Fluid-temperature-phase-stress Multi-field Coupled Numerical Simulation Of Heat Treatment Process

Numerical simulation of heat treatment can be used as an aid to the heat treatment process of product.It can save a lot of test cost and improve the efficiency of heat treatment process development.It has now been widely used.However,as one of the simulation input parameters,the influencing factors of the boundary heat transfer coefficient is complicated.This leads to that the previous measurement results usually could not be reused for different environments,affecting the application of heat treatment simulation.Recently,the simulation of the flow of heat treatment medium has been added,expanding the solution domain of heat treatment simulation.It replaces the role of the heat transfer coefficient for the simulation,which has been one of the research directions of heat treatment simulation.The discretization principle and numerical analysis method of the fluid domain and the solid domain during heat treatment are compared.Finite volume method has the advantage of small computation compared with finite element method.So it is more suitable for the simulation of the internal flow field of large heat treatment equipment.Aiming at the coupled interaction of fluid-structure in the heat treatment process,the interpolation function of MPCCI software is put forward.Using finite element-finite volume coupled simulation method,for the first time the coupled numerical model simulating on the distribution of flow,temperature,phases and stressstrain during a heat treatment process is established.A multi-field coupled numerical model for high pressure gas quenching process is established.The cooling process of cylindrical bulk material in SGF-644 H vacuum high pressure gas quenching furnace is simulated and validation experiment is made.The simulation results show that the cooling of cylindrical bulk material in the gas quenching furnace is not uniform and there is temperature difference of the workpiece at different positions at the same time.The main reason is that the gas flow is blocked by the load tray,resulting in lower cooling rate.After quenching the workpiece is mainly composed of ferrite and bainite.As the workpiece size is small and the cooling rate is low,small amounts of martensite is generated.The average residual stress is about 10 MPa.The experimental results of temperature sampling data and metallographic tests show that the simulated results well explain the experimental cooling curves and microstructure characters at typical locations.The multi-field coupled numerical simulation of 30Cr2Ni4 MoV lowpressure rotor forced convection heating in a large-scale pit type resistance furnace is made.The internal flow field of the furnace,temperature field,microstructure field and stress field of the furnace are obtained.The simulation results show that the gas velocity distribution in the furnace is not uniform.The flow rate near the upper end of the rotor is highest,resulting in higher temperature of the upper end.The temperature difference between the upper and lower shaft head is about 37 ?.In the step heating process,the maximum thermal stress appears at the end of the first temperature rise near the center of the cross-section.The effects of different inlet flow velocities on the temperature,microstructure and thermal stress of the rotor are investigated.The result shows that the decrease of inlet flow velocity has different effect on the gas flow velocity at different positions on the rotor surface,and the decreasing range of velocity decreases from top to bottom.With the decrease of inlet flow velocity,the maximum thermal stress of the rotor increases during the heating process.In addition,as the inlet flow rate decreases,the austenitizing start time of the rotor gradually progresses backwards,and the time interval of the austenitizing start time between the surface and center increases.