Numerical Simulation Of Normalizing Cooling Process Of U75V Based On Fluent

The 13 th five year plan will basically build a safer and more efficient modern railway transportation system in 2020,which puts forward higher requirements for CWR.Flash welding is used in most of the welding process of CWR in China,and the welded joint is the main weak link of CWR,so the mechanical properties of welded joint must be improved by post weld heat treatment.The simulation of the cooling process by computer simulation can simulate the flow field and temperature field of the cooling process more accurately,and further understand how to improve the structure and mechanical properties of the heat treatment process and improve the welding quality of the rail.The main content of this paper is to develop a reasonable flash welding process and post weld heat treatment process analysis,and then through the computer ansys-fluent to simulate the process of normalizing air cooling and normalizing jet cooling in post weld heat treatment,through the comparison between the simulation results and the actual measurement to determine the reliability of the simulation,The simulation was used to explain the microstructure and some important mechanical properties after normalizing.The conclusions are as follows(1)The cooling flow field of normalizing jet moves up and down along the rail surface,and the velocity of the flow field increases gradually from top to bottom.The velocity at the junction of rail waist and rail head and at the side of rail bottom increases obviously;The cooling rate of normalizing air cooling and normalizing air cooling is:rail bottom > rail waist > rail head.(2)Through the data of monitoring points measured by infrared thermometer,the temperature data obtained by numerical simulation is compared with the actual measured data by interception method,and it is verified that ANSYS fluent numerical simulation of normalizing cooling can simulate the temperature field change of normalizing cooling stage more accurately.(3)After normalizing and air cooling,the rail head is finer than that of the rail bottom,the network ferrite disappears,but the massive proeutectoid ferrite precipitates,and the pearlite is uniform.Rail head is smaller than that of rail bottom,;The amount of proeutectoid ferrite decreases obviously;Combined with the numerical simulation of normalizing cooling process,the change of microstructure was explained.(4)After normalizing,the toughness of the joint is greatly improved,and different cooling methods have different effects on the toughness of different parts;Comparing the fracture morphology and temperature field of normalizing air cooling and normalizing air cooling,the simulation results show that with the increase of cooling rate,the thickness of the fiber area and shear lip of the fracture becomes thicker,the proportion in the range of the picture increases,the river pattern is clearer,the transverse shrinkage of the notch root is larger,and the macroscopic performance is better impact toughness;After flash welding,there is softening band,and the hardness matching is not good;After normalizing,the softening zone increases,but the hardness distribution can not be improved;After normalizing and air cooling,a softening band appeared,and the hardness matching was better,and the hardness distribution was uniform.