Contaminants such as moisture, oil, paint, and mill scale will flash into gasses and can become trapped in the solidifying weld pool. Shielding Gas Problems
Shielding gas or flux protects the weld pool from reacting with the atmosphere. However, porosity can be caused by the shielding gas being improperly applied or the flux being contaminated with moisture.
When too little shielding gas is used, the liquid metal reacts with the atmosphere trapping gasses, such as oxygen and nitrogen, within the weld pool and forming porosity.
Conversely, too much shielding gas flow pressure can also be a problem. When the gas flow rate is too high, it creates turbulence in the shielding area, pulling the atmosphere into it and resulting in porosity. Mechanical Problems
Trouble with the welding equipment can affect the weld bead, with the most common issues being:
- Spatter-filled MIG liners interfering with the shielding gas
- Shielding gas contaminated by the supplier
- Cracked MIG liners, worn O-rings, or loose fittings allowing outside air into the shielding gas delivery system
Improper welding methods
can cause porosity in the bead, and some of these include:
- Stopping a TIG bead too quickly and suddenly removing the shielding gas may cause a crater at the end of the bead.
- An extreme angle of a TIG torch or MIG stinger could prevent the shielding gas from surrounding the weld pool.
- Moving faster than the available shielding gas could also expose the puddle
MIG welding is a popular welding technique that uses a wire as the electrode and an inert gas as the shielding gas. When using MIG welding, it is important to select the correct welding wire based on the type of material being welded.
One common mistake in MIG welding is using the wrong type of welding wire. Using a wire that is not suited for the material being welded can result in poor weld quality and porosity.
To avoid porosity in MIG welding, it is important to ensure that the welding wire is clean and free from rust or other contaminants. Contaminated welding wire can lead to inconsistent welds and reduced strength.
Overall, MIG welding can be a highly effective welding technique when performed correctly, with proper selection of welding wire and careful attention to shielding gas and welding parameters.