Gap Filling Capacity
Gap filling ability describes the capability of a filler metal to completely fill narrow gaps. It depends on viscosity, surface tension, and wettability.
Physical-chemical mechanism of action
The gap-filling ability of a solder results from its capacity to get into tight gaps and stay there. This is influenced by viscosity, which controls the flow of the solder. Surface tension ensures that the solder adheres to the gap walls, while wettability ensures it goes through the entire joint.
Metallurgical relevance & risks in welding
Good gap-filling ability is crucial for a sound weld. It prevents porosity and improves the mechanical properties of the joint. Too low a gap-filling ability can lead to incompletely filled gaps, pores, and weak points, which impairs the toughness and service life of the weld.
Workshop practice & instructions
To ensure good gap-filling, choose a solder with suitable viscosity for the material combination. Set the temperature of the solder and the weld so that the solder is fluid enough to fill the gaps, but not so fluid that it runs off too quickly and promotes porosity. For heavy materials or tight joints, a higher viscosity may be required.