Pure aluminum has a low melting point

The low melting point of pure aluminum allows good machinability and counteracts the recycling of old material. It should be noted, however, that many common types of alloys increase the melting point. An outer oxide layer created by anodizing has a melting point that is more than three times higher.

Melting points of alloying partners

The melting point of pure aluminum is 660 degrees Celsius, making it one of the lowest of all metals. However, since aluminum is present in almost all cases as an alloy when used as a workpiece or component, the melting point increases according to the proportion of alloying partners involved. The natural oxidation to alumina leads to a melting point of the outer skin of 2052 degrees.

Melting points of the typical alloying partners are:

metalMelting point in degrees / centigrade
zinc419
magnesium639
copper1083
manganese1245
silicon1410
titanium1668

Other working and processing concerns mainly the oxide layer, which is controlled by anodizing. In the artificial oxidation of aluminum, an external melting point of the workpiece or component of about 2000 degrees is desired.

Sealing oxide layers

Typical anodization and sealing are chrome plating and gold plating of aluminum. In order to create a brass surface, a copper sputtering of the aluminum with different zinc content is made. In some alloys, especially in the field of sanitary components, vanadium is also used.

metalMelting point in degrees / centigrade
gold1064
Brass920-1065
chrome1857
vanadium1890

Oxidation prevents liquefaction

In order to process aluminum and successfully carry out a smelting process, the high degree of oxidation of the soft metal must be taken into account. When aluminum is to be liquefied, it is hardly possible to simply heat it in the air. When the melting point is reached, the aluminum is soft as kneadable rubber, but the oxidation "overtakes" the temperature of the aluminum and prevents it from becoming liquid.

Anyone wishing to re-pour pure aluminum, apart from any oxide layers that may be present, must carry out the heating in an oxygen-free working chamber. Both for heating and for welding aluminum, so-called protective gases are required. The noble gases argon, helium and mixtures of both are used for this purpose.

Eight alloy groups

Important for the estimation of the melting point of an aluminum alloy are the classifications of a kind in a designation system for wrought alloys. In eight groups the changes in the properties of the aluminum with the different alloying partners and in the pure state are recorded.

Further scaling includes workpieces in the range of cast aluminum, which is mainly used in the field of kitchen tools. The most common alloy is formed with silicon and melts at about 570 degrees.

Tips & Tricks

If you want to weld aluminum, you must first determine the alloy type. Unhardened alloys can not be welded.

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