【摘要】 通过对运行４２０００小时ＨＫ４０炉管的成分，组织和机械性能的测定与观察、发 现晶界碳化物由骨架状变为网链状，其周围有不同宽度的无析出带：二次碳化物明显 粗化：除Ａ５段外均发现少量空洞，个别处已发展成裂纹。以上均以Ｃ段为最严重。 各段均有σ相析出．以块状为主，最多为４．３％．对机械性能无明显影响。持久数据 以Ｃ段为最低，用Ｌ－Ｍ法外推和多元回归法计算．剩余寿命为２００００小时左右。 Ｃ段含碳量低于标准下限，应属废品。含碳量对寿命影响显著，应在寿命预测中 作为重要组织因素，而且应将含碳量标准的下限从０．３５％提高到０．３８％左右。更多还原

【Abstract】 Chemical compositions, structures and mechanical properties of the HK40 steel reformer. furnace tube after more than 42,000 hours operating at about 900℃ are investigated. The experiment results show that the tube has deteriorated after long exposure at elevated temperature and that C6 is most seriously dete- riorated in the whole tube. The observation of the microstructure indicates that the eutectic carbides along the austenitic grain boundary have been translated into network-like carbides and that the secondary carbides within the austenitic grain have becn coarsened obviously and that the holes,which have developed into the fissures in some parts are found in the whole tube except A5. "Mass- like" Sigma phases are formed in the whole tube, but are of no effect on the elevated temperature strength of material obviously,even reaching the maximum value about 4.3% in A5. The elevated temperature rupture strength of C6 is the lowest in the whole tube. After Larson-Miller treatment, the elevated temperature rupture strength of C6 is translated into Larson-Miller parameter P value, which is located below the lower limit of Estruch,B. and Nishino curves. According to the P value extension and calculation, the residual life of tubo is about 20,000 hours. The carbon content of C6 is lower than the standard of that of HK40 steel. So it should be a waste product. The effect of the carbon content on the life of tube is obvious, therefore, it should be regarded as all important structural factor for residual life prediction. The lower limit of carbon content standard of HK40 should be increased from 0.35% to 0.38%.更多还原