We continue to publish a review of equipment for foundry plant for pressing of aluminum profiles. Such workshops melted own technological scrap and produce ingots for pressing-pillars. This time it will be about the melting furnaces for such plants.
Melting furnace and mixer
There are several options for selection of stoves and their location, which depend on the total amount of the planned foundry production. With a capacity of up to 8000 tons of ingots a year poles may well be quite a furnace, in which all operations will be performed: melting, alloy preparation, Exposure and feeding the melt onto the casting machine.
If the production of ingots, columns exceeds 10000 tons per year, the, perhaps, it is better to use two ovens:
- melting furnace;
- holding furnace.
The mixer is finishing the chemical composition of the alloy, refining and subsequent casting. Such furnaces also referred to as handouts.
If an even higher capacity is required, three furnaces can be used:
- two melting furnaces;
- one mixer.
This configuration is suitable, if frequent changes of aluminum alloy required. It can promote the production of ingots to 60000 tons per year.
A furnace for melting and casting of aluminum may be a fixed or tiltable.
Stationary furnace has a low capital cost and simple construction. The molten metal flows from the furnace through a special opening - taphole, which is closed with a special refractory cone-shaped plug - a shutter (Figure 1).
Tilting furnace requires more capital vlolzheny, because in order, to pour out the melt, it is tilted using a hydraulic cylinder (figure 2).
The figure 3 represented by 15-tonne tilting furnace for melting and casting of aluminum.
The higher cost is justified tiltable melting furnace ease and accuracy of the molten metal in the casting, and higher safety for the foundry workers and foundry generally.
In case of problems, for example, with casting or ingot-pillars with the supply of electric energy, tiltable furnace easily returns to its original safety position. metal feed for casting stops, and the remaining molten metal remains in the furnace to troubleshoot.
In a similar situation with a stationary oven must manually close the tap hole furnace. It is difficult and dangerous, special, under emergency conditions. All this increases the risk, that the entire volume of the furnace may be in the casting pit or on the floor of the foundry.
Aluminum charge - all materials and components, are charged into a melting furnace to obtain the desired aluminum alloy.
Aluminum charge carefully selected, To make sure, that there are no unwanted elements or alloys, which would contaminate or alter the final product - a given aluminum alloy. This is achieved by careful control of the supply of aluminum scrap, as well as permanent control of the charge in the absence of foreign material, for example, steel strapping or cans, which may contain liquid.
If the aluminum scrap contained a certain amount of water, especially in closed containers, there is a great danger of explosions. Such explosions may have a threat to health and life of workers casters, as well as destroy the oven and other equipment. It must be ensured, that in the kiln aluminum scrap no liquids. Of particular danger are beverage cans and other metal containers.
To reduce the risk of load into the oven problem, for example, wet, scrap is recommended to dry it at the entrance to the furnace before, both immerse it in a bath of molten metal. Standing for 10-15 minutes is usually sufficient.
To the furnace aluminum scrap it is necessary to weigh, to prevent excessive loading of the furnace and the molten metal spilling, as well as to accurately calculate dopants. It is impossible to estimate the number of eyes on the loaded scrap, because its volume can vary considerably for different types of scrap.
Aluminum ingots typically loaded in whole bales. Typically they are placed with a forklift entering the furnace and then is confronted in a bath of molten metal. Scrap extruded profiles usually charged beams approximately 150 kg. Before loading into the furnace of all steel packaging tape must be removed, to prevent contamination of the molten iron.
To download an aluminum charge into the furnace using special devices and machines - Loaders. A simple loader for small capacity furnace 3500 kg is shown in Figure 4.
Semi-automatic loader for large furnaces with simultaneous loading 2000 kg of aluminum charge is shown in Figure 5. The figure 6 similar to the loader shown in.
Source: Materials from Ashford Engineering Services, 1997