Microscopic linear porosity
Microscopic pore chains are fine gas inclusions along the solidification front in the weld metal that weaken the load-bearing capacity and come from local moisture in the filler material.
Physical-Chemical Mechanism of Action
Microscopic pore chains form through the spreading of gases like oxygen or hydrogen in the weld zone. These gases can form during the welding process or diffuse from the surrounding medium. They accumulate at interfaces and solidification fronts where temperature varies greatly.
Metallurgical Relevance & Risks in Welding
These pore chains weaken the mechanical load-bearing capacity of the weld because they serve as paths for stresses and loads. They can lead to cracks or deformations, especially under high pressure or at temperatures near the metal's solidification point. They also increase the risk of corrosion.
Workshop Practice & Action Instructions
To minimize microscopic pore chains, it is important to keep the weld metal dry and clean before welding. Use careful deoxidation and protect the weld from moisture during the process. Pay attention to correct welding parameters, such as temperature and time, to achieve a homogeneous structure. For heavily stressed applications, post-weld heat treatment like austenitizing or tempering can be helpful.