Abstract:The relationship among rollong contact fatigue crack at the gauge corner, wear and hardness of the U75V heat treated rails in field curve was analyzed by surface observation, sampling, wear measurement, laboratory photomicrograp for length and depth of the crack and hardness of the rail longitudinal cross section measurement at different traffic. The research show that there were 3 main periods during the fatigue crack growth: crack initiation and rapid propagation, co existence of crack and wear, and growth and wear control crack. The crack at the gauge corner propagated into the railhead with the angle of 10.8° to 29.4° with respect to the rail longitudinal surface. When the hardness of the heat treated layer was 340 to 360 HB and above, the wear growth rate was less than 0.015 mm·Mt-1 with rapid fatigue crack growh. The rail pre grinding from new rail installation to 5 to 10 Mt and preventive grinding with an interval of 30 to 60 Mt were recommended to balance the crack and wear. The thickness of the heat treated layer with 340 to 360 HB and above should be over 10 mm.
