Slag Inclusion
Slag entrapment is the inclusion of solidified slag in the weld joint, caused by insufficient degassing or too high thermal conductivity of the weld metal. This leads to porosity and reduced mechanical properties.
Physical-Chemical Action Mechanism
Slag inclusions occur when slag is not fully released during the welding process. The slag solidifies and forms pores in the weld. This happens especially when gas removal is insufficient or when the weld metal has too high thermal conductivity, preventing gas release.
Metallurgical Relevance & Welding Risks
Slag inclusions lead to pores in the weld, significantly reducing mechanical properties like strength and toughness. The pores can also cause cracks or hot cracks, especially under load. Additionally, the material may no longer be optimally deformable.
Workshop Practice & Instructions
To avoid slag inclusions, careful gas removal is essential. Use a sufficiently powerful shielding gas and ensure the gas hose is not too tight or too long. For highly conductive materials like aluminum or alloys, thermal conductivity can be reduced by slightly cooling the weld metal or using a suitable filler gas. Always monitor gas removal and the process with a gas analyzer.