Regularities of Changes in the Mechanical Characteristics and Electrical Properties of the Reaction Furnaces Coils Material during Operation

摘要

The main causes of early failure of reaction furnaces coils are diffusion processes in the material as a result of which structural changes occur, new phases are formed and void structure is formed in the surface layers of the metal, which has a negative effect on the mechanical characteristics. In this regard as a structurally sensitive method, which allows evaluating the changes occurring in the metal, the response parameters of the electrical signal are used which are sensitive to pore formation and allow predicting the zone of formation of the breaking crack. Fragments of the coils of the reaction furnaces from the radiant section, which were in operation for 750, 1300, 8000, and 10000 hours and the pipe element in the delivery condition were chosen as the objects of the study. As a result of the research a correlation between the amplitude of the first harmonic of the electrical signal output voltage with the results of static tests for tensile and impact bending was established. This happens due to the fact that during operation there is an increase in the relative impact viscosity and relative tensile strength, and the relative magnitude of the voltage amplitude of the first harmonic of the output electrical signal also increases. These results can be used as a method of mechanical properties assessment by non-destructive testing, and also they can be used to develop a criterion for the rejection of reaction furnace coils.