| 6XXX aluminum alloy is mainly used in the field of rail transit.With the rapid development of the rail transit industry,lightweight and high speed have become the development direction of modern vehicle transportation,so the research and application of advanced aluminum profiles are very important.Conventional quenching usually adopts vertical pit quenching,which has low quenching efficiency,poor uniformity of structure,large quenching deformation,and cannot produce advanced aluminum profiles such as aviation.high-speed rail and automobile in large quantities.New roller-type continuous heat treatment designed and developed by Northeastern University.It integrates solid solution and quenching.It has various quenching methods of gas quenching,mist quenching and water quenching.It can carry out batch production,greatly improve production efficiency,good organization uniformity and less quenching deformation.This paper takes 6005A aluminum profile as the research object.In this paper,6005A aluminum profile is taken as the research object.Firstly,the isothermal quenching experiment is designed.The TTP curve of 6005A aluminum alloy is drawn.The TTT and CCT curves of 6005A aluminum alloy are simulated by JmatPro software to determine the critical quenching cooling rate of 6005A.Secondly,the influence of isothermal temperature and holding time on the microstructure of 6005A aluminum alloy was studied by TEM.The paper uses FLUENT finite element software to simulate the three-dimensional flow-heat coupling of the quenching process.For symmetrical profiles and asymmetric profiles,the paper analyzes the effects of static quenching,dynamic quenching,wind speed and swing speed in the quenching zone on the temperature uniformity and quenching cooling rate of the two profiles.The main results include:(1)The tip temperature of 6005A aluminum alloy is about 360℃,the quenching sensitive temperature range is 250℃～450℃;the critical quenching cooling rate is 2.5℃/s.When the alloy is kept at 350℃,the supersaturated solid solution decomposition rate is faster,the amount of β" phase precipitated in the crystal increases,the size becomes larger,and finally the β stable phase is formed;in order to ensure good comprehensive mechanical properties and reduce quenching deformation,the cooling rate of the quenching sensitive zone should be increased,and The cooling rate in the high temperature zone and the low temperature zone is appropriately lowered.(2)For thin-walled symmetrical profiles,the longitudinal and high-temperature zones alternately appear in the longitudinal quenching process,and the temperature fluctuates greatly.With the increase of wind speed,the maximum temperature difference between the longitudinal and lateral directions of the profile increases gradually,but the longitudinal temperature distribution is more uneven.During the dynamic quenching process,the longitudinal temperature distribution inhomogeneity is solved.When the wind speed is greater than 40 m/s,the temperature difference of the cross-section temperature tends to be stable;the swing speed of the quenching zone mainly affects the uniformity of the longitudinal temperature,and when the swing speed of the quenching zone is greater than 50 mm/s,the longitudinal temperature fluctuation range is kept within ±3℃,the longitudinal temperature distribution is no longer affected by the swinging speed of the quenching zone.(3)For asymmetric and thick-walled profiles,the flow of air is affected by the cross-sectional shape of the profile,the flow velocity of the air at different locations is different,resulting in different heat transfer strengths at each location,which is the main cause of uneven temperature distribution;when the wind speed is greater than 40 m/s The wind speed has no obvious influence on the distribution of the cross-section temperature;when the swing speed of the quenching zone is greater than 50 mm/s,the longitudinal temperature fluctuation range is kept within ±2.5℃. |
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