Welding Methods of Aluminum Alloys
There are many welding methods for aluminum alloys, and each method has different applications. In addition to traditional fusion welding, resistance welding, gas welding, some other welding such as plasma arc welding, electron beam welding and vacuum diffusion welding can also easily weld aluminum alloys.
The characteristics and application scopes of common welding methods for aluminum alloys are shown in Table 1. The welding type should be selected according to the grades of aluminum and aluminum alloys, the thickness of the weldment, the product structure, and the requirements for weldability.
Table 1 Characteristics and application ranges of common welding methods for aluminum alloys
The characteristics and application scopes of common welding methods for aluminum alloys are shown in Table 1. The welding type should be selected according to the grades of aluminum and aluminum alloys, the thickness of the weldment, the product structure, and the requirements for weldability.
Table 1 Characteristics and application ranges of common welding methods for aluminum alloys
| Welding types | Features | Scopes of applications |
| Gas welding | Low thermal power, great deformation of weldment, low productivity, being easy to produce slag inclusions, cracks and other defects | Butt welding and repair welding are used for thin plates for non-critical occasions. |
| Manual arc welding | Poor quality of joints | It is used for repair welding and general repair for aluminum castings |
| TIG welding | Dense welding metal, joints with high strength and good plasticity, high-quality joints | It is used widely and can weld the plate with a thickness between 1 and 20mm. |
| Tungsten pulsed argon | Stable welding processes, precise and adjustable heat input, small deformation of the weldment, and joints with good quality | It is used for thin plates, welding at all positions, assembly welding and high-strength aluminum alloys such as forged aluminum and hard aluminum with great heat sensitivity. |
| Molten electrode argon arc welding | High arc power and fast welding speeds | It is applied to welding thick parts, and the thickness can be up to 50mm. |
| Melting electrode pulse argon arc welding | Small welding deformation, good porosity and crack resistance, and wide adjustment of process parameters | It is used for welding thin plates or at all positions, and it is commonly used for workpieces with a thickness of 2 to 12mm. |
| Plasma arc welding |
Concentrated heat, fast welding speeds, small welding deformation and stress and complicated processes | It is applied to places where requirements for butt welding are higher than those of argon arc welding. |
| Vacuum electron beam | Great penetration, small heat-affected zones, small welding deformation and good mechanical properties of joints | It is used for welding the welding part with small sizes. |
| Laser welding | Small welding deformation and high productivity | It is applied to weldments that require precision welding. |
(1) Gas welding
The thermal power of the oxy-acetylene gas welding flame is low, and the heat is relatively dispersed. Therefore, the deformation of the weldment is great and the productivity is low. When thick aluminum weldments are welded by gas welding, preheating is required. The welding seam metal after welding not only has coarse grains and loose structure, but also is prone to defects such as alumina inclusions, gas holes and cracks. This method is only used for welding repair of unimportant aluminum structural parts and castings with a thickness ranging from 0.5 to 10 mm.
(2) TIG welding
This method is performed under the protection of argon gas, and the heat is relatively concentrated. The arc combustion is stable. The welding seam metal is dense. The strength and plasticity of the welded joint are great, which makes TIG welding widely used in the industry. TIG welding is a relatively complete welding method for aluminum alloys, but the TIG welding equipment is more complicated and should not be operated outdoors.
(3) Fusion argon arc welding
The arc power of automatic and semi-automatic fusion argon arc welding is great, and the heat is concentrated. The heat affected area is small, and the production efficiency can be increased by 2 to 3 times compared with manual tungsten electrode argon arc welding. Pure aluminum and aluminum alloy plates with a thickness of less than 50mm can be welded. For example, welding aluminum plates with a thickness of 30 mm does not require preheating. A smooth surface and high-quality welding seam can be obtained only by welding the front and back layers. Semi-automatic melting electrode argon arc welding is suitable for positioning welding seams, intermittent short welding seams and weldments with irregular structures. The semi-automatic argon arc welding torch can be used for convenient and flexible welding, but the diameter of the semi-automatic welding wire is relatively small. The porosity of the welding seam is more sensitive.
(4) Pulse argon arc welding
Tungsten pulse argon arc welding
This kind of welding can significantly improve the stability of the low-current welding processes, and it is convenient to control the arc power and formation of welding seam by adjusting various process parameters. The weldment has small deformation and small heat affected zones, and is especially suitable for thin plates, welding at all positions and other occasions, as well as the welding of forged aluminum, hard aluminum and super hard aluminum.
Melting electrode pulse argon arc welding
The applicable average welding current is small, and the parameter adjustment range is wide. The deformation and heat affected zone of the weldment are small. The productivity is high, and the porosity and crack resistance are good. It is suitable for welding aluminum alloy sheets with a thickness of 2 to 10 mm at all positions.
(5) Resistance spot welding or seam welding
It can be used to weld aluminum alloy sheets with a thickness of less than 4mm. For products with higher requirements, DC shock wave spot welding and seam welding machine welding can be used. Welding requires more complex equipment, high welding current and high productivity, and it is especially suitable for mass-produced parts.
(6) Friction stir welding
Friction stir welding is a solid-state joining technique that can be used for welding various alloy sheets. Compared with the traditional fusion welding, friction stir welding has no spatter, no smoke, no addition of welding wires and shielding gas, no pores and cracks in the joint. Compared with ordinary friction, it is not limited by shaft parts and can weld straight seams. This welding also has a series of other advantages, such as good mechanical properties of the joint, energy saving, no pollution, and low requirements for pre-welding preparation. Friction stir welding is more suitable due to the low melting point of aluminum and aluminum alloys.
