Remelting and casting of aluminium
The metal in many of the aluminium objects around us has been remelted several times. Today, aluminium which has already served a useful life as one product will, after having been recycled, remelted and recast, reappear in a new prduct, perhaps in the form of a modern car engine.
The process of remelting requires expert knowledge of how aluminium with differing history – primary as well as secondary metals – can be converted into new alloys for hot rolling or extrusion, or directly into the final shape. The remelting and casting of aluminium alloys present a number of technical questions:
- How can the material losses during remelting be minimized?
- Which types of lining material for melting furnaces give the longest lifetime?
- How is the best precision obtained with regard to the addition of alloying elements?
- What methods are available for cleaning the melts?
- How should the casting process be carried out to obtain the required structure?
- Must the billet be heat treated and, if so, in what way, to secure the desired properties of the end product?
Sapa Technology can answer these questions. We work with Sapa's remelt plants and casting shops, and can contribute to solutions to the problems that may arise in melting and casting operations – all to make sure customers will have an alloy that is suitable for their end product.
In order to understand the properties of a material and how they are affected by composition and production processes, knowledge of the "building blocks" from which they are made up is necessary – all the way from the atomic level and upwards.
That an alloy should have the right composition is an obvious necessity, but this in itself is not the whole answer. The precipitation structure and grain structure must also be controlled to obtain a material with the required properties. The alloying elements can exist as separate particles of various sizes and as atoms evenly distributed amid the aluminium atoms. The way an alloying element behaves in a material and its influence on the properties of a material depends on:
- type of alloying element
- concentration of alloying elements
- combinations of different alloying elements
- production processes such as casting, heat treatment and deformation
To study the structure we use microscopes of various types. Our optical microscopes can magnify up to 2,000 times, and our scanning electron microscope up to 100,000 times, while still achieving the great depth of focus necessary in studies of rough surfaces or fractures. Learn more about: