Aluminum Welding and Important Considerations

Aluminum is the third most abundant element in nature, after oxygen and silicon. Although pure aluminum is a relatively soft metal, its strength can increase from 49 MPa to 700 MPa when alloyed. A small piece of aluminum oxidizes rapidly in an oxygen-rich environment. It is corrosion-resistant because its pH value ranges from 4 to 9. This oxide layer protects the aluminum from further oxidation but can cause difficulties in weldability.

Compared to Steel

• Physical Properties: Density 2.7 g/cm³ (steel 7.85 g/cm³)
• Melting Point: 660°C (aluminum oxide 2050°C, steel approximately 1500°C)
• Thermal Conductivity: 2.2 W/cm·K (steel: 0.8858 W/cm·K)
• Electrical Conductivity: 35 S·m/min² (steel: 10 S·m/min²)
• Hydrogen Solubility: 0.05 cm³ in solid aluminum (8 cm³ in steel)

With advantages such as low density, high corrosion resistance, and good conductivity, aluminum is widely used in the following sectors:

• Automotive technology
• Ship and rail vehicle manufacturing
• Aviation
• Tank construction
• Construction
• Packaging industry
• Electrical Engineering

Aluminum Alloys

• Forged Aluminum Alloys:
  • Non-age-hardening alloys: For example, AW-1050A (Al 99.5), AW-5005 (AlMg1), AW-5019 (AlMg5), AW-5083 (AlMg4.5Mn0.7)
  • Age-hardenable alloys: For example, AW-6005A (AlSiMg(A)), AW-6060 (AlMgSi), AW-6082 (AlSi1MgMn), AW-7020 (AlZn4.5Mg1)
• Aluminum Casting Alloys: AlSi and AlSiMg alloys may contain between 5% and 20% Si.

Welding of Aluminum Alloys

Aluminum can primarily be welded using TIG and MIG welding methods. Electrode welding is less commonly used today. It is important to follow specific rules when welding aluminum. First, the weld joint must be properly prepared, and the surface must be thoroughly cleaned. This helps prevent the negative effects of an oxide layer that may form on the aluminum surface at the start of welding.

Due to aluminum’s high thermal conductivity, preheating may be performed on thick and long pieces to prevent problems such as lack of penetration and porosity. To address the preheating issue in aluminum MIG welding, argon gas mixed with 30% helium can be used. Helium reduces porosity in the weld zone, increases penetration, and widens the weld bead; however, it may cause some instability in the welding arc.

Aluminum MIG pulse welding is preferred at low currents and in situations where the risk of warping or distortion is high.

Non-age-hardening wrought aluminum alloys can be welded with aluminum welding wires of similar composition, such as Al99.5 and AlMg. For age-hardenable alloys, AlMg4.5Mn or AlMg4.5MnZr welding wires may be preferred. The properties of the heat-affected zone (HAZ) in age-hardenable aluminum alloys may differ from those in other areas. Aluminum casting alloys, on the other hand, can be welded using AlSi welding wires with similar compositions.