| High-strength steel has a wide range of applications in the fields of automobiles,at the same time,the ultimate low temperature tempering technology is one of the key technologies for improving the performance stability of high strength steel plates.After the heat treatment,the shape and performance of the steel plate are directly related to the control accuracy of the furnace temperature.Generally,the deviation of the temperature control accuracy is generally less than 15 ?.High-end high-strength steel products generally require a tempering heat treatment process with a furnace temperature lower than 300?,and are highly sensitive to temperature.Therefore,the temperature uniformity and temperature control accuracy of the tempering furnace are required to be high at low temperature tempering.When the furnace temperature is less than 300?,the temperature uniformity and temperature control accuracy deviation of domestic common tempering furnaces are all above 20?30?,which is difficult to meet the production requirements of high-end high-strength steel products.In response to the above problems,the State Key Laboratory of Rolling Technology and Continuous Rolling Automation of Northeastern University has developed a new mediumlow temperature tempering furnace using hot air circulation.The finite element numerical simulation technology is used to establish a simulation platform for the hot air impact steel plate heating process in the hot air circulation furnace.The influence of the structural parameters of the hot air circulation furnace spray box on the flow field in the furnace is studied.And the influence of flow parameters and nozzle parameters on the heat transfer characteristics of hot-blast impacted steel sheets is analyzed,and the way of using the oscillating heating of the steel plate can achieve the temperature control accuracy deviation requirement for the tempering furnace for producing high-end high-strength steel,which provided theoretical guidance for the design and manufacture of hot-air circulation furnaces.The main research work and results are as follows:(1)The experimental study on the heating of high-strength steel plates with different heating methods shows that the heat transfer strength and heat transfer efficiency of hot-soilimpacted steel plates are much higher than those of radiant heating steel plates;The heat transfer characteristics of the circulating hot air impingement heating steel plate are studied,and the influence of jet flow velocity on the heat exchange efficiency of hot air impact heating steel plate is investigated.(2)The working principle of the hot air circulating tempering furnace and the heat transfer phenomenon of the steel sheet during the heat treatment process are systematically analyzed.The FLUENT universal CFD simulation software is used to simulate the forced circulation system,and the mathematical model of the hot air circulation type tempering furnace is established.The model is verified by grid independence and the turbulence model is selected.(3)Based on the simulation platform of the hot air impact steel plate heating process,the influence of the structural parameters of the hot air circulation furnace spray box on the flow field in the furnace is studied.By analyzing the appropriate parameters of the length of the spray box and the diameter of the round hole on the sloping plate of the air duct,the pressure distribution uniformity at the nozzle inlet is obtained.Based on the abo ve-mentioned furnace structure parameters,a new mathematical model of the tempering furnace is established,and the simulation is carried out.The simulation results are compared with the experimental measurements,and the correctness of the mathematical model used in the simulation is verified.(4)Based on the simulation platform of hot air impact steel plate heating process,the effects of jet nozzle parameters and motion parameters on the heat transfer characteristics of hot air impact heating steel plates are studied.The effects of nozzle parameters and motion parameters on the heat transfer performance of the steel plate are obtained,and in the simulation of this paper,the most suitable nozzle parameters are selected;By comparing the simulation results of the impact heating of the steel plate under different motion states,it is concluded that the swing heating of the steel plate can achieve the design requirement of temperature uniformity when the steel plate is subjected to low temperature tempering heat treatment. |
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