Deoxidation slag
Deoxidation slag is a liquid layer of slag that absorbs oxygen and impurities from the weld pool. It protects the solidifying weld metal and promotes a clean weld.
Physicochemical Mechanism of Action
Deoxidation slag forms through chemical reactions between metals in the weld pool and oxygen. It consists mainly of silicon dioxide (SiO2) and other additives like sulfur dioxide (SO2). This slag floats to the surface of the weld pool and forms a dense layer that keeps oxygen away from the metal.
Metallurgical Relevance & Welding Risks
Deoxidation slag has a critical impact on weld quality. It prevents porosity, improves mechanical properties and protects the solidifying metal from corrosion. Without an effective slag layer, oxygen contamination and incomplete cooling can occur, leading to hot cracking and a coarse grain structure.
Workshop Practice & Instructions
To ensure good deoxidation slag, clean the metals thoroughly before welding. Watch the slag layer on the weld pool surface regularly and, if needed, strengthen it by adding deoxidizers like silicon or sulfur dioxide. A thin, smooth slag layer is ideal for a clean weld.