Transport of molten metal
For casting aluminium, the molten metal has to be transported within the smelter, for example from the pot to the foundry. Different types of technique have been developed for specific purposes:
- crucibles for transport via forklift, crane or cart
- slightly tilted "gravity" launders (channels along which the molten metal flows)
- mechanical pumps (whose parts that come into contact with the molten metal are made from a material such as silicon carbide)
- induction transfer launders for transporting, dosing and casting: the molten metal is transported via these launders (channels) using travelling magnetic fields, which are generated by built-in, current-carrying coils
- induction pumps (based on the same principle as the induction transfer launders)
Foundries are also supplied with molten metal from primary and secondary aluminium smelters. Such foundries save the costs of investments for melting plant, as well as energy (and thus avoid emissions). The deliveries are carried out in holding crucibles on low loaders. The temperature loss is only about 7-15 °C an hour, so that transport over distances of 200 kilometres and more is possible. In Germany, molten aluminium has been transported by road since 1972. The low loaders usually transport three crucibles at a time, each containing four tonnes of molten metal. The crucibles can be tilted and emptied using a casting spout. They are secured in such a way that no aluminium can escape in the event of an accident. Special safety measures are specified for the journey.