Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Abstract The joining process of bainitic rails is significant in terms their industrialization high-speed and heavy-loaded railways. This paper demonstrates the microstructure changes critical zone welded joint, which responsible for greatest deterioration mechanical properties. Extensive progress decomposition retained austenite ferrite occurs low-temperature heat-affected (LTHAZ) flash-butt joint low-carbon rail. products were mainly a mixture cementite ferrite. was precipitated at boundary laths, indicates lower thermal stability filmy austenite. Moreover, it found that part refined blocky decomposed into nanometric cementite, while another remained structure. mechanisms are rather heterogeneous with varying degrees decomposition. A relatively high proportion dislocations stress fields prove occurrence residual stresses formed during welding process.