The Simulation Of Microstructure And Rail Bending Deformation In Quenching With Residual Heat

With the continuous development of China’s railway industry,the annual cargo volume of railway transportation has been increasing year by year,the rail wear is increasing,and the service life of the rail is shortened.Therefore,higher requirements are placed on the wear resistance of the rail.Heat treatment technology is one of the means to improve the wear resistance of the rails,the small radius curve segment uses heat treated steel rails with several times the wear resistance of conventional hot rolled steel rails.times the wear resistance of conventional hot rolled steel rails.The use of heat-treated rails can effectively reduce rail damage such as rail side grinding,peeling off,crushing and wave grinding.The combination of heat treatment technology and micro-alloying design of rail components is the key to meeting the technical bottleneck of current rail development.The addition of alloying elements puts forward higher requirements for the commissioning and optimization of the rail heat treatment process.It is necessary to analyze the parameter control of the rail heat treatment process more systematically and provide theoretical guidance for the process parameters of the heat treatment rail.In this paper,the quenching process of 380 HB grade rare earth heat treated steel rail is taken as the research object,and the optimized composition of the industrial trial steel rail is optimized to determine the optimal chemical composition range of the rail to meet the mechanical properties.The heat treatment process of 380 HB rail was analyzed.It is proposed that the influence of the pearlite rail spacing is not only related to the cooling rate,but also related to the material transformation start temperature of the material.The rail heat treatment process is a "continuous isothermal transformation process" between the isothermal transition and the continuous cooling transition.The calculation shows that the temperature drop of the380 HB heat treatment rail is controlled at 200~250 °C.The phase transition of the steel head tread is between 18 s and 22 s,the phase change of the tensile strength of the rail head is between22 and 30 s.In this interval,the cooling strength is increased,the degree of subcooling is increased,the pitch of the pearlite structure layer is refined,and the phase transition temperature of the pearlite structure is lowered.The starting temperature of the control rail head tread phasetransformation should not exceed 620 ° C,the phase change starting temperature of the rail head tensile strength sampling should not exceed 650 ° C,and the rail enters the quenching line and the quenching temperature is controlled within the range of 760 ° C ± 20 ° C.Through the research in this paper,the on-site rail heat treatment process was guided,and the chemical composition of the grade steel grade was optimized,which saved the cost for the enterprise.The paper,the static analysis of temperature,microstructure,stress and strain during quenching process is provided,which provides a theoretical calculation range for temperature control and phase transition time of heat treatment process.In order to solve the problem that the mechanical properties of this grade heat-treated rail does not meet the requirements in the industrial trial production,the theoretical explanation is given.According to the research results of this paper,it provides a reference for the subsequent optimization of the heat treatment debugging process of this grade.