Abstract: The aluminum alloy welding several advanced processes: friction stir welding, laser welding, laser - arc hybrid welding, electron beam welding. Poor weldability and had thought that the alloy can not be welded proposed effective solution, several processes have advantages, and welding of thick Welding Alloys.
Keywords: aluminum; friction stir welding; laser welding; laser - arc hybrid welding; electron beam welding

Aluminum alloy welding characteristics

Aluminum light weight, high strength, good corrosion resistance, non-magnetic, good formability and good low temperature performance is widely used in a variety of welding structural products, the use of aluminum alloy instead of steel plate material welding, structural weight reduce by more than 50%.

Aluminum welding several major difficulty: â‘      Aluminium Welding Rodsjoints soften serious, low intensity coefficient, which is the biggest obstacle to hinder aluminum applications; â‘¡ aluminum surface is easy to produce refractory oxide film (Al2O3 The melting point of 2060 ° C) This requires the use of high power density welding process; prone to porosity (3) aluminum alloy welding; easy to produce hot cracking â‘£ aluminum welding; ⑤ linear expansion coefficient, easy to produce welding deformation; â‘¥ aluminum alloy thermal conductivity (about steel 4-fold), under the same welding speed, the heat input than the welded steel 2 to 4 times.

Therefore, the welding of aluminum alloys require the use of the energy density, the welding heat input is small, the welding speed is high efficient welding method.

2 advanced aluminum alloy welding process

Aluminum alloy welding difficult in recent years to propose several new techniques, certain applications in transportation, aerospace, aviation and other industries, and several new techniques can be a good solution to the difficulty of aluminum alloy welding, welding joint performance and poor weldability or non-welded aluminum alloy welding.

2.1 aluminum alloy friction stir welding

Friction stir welding FSW (Friction Stir Welding) was proposed in 1991 by the British Welding Institute TWI (The Welding Institute) new solid plastic connection process [2]. Figure 1 shows the friction stir welding schematic diagram [3]. Its working principle is inserted into the workpiece to be welded, using a special form of mixing head by friction stir mixing head between the high-speed rotation and the workpiece, friction heat is generated so that the parts of the metal is in a thermoplastic state, and in the mixing head under pressure from The rearward portion of its front end the plastic flow, thereby the weldment pressure welded together. Figure 2 shows the friction stir welding process [4]. Due to stirring friction welding process does not exist in the melting of the metal, is a solid connection process, it does not exist in the welding welding a variety of defects, non-ferrous materials can be welded by welding methods are difficult to weld, such as aluminum and high strength aluminum alloy , copper alloys, titanium alloys and dissimilar materials, composite materials welding etc.. Friction stir welding more aspects of research applications in the welding of aluminum alloys. Has been successfully carried out the friction stir welding of aluminum alloy 2000 series (Al-Cu), 5000 series (Al - Mg), 6000 series (Al - Mg - Si), 7000 series (Al - Zn), 8000 series (Al - Li). Abroad already. Enter the industrial production stage, the technology, the U.S. aerospace company Lockheed Martin in Norway have applied this technology welding speedboat length of 20 m structural parts welded aluminum alloy storage of liquid oxygen the cryogenic vessels rocket structural parts.