Finite Element Simulation Of Temperature Field And Microstructure And Property Analysis Of H-beam Under Ultra Fast Cooling Conditions

H-beams are widely used because of their high strength,light weight and flexible design.However,due to its complicated cross-sectional shape,on-line controlled cooling is prone to uneven cooling,which causes warping and bending of H-shaped steel,and may also affect the distribution of the structure and mechanical properties.Combined with the "13th Five-Year Plan" national key R&D plan "Key technologies for intelligent preparation of long sections",the sub-project "intelligent production and application of complex cross-section profiles",taking H-shaped steel with material Q235 and model H200×200mm as the research object,a three-dimensional finite element model of the H-beam cooling process was established in ANSYS software.The transient temperature field,stress field,and corresponding time history curves of the H-beam controlled cooling process were obtained by finite element simulation.The simulation calculation results were compared and analyzed with field experimental results.Based on experiments and simulation calculations,an optimized cooling scheme was determined to improve the microstructures and properties and provided reliable experimental data for industrial production.The main research contents and results were as follows:(1)The continuous cooling transformation curve of experimental steel was drawn through experiments,which provided data basis for determining the finite element model and key parameters of the cooling experiment.When the cooling rate was 0.2?0.5?/s,only ferrite and pearlite were present in the experimental steel.When the cooling rate reached 5?/s,the structure was ferrite,bainite and a small amount of pearlite.When it reached 10?/s,ferrite,martensite,and bainite were generated in the structure.(2)The initial cooling scheme was designed and the finite element modeling was carried out by ANSYS software,and the same parameters of experiments were adopted.The temperature changes and of different parts of H-beam section and node displacement were calculated by using the proposed model,and the results were compared with the measured values in the field.The results show that the deviation between the calculated value and the measured value was very small,which showed that the calculated results of the finite element model were reliable.(3)The field experiments and finite element simulations were carried out by adopting five different schemes to change the nozzle position.The temperature field of the H-beam was simulated and analyzed by ANSYS software.The results showed that the temperature at the center of the R corner was the highest,and the temperature at the center of the web decreased most rapidly.Where the temperature distribution was quite different,the greater the stress was,and the law of stress and strain distribution was basically consistent.(4)The typical parts of H-beam were sampled and metallographically observed.The tensile strength,yield strength,and elongation were measured by experiments.And the effect of uneven cooling on the microstructure and properties of the experimental steel was studied.The results showed that when the optimized cooling scheme was adopted,the temperature distribution was uniform,and uniform microstructure and properties could be obtained by uniform temperature distribution.