Some problems on sheets from semi-continuously cast slab for vessel (Part 2)

Abstract

In the industrial rolling process of Al sheet, the cold rolling process practically follows immediately to hot rolling process without intermediate annealing. In this case, the hot rolling conditions may have effects on the anisotropy of final annealing sheets.So, we examined, by eare tests, these. effects on the anisotropy of final annealing sheets made of a semi-continuously cast slab (S. C. C. S.) and a book-mold cast slab (B. M. C. S.), both cold rolled in one way and cross way.The results obtained are as follows:(1) The ear values of sheets of S. C. C. S. are not always higher than those of B. M. C. S. but can be made even lower by selecting the proper hot rolling temperature, and are more severely affected by hot rolling temprerature than those of B. M. C. S., in which these effects are almost negligible. (See Fig. 8, 9)(2) Although it has been generally considered that the cross rolling gives lower ear value than one way rolling, it seems to be not always so. (See Fig. 8, 9)(3) In this experiment, both slabs were treated by the same processes after hot rolling, therefore the difference in anisotropies of final sheets made of both slabs should indicate the effects of orientation of cast grains resulted from both casting methodes.(4) The temper of as-hot-rolled plate at 400°C coresponds to I/2 H. When it is annealed, it softens gradually up to 450°C, but in high temperature annealing 600-640°C it rather hardens. (See Fig. 4) Consequently, ears of final annealed sheets become higher at 0-90° directions until the intermediate annealing temperature reaches about 400°C, but when the temperature rises over 400°C, the height of ear becomes lower and then finally the direction changes to 45°. (See Fig. 15)(5) The effects of hot rolling as the antecedents on mechanical properties, can be removed by subsequent intermediate or final annealing, but the effects on ears can never be removed. (See Fig. 13, 14, 15)(6) The pattern appeared on the anodized surface of the sheets made of S. C. C. S. can not be industrially removed by hot or cold rolling and annealing. The only way to cover it is cladding process.