| In the 21 st century,among the three modes of transportation,aviation,highway and railway,if you choose the most popular mode of transportation;railway will definitely become the first choice.The rail is the core component of the railway,and its quality directly affects the safety of driving.In recent years,the form of damage suffered by the rail has changed from the fatigue damage of the rail induced by the rolling contact between the traditional wheels and rails to the additional corrosion fatigue damage caused by different media conditions and wheel-rail rolling contact.Therefore,it is of great significance for the development of China’s railway to study the initiation and fracture behavior of rail corrosion fatigue cracks.This article takes U75 V rail as the research object,and chooses to study its corrosion fatigue under simulated extreme conditions.The corrosion morphology of U75 V rail and the initiation of corrosion fatigue cracks were studied through equipment such as "EA-08" periodic infiltration corrosion box,high frequency dynamic fatigue machine,GALYA3 field emission scanning electron microscope,S-3400 environmental scanning electron microscope,OLS4000 laser confocal microscope,The relationship between fractures.First,the pearlite lamellar spacing was refined by heat treatment at different cooling rates,and the pearlitic lamellar spacing at a cooling rate of 3 ℃ /s and 5 ℃ /s was respectively:0.2012 um and 0.1224 um.It is 0.3045 um.The heat treatment refinement effect with the cooling rate of 5℃/s is the best.By studying the corrosion morphology,the corrosion type is non-uniform corrosion.With the increase of corrosion time,the maximum diameter of corrosion pits,roughness and depth of corrosion pits increase with the increase of corrosion time in 5 ℃ /s By studying the corrosion morphology,the corrosion type is non-uniform corrosion.With the increase of corrosion time,the maximum diameter of corrosion pits,roughness and depth of corrosion pits increase with the increase of corrosion time in 5℃/s heat treatment androlling conditions.The rolling corrosion time is: 240 h,360,480 h,the maximum diameter of the corrosion pit is increased from 388.890 um to 516.274um;the depth is increased from 0.091 mm to 0.297mm;the roughness is increased from 12.18 um to 12.61 um.5℃/s heat treatment state corrosion 240 h,360h,480 h,the maximum diameter of the corrosion pit increased from 351.025 um to 501.916 um,the depth increased from 0.077 mm to0.259 mm,and the roughness increased from 9.29 um to 10.59 um.It is concluded that the smaller the spacing of the pearlite sheets under the same material,the smaller the corrosion pits.With the increase of corrosion time,the corrosion pits formed may be a single corrosion pit or a combination of multiple corrosion pits.The shape of the corrosion pits formed by pearlite is U-shaped.After corrosion,the life of the fatigue specimen is greatly reduced.The corrosion time is 240 h,which is 10 times lower than the life without corrosion.The fracture of corrosion fatigue still has a crack source,crack extension area,and transient fracture area.The pit is the source of cracks for expansion.The non-corroded fatigue specimen has only one crack source.After 240 h and 480 h,the corrosion fatigue specimen has multiple crack sources.The crack propagation area is very small and is not easy to be found.1.017 um increased to1.799 um.Through the above experimental research,it will have a certain guiding role in improving the corrosion resistance fatigue life of the rail. |
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