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8 Methods and Skills of Aluminum Alloy Welding

1. Resistance welding

Aluminum alloy resistance butt welding (spot welding) can generally only be used for the lap welding of plates with a thickness of less than 5mm, or the lap welding of bars with a thickness of less than Φ10mm. The advantage is that the welding cost is low, the welding efficiency is high, and it is more convenient to integrate into the automatic production line. For example, it is widely used in automobile manufacturing. The limitation is that the thickness that can be welded is limited, and different electrodes need to be made for different products and structures.

2. Argon arc welding

Manual argon tungsten arc welding is mainly used for welding aluminum alloy sheet (thickness < 6mm) structure. Due to the protective effect of argon gas and the crushing effect of argon ions on the oxide film of aluminum alloy, argon arc welding can be used without welding powder, thus avoiding the corrosion of the joint by the residue after welding, so there is no need to clean up after argon arc welding. Can also be unlimited. In addition, the scouring of the welding area by the argon flow during welding can significantly cool the welded joint, thus improving the structure and performance of the joint and reducing the deformation of the weldment

3. Gas shielded welding

Gas-shielded welding aluminum alloy single-sided welding double-sided forming is generally more difficult to master. If there is a gap between the butt plates, it is easy to weld through, and it is not easy to control the back penetration of the weld without leaving a gap. The domestic welding of aluminum alloys is generally AC argon arc welding method, but for thicker plates, the efficiency of argon arc will be very low. At present, melting electrode pulse gas shielded aluminum alloy welding is only used in some examination items. Moreover, most of the welding of the butt plate is the overhead welding position, which is mainly used in the welding of the aluminum alloy car body and frame of the EMU.

4. Friction welding

The aluminum alloy friction stir welding seam is formed through plastic deformation and dynamic recrystallization, the grains in the weld area are refined, there is no fusion welding dendrite, the structure is fine, the heat affected zone is narrower than that of fusion welding, and there is no burning loss of alloying elements , cracks and pores and other defects, the overall performance is good. Compared with the traditional fusion welding method, it has no spatter, smoke, no need to add welding wire and shielding gas, and the joint performance is good. Because it is a solid-phase welding process, the heating temperature is low so that the welding deformation is small. The disadvantage is that the welding speed is slow and the process is not mature enough.

5. Gas welding

The thermal power of the oxygen-acetylene gas welding flame is low, and the heat is dispersed, so the deformation of the weldment is large and the productivity is low. When welding thicker aluminum weldments with gas welding, preheating is required. The weld metal after welding not only has coarse grains and loose structure, but also is prone to defects such as alumina inclusions, pores and cracks. This method is only used for welding repairs of unimportant aluminum structural parts and castings with a thickness ranging from 0.5 to 10 mm.

6. Laser welding

Aluminum alloy laser welding technology is a new technology developed in the past ten years. Compared with traditional welding technology, it has the characteristics of strong function, high reliability, no vacuum condition and high efficiency. It has the characteristics of high power density, low total heat input, large penetration depth with the same heat input, small heat-affected zone, small welding deformation, high speed, and easy industrial automation. The disadvantage is that the energy cannot be fully absorbed when welding aluminum alloys. Cause waste is big, and equipment purchase cost is high.

Seven, molten electrode argon arc welding

The arc power of automatic and semi-automatic metal argon arc welding is large, 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 argon tungsten arc welding. It can weld pure aluminum and aluminum alloy plates with a thickness of less than 50mm. For example, welding an aluminum plate with a thickness of 30 mm does not require preheating, and only two layers of front and back can be welded to obtain a weld with smooth surface and high quality. Semi-automatic melting electrode argon arc welding is suitable for positioning welds, intermittent short welds and weldments with irregular structural shapes. Semi-automatic argon arc welding torches can be used for welding conveniently and flexibly, but the diameter of semi-automatic welding wire is relatively small. The porosity sensitivity of the weld is greater.

8. Pulse argon arc welding

①, tungsten pulse argon arc welding

This method can significantly improve the stability of the low-current welding process, and it is convenient to control the arc power and weld shape by adjusting various process parameters. The weldment has small deformation and small heat-affected zone, which is especially suitable for thin plate, all-position welding and other occasions, as well as welding of forged aluminum, duralumin, super duralumin, etc. that are highly sensitive to heat.

②, melting electrode pulse argon arc welding

The average welding current that can be used is small, the parameter adjustment range is large, the deformation and heat-affected zone of the weldment are small, the productivity is high, the resistance to porosity and cracking is good, and it is suitable for all-position welding of aluminum alloy sheets with a thickness of 2-10 mm.

③, resistance spot welding, seam welding

It can be used to weld aluminum alloy sheets with a thickness below 4mm. For products with higher quality requirements, DC shock wave spot welding and seam welding can be used for welding. More complex equipment is required for welding, the welding current is large and the productivity is high, especially suitable for mass-produced parts and components.

④, friction stir welding

Friction stir welding is a solid-state joining technique that can be used for welding plates of various alloys. Compared with the traditional fusion welding method, friction stir welding has no spatter, no smoke, no need to add welding wire and shielding gas, and the joint has no pores and cracks. Compared with ordinary friction, it is not limited by shaft parts, and can weld straight seams. This welding method also has a series of other advantages, such as good mechanical properties of the joint, energy saving, no pollution, and low preparation requirements before welding. Due to the low melting point of aluminum and aluminum alloys, it is more suitable for friction stir welding.

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