| 摘要 |
A method of working blanks of so-called hard aluminium of the special standard type USA 7075 T6, which is otherwise difficult to work by bending, hammering out, or the like. The relevant blank is heated briefly to the so-called loosening point, which is approximately 475 DEG C, this heating being controlled with high precision to a blank temperature in the interval 471-475 DEG C, whereafter - within 60 seconds - the blank is exposed to a shock chilling by abrupt immersion in cold water, preferably with a transition time of only few theths of a second. When through-cooled, the blank is lifted off the water and is then easily workable within the next 12 hours, preferably within 2-3 hours. The metal will then regain its rigidity, even to an increased degree due to the cold working, during the following few months, but this period may be shortened by heating the product, e.g. at 120 DEG C for 24 hours. At the cold working the blank can be worked almost as was it tin solder, e.g. with entirely sharp foldings or bends, without these giving rise to subsequent weakness in the product.
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