大型管式燃料加热炉是石油化工企业里广泛应用且必不可少的重要设备，其中炉管的失效大多由渗碳引起。为了评价声发射技术在渗碳层厚度检测中应用的有效性，对规格为 70 mm×6 mm的HP40Nb裂解炉炉管进行了试验。试验时，主要考虑了不同渗碳时长引起的组织变化、磁场变化及各种附加应力对声发射信号的衰减响应规律。结果表明，短时间的强渗碳作用下，裂解炉炉管的材料组织、磁场强度等会发生变化，但对声信号的衰减不会产生明显的影响。

Large tube type fuel heating furnaces are important and essential equipments, which have a wide range of applications in the petroleum and chemical industry, and failure modes of the furnace tubes in them are mostly caused by carburizing. It is important to improve effective detection technology for the measurement of the tube carburized layer thickness, as well as the research on the comprehensive performance of furnace tubes considering the impacts of different conditions. The cracking furnace tube of  70 mm×6 mm HP40Nb specifications was studied to evaluate the effectiveness of an acoustic emission(AE) technique, which used to measure the carburized layer thickness. In experiment, different carburizing time factors were mainly taking into account, and the response of acoustic emission attenuation to the organization changes, the magnetic field changes, and additional stress which caused by carburization are considered. The results show that the short periods strong carburizing has obviously impacts on the changes of the organization and magnetic field of the cracking furnace tube. It however, has little contribution to the acoustic emission signal attenuation.