Cluster porosity
Chain porosity consists of linear pore systems caused by irregular gas formation or surface contamination. They lead to fracture points and reduce strength.
Physical-Chemical Mechanism of Action
Chain porosity occurs when gas (often oxygen or hydrogen) is not sufficiently expelled during the welding process. This can be caused by irregular processes or local surface contamination. The gas forms lines that run parallel to the weld.
Metallurgical Relevance & Welding Risks
Chain porosity is dangerous because it creates fracture points and greatly reduces weld strength. It can lead to hot cracks or stress cracks, especially under mechanical load. The presence of chain porosity can be detected by visual inspection or specialized NDT methods.
Workshop Practice & Action Instructions
To avoid chain porosity, it is crucial to ensure a clean surface before welding and to initiate an effective deoxidation process. Use high-quality shielding gases and pay attention to correct gas flow rate. In severe cases of chain porosity, post-treatment such as hardening or austenitizing may be required.