Browsing by Author "Ramadan, Nizar"
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Item PROCESS DESIGN OPTIMIZATION FOR THE POST-WELD CONTROLLED ACCELERATED COOLING OF R350HT HEAD HARDENED RAIL JOINTS(2022-02-21) Ramadan, Nizar; TUR, Kazım; KONCA, ErkanIn order to benefit fully from the use of head hardened rails, the weld and the heat affected zones of these rails must have microstructures with mechanical properties similar to those produced by the fine pearlitic microstructures of the rails themselves. For the flash butt welding of head hardened rails, this is only possible through the accelerated controlled cooling of the related zones just after the welding operation. In this study, the required method and the conditions for the controlled accelerated cooling of flash butt welded head hardened R350HT rails have been investigated. Dilatometer experiments were performed on R350HT rail steel samples in order to determine the heat treatment conditions to produce microstructures that would give the hardness values required by the related rail and rail welding standards. A computer simulation study was undertaken to improve the design of the apparatus to be used for the accelerated cooling of the rail welds. A custom accelerated cooling system that employs this specially designed apparatus was used on flash butt welded R350HT rail joints of the 60E1 profile and results satisfying the related EN 14587-2 standard were obtained. For the aluminothermite welding of the head hardened rails, it was shown that the related EN 14730 standard could be met through the use of the proper weld portion.