Research On Surface Defects And Annealing Process Of Aluminum Substrate For Aluminum Plastic Composite Panel By Direct Cast-Rolling Of Electrolytic Aluminum Liquid

Aluminum plastic composite panel widely used in curtain wall decoration and advertising signs, because of its good resistance to corrosion, fire prevention, moisture proof and processing properties. Aluminum substrate as an important part of the aluminum plastic composite panel, its quality has a direct effect on the service life of the aluminum plastic composite panel. The traditional production of aluminum substrate is hot-rolled metal ingot remelting and other multi-channel order process, but the production process cumbersome, inefficiency and wasting energy. In recent years, as cast-rolling technology advances, the increasing use of electrolytic aluminum liquid direct cast-rolling in aluminum substrate production with short casting production process is replacing the traditional method. Compared with the traditional method, the production of aluminum substrate by electrolytic aluminum liquid direct cast-rolling has several advantages:short casting production process, low production costs, high production efficiency, etc.However, the direct cast-rolling of electrolytic aluminum liquid still has some technical problems:the temperature of aluminum liquid is too high; the low rate of effective crystal nucleation. The faster cooling rate in cast-rolling causes composition segregation, coarse second phase and the grains. The coarse second phase particles and the grains will cause poor bending and series surface defects of the aluminum substrate. To solve the above problem, this paper systematic studies the cause of surface defects in the direct cast-rolling process of electrolyte aluminum liquid, and improves surface quality and bending properties by optimizing the annealing process.In this paper, polarization optical microscope, scanning electron microscopy and other analysis methods were used and the mechanical properties, the bending properties were also tested to study the cause of macular defects, black bars defects, color defects, and also to investigate the influence of annealing treatment on microstructure and properties of aluminum substrate.The results show that the macular defects mainly due to annealing process unreasonable and the physical and chemical properties of rolling oil does not meet the requirements. When the heating rate is2.5℃/min, the holding time is4h, the heating temperature is180℃, the macular pollution level is the least; when the base oil is saturated hydrocarbons(eicosane) or n-alkanes, the additives is low carbon chain saturated alcohols or esters, the additives addition is2%, the macular pollution level is the least.The black bars mainly due to the refining agent and the inclusions wrapped in the refining agent into the aluminum billet, causing aluminum billet surface roughness increases, adsorbs dirt and rolling oils; or foreign impurities were pressed into the strip surface in the rolling process, resulting the strip surface roughness increases, then the rough places adsorbed dirt and rolling oil, thus presented as black bars at the macro level.The color defects mainly due to composition segregation and coarse grains. When the homogenization annealing temperature is480℃, the holding time is4h, small and uniform second phase particles can be obtained, at the same time, composition segregation are completely eliminated.As the final annealing temperature increases, the amount of second phase particles precipitated in the aluminum substrate increases firstly and then decreases. At210℃the amount of second phase particles precipitated is the least, is142931mm-2; at310℃the amount of second phase particles precipitated is the most, is178514mm-2. As the final annealing holding time increases, the amount of second phase particles precipitated increases firstly and then decreases. At3h the amount of second phase particles precipitated is the most, is180248mm-2; at16h the amount of second phase particles precipitated is the least, is107576mm-2. The second phase particles are small and uniform, the tensile strength is135.6Mpa, the elongation is9.2%, bending properties is optimal when the final annealing temperature is270℃, the holding time is4h、can meet the requirements of users.