Compensation of crack susceptibility by manganese
Manganese reacts with sulfur to form manganese sulfides, which prevent hot cracking. This lowers the crack susceptibility during welding.
Physico-chemical Mechanism of Action
Manganese combines with free sulfur in the molten pool to form stable manganese sulfides (such as MnS). This prevents sulfur from remaining as free atoms in the weld, which could cause hot cracking.
Metallurgical Relevance & Risks in Welding
Without manganese, free sulfur atoms can remain in the crystal lattice and cause hot cracks. Adding manganese minimizes this risk, significantly reducing crack susceptibility.
Workshop Practice & Instructions for Use
When welding joints with high sulfur content (e.g., steel with high carbon content), add manganese in the form of manganese slugs or droplets to the melt. A typical addition is 0.1 to 0.3% manganese. Ensure thorough mixing to achieve uniform distribution of manganese sulfide.