Numerical Simulation Of Temperature And Stress Field During U71Mn Steel Rail-head Quenching Process

Our country is mainly relied on railway transportation . With the development of national economy, the traffic volume of the railway was increased day by day.The intensity and wearability of the railway was required to improve the driving speed of train. And higher demand had been proposed to improve the service life of heavy rail. But such questions as the hardness, fragility, toughness and cleanliness of the heavy rail were very visible. The heavy rail wasn't in the situation of uniform cooling; the phase transition and the internal stress were influenced and changed directly by the changing temperature field.The specification of 50kg/m-heavy rail was taken as investigated subject in this paper. The quenching process of rail-head was simulated to study the stress filed by finite method. In this model, the equivalent thermal capacity method was used to deal with the influence of latent heat on temperature filed and the transformation stress which resulted from phase transformation was taken into account using the equivalent linear expansion coefficient method. The impact of material's non-linear parameter on temperature field was considered. The results show that the simulation result is identical with the measuring temperature. The model can achieve dynamics and exact calculation of temperature field of heavy rail, forecasted transient temperature during quenching. According to the distribution of temperature field, the time of compressed air should be controlled. The ideal sorbite can be gained.During the process of calculating in numerical simulation, inputed the convective heat transfer coefficient under different wind pressure received the corresponding result of temperature field and stress filed, and analyzed the result. This paper analyzed that calculated heating, keeping warm, force cooling and air cooling's temperature field and stress filed distribution in such different operating modes. The impact of quenching time on temperature field and stress filed. And the result of calculation approached the three-dimensional work piece. Then calculational result and experimental result were compared. The tested result is in agreement with the measured temperature quite well. Gas quenching can induce lower residual stresses and protect the heavy rail from distortion and cracking. The numerical simulation verified the exactness of this finite element model, thus it is significantly valuable for the heavy rail quenching and can be used to guide the quenching process design.