乙烯裂解反应管的渗碳损伤及其原因分析

Carburization Damage and Reason Analysis on Ethylen Cracking Furnace Tube

通过对实际进行中的裂解反应管的解剖分析和模似实验,探讨了反应管的损伤型式和损伤原因。提出渗碳和热疲劳的联合作用是引起反应管内壁开裂的主要原因。渗碳层中奥氏体基体Cr 含量显著下降,引起耐热钢抗氧化能力下降,从而造成管内壁粉化,在反应介质的冲刷下,管壁减薄乃至穿孔。由于厚壁弯管常处于炉膛边缘,对炉温变化较敏感,因此易于遭受热疲劳损伤。

Through failure analysis of ethylen cracking furnace tubes which had used for eight years and simulation test in laboratory,the damage pattern and reason of the cracking tubes are investigated.The results show that carburization and thermal fatigue acting simultane- ously is basic reason which leads to the straight cracking tube to crack on inside wall.Especially carburization induces interstress in the tube wall dus to there are different specific volume and thermal expension coefficient in the carburization and non-carburization layers as a result,the cracking tude is subjected to creep and thermal fatigue at same time.In addition,carburization spoils the abiiity of resistance corrosion at high temperature due to a large number of carbides are formed in the carburization layer,which reduces the chromium content of the alloy matrix.Under the process (?) washing out the tube wall become thiner and thiner until a hole is formed on it. The bend tubes usually have thicker wall and are situated in the side of combustion chamber there temperature is changed frequently,and they are mainly subjected to thermal fatigue dama- ge.