To produce secondary aluminum they use scrap. In modern conditions, this process is called Recycling, because in the process of production from one cycle, the metal passes into another cycle. Is impossible to produce primary aluminum from aluminum scrap, so if you need primary one, you should contact exclusively the manufacturers of primary aluminum. Some of the manufacturers who are involved in the production of recycled metal have learned how to produce better and more durable alloys. In the process of remelting in several stages and special processing of scrap, products of increased value are created that meet quality standards.
The reaction of aluminum and oxygen very often creates alumina. On the surface of a metal such as solid aluminum, as a result of the reaction, a film with anti-corrosion functions is formed, so any oxidation and defects are further excluded. The film becomes a reliable way to protect the product from metal destruction. In liquid form, an oxide-based film is also formed, but it is thermally affected. It leads to frequent oxidation of the material, which is highly undesirable in the production. Oxidation is more expressed in cases where aluminum in molten form covers plenty of surface. This process must necessarily be reduced, since oxidation leads to significant losses of material. In production, this task is perfectly handled with the help of special equipment.
In modern conditions, melting can be carried out in such a way to prevent strong oxidation of the material. For the manufacture of products from secondary aluminum, special furnaces are used. They allow you to immerse scrap in a previously prepared bath of liquid metal. There are also other types of furnace equipment, which are characterized by the melting of aluminum in isolation from contact with oxygen. If the scrap is contaminated and has many defects, then it is treated with a flux layer in rotary furnaces. This method not only guarantees effective protection against possible oxidation, but also separates the film from the liquid material, thereby cleaning it with high efficiency. Flux is far from the only way to clean the material: some experts use various additives and alloying components.
During production, significant losses of secondary aluminum are very frequent. Most of the problems in this regard are formed during the processing of metal in its liquid form, and other are associated with the low quality of scrap. Often, the amount of metal can be reduced during cleaning furnaces or during processing on special filtering equipment. Also, during the launch of the foundry equipment, insignificant losses are possible. Either way, any loss or waste that results from recycling can be re-processed.
For the competent and efficient production of secondary grade aluminum, scrap is used. As a result, secondary aluminum alloys are produced that are not inferior in quality to primary ones. At the same time, such types of scrap as beer cans and scrap can be used for development. However, the use of low-quality scrap leads to problems and loss of material as a result, therefore it is very important to ensure its sorting.
The requirements for the chemical composition of aluminum alloys are not always met, despite the correct processing of scrap in special furnaces. In this regard, special alloying type additives are introduced into the alloy. Components in the form of ligatures, alloys or pure metal are also used. Alloying is carried out using a special furnace, and the final processing requires filling equipment. In production, it is necessary to have not only a melting, but also a casting furnace.
In order to remove various defects and contaminants, as well as to eliminate the risk of oxidation in the aluminum furnace, special additives are used. They are also designed to grind grain when the need arises. In addition to the above processes, chlorine, nitrogen or other types of gases, including their mixtures, can often be used in melting furnaces during production. It is also necessary to improve the performance of the recycled aluminum.
Previously, the processing of aluminum was not very difficult. Only high-quality scrap was used, while it was melted a second time in the usual way. The secondary alloy obtained as a result of such processing fully satisfied the needs of the customers. Foundries have enjoyed the most demand for this option. In those days, difficulties in terms of electricity did not exist, but modern conditions changed the situation for the worse. Manufacturing processes are now much more complex. A modern customer requires a high-quality secondary aluminum alloy that meets the required criteria and chemical composition. Processing and alloying have become mandatory complex procedures that are required in modern conditions in production for various purposes.
The production of granules or ingots in accordance with GOST is most often carried out using secondary aluminum. This is due to the large space of possibilities for the mixtures that are included in the scrap. Granules and ingots are effective solutions for steel deoxidation. They are also used in other metallurgical industries. According to GOST 295-98, it is necessary to use secondary aluminum. This standard includes 3 types of AV alloys: 97, 91 and 87. Each digit indicates the amount of magnesium and aluminum in the composition.
The cleanest is AV97. Its magnesium content cannot exceed 0.1 percent. At the same time, the percentage of high-quality aluminum is at least 96.9 percent. In spite of this, this alloy may also contain iron (sometimes up to 2%). In this regard, it is not used in alloys according to GOST 4784-97 – these are types AD0 or AD1.
One of the best quality alloys is AV87. It contains the largest amount of various impurities (about 5 percent silicon, 0.3 percent lead, about 4 percent copper, up to 3.3 percent zinc and a small amount of tin). Of course, components such as manganese, nickel and iron can be observed in the composition (their amount may be different, but the total percentage cannot exceed 13).
In foundry alloys, a high content of various mixtures is allowed, which was mentioned above in the article. Iron is also possible. In the process of casting under pressure in the AK12 alloy there can be up to 1.5 percent iron, and in AK5M2 – about 3. Secondary aluminum can be used in casting alloys and is a popular solution.
Unlike cast alloys, in this case, the content of various mixtures is lower. Their production using secondary aluminum scrap is difficult. Often, primary or clean waste is diluted with recycled metal. However, the dilution process proceeds to the acceptable limits set by the customer or standards.