Correlation between Microstructure and Hardness of a Flash Butt-Welded Rail Joint

In this paper, the results analysis of microstructure and hardness examination of pearlite rail steel type 260 and its welded joint are presented.The relationship between the microstructure and the local hardness in different zones of the Flash Butt Welding (FBW) weld was examined, and the correlation was interpreted in terms of the quality of the examined microstructure.The main microstructural variations in the FBW weld occur within the Heat Affected Zone (HAZ).The local decrease in hardness in the zone of intercritical HAZ is caused by spheroidization of cementite.For this reason, the measured hardness values changed when advancing from the centreline of the weld towards the base metal.When moving slightly from the centreline of the weld to the maximum value across the weld in the area 1-2 mm away from the centre of the weld, the hardness value increased sharply.At the visible extent of HAZ, where the pearlite is partially spheroidized, the hardness decreased to a minimum value.Moving away from the visible part of the ZUT, the hardness gradually increased, returning to the value of the hardness of the base metal.The purpose of this paper is to present the relationship between microstructure and hardness on the longitudinal section of a flash butt-welded rail joint and to indicate their inter relationship.It has been confirmed that the altered microstructure in the welded joint of the rail leads to a change in hardness in areas of reduced hardness.