Aluminum scrap 

Why sort aluminum scrap?

 

Typically, the aluminum scrap is supplied to the plant for sorting of scrap metal in the composition of non-ferrous metals, which may comprise besides of aluminum and its alloys, such non-ferrous metal, as well as their alloys, like: tungsten. cobalt, magnesium,, copper, bronze, brass, Molybdenum, nickel, lead, lead, titanium and zinc.

Handbook of aluminium recycling /Ch. Schmitz – 2014

Aluminium recycling /M. Schlesinger – 2017

Cast and wrought aluminum scrap

Primary sorting non-ferrous scrap made by hand directly in the acceptance of scrap Party. It consists in dividing it into various metals and their alloys: aluminum and its alloys, copper and its alloys, etc.. d.

Aluminum scrap is usually a mixture of various aluminum alloys - wrought and cast. Wrought and cast alloys can be easily divided - sort - by hand in appearance of the products and details, from which they are made.

Sorting aluminum alloys

See. also Aluminum scrap: sorting of alloys

Sort by zinc and copper

However sorted wrought and casting alloys even differ greatly from each other in chemical composition. for instance, aluminum alloy 7029, from which a car bumper made, It contains a large amount of zinc, whereas aluminum alloy 2036, from which the lining is made of the vehicle body, It has a high content of copper.

Sort by silicon and copper

If the "dumb" melted mixture was cast and wrought alloys, we certainly obtain the "fusion" to the high silicon content. Often this is not a problem for the secondary casting alloys, but may be unacceptable for wrought alloys. The same aluminum casting alloys, which are used in cars, They can vary widely on the content of copper, that is desired is not in all aluminum alloys, as a deformable, and casting. for instance, popular with car makers casting alloys A356 and A380 are the average content of the silicon, respectively 7 and 8,5 %. On the other hand, average copper content in the alloy is about A380 3,5 %, A356 alloy and the copper content should be not more 0,1 %.

Sorting "airplane" aluminum alloys

Such alloys as the 7050 and 7075 It belongs to the same series of aluminum alloys. However, a slight difference in the chemical composition, for example, presence of zirconium in the alloy 7050, It provides them with different physical properties, they need to work. other, of the so-called "aircraft" Alloys, such as , 2014, 2024, 7055 and 7449, also require pre-sorting.

The minimum for zinc alloys 6061 and 6063

Aluminum alloys 6061 and 6063 (domestic AD33 and AD31) are perhaps the most popular in many industrial areas, especially in the construction and automotive. The main alloying elements in alloys 6061 and 6063 They are magnesium and silicon, and the maximum zinc content must be kept below 0,10 %, but better - even lower. Therefore, the charge for smelting these alloys must be carefully sorted: there must be absolutely no profiles or sheets of 7xxx series alloys in it., in which the zinc is the main alloying element.

Control of the content of lead and bismuth

Moreover, in the party of aluminum scrap of 6xxx alloys can be, for example, articles of such alloys, as 6262 and 6033. These alloys contain lead and bismuth additives to improve machining. If these items do not have any labeling, then visually distinguish them among other scrap impossible.

Sorting in magnesium content

Another important reason for the sorting of wrought and cast alloys in their "native" series, as well as the individual alloys, is a hidden increased the price of some alloys, which hides inside their chemical composition. for instance, alloys 2014 and 2024 They are similar, but with different content of magnesium. The difference of magnesium in a mixture of these alloys may be from 0,4 to 1,6 %. Some businessmen say, what, considering, the, that magnesium is lighter and more expensive than aluminum, to abortion 2024 It should be more expensive alloy 2014. On the large volumes it can be a decent amount.

Portable analyzers for sorting aluminum scrap

In recent 10 years X-ray fluorescence spectroscopy (XRF spectroscopy) (in English - XRF-spectroscopy) is the standard method for the rapid determination of the chemical composition of metals and alloys in many countries around the world. RF analyzers are used for sorting metals, and input control of the chemical composition of metals and alloys.

Input control of the chemical composition of metals and alloys is an essential element of the quality assurance system in various industrial enterprises. Such control is necessary for the control of conformity of incoming materials and coordinated technical requirements for, to avoid unwanted mixing of different materials.

Laser Spark Emission Spectroscopy (LIBS) is a fairly new technique, which demonstrates a good opportunity to analyze the chemical composition of metals and alloys. This method has distinct advantages in determining the content of so-called "light" chemical elements, such as, beryllium, lithium, magnesium,, aluminum and silicon.

Portable X-ray analyzer

X-ray analyzer sends to the metallic surface of the sample miniature X-ray, which causes the ionization of the inner shell of the atoms, which consists of metal. As a result, the metal emits photons, which are characteristic of the elements present in the metal. These trapped photons silicon sensor device. To determine the "heavy" metals, such as titanium and lead, the analyzer takes a few seconds, and analysis lasts for lighter metals from 10 to 60 seconds.

Portable Laser Analyzer

Laser spark emission spectroscopy - this option optical emission spectroscopy, wherein the laser emission is caused. laser analyzer It strikes the sample surface and laser pulse vaporizes a certain amount of material of the order of one-billionth of a gram, and generates plasma at a temperature schleyf 5000-20000 Kelvin gradwsov. The laser energy is not great, but it is focused in a microscopic point on the sample surface, to form a plasma. In this plasma substance, of which the sample, decomposes partially into atoms and ionized. These excited atoms and ions at his return to the lower orbit emits line, characteristic for each chemical element.

Almost all chemical elements, commonly found in metals, can be detected by laser-spark emission spectroscopy:

  • Sensitivity to alkali metals (lithium, and sodium t. and alkaline earth metals (beryllium, magnesium, etc.. is very high.
  • Sensitivity of transition metals is high. It belongs, including, for zinc, manganese, iron and copper. refractory metals, such as niobium, Molybdenum, tungsten or tantalum, difficult to define.
  • Sensitivity to carbon, phosphorus and sulfur is generally insufficient for the analysis of these elements, but this fact has implications for steel, rather than for aluminum alloys.

Selection analyzer for sorting aluminum alloys

It is believed, X-ray analyzer that gives more stable, repeatable and reproducible results, than laser analyzer. At the same time, Laser analyzer provides new possibilities in comparison with X-ray. for instance, it can detect lithium in aluminum alloys, which are used in aerospace engineering. Moreover, the sensitivity of the laser analyzer of magnesium and aluminum is much higher, than that of the X-ray. Therefore, it can sort aluminum alloys much faster, than the X-ray - for a few seconds, compared with 30-60 seconds for the X-ray analyzer.

For aluminum alloys quicksort, which consist mainly of "light" chemical elements, laser is the preferred choice analyzer. For the separation of various aluminum alloys in the mixed aluminum scrap on some chemical element - copper, zinc or silicon - important not to exact its content, and its order - a lot or a little.

It is necessary to take into account the fact, that permits the point of view, the use of X-ray analyzer requires registration of many securities and licensing, as well as the usual long training safe handling of X-ray equipment. In laser analyzer is nothing of the kind.

Source: John I.H. Patterson, Ph.D., Portable Analytical Technologies LLC, 2015