| The large-scale use of aluminum alloy panels is a very important approach to realize automobile lightweight,and the appilication of aluminum alloy panel was depend on the stamping technology of the sheet.Aiming to the problem and demand of surface treatment and lubricating material for automotive aluminum alloy sheet in China,cupping and tribological tests were used,associating with surface analysis methods like white light confocal microscopy and scanning electron microscopy.Besides,the computer simulation technique was employed.The effect of lubricating material on the stamping performance of automotive aluminum alloy sheet was systematically studied.The lubrication performance and surface quality of aluminum alloy stamping were investigated with the lubricating medium like the ester base oil,its extreme pressure additive and PTFE-containing solid lubricant film.The lubrication models of the lubricating medium types(liquid/ solid lubrication)in the stamping process were established to reveal the lubrication mechanism.The effect of anodic oxidation film on the stamping of aluminum alloy sheet were studied under the condition of oil liquid lubrication and PTFE-containing solid lubricantion.A further analysis has been given to the formability and surface quality of aluminum alloy sheet.The simulation model of aluminum alloy sheet cupping was established by computer simulation technology to research the influence of friction coefficient between aluminum alloy sheet and molds on the formability.The main results of this paper are as follows:(1)Under the lubrication condition of TMPTO and DOA ester base oils,the forming performance and forming quality of aluminum alloy sheet are affected by changing the lubrication state of the contact surface between the 6061-T6 aluminum alloy sheet and molds.The extreme pressure additives like T321 and Cu-DDP can enhance the extreme pressure performance of both base oils,reduce the punching pressure and improve the surface quality of the formed parts.(2)Solid lubricating layer containing PTFE exhibits the better lubricating property in stamping,and the formed parts have higher surface quality.The established lubrication models reveal the lubrication mechanisms that(i)the mixture lubrication state can be confirmed between the contact surfaces of the sheet and the mold under the oil lubrication and(ii)the transfer film is easily formed during the friction process between the PTFE-containing solid film and the mold.(3)An oxide film with the thickness about 6 ?m can be obtained after anodizing on the surface of the 6061-T6 aluminum alloy sheet.The tribological test shows that the oxide film improves the surface hardness and wear resistance of the aluminum alloy sheet.The porous structure of the oxide film can store the lubricating oil and improve the physical adsorption of the oil medium.In addition,the complex effect of the base oil and its extreme additive can reduce the resistance of the friction surfaces.(4)Anodized aluminum alloy sheet has the poor stamping formability than original sheet.Appropriate BHF and lubrication conditions can improve the stamping performance and forming surface quality of the anodized aluminum alloy sheet.(5)Finite element simulation analysis shows that the friction coefficient of the contact surface between the sheet and the molds affects the maximum thinning rate,thickness distribution and forming quality of the formed part,and the influence rules are different. |
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