Slag inclusions can be caused by:

Slag inclusions in welds occur when molten slag or impurities become trapped in the weld metal. These inclusions can negatively affect the mechanical properties of the weld, leading to weaknesses or failures. The correct choice regarding the cause of slag inclusions is related to poor welding technique.

When a welder does not properly control the welding process—such as maintaining a consistent travel speed, using the right electrode angle, or not properly cleaning the surface before welding—it can lead to incomplete fusion or improper removal of slag during the welding process. This can result in the slag being trapped in the weld pool and becoming a part of the solidified weld.

In contrast, poor preheating techniques, using the wrong size tungsten, or over-aggressive interpass cleaning do not directly relate to the phenomenon of slag inclusions. Preheating is mainly involved in reducing thermal shock and preventing cracking, rather than affecting slag. The size of the tungsten in TIG welding pertains to arc stability and weld quality but is less likely to lead to inclusions, and interpass cleaning, when done properly, is meant to remove contaminants and can reduce the occurrence of inclusions. Thus, the focus on welding technique as the cause of slag inclusions highlights its critical role in ensuring