Aluminum is a lightweight, corrosion-resistant, and highly conductive metal material widely used in aviation, automotive, construction, electronics, and other fields. However, the welding of aluminum is not as easy as steel, and it requires mastering some special methods and techniques to ensure welding quality and efficiency. This article will introduce you to the relevant knowledge of aluminum welding from four aspects: principles, methods, methods, and equipment.

1. The principle of aluminum welding

The principle of aluminum welding is to use an arc or other heat source to melt aluminum or aluminum alloy materials, and under a certain pressure and protective gas, make them penetrate and fuse with the base metal or filler metal to achieve connection. However, there are also some difficulties and problems in aluminum welding, mainly including the following points:

Both aluminum and aluminum alloys have a dense oxide film on their surface, which has a melting point several hundred degrees higher than the base material and is highly inert and not easily damaged. If the oxide film is not removed, it will affect the stability of the arc and the formation of the molten pool, leading to weld defects.

Aluminum and aluminum alloys have high thermal conductivity, about four times that of steel, which means they require greater heat input to reach the melting temperature, and heat quickly dissipates, resulting in a larger heat affected zone and greater deformation.

Aluminum and aluminum alloys have very small volume shrinkage during solid-liquid phase transformation, which is about one tenth of that of steel. This can lead to an increase in surface tension of the molten pool, making it difficult to flow and diffuse, and easily producing defects such as pores and slag inclusions.

Aluminum and aluminum alloys undergo precipitation hardening during the solidification process, where some alloy elements precipitate from the solid solution, forming fine dispersed phases, increasing the strength and hardness of the material. However, if precipitation hardening is uneven or excessive, it will reduce the plasticity and toughness of the material, affecting the mechanical properties of the weld.

Therefore, aluminum welding requires the use of special methods and techniques, such as removing oxide films, using protective gases, selecting suitable filler metals, controlling heat input and cooling rate, etc.

2. Welding methods for aluminum materials

According to different heat sources, aluminum welding can be divided into the following common methods:

Arc welding: Using an arc to generate high temperatures to melt the base material and filler metal. Arc welding can also be divided into AC arc welding, DC arc welding, pulse arc welding, etc. Arc welding is the most common aluminum welding method, which has advantages such as high efficiency, good quality, and wide applicability. However, it also has disadvantages such as high equipment cost, high operational requirements, and certain environmental impacts.

Gas welding: Using a mixture of gas and air or oxygen to produce a high-temperature flame to melt the base metal and filler metal. Gas welding can also be divided into acetylene welding, propane welding, hydrogen welding, etc. Gas welding is a relatively traditional aluminum welding method, which has advantages such as simple equipment, flexible operation, and low cost. However, it also has disadvantages such as low efficiency, unstable quality, and easy defects.

Laser welding: Using a laser beam to generate a high energy density heat source to melt the base material and filler metal. Laser welding can be divided into continuous laser welding, pulse laser welding, etc. Laser welding is a relatively advanced aluminum welding method, which has advantages such as fast speed, high accuracy, small deformation, and large aspect ratio. However, it also has disadvantages such as high equipment cost, high requirements for material surface quality, and high environmental conditions.

Ultrasonic welding: Using ultrasonic waves to generate high-frequency vibrations to solid-phase connect the base metal and filler metal under a certain pressure. Ultrasonic welding can also be divided into ultrasonic metal welding, ultrasonic plastic welding, etc. Ultrasonic welding is a relatively special aluminum welding method, which has advantages such as low temperature, high efficiency, energy conservation and environmental protection. However, it also has disadvantages such as complex equipment, high requirements for joint shape and size, and high requirements for operator skills.

3. Welding method of aluminum materials

According to the differences in electrodes and filler metals, there are several commonly used aluminum welding methods in electric arc welding:

Manual arc welding: Using a coated filler metal rod as the electrode, it is melted under the action of the arc and fused with the base metal. Manual arc welding is the simplest method of arc welding, which is suitable for the connection of aluminum or aluminum alloys with a thickness of less than 3mm, and is commonly used for repair and repair work. The advantages of manual arc welding are simple equipment, flexible operation, and low cost, while the disadvantages are unstable quality, low efficiency, and susceptibility to defects.

Argon arc welding: Using inert gas (such as argon) as a protective gas, an arc is generated between a non consumable metal electrode (such as tungsten electrode) and the base metal, and the connection is achieved by feeding the filler metal wire. Argon arc welding is the most commonly used arc welding method, which is suitable for the connection of aluminum or aluminum alloys of various thicknesses and shapes, and is commonly used in production and manufacturing work. The advantages of argon arc welding are the ability to remove oxide film, protect the molten pool, improve quality and efficiency, while the disadvantages are high skill requirements for operators and high environmental conditions.

