Classification of Primary Carbides in Ethylene Pyrolysis Furnace Tubes and the Effects on High Temperature Rupture Performance

doi:10.3901/JME.2018.08.109

Abstract

Abstract: For centrifugally cast 25Cr35NiNb+microalloy and 35Cr45NiNb+microalloy furnace tube, the morphology, distribution and type of primary carbides in original as-cast microstructure are analyzed by optical microscope and scanning electron microscope, and the high temperature rupture tests are carried out by using high temperature creep testing machine. The metallographic results show that the morphology of primary carbides in centrifugally cast furnace tube material can be divided into normal type, which refers to skeletal or fine strip Cr carbide + short rod or granular NbC in grain boundary, and abnormal type, which refers to cluster shape or fine granular or dash-dotted line like Cr carbide + cluster NbC (or G phase) in grain boundary. The high temperature rupture test results under the condition of 900-1 100℃ and 12-45 MPa stress level show that the rupture time of furnace tubes with normal type primary carbides are longer than those of abnormal type. Finally, the reference maps of normal type and abnormal type microstructure are offered to quickly estimate the high temperature performance of furnace tubes.

Key words: ethylene pryolysis furnace tube, high temperature rupture performance, original as-cast microstructure

CLC Number:

TB31

CHEN Tao, CHEN Xuedong, LIU Chunjiao, QIAN Bing. Classification of Primary Carbides in Ethylene Pyrolysis Furnace Tubes and the Effects on High Temperature Rupture Performance[J]. Journal of Mechanical Engineering, 2018, 54(8): 109-116.

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