Study On The Interface Heat Exchange Of Complex Cross Section Aluminum Alloy Profiles During Online Quenching Process

Due to the characteristics of complexity in shape and difference in wall thickness,aluminum profiles of large and complex cross section often encounters warping,distortion during quenching process. As the computer develops rapidly, numericalsimulation technique is gradually applied to research the quenching process. Heattransfer coefficient is one of the most crucial parameters of the boundary conditionduring simulation，However it is difficult to obtain it accurately. Thus, the inversemethod is applied to exactly calculate the heat transfer coefficient.In present paper, an end quenching experiment was designed. Cooling curves of6061,6082aluminum alloy during quenching were measured. The effect of water flow,wind speed, surface roughness of profile and materials on cooling curves wereanalyzed. Coupling the cooling curves with the inverse method, the heat transfercoefficient of aluminum alloy in different quenching process was obtained.It was shown that during water quenching, the heat transfer coefficient increasedfirstly and then decreased with decreasing surface temperature，with increasing waterflow or profile’s surface roughness, the heat transfer coefficient increased, and thetemperature corresponding to the peak heat transfer coefficient was decreased. Theeffect of water flow was remarkable, while the impact of roughness was undetectable.For wind cooliing, the heat transfer coefficient firstly increased sharply and thenattained a steady state with decreasing surface temperature. With increasing windspeed or profile’s surface roughness, the heat transfer coefficient increased. The effectof wind speed was significantly, nevertheless, there was negligible influence ofroughness. The heat transfer coefficient of6082was a little larger than this of6061under the same quenching condition.Based on the obtained heat transfer coefficient, a finite element analysis modelwas built to predict the air quenching process of a commercial6082aluminum profile，and its accuracy was verified. The distributions of temperature, stress and strain fieldof profile under different situations were analyzed. The profile was cooled to roomtemperature around100s at a wind speed of30m/s. As quenching process continuing,the difference of temperature for the different part decreased from a maximum of30℃to0℃. In quenching process, obvious stress first increased from0to a peak value of130MPa in15s and then decreased slowly. There was small strain in profile afterquenching. During quenching, cooling rate of the profile was faster and the stress and stain of it were larger with higher wind speed. The simulated results showed that if thewind speed was kept around20m/s，not only the cooling rate of aluminum alloy wassatisfied, but also deformation of profile could be controlled.