The question of the most accessible ways of welding products from pure aluminum and its various alloys is quite relevant due to their wide application. One of the most common technologies is argon welding of aluminum. Usually, deformable non-heat-hardened aluminum alloys are welded, which include technical aluminum (grades AD, AD1), alloys based on aluminum and manganese (AMts), aluminum and magnesium (AMg). Such alloys are predominantly 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 (Tmelt Al2O3=2050°C), having a higher density than at the metal itself. When the oxide film is destroyed, its particles contaminate the weld pool, complicating the connection of the edges. Therefore, argon welding of aluminum is preferable after mechanical removal of the oxide or etching of the base and filler metal. Additional difficulties are caused by a significant difference between the melting points of Al (Тmelt=660°С) and its oxide.
Whenargon welding of aluminum is performed with a non-consumable tungsten electrode, alternating current is used. In this case, the oxide film is destroyed in half-cycles of reverse polarity, when the electrode accounts for 70% of the heat of the arc, and the product - 30% (cathode sputtering occurs).
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 it flowing out of the weld root. To prevent burns and failures of the seam, if argon welding is performed, the technology may include the use of forming ceramic (graphite, steel) linings. This is done when welding a single-layer metal or the initial layers of a multi-pass weld.
The increased tendency of aluminum alloys to warp can be overcome by welding at optimal temperature conditions and warming up the parts to be joined. The occurrence of hydrogen porosity of the weld, which is 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 weld wire. To avoid hot cracks, the seams should not be located 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 gas environment of inert gas argon, which displaces airatmosphere from the weld pool and the plasma arc. Can be used Ar (highest or first grade). Another shielding option is helium, a mixture of helium and argon, but then the shielding gas consumption increases slightly.
The diameter of a non-consumable tungsten electrode (except for pure, lanthanum or yttrated electrodes are used) 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 (installations of the UDG type) in compliance with the necessary modes selected by an experienced welder. A beginner should first familiarize himself with the literary sources, which indicate the modes and nuances of aluminum welding.
