Microstructural and mechanical characterization of postweld heat-treated thermite weld in rails

This paper describes a comparative study of the hardness characteristics, m echanical properties, microstructures, and fracture mechanisms of the therm ite welded rail steel joints before and after heat treatment. It has been f ound that heat treatment of the welded joint improves the mechanical proper ties (UTS and elongation), and changes the fracture mechanism from brittle to ductile. Improved strength and elongation are attributed to the finer fe rrite-pearlite microstructure and the different fracture mechanism. Micropo rosity and numerous inclusions were seen on the fracture surface of the wel ded joint. The chemical composition of the inclusions indicated that the mo lten thermite mixture had reacted with the magnesite lining of the ladle an d the feeder. (C) Elsevier Science Inc., 1999. All rights reserved.