Microstructure and Mechanical Properties of Rail Steel Welded by Flash Butt Welding

Abstract

TR-57 intermediate steel rails were welded in a Brazilian flash butt welding plant and the joints were subjected to a detailed mechanical and structural characterization. Quantitative data were subjected to ANOVA analysis. The metallography has confirmed the majority presence of pearlite, but pro-eutectoid ferrite was also verified in the weld centerline. Globulized cementite appeared in some regions of the Heat Affected Zone (HAZ), particularly in the partial transformation zone. The pearlite colony size and pearlite interlamellar spacing were related to Vickers microhardness over the full joint length. The base metal met the minimum specified tensile properties in the AREMA standard. However, the weld joints did not meet the minimum tensile strength and all samples fractured in the partial transformation zone, which has lower hardness. The results help to deep understand the structure-properties relationships over the full joint, highlighting the relations between the welding process and the resultant pearlite morphology. Considerations about the component failure modes previously related in scientific literature are also presented.

Key-words:
Flash butt welding; Rail steels; Mechanical properties of welded joints; Welding metallurgy