Distributed porosity
Area porosity field: A widely found collection of pores in the weld, caused by gas release or wrong material choice. Reduces load-bearing capacity and can lead to cracks.
Physico-Chemical Mechanism of Action
An area porosity field forms by the occurrence of gases in the weld pool that are not completely expelled. These gas bubbles remain in the liquid melt and condense into pores upon cooling. Additionally, incompletely dissolved metal compounds or wrong materials can lead to a dense porosity field.
Metallurgical Relevance & Welding Risks
An area porosity field reduces the strength and toughness of the weld. It can lead to cracks and failure under mechanical load, especially when the material operates under high pressure or at high temperatures. Pores can also serve as entry paths for corrosive substances.
Workshop Practice & Work Instructions
To avoid an area porosity field, it is crucial to set the shielding gas atmosphere correctly and ensure that all metal compounds are fully dissolved. The selection of the right wire and suitable welding flux is also critical. For difficult-to-dissolve metals, an increased melting temperature or longer heat treatment may be required to minimize gas evolution.