Oxide Scale
Oxide layer: At high temperatures, a thin, scale-like layer forms on the metal surface due to oxygen. It protects the metal from further scaling.
Physical-Chemical Mechanism of Action
At high temperatures, the metal reacts with oxygen from the environment and forms a thin layer on its surface. This layer consists of oxidized metal compounds that prevent direct contact between the metal and oxygen.
Metallurgical Relevance & Risks in Welding
The oxide layer can have both positive and negative effects. Positively, it protects the metal from further scaling, which increases service life and strength. Negatively, it can cause problems, such as deterioration of the weld or formation of porosity, if not properly removed.
Workshop Practice & Instructions
Before welding, the oxide layer should be removed. This can be done by chemical cleaners or mechanical methods like grinding or polishing. The welding temperature and time should be selected so that a new, thin oxide layer forms after cooling, protecting the metal.