Porosity
Pore porosity is the presence of gas-filled voids in the weld metal, caused by inadequate gas shielding, moisture, or contaminants. They weaken the effective cross-section and act as notches.
Physical-Chemical Mechanism of Action
Pores form when gas bubbles are not adequately removed during welding. This can be caused by insufficient gas shielding, moisture, or contaminants. The pores grow during cooling and can form a network of voids.
Metallurgical Relevance & Welding Risks
Porosity weakens the weld metal by reducing the effective cross-section. This can lead to a reduction in mechanical properties such as strength and toughness. Furthermore, pores can act as notches that can lead to cracks or hot cracks. The service life of the weld is significantly shortened.
Workshop Practice & Instructions
To avoid porosity, effective gas shielding is essential. This can be achieved by using shielding gases like argon or helium and maintaining a dry environment. Moisture in the weld should be minimized by thoroughly drying the workpiece before welding. Also, all contaminants should be removed thoroughly before starting to weld. In severe cases, careful gas control and slow cooling can help reduce pore formation.