Research On The Cause Of Coarse Grain Layer And Cold-rolling Process Of Cast 1235/8079 Aluminum Foil Blank

Double-zero aluminum foil has the characteristics of light weight,non-toxic and non-tasteless,and anti-ultraviolet.It is widely used in the packaging field,such as the packaging of milk boxes and cigarette cases.Casting method is the most common method for producing double-zero aluminum foil blanks.It has the characteristics of short process flow,high production efficiency,low equipment investment,energy saving and consumption reduction.In the production process of casting and rolling,the average grain size of rolling section is 110?m,which is the normal cast-rolled plate,but abnormally coarse-grained cast-rolled sheets sometimes occur.The average grain size of rolling section was 180?m.The coarse grain layer appears on the upper layer of the cast-rolled sheet,which seriously affects the microstructure and properties of the 0.24mm finished aluminum foil blank,and directly affects the pinhole rate of the double-zero aluminum foil at the later stage.This paper studies the causes of coarse grain layers in abnormally coarse-grained cast strips and the improvement measures.In view of the unavoidable coarse-grained cast-rolled sheet,the cold-rolling process suitable for the coarse-grained cast-rolled sheet is obtained through the study of the cold-rolling process,so that the coarse-grained cast-rolled sheet can also produce a qualified 0.24mm finished aluminum foil blank.In this paper,Inductively Coupled Plasma(ICP),Optical Microscope(OM),Scanning Electron Microscope(SEM),universal tensile testing machine,cupping test machine were used to measure the Ti content of the thickness gradient of the casting plate,observe the grains and the second phase of Size and condition,scan the cast plate morphology and elemental analysis,measure the mechanical properties of cast rolled plates and cold rolled plates,and plastic forming properties of 0.24 mm aluminum foil blanks.The above analysis method was used to study the cause of the coarse grain layer of the double-zero aluminum foil blank and the cold rolling process of the abnormally coarse grain cast steel plate.The result is as follows:The content of refining agent in abnormally coarse grain cast-rolled plates is uneven low,the underlayer of the abnormally coarse grain cast sheet detected many undissolved refiner agglomerates.The general conclusion is that the coarse grain layer appears on the top layer of the abnormally coarse grain cast-rolled sheet,because the refining agent is unstable in structure,the refining agent is unevenly distributed in the abnormally coarse-grained cast-rolled sheet,the refining agent is failed to be fully dissolved and form effective Nucleation particles.The addition method of refiners changed from single-filament and single-entry to double-filament and double-entry.The addition rate slowed down and the refiner dissolved more completely.After adding the position,not only did the refiner have sufficient incubation time,but also It is close to the optimum action time of the refiner in the casting and rolling.After refinement agent quality,the addition of methods and locations have been improved,refinement results have improved significantly.The 7.0mm thick cast rolled sheet was cold-rolled into a 4.1mm thick cold rolled sheet and then subjected to homogenization annealing.During the homogenization annealing(550°C,20h).When the 4.1mm thick cold-rolled sheet is not annealed,the average grain width of the coarse-grained cold-rolled sheet is 19?m,and the average grain size of the fine-grained cold-rolled sheet is 13?m;after the homogenization annealing,the average grain width of the coarse-grained annealed sheet is 57?m,and the average grain size of the fine-grained annealed sheet is 55?m;the final average grain size also tends to be close.Due to the hereditary nature of the cold rolling process,the grain size of the 0.24 mm thick aluminum foil blank is also close(The grain width is about 8?m).After the homogenized annealing having be used to 4.1mm cold-rolled sheet,the rod-shaped?-(AlFeSi)structure appears in the center layer of the cast-rolled sheet.The size and distribution of the second phase in the finished aluminum foil blanks produced by the abnormally coarse grain cast-rolled sheets after the increase in the amount of press-down is close to the second phase size and distribution in the finished aluminum foil blanks produced by the normal fine-grained cast-rolled sheet after the normal cold-rolling process.they are about 2?m disc-like particles,and the rod-like?-(AlFeSi)second phase structure disappeared.In the finished billet of abnormally coarse grain cast-rolled sheet produced by the normal cold rolling process,the rod-like?-(AlFeSi)secondary phase structure still exists,but the size(6?m)becomes smaller,accounting for about 20%.After the process of abnormally coarse-grained grain casting and rolling plate is improved,the mechanical properties and plastic forming properties of the finished aluminum foil blank are similar to those of the finished aluminum foil blank produced by the normal cold-rolling process,and the tensile strength,elongation,and cupping point are comparable.The bursts differ by about 2%.After the abnormally coarse grain cast-rolled plate is improved by the cold-rolling process,the finished aluminum foil blank is superior to the coarse-grained cast-rolled steel plate in production of the finished aluminum foil blank after the normal cold-rolling process,the tensile strength is basically unchanged,but the elongation rate is improved.16.1%(horizontal),14.7%(Longitudinal),14.5%(45~o direction),plastic forming performance increased by 10.9%.