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Test and simulation study of the 7050 aluminum alloy spray quenching

Author: GuoShiGui
Tutor: DengYunLai
School: Central South University
Course: Materials Processing Engineering
Keywords: 7050 aluminum alloy plate Spray quenching Hardnability Heat transfer coefficient Temperature field
CLC: TG156.3
Type: Master's thesis
Year: 2010
Downloads: 18
Quote: 0
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Abstract


Harmonizing the hardnability of 7050 aluminum alloy plate and residual stress in the water spray quenching is the key technology to manufacter the large size of aluminum sheet.End-quench test of 7050 aluminum alloy by spraying water with independent parameters of pressure (p) and average volumetric flux over spraying area (qs) has been designed.Effect of parameters of p, qs and nozzle diameter (d) on heat transfer coefficient has been studied;The experiment of double quenching has been learned,also its cooling mechanism;The temperature field and heat transfer coeficient have been simulated and modified by finite element soft ABAQUS,and the residual stress of the test specimen quenched in the designed queching processes is also simulated and learned;As a result,the conclusions can be gotten:(1)The results show that the maximum value of heat transfer coefficient (hmax) always occurs when the spraying surface temperature is 100-150℃,and the scale of hmax is 20000-50000W·m-2·℃-1.The 3-D diagram of hmax-qs-p is established,which can reflect the effect of parameters of p and qs on heat transfer.The 3-D diagram of hmax-k-qs,in which k represents ratio of spraying surface area to cross-section of nozzle,is also established to show effect of d on heat transfer.The diagrams of hmax-p-qs and hmax-k-qs are helpful to select quenching parameters (p, qs, k, et al) by spraying water.(2)A mathematical mode of inverse problem of heat conduct equation is analyzed and established.It is found that the surface heat transfer coefficient is spatial normal distribution round end-face in water spraying.The temperature field is simulated when loading different surface heat transfer coefficient by using ABAQUS finite element software.The results show that,when considering the heat transfer coefficient circle end-face in water spraying with spatial normal distribution and the air heat transfer coefficient dynamic changing,the calculated temperature field matches with the measured data so well. (3) The cooling effect of double quenching process which firstly using high pressure then low pressure is superior to the single queching processes and another double process.The main mechanism is that double queching process improved the distribution of coefficient of heat transfer on the spraying face.So the test specimen has more time to transfer heat with high coefficient of heat transfer,as a result,the hardening depth of test specimen get improved.So designing reasonable quenching process is a key way to improve hardening depth,then improve hardability.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Heat treatment > Heat treatment process > Hardening, surface hardening
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