Slag inclusion
Slag inclusions are nonmetallic residues in the weld metal that could not float to the surface during solidification. They can come from electrode coatings or fluxes.
Physical-Chemical Action Mechanism
Slag inclusions form when non-metallic substances such as oxygen, carbon, or other chemical additives enter the molten pool during welding and are not fully dissolved. These slags remain trapped in the weld metal and cannot rise to the surface during solidification.
Metallurgical Relevance & Welding Risks
Slag inclusions can cause various problems, such as porosity, grain coarsening, and reduced mechanical properties of the weld metal. They also result in poor surface quality and can lead to corrosion issues.
Workshop Practice & Instructions
To minimize slag inclusions, it is important to keep the welding environment clean and apply flux correctly. The electrode covering should be properly selected and used to prevent non-metallic substances. For severe slag inclusions, post-treatment such as polishing or chemical cleaning may be required.