The question of the most affordable methods for welding pure aluminum products and its various alloys is quite relevant in connection with their wide application. One of the common technologies is argon welding of aluminum. Usually welded deformable non-heat-strengthened aluminum alloys, which include industrial aluminum (grades AD, AD1), alloys based on aluminum and manganese (AMts), aluminum and magnesium (AMg). Such alloys mainly relate to difficult to weld. Therefore, they are used if heat treatment is possible for the construction.
Alumina forms a refractory film on the surface of the part (Tm Al
2 O
3 = 2050 ° C), which has a higher density than that of the metal itself. When the oxide film is destroyed, its particles contaminate the weld pool, making it difficult to connect the edges. Therefore, argon
welding of aluminum is preferable after mechanical removal of the oxide or etching of the base and filler metal. An additional difficulty is caused by the significant difference between the melting points of Al (mp = 660 ° C) and its oxide.
When performing argon welding of aluminum with a non-consumable tungsten electrode, alternating current is applied. In this case, the oxide film is destroyed in half-periods of reverse polarity, when the electrode accounts for 70% of the heat of the arc and 30% (cathodic sputtering).
The strength of the metal decreases sharply at high temperatures, which can cause the destruction of the unmelted part of the edges under the weight of the weld pool. The increased fluidity of the Al melt increases the likelihood of its leakage from the root of the
weld. To prevent burns and weld failures, if argon welding is performed, the technology may include 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 seam.
The increased tendency of aluminum alloys to warping can be overcome by welding at optimal temperature conditions and warming up the connected parts. The appearance of hydrogen porosity of the weld, especially noticeable in alloys with magnesium, is reduced by heating to T = 150-250 ° C before and during welding, as well as by thorough cleaning of the edges and welded wire. To avoid hot cracks, the seams should not be placed close to each other. It is also allowed 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 atmospheric air from the weld pool and plasma arc. Can be applied Ar (premium or first grade). Another protection option is helium, a mixture of helium and argon, but then the flow of protective gas increases slightly.
The diameter of the non-consumable tungsten electrode (except pure, apply lanthanum or yttrium) is selected depending on the thickness of the product. Welding wire of various grades acts as a filler material, which depends on the composition of the main product and the thickness of the edges. Do-it-yourself high-quality argon welding can be carried out on alternating current (UDG-type installations) in compliance with the necessary conditions selected by an experienced welder. A beginner should first familiarize themselves with literary sources, which indicate the modes and nuances of aluminum welding.