| Superior quality light gauge aluminum foil has become the mainstream of today’s market demand, it is also the common goal and direction for aluminum foil enterprises to seize the market and improve the effectiveness. To obtain the few number of pinhole and the yield of finished product of aluminum foil products, the quality of aluminum foil blank must be strictly controled. Joint purification of aluminum melt is the primary task and important subject for aluminum foil blank production; it also is the prerequisite and guarantee for the high quality light gauge aluminum foil production. At present, the light gauge aluminum foil is produced mainly by the casting and rolling method, the three key technologies of continuous cast-rolling are melt purification, alloy composition controlling and microstructure controlling of casting blank.The number of pinhole is one of the main measure indexes for the quality of the light gauge aluminum foil; the tendency of the aluminum foil pinhole number is mainly determined by the melt hydrogen content. For the production of ultra-thin aluminum foil, melt hydrogen content is kept as low as possible, the general requirements for the hydrogen content is less than0.14ml/100gAl. This article describes the pinhole status of the light gauge aluminum foil of the advanced domestic enterprises, The experiments has researched the affect situation for the1235alloy melt hydrogen content and the quality of the aluminum foil follow-up form the amount of refining gas and refining time, the using time of the filter plates, environment humidity, and the accurately controlling of the alloy composition and technology of grain refinement. The experimental results have the certain guiding significance to reduce the number of pinhole and improve the yield of finished product of ultra-thin aluminum foil.The results showed that blow the N2through ventilation bricks into the1235alloy melt, when the N2amount is80dm3/h, refining time is15min, the hydrogen content of the melt can be reduced to0.11ml/100gAl, the purification and dehydrogenation efficiency is the best, in this moment, to increasing N2amount has not much affect for improving the quality of ultra-thin aluminum foil. Twin-stage filter plates are mainly used to filter out the slag from aluminum alloy melt, it by means of the pores of the plates to absorb the small particles. The filtration efficiency of the same filter plate is different when it is used in different time due to blockage problems and so on. It is the most suitable for the production of ultra-thin aluminum foil by aluminum foil blanks are produced with the26to55tons molten aluminum filtered by40/50ppi twin-stage filter plates. Environmental humidity is one of the factors that affect the quality of ultra-thin aluminum foil too. The greater the ambient humidity, the higher the hydrogen content in the melt of1235aluminum, the more the pinhole number in ultra-thin aluminum foil. When produced good quality ultra-thin aluminum foil, the best choice for aluminum foil casting blank is ambient humidity below55%. When environmental humidity is above the65%so in the ultra-thin aluminum foil, the pinhole number is increased significantly and the yield of the ultra-thin aluminum foil is lower.The compounds composed in the aluminum foil blank are mainly decided by adding elements Fe, Si contents and the ratio of Fe/Si, By study the effect of different Fe/Si ratio for the quality of aluminum foil, It could draw that the alloy composition range is0.38%<Fe<0.40%,0.12%<Si<0.14%,2.75<Fe/Si<3.30, the pinhole number of ultra-thin aluminum foil is lower, and the yield of finished products is higher. The organization of aluminum foil blank in this alloy composition range is analyzed by transmission electron microscopy, and do not find the coarse second-phase compound that is not conducive to rolling.Before homogenizing annealing in630℃×7h, the amount of deformation of2.55mm thick aluminum blank sample, is about57%, due to the anisotropy of the deformation texture, both the blank longitudinal tensile strength and the elongation rate are higher than those of transverse after630℃×7h homogenizing annealing,, the longitudinal tensile strength get close to transverse tensile strength, and elongation rate can reach more than30%. This is consistent with the properties of annealed cube texture. The tracking of the to the finished aluminum foil production shows that the product rate of ultra-thin aluminum foil is the highest, and the number of pinholes is relatively low under630℃×7h homogenizing annealing.Before intermediate annealing by370℃×6h, the0.5mm thick aluminum blank sample with80%deformation, blank longitudinal tensile strength and elongation rate is also higher than the transverse tensile strength. This is induced by anisotropy produced by the same deformation texture as before. Aluminum blank sample intermediate annealed in370"Cx6h, which extension rate is of about45%. Heating speed in Intermediate annealing can ensure that products rate of aluminum foil is higher, and pinhole number relatively lower.Before the product annealing, the tensile strength of ultra-thin aluminum foil can reach152MPa, while the extension rate is of only0.4%-0.6%. After annealing treatment to the finished product in185℃×9h, the tensile strength decreased to67～80MPa,and the elongation also slightly increased to0.8%～1.4%.The blank of6mm thickness after roll casting, in which the grain size is mainly distributed in24～48μm. Roll casting process results that the blank has the textures of {110}<001> Gauss,{112}<111> copper type texture,{210}<367>texture, and {221}<012>texture. In which, Gauss texture and copper texture are typical deformation texture, but the strength is lower than{210}<367>texture and {221}<012> texture.The aluminum blank with6mm thickness is rolled into2.55mm sample after one pass rolling, The grain size is mainly distributed in20～28μm, and which mainly has the textures of{110}<001>Gauss texture,{112}<111> copper texture and {221}<012> texture. In those types, the deformation texture, such as{110}<001> Gauss texture and{112}<111> copper texture, which strength is far greater than that of casting sample, and individual area retains the cast rolling texture{221}<012> After the heat treatment of630℃×7h, the processing state samples with2.55mm thickness grain size are mainly distributed in27～44μm, and also, the texture of the samples after heat treatment is mainly annealing cube texture{001}<100>, but the Gauss texture remains in individual region.The annealed aluminum blank with2.55mm thickness can come into being samples with0.5mm thickness after3passes continuous rolling, and the grain size mainly distributed in8～16μm. In process of rolling deformation, samples generated the texture, which are mainly{112}<111> copper texture,{110}<001> Gauss texture, texture{110}<112> and{111}<123>. After intermediate annealing treatment of the blank with0.5mm thickness under370℃×6h, the grain size is mainly distributed in15-27μm, and the texture mainly is annealed cube texture{001}<100>. There also have the deformation texture, such as copper texture and Gauss texture in the structure.After a series of cold deformation,0.0045mm thick aluminum foil is eventually produced, and the grain size mainly distribute in15～30μm. Cube texture and Gauss texture mainly exist in the finished aluminum foil. Refined aluminum foil is stored for a period of time after foil rolling and roll, which formed a natural aging process.In the process of continuous casting and rolling, the molten aluminum is excessively quenched, and aluminum nanocrystalline region with the grain size of10-30nm come into being. Because some rolled nano-crystal region is stretched, and aluminum has a variety of orientation distribution, so apparent slip band is produced. Although the grain refiner of Ti and B is added, in continuous casting and rolling process, the second phase is not observed in the selected sample, which suggested that the Ti and B exist inside the grain. In this rolling process, the second phase Al3FeSi precipitated, and also, the second phase is stretched along rolling direction, and some distribute in linear or scattered punctuate form. Phase transition and phase reunion occurred in the630℃×7h annealing process, and the second reunion gathered into a sphere with the diameter of about800nm. The phase components are A13.2Fe (PDF#65-4770). The second phase formed by samples with0.5mm thickness is (Al,Fe,Si)(PDF#20-0030) after the process of370℃×6h intermediate annealing,, which component are close to A18Fe2Si. The conditions of two annealing are different, which results in the differences on phase composition and phase structure. |
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