Rolling: Continuous casting and rolling (strip casting)
Hot-mill trains are very capital intensive and have specific production characteristics. Strip casting offers an alternative. In this process, 2–30 mm thick strip is produced by pouring molten aluminium through a type of nozzle into the gap between the rolls of a two-high breakdown rolling stand. These rolls are water cooled on the inside and the molten metal solidifies just before it reaches the narrowest point. Thanks to the short cooling time, this produces a very fine-grained structure that is beneficial to subsequent rolling. The cast strip is then cold rolled to the required finished thickness, either immediately or after intermediate storage.
The difference between – and possibly the disadvantage of – sheet and foil made from strip produced by strip casting and cold rolled products made via the hot rolling route lies in process limitations placed on the alloys that can be used. Depending on the thickness of the cast strip, supersaturation of the alloying elements can also result in unusual material properties. As a rule, it is therefore not possible to use strip casting with age-hardenable wrought alloys or alloys containing more than 3% magnesium. As a result, the semi-finished rolled products produced can only be used at the lower end of the strength scale.