At present, all premium rail is manufactured by an accelerated cooling process that produces a fine pearlitic microstructure in the rail head. These accelerated cooling processes include forced air cooling, water spray cooling and quenching in oil or an aqueous polymer solution. Although all of these various processes are designed to produce a similar microstructure, there can be significant differences JL the characteristics of the microstructure and hardness distribution throughout the rail head. One major difference can be seen by comparing off-line and in-line head hardening systems. In an off-line* head hardening system, the rah1 head is reheated into the austenite regime and subsequentlyforced air cooled. Because the rail head is reaustenitized by induction heating, the off-line processes produce a marked microstructural change between the austenitized and unaustenized portions of the head.
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