Aluminum charge is all the materials and components, including aluminium scrap, that are loaded into a melting furnace to produce a given aluminum alloy.
Control of aluminium scrap
The aluminum charge is carefully selected to ensure that it does not contain any undesirable alloys or elements that will contaminate or distort the final product, the given aluminum alloy. This is achieved by careful control of the supply of aluminum scrap, as well as constant monitoring of the charge for the absence of foreign materials, for example, steel packaging tapes or cans that may contain liquids.
No water at all
If aluminum scrap contains any amount of water, especially in closed containers, there is a high risk of explosions. Such explosions can pose a threat to the health and life of foundry workers, as well as destroy the furnace and other equipment. It is necessary to ensure that there are no liquids in the aluminum scrap loaded into the furnace. Drink cans and other metal containers are especially dangerous.
To reduce the risk of loading problematic, for example wet, scrap into the furnace, it is recommended to pre-dry it at the entrance to the furnace before immersing it in a bath of molten metal. Waiting for 10-15 minutes is usually sufficient.
Тo weigh the scrap
Aluminum scrap loaded into the furnace must be weighed to prevent excessive loading of the furnace and splashing out of liquid metal, as well as to accurately calculate alloying additives. It is impossible to estimate the amount of loaded scrap by eye, since its volume can vary significantly for different types of scrap.
No steel tape
Aluminum pigs are usually loaded in whole bundles. They are usually placed using a forklift at the entrance to the furnace and then pushed into a bath of molten metal. Scrap extruded profiles are usually loaded in bundles of approximately 150 kg. All steel packaging tapes must be removed before loading into the furnace to prevent iron contamination of the melt.
Melting furnace loaders
To load aluminum charge into the furnace, special devices and machines are used – loaders. A simple loader for a small 3500 kg oven is shown in Figure 1.
Figure 1 – Simple loader for a small 3500 kg melting furnace .
A semi-automatic loader for a large furnace with simultaneous loading of 2000 kg of aluminum charge is shown in Figure 2. In Figure 2 a similar loader is shown in operation.
Acceptance and storage of aluminium scrap
Preventing water explosions and other hazards is the most important task in the receiving and handling of scrap aluminum :
- Visual inspection of incoming scrap to determine if a load is especially wet.
- Storing scrap in a covered location is recommended.
- Policy for charging must be a FIFO (first in, first out).
- Shredding the baled scrap is strongly recomended to give undesired fluids a chance to drain away.
- Inspection of incoming scrap for removing other hazards.
- Training personnel to recognize hazards is an important part of a safety program.
- Visual inspection of aluminium scrap with a radiation detection station, since radioactive material is the hardest to spot and the most damaging if not caught.
- Magnetic separators can remove most of the ferrous material (and the rust) from incoming scrap.
1. Материалы фирмы Ashford Engineering Services, 1997
2. Aluminum recycling / Mark Schlesinger – 2007