Oxygen segregation
Oxygen segregation is a local enrichment of oxygen in metals, leading to oxide inclusions and reducing toughness and fatigue strength.
Physical-Chemical Mechanism of Action
Oxygen segregation occurs when oxygen concentrates near metal crystals. This can be caused by chemical reactions or mechanical processes such as welding. The extra oxygen forms oxides with the metal, leading to inclusions.
Metallurgical Relevance & Risks in Welding
The oxides are less tough and fatigue-resistant than the unsegregated metal. This can significantly impair the mechanical properties of the material, especially if segregation occurs in critical areas like stress fields or hardened zones. Toughness drops, which can lead to cracks and failure.
Workshop Practice & Instructions
To avoid oxygen segregation, it is important to ensure a clean welding environment. Use deoxidizers like silicon or potassium fluoride in the molten pool. Make sure the weld cools properly to get a uniform grain structure. For highly stressed components, it is advisable to use special welding processes like TIG or MIG with shielded gas.