Argon welding of aluminum: what are the difficulties

The question of the most accessible methods of welding products from aluminum in pure form and its various alloys is quite relevant in connection with their wide application. Argon welding of aluminum is considered to be one of the most common technologies. Typically, welded deformable non-heat-strengthened aluminum alloys, which include technical aluminum (grades AD, AD1), alloys based on aluminum and manganese (AMZ), aluminum and magnesium (AMg). Such alloys, mainly, are difficult to weld. Therefore, they are used if heat treatment is possible for the structure.

Aluminum oxide forms a refractory film on the surface of the part (Tmol Al ₂ O ₃ = 2050 ° C), which has a higher density than the metal itself. When the oxide film is destroyed, its particles contaminate the welded bath, complicating the joint of the edges. Therefore, argon argon welding is preferred after mechanical removal of the oxide or etching of the base and filler metal. Additional complications are caused by a significant difference between the melting points of Al (Tm = 660 ° C) and its oxide.

When an argon welding of aluminum with a non-consumable electrode from tungsten is performed, alternating current is applied. In this case, the oxide film breaks down in half-periods of reverse polarity, when 70% of the arc's heat is released to the electrode and 30% to the product (cathode sputtering occurs).

The strength of the metal is sharply reduced at high temperatures, which can cause destruction of the unmelted part of the edges under the weight of the welded bath. Increased fluidity of the Al melt increases the likelihood of its flow from the root of the weld. To prevent burns and joint failures, if argon welding is performed, the technology can provide for the use of forming ceramic (graphite, steel) linings. This is done by welding a single-layer metal or the initial layers of a multi-pass weld.

The increased tendency of aluminum alloys to warpage can be overcome by welding at optimal temperature conditions and heating the connected parts. The appearance of the hydrogen porosity of the seam, which is particularly noticeable in alloys with magnesium, is reduced by heating to T = 150-250 ° C before and during welding, and by thoroughly cleaning the edges and welded wire. To avoid hot cracks, the seams should not be placed close to each other. It is also possible to add special improving modifiers to the metal.

Argon welding of aluminum involves the use of a protective gaseous medium from an inert gas of argon, which displaces the atmosphere air from a welded bath and plasma arc. Ar can be applied (higher or first grade). Another option is helium, a mixture of helium and argon, but then the shielding gas consumption is slightly increased.

The diameter of the non-melting tungsten electrode (except for pure, used lanthanized or yttrium) is selected depending on the thickness of the product. As a filler material is a welding wire of different brands, which depends on the composition of the main product and the thickness of the edges. Qualitative argon welding by one's own hands can be carried out on alternating current (UDG type installations) with observance of necessary regimes selected by an experienced welder. Beginners should first familiarize themselves with the literature sources, which indicate the modes and nuances of aluminum welding.