Carbide precipitation front
The carbide precipitation front is the region where carbides precipitate from the steel during welding. This front moves controllably through the crystal lattice.
Physical-Chemical Effect Mechanism
During welding, a supersaturated carbide equilibrium forms in the weld metal. On cooling, excess carbide condenses and forms a front that moves controllably through the crystal lattice.
Metallurgical Relevance & Risks in Welding
An uncontrolled or too-fast movement of the carbide precipitation front can lead to uneven hardness distribution, causing cracks and hot cracks in the steel. A too-slow front movement can result in coarser microstructure and lower toughness.
Workshop Practice & Guidelines
To ensure a controlled carbide precipitation front, carefully regulate the cooling steps. For high-carbide steels (e.g., HSS), the cooling time should be at least 10 seconds per cm of weld. Avoid rapid cooling methods like water spray, as they can cause uncontrolled front movement.