Macropore
Macro pores are visible gas inclusions in the weld metal, formed by escaping gases during solidification. They reduce the weld cross-section and act as mechanical notches.
Physico-chemical mechanism of action
Macropores form when gases like oxygen or hydrogen are not fully removed from the molten pool during welding and collapse into spheres upon cooling. These gas inclusions are large enough to be visible to the naked eye.
Metallurgical relevance & welding risks
Macropores reduce the effective cross-section of the weld and make it mechanically weaker. They can lead to cracks or deformation, especially under load. They also increase the risk of corrosion since water and air can penetrate through the pores.
Workshop practice & instructions
To minimize macropores, it's important to prepare the weld pool cleanly. Use deoxidizers like silicon or potassium hydroxide to remove oxygen from the melt. Make sure the weld is well covered and no air bubbles form. For heavily loaded applications, a finer weld or special filler material can help reduce the number of pores.