Keyhole Porosity
Keyhole porosity results from the collapse of an unstable vapor capillary caused by excessive energy density during welding. The trapped shielding gas cannot escape in time, leaving voids in the structure.
Physical-Chemical Mechanism of Action
During welding, an unstable vapor capillary forms and collapses due to excessive energy density (e.g., too high voltage or too rapid cooling). The trapped shielding gas cannot escape in time and remains confined, leading to voids in the structure.
Metallurgical Relevance & Welding Risks
Keyhole porosity can create weak points in the weld that may crack under mechanical load. It reduces the strength and toughness of the material and can cause leaks or failure in service.
Workshop Practice & Action Instructions
To avoid keyhole porosity, control the energy density during welding. This can be achieved by optimal voltage setting and controlled cooling. High voltage or rapid cooling should be avoided. For heavy-duty applications, additional inspections and quality checks are advisable.