Submerged arc welding: Using granular or powdered flux as a protective layer and consumable metal wire as an electrode, an arc is generated between it and the base metal, and the connection is achieved by feeding the filler metal wire. Submerged arc welding is a relatively special arc welding method, which is suitable for the connection of aluminum or aluminum alloys with a thickness of over 3mm. It is commonly used for the welding of large structures and thick plates. The advantages of submerged arc welding are that it can prevent defects such as pores and slag inclusions, improve mechanical performance and corrosion resistance, but the disadvantages are complex equipment, inconvenient operation, and easy generation of a large amount of smoke and dust.

4. Equipment for aluminum welding

Aluminum welding requires the selection of appropriate welding machine types to ensure welding quality and efficiency. Generally speaking, the following types of welding machines are suitable for aluminum welding:

AC arc welding machine: Using an AC power source to generate an arc, it can automatically remove the oxide film, improve arc stability and penetration. AC arc welding machines are suitable for manual arc welding and argon arc welding, and are commonly used for connecting aluminum or aluminum alloys with a thickness of less than 6mm. The advantages of AC arc welding machines are simple equipment, low cost, and strong adaptability, while the disadvantages are high arc noise and easy generation of alternating stress.

DC arc welding machine: Using a DC power source to generate an arc can improve heat input and melt pool control. DC arc welding machines are suitable for argon arc welding and submerged arc welding, and are commonly used for connecting aluminum or aluminum alloys with a thickness of over 6mm. The advantages of DC arc welding machine are stable arc, large melting depth, and small deformation, while the disadvantages are high equipment cost and inability to remove oxide film.

Pulse arc welding machine: Using a pulse power supply to generate an arc, it can control the temperature and shape of the molten pool, reduce the heat affected zone and deformation. Pulse arc welding machines are suitable for argon arc welding and are commonly used for connecting aluminum or aluminum alloys with a thickness of less than 3mm. The advantages of pulse arc welding machines are high quality, high efficiency, energy conservation and environmental protection, while the disadvantages are high equipment cost and high operational difficulty.

Gas welding machine: Using a mixture of gas and air or oxygen to generate a flame, it can melt the base metal and filler metal. Gas welding machines are suitable for gas welding and are commonly used for connecting aluminum or aluminum alloys with a thickness of less than 3mm. The advantages of gas welding machines are simple equipment, flexible operation, and low cost, while the disadvantages are low efficiency, unstable quality, and susceptibility to defects.

Laser welding machine: Using a laser to generate a laser beam, it can melt the base material and filler metal. Laser welding machines are suitable for laser welding and are commonly used for connecting aluminum or aluminum alloys with a thickness of less than 3mm. The advantages of laser welding machines are fast speed, high accuracy, small deformation, and large aspect ratio. The disadvantages are high equipment cost, high requirements for material surface quality, and high requirements for environmental conditions.

Ultrasonic welding machine: Use an ultrasonic generator to generate ultrasonic waves, which can cause solid phase connection between the base material and the filler metal under a certain pressure. Ultrasonic welding machines are suitable for ultrasonic welding and are commonly used for connecting aluminum or aluminum alloys with a thickness of less than 1mm. The advantages of ultrasonic welding machines are low temperature, high efficiency, energy conservation and environmental protection, while the disadvantages are complex equipment, high requirements for joint shape and size, and high requirements for operator skills.

5. Precautions for aluminum welding

In addition to mastering the correct methods and methods, aluminum welding should also pay attention to the following aspects:

Cleaning of aluminum: The surface of aluminum is prone to forming an oxide film, which can affect the quality and strength of welding. Therefore, before welding, tools such as brushes, sandpaper, solvents, etc. should be used to clean the oxide film, oil stains, dust, and other impurities on the surface of the aluminum material.

Preheating of aluminum: Aluminum has high thermal conductivity, which can cause rapid heat loss during welding, resulting in uneven or insufficient welds. Therefore, before welding, it is necessary to use tools such as flames or electric heaters to preheat the aluminum material appropriately to increase its temperature and plasticity.

Cooling of aluminum: Aluminum has a high degree of shrinkage, which can lead to stress and deformation after welding. Therefore, after welding, it is necessary to use tools such as natural cooling or water cooling to properly cool the aluminum material to eliminate its stress and deformation.

Inspection of aluminum materials: The welding seams of aluminum materials are not easy to observe with the naked eye and require professional testing instruments to ensure that they are free from defects, cracks, pores, oxidation, and other issues. If any problems are found, they should be repaired or replaced in a timely manner.

6. Summary

Aluminum welding is a process of connecting aluminum or aluminum alloy materials, which requires mastering some special methods and techniques. This article introduces the relevant knowledge of aluminum welding from four aspects: principles, methods, methods, and equipment. I hope this article can be helpful to you.