Chain-Like Porosity
Linear gas porosity in weld metal, resulting from continuous gas release during solidification. Reduces fatigue strength.
Physical-Chemical Mechanism of Action
Gas porosity occurs due to continuous release of gases like carbon dioxide or hydrogen during cooling of the weld metal. These gases form chains or lines as they release slowly and continuously.
Metallurgical Relevance & Welding Risks
Chain-like gas porosity significantly reduces the dynamic fatigue strength of the component. This porosity can lead to cracks and deformation, especially under mechanical load. Additionally, it can make the weld metal susceptible to corrosion.
Shop Practice & Instructions
To avoid chain-like gas porosity, ensure careful preparation and controlled cooling of the weld metal. Use a stable welding current and appropriate shielding gas mixtures. Ensure the weld does not cool too fast (t8/5 > 25 s) to promote homogeneous cooling and avoid porosity.