With analyzing the thermal boundan conditions in cooling process of U75 V steel rail

the temperature field of 100 in steel rail during cooling process at 845 ~ 150 ℃ before straightening has been calculated by using three-dimensional non-linear finite element method. Results showed that during cooling process the temperature decrease rate was different at different position of cross- section of rail

in initial cooling period (200 ~2 000 s) a "platform'' period with temperature decreasing slow for each curve occurred

for instance the cooling rate was fastest at edge of rail bottom at which the phase transition was earliest: in cooling for 2 500 ~ 3 000 s

the temperature at rail head

rail waist and median of rail bottom decreased very quickly and the temperature difference between rail head and edge of rail bottom was about 5℃

in cooling for 5 000 ~ 7 000 s the temperature of each position tended to show no difference; the difference between calculated temperature and measured temperature at situ was less than 50℃.