Aluminum and its alloys are widely used in the field of industry due to their good corrosion resistance, electrical conductivity, thermal conductivity and high specific strength. They are second kinds of metal materials in the production of steel. In recent years, with more and more extensive application Aluminum Alloy in automobile, shipbuilding, aerospace, defense, entertainment and sports equipment manufacturing, technology development by leaps and bounds in the Aluminum Alloy welding, its performance can be classified into 3 aspects.
A new welding technology Aluminum Alloy and the improvement and innovation of the traditional welding technology based on, such as low frequency modulated pulse MIG welding, AC MIG welding, TIG welding, welding torch double keyhole plasma arc vertical weld;
Second, high aluminum and its alloys have been widely used in the industrial field because of its good corrosion resistance, electrical conductivity, thermal conductivity and high specific strength. It is the second kind of metal material in the production of iron and steel. In recent years, with more and more extensive application Aluminum Alloy in automobile, shipbuilding, aerospace, defense, entertainment and sports equipment manufacturing, technology development by leaps and bounds in the Aluminum Alloy welding, its performance can be classified into 3 aspects. A new welding technology Aluminum Alloy and the improvement and innovation of the traditional welding technology based on, such as low frequency modulated pulse MIG welding, AC MIG welding, TIG welding, welding torch double keyhole plasma arc welding in vertical position; second, high energy density welding technology in welding Aluminum Alloy further promotion and application fields, such as electron beam welding, laser welding and YAG welding; third, in Aluminum Alloy appeared in the field of friction stir welding.
Characteristics of aluminium alloy welding
Aluminum Alloy because of light weight, high strength, good corrosion resistance, no magnetism, good formability and good low temperature performance and is widely used in all kinds of welding structure of products, using Aluminum Alloy instead of steel welded structure can reduce the weight of more than 50%.
There are several difficulties in the welding of aluminum alloy:
(1) the welding joint of aluminum alloy is severely softened and the strength coefficient is low, which is the biggest obstacle to the application of aluminum alloy;
(2) on the surface of the alloy, it is easy to produce the refractory oxide film (the melting point of A12O3 is about 2060 DEG C);
(3) welding of aluminum alloy is easy to produce porosity;
(4) welding hot cracking of aluminum alloy;
(5) the coefficient of linear expansion is large and it is easy to produce welding deformation;
(6) the thermal conductivity of aluminum alloy is large (about 4 times that of steel), and at the same welding speed, the heat input is larger than that of the welded steel by a factor of 2 to 4 times.
Therefore, the welding of aluminum alloy requires high efficiency welding with high energy density, small heat input and high welding speed.
Laser welding technology of aluminium alloy

At present, the production of commonly used MIG welding, TIG welding method to weld aluminum alloy materials. Although these 2 methods can get good welding joints, the 2 methods have the disadvantages of poor penetration, large welding deformation and low production efficiency. In recent years, many scientists began to explore a new method of welding Aluminum Alloy, such as laser welding, dual beam laser welding, laser arc hybrid welding and friction stir welding, this paper briefly introduces the main features of the first 3 kinds of welding methods.

Laser welding of 1 aluminum alloy
With the development of high power and high performance laser processing equipment, the laser welding technology of aluminum alloy is developing rapidly, which is one of the main development directions of the future welding aluminum alloy. At present, the aluminum alloy laser welding has been used in the connection of the body parts, in the Audi A2 (all aluminum structure), there are 30m laser welding.
Compared with the traditional TIG, MIG welding, laser welding aluminum alloy has the following advantages:
(1) high energy density, small amount of heat input, small welding deformation, can melt zone and heat affected zone is narrow and deep penetration welding.
(2) the cooling speed is fast, and the microstructure of the welded joint can be obtained.
(3) the welding speed is quick, the function is many, the adaptability is strong, the reliability is high and does not need the vacuum device, therefore has the incomparable superiority in the welding precision, the efficiency, the automation and so on.
Laser welding is a kind of high energy density welding technology, welding aluminum alloy can effectively prevent the defects of traditional welding process, the strength coefficient is greatly improved. But the laser power is low, the Aluminum Alloy welding of thick plates, while Aluminum Alloy surface with laser beam absorption rate is very low, and there is a threshold to achieve deep penetration, so there is a certain degree of difficulty on the process.
Laser arc hybrid welding of 2 aluminum alloy
Although laser welding aluminum alloy has many advantages, but there are still a large number of limitations, such as high cost of equipment, joint clearance tolerance is small, the preparation process of the workpiece is strictly required. In order to weld aluminum alloy more effectively, laser arc hybrid welding technology has been developed. Laser arc hybrid is mainly composed of laser and TIG arc, MIG arc and plasma. At present, the technology of more research in developed countries such as Germany and Japan, and in the automotive industry has some application, such as the Volkswagen Phaeton on the front door there are 48 -MIG laser welding, laser welding and hybrid welding can also be used for the vehicle body and axle.  However, the domestic research and application of the process is basically blank.
Aluminum Alloy laser arc hybrid welding is a good solution to the laser power, welding Aluminum Alloy surface absorption rate of laser beam and the threshold value of deep penetration, is one of the most promising technology Aluminum Alloy welding, the current technology is not mature, at the stage of research and exploration.
When the laser and arc welding method is used to weld aluminum alloy, the influence of laser and arc can be overcome. It can significantly improve the welding efficiency, which is mainly based on 2 Effects: on the one hand, the high energy density leads to high welding speed; on the other hand, the superposition effect of 2 kinds of heat sources acting at the same time. This kind of composite technology has many advantages and great potential, and it will have a wide application prospect in the future.
Dual beam laser welding of 3 aluminum alloy
When the laser welding aluminum alloy alone, the pores will be produced due to the collapse of the keyhole. To solve this problem, people study the dual beam laser welding, dual beam laser welding seam has found a relatively wide weld width and low aspect ratio, can improve the stability of the keyhole, could significantly reduce the stomatal sensitivity. The reason is that the dual beam laser welding laser beam to produce the first molten pool, and preheating of the nearby area, cumulative heat to second laser irradiation area, can melt more base material, thereby forming a wider weld. In addition, due to the second laser beam to keyhole laser beam forming the first posterior gasification, to avoid the collapse of key hole, so the formation of pores will be little chance.