Effect of Coking Size on the Thermal Diffusion and Stress Distribution of Cr25Ni35Nb and Cr35Ni45Nb Austenitic Steels

Publisher: Trans Tech Publications

E-ISSN: 1662-7482|2015|750|192-197

ISSN: 1660-9336

Source: Applied Mechanics and Materials, Vol.2015, Iss.750, 2015-05, pp. : 192-197

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Abstract

Cr25Ni35Nb and Cr35Ni45Nb austenitic steels, used as furnace tube material in the ethylene pyrolysis furnace, generally suffer from coking during the long operation period. In the present paper, for coked Cr25Ni35Nb and Cr35Ni45Nb austenitic steel, using the finite element ABAQUS code, a sequentially coupled thermal stress procedure was developed to calculate distribution of the temperature and thermal stress field. The results show that thermal diffusion property of Cr25Ni35Nb and Cr35Ni45Nb steel deteriorates obviously with coking layer increasing. Radial bulge and rupture at local field would generate due to excess temperature for applied subsequent measurement. Maximum stress distribute along the cross-section of coking layer and metal matrix. Finally, the critical depth of coking layer of Cr25Ni35Nb and Cr35Ni45Nb austenitic steel are predicted when decoking measurement must be executed.