Lengthening, Cracking and Weldability Problems of Fe–Ni–Cr Alloy Tube

Abstract

Ethylene pyrolysis furnace tubes which are made of high Cr-Ni alloys often become difficult to weld after few years in service due to carburization and creep damage. The presence of carburization, often attempted to detect by magnetic permeability, can escape detection due to high Cr-Ni content of the alloy. Based on optical microstructural analysis and supported by scanning electron microscopy, this paper establishes that carburized material becomes difficult to weld due to carburized internal layers of the tube and cause hot shortness. To provide a practical way out for ethylene furnace operators, a solution annealing heat-treatment is recommended to have a successful weld.