Preventing porosity during aluminum welding

Porosity is one of the main defects encountered during aluminum welding. This phenomenon is caused by hydrogen being trapped in the metal's microstructure after cooling. The concentration of hydrogen, which is highly soluble in liquid aluminum, decreases rapidly during solidification, leading to the formation of voids or pockets of air, referred to as porosity defects. These defects can adversely affect essential properties such as mechanical strength and toughness of aluminum.

Sources of Hydrogen

The sources of hydrogen in welding primarily stem from moisture, contamination, and manufacturing conditions:

1.      Moisture

• Hydrated oxide layer on the metal surface
• Poor storage conditions for welding consumables
• Condensation in water-cooled welding torches
• Defective gas shielding hoses
• Low-purity shielding gas

2.      Contamination

• Presence of hydrocarbon substances (oils, greases, solvents) on the base or filler metal.

3.      Manufacturing Conditions and Welding Parameters

• Base metals from die casting are often more porous
• Inadequate welding parameters (distance, gas flow rate, etc.)

Prevention of Porosity

Preventing porosity requires a thorough diagnosis of hydrogen sources. Here are some corrective actions to implement:

1. Filler Metals

• Store in a dry environment (relative humidity < 35%).
• Keep in original packaging until use.
• Recondition coated electrodes that have absorbed moisture.

2. Tools and Cleaning

• Use clean tools dedicated to aluminum (stainless steel brushes).
• Check the seals on torches for leaks.
• Degrease solid filler rods with solvents such as acetone.

3. Welding Methods

• Preheat the base metal.
• Use high-frequency alternating current for TIG welding.
• Avoid turbulence in the molten pool.

To achieve porosity-free welds, it is crucial to control the sources of hydrogen, whether from moisture, contamination, or welding parameters. By applying these best practices, you will significantly improve the quality of your aluminum welds. To have even more information about the welding of aluminum we suggest you to read the following articles : Part 1 : Types of aluminum and their characteristics and Part 2 : Weldability of aluminum alloys.

To optimize the quality of your aluminum welds and minimize the risk of porosity, contact our experts today! They will guide you toward the best practices and solutions tailored to your industrial needs.