Parameter Analysis and Establishment of Empirical Equations During Hot Rolling Processes of Aluminum Alloy 5182

• Main Authors: Kuo-hsing Wang, 王國興
• Other Authors: Yeong-maw Hwang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/t48fzx

博士 === 國立中山大學 === 機械與機電工程學系研究所 === 102 === Aluminum alloy 5182 (AA5182) has been widely used in beverage cans, automobile parts, computer, communication and consumer electronics (3C) products for excellent properties, such as high strength-to-weight ratio, electro-magnetic shielding, better corrosion resistance, and recyclable etc. The strain and temperature of the hot rolled strip affect the microstructure of material as well as change the strength and formability of the product. In order to improve the product performance, it is essential to understand the effect of process parameters during hot rolling on the strain and temperature of the strip. Several studies have been published to investigate the effects of strain and temperature on the recrystallization behavior of AA5182 strip during hot rolling. However, only a few studies published discussed the effects of process parameters on the strain and temperature distributions of AA5182 strip during hot rolling. In this study, the finite element simulations of the strain and temperature distributions of AA5182 during hot rolling were carried out by using a commercial code DEFORM. Firstly, the cylindrical compression tests were performed to obtain the mean flow stress curves of AA5182 at strain rates of 0.01 s-1 to 30.0 s-1 under 320oC to 470oC by using Gleeble thermal-mechanical simulator for understanding the strength of material at elevated temperatures. The mean flow stress curves were applied to simulate the hot rolling of AA5182 strip. The relationships between the mean flow stress obtained by the cylindrical compression test and material flow stress were established by using the finite element simulations. It is known that the error between the mean flow stress and material flow stress is about 2% to 4% during the cylindrical compression test considering the effect of friction at the interface between the cylindrical and anvils. A hyperbolic-sine Arrhenius equation was used to characterize the flow stress curves of aluminum alloy 5182. The parameters of characterization equation were obtained by using experimental data and the least square method. The error between the prediction results obtained by the characterization equation and the experimental data is within 10%. Secondly, the finite element simulations of hot rolling were carried out to investigate the effects of process parameters and boundary conditions involved reduction in thickness, entry thickness, rolling speed, coefficient of coulomb friction and interfacial heat transfer coefficient on temperature variation of the strip and distributions of strain and temperature in the thickness direction at the roll bite exit. The results of simulations were applied to the prediction model of static recrystallization behavior proposed by literature and discussed the effect of process parameters and boundary conditions mentioned above on static recrystallization behavior. The mechanisms about effects of process parameters and boundary conditions on strain, temperature, and static recrystallization behavior of the strip were proposed. Finally, the empirical equations were established for predicting rolling force, forward slip ratio, surface temperature and average temperature of strip at the roll bite exit and balance temperature of the strip by regression analysis and simulation results. A prediction model for the rolling results of hot continuous rolling of AA 5182 was also proposed. The parameters applicable of the prediction model proposed are as follow: the work roll diameter is 700 to 1000 mm, the entry thickness 5 to 50 mm, the reduction in thickness 30% to 60%, the coefficient of coulomb friction 0.15 to 0.40, the ratio between tension and mean deformation resistance 0 to 0.4, the speed of work roll 0.1 to 6.0 m/s, the entry temperature 320oC to 450oC, the interfacial heat transfer coefficient 10 to 400 kW/m2∙oC. The results of this study and the empirical equations proposed can provide useful knowledge for rolling pass schedule design during hot rolling process of AA 5182. In addition, flow stress characterization equation proposed can improve the accuracy of simulation results of hot forming processes in industrial and academic fields.