Manganese sulfide stringers
Manganese sulfide stringers are deformed, stringy inclusions of manganese sulfide that cause anisotropic mechanical properties and reduce transverse toughness.
Physicochemical Mechanism of Action
Manganese sulfide stringers form when steels cool in an environment with free oxygen. The manganese sulfide forms at the edges and faces of weld grains and deforms into stringer structures during cooling.
Metallurgical Relevance & Welding Risks
These stringers cause uneven mechanical properties in different directions (anisotropy), which significantly lowers the transverse toughness of the weld. This can lead to cracks and distortion, especially under loads in directions other than the welding direction.
Workshop Practice & Action Guidelines
To minimize manganese sulfide stringers, it is important to cool the weld as quickly as possible. This can be achieved with a high cooling rate, e.g., by using cooling water or air flow directly on the weld. An optimal cooling curve is crucial to prevent the formation of manganese sulfide stringers.