Isolated gas pores
Individual gas pores are spherical air bubbles that form during cooling of the weld metal and reduce the load-bearing cross-section.
Physicochemical mechanism of action
Gas bubble porosity occurs when air penetrates the molten weld metal. This air gets trapped and forms spherical cavities during cooling.
Metallurgical relevance & risks when welding
Gas bubble porosity reduces the load-bearing cross-section, which leads to a decrease in strength. They can also serve as starting points for cracks and make the material more susceptible. Furthermore, they impair the weld appearance and the mechanical properties of the overall weld metal.
Workshop practice & instructions
To minimize gas bubble porosity, it is important to ensure a clean welding environment. Use a strong deoxidizer like silicon and make sure the shielding gas atmosphere is correct. Make sure the weld metal is properly cleaned before welding and the cooling is controlled.