Fundamental Study On The Technology Of Preparing Aluminum Foil By Quenching With Inner Concaved Belt

Preparing aluminum foil by quenching with inner concaved belt is the technologythat molten aluminum ejected on the moving loading belt spreads while moving alongwith the belt, in which process it quickly cools and solidifies into aluminum foil. As theloading belt is concave inwards, the molten aluminum ejected on it clings to the beltunder the influence of centrifugal force and then turns to continuous aluminum foil.Besides, aluminum foil in different thicknesses could be prepared by controlling suchparameters as the initial temperature of molten aluminum, the belt speed, the ejectingflow of molten aluminum, etc.Temperature field is the primary factor affecting the quality of the aluminum foilprepared by quenching with inner concaved belt. This research analyses the cooling andsolidification process with analytic solution, numerical solution and the ProCASTsimulation software. Temperature field formulas at three stages are obtained withanalytic solution, numerical analysis of the solidification stage is conducted withexplicit difference equation so as to better describe the influence exerted by the latentheat of solidification on temperature field, and curves indicating the changingtemperature field of different positions on the aluminum foil and the loading belt inthickness direction is also obtained by applying the ProCAST simulation software. Allthese three methods could well prove that the duration is less than0.031s from themolten aluminum’s contact with the loading belt to the end of its solidification. Whenthe equipment is in operation, molten aluminum covers a distance of over800mmduring its ejection and contact with the loading belt, cooling and solidification into foil,and disengagement from the belt by press roll. As a result, molten aluminum could stillspread and solidify into aluminum foil despite the high belt speed of25m/s, whichdemonstrates the feasibility of molten aluminum’s solidification into foil. With theProCAST software, simulations are conducted of molten aluminum’s ejection whenthere are different jet widths and jet velocities and analysis indicates that the length ofthe ejected molten aluminum is even and steady within35mm if the jet width is1~3mmand the jet velocity0.10m/s~0.40m/s. Simulation of molten aluminum’s flow andspreading with the hydro-mechanical analysis software Flow-3D shows that continuousaluminum foil could be prepared when the molten aluminum’s initial temperature is 700℃~800℃and the belt speed2.5m/s~7m/s.In this research, pure aluminum foil in certain continuous length and of goodsurface quality is successfully prepared by quenching with inner concaved beltequipment. Different initial temperatures of molten aluminum and belt speeds affect thesurface quality and the thickness of aluminum foil. By analyzing the process parametersof the low-quality aluminum foil, defects of the equipment are found and correspondingimprovement measures put forward. Test and analysis of the aluminum foil’smicrostructure and hardness shows that the aluminum foil grains are in zonal andlong-strip distribution in thickness direction and the size of which is less than7μm.According to the relationship between N (nucleation rate), G (growth speed), andΔ T(undercooling), the molten aluminum’s cooling rate and undercoling increases while itsinitial temperature rises, which leads to the increase ofZ V(the number of the grains perunit volume), grain refinement and the microhardness increases. When the belt speedincreases, the grain size decreases and the microhardness increases. Based on analysis,the reasonable process parameters of preparing aluminum foil by quenching with innerconcaved belt are as follows: the initial temperature of molten aluminum is700℃~800℃, the belt speed3m/s~6m/s, and the jet pressure0.06MPa~0.1MPa.