高温作用后，均发生了一定程度的组织变化．在20钢炉管的微观组织中，珠光体组织产生球化现象，发生轻度损伤；在304不锈钢炉管的微观组织中的奥氏体晶界处有碳化物析出，发生中度损伤；在353MA耐热钢炉管的微观组织中，在奥氏体基础上沿晶界分布着大量的σ相与碳化物，发生严重损伤．

英文摘要：

In order to analyze material damage of furnace pipe under high temperature, differences in microstructure of new furnace pipe and old furnace pipe were tested by SEM. The old furnace pipe had been used for a long time under different temperature. The materials of furnace pipe were 20 steel, 304 stainless steel and 353MA heat resistant steel. The results of the analysis showed that microstructure evolution occurred to both new furnace pipe and old furnace pipe. Minor damage happened with pearlite spheroidization in the microstructure of 20 steel. Moderate damage occurred with carbide eduction on austenitic grain boundaries in the microstructure of 304 stainless steel. And serious damage with large a phase and carbide eduction along austenitic grain boundaries appeared in the microstructure of 353MA heat resistant steel.