As the annealing temperature increases, the 45 ear rate decreases to zero, so increasing the annealing temperature is the most effective way to eliminate the 3003 aluminum plate ear. The optimal annealing temperature was obtained through production experiments. However, it is not necessary to conduct a full-line temperature test during production. It is only necessary to select several temperatures for testing within a key temperature range (ie, 350 ° C ~ 450 ° C). If the optimal annealing temperature cannot be found within this temperature range, the chemical composition of the alloy must be adjusted. Due to the different cold rolling processing rates, the optimal annealing temperature is also different for aluminum sheets with the same chemical composition, but this does not mean that different thicknesses Different annealing temperatures must be used for the aluminum sheets. Production practice has proved that as long as the ear rate of the aluminum plate is within the range of ±3%, it can meet the requirements of the deep drawing process. Therefore, the different annealing temperatures are only used when the difference in the cold rolling rate is large, and the difference in this temperature is actually large.
In actual production, the annealing temperature is not expected to be too high, and increasing the content of Si and reducing the content of Fe is an effective method to reduce the optimal annealing temperature. In order to stabilize the annealing process, it is necessary to control the ratio of Fe to Si in the range of 1.5 to 3 according to different alloys. Alloys containing Mn can take low values, and alloys containing pure aluminum or magnesium can take high values. The chemical composition of the alloy (especially Fe and Si) should not be easily changed once it is determined, otherwise it will affect the deep drawing performance of the 3003 aluminum sheet after annealing.
The hot rolling process of 3003 aluminum plate is completed above the recrystallization temperature, so hot rolling has the characteristics of rolling and dynamic recrystallization. The hot-rolled sheet basically has no lugs or a small ear-making rate. Regarding the influence of the heating system before hot rolling on the texture formed by subsequent cold rolling and annealing, it has been found in production practice that if the heating before hot rolling is insufficient, even if annealed at the optimum temperature after cold rolling, you will also get a higher 45 ear rate in the end. If the heating and holding time before hot rolling is properly extended, the ear rate of the aluminum plate after annealing will be greatly improved. The explanation for this phenomenon may be that the long heating time can ensure that the whole hot rolling process is in dynamic recrystallization from beginning to end, so that the hot rolled plate does not last. Excessive cold rolling texture remains, so it is necessary to control the finishing temperature of hot rolling to 300°C or higher.
In production practice, it is not seen that the coarse grain will have a significant impact on the deep drawing performance (ear rate, tensile strength, elongation) of the aluminum sheet. Even the 3003 aluminum sheet with the coarse grain size of grade 3 can be deep drawn. For aluminum products with a deep drawing coefficient less than 0.6, orange peel defects will be formed on the surface of aluminum products after deep drawing. In general industrial pure aluminum, even if the annealing temperature is as high as 500 °C, the phenomenon of grain aggregation and growth is not seen, and it is only possible when it reaches 540 °C. Therefore, under general production conditions, 1050, 1100 and other industrial pure aluminum sheets cannot have coarse-grained waste products. Unless other impurities are brought into the scrap aluminum by using the washing charge or recycled, for example, more than 0.1% Mn is brought in, which is enough to make the grains of the pure aluminum plate abnormally coarse.
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