Weld Pool Surface Tension Gradient
The melt pool surface tension gradient describes the local change in tension on the pool surface due to temperature and concentration differences. It drives thermocapillary Marangoni convection, which affects penetration depth.
Physical-chemical mechanism of action
Surface tension in the melt pool changes with local temperatures and concentrations of gases like oxygen or water vapor. This tension difference creates a pressure gradient that drives fluid flow (thermocapillary Marangoni convection).
Metallurgical relevance & welding risks
An uneven tension gradient can cause distortion or porosity. This impairs the strength and mechanical properties of the weld. It can also lead to uneven cooling and thus microstructural changes, posing risks to toughness and load behavior.
Workshop practice & instructions
To ensure a homogeneous melt pool, control temperature and concentration distribution. Keep the melt pool dry and regulate oxygen concentration. For complex tasks, special tension compensation measures may be needed to stabilize penetration depth.