Carbon Dioxide Shielding Gas
CO2 shielding gas is used in MAG welding of unalloyed steels to prevent deep penetration. It dissociates in the arc and leads to more spatter.
Physicochemical Mechanism of Action
CO2 shielding gas (CO2) is injected into the arc during MAG welding. There it dissociates into carbon and oxygen. The oxygen reacts with the iron and forms iron oxide, which prevents deep penetration.
Metallurgical Relevance & Risks in Welding
The use of CO2 shielding gas can cause deep penetration if the gas is not correctly metered. This can lead to incomplete weld fill and cracks in the material. Additionally, increased spatter raises stresses in the weld and can cause hot cracks or grain coarsening.
Shop Practice & Action Guidelines
Use CO2 shielding gas for MAG welding of unalloyed steels with a flow rate of 10-15 l/min. Make sure gas flow rate and welding current are correlated. Too high a flow rate can lead to deep penetration, while too low a rate results in incomplete fill and cracks.