Activating Flux
A flux applied before TIG welding to increase penetration depth via Marangoni convection and stabilize the weld bead.
Physical-Chemical Mechanism of Action
An activating flux contains chemical additives that are activated in the molten phase. These additives reduce surface tension forces and promote homogeneous weld bead formation through Marangoni convection. The liquid in the weld pool moves according to the concentrations of the additives, leading to a more uniform distribution of the molten phase.
Metallurgical Relevance & Welding Risks
Proper application of an activating flux increases weld quality and stability by reducing porosity and minimizing distortion. However, too much or missing flux can cause uneven weld bead formation, which may lead to cracks and microstructural degradation. Additionally, incorrect additives can cause chemical reactions in the weld pool that damage the material.
Workshop Practice & Working Instructions
Before starting TIG welding, apply the flux to the weld joint. The amount and application method depend on the material and desired penetration depth. A template or special tool can be used to control the flux dosage. After welding, the weld bead should be thoroughly cleaned to ensure no residues remain in the microstructure.