Gas Pocket
A gas pocket is a large, bubble-shaped volume in the weld metal that forms due to gas entrapment or reactions in the molten pool. It can lead to porosity and weak spots.
Physical-chemical mechanism of action
A gas pocket forms when massive amounts of gases (like oxygen or hydrocarbons) are generated in the weld zone. These gases often get trapped by reactions between the metal and the additives in the molten pool or by insufficient deoxidation.
Metallurgical relevance & risks in welding
Gas pockets lead to porosity in the weld, which affects the strength and toughness of the material. These pores can also cause cracks or make the material susceptible to corrosion. A high amount of gas pockets can also lead to poor weld penetration and reduce the mechanical performance of the joint.
Workshop practice & instructions for use
To avoid gas pockets, it is important to ensure good deoxidation of the metal before welding. This can be achieved by using deoxidizers. Also, the molten pool process should be designed to minimize gas generation. For hard-to-weld steels, it helps to use a slower cooling process to control gas evolution.