Sulfur Inclusion
Sulfide inclusions are manganese sulfides that form in the microstructure and reduce toughness in the through-thickness direction.
Physicochemical Mechanism of Action
Sulfur inclusions form from the reaction of sulfur dioxide with manganese in the molten pool. This reaction creates manganese sulfides, which are carried through the metal as heterogeneous inclusions.
Metallurgical Relevance & Welding Risks
The presence of sulfur inclusions reduces through-thickness toughness. This can lead to cracking and fracture under mechanical loading, especially at high stresses or temperatures near the melting point.
Workshop Practice & Action Instructions
To minimize sulfur inclusions, reduce the sulfur dioxide content in the weld pool. This can be achieved by careful selection of shielding gas and use of deoxidizers. A typical target for sulfur content in the melt is below 0.01 %.