Reason Analysis on Substandard Elongation after Fracture of U75V Rail Web of Flash Welding Joint

Using chemical composition analysis, mechanical properties testing, metallographic examination and fracture analysis to find out the reason of substandard elongation after fracture of U75V rail web of flash welding joint. The results showed that there were numerous dense inclusions (MnS ratings reached 3.0 grade) in rail joint and rail web, the long stripe of MnS inclusion after welding upsetting, was deflected with the metal flow, and the deflecting direction was 45°, when it was parallel to the tensile process of 45° maximum shear stress, that means was the MnS inclusion subjected to transverse tensile shear, the cracks was so easy dehisced and expanded in MnS inclusion, elongation properties was so low